0001564590-22-008055 | 10-K | XBRL Viewer

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Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 345,209	$ 338,426
Marketable securities	112,230	137,314
Accounts receivable (net of allowance of $7,678 as of December 31, 2020)	32,439	42,999
Prepaid expenses	18,752	10,505
Other current assets	10,196	1,953
Total current assets	518,826	531,197
Marketable securities	391,907	46,809
Accounts receivable (net of allowance of $3,758 as of December 31, 2021)	2,262	3,267
Property and equipment, net	131,547	56,467
Operating lease right-of-use assets	60,904	63,815
Restricted cash	2,030	1,330
Other assets	6,428	5,279
Total assets	1,113,904	708,164
Current liabilities
Accounts payable	11,387	10,622
Accrued expenses and other current liabilities	76,111	49,082
Deferred revenue	3,333	449
Operating lease liabilities	1,752	2,500
Liability related to sale of future royalties	37,889	18,794
Total current liabilities	130,472	81,447
Deferred revenue		3,783
Operating lease liabilities	84,929	70,153
Liability related to sale of future royalties	133,460	174,504
Other liabilities	745	524
Total liabilities	349,606	330,411
Commitments and contingencies (Note 8)
Stockholders’ equity
Preferred stock; $0.0001 par value; 10,000 shares authorized, no shares issued and outstanding at December 31, 2021 and 2020
Common stock; $0.0001 par value; 100,000 shares authorized at December 31, 2021 and 2020; 42,831 and 37,476 shares issued and outstanding at December 31, 2021 and 2020, respectively	4	4
Additional paid-in capital	928,095	667,181
Accumulated other comprehensive loss	(2,569)	(360)
Accumulated deficit	(161,232)	(289,072)
Total stockholders’ equity	764,298	377,753
Total liabilities and stockholders’ equity	$ 1,113,904	$ 708,164

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Accounts receivable, allowance for credit loss, current	$ 3,758	$ 7,678
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	42,831,000	37,476,000
Common stock, shares outstanding	42,831,000	37,476,000

Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues
Revenues	$ 470,347	$ 154,567	$ 35,233
Operating Expenses
Cost of revenues	51,833	35,714	8,241
Research and development	181,437	166,294	124,185
General and administrative	79,333	63,817	51,815
Credit losses (recoveries) and other	(2,236)	7,975	(10)
Total operating expenses	310,367	273,800	184,231
Income (loss) from operations	159,980	(119,233)	(148,998)
Other Income (Expense)
Interest income from licensing	719	4,271	2,951
Investment income	6,825	9,723	48,559
Interest expense	(26,277)	(771)
Total other income (expense)	(18,733)	13,223	51,510
Income (loss) before income taxes	141,247	(106,010)	(97,488)
Income Tax Benefit (Expense)	(13,407)	(5,240)	2,755
Net income (loss)	127,840	(111,250)	(94,733)
Other Comprehensive Income (Loss)
Unrealized gain (loss) on available-for-sale securities, net	(2,209)	(565)	885
Total other comprehensive income (loss)	(2,209)	(565)	885
Comprehensive income (loss)	$ 125,631	$ (111,815)	$ (93,848)
Net income (loss) per share:
Basic	$ 3.01	$ (2.98)	$ (2.58)
Diluted	$ 2.91	$ (2.98)	$ (2.58)
Weighted-average common shares outstanding:
Basic	42,438	37,281	36,690
Diluted	43,913	37,281	36,690
License and royalty [Member]
Revenues
Revenues	$ 470,347	$ 154,567	$ 35,233

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional paid in capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Balances at Dec. 31, 2018	$ 508,848	$ 4	$ 592,580	$ (720)	$ (83,016)
Balances (Shares) at Dec. 31, 2018		36,120
Adoption of ASU 2016-02 (Topic 842) \| ASU 2016-02 [Member]	(33)				(33)
Adoption of ASU 2016-02 (Topic 842) \| ASU 2018-02 [Member]				40	(40)
Vesting of restricted stock units, Shares		40
Exercise of stock options	7,062		7,062
Exercise of stock options, Shares		796
Issuance of common stock under employee stock purchase plan	1,314		1,314
Issuance of common stock under employee stock purchase plan, shares		36
Stock-based compensation expense	26,854		26,854
Unrealized gain (loss) on available-for-sale securities, net	885			885
Net income (loss)	(94,733)				(94,733)
Balances at Dec. 31, 2019	450,197	$ 4	627,810	205	(177,822)
Balances (Shares) at Dec. 31, 2019		36,992
Exercise of stock options	5,623		5,623
Exercise of stock options, Shares		428
Issuance of common stock under employee stock purchase plan	1,799		1,799
Issuance of common stock under employee stock purchase plan, shares		55
Stock-based compensation expense	31,949		31,949
Unrealized gain (loss) on available-for-sale securities, net	(565)			(565)
Net income (loss)	(111,250)				(111,250)
Balances at Dec. 31, 2020	377,753	$ 4	667,181	(360)	(289,072)
Balances (Shares) at Dec. 31, 2020		37,476
Issuance of common stock upon public offering, net of transaction costs	216,059		216,059
Issuance of stock, net of transaction costs		4,899
Exercise of stock options	4,279		4,279
Exercise of stock options, Shares		403
Issuance of common stock under employee stock purchase plan	1,768		1,768
Issuance of common stock under employee stock purchase plan, shares		54
Stock-based compensation expense	38,808		38,808
Unrealized gain (loss) on available-for-sale securities, net	(2,209)			(2,209)
Net income (loss)	127,840				127,840
Balances at Dec. 31, 2021	$ 764,298	$ 4	$ 928,095	$ (2,569)	$ (161,232)
Balances (Shares) at Dec. 31, 2021		42,831

Consolidated Statements of Stockholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($)
Common Stock [Member]
Issuance of Stock, transaction costs	$ 14,194

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net income (loss)	$ 127,840	$ (111,250)	$ (94,733)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities
Stock-based compensation expense	38,808	31,949	26,854
Depreciation and amortization	9,564	8,407	7,152
Provision for credit losses (recoveries)	(2,569)	7,678	0
Net amortization of premiums (accretion of discounts) on marketable debt securities	5,842	1,083	(1,196)
Net gains on investments	(5,189)	(4,918)	(37,774)
Imputed interest income from licensing	(360)	(2,163)	(2,951)
Non-cash interest expense	4,642	771
Other non-cash adjustments	79	163	268
Changes in operating assets and liabilities
Accounts receivable	14,118	(9,898)	(8,622)
Prepaid expenses	(8,247)	(4,030)	(973)
Other current assets	(7,314)	2,341	(499)
Operating lease right-of-use assets	4,866	3,219	2,431
Other assets	(2,272)	399	(2,694)
Accounts payable	(2,304)	3,873	1,528
Accrued expenses and other current liabilities	29,908	17,400	6,882
Deferred revenue	(899)		(600)
Operating lease liabilities	12,073	2,139	(2,255)
Other liabilities	289	(1,224)	(523)
Net cash provided by (used in) operating activities	218,875	(54,061)	(107,705)
Cash flows from investing activities
Purchases of marketable debt securities	(498,144)	(123,041)	(190,735)
Maturities of marketable debt securities	170,086	233,468	289,994
Sales of marketable debt securities		2,287
Sales of equity securities	5,591	36,914	6,020
Purchases of property and equipment	(84,175)	(26,869)	(11,720)
Net cash provided by (used in) investing activities	(406,642)	122,759	93,559
Cash flows from financing activities
Proceeds from exercise of stock options	4,281	5,623	7,062
Taxes paid related to net settlement of stock options	(2)
Proceeds from issuance of common stock under employee stock purchase plan	1,768	1,799	1,314
Proceeds from public offering of common stock, net of underwriting discounts and commissions	216,438
Issuance costs for public offering of common stock	(379)
Proceeds from sale of future royalties		196,000
Repayments under liability related to sale of future royalties, net of imputed interest	(26,591)
Transaction costs for sale of future royalties	(265)	(3,208)
Net cash provided by financing activities	195,250	200,214	8,376
Net increase (decrease) in cash and cash equivalents and restricted cash	7,483	268,912	(5,770)
Cash and cash equivalents and restricted cash
Beginning of period	339,756	70,844	76,614
End of period	347,239	339,756	70,844
Supplemental cash flow information
Cash paid (received) for income taxes	5,996	(191)	904
Cash paid for imputed interest under liability related to sale of future royalties	21,635
Supplemental disclosures of non-cash investing and financing activities
Increase in accounts payable and accrued liabilities related to purchases of property and equipment	558	6,812	$ 1,572
Non-cash additions to property and equipment through tenant improvement allowance		2,263
Non-cash consideration received for licenses granted		1,123
Transaction costs for sale of future royalties in accounts payable and other current liabilities		$ 265
Proceeds due to Company from sales of non-marketable equity securities	$ 600

Nature of Business

12 Months Ended

Dec. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Nature of Business

1. Nature of Business

REGENXBIO Inc. (the Company) is a clinical-stage biotechnology company seeking to improve lives through the curative potential of gene therapy. The Company has developed a broad pipeline of gene therapy product candidates using its proprietary adeno-associated virus (AAV) gene delivery platform (NAV Technology Platform), which consists of exclusive rights to over 100 novel AAV vectors, including AAV7, AAV8, AAV9 and AAVrh10. In addition to its internal product development efforts, the Company also selectively licenses the NAV® Technology Platform to other leading biotechnology and pharmaceutical companies (NAV Technology Licensees). As of December 31, 2021, the NAV Technology Platform was being applied by NAV Technology Licensees in one commercially available product, Zolgensma®, and in the preclinical and clinical development of a number of licensed products. Additionally, the Company has licensed intellectual property rights to collaborators for the joint development and commercialization of certain product candidates. The Company was formed in 2008 in the State of Delaware and is headquartered in Rockville, Maryland.

As of December 31, 2021, the Company had generated an accumulated deficit of $161.2 million since inception. As the Company has incurred cumulative losses since inception, transition to recurring profitability is dependent upon achieving a level of revenues adequate to support the Company’s cost structure, which depends heavily on the successful development, approval and commercialization of its product candidates. The Company may never achieve recurring profitability, and unless and until it does, the Company will continue to need to raise additional capital, to the extent possible. As of December 31, 2021, the Company had cash, cash equivalents and marketable securities of $849.3 million, which management believes is sufficient to fund operations for at least the next 12 months from the date these consolidated financial statements were issued.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation and Principles of Consolidation

The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (GAAP) and include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

Foreign Currency Transactions

The functional currency of the Company and its consolidated subsidiaries is the U.S. dollar. Transaction gains and losses that arise from exchange rate fluctuations on transactions denominated in currencies other than the U.S. dollar are included in results of operations as incurred.

Use of Estimates

The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and related disclosure of contingent assets and liabilities for the periods presented. Management bases its estimates on historical experience and various other factors that it believes are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities, and other reported amounts, that are not readily apparent from other sources. Actual results may differ materially from these estimates. Significant estimates are used in the following areas, among others: license and royalty revenue, the allowance for credit losses, accrued research and development expenses and other accrued liabilities, stock-based compensation expense, interest expense under the liability related to the sale of future royalties, income taxes and the fair value of financial instruments.

The Company is actively monitoring the impact of the COVID-19 pandemic on its business, results of operations and financial condition. The full extent to which the COVID-19 pandemic will directly or indirectly impact the Company’s business, results of operations and financial condition in the future is unknown at this time and will depend on future developments that are highly unpredictable. The most significant estimates affecting the Company’s consolidated financial statements that may be impacted by the COVID-19 pandemic are related to the Company’s assessment of credit losses on accounts receivable, contract assets and available-for-sale debt securities.

Segment and Geographical Information

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker (CODM), or decision-making group, in making decisions on how to allocate resources and assess performance. The Company’s CODM, its Chief Executive Officer, views the Company’s operations and manages the business as one operating segment.

The Company’s revenues consist of license and royalty revenue. For the year ended December 31, 2021, 79% and 7% of the Company’s revenues were attributed to Bermuda and the U.S., respectively, and no other countries were attributed 10% or more of the Company’s revenues. For the year ended December 31, 2020, 80% of the Company’s revenues were attributed to the U.S. and no other countries were attributed 10% or more of the Company’s revenues. For the year ended December 31, 2019, 90% of the Company’s revenues were attributed to the U.S. and no other countries were attributed 10% or more of the Company’s revenues. The country of origin for license revenue is determined based on the country of domicile of the licensee. The country of origin for royalty revenue is determined based on the location of the underlying net sales of licensed products. The substantial majority of the Company’s assets reside in the U.S.

Cash and Cash Equivalents

The Company considers all highly liquid investments purchased with original maturities of 90 days or less at acquisition to be cash equivalents.

Restricted Cash

Restricted cash includes money market mutual funds and other deposits used to collateralize irrevocable letters of credit required under the Company’s lease agreements and other certain agreements. The following table provides a reconciliation of cash and cash equivalents and restricted cash as reported on the consolidated balance sheets to the total of these amounts as reported at the end of the period in the consolidated statements of cash flows (in thousands):

	As of December 31,
	2021		2020		2019
Cash and cash equivalents	$	345,209	$	338,426	$	69,514
Restricted cash		2,030		1,330		1,330
Total cash and cash equivalents and restricted cash	$	347,239	$	339,756	$	70,844

Marketable Securities

Marketable securities consist of available-for-sale debt securities and equity securities and are carried at fair value. Marketable debt securities with remaining maturity dates exceeding 12 months which are not intended to be sold prior to maturity for use in current operations are classified as non-current assets. Marketable equity securities are classified as current assets.

Unrealized gains and losses on available-for-sale debt securities, net of any related tax effects, are excluded from results of operations and are included in other comprehensive income (loss) and reported as a separate component of stockholders’ equity until realized. The Company uses the aggregate portfolio approach to release the tax effects of unrealized gains and losses on available-for-sale debt securities in accumulated other comprehensive loss. Purchase premiums and discounts on marketable debt securities are amortized or accreted into the cost basis over the life of the related security as adjustments to the yield using the effective-interest method. Interest income is recognized when earned. Unrealized gains and losses on marketable equity securities are included in results of operations as investment income. Realized gains and losses from the sale or maturity of marketable securities are based on the specific identification method and are included in results of operations as investment income.

At each reporting date, the Company evaluates available-for-sale debt securities which have an amortized cost basis in excess of the fair value of the security to determine if the unrealized loss or any potential credit losses should be recognized in results of operations. If the Company does not have the intent and ability to hold the security until recovery of the unrealized loss, the difference between the fair value and amortized cost basis of the security is charged to results of operations resulting in a new amortized cost basis of the security. If the Company has the intent and ability to hold the security until recovery of the unrealized loss, the security is evaluated for potential credit losses. If a credit loss is deemed to exist, the credit loss is recognized in results of operations and an allowance for credit losses is recorded against the amortized cost basis of the security. In determining whether a credit loss exists related to impaired available-for-sale debt securities, the Company considers, among other factors, the extent of the unrealized loss relative to the amortized cost basis, the credit rating of the issuer and any recent changes thereto, current and expected future

economic conditions, and any adverse events or other changes in circumstances that have occurred which may indicate a potential credit loss. The Company did not record an allowance for credit losses on its available-for-sale debt securities as of December 31, 2021 or 2020.

Accounts Receivable

Accounts receivable primarily consist of consideration due to the Company resulting from its license agreements with customers. Accounts receivable include amounts invoiced to licensees as well as rights to consideration which have not yet been invoiced, including unbilled royalties, and for which payment is conditional solely upon the passage of time. If a licensee elects to terminate a license prior to the end of the license term, the licensed intellectual property is returned to the Company and any accounts receivable from the licensee which are not contractually payable to the Company are charged off as a reduction of license revenue in the period of the termination. Accounts receivable which are not expected to be received by the Company within 12 months from the reporting date are stated net of a discount to present value and recorded as non-current assets on the consolidated balance sheets. The present value discount is recognized as a reduction of revenue in the period in which the accounts receivable are initially recorded and is accreted as interest income from licensing over the term of the receivables.

Accounts receivable are stated net of an allowance for credit losses, if deemed necessary based on the Company’s evaluation of collectability and potential credit losses. Management assesses the collectability of its accounts receivable using the specific identification of account balances, and considers the credit quality and financial condition of its significant customers, historical information regarding credit losses and the Company’s evaluation of current and expected future economic conditions. If necessary, an allowance for credit losses is recorded against accounts receivable such that the carrying value of accounts receivable reflects the net amount expected to be collected. Accounts receivable balances are written off against the allowance for credit losses when the potential for collectability is considered remote. Please refer to Note 10 for further information regarding the allowance for credit losses related to accounts receivable.

Concentrations of Credit Risk and Off-balance Sheet Risk

Cash and cash equivalents, marketable debt securities and accounts receivable are financial instruments that are potentially subject to concentrations of credit risk. The Company’s cash and cash equivalents are deposited in accounts at multiple financial institutions, and amounts may exceed federally insured limits. The Company believes it is not exposed to significant credit risk due to the financial strength of the depository institutions in which the cash and cash equivalents are held. The Company’s marketable debt securities consist of investment grade securities and may be subject to concentrations of credit risk. The Company has adopted an investment policy which limits potential concentrations of investments and establishes minimum acceptable credit ratings, thereby reducing credit risk exposure. With the exception of accounts receivable from Abeona Therapeutics Inc. (Abeona), as discussed further in Note 10, the Company believes that it is not exposed to significant credit risk related to accounts receivable due to the credit quality and history of collections from its significant customers, and the Company is unaware of any concentrations of credit risk related to accounts receivable from significant customers with deteriorated credit quality. The Company has no financial instruments with off-balance sheet risk of loss.

The following table summarizes those customers who represented at least 10% of revenues or total net accounts receivable for the periods presented:

	Revenues									Accounts Receivable, Net
	Years Ended December 31,									As of December 31,
	2021			2020			2019			2021			2020
Customer A		79	%	*			*			*			*
Customer B		20	%		94	%		69	%		77	%		44	%
Customer C	*			*			*				14	%		48	%
Customer D	*			*				13	%	*			*
Customer E	*			*				10	%	*			*

*	Represented less than 10%

Leases

Effective January 1, 2019, the Company adopted Accounting Standards Update (ASU) 2016-02, Leases (Topic 842) which supersedes the lease accounting requirements in Accounting Standards Codification (ASC) 840, Leases (Topic 840). Please refer to Recent Accounting Pronouncements below for additional information on the adoption of Topic 842 and the associated impact to the Company’s consolidated financial statements.

Under Topic 842, the Company classifies its leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the Company. Lease classification is evaluated at the inception of the lease agreement. Regardless of classification, the Company records a right-of-use asset and a lease liability for all leases with a term greater than 12 months. All of the Company’s leases as of December 31, 2021 and 2020 have been classified as operating leases. Operating lease expense is recognized on a straight-line basis over the term of the lease, with the exception of variable lease expenses which are recognized as incurred.

The Company identifies leases in its contracts if the contract conveys the right to control the use of identified property, plant or equipment for a period of time in exchange for consideration. The Company does not allocate lease consideration between lease and nonlease components and records a lease liability equal to the present value of the remaining fixed consideration under the lease. The interest rates implicit in the Company’s leases are generally not readily determinable. Accordingly, the Company uses its estimated incremental borrowing rate at the commencement date of the lease to determine the present value discount of the lease liability. The Company estimates its incremental borrowing rate for each lease based on an evaluation of its expected credit rating and the prevailing market rates for collateralized debt in a similar economic environment with similar payment terms and maturity dates commensurate with the term of the lease. The right-of-use asset for each lease is equal to the lease liability, adjusted for unamortized initial direct costs and lease incentives and prepaid or accrued rent. Initial direct costs of entering into a lease are included in the right-of-use asset and amortized as lease expense over the term of the lease. Lease incentives, such as tenant improvement allowances, are recorded as a reduction of the right-of-use asset and amortized as a reduction of lease expense over the term of the lease. The Company excludes options to extend or terminate leases from the calculation of the lease liability unless it is reasonably certain the option will be exercised.

Property and Equipment

Property and equipment is stated at cost less accumulated depreciation and amortization. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred. Upon disposal, the related cost and accumulated depreciation is removed from the accounts and any resulting gain or loss is included in the results of operations. Depreciation and amortization is calculated using the straight-line method over the estimated useful lives of the assets, which are as follows:

	Estimated Useful Life
Computer equipment and software	3 years
Furniture and fixtures	5 years
Laboratory and manufacturing equipment	5 to 15 years
Leasehold improvements	Shorter of lease term or estimated useful life

Impairment of Long-lived Assets

The Company evaluates its long-lived assets for impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparison of the book values of the assets to estimated future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book value of the assets exceed their fair value, which is measured based on the projected discounted future net cash flows arising from the assets. No impairment losses on long-lived assets were recorded during the years ended December 31, 2021, 2020 and 2019.

Non-marketable Equity Securities

The Company’s non-marketable equity securities consist of equity investments in other entities in which the Company’s ownership interest is below 20% and the Company does not have significant influence over the operations of the entity, or for which the equity securities are not common stock or in-substance common stock. The Company’s non-marketable equity securities do not have readily determinable fair values and are measured at cost less impairment, adjusted for observable price changes for identical or similar investments of the same issuer. Please refer to Note 4 for further information on non-marketable equity securities.

Fair Value of Financial Instruments

The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. ASC 820, Fair Value Measurements and Disclosures, establishes a hierarchy of inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability, and are developed based on the best information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The three levels of the fair value hierarchy are described below:

•

Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

•

Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly.

•

Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable.

To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The fair values of the Company’s Level 2 instruments are based on quoted market prices or broker or dealer quotations for similar assets. These investments are initially valued at the transaction price and subsequently valued utilizing third party pricing providers or other market observable data. Please refer to Note 4 for further information on the fair value measurement of the Company’s financial instruments.

Liability Related to Sale of Future Royalties

As discussed in Note 7, the Company recorded a liability for the net proceeds received from the sale of its Zolgensma royalty payments to entities managed by Healthcare Royalty Management, LLC (collectively, HCR). The liability is accounted for as debt since the return to HCR is explicitly capped under the royalty purchase agreement, and is amortized over the estimated life of the arrangement using the effective interest method. The total amount of royalty payments received by HCR under the agreement, less the net proceeds received by the Company, is recorded as interest expense over the life of the arrangement. The Company estimates the effective interest rate based on its estimate of total royalty payments to be received by HCR under the agreement. The Company reassesses these estimates at each reporting date and adjusts the effective interest rate and amortization of the liability on a prospective basis as necessary.

Due to its continuing involvement in the underlying license agreement with Novartis Gene Therapies, Inc. (formerly AveXis, Inc.), the Company continues to recognize royalty revenue on net sales of Zolgensma and records the royalty payments to HCR as a reduction of the liability when paid. As such payments are made to HCR, the balance of the liability will be effectively repaid over the life of the royalty purchase agreement. The portion of the liability related to the sale of future royalties which is expected to be amortized within 12 months of the reporting date is recorded as a current liability, with the remaining portion of the liability recorded as a non-current liability.

Revenue Recognition

The Company recognizes revenue in accordance with ASC 606, Revenue from Contracts with Customers (Topic 606). Topic 606 requires entities to recognize revenue when control of the promised goods or services is transferred to customers at an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services. The following five steps are performed to determine the appropriate revenue recognition for arrangements within the scope of Topic 606: (i) identify the contract(s) with a customer, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract and (v) recognize revenue when (or as) the entity satisfies the performance obligations.

The Company applies the five-step model to contracts that are within the scope of Topic 606 only when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract

inception, for contracts within the scope of Topic 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations and whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to respective performance obligations when (or as) the respective performance obligations are satisfied.

The Company evaluates its contracts with customers for the presence of significant financing components. If a significant financing component is identified in a contract and provides a financing benefit to the customer, the transaction price for the contract is adjusted to account for the financing portion of the arrangement, which is recognized as interest income over the financing term using the effective interest method. In determining the appropriate interest rates for significant financing components, the Company evaluates the credit profile of the customer and prevailing market interest rates and selects an interest rate in which it believes would be charged to the customer in a separate financing arrangement over a similar financing term.

License and Royalty Revenue

The Company licenses its NAV Technology Platform and other intellectual property rights to other biotechnology and pharmaceutical companies, including collaborators for the joint development and commercialization of its product candidates. The terms of the licenses vary, and licenses may be exclusive or non-exclusive and may be sublicensable by the licensee. Licenses may grant intellectual property rights for purposes of internal and preclinical research and development only, or may include the rights, or options to obtain future rights, to commercialize drug therapies for specific diseases using the Company’s NAV Technology Platform and other licensed rights. License agreements generally have a term at least equal to the life of the underlying patents, but are terminable at the option of the licensee. Consideration payable to the Company under its license agreements may include: (i) up-front and annual fees, (ii) milestone payments based on the achievement of certain development and sales-based milestones, (iii) sublicense fees, (iv) royalties on sales of licensed products and (v) other consideration payable upon optional goods and services purchased by licensees.

The Company’s license agreements are accounted for as contracts with customers within the scope of Topic 606, with the exception of transactions for which the counterparty is determined not to be a customer. At the inception of each license agreement, the Company determines the contract term for purposes of applying the requirements of Topic 606. Licenses are generally terminable at the option of the licensee with advance notice to the Company. For each license granted, including licenses granted upon the exercise of license options, the Company evaluates these termination rights to determine whether a substantive termination penalty would be incurred by the licensee upon termination. If the licensee incurs a substantive termination penalty upon termination, the contract term for revenue recognition purposes is generally equal to the stated term of the license, which is the life of the underlying licensed patents. Alternatively, if the licensee does not incur a substantive termination penalty upon termination, the contract term for revenue recognition purposes may be shorter than the stated term of the license, in which case the termination rights may be accounted for as contract renewal options. The determination of whether a substantive termination penalty is associated with the termination rights requires significant judgment. In making this determination, the Company considers, among other things, the nature of the intellectual property rights that would be returned to the Company upon termination, including the exclusivity of the licensed rights and the stage of development of the licensed products, the payment terms, including the amount and timing of non-refundable or guaranteed payments, and the business purpose of the termination rights granted to the licensee. Generally, the most significant judgment in determining whether a substantive termination penalty exists relates to the amount of any up-front or guaranteed non-refundable payments relative to the amount of annual payments that may be avoided by the licensee upon termination of the license. The Company considers all of the facts and circumstances relevant to each license when making this determination.

Performance obligations under the Company’s license agreements may include (i) the delivery of intellectual property licenses, (ii) options granted to licensees to acquire additional licenses, to the extent the options represent material rights to the licensee, and (iii) research and development services to be performed by the Company related to licensed products. License agreements may provide licensees with contract renewal options or options to acquire additional licenses, goods or other services. Options are evaluated at the inception of the license agreement to determine whether they provide material rights to the licensee. In making this determination, the Company considers whether the options are priced at an incremental discount to the standalone selling price for the underlying licenses, goods or services, in which case the option is considered to be a material right to the licensee and is accounted for as a separate performance obligation under the current license agreement. At the inception of each license agreement which contains performance obligations for research and development services, the Company evaluates whether the license is distinct from the research and development services, which requires judgment. In making this determination, the Company considers, among other things, the stage of development of the licensed products and whether the research and development services will significantly impact further development of the licensed products. If it is determined that the license is not distinct from the research and development services, the license is combined with the research and development services into a single performance obligation.

The Company evaluates the transaction price of its license agreements at the inception of each agreement and at each reporting date. The transaction price includes the fixed consideration payable to the Company during the contract term, as well as any variable consideration to the extent that it is probable that a significant reversal of revenue will not occur in the future. Fixed consideration under the license agreements includes up-front and annual fees payable during the contract term. Variable consideration under the license agreements includes development and sales-based milestone payments, sublicense fees and royalties on sales of licensed products. Consideration contingent upon the exercise of options by a licensee is excluded from the transaction price and not accounted for as part of the license agreement until the option is exercised.

The transaction price for each license agreement is allocated to the underlying performance obligations based on their relative standalone selling prices and recognized as revenue when (or as) the performance obligations are satisfied. Consideration allocated to performance obligations for the delivery of an intellectual property license is recognized as revenue in full upon the delivery of the license to the licensee. Consideration allocated to performance obligations for license options is recognized as revenue in full upon the earlier of the option exercise or expiration. The exercise of a license option by a licensee is accounted for as a new license for revenue recognition purposes. Consideration allocated to performance obligations for research and development services is recognized as revenue as the services are performed by the Company.

Up-front and annual licenses fees payable to the Company over the contract term of each license are included in the transaction price, and the portion of this consideration allocated to the performance obligation for the delivery of the intellectual property license is recognized as revenue in full upon the delivery of the license to the licensee. If annual license fees are payable to the Company in periods beyond 12 months from the delivery of the license, a significant financing component is deemed to exist which provides a financing benefit to the licensee. If a significant financing component is identified, the Company adjusts the transaction price for the license to include only the present value of the annual license fees payable to the Company over the contract term. The discounted portion of the license fees is recognized as interest income from licensing over the financing period of the license.

Development milestone payments are payable to the Company upon the achievement of specified development milestones. At the inception of each license agreement that contains development milestone payments, the Company evaluates whether the milestones are considered probable of achievement and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal will not occur in the future, milestone payments are included in the transaction price and recognized as revenue upon the delivery of the license. Milestone payments contingent on the achievement of development milestones that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved and are excluded from the transaction price until the milestone is achieved. At each reporting date, the Company re-evaluates the probability of achievement of each outstanding development milestone and, if necessary, adjusts the transaction price for any milestones for which the probability of achievement has changed due to current facts and circumstances. Any such adjustments are recorded on a cumulative catch-up basis and recognized as revenue in the period of the adjustment.

Royalties on sales of licensed products, sales-based milestone payments, including milestones payable upon first commercial sales of licensed products, and sublicense fees based on the receipt of certain fees by licensees from any sublicensees are excluded from the transaction price of each license and recognized as revenue in the period that the related sales or sublicenses occur, provided that the associated license has been delivered to the licensee.

Royalty revenue to date consists primarily of royalties on net sales of Zolgensma, which is a licensed product under the Company’s license agreement with Novartis Gene Therapies, Inc. (formerly AveXis, Inc.) (Novartis Gene Therapies), a wholly owned subsidiary of Novartis AG (Novartis), for the development and commercialization of treatments for spinal muscular atrophy (SMA). The Company recognizes royalty revenue from net sales of Zolgensma in the period in which the underlying products are sold by Novartis Gene Therapies, which in certain cases may require the Company to estimate royalty revenue for periods of net sales which have not yet been reported to the Company. Estimated royalties are reconciled to actual amounts reported in subsequent periods, and any differences are recognized as an adjustment to royalty revenue in the period the royalties are reported. Sales-based milestone payments related to net sales of Zolgensma are recognized as royalty revenue in the period in which the milestone is achieved.

The Company receives payments from licensees based on the billing schedules established in each license agreement. Amounts recognized as revenue which have not yet been received from licensees, including unbilled royalties, are recorded as accounts receivable when the Company’s rights to the consideration are conditional solely upon the passage of time. Amounts recognized as revenue which have not yet been received from licensees are recorded as contract assets when the Company’s rights to the consideration are not unconditional. Contract assets are recorded as other current assets on the consolidated balance sheets if the consideration is expected to be realized within 12 months from the reporting date, or as other assets if the consideration is expected to be realized in periods beyond 12 months from the reporting date. If a licensee elects to terminate a license prior to the end of the license term, the licensed intellectual property is returned to the Company and any consideration recorded as accounts receivable or contract assets which is not contractually payable by the licensee is charged off as a reduction of license revenue in the period of the

termination. Amounts received by the Company prior to the delivery of underlying performance obligations are deferred and recognized as revenue upon the satisfaction of the performance obligations by the Company. Deferred revenue which is not expected to be recognized within 12 months from the reporting date is recorded as non-current on the consolidated balance sheets.

Collaborative Arrangements

The Company evaluates its agreements with collaboration partners to determine whether they are within the scope of ASC 808, Collaborative Arrangements (Topic 808). Such arrangements are within the scope of Topic 808 if they involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities. This evaluation is performed throughout the life of the arrangement based on any changes in the roles and responsibilities of the parties under the arrangement. For collaboration arrangements within the scope of Topic 808 that contain multiple elements, the Company identifies the various transactions with the counterparty and determines if any unit of account is more reflective of a transaction with a customer and therefore should be accounted for within the scope of Topic 606. For transactions that are accounted for pursuant to Topic 808, an appropriate method of recognition and presentation is determined and consistently applied. For transactions that are accounted for pursuant to Topic 606, the Company applies the five-step model as described in its revenue recognition policies.

For transactions accounted for as collaborative arrangements under Topic 808, payments to and from collaboration partners associated with multiple activities in a collaboration arrangement are classified based on the nature of each separate activity. Payments associated with development activities performed are recorded as research and development expense when owed to collaboration partners, or as a reduction of research and development expense when due from collaboration partners. Payments associated with commercialization activities performed are recorded as general and administrative expense when owed to collaboration partners, or as a reduction of general and administrative expense when due from collaboration partners. At the end of each reporting period, the Company records a net amount due to or from collaboration partners for activities performed by the parties under the collaboration.

Cost of Revenues

Cost of revenues consists primarily of sublicense fees, milestone payments and royalties on net sales of licensed products as specified in the Company’s agreements with its licensors. Sublicense fees are based on a percentage of license fees received by the Company from licensees and are recognized in the period that the underlying revenue is recognized. Milestone payments are payable to licensors upon the achievement of specified milestones by licensees and are recognized in the period the milestone is achieved or deemed probable of achievement. Royalties are based on a percentage of net sales of licensed products by licensees and are recognized in the period that the underlying sales occur. Amounts which are payable to licensors in periods beyond 12 months from the reporting date are recorded as non-current liabilities on the consolidated balance sheets.

Research and Development Expenses

Research and development costs are expensed as incurred in performing research and development activities. Advance payments for goods or services related to research and development activities are deferred and expensed as the goods are delivered or the services are performed. Research and development costs include salaries, wages, benefits and other personnel costs, laboratory and facilities costs, allocated overhead costs, license and milestone fees, and costs of goods and services associated with preclinical research and clinical trial activities, associated manufacturing-related activities, regulatory activities and other related services performed by third-parties. At the end of each reporting period, the Company compares payments made to third-party service providers to the estimated expenses incurred based on the services provided and progress toward completion of the research or development objectives. Such estimates are subject to change as additional information becomes available. Depending on the timing of payments to the service providers and the estimated expenses incurred, the Company may record net prepaid or accrued research and development expenses relating to these costs. Up-front fees incurred in obtaining technology licenses, as well as milestone payments to licensors, are charged to research and development expense as incurred if the technology licensed has no alternative future use.

Stock-based Compensation

The Company accounts for its stock-based compensation awards in accordance with ASC 718, Compensation—Stock Compensation. ASC 718 requires all stock-based awards to employees and nonemployees to be recognized as expense based on the grant date fair value of the awards. The Company’s stock-based awards include stock options granted to employees and nonemployees, restricted stock units granted to employees and shares issued to employees under its employee stock purchase plan.

The Company’s stock-based awards may be subject to either service or performance-based vesting conditions. Compensation expense related to awards with service-based vesting conditions is recognized on a straight-line basis based on the estimated grant date fair value over the requisite service period of the award, which is generally the vesting term. Compensation expense related to awards with performance-based vesting conditions is recognized based on the estimated grant date fair value over the requisite service period using the accelerated attribution method to the extent achievement of the performance condition is probable.

The Company has elected to not estimate forfeitures of stock-based awards and accounts for forfeitures as they occur.

The Company estimates the fair value of its stock option awards using the Black-Scholes option-pricing model, which requires the input of subjective assumptions, including (i) the fair value of the underlying common stock, (ii) the expected stock price volatility, (iii) the expected term of the award, (iv) the risk-free interest rate and (v) expected dividends. For reporting periods through December 31, 2020, the Company did not have sufficient historical or implied volatility data for its common stock necessary to estimate expected volatility over a period of time commensurate with the expected term of its stock option awards. For such reporting periods, the Company estimated expected volatility based on a weighted-average of the historical volatility of its common stock and the common stock of a selected peer group of similar publicly traded companies for which sufficient historical volatility data was available. As more historical trading data became available over time, the Company gradually increased the weight placed on the historical volatility of its common stock versus the historical peer group volatility data. Effective January 1, 2021, the Company eliminated the use of historical peer group volatility data and now estimates expected volatility based solely on the historical volatility of its common stock given that sufficient historical volatility data has become available. The Company estimates the expected term of its employee stock options using the “simplified” method, whereby the expected term equals the arithmetic average of the vesting term and the original contractual term of the option, due to its lack of sufficient historical data. For stock options granted to nonemployees, the Company uses the contractual term of the award rather than expected term to estimate the fair value of the award. The Company estimates the risk-free interest rates for periods within the expected term of its options based on the rates of U.S. Treasury securities with maturity dates commensurate with the expected term of the associated awards. The Company assumes a dividend yield of zero for its common stock as it has never paid dividends and does not expect to pay dividends for the foreseeable future.

The Company estimates the fair value of restricted stock units based on the fair value of the Company’s common stock on the date of the grant.

Income Taxes

Income taxes are accounted for in accordance with ASC 740, Income Taxes, which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the consolidated financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are provided, if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.

The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances.

The Company recognizes interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2021 and 2020, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company’s consolidated statements of operations and comprehensive income (loss).

Net Income (Loss) Per Share

Basic net income (loss) per share is calculated by dividing net income (loss) applicable to common stockholders by the weighted-average common shares outstanding during the period, without consideration for common stock equivalents. Diluted net income (loss) per share is calculated by adjusting the weighted-average common shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock method. Contingently convertible shares in which conversion is based on non-market-priced contingencies are excluded from the calculations of both basic and diluted net income (loss) per share until the contingency has been fully met. For purposes of the diluted net income (loss) per share calculation, common stock equivalents are excluded from the calculation of diluted net income (loss) per share if their effect would be anti-dilutive.

Comprehensive Income (Loss)

Comprehensive income (loss) includes net income (loss) as well as unrealized gains and losses on available-for-sale debt securities, net of income tax effects and reclassification adjustments for realized gains and losses.

Correction of Previously Issued Financial Statements

During the quarter ended December 31, 2021, the Company identified an immaterial error in the presentation of payments made under the liability related to the sale of future royalties in the consolidated statements of cash flows for the three months ended March 31, 2021, six months ended June 30, 2021 and nine months ended September 30, 2021. Payments made under the liability related to the sale of future royalties were presented as cash outflows from financing activities in the interim financial statements for these periods. Upon further review, the Company determined that the amount of these payments attributable to imputed interest expense should be presented as cash outflows from operating activities, and only the amount attributable to principal repayments should be presented as cash outflows from financing activities. The amounts previously reported as cash outflows from financing activities which should have been reported as cash outflows from operating activities were $2.9 million for the three months ended March 31, 2021, $9.1 million for the six months ended June 30, 2021 and $15.3 million for the nine months ended September 30, 2021. The Company evaluated the materiality of these errors from both a quantitative and qualitative perspective and concluded that they were immaterial to the aforementioned previously issued interim financial statements taken as a whole. The Company has corrected the presentation of these cash flows in the accompanying consolidated statement of cash flows for the year ended December 31, 2021. The error in presentation did not have an impact on the financial statements for any periods prior to 2021, and did not have an impact on the previously reported assets, liabilities, stockholders’ equity or results of operations for the interim periods ended March 31, 2021, June 30, 2021 and September 30, 2021. Although the Company has determined that this error was not material to its previously issued interim financial statements for 2021, the Company is revising the previously issued interim financial statements to correct for such error, which revision will be effected in connection with its future filings of Form 10-Q for interim periods in 2022. The accompanying consolidated financial statements for the year ended December 31, 2021 reflect the as corrected annualized impact of correcting the error.

Recent Accounting Pronouncements

Recently Adopted Accounting Pronouncements

In June 2016, the Financial Accounting Standards Board (FASB) issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which amends the accounting for credit losses for most financial assets and certain other instruments. The standard requires that entities holding financial assets that are not accounted for at fair value through net income be presented at the net amount expected to be collected by recording an allowance for credit losses. The allowance for credit losses will be a valuation account that will be deducted from the amortized cost basis of the financial asset to present the net carrying value at the amount expected to be collected on the financial asset. The standard also amends the impairment model for available-for-sale debt securities, requiring credit losses on impaired debt securities to be included in results of operations. The Company adopted this standard effective January 1, 2020 using a modified retrospective transition method, which requires a cumulative-effect adjustment, if any, to opening accumulated deficit on the adoption date. The adoption of this standard primarily impacts the Company’s methodology used to assess credit losses on its accounts receivable, contract assets and available-for-sale debt securities. Based on the composition of the Company’s accounts receivable, contract assets and available-for-sale debt securities, the adoption of this standard required no cumulative-effect adjustments and did not have a material impact on the Company’s financial position or results of operations. Please refer to the significant accounting policies above for a description of the Company’s accounting policies for accounts receivable and marketable securities upon the adoption of this standard.

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which modifies certain disclosure requirements regarding fair value measurements. The Company adopted this standard effective January 1, 2020. The adoption of this standard did not have a material impact on the Company’s financial statement disclosures.

In August 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. The standard aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The Company adopted this standard effective January 1, 2020 on a prospective basis. The Company has various cloud-based software applications accounted for as service contracts, the most significant of which is the Company’s enterprise resource planning (ERP) system for which implementation was in progress on the adoption date of this standard. The adoption of this standard resulted in the capitalization of certain costs during the years ended December 31, 2021 and 2020 related to the implementation of the ERP system and other cloud-based software applications which would have been expensed as incurred prior to the adoption of this standard. Once implementation activities are substantially complete and the cloud-based application is ready for its intended use, capitalization of implementation costs ceases and amounts capitalized are amortized on a straight-line basis over the term of the hosting arrangement. Capitalized implementation costs for cloud-based applications are classified on the consolidated balance sheets and statements of operations and comprehensive income (loss) in the same manner as the costs of the associated hosting arrangement. As of December 31, 2021 and 2020, the Company had recorded capitalized costs, net of amounts amortized, of $3.3 million and $1.6 million, respectively, related to the implementation of cloud-based software applications accounted for as service contracts, which were included in prepaid expenses and other assets in the consolidated balance sheets. Amortization of capitalized implementation costs for cloud-based applications recorded for the years ended December 31, 2021 and 2020 was $0.6 million and $0.1 million, respectively, and was in included in general and administrative expenses in the consolidated statements of operations and comprehensive income (loss).

In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740)—Simplifying the Accounting for Income Taxes, which simplifies the current accounting for income taxes. Among other changes, the standard removes the exception to the incremental approach for intraperiod tax allocation when there is a loss from continuing operations and income or a gain from other items such as other comprehensive income. The Company early adopted this standard effective January 1, 2020, with certain aspects of the standard applied using the modified retrospective transition method and other aspects of the standard applied on a prospective basis. The adoption of this standard required no cumulative-effect adjustments and did not have a material impact on the Company’s financial position or results of operations.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) which supersedes the lease accounting requirements in ASC 840, Leases (Topic 840). Effective January 1, 2019, the Company adopted Topic 842 using the modified retrospective transition method. Under this method, the Company applied Topic 842 to all leases in effect as of, or entered into after, January 1, 2019 and recorded the cumulative impact of the adoption as an adjustment to its accumulated deficit on January 1, 2019. The cumulative impact of the adoption of Topic 842 resulted in an increase in accumulated deficit of less than $0.1 million on January 1, 2019. The adoption of Topic 842 did not have a material impact on the Company’s results of operations for years ended December 31, 2021, 2020 and 2019, nor does the Company believe it will have a material impact on future results of operations based on its current leasing arrangements. Please refer to the significant accounting policies above for a description of the Company’s lease accounting policies upon the adoption on Topic 842.

In February 2018, the FASB issued ASU 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, which amends the previous guidance on comprehensive income to provide an option for an entity to reclassify the stranded tax effects of the Tax Cuts and Jobs Act of 2017 (the TCJA) that was signed into law in December 2017 from accumulated other comprehensive income directly to retained earnings. The stranded tax effects result from the remeasurement of deferred tax assets and liabilities which were originally recorded in comprehensive income but whose remeasurement is reflected in the income statement. The Company adopted this standard effective January 1, 2019, and upon adoption recorded a cumulative adjustment of less than $0.1 million to reclassify the stranded tax effects of unrealized gains and losses on available-for-sale securities from accumulated other comprehensive income (loss) to accumulated deficit. The adoption of this standard did not have a material impact on the Company’s financial position or results of operations.

Marketable Securities

12 Months Ended

Dec. 31, 2021

Investments Debt And Equity Securities [Abstract]

Marketable Securities

3. Marketable Securities

The following tables present a summary of the Company’s marketable securities, which consist solely of available-for-sale debt securities (in thousands):

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2021
U.S. government and agency securities	$	60,118	$	—	$	(229	)	$	59,889
Certificates of deposit		2,936		2		(11	)		2,927
Corporate bonds		442,792		62		(1,533	)		441,321
	$	505,846	$	64	$	(1,773	)	$	504,137

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2020
U.S. government and agency securities	$	12,782	$	22	$	—		$	12,804
Certificates of deposit		1,956		34		—			1,990
Corporate bonds		165,850		497		(55	)		166,292
Municipal securities		3,035		2		—			3,037
	$	183,623	$	555	$	(55	)	$	184,123

As of December 31, 2021 and 2020, no available-for-sale debt securities had remaining maturities greater than three years. The amortized cost of marketable debt securities is adjusted for amortization of premiums and accretion of discounts to maturity, or to the earliest call date for callable debt securities purchased at a premium.

As of December 31, 2021 and 2020, the balance in accumulated other comprehensive loss consisted solely of unrealized gains and losses on available-for-sale debt securities, net of reclassification adjustments for realized gains and losses and income tax effects. Unrealized gain (loss) on available-for-sale securities, net, presented in the statements of operations and comprehensive income (loss) consisted of the following (in thousands):

	Years Ended December 31,
	2021			2020			2019
Unrealized gain (loss) before reclassifications	$	(2,202	)	$	(426	)	$	1,392
Realized gains reclassified to investment income		(7	)		(139	)		(40	)
Income tax expense		—			—			(467	)
Unrealized gain (loss) on available-for-sale securities, net	$	(2,209	)	$	(565	)	$	885

The following tables present the fair values and unrealized losses of available-for-sale debt securities held by the Company in an unrealized loss position for less than 12 months and 12 months or greater (in thousands):

	Less than 12 Months					12 Months or Greater				Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
December 31, 2021
U.S. government and agency securities	$	59,889	$	(229	)	$	—	$	—	$	59,889	$	(229	)
Certificates of deposit		2,195		(11	)		—		—		2,195		(11	)
Corporate bonds		385,115		(1,533	)		—		—		385,115		(1,533	)
	$	447,199	$	(1,773	)	$	—	$	—	$	447,199	$	(1,773	)

	Less than 12 Months					12 Months or Greater				Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
December 31, 2020
Corporate bonds	$	55,507	$	(55	)	$	—	$	—	$	55,507	$	(55	)
	$	55,507	$	(55	)	$	—	$	—	$	55,507	$	(55	)

As of December 31, 2021, available-for-sale debt securities held by the Company which were in an unrealized loss position consisted of 92 investment grade security positions. The Company has the intent and ability to hold such securities until recovery, and based on the credit quality of the issuers and low severity of each unrealized loss position relative to its amortized cost basis, the Company did not identify any credit losses associated with its available-for-sale debt securities. The Company did not recognize any impairment or credit losses on available-for-sale debt securities during the years ended December 31, 2021, 2020 and 2019.

During the years ended December 31, 2020 and 2019, the Company recognized total net realized and unrealized gains of $4.8 million and $37.8 million, respectively, related to its marketable equity securities of Prevail Therapeutics Inc. (Prevail). The Prevail securities were acquired as consideration for a license to the NAV Technology Platform granted to Prevail in August 2017. Prevail completed its initial public offering (IPO) in June 2019, prior to which the securities were accounted for as non-marketable equity securities without a readily determinable fair value and had a carrying value of $0.4 million. Upon Prevail’s IPO in June 2019, the securities were reclassified to marketable securities and remeasured at fair value at each subsequent reporting date. As of December 31, 2020, the Company had sold all of its Prevail equity securities.

Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

4. Fair Value of Financial Instruments

Financial instruments reported at fair value on a recurring basis include cash equivalents and marketable securities. The following tables present the fair value of cash equivalents and marketable securities in accordance with the hierarchy discussed in Note 2 (in thousands):

	Quoted		Significant
	prices		other		Significant
	in active		observable		unobservable
	markets		inputs		inputs
	(Level 1)		(Level 2)		(Level 3)		Total
December 31, 2021
Cash equivalents:
Money market mutual funds	$	—	$	236,340	$	—	$	236,340
Total cash equivalents		—		236,340		—		236,340
Marketable securities:
U.S. government and agency securities		—		59,889		—		59,889
Certificates of deposit		—		2,927		—		2,927
Corporate bonds		—		441,321		—		441,321
Total marketable securities		—		504,137		—		504,137
Total cash equivalents and marketable securities	$	—	$	740,477	$	—	$	740,477

	Quoted		Significant
	prices		other		Significant
	in active		observable		unobservable
	markets		inputs		inputs
	(Level 1)		(Level 2)		(Level 3)		Total
December 31, 2020
Cash equivalents:
Money market mutual funds	$	—	$	96,307	$	—	$	96,307
Total cash equivalents		—		96,307		—		96,307
Marketable securities:
U.S. government and agency securities		—		12,804		—		12,804
Certificates of deposit		—		1,990		—		1,990
Corporate bonds		—		166,292		—		166,292
Municipal securities		—		3,037		—		3,037
Total marketable securities		—		184,123		—		184,123
Total cash equivalents and marketable securities	$	—	$	280,430	$	—	$	280,430

Management estimates that the carrying amounts of its current accounts receivable, other current assets, accounts payable, accrued expenses and other current liabilities approximate fair value due to the short-term nature of those instruments. Accounts receivable which contain non-current portions are recorded at their present values using a discount rate that is based on prevailing market rates and the credit profile of the licensee on the date the amounts are initially recorded. Management does not believe there have been any significant changes in market conditions or credit quality that would cause the discount rates initially used to be materially different from those that would be used as of December 31, 2021 to determine the present value of the receivables. Accordingly, management estimates that the carrying value of its non-current accounts receivable approximates the fair value of those instruments. Management estimates that the carrying value of the liability related to the sale of future royalties approximates fair value. As discussed in Note 7, the carrying value of the liability related to the sale of future royalties is based on the Company’s estimate of future royalty payments expected to be paid to HCR over the life of the arrangement, which are considered Level 3 inputs.

Non-marketable Equity Securities

Non-marketable equity securities are measured at cost less impairment, adjusted for observable price changes for identical or similar investments of the same issuer. As of December 31, 2021, the Company did not hold any non-marketable equity securities. As of December 31, 2020, non-marketable equity securities had a carrying value of $1.1 million and were included in other assets on the consolidated balance sheet. The Company did not identify any observable price changes or changes in circumstances that would have had an adverse effect on the fair value of the securities as of December 31, 2020. No remeasurements or impairment losses were recorded on non-marketable equity securities during the years ended December 31, 2021, 2020 and 2019.

The Company’s non-marketable equity securities as of December 31, 2020 consisted solely of equity securities of Corlieve Therapeutics SAS (Corlieve), which were acquired in June 2020 as consideration under a license and collaboration agreement with Corlieve. In July 2021, Corlieve was acquired by uniQure N.V. (uniQure). In exchange for its ownership in Corlieve, the Company received sales proceeds of €4.8 million ($5.6 million) from uniQure and is entitled to receive additional proceeds of €0.5 million ($0.6 million as of December 31, 2021) by July 2022. The Company recorded a realized gain of $5.2 million during the year ended December 31, 2021 as a result of the acquisition of its Corlieve securities by uniQure, which is included in investment income in the consolidated statements of operations and comprehensive income (loss). In connection with the acquisition, the Company is also eligible to receive payments of up to €37.1 million ($42.1 million as of December 31, 2021) from uniQure contingent upon the achievement of various development and regulatory milestones, none of which have been recognized in the consolidated financial statements as of December 31, 2021. Proceeds contingent upon the achievement of these milestones will be recognized as investment income in the period in which any uncertainty regarding realization is substantially resolved, which may not occur until the achievement of the underlying milestones. It is at least reasonably possible that some or all of the proceeds contingent upon these milestones will not be realized by the Company.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Property and Equipment, Net

12 Months Ended

Dec. 31, 2021

Property Plant And Equipment [Abstract]

Property and Equipment, Net

5. Property and Equipment, Net

Property and equipment, net consists of the following (in thousands):

	As of December 31,
	2021			2020
Laboratory and manufacturing equipment	$	56,976		$	26,306
Computer equipment and software		4,268			3,764
Furniture and fixtures		6,804			4,114
Leasehold improvements		92,535			44,957
Total property and equipment		160,583			79,141
Accumulated depreciation and amortization		(29,036	)		(22,674	)
Property and equipment, net	$	131,547		$	56,467

During the years ended December 31, 2021, 2020 and 2019, the Company recorded depreciation and amortization expense of $9.6 million, $8.4 million and $7.2 million, respectively.

Leases

12 Months Ended

Dec. 31, 2021

Leases [Abstract]

Leases

6. Leases

9804 Medical Center Drive

In November 2018, the Company entered into an operating lease, as amended from time to time, for approximately 186,000 square feet of office, laboratory and manufacturing facilities at a new building to be constructed at 9804 Medical Center Drive in Rockville, Maryland (the 9804 Medical Center Drive Lease), which will serve as the Company’s corporate, research and manufacturing headquarters. The initial construction of the building was performed by the landlord and the lease commenced in September 2020 upon delivery of the leased premises to the Company to make additional improvements to the building. Monthly payments under the lease began in September 2021 and escalate annually in accordance with the lease agreement. The lease expires in September 2036, subject to extension and termination options held by the Company. The Company has the option to extend the term of the lease for up to 10 additional years and the option to terminate the lease, with payment of an early termination fee, after 12 years from the delivery of the leased premises to the Company. As of December 31, 2021, the Company’s extension and termination options under the 9804 Medical Center Drive Lease have been excluded from the measurement of the right-of-use assets and lease liabilities as they were not reasonably certain of exercise. As required by the lease agreement, the Company has provided the landlord with an irrevocable letter of credit of $1.1 million which the landlord may draw upon in the event of any uncured default by the Company under the terms of the lease.

Pursuant to the 9804 Medical Center Drive Lease, the Company received a $19.5 million tenant improvement allowance from the landlord to perform improvements to the leased premises. The tenant improvement allowance has been recorded as a reduction of the right-of-use assets for the lease and is amortized on a straight-line basis as a reduction of lease expense over the term of the lease. As of December 31, 2021, the Company had unreimbursed amounts remaining under the tenant improvement allowance of $1.5 million, which were deemed in-substance lease payments and recorded as a reduction of the lease liability. The Company began occupation of a portion of the facility in 2021, while the buildout of the remaining portion of the building, including the manufacturing facility, is expected to be completed in the first half of 2022. As of December 31, 2021, the Company had recorded property and equipment at cost of $113.2 million related to the buildout at 9804 Medical Center Drive, of which $41.2 million was placed in service upon the initial occupation of the building in 2021 and $72.0 million, primarily related to the manufacturing facility, has not yet been placed in service.

The Company recorded the right-of-use assets and lease liabilities related to the 9804 Medical Center Drive Lease upon its commencement in September 2020. As of December 31, 2021, the Company had recorded right-of-use assets of $48.3 million and lease liabilities of $72.5 million related to the 9804 Medical Center Drive Lease.

9712 Medical Center Drive

In March 2015, the Company entered into an operating lease for office space at 9712 Medical Center Drive in Rockville, Maryland (the 9712 Medical Center Drive Lease). The lease term commenced in April 2015, and monthly payments under the lease began in October 2015 and escalate annually in accordance with the lease agreement.

The 9712 Medical Center Drive Lease has been amended from time to time to include additional office and laboratory space at an adjacent building located at 9714 Medical Center Drive and extend the term of the lease. In October 2020, the 9712 Medical Center Drive Lease was amended to extend the lease term from September 2021 to February 2027, subject to extension options held by the Company. The October 2020 amendment resulted in a $7.2 million increase in the right-of-use assets and lease liabilities under the 9712 Medical Center Drive Lease. The Company has an option to extend the term of the lease for three additional years, as well as an option to extend the lease term to be coterminous with the 9804 Medical Center Drive Lease, which expires in September 2036. As of December 31, 2021, the Company’s extension options under the 9712 Medical Center Drive Lease have been excluded from the measurement of the right-of-use assets and lease liabilities as they were not reasonably certain of exercise. The Company received a $0.4 million tenant improvement allowance from the landlord which has been recorded as a reduction of the right-of-use assets for the lease and is amortized on a straight-line basis as a reduction of lease expense over the term of the lease.

400 Madison Avenue

In May 2016, the Company entered into an operating lease for office space at 400 Madison Avenue in New York, New York (the 400 Madison Lease). The lease term commenced in July 2016, and monthly payments under the lease began in October 2016 and escalate annually in accordance with the lease agreement. In May 2019, the 400 Madison Lease was amended to include additional office space and extend the lease term from October 2020 to April 2027. The May 2019 amendment resulted in a $5.2 million increase in the right-of-use assets and lease liabilities under the 400 Madison Lease. The Company received a $0.7 million tenant improvement allowance from the landlord which has been recorded as a reduction of the right-of-use assets for the lease and is amortized on a straight-line basis as a reduction of lease expense over the term of the lease. As required by the lease agreement, the Company has provided the landlord with an irrevocable letter of credit of $0.2 million which the landlord may draw upon in the event of any uncured default by the Company under the terms of the lease.

9600 Blackwell Road

In November 2020, the Company exercised its termination option under the operating lease for its former corporate headquarters at 9600 Blackwell Road in Rockville, Maryland (the 9600 Blackwell Road Lease). Upon exercise of the termination option, the Company was obligated to pay an early termination fee of $0.4 million and the lease term was reduced from September 2023 to September 2021. The exercise of the termination option in November 2020 resulted in a $0.7 million decrease in the right-of-use assets and lease liabilities under the 9600 Blackwell Road Lease, and the lease was terminated upon its expiration in September 2021.

Other Leases

The Company leases additional laboratory and other equipment under operating leases with various expiration dates through 2028, including leases which have been executed but have not yet commenced.

Operating Lease Information

All of the Company’s leases are classified as operating leases. The following table summarizes the Company’s lease costs and supplemental cash flow information related to its operating leases (in thousands):

	Years Ended December 31,
	2021			2020			2019
Operating lease cost	$	9,729		$	5,246		$	3,040
Variable lease cost		2,348			1,104			666
Total lease cost	$	12,077		$	6,350		$	3,706

Cash paid (received) for amounts included in operating lease liabilities	$	(6,765	)	$	(678	)	$	2,724
Right-of-use assets acquired through operating lease liabilities	$	1,955		$	56,956		$	5,114

Cash received for amounts included in operating lease liabilities for the years ended December 31, 2021 and 2020 includes $11.4 million and $5.0 million, respectively, received by the Company during the period under its tenant improvement allowances, which were deemed in-substance lease payments and included in the calculation of the lease liability. Right-of-use assets acquired through operating lease liabilities for the years ended December 31, 2020 and 2019 include additions and reductions to right-of-use assets resulting from lease modifications and changes in lease term. Short-term lease expense for the years ended December 31, 2021, 2020 and 2019 was not material and is included in operating lease cost in the table above. Variable lease cost under the Company’s operating leases includes items such as common area maintenance, utilities, taxes and other charges.

The weighted-average remaining lease term and weighted-average discount rate of the Company’s operating leases were as follows:

	As of December 31,
	2021			2020
Weighted-average remaining lease term (years)		13.2			13.7
Weighted-average discount rate		5.6	%		5.6	%

The following table presents a reconciliation of the undiscounted future minimum lease payments remaining under the Company’s operating leases to the amounts reported as operating lease liabilities on the consolidated balance sheet as of December 31, 2021 (in thousands):

	As of
	December 31, 2021
Undiscounted future minimum lease payments:
2022	$	6,556
2023		9,163
2024		10,224
2025		10,383
2026		10,388
Thereafter		83,050
Total undiscounted future minimum lease payments	$	129,764
Amount representing imputed interest		(41,619	)
Tenant improvement allowance not yet received		(1,464	)
Total operating lease liabilities		86,681
Current portion of operating lease liabilities		(1,752	)
Operating lease liabilities, non-current	$	84,929

The table above excludes future minimum lease payments for leases which were executed but had not yet commenced as of December 31, 2021, the total of which were not material.

Liability Related to Sale of Future Royalties

12 Months Ended

Dec. 31, 2021

7. Liability Related to Sale of Future Royalties

In December 2020, the Company entered into a royalty purchase agreement (the Royalty Purchase Agreement) with HCR. Under the agreement, HCR purchased the Company’s rights to a capped amount of Zolgensma royalty payments under the Company’s license agreement with Novartis Gene Therapies, including $4.0 million of royalty payments received by the Company in the fourth quarter of 2020 (the Pledged Royalties). In consideration for these rights, HCR paid the Company $200.0 million (the Purchase Price), less $4.0 million representing the payment of the Pledged Royalties to HCR. Beginning upon the effective date of the agreement, Zolgensma royalty payments, up to a specified threshold, will be paid to HCR, net of upstream royalties payable by the Company to certain licensors in accordance with existing license agreements.

Pursuant to the Royalty Purchase Agreement, the total amount of royalty payments to be received by HCR under the agreement is subject to an increasing cap (the Cap Amount) equal to (i) $260.0 million applicable for the period from the effective date of the agreement through November 7, 2024, and (ii) $300.0 million applicable for the period from November 8, 2024 through the effective date of termination of the license agreement with Novartis Gene Therapies. If, on or prior to the defined dates for each Cap Amount, the total amount of royalty payments received by HCR equals or exceeds the Cap Amount applicable to such date, the Royalty Purchase Agreement will automatically terminate and all rights to the Zolgensma royalty payments will revert back to the Company. The Company has no obligation to repay any amounts to HCR if total future Zolgensma royalty payments are not sufficient to achieve the applicable Cap Amount prior to the termination of the license agreement with Novartis Gene Therapies.

The Company has a call option to repurchase its rights to the purchased royalties from HCR for a repurchase price equal to, as of the option exercise date, $300.0 million minus the total amount of royalty payments received by HCR; provided, however, that with respect to a call option exercised on or before November 7, 2024, in the event that the then applicable Cap Amount minus the total amount of royalty payments received by HCR is less than $1.0 million, the repurchase price shall equal such difference.

The proceeds received from HCR of $196.0 million were recorded as a liability, net of transaction costs of $3.5 million, which is amortized over the estimated life of the arrangement using the effective interest method. In order to determine the amortization of the liability, the Company is required to estimate the total amount of future royalty payments to be received by HCR, subject to the Cap Amount, over the life of the arrangement. The total amount of royalty payments received by HCR under the agreement, less the net proceeds received by the Company of $192.5 million, is recorded as interest expense over the life of the arrangement using the effective interest method. Due to its continuing involvement in the underlying license agreement with Novartis Gene Therapies, the Company continues to recognize royalty revenue on net sales of Zolgensma and records the royalty payments to HCR as a reduction of the liability when paid. As such payments are made to HCR, the balance of the liability will be effectively repaid over the life of the Royalty Purchase Agreement.

The Company estimates the effective interest rate used to record interest expense under the Royalty Purchase Agreement based on its estimate of future royalty payments to be received by HCR. As of December 31, 2021, the estimated effective interest rate under the agreement was 15.1%. Over the life of the arrangement, the actual effective interest rate will be affected by the amount and timing of the royalty payments received by HCR and changes in the Company’s forecasted royalties. At each reporting date, the Company reassesses its estimate of total future royalty payments to be received by HCR at the applicable Cap Amount, and prospectively adjusts the effective interest rate and amortization of the liability as necessary.

The following table presents the changes in the liability related to the sale of future royalties under the Royalty Purchase Agreement with HCR (in thousands):

	Liability Related to
	Sale of Future Royalties
Proceeds from sale of future royalties in December 2020	$	196,000
Deferred transaction costs		(3,473	)
Interest expense recognized		771
Balance at December 31, 2020		193,298
Zolgensma royalties paid to HCR		(48,226	)
Interest expense recognized		26,277
Balance at December 31, 2021		171,349
Current portion of liability related to sale of future royalties		(37,889	)
Liability related to sale of future royalties, non-current	$	133,460

Commitments and Contingencies

12 Months Ended

Dec. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

8. Commitments and Contingencies

In-licensed Technology

The Company in-licenses intellectual property from third parties for technology and know-how used in its product candidates and development programs, some of which is further sublicensed to NAV Technology Licensees and collaboration partners. In-licenses may require the Company to make future payments relating to sublicense fees, milestone fees and royalties on future sales of licensed products. Additionally, the Company may be responsible for the cost of the maintenance of the intellectual property as incurred by its licensors. Up-front fees to obtain licensed technology are recorded as research and development expenses if the technology has no alternative future use. Sublicense fees are based on a specified percentage of license fees earned by the Company as a result of sublicensing the technology to third parties and are recorded as cost of revenues. Milestone fees are recorded as cost of revenues if the underlying milestone is achieved by a licensee, or as research and development expense if the underlying milestone is achieved by the Company as a result of the development of its product candidates and the technology has no alternative future use. Royalties due to licensors on sales of licensed products, including sales by NAV Technology Licensees, are recorded as cost of revenues. Patent maintenance costs are recorded as general and administrative expenses.

Please refer to Note 10 for information on licenses granted by the Company and collaboration agreements with third parties.

The Trustees of the University of Pennsylvania

In February 2009, the Company entered into a license agreement, which has been amended from time to time, with The Trustees of the University of Pennsylvania (together with the University of Pennsylvania, Penn) for exclusive, worldwide rights to certain patents owned by Penn underlying the Company’s NAV Technology Platform, as well as exclusive rights to certain data, results and other information. Pursuant to the license agreement, the Company is obligated to pay Penn royalties on net sales of licensed products and sublicense fees. Additionally, the Company is obligated to reimburse Penn for certain costs incurred related to the maintenance of the licensed patents.

In April 2019, the Company amended its license from Penn to include exclusive license rights to certain patent rights and know-how, including research data and other information, relating to the treatment of late-infantile neuronal ceroid lipofuscinosis type 2 (CLN2) disease. In consideration for the additional licensed rights, and in addition to any consideration owed under the license prior to the amendment, the Company paid Penn an up-front fee and is obligated to pay milestone fees of up to $20.5 million upon the achievement of various development and sales-based milestones and additional royalties on net sales of licensed products for the treatment of CLN2 disease, none of which have been achieved or deemed probable of achievement as of December 31, 2021. Additionally, the amendment modified the percentage of sublicense fees the Company is obligated to pay Penn on amounts received by the Company from third parties for the sublicensing of the licensed rights for the treatment of CLN2 disease.

Expenses incurred by the Company related to the license from Penn were recorded as follows (in thousands):

	Years Ended December 31,
	2021		2020		2019
Cost of revenues	$	8,046	$	39	$	—
Research and development		—		—		200
General and administrative		706		821		905
	$	8,752	$	860	$	1,105

As of December 31, 2021 and 2020, the Company had recorded $8.2 million and $0.1 million, respectively, in expenses payable to Penn under the license agreement, which are included in accounts payable, accrued expenses and other current liabilities and other liabilities on the consolidated balance sheets.

GlaxoSmithKline LLC

In March 2009, the Company entered into a license agreement, which was amended in April 2009, with GlaxoSmithKline LLC (GSK) for exclusive, worldwide rights to certain patents underlying the Company’s NAV Technology Platform which are owned by Penn and exclusively licensed to GSK. Pursuant to the license agreement, the Company is obligated to pay GSK royalties on net sales of licensed products and sublicense fees. Additionally, the Company is obligated to reimburse GSK for certain costs incurred related to the maintenance of the licensed patents. The Company was also obligated to pay $1.5 million to GSK upon the achievement of various milestones, all of which have been achieved and paid as of December 31, 2021.

Expenses incurred by the Company related to the license from GSK were recorded as follows (in thousands):

	Years Ended December 31,
	2021		2020		2019
Cost of revenues:
Royalties on net sales of Zolgensma	$	43,161	$	26,278	$	5,822
Other cost of revenues		626		9,398		2,419
Total cost of revenues		43,787		35,676		8,241
General and administrative		889		1,046		928
	$	44,676	$	36,722	$	9,169

As of December 31, 2021 and 2020, the Company had recorded $16.3 million and $13.1 million, respectively, in expenses payable to GSK under the license agreement, which are included in accounts payable, accrued expenses and other current liabilities and other liabilities on the consolidated balance sheets.

Clearside Biomedical, Inc.

In August 2019, the Company entered into an option and license agreement with Clearside Biomedical, Inc. (Clearside) pursuant to which the Company was granted an option to exclusively license the worldwide rights to certain patents related to Clearside’s proprietary, in-office SCS Microinjector™ for the delivery of RGX-314 to the suprachoroidal space to treat wet age-related macular degeneration (wet AMD), diabetic retinopathy (DR) and other diseases. The Company exercised its license option in October 2019, resulting in a payment of $1.6 million to Clearside which was recognized as research and development expense upon exercise. Additionally, the Company is obligated to pay milestone fees of up to $136.0 million upon the achievement of various development and sales-based milestones, as well as royalties on net sales of licensed products using the SCS Microinjector. Clearside is responsible for supplying the SCS Microinjector to the Company to support all preclinical, clinical and commercial needs. From the inception of the agreement through December 31, 2021, the Company had incurred $3.0 million for development milestones achieved, or deemed probable of achievement, under the agreement.

Other Licenses

In November 2014, the Company entered into a license agreement, which has been amended from time to time, with Regents of the University of Minnesota (Minnesota), for an exclusive license under Minnesota’s interest in certain patent rights which are co-owned by Minnesota and the Company to commercialize products covered by the licensed patent rights in any country or territory in which a licensed patent has been issued and is unexpired, or a licensed patent application is pending. Pursuant to the license agreement, the Company is obligated to pay Minnesota annual maintenance fees, royalties on net sales, sublicense fees and fees upon the achievement of various milestones. Additionally, the Company is obligated to pay for certain costs incurred related to the maintenance of the licensed patents.

In August 2018, the Company entered into a license agreement with Emory University (Emory) for an exclusive license under Emory’s interest in certain patent rights which are co-owned by Emory and the Company to commercialize products covered by the licensed patent rights in any country or territory. Pursuant to the license agreement, the Company is obligated to reimburse Emory for patent prosecution and maintenance expenses and pay Emory annual maintenance fees under certain circumstances, royalties on net sales, sublicense fees and fees upon the achievement of various milestones for the first licensed product.

Other Funding Commitments

In the normal course of business, the Company enters into agreements with contract research organizations, contract manufacturing organizations and other third parties for services to be provided to the Company. Generally, these agreements provide for termination upon notice, with specified amounts due upon termination based on the timing of termination and the terms of the agreement. The actual amounts and timing of payments under these agreements are uncertain and contingent upon the initiation and completion of services to be provided to the Company.

Guarantees and Indemnifications

In the normal course of business, the Company enters into agreements that contain a variety of representations and provide for general indemnification. The Company’s potential exposure under these agreements is unknown because it involves claims that may be made against the Company in the future. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. As of December 31, 2021 and 2020, the Company did not have any material indemnification claims that were probable or reasonably possible and consequently had not recorded any related liabilities.

Capitalization

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Capitalization

9. Capitalization

As of December 31, 2021 and 2020, the authorized capital stock of the Company included 100,000,000 shares of common stock, par value $0.0001 per share, and 10,000,000 shares of preferred stock, par value $0.0001 per share. The Company’s restated certificate of incorporation and bylaws contain the rights, preferences and privileges of the Company’s stockholders and their respective shares.

In January 2021, the Company completed a public offering of 4,899,000 shares of its common stock (inclusive of 639,000 shares pursuant to the full exercise by the underwriters of their option to purchase additional shares) at a price of $47.00 per share. The aggregate net proceeds received by the Company from the offering, inclusive of the underwriters’ option exercise, were $216.1 million, net of underwriting discounts and commissions and offering expenses payable by the Company.

Shares of common stock reserved for future issuance were as follows (in thousands):

	As of December 31,
	2021		2020
Reserved for issuance under equity incentive plans		9,755		8,659
Reserved for issuance under employee stock purchase plan		769		448
		10,524		9,107

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

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-Name Accounting Standards Codification
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-Section 50
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section 50
-Paragraph 18
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496189-112644

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 16
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496180-112644

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

License and Collaboration Agreements

12 Months Ended

Dec. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

License and Collaboration Agreements

10. License and Collaboration Agreements

Please refer to Note 8 for information on license agreements for technology in-licensed by the Company from third parties.

License and Royalty Revenue

As of December 31, 2021, the Company’s NAV Technology Platform was being applied by NAV Technology Licensees in one commercially available product, Zolgensma, and in the development of a number of licensed products. Additionally, the Company has licensed intellectual property rights to collaborators for the joint development of certain product candidates. Consideration to the Company under its license agreements may include: (i) up-front and annual fees, (ii) milestone payments based on the achievement of certain development and sales-based milestones, (iii) sublicense fees, (iv) royalties on sales of licensed products and (v) other consideration payable upon optional goods and services purchased by licensees. Sublicense fees vary by license and range from a mid-single digit percentage to a low-double digit percentage of license fees received by licensees as a result of sublicenses. Royalties on net sales of commercialized products vary by license and range from a mid-single digit percentage to a low double-digit percentage of net sales by licensees.

License and royalty revenue consisted of the following (in thousands):

	Years Ended December 31,
	2021		2020		2019
AbbVie collaboration and license agreement	$	370,000	$	—	$	—
Royalties on net sales of Zolgensma		94,978		61,631		20,829
Achievement of sales-based milestone for Zolgensma		—		80,000		—
Other license and royalty revenue		5,369		12,936		14,404
Total license and royalty revenue	$	470,347	$	154,567	$	35,233

Development milestone payments are evaluated each reporting period and are only included in the transaction price of each license and recognized as license revenue to the extent the milestones are considered probable of achievement. Sales-based milestones are excluded from the transaction price of each license agreement and recognized as royalty revenue in the period of achievement. As

of December 31, 2021, the Company’s license agreements, excluding additional licenses that could be granted upon the exercise of options by licensees, contained unachieved milestones which could result in aggregate milestone payments to the Company of up to $1.58 billion, including (i) $538.3 million upon the commencement of various stages of clinical trials, (ii) $21.0 million upon the submission of regulatory approval filings, (iii) $141.0 million upon the approval of commercial products by regulatory agencies and (iv) $877.0 million upon the achievement of specified sales targets for licensed products, including milestones payable upon first commercial sales of licensed products. To the extent the milestone payments are realized by the Company, the Company will be obligated to pay sublicense fees to licensors based on a specified percentage of the fees earned by the Company. The achievement of these milestones is highly dependent on the successful development and commercialization of licensed products and it is at least reasonably possible that some or all of the milestone fees will not be realized by the Company.

Changes in Accounts Receivable, Contract Assets and Deferred Revenue

The following table presents changes in the balances of the Company’s net accounts receivable, contract assets and deferred revenue, as well as other information regarding revenue recognized, during the periods presented (in thousands):

	Years Ended December 31,
	2021			2020			2019
Accounts receivable, net, current and non-current:
Balance, beginning of period	$	46,266		$	42,303		$	31,599
Additions		472,347			158,682			39,203
Deductions		(483,912	)		(154,719	)		(28,499	)
Balance, end of period	$	34,701		$	46,266		$	42,303

Contract assets:
Balance, beginning of period	$	350		$	—		$	750
Additions		1,074			350			1,000
Deductions		(350	)		—			(1,750	)
Balance, end of period	$	1,074		$	350		$	—

Deferred revenue, current and non-current:
Balance, beginning of period	$	4,232		$	3,333		$	3,933
Additions		—			1,124			—
Deductions		(899	)		(225	)		(600	)
Balance, end of period	$	3,333		$	4,232		$	3,333

Revenue recognized during the period from:
Amounts included in deferred revenue at beginning of period	$	390		$	—		$	600
Performance obligations satisfied in previous periods	$	98,575		$	146,772		$	26,689

Additions to accounts receivable during the periods presented consisted primarily of royalties on net sales of Zolgensma, new licenses granted by the Company, the achievement of milestones by licensees, interest income recognized and decreases in the allowance for credit losses during the period. Deductions to accounts receivable during the periods presented consisted primarily of amounts collected from licensees and increases in the allowance for credit losses during the period. Additions to accounts receivable during the year ended December 31, 2021 include $370.0 million billed to AbbVie Global Enterprises Ltd. under the collaboration and license agreement which became effective in November 2021. Additions to accounts receivable during the year ended December 31, 2020 include $80.0 million billed to Novartis Gene Therapies upon the achievement of a sales-based milestone for net sales of Zolgensma in the third quarter of 2020.

Additions to contract assets during the periods presented consisted of development milestones deemed probable of achievement by licensees during the period and revenue recognized from research and development services performed by the Company for which payment by the licensee is not unconditional. Deductions to contract assets during the periods presented consisted of the achievement of development milestones by licensees and billing of the associated milestone payments by the Company. Contract assets as of December 31, 2021 and 2020 are included in other current assets on the consolidated balance sheets.

As of December 31, 2021, the Company had recorded deferred revenue of $3.3 million which represents consideration received from licensees for performance obligations that have not yet been satisfied by the Company. Unsatisfied performance obligations consisted of (i) options granted to licensees that provide material rights to the licensee to acquire additional licenses from the Company, which will be satisfied upon the exercise or expiration of the options and (ii) research and development services to be performed by the Company related to licensed products, which will be satisfied as the research and development services are performed.

Revenue recognized from performance obligations satisfied in previous periods was primarily attributable to Zolgensma royalty revenues, the achievement of a sales-based milestone for net sales of Zolgensma, sublicense fees earned from licensees and changes in the transaction prices of the Company’s license agreements. Changes in transaction prices were primarily attributable to development milestones achieved or deemed probable of achievement during the periods, which were previously not considered probable of achievement.

Accounts Receivable, Contract Assets and the Allowance for Credit Losses

Accounts receivable, net consisted of the following (in thousands):

	As of December 31,
	2021			2020
Current accounts receivable:
Billed to customers	$	365		$	30,573
Unbilled		32,074			20,104
Allowance for credit losses		—			(7,678	)
Current accounts receivable, net		32,439			42,999
Non-current accounts receivable:
Unbilled		6,020			3,267
Allowance for credit losses		(3,758	)		—
Non-current accounts receivable, net		2,262			3,267
Total accounts receivable, net	$	34,701		$	46,266

The following table presents the changes in the allowance for credit losses related to accounts receivable and contract assets for the years ended December 31, 2021 and 2020 (in thousands):

	Allowance for Credit Losses
	Accounts Receivable			Contract Assets
Balance at December 31, 2019	$	—		$	—
Provision for credit losses (recoveries)		7,678			—
Write-offs		—			—
Balance at December 31, 2020		7,678			—
Provision for credit losses (recoveries)		(2,569	)		—
Changes in present value discount of receivables		(1,243	)		—
Write-offs		(108	)		—
Balance at December 31, 2021	$	3,758		$	—

The Company’s allowance for credit losses as of December 31, 2021 and 2020 was related solely to accounts receivable from Abeona. Please refer to the section below, Abeona Therapeutics Inc., for further information regarding amounts due from Abeona and the associated allowance for credit losses. The Company’s provision for credit losses (recoveries) for the years ended December 31, 2021 and 2020 was $(2.6) million and $7.7 million, respectively, and was related solely to changes in estimates regarding the collectability of the accounts receivable due from Abeona. No allowance for credit losses was recorded as of December 31, 2019, and no provision for credit losses (recoveries) was recorded for the year ended December 31, 2019.

Novartis Gene Therapies, Inc.

In March 2014, the Company entered into an exclusive license agreement (as amended, the March 2014 License) with Novartis Gene Therapies (formerly AveXis, Inc.). Under the March 2014 License, the Company granted Novartis Gene Therapies an exclusive, worldwide commercial license, with rights to sublicense, to the NAV Technology Platform, as well as other certain rights, for the treatment of SMA in humans by in vivo gene therapy.

In consideration for the rights granted under the license, Novartis Gene Therapies paid the Company (i) an up-front fee of $2.0 million upon the execution of the agreement in 2014, (ii) license fees totaling $180.0 million upon the amendment of the agreement in January 2018 and the subsequent acquisition of AveXis, Inc. (now Novartis Gene Therapies) by Novartis in May 2018, (iii) total cumulative payments of $12.3 million upon the achievement of various development milestones, and (iv) a sales-based milestone payment of $80.0 million upon the achievement of $1.0 billion in cumulative net sales of Zolgensma. In addition to the consideration above, Novartis Gene Therapies is obligated to pay to the Company fixed annual fees, royalties on net sales of licensed products and a percentage of any sublicense fees received by Novartis Gene Therapies from sublicensees for the licensed intellectual property rights. Royalties are payable by Novartis Gene Therapies at a mid-single to low double-digit percentage of net sales of licensed products using the NAV AAV9 vector, and a low double-digit percentage of net sales of licensed products using a licensed vector other than NAV AAV9, and are subject to reduction in specified circumstances.

Novartis Gene Therapies launched commercial sales of Zolgensma, a licensed product under the March 2014 License, in the second quarter of 2019, upon which the Company began recognizing royalty revenue on net sales of the licensed product. Pursuant to the license agreement, Novartis Gene Therapies was obligated to pay a sales-based milestone fee of $80.0 million to the Company upon the achievement of $1.0 billion in cumulative net sales of licensed products. Novartis Gene Therapies achieved cumulative net sales of Zolgensma of $1.0 billion in the third quarter of 2020, upon which the Company recognized revenue of $80.0 million related to the sales-based milestone fee. Additionally, the Company recognized license revenue of $3.5 million and $3.5 million for the years ended December 31, 2020 and 2019, respectively, related to development milestones achieved during the periods which were previously considered not probable of achievement. As of December 31, 2020, all development and sales-based milestones under the March 2014 License had been achieved and associated milestone payments had been received from Novartis Gene Therapies.

The Company recognized the following amounts under the March 2014 License with Novartis Gene Therapies (in thousands):

	Years Ended December 31,
	2021		2020		2019
Royalties on net sales of Zolgensma	$	94,978	$	61,631	$	20,829
Achievement of sales-based milestone for Zolgensma		—		80,000		—
Other license revenue		—		3,500		3,500
Total license and royalty revenue	$	94,978	$	145,131	$	24,329

Interest income from licensing	$	22	$	26	$	29

As of December 31, 2021 and 2020, the Company had recorded total accounts receivable of $26.6 million and $19.6 million, respectively, from Novartis Gene Therapies under the March 2014 License, which consisted primarily of Zolgensma royalties receivable. Zolgensma royalties receivable recorded as of December 31, 2021 included $12.8 million expected to be paid to HCR in accordance with the Royalty Purchase Agreement discussed in Note 7.

Abeona Therapeutics Inc.

In November 2018, the Company entered into a license agreement with Abeona (as amended, the November 2018 License) for the treatment of various diseases using the NAV Technology Platform. Pursuant to the November 2018 License, Abeona was required to pay a license fee of $8.0 million to the Company no later than April 1, 2020. Abeona failed to make this payment, and in April 2020, the Company delivered to Abeona a notice of its breach of the license agreement and written demand for payment. Upon expiration of the applicable cure period in May 2020, the license agreement terminated. As a result of the termination, Abeona was required to pay an additional $20.0 million license fee to the Company within 15 days of the termination date, which otherwise would have been due to the Company in November 2020. Unpaid balances due under the November 2018 License accrue interest at 1.5% per month.

In May 2020, after the termination of the November 2018 License, Abeona filed a claim in arbitration alleging that the Company had breached certain responsibilities to communicate with Abeona regarding the Company’s prosecution of licensed patents under the November 2018 License. The Company disputed Abeona’s claim and filed a counterclaim in arbitration demanding payment of the $28.0 million of unpaid fees from Abeona, plus accrued interest. A binding arbitration was held in March 2021 and the arbitration tribunal issued its ruling in July 2021, which denied Abeona’s claim and upheld the Company’s counterclaim. The arbitration tribunal’s ruling, which was subsequently amended to reflect a minor adjustment in the computation of accrued interest, awarded the Company a total of $33.6 million, which consisted of $28.0 million in damages and $5.6 million in accrued interest payable to the Company by Abeona.

Subsequent to the arbitration tribunal’s ruling in July 2021, Abeona filed an additional claim in a second arbitration to enforce a purported settlement relating to the unpaid fees, which the Company disputed. In November 2021, the Company and Abeona entered into a settlement agreement and mutual release (the Settlement Agreement) to resolve all arbitration and legal proceedings and mutually release each party from any and all claims under the November 2018 License. Pursuant to the Settlement Agreement, Abeona will pay the Company a total of $30.0 million as follows: (i) $20.0 million which was paid in November 2021, (ii) $5.0 million payable in November 2022, which is fully secured by an irrevocable standby letter of credit issued to the Company by a reputable U.S. financial institution, and (iii) $5.0 million payable on the earlier of the third anniversary of the Settlement Agreement in November 2024 or the closing of a specified type of transaction by Abeona.

As of December 31, 2020, the Company had recorded gross accounts receivable of $30.1 million from Abeona under the November 2018 License, which consisted of the $8.0 million fee due in April 2020, the $20.0 million fee due within 15 days of the termination of the license agreement in May 2020 and accrued interest on the outstanding balances. As a result of its assessment of credit risk, the Company recorded an allowance for credit loss of $7.7 million as of December 31, 2020 related to the accounts receivable due from Abeona. As of December 31, 2020, the Company had recognized interest income from licensing of $2.1 million related to the unpaid license fees from Abeona, which was included in the gross accounts receivable balance of $30.1 million. In accordance with its interest accrual policy, the Company ceased the recognition of interest income accrued under the license agreement subsequent to the establishment of the allowance for credit losses in the third quarter of 2020.

In accordance with the Settlement Agreement, the Company received a payment of $20.0 million from Abeona in November 2021. As of December 31, 2021, the Company had recorded gross accounts receivable of $8.8 million from Abeona under the Settlement Agreement, which consisted of current accounts receivable of $5.0 million for the payment due in November 2022, and non-current accounts receivable of $3.8 million for the present value of the $5.0 million payment due by November 2024. While the Company anticipates taking appropriate measures to enforce the full collection of amounts due from Abeona under the Settlement Agreement, the Company assessed the collectability of the accounts receivable from Abeona as it relates to credit risk. In performing this assessment, the Company evaluated Abeona’s credit profile and financial condition, as well its expectations regarding Abeona’s future cash flows and ability to satisfy the contractual obligations of the Settlement Agreement. As a result of its analysis, the Company recorded an allowance for credit losses of $3.8 million as of December 31, 2021 related to the non-current accounts receivable due from Abeona. The Company recorded a provision for credit losses (recoveries) of $(2.6) million and $7.7 million for the years ended December 31, 2021 and 2020, respectively, as a result of changes in estimates regarding the allowance during the periods. The present value discount of the non-current accounts receivable from Abeona is accreted as interest income from licensing through the contractual due date using the effective interest method. The Company has elected to record increases in the allowance for credit losses associated with the accretion of the present value discount of the receivable as a reduction of the associated interest income, resulting in no interest income recognized during the period related to the accretion of the present value discount on the non-current receivable from Abeona.

Collaboration Agreements

AbbVie Global Enterprises Ltd.

In September 2021, the Company entered into a collaboration and license agreement with AbbVie Global Enterprises Ltd. (AbbVie), a subsidiary of AbbVie Inc., to jointly develop and commercialize RGX-314, the Company’s product candidate for the treatment of wet AMD, DR and other chronic retinal diseases (the AbbVie Collaboration Agreement). The AbbVie Collaboration Agreement became effective in November 2021.

Pursuant to the AbbVie Collaboration Agreement, the Company granted AbbVie a co-exclusive license to develop and commercialize RGX-314 in the United States and an exclusive license to develop and commercialize RGX-314 outside the United States. The Company and AbbVie will collaborate to develop RGX-314 in the United States, and AbbVie will be responsible for the development of RGX-314 in specified markets outside the United States. Through December 31, 2022, the Company will be responsible for development expenses for certain ongoing trials of RGX-314 and the parties will share additional development expenses related to RGX-314. Beginning on January 1, 2023, AbbVie will be responsible for the majority of all RGX-314 development expenses.

The Company will lead the manufacturing of RGX-314 for clinical development and U.S. commercial supply, and AbbVie will lead the manufacturing of RGX-314 for commercial supply outside the United States. Manufacturing expenses will be allocated between the parties in accordance with the terms of the AbbVie Collaboration Agreement and supply agreements determined in accordance with the agreement. If requested by AbbVie, the Company will manufacture up to a specified portion RGX-314 for commercial supply outside the United States at a price specified in the agreement. AbbVie will lead the commercialization of RGX-314 globally, and the Company will participate in U.S. commercialization efforts as provided under a commercialization plan determined in accordance with the agreement. The Company and AbbVie will share equally in the net profits and net losses associated with the commercialization of RGX-314 in the United States. Outside the United States, AbbVie will be responsible, at its sole cost, for the commercialization of RGX-314.

In consideration for the rights granted under the AbbVie Collaboration Agreement, AbbVie paid the Company an up-front fee of $370.0 million upon the effective date of the agreement in November 2021, and is required to pay to the Company up to $1.38 billion upon the achievement of specified development and sales-based milestones, of which $562.5 million are based on development milestones and $820.0 million are sales-based milestones. AbbVie is also required to pay to the Company tiered royalties on net sales of RGX-314 outside the United States at percentages in the mid-teens to low twenties, subject to specified offsets and reductions.

The AbbVie Collaboration Agreement contains provisions for termination, including termination for convenience by AbbVie. Contemporaneously with entering into the AbbVie Collaboration Agreement in September 2021, the Company entered into a sublicense agreement with AbbVie (the AbbVie Sublicense Agreement) pursuant to which the Company granted AbbVie an exclusive sublicense to exploit licensed products in connection with the AbbVie Collaboration Agreement under specified patents licensed to the Company by Penn. The AbbVie Sublicense Agreement became effective contemporaneously with the AbbVie Collaboration Agreement in November 2021 and is coterminous with the AbbVie Collaboration Agreement.

The Company evaluated its various commitments under the AbbVie Collaboration Agreement and identified the following distinct units of account: (i) delivery of an intellectual property license for the rights to develop and commercialize RGX-314 globally, (ii) development, manufacturing and commercialization activities for RGX-314 in the United States, and (iii) manufacturing of commercial supply for sales of RGX-314 outside the United States, if requested by AbbVie. In determining the distinct units of account, the Company concluded that the license granted to AbbVie to develop and commercialize RGX-314 is distinct from the other goods and services promised under the agreement, as AbbVie can benefit from the license on a standalone basis and, based on the stage of development of RGX-314, the underlying licensed products and know-how are not expected to be significantly modified as a result of other goods and services promised under the agreement.

For each of the distinct units of account identified under the AbbVie Collaboration Agreement, the Company determined whether the transactions should be accounted for as a contract with a customer within the scope of Topic 606 or as a collaborative arrangement within the scope of Topic 808. The Company concluded that the units of account for the delivery of the functional intellectual property license and the manufacturing of commercial supply for sales of RGX-314 outside the United States should be accounted for as revenue under Topic 606, as AbbVie is deemed to be a customer for these transactions. The Company concluded that the unit of account for development, manufacturing and commercialization activities for RGX-314 in the United States should be accounted for as a collaborative arrangement under Topic 808, as these represent joint operating activities for which the Company and AbbVie are both active participants and exposed to significant risks and rewards dependent on the commercial success of such activities.

The Company applied the requirements of Topic 606 to the AbbVie Collaboration Agreement for the units of account in which AbbVie was deemed to be a customer. The Company determined that there is only one material performance obligation under the agreement for the delivery of the intellectual property license to develop and commercialize RGX-314 globally. The Company evaluated options granted to AbbVie under the agreement and determined that the options do not represent material rights, and therefore are not considered separate performance obligations under the current contract. Specifically, the Company concluded that the option granted to AbbVie to purchase commercial supply of RGX-314 from the Company for a portion of sales outside the United States does not convey a material right, as the option is not priced at an incremental discount to the standalone selling price of the underlying goods and services. Additionally, the Company identified various promises under the AbbVie Collaboration Agreement which were determined to be immaterial in the context of the contract and will not be accounted for as a separate performance obligations.

Upon the effective date of the agreement and as of December 31, 2021, the transaction price of the AbbVie Collaboration Agreement was $370.0 million, which consisted solely of the up-front payment in November 2021. The $370.0 million transaction price was fully recognized as revenue upon the delivery of the license to AbbVie in November 2021. Variable consideration under the AbbVie Collaboration Agreement, which has been excluded from the transaction price, includes $562.5 million in payments for development milestones that have not yet been achieved and were not considered probable of achievement. Additionally, the transaction price excludes sales-based milestone payments of $820.0 million and royalties on net sales of RGX-314 outside the United States. Development milestones will be added to the transaction price and recognized as revenue upon achievement, or if deemed probable of achievement. In accordance with the sale- or usage-based royalty exception under Topic 606, royalties on net sales and sales-based milestones will be recognized as revenue in the period the underlying sales occur or milestones are achieved.

The Company applied the requirements of Topic 808 to the AbbVie Collaboration Agreement for the units of account which were deemed to be a collaborative arrangement. Both the Company and AbbVie will perform various activities related to the development, manufacturing and commercialization of RGX-314 in the United States. Development costs are shared between the parties in accordance with the terms of the AbbVie Collaboration Agreement, and the parties will share equally in the net profits and losses derived from sales of RGX-314 in the United States. The Company accounts for payments to and from AbbVie for the sharing of development costs in accordance with its accounting policy for collaborative arrangements. Amounts owed to AbbVie for the Company’s share of development costs incurred by AbbVie are recorded as research and development expense in the period the costs are incurred. Amounts owed to the Company for AbbVie’s share of development costs incurred by the Company are recorded as a reduction of research and development expense in the period the costs are incurred. At the end of each reporting period, the Company records a net amount due to or from AbbVie as a result of the cost-sharing arrangement. As of December 31, 2021, the Company had recorded $5.9 million due from AbbVie for reimbursement of development costs under AbbVie Collaboration Agreement which is included in other current assets on the consolidated balance sheet.

The Company recognized the following amounts under the AbbVie Collaboration Agreement (in thousands):

	Year Ended
	December 31, 2021
License and royalty revenue	$	370,000
Reduction of research and development expense for costs reimbursable by AbbVie	$	5,866

Neurimmune AG

In July 2019, the Company entered into a collaboration and license agreement with Neurimmune AG (Neurimmune) pursuant to which the Company and Neurimmune will jointly develop and commercialize novel gene therapies using AAV vectors from the NAV Technology Platform to deliver human antibodies for chronic neurodegenerative diseases. The Company and Neurimmune will share all research and development costs for the first two years of the agreement, after which each party will have the option, on a target-by-target basis, to: (i) continue as a 50% partner in the collaboration; (ii) receive a phase-based worldwide royalty in lieu of continued development investment; or (iii) negotiate with the other party to lead the development and commercialization of the respective program. Unless the parties agree otherwise, upon the commercialization of any product candidates, if any, it is anticipated that profits and losses will be shared equally on a worldwide basis.

The Company determined that the collaboration and license agreement with Neurimmune is a collaborative arrangement within the scope of Topic 808, and that no unit of account under the arrangement should be accounted for as a transaction with a customer within the scope of Topic 606. The Company accounts for payments to and from Neurimmune for the sharing of development costs in accordance with its accounting policy for collaborative arrangements. Amounts owed to Neurimmune for the Company’s share of development costs incurred by Neurimmune are recorded as research and development expense in the period the costs are incurred. Amounts owed to the Company for Neurimmune’s share of development costs incurred by the Company are recorded as a reduction of research and development expense in the period the costs are incurred. At the end of each reporting period, the Company records a net amount due to or from Neurimmune as a result of the cost-sharing arrangement. As of December 31, 2021 and 2020, the Company had recorded $0.4 million and $0.3 million, respectively, due to Neurimmune for reimbursement of development costs under the collaboration and license agreement which is included in accrued expenses and other current liability on the consolidated balance sheets.

During the years ended December 31, 2021, 2020 and 2019, the Company recorded $0.2 million, $0.3 million and less than $0.1 million, respectively, in net cost reimbursement to Neurimmune for development activities under the collaboration and license agreement, which were recorded as research and development expenses.

Stock-based Compensation

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-based Compensation

11. Stock-based Compensation

In September 2014, the Board of Directors adopted the 2014 Stock Plan (the 2014 Plan). In June 2015, the Board of Directors adopted the 2015 Equity Incentive Plan (the 2015 Plan), which became effective upon the Company’s initial public offering in September 2015. The 2015 Plan replaced the 2014 Plan, and as of the effective date of the 2015 Plan, no further awards may be issued under the 2014 Plan. Any options or awards outstanding under the 2014 Plan as of the effective date of the 2015 Plan remained outstanding and effective. The number of authorized shares under the 2015 Plan automatically increases annually on the first business day of each fiscal year, by the lesser of (i) 4% of the total number of shares of common stock outstanding on December 31 of the prior year, or (ii) a number of common shares determined by the Board of Directors. As of December 31, 2021, the total number of shares of common stock authorized for issuance under the 2015 Plan and 2014 Plan was 13,911,954, of which 2,352,346 remained available for future grants under the 2015 Plan. In January 2022, the Board of Directors authorized an additional 1,713,246 shares to be issued under the 2015 Plan.

The 2014 Plan and 2015 Plan provide for the issuance of stock options, stock appreciation rights, restricted and unrestricted stock and unit awards, and performance cash awards to employees, members of the Board of Directors and consultants of the Company. Since the inception of the plans, the Company has issued only stock options and restricted stock units under the plans. Stock options under the 2014 Plan and 2015 Plan generally expire 10 years following the date of grant. Options typically vest over a four-year period, but vesting provisions can vary by award based on the discretion of the Board of Directors. Certain stock option awards granted by the Company may include performance conditions that must be achieved in order for vesting to occur. Stock options under the 2014 Plan and 2015 Plan have an exercise price at least equal to the estimated fair value of the Company’s common stock on the date of grant. Restricted stock units typically vest over a four-year period, but vesting provisions can vary by award based on the discretion of the Board of Directors. Upon vesting, restricted stock units are settled in common stock of the Company.

Shares of common stock underlying awards previously issued under the 2014 Plan and 2015 Plan which are reacquired by the Company, withheld by the Company in payment of the purchase price, exercise price or withholding taxes, expired, cancelled due to forfeiture or otherwise terminated other than by exercise or settlement, are added to the number of shares of common stock available for issuance under the 2015 Plan. Shares available for issuance under the 2015 Plan may be either authorized but unissued shares of the Company’s common stock or common stock reacquired by the Company and held in treasury. The 2015 Plan expires in June 2025, 10 years from the date it was adopted by the Board of Directors, unless earlier terminated.

Stock-based Compensation Expense

The Company’s stock-based compensation expense by award type was as follows (in thousands):

	Years Ended December 31,
	2021		2020		2019
Stock options	$	35,320	$	31,178	$	25,964
Restricted stock units		2,835		—		257
Employee stock purchase plan		653		771		633
	$	38,808	$	31,949	$	26,854

As of December 31, 2021, the Company had $67.9 million of unrecognized stock-based compensation expense related to stock options, restricted stock units and the 2015 Employee Stock Purchase Plan (the 2015 ESPP), which is expected to be recognized over a weighted-average period of 2.3 years.

The Company recorded aggregate stock-based compensation expense in the consolidated statements of operations and comprehensive income (loss) as follows (in thousands):

	Years Ended December 31,
	2021		2020		2019
Research and development	$	19,602	$	16,280	$	13,031
General and administrative		19,206		15,669		13,823
	$	38,808	$	31,949	$	26,854

Stock Options

The following table summarizes stock option activity under the 2014 Plan and 2015 Plan (in thousands, except per share data):

						Weighted-
						average
				Weighted-		Remaining
				average		Contractual		Aggregate
				Exercise		Life		Intrinsic
	Shares			Price		(Years)		Value (a)
Outstanding at December 31, 2020		6,361		$	31.21		7.2	$	101,356
Granted		1,437		$	43.04
Exercised		(404	)	$	11.46
Cancelled or forfeited		(268	)	$	45.98
Outstanding at December 31, 2021		7,126		$	34.16		6.8	$	41,128
Exercisable at December 31, 2021		4,566		$	29.62		5.9	$	40,607
Vested and expected to vest at December 31, 2021		7,126		$	34.16		6.8	$	41,128

(a)	The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of the common stock for the options that were in the money at the dates reported.

The weighted-average grant date fair value per share of options granted during the years ended December 31, 2021, 2020 and 2019 was $26.01, $23.82 and $31.19, respectively. During the years ended December 31, 2021, 2020 and 2019, the total number of stock options exercised was 404,263, 434,534 and 796,847, respectively, resulting in total proceeds of $4.3 million, $5.6 million and $7.1 million, respectively. The total intrinsic value of options exercised during the years ended December 31, 2021, 2020 and 2019 was $11.9 million, $11.5 million and $30.8 million, respectively.

The fair values of options granted were estimated at each grant date using the Black-Scholes valuation model with the following weighted-average assumptions:

	Years Ended December 31,
	2021			2020			2019
Expected volatility		68	%		71	%		74	%
Expected term (years)		6.0			6.0			6.1
Risk-free interest rate		0.6	%		1.4	%		2.3	%
Expected dividend yield		0.0	%		0.0	%		0.0	%

Restricted Stock Units

The following table summarizes restricted stock unit activity under the 2015 Plan (in thousands, except per share data):

				Weighted-
				average
				Grant Date
	Shares			Fair Value
Unvested balance at December 31, 2020		—		$	—
Granted		291		$	43.67
Vested		—		$	—
Forfeited		(14	)	$	44.55
Unvested balance at December 31, 2021		277		$	43.62

No restricted stock units vested during the years ended December 31, 2021 and 2020. The total intrinsic value of restricted stock units vested during the year ended December 31, 2019 was $1.8 million.

Employee Stock Purchase Plan

In June 2015, the Board of Directors adopted the 2015 ESPP, which became effective upon the Company’s initial public offering in September 2015. The number of authorized shares reserved for issuance under the 2015 ESPP automatically increases on the first business day of each fiscal year by the lesser of (i) 1% of the shares of common stock outstanding on the last business day of the prior fiscal year; or (ii) the number of shares determined by the Board of Directors. Unless otherwise determined by the administrator of the 2015 ESPP, two offering periods of six months’ duration will begin each year on January 1 and July 1. As of December 31, 2021, the total number of shares of common stock authorized for issuance under the 2015 ESPP was 998,683, of which 769,174 remained available for future issuance. During the years ended December 31, 2021, 2020 and 2019, 53,596, 55,499 and 35,994 shares of common stock, respectively, were issued under the 2015 ESPP. In January 2022, the Board of Directors authorized an additional 428,311 shares to be issued under the 2015 ESPP.

Retirement Plan

12 Months Ended

Dec. 31, 2021

Postemployment Benefits [Abstract]

Retirement Plan

12. Retirement Plan

The Company sponsors a defined-contribution retirement plan under Section 401(k) of the Internal Revenue Code (the 401(k) Plan). The 401(k) Plan covers all employees who meet defined minimum age and service requirements, and allows participants to defer a portion of their annual compensation. The Company matches employee deferrals up to a specified percentage of eligible compensation. For the years ended December 31, 2021, 2020 and 2019, the Company incurred expenses of $2.6 million, $2.2 million and $1.8 million, respectively, for matching contributions to the 401(k) Plan.

Income Taxes

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Income Taxes

13. Income Taxes

The components of income (loss) before income taxes were as follows (in thousands):

	Years Ended December 31,
	2021			2020			2019
United States	$	141,303		$	(105,960	)	$	(97,435	)
Foreign		(56	)		(50	)		(53	)
Total income (loss) before income taxes	$	141,247		$	(106,010	)	$	(97,488	)

The components of the provision for income tax expense (benefit) were as follows (in thousands):

	Years Ended December 31,
	2021		2020		2019
Current:
Federal	$	4,107	$	—	$	—
State		9,300		5,240		(2,288	)
Foreign		—		—		—
Total current		13,407		5,240		(2,288	)
Deferred:
Federal		—		—		(284	)
State		—		—		(183	)
Foreign		—		—		—
Total deferred		—		—		(467	)
Total income tax expense (benefit)	$	13,407	$	5,240	$	(2,755	)

In response to the COVID-19 pandemic, the Coronavirus Aid, Relief and Economic Security Act (the CARES Act) was signed into law in March 2020. The CARES Act (i) lifted certain deduction limitations originally imposed by the TCJA, (ii) allowed corporate taxpayers to carryback net operating losses (NOLs) originating during 2018 through 2020 for up to five years, which was not previously allowed under the TCJA, (iii) eliminated the 80% of taxable income limitations on NOL utilization imposed by the TCJA, allowing corporate entities to fully utilize NOL carryforwards to offset taxable income in 2018, 2019 or 2020, and (iv) enacted various other changes to corporate taxation. Also included in the CARES Act was a change to the TCJA related to qualified

improvement property, retroactively allowing for a 15-year recovery period and bonus depreciation. As a result of this change, the Company recorded current income tax benefit of $0.5 million for the year ended December 31, 2020 related to a reduction of state taxes associated with additional depreciation deductions allowed for the 2018 tax year. Overall, the enactment of the CARES Act, including the change for qualified improvement property, did not result in any material adjustments to the Company’s income tax provision for the year ended December 31, 2020.

Beginning in 2022, the TCJA eliminates the option to deduct research and development expenses currently and requires taxpayers to amortize such costs over a period of five years. While the Federal government is currently considering legislation that would defer or repeal this provision, there is no assurance such legislation will be enacted. The Company does not currently expect this provision of the TCJA will have a material impact on its tax position or operating cash flows for the year ended December 31, 2022, however, the actual impact of this provision to future periods is uncertain as of this time.

The following table presents a reconciliation of income tax expense (benefit) computed at the statutory federal income tax rate of 21% to income tax expense (benefit) reported in the consolidated statements of operations and comprehensive income (loss) (in thousands):

	Years Ended December 31,
	2021			2020			2019
Federal income tax expense (benefit) at statutory rate	$	29,662		$	(22,263	)	$	(20,473	)
State income tax expense (benefit), net of federal tax effect		9,183			(11,495	)		(15,323	)
Research and development credits		(10,059	)		(7,793	)		(11,075	)
Stock-based compensation		755			587			(2,134	)
Executive compensation		1,511			202			—
Other non-deductible expenses and reconciling items		329			684			144
Change in corporate tax rates		14,772			109			130
Change in valuation allowance		(32,746	)		45,209			45,976
Total income tax expense (benefit)	$	13,407		$	5,240		$	(2,755	)

The significant components of the Company’s net deferred tax assets were as follows (in thousands):

	As of December 31,
	2021			2020
Deferred tax assets:
Net operating loss carryforwards	$	3,981		$	14,683
Research and development tax credits		45,576			47,970
Stock-based compensation		18,303			15,644
Lease liabilities		23,430			21,961
Liability related sale of future royalties		43,234			62,089
Accruals and other		6,230			7,370
Total deferred tax assets before valuation allowance		140,754			169,717
Valuation allowance		(110,756	)		(142,907	)
Total deferred tax assets		29,998			26,810
Deferred tax liabilities:
Unrealized gains on marketable securities		—			(163	)
Right-of-use assets		(16,363	)		(21,094	)
Depreciation and amortization		(13,635	)		(5,155	)
Other		—			(398	)
Total deferred tax liabilities		(29,998	)		(26,810	)
Net deferred tax assets	$	—		$	—

The Company evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets as of December 31, 2021 and 2020. Based on the Company’s history of operating losses, and other relevant facts and circumstances, the Company concluded that it was more likely than not that the benefit of its deferred tax assets will not be realized. Accordingly, the Company provided a full valuation allowance for its net deferred tax assets as of December 31, 2021 and 2020. The valuation allowance increased (decreased) by $(32.2) million and $45.4 million during the years ended December 31, 2021 and 2020, respectively. The decrease in the valuation allowance during the year ended December 31, 2021 was due primarily to the utilization of

federal and state NOLs and research and development tax credit carryforwards, a decrease in the deferred tax asset for the liability related to the sale of future royalties and other decreases in net deferred tax assets during the period. The increase in the valuation allowance during the year ended December 31, 2020 was due primarily to an increase in deferred tax assets resulting from the sale of the Company’s Zolgensma royalty rights to HCR in December 2020, which was treated as a sale for tax purposes, research and development credits generated during the period, stock-based compensation expense and realized gains on sales of marketable securities, the impact of which was partially offset by the utilization of federal and state NOLs during the period.

As of December 31, 2021 and 2020, the Company had U.S. federal NOL carryforwards of zero and approximately $44.7 million, respectively, and U.S. state NOL carryforwards of approximately $59.9 million and $79.7 million, respectively, which may be available to offset future income tax liabilities. A portion of the Company’s U.S. state NOL carryforwards as of December 31, 2021 may be carried forward indefinitely, with the remaining portion expiring at various dates between 2034 and 2041.

As of December 31, 2021 and 2020, the Company had U.S. federal and state research and development tax credit carryforwards of approximately $45.6 million and $48.0 million, respectively, net of unrecognized tax benefits of $0.1 million and $0.1 million, respectively, which may be available to reduce future income tax liabilities and expire at various dates between 2035 and 2041. The calculation of these credits requires assumptions to be made by the Company to estimate qualified research expenses. The Company conducts formal studies to document the qualified activities and expenses used to calculate these credits, however a portion of these credits may be subject to future studies which have not yet occurred, the results of which may result in an adjustment to the Company’s credit carryforwards. The Company accounts for uncertain tax positions in accordance with the requirements of ASC 740, and recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. As of December 31, 2021 and 2020, the Company had total unrecognized tax benefits of $0.1 million and $0.1 million, respectively, which were reserved against its research and development tax credit carryforwards as uncertain tax positions. No reserve for uncertain tax positions has been placed against qualified expenses for which a study has not been conducted. However, a full valuation allowance has been provided against the net credit carryforwards and, if an adjustment is required upon the completion of the study, this adjustment would be offset by an adjustment to the deferred tax asset established for the research and development credit carryforwards and the valuation allowance. If these unrecognized tax benefits were to be recognized, the impact would be offset by an adjustment to the valuation allowance, resulting in no impact on the Company’s effective tax rate. The Company does not expect that a significant portion of its unrecognized tax benefits will increase or decrease in the next 12 months as of December 31, 2021.

Under the provisions of the Internal Revenue Code, the Company’s NOL and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. NOL and tax credit carryforwards may be subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three-year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. The Company has completed several financings since its inception which may have resulted in a change in control as defined by Sections 382 and 383 of the Internal Revenue Code, or could result in a change in control in the future.

The Company and its subsidiaries file income tax returns in the United States, at the federal level and in various states, and in foreign jurisdictions. The U.S. federal and state income tax returns are generally subject to tax examinations for the tax years ended December 31, 2017 onward. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service or state tax authorities to the extent utilized in a future period.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI http://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Related Party Transactions

12 Months Ended

Dec. 31, 2021

Related Party Transactions

14. Related Party Transactions

FOXKISER LLP

Since 2016, the Company has been party to professional services agreements with FOXKISER LLP (FOXKISER), an affiliate of certain stockholders of the Company and an affiliate of a member of the Company’s Board of Directors, pursuant to which the Company pays a fixed monthly fee in consideration for certain strategic services provided by FOXKISER. Effective January 2019, the Company entered into a new professional services agreement with FOXKISER with similar terms and conditions as the previous agreements. The agreement was amended effective June 2019 to expand the scope of the services provided and increase the monthly fee. Effective August 2020, the agreement was further amended to extend the term of the agreement by two years through December 2022. The agreement may be terminated by either party with six months’ advanced written notice. In December 2021, the Company provided notice of termination of the agreement to FOXKISER, with such termination to be effective in June 2022. Expenses incurred under the agreement with FOXKISER for the years ended December 31, 2021, 2020 and 2019 were $4.8 million, $4.8 million and $4.1 million, respectively, and were recorded as research and development expenses in the consolidated statements of operations and comprehensive income (loss).

Net Income (Loss) Per Share

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Net Income (Loss) Per Share

15. Net Income (Loss) Per Share

The computations of basic and diluted net income (loss) per share were as follows (in thousands, except per share data):

	Years Ended December 31,
	2021		2020			2019
Basic net income (loss) per share:
Net income (loss)	$	127,840	$	(111,250	)	$	(94,733	)
Shares used in computation:
Weighted-average common shares outstanding		42,438		37,281			36,690
Basic net income (loss) per share	$	3.01	$	(2.98	)	$	(2.58	)

Diluted net income (loss) per share:
Net income (loss)	$	127,840	$	(111,250	)	$	(94,733	)
Shares used in computation:
Weighted-average common shares outstanding		42,438		37,281			36,690
Stock options		1,467		—			—
Restricted stock units		2		—			—
Employee stock purchase plan		6		—			—
Weighted-average diluted common shares		43,913		37,281			36,690
Diluted net income (loss) per share	$	2.91	$	(2.98	)	$	(2.58	)

For periods in which the Company incurred net losses, common stock equivalents were excluded from the calculation of diluted net loss per share as their effect would be anti-dilutive. Accordingly, basic and diluted net loss per share were the same for such periods. The following potentially dilutive common stock equivalents outstanding at the end of the period were excluded from the computations of weighted-average diluted common shares for the periods indicated as their effects would be anti-dilutive (in thousands):

	Years Ended December 31,
	2021		2020		2019
Stock options issued and outstanding		4,939		6,361		5,544
Unvested restricted stock units outstanding		248		—		—
Employee stock purchase plan		—		19		17
		5,187		6,380		5,561

Supplemental Disclosures

12 Months Ended

Dec. 31, 2021

Payables And Accruals [Abstract]

Supplemental Disclosures

16. Supplemental Disclosures

Accrued expenses and other current liabilities consisted of the following (in thousands):

	As of December 31,
	2021		2020
Accrued sublicense fees and royalties	$	23,483	$	12,160
Accrued personnel costs		19,849		13,155
Accrued external research and development expenses		11,783		9,738
Accrued income taxes payable		11,325		3,135
Accrued purchases of property and equipment		5,285		7,853
Accrued external general and administrative expenses		3,642		2,865
Other accrued expenses and current liabilities		744		176
	$	76,111	$	49,082

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Basis of Presentation and Principles of Consolidation

Foreign Currency Transactions

Use of Estimates

Segment and Geographical Information

Cash and Cash Equivalents

The Company considers all highly liquid investments purchased with original maturities of 90 days or less at acquisition to be cash equivalents.

Restricted Cash

	As of December 31,
	2021		2020		2019
Cash and cash equivalents	$	345,209	$	338,426	$	69,514
Restricted cash		2,030		1,330		1,330
Total cash and cash equivalents and restricted cash	$	347,239	$	339,756	$	70,844

Marketable Securities

Accounts Receivable

Concentrations of Credit Risk and Off-balance Sheet Risk

The following table summarizes those customers who represented at least 10% of revenues or total net accounts receivable for the periods presented:

	Revenues									Accounts Receivable, Net
	Years Ended December 31,									As of December 31,
	2021			2020			2019			2021			2020
Customer A		79	%	*			*			*			*
Customer B		20	%		94	%		69	%		77	%		44	%
Customer C	*			*			*				14	%		48	%
Customer D	*			*				13	%	*			*
Customer E	*			*				10	%	*			*

*	Represented less than 10%

Leases

Property and Equipment

	Estimated Useful Life
Computer equipment and software	3 years
Furniture and fixtures	5 years
Laboratory and manufacturing equipment	5 to 15 years
Leasehold improvements	Shorter of lease term or estimated useful life

Impairment of Long-lived Assets

Non-marketable Equity Securities

Fair Value of Financial Instruments

•

Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

•

Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly.

•

Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable.

Revenue Recognition

License and Royalty Revenue

Collaborative Arrangements

Cost of Revenues

Research and Development Expenses

Stock-based Compensation

The Company has elected to not estimate forfeitures of stock-based awards and accounts for forfeitures as they occur.

The Company estimates the fair value of restricted stock units based on the fair value of the Company’s common stock on the date of the grant.

Income Taxes

Net Income (Loss) Per Share

Comprehensive Income (Loss)

Recent Accounting Pronouncements

Correction of Previously Issued Financial Statements

Recent Accounting Pronouncements

Recently Adopted Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Summary of Reconciliation of Cash and Cash Equivalents and Restricted Cash

The following table provides a reconciliation of cash and cash equivalents and restricted cash as reported on the consolidated balance sheets to the total of these amounts as reported at the end of the period in the consolidated statements of cash flows (in thousands):

	As of December 31,
	2021		2020		2019
Cash and cash equivalents	$	345,209	$	338,426	$	69,514
Restricted cash		2,030		1,330		1,330
Total cash and cash equivalents and restricted cash	$	347,239	$	339,756	$	70,844

Schedule of Revenue or Accounts Receivable by Major Customers

The following table summarizes those customers who represented at least 10% of revenues or total net accounts receivable for the periods presented:

	Revenues									Accounts Receivable, Net
	Years Ended December 31,									As of December 31,
	2021			2020			2019			2021			2020
Customer A		79	%	*			*			*			*
Customer B		20	%		94	%		69	%		77	%		44	%
Customer C	*			*			*				14	%		48	%
Customer D	*			*				13	%	*			*
Customer E	*			*				10	%	*			*

*	Represented less than 10%

Summary of Estimated Useful Lives of Assets

Depreciation and amortization is calculated using the straight-line method over the estimated useful lives of the assets, which are as follows:

	Estimated Useful Life
Computer equipment and software	3 years
Furniture and fixtures	5 years
Laboratory and manufacturing equipment	5 to 15 years
Leasehold improvements	Shorter of lease term or estimated useful life

Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2021

Investments Debt And Equity Securities [Abstract]

Summary of Company Marketable Securities

The following tables present a summary of the Company’s marketable securities, which consist solely of available-for-sale debt securities (in thousands):

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2021
U.S. government and agency securities	$	60,118	$	—	$	(229	)	$	59,889
Certificates of deposit		2,936		2		(11	)		2,927
Corporate bonds		442,792		62		(1,533	)		441,321
	$	505,846	$	64	$	(1,773	)	$	504,137

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2020
U.S. government and agency securities	$	12,782	$	22	$	—		$	12,804
Certificates of deposit		1,956		34		—			1,990
Corporate bonds		165,850		497		(55	)		166,292
Municipal securities		3,035		2		—			3,037
	$	183,623	$	555	$	(55	)	$	184,123

Summary of unrealized gain (loss) on available-for-sale securities, net, presented in the statements of operations and comprehensive income (loss)

Unrealized gain (loss) on available-for-sale securities, net, presented in the statements of operations and comprehensive income (loss) consisted of the following (in thousands):

	Years Ended December 31,
	2021			2020			2019
Unrealized gain (loss) before reclassifications	$	(2,202	)	$	(426	)	$	1,392
Realized gains reclassified to investment income		(7	)		(139	)		(40	)
Income tax expense		—			—			(467	)
Unrealized gain (loss) on available-for-sale securities, net	$	(2,209	)	$	(565	)	$	885

Summary of Fair Values and Unrealized Losses of Marketable Securities Held by the Company in an Unrealized Loss Position for Less Than 12 months and 12 Months or Greater

	Less than 12 Months					12 Months or Greater				Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
December 31, 2021
U.S. government and agency securities	$	59,889	$	(229	)	$	—	$	—	$	59,889	$	(229	)
Certificates of deposit		2,195		(11	)		—		—		2,195		(11	)
Corporate bonds		385,115		(1,533	)		—		—		385,115		(1,533	)
	$	447,199	$	(1,773	)	$	—	$	—	$	447,199	$	(1,773	)

	Less than 12 Months					12 Months or Greater				Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
December 31, 2020
Corporate bonds	$	55,507	$	(55	)	$	—	$	—	$	55,507	$	(55	)
	$	55,507	$	(55	)	$	—	$	—	$	55,507	$	(55	)

Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Schedule of Fair Value of Cash Equivalents and Marketable Securities

The following tables present the fair value of cash equivalents and marketable securities in accordance with the hierarchy discussed in Note 2 (in thousands):

	Quoted		Significant
	prices		other		Significant
	in active		observable		unobservable
	markets		inputs		inputs
	(Level 1)		(Level 2)		(Level 3)		Total
December 31, 2021
Cash equivalents:
Money market mutual funds	$	—	$	236,340	$	—	$	236,340
Total cash equivalents		—		236,340		—		236,340
Marketable securities:
U.S. government and agency securities		—		59,889		—		59,889
Certificates of deposit		—		2,927		—		2,927
Corporate bonds		—		441,321		—		441,321
Total marketable securities		—		504,137		—		504,137
Total cash equivalents and marketable securities	$	—	$	740,477	$	—	$	740,477

	Quoted		Significant
	prices		other		Significant
	in active		observable		unobservable
	markets		inputs		inputs
	(Level 1)		(Level 2)		(Level 3)		Total
December 31, 2020
Cash equivalents:
Money market mutual funds	$	—	$	96,307	$	—	$	96,307
Total cash equivalents		—		96,307		—		96,307
Marketable securities:
U.S. government and agency securities		—		12,804		—		12,804
Certificates of deposit		—		1,990		—		1,990
Corporate bonds		—		166,292		—		166,292
Municipal securities		—		3,037		—		3,037
Total marketable securities		—		184,123		—		184,123
Total cash equivalents and marketable securities	$	—	$	280,430	$	—	$	280,430

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2021

Property Plant And Equipment [Abstract]

Schedule of Property and Equipment

Property and equipment, net consists of the following (in thousands):

	As of December 31,
	2021			2020
Laboratory and manufacturing equipment	$	56,976		$	26,306
Computer equipment and software		4,268			3,764
Furniture and fixtures		6,804			4,114
Leasehold improvements		92,535			44,957
Total property and equipment		160,583			79,141
Accumulated depreciation and amortization		(29,036	)		(22,674	)
Property and equipment, net	$	131,547		$	56,467

Leases (Tables)

12 Months Ended

Dec. 31, 2021

Leases [Abstract]

Summary of Lease Costs and Supplemental Cash Flow Information of Operating Leases

The following table summarizes the Company’s lease costs and supplemental cash flow information related to its operating leases (in thousands):

	Years Ended December 31,
	2021			2020			2019
Operating lease cost	$	9,729		$	5,246		$	3,040
Variable lease cost		2,348			1,104			666
Total lease cost	$	12,077		$	6,350		$	3,706

Cash paid (received) for amounts included in operating lease liabilities	$	(6,765	)	$	(678	)	$	2,724
Right-of-use assets acquired through operating lease liabilities	$	1,955		$	56,956		$	5,114

Weighted-Average Remaining Lease Term and Weighted-Average Discount Rate of Operating Leases

The weighted-average remaining lease term and weighted-average discount rate of the Company’s operating leases were as follows:

	As of December 31,
	2021			2020
Weighted-average remaining lease term (years)		13.2			13.7
Weighted-average discount rate		5.6	%		5.6	%

Reconciliation of Undiscounted Future Minimum Lease Payments Remaining Operating Leases

	As of
	December 31, 2021
Undiscounted future minimum lease payments:
2022	$	6,556
2023		9,163
2024		10,224
2025		10,383
2026		10,388
Thereafter		83,050
Total undiscounted future minimum lease payments	$	129,764
Amount representing imputed interest		(41,619	)
Tenant improvement allowance not yet received		(1,464	)
Total operating lease liabilities		86,681
Current portion of operating lease liabilities		(1,752	)
Operating lease liabilities, non-current	$	84,929

Liability Related to Sale of Future Royalties (Tables)

12 Months Ended

Dec. 31, 2021

Schedule of Activity Within Liability Related to Sale of Future Royalties

The following table presents the changes in the liability related to the sale of future royalties under the Royalty Purchase Agreement with HCR (in thousands):

	Liability Related to
	Sale of Future Royalties
Proceeds from sale of future royalties in December 2020	$	196,000
Deferred transaction costs		(3,473	)
Interest expense recognized		771
Balance at December 31, 2020		193,298
Zolgensma royalties paid to HCR		(48,226	)
Interest expense recognized		26,277
Balance at December 31, 2021		171,349
Current portion of liability related to sale of future royalties		(37,889	)
Liability related to sale of future royalties, non-current	$	133,460

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2021

The Trustees of the University of Pennsylvania [Member]

Summary of Expenses Incurred by Company

Expenses incurred by the Company related to the license from Penn were recorded as follows (in thousands):

	Years Ended December 31,
	2021		2020		2019
Cost of revenues	$	8,046	$	39	$	—
Research and development		—		—		200
General and administrative		706		821		905
	$	8,752	$	860	$	1,105

GlaxoSmithKline LLC [Member]

Summary of Expenses Incurred by Company

Expenses incurred by the Company related to the license from GSK were recorded as follows (in thousands):

	Years Ended December 31,
	2021		2020		2019
Cost of revenues:
Royalties on net sales of Zolgensma	$	43,161	$	26,278	$	5,822
Other cost of revenues		626		9,398		2,419
Total cost of revenues		43,787		35,676		8,241
General and administrative		889		1,046		928
	$	44,676	$	36,722	$	9,169

Capitalization (Tables)

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Schedule of Shares of Common Stock Reserved for Future Issuance

Shares of common stock reserved for future issuance were as follows (in thousands):

	As of December 31,
	2021		2020
Reserved for issuance under equity incentive plans		9,755		8,659
Reserved for issuance under employee stock purchase plan		769		448
		10,524		9,107

- Definition

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

+ References

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+ Details

License and Collaboration Agreements (Tables)

12 Months Ended

Dec. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Schedule Of License and Royalty Revenue

License and royalty revenue consisted of the following (in thousands):

	Years Ended December 31,
	2021		2020		2019
AbbVie collaboration and license agreement	$	370,000	$	—	$	—
Royalties on net sales of Zolgensma		94,978		61,631		20,829
Achievement of sales-based milestone for Zolgensma		—		80,000		—
Other license and royalty revenue		5,369		12,936		14,404
Total license and royalty revenue	$	470,347	$	154,567	$	35,233

Summary of Changes in Balances of Receivables, Contract Assets and Deferred Revenue

	Years Ended December 31,
	2021			2020			2019
Accounts receivable, net, current and non-current:
Balance, beginning of period	$	46,266		$	42,303		$	31,599
Additions		472,347			158,682			39,203
Deductions		(483,912	)		(154,719	)		(28,499	)
Balance, end of period	$	34,701		$	46,266		$	42,303

Contract assets:
Balance, beginning of period	$	350		$	—		$	750
Additions		1,074			350			1,000
Deductions		(350	)		—			(1,750	)
Balance, end of period	$	1,074		$	350		$	—

Deferred revenue, current and non-current:
Balance, beginning of period	$	4,232		$	3,333		$	3,933
Additions		—			1,124			—
Deductions		(899	)		(225	)		(600	)
Balance, end of period	$	3,333		$	4,232		$	3,333

Revenue recognized during the period from:
Amounts included in deferred revenue at beginning of period	$	390		$	—		$	600
Performance obligations satisfied in previous periods	$	98,575		$	146,772		$	26,689

Summary of Accounts Receivables, net

Accounts receivable, net consisted of the following (in thousands):

	As of December 31,
	2021			2020
Current accounts receivable:
Billed to customers	$	365		$	30,573
Unbilled		32,074			20,104
Allowance for credit losses		—			(7,678	)
Current accounts receivable, net		32,439			42,999
Non-current accounts receivable:
Unbilled		6,020			3,267
Allowance for credit losses		(3,758	)		—
Non-current accounts receivable, net		2,262			3,267
Total accounts receivable, net	$	34,701		$	46,266

Summary of Changes in Allowance For Credit Losses

The following table presents the changes in the allowance for credit losses related to accounts receivable and contract assets for the years ended December 31, 2021 and 2020 (in thousands):

	Allowance for Credit Losses
	Accounts Receivable			Contract Assets
Balance at December 31, 2019	$	—		$	—
Provision for credit losses (recoveries)		7,678			—
Write-offs		—			—
Balance at December 31, 2020		7,678			—
Provision for credit losses (recoveries)		(2,569	)		—
Changes in present value discount of receivables		(1,243	)		—
Write-offs		(108	)		—
Balance at December 31, 2021	$	3,758		$	—

Schedule of AbbVie Collaboration Agreement

The Company recognized the following amounts under the AbbVie Collaboration Agreement (in thousands):

	Year Ended
	December 31, 2021
License and royalty revenue	$	370,000
Reduction of research and development expense for costs reimbursable by AbbVie	$	5,866

License and Royalty Revenue (Tables)

12 Months Ended

Dec. 31, 2021

Schedule Of License and Royalty Revenue

License and royalty revenue consisted of the following (in thousands):

	Years Ended December 31,
	2021		2020		2019
AbbVie collaboration and license agreement	$	370,000	$	—	$	—
Royalties on net sales of Zolgensma		94,978		61,631		20,829
Achievement of sales-based milestone for Zolgensma		—		80,000		—
Other license and royalty revenue		5,369		12,936		14,404
Total license and royalty revenue	$	470,347	$	154,567	$	35,233

Novartis Gene Therapies [Member]

Schedule Of License and Royalty Revenue

The Company recognized the following amounts under the March 2014 License with Novartis Gene Therapies (in thousands):

	Years Ended December 31,
	2021		2020		2019
Royalties on net sales of Zolgensma	$	94,978	$	61,631	$	20,829
Achievement of sales-based milestone for Zolgensma		—		80,000		—
Other license revenue		—		3,500		3,500
Total license and royalty revenue	$	94,978	$	145,131	$	24,329

Interest income from licensing	$	22	$	26	$	29

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Stock-Based Compensation Expense by Award Type

The Company’s stock-based compensation expense by award type was as follows (in thousands):

	Years Ended December 31,
	2021		2020		2019
Stock options	$	35,320	$	31,178	$	25,964
Restricted stock units		2,835		—		257
Employee stock purchase plan		653		771		633
	$	38,808	$	31,949	$	26,854

Stock-Based Compensation Expense

The Company recorded aggregate stock-based compensation expense in the consolidated statements of operations and comprehensive income (loss) as follows (in thousands):

	Years Ended December 31,
	2021		2020		2019
Research and development	$	19,602	$	16,280	$	13,031
General and administrative		19,206		15,669		13,823
	$	38,808	$	31,949	$	26,854

Schedule of Fair Value of Options Granted on Weighted-Average Assumptions

The fair values of options granted were estimated at each grant date using the Black-Scholes valuation model with the following weighted-average assumptions:

	Years Ended December 31,
	2021			2020			2019
Expected volatility		68	%		71	%		74	%
Expected term (years)		6.0			6.0			6.1
Risk-free interest rate		0.6	%		1.4	%		2.3	%
Expected dividend yield		0.0	%		0.0	%		0.0	%

Summary of Unvested RSUs Activity Under 2015 Plan

The following table summarizes restricted stock unit activity under the 2015 Plan (in thousands, except per share data):

				Weighted-
				average
				Grant Date
	Shares			Fair Value
Unvested balance at December 31, 2020		—		$	—
Granted		291		$	43.67
Vested		—		$	—
Forfeited		(14	)	$	44.55
Unvested balance at December 31, 2021		277		$	43.62

2014 and 2015 Equity Incentive Plan [Member]

Summary of Stock Option Activity

The following table summarizes stock option activity under the 2014 Plan and 2015 Plan (in thousands, except per share data):

						Weighted-
						average
				Weighted-		Remaining
				average		Contractual		Aggregate
				Exercise		Life		Intrinsic
	Shares			Price		(Years)		Value (a)
Outstanding at December 31, 2020		6,361		$	31.21		7.2	$	101,356
Granted		1,437		$	43.04
Exercised		(404	)	$	11.46
Cancelled or forfeited		(268	)	$	45.98
Outstanding at December 31, 2021		7,126		$	34.16		6.8	$	41,128
Exercisable at December 31, 2021		4,566		$	29.62		5.9	$	40,607
Vested and expected to vest at December 31, 2021		7,126		$	34.16		6.8	$	41,128

(a)	The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of the common stock for the options that were in the money at the dates reported.

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Components of Income (Loss) Before Income Taxes

The components of income (loss) before income taxes were as follows (in thousands):

	Years Ended December 31,
	2021			2020			2019
United States	$	141,303		$	(105,960	)	$	(97,435	)
Foreign		(56	)		(50	)		(53	)
Total income (loss) before income taxes	$	141,247		$	(106,010	)	$	(97,488	)

Components of the Provision For Income Tax Expense (Benefit)

The components of the provision for income tax expense (benefit) were as follows (in thousands):

	Years Ended December 31,
	2021		2020		2019
Current:
Federal	$	4,107	$	—	$	—
State		9,300		5,240		(2,288	)
Foreign		—		—		—
Total current		13,407		5,240		(2,288	)
Deferred:
Federal		—		—		(284	)
State		—		—		(183	)
Foreign		—		—		—
Total deferred		—		—		(467	)
Total income tax expense (benefit)	$	13,407	$	5,240	$	(2,755	)

Schedule of Reconciliation of Effective Income Tax Expense (Benefit)

	Years Ended December 31,
	2021			2020			2019
Federal income tax expense (benefit) at statutory rate	$	29,662		$	(22,263	)	$	(20,473	)
State income tax expense (benefit), net of federal tax effect		9,183			(11,495	)		(15,323	)
Research and development credits		(10,059	)		(7,793	)		(11,075	)
Stock-based compensation		755			587			(2,134	)
Executive compensation		1,511			202			—
Other non-deductible expenses and reconciling items		329			684			144
Change in corporate tax rates		14,772			109			130
Change in valuation allowance		(32,746	)		45,209			45,976
Total income tax expense (benefit)	$	13,407		$	5,240		$	(2,755	)

Components of Net Deferred Tax Assets

The significant components of the Company’s net deferred tax assets were as follows (in thousands):

	As of December 31,
	2021			2020
Deferred tax assets:
Net operating loss carryforwards	$	3,981		$	14,683
Research and development tax credits		45,576			47,970
Stock-based compensation		18,303			15,644
Lease liabilities		23,430			21,961
Liability related sale of future royalties		43,234			62,089
Accruals and other		6,230			7,370
Total deferred tax assets before valuation allowance		140,754			169,717
Valuation allowance		(110,756	)		(142,907	)
Total deferred tax assets		29,998			26,810
Deferred tax liabilities:
Unrealized gains on marketable securities		—			(163	)
Right-of-use assets		(16,363	)		(21,094	)
Depreciation and amortization		(13,635	)		(5,155	)
Other		—			(398	)
Total deferred tax liabilities		(29,998	)		(26,810	)
Net deferred tax assets	$	—		$	—

Net Income (Loss) Per Share (Tables)

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Computations of Basic and Diluted Net Income (Loss) Per Share

The computations of basic and diluted net income (loss) per share were as follows (in thousands, except per share data):

	Years Ended December 31,
	2021		2020			2019
Basic net income (loss) per share:
Net income (loss)	$	127,840	$	(111,250	)	$	(94,733	)
Shares used in computation:
Weighted-average common shares outstanding		42,438		37,281			36,690
Basic net income (loss) per share	$	3.01	$	(2.98	)	$	(2.58	)

Diluted net income (loss) per share:
Net income (loss)	$	127,840	$	(111,250	)	$	(94,733	)
Shares used in computation:
Weighted-average common shares outstanding		42,438		37,281			36,690
Stock options		1,467		—			—
Restricted stock units		2		—			—
Employee stock purchase plan		6		—			—
Weighted-average diluted common shares		43,913		37,281			36,690
Diluted net income (loss) per share	$	2.91	$	(2.98	)	$	(2.58	)

Schedules for Computation of Diluted Weighted-Average Shares Outstanding

The following potentially dilutive common stock equivalents outstanding at the end of the period were excluded from the computations of weighted-average diluted common shares for the periods indicated as their effects would be anti-dilutive (in thousands):

	Years Ended December 31,
	2021		2020		2019
Stock options issued and outstanding		4,939		6,361		5,544
Unvested restricted stock units outstanding		248		—		—
Employee stock purchase plan		—		19		17
		5,187		6,380		5,561

Supplemental Disclosures (Tables)

12 Months Ended

Dec. 31, 2021

Payables And Accruals [Abstract]

Schedules of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):

	As of December 31,
	2021		2020
Accrued sublicense fees and royalties	$	23,483	$	12,160
Accrued personnel costs		19,849		13,155
Accrued external research and development expenses		11,783		9,738
Accrued income taxes payable		11,325		3,135
Accrued purchases of property and equipment		5,285		7,853
Accrued external general and administrative expenses		3,642		2,865
Other accrued expenses and current liabilities		744		176
	$	76,111	$	49,082

Nature of Business - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accumulated deficit	$ (161,232)	$ (289,072)
Cash, cash equivalents and marketable securities	$ 849,300

- Definition

The cumulative amount of the reporting entity's undistributed earnings or deficit.

+ References + Details

Summary of Significant Accounting Policies - Additional Information (Detail)		3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Jan. 01, 2019 USD ($)	Mar. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($) Segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Significant Accounting Policies [Line Items]
Number of operating segments \| Segment					1
Impairment losses					$ 0	$ 0	$ 0
Percentage of ownership interest					20.00%
Accrued interest or penalties related to uncertain tax positions					$ 0	0	$ 0
Unrecognized tax benefits					0	0
Accumulated deficit					(161,232,000)	(289,072,000)
Software and Software Development Costs \| ASU 2016-02 [Member]
Significant Accounting Policies [Line Items]
Capitalized costs net					3,300,000	1,600,000
Amortization of capitalized costs					$ 600,000	$ 100,000
Royalty Agreements
Significant Accounting Policies [Line Items]
Non Cash Interest Expense		$ 2,900,000	$ 9,100,000	$ 15,300,000
Maximum [Member] \| ASU 2016-02 [Member]
Significant Accounting Policies [Line Items]
Accumulated deficit	$ 100,000
Maximum [Member] \| ASU 2018-02 [Member]
Significant Accounting Policies [Line Items]
Accumulated deficit	100,000
Reclassification of stranded tax effects of unrealized gains and losses on available-for-sale securities from accumulated other comprehensive income (loss) to accumulated deficit	$ 100,000
Customer Concentration Risk [Member] \| Revenue [Member] \| UNITED STATES
Significant Accounting Policies [Line Items]
Concentration risk percentage					7.00%	80.00%	90.00%
Customer Concentration Risk [Member] \| Revenue [Member] \| BERMUDA
Significant Accounting Policies [Line Items]
Concentration risk percentage					79.00%
Customer Concentration Risk [Member] \| Revenue [Member] \| Other Countries \| Maximum [Member]
Significant Accounting Policies [Line Items]
Concentration risk percentage					10.00%	10.00%	10.00%

Summary of Significant Accounting Policies - Summary of Reconciliation of Cash and Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cash and cash equivalents	$ 345,209	$ 338,426	$ 69,514
Restricted cash	2,030	1,330	1,330
Total cash and cash equivalents and restricted cash	$ 347,239	$ 339,756	$ 70,844

Summary of Significant Accounting Policies - Schedule of Revenue or Accounts Receivable by Major Customers (Detail) - Customer Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue [Member] \| Customer A [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage	79.00%
Revenue [Member] \| Customer B [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage	20.00%	94.00%	69.00%
Revenue [Member] \| Customer D [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage			13.00%
Revenue [Member] \| Customer E
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage			10.00%
Accounts Receivable \| Customer B [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage	77.00%	44.00%
Accounts Receivable \| Customer C [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage	14.00%	48.00%

Summary of Significant Accounting Policies - Summary of Estimated Useful Lives of Assets (Detail)	12 Months Ended
	Dec. 31, 2021
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Property plant and equipment estimated useful lives	3 years
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Property plant and equipment estimated useful lives	5 years
Laboratory and Manufacturing Equipment [Member] \| Minimum [Member]
Property Plant And Equipment [Line Items]
Property plant and equipment estimated useful lives	5 years
Laboratory and Manufacturing Equipment [Member] \| Maximum [Member]
Property Plant And Equipment [Line Items]
Property plant and equipment estimated useful lives	15 years
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Property plant and equipment estimated useful lives	Shorter of lease term or estimated useful life

Marketable Securities - Summary of Company Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	$ 505,846	$ 183,623
Unrealized Gains	64	555
Unrealized Losses	(1,773)	(55)
Fair Value	504,137	184,123
U.S. Government and Agency Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	60,118	12,782
Unrealized Gains		22
Unrealized Losses	(229)
Fair Value	59,889	12,804
Certificates of Deposit [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	2,936	1,956
Unrealized Gains	2	34
Unrealized Losses	(11)
Fair Value	2,927	1,990
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	442,792	165,850
Unrealized Gains	62	497
Unrealized Losses	(1,533)	(55)
Fair Value	$ 441,321	166,292
Municipal Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost		3,035
Unrealized Gains		2
Fair Value		$ 3,037

Marketable Securities - Additional Information (Detail)	12 Months Ended
Marketable Securities - Additional Information (Detail)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2021 USD ($) Security
Schedule Of Available For Sale Securities [Line Items]
Available for sale debt securities remaining maturities greater than three years	$ 0		$ 0
Number of investment grade fixed income debt security \| Security			92
Non-marketable equity securities, carrying value	400,000
Marketable securities, realized gain	$ 4,800,000
Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Marketable securities, unrealized gain		$ 37,800,000

Marketable Securities - Summary of unrealized gain (loss) on available-for-sale securities, net, presented in the statements of operations and comprehensive income (loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Investments Debt And Equity Securities [Abstract]
Unrealized gain (loss) before reclassifications	$ (2,202)	$ (426)	$ 1,392
Realized gains reclassified to investment income	(7)	(139)	(40)
Income tax expense			(467)
Unrealized gain (loss) on available-for-sale securities, net	$ (2,209)	$ (565)	$ 885

Marketable Securities - Summary of Fair Values and Unrealized Losses of Marketable Securities Held by the Company in an Unrealized Loss Position for Less Than 12 months and 12 Months or Greater (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 447,199	$ 55,507
Less than 12 Months, Unrealized Losses	(1,773)	(55)
Total, Fair Value	447,199	55,507
Total, Unrealized Losses	(1,773)	(55)
U.S. Government and Agency Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	59,889
Less than 12 Months, Unrealized Losses	(229)
Total, Fair Value	59,889
Total, Unrealized Losses	(229)
Certificates of Deposit [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	2,195
Less than 12 Months, Unrealized Losses	(11)
Total, Fair Value	2,195
Total, Unrealized Losses	(11)
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	385,115	55,507
Less than 12 Months, Unrealized Losses	(1,533)	(55)
Total, Fair Value	385,115	55,507
Total, Unrealized Losses	$ (1,533)	$ (55)

Fair Value of Financial Instruments - Schedule of Fair Value of Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Marketable securities:
Fair Value	$ 504,137	$ 184,123
Cash Equivalents and Marketable Securities [Member]
Marketable securities:
Total cash equivalents and marketable securities	740,477	280,430
Corporate Bonds [Member]
Marketable securities:
Fair Value	441,321	166,292
Municipal Bonds
Marketable securities:
Fair Value		3,037
Cash Equivalents [Member]
Cash equivalents:
Total cash equivalents	236,340	96,307
US Government Agencies Debt Securities
Marketable securities:
Fair Value	59,889	12,804
Certificates of Deposit [Member]
Marketable securities:
Fair Value	2,927	1,990
Money Market Mutual Funds [Member] \| Cash Equivalents [Member]
Cash equivalents:
Total cash equivalents	236,340	96,307
Significant Other Observable Inputs (Level 2) [Member]
Marketable securities:
Fair Value	504,137	184,123
Significant Other Observable Inputs (Level 2) [Member] \| Cash Equivalents and Marketable Securities [Member]
Marketable securities:
Total cash equivalents and marketable securities	740,477	280,430
Significant Other Observable Inputs (Level 2) [Member] \| Corporate Bonds [Member]
Marketable securities:
Fair Value	441,321	166,292
Significant Other Observable Inputs (Level 2) [Member] \| Municipal Bonds
Marketable securities:
Fair Value		3,037
Significant Other Observable Inputs (Level 2) [Member] \| Cash Equivalents [Member]
Cash equivalents:
Total cash equivalents	236,340	96,307
Significant Other Observable Inputs (Level 2) [Member] \| US Government Agencies Debt Securities
Marketable securities:
Fair Value	59,889	12,804
Significant Other Observable Inputs (Level 2) [Member] \| Certificates of Deposit [Member]
Marketable securities:
Fair Value	2,927	1,990
Significant Other Observable Inputs (Level 2) [Member] \| Money Market Mutual Funds [Member] \| Cash Equivalents [Member]
Cash equivalents:
Total cash equivalents	$ 236,340	$ 96,307

Fair Value of Financial Instruments - Additional Information (Detail) € in Millions	12 Months Ended
	Dec. 31, 2021 USD ($)	Dec. 31, 2021 EUR (€)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Non-marketable equity securities			$ 1,100,000
Remeasurements or impairment losses on non-marketable equity securities	$ 0		$ 0	$ 0
Uni Qure N V
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Proceeds From Acquiring Business	5,600,000	€ 4.8
Additional Proceeds From Acquiring Business	600,000	0.5
Realized Gain	5,200,000
Revenue Recognition, Milestone Method, Revenue Recognized	$ 42,100,000	€ 37.1

Property and Equipment Net - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment	$ 160,583	$ 79,141
Accumulated depreciation and amortization	(29,036)	(22,674)
Property and equipment, net	131,547	56,467
Laboratory and Manufacturing Equipment [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	56,976	26,306
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	4,268	3,764
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	6,804	4,114
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	$ 92,535	$ 44,957

Property and Equipment Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 9,564	$ 8,407	$ 7,152

Leases - Additional Information (Detail) $ in Thousands	1 Months Ended					12 Months Ended
Leases - Additional Information (Detail) $ in Thousands	Nov. 30, 2020 USD ($)	May 31, 2019 USD ($)	Nov. 30, 2018 USD ($) ft²	May 31, 2016 USD ($)	Mar. 31, 2015	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Other Commitments [Line Items]
Tenant improvement allowance received						$ 11,400	$ 5,000
Property and equipment, net						131,547	56,467
Operating lease right-of-use assets						60,904	$ 63,815
Lease liabilities						$ 86,681
Rockville, Maryland [Member]
Other Commitments [Line Items]
Operating lease expiration year						2028
9804 Medical Center Drive [Member]
Other Commitments [Line Items]
Tenant improvement allowance received						$ 19,500
Tenant improvement allowance receivable						1,500
Property and equipment, net						113,200
Operating lease right-of-use assets						48,300
Lease liabilities						72,500
9804 Medical Center Drive [Member] \| Building [Member]
Other Commitments [Line Items]
Property and equipment, net						41,200
9804 Medical Center Drive [Member] \| Manufacturing Facility [Member]
Other Commitments [Line Items]
Property and equipment, net						$ 72,000
9804 Medical Center Drive [Member] \| Rockville, Maryland [Member]
Other Commitments [Line Items]
Number of square feet to be constructed \| ft²			186,000
Construction completion, description						The initial construction of the building was performed by the landlord and the lease commenced in September 2020 upon delivery of the leased premises to the Company to make additional improvements to the building.
Lease commenced date			2020-09
Lease expiration date			Sep. 30, 2036
Lease not yet commenced, option to terminate the lease						true
Lease not yet commenced, option to terminate the lease, description						The Company has the option to extend the term of the lease for up to 10 additional years and the option to terminate the lease, with payment of an early termination fee, after 12 years from the delivery of the leased premises to the Company.
Lease not yet commenced, additional lease term			10 years
Minimum release term for option to terminate			12 years
Letters of credit			$ 1,100
9712 Medical Center Drive [Member] \| Rockville, Maryland [Member]
Other Commitments [Line Items]
Lease commenced date					2015-04
Lease expiration date						Sep. 30, 2036
Tenant improvement allowance received						$ 400
Lease term						In October 2020, the 9712 Medical Center Drive Lease was amended to extend the lease term from September 2021 to February 2027, subject to extension options held by the Company.
Operating lease, existence of option to extend the lease						true
Increase decrease in right-of-use assets and lease liabilities						$ 7,200
Operating lease, option to extend description						The Company has an option to extend the term of the lease for three additional years, as well as an option to extend the lease term to be coterminous with the 9804 Medical Center Drive Lease, which expires in September 2036.
Additional lease term under option to extend						3 years
400 Madison Avenue [Member] \| 400 Madison Lease [Member]
Other Commitments [Line Items]
Letters of credit				$ 200
Increase decrease in right-of-use assets and lease liabilities		$ 5,200
Operating Lease Commencement Year				2016-07
Tenant improvement allowance entitled to received				$ 700
9600 Blackwell Road [Member] \| Rockville, Maryland [Member]
Other Commitments [Line Items]
Lease expiration date	Sep. 30, 2021
Increase decrease in right-of-use assets and lease liabilities	$ (700)
Operating lease, existence of option to terminate	true
Early termination fee	$ 400

Leases - Summary of Lease Costs and Supplemental Cash Flow Information of Operating Leases (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 9,729	$ 5,246	$ 3,040
Variable lease cost	2,348	1,104	666
Total lease cost	12,077	6,350	3,706
Cash paid (received) for amounts included in operating lease liabilities	(6,765)	(678)	2,724
Right-of-use assets acquired through operating lease liabilities	$ 1,955	$ 56,956	$ 5,114

Leases - Weighted-Average Remaining Lease Term and Weighted-Average Discount Rate of Operating Leases (Detail)	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Weighted-average remaining lease term (years)	13 years 2 months 12 days	13 years 8 months 12 days
Weighted-average discount rate	5.60%	5.60%

Leases - Reconciliation of Undiscounted Future Minimum Lease Payments Remaining Operating Leases (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Undiscounted future minimum lease payments:
2022	$ 6,556
2023	9,163
2024	10,224
2025	10,383
2026	10,388
Thereafter	83,050
Total undiscounted future minimum lease payments	129,764
Amount representing imputed interest	(41,619)
Tenant improvement allowance not yet received	(1,464)
Total operating lease liabilities	86,681
Current portion of operating lease liabilities	(1,752)	$ (2,500)
Operating lease liabilities, non-current	$ 84,929	$ 70,153

Liability Related to Sale of Future Royalties - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Liability Related To Sale Of Future Royalties [Line Items]
Repurchase of call option amount	$ 300,000
Proceeds from sale of future royalties		$ 196,000
Interest expense	26,277	771
November 7, 2024
Liability Related To Sale Of Future Royalties [Line Items]
Repurchase of call option amount, before exercised	1,000
HCR [Member]
Liability Related To Sale Of Future Royalties [Line Items]
Proceeds from Royalties Received	4,000
Deferred Transaction Cost	3,500
Interest expense	$ 192,500
Interest Rate, Effective Percentage	15.10%
HCR [Member] \| Other Noncurrent Liabilities
Liability Related To Sale Of Future Royalties [Line Items]
Proceeds from sale of future royalties	$ 196,000
HCR [Member] \| November 7, 2024
Liability Related To Sale Of Future Royalties [Line Items]
Royalty Payment Cap Amount	260,000
HCR [Member] \| November 8, 2024
Liability Related To Sale Of Future Royalties [Line Items]
Royalty Payment Cap Amount	300,000
Royalty Agreements
Liability Related To Sale Of Future Royalties [Line Items]
Proceeds from sale of future royalties		196,000
Deferred Transaction Cost		$ (3,473)
Royalty Agreements \| HCR [Member]
Liability Related To Sale Of Future Royalties [Line Items]
Purchase Agreement	$ 200,000

Liability Related to Sale of Future Royalties -Schedule of Activity Within Liability Related to Sale of Future Royalties (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Liability Related To Sale Of Future Royalties [Line Items]
Proceeds from sale of future royalties in December 2020		$ 196,000
Current portion of liability related to sale of future royalties	$ (37,889)	(18,794)
Liability related to sale of future royalties	133,460	174,504
Royalty Agreements
Liability Related To Sale Of Future Royalties [Line Items]
Proceeds from sale of future royalties in December 2020		196,000
Deferred Transaction Cost		(3,473)
Interest expense recognized	26,277	771
Ending balance	171,349	$ 193,298
Zolgensma royalties paid to HCR	(48,226)
Current portion of liability related to sale of future royalties	(37,889)
Liability related to sale of future royalties	$ 133,460

Commitments and Contingencies - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Aug. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Apr. 30, 2019	Mar. 31, 2009
Other Commitments [Line Items]
Claims paid to date related to indemnification issues		$ 0
Accruals or expenses related to indemnification issues		0	$ 0
University of Pennsylvania [Member]
Other Commitments [Line Items]
Accrued expenses		8,200,000	100,000
University of Pennsylvania [Member] \| Maximum [Member]
Other Commitments [Line Items]
Upfront fee, milestone fees				$ 20,500,000
GlaxoSmithKline LLC [Member]
Other Commitments [Line Items]
Accrued expenses		16,300,000	$ 13,100,000
Milestone payment obligation					$ 1,500,000
Clearside Biomedical Inc. [Member]
Other Commitments [Line Items]
Milestone payment obligation		$ 3,000,000.0
Payments against exercise of license option	$ 1,600,000
Clearside Biomedical Inc. [Member] \| Maximum [Member]
Other Commitments [Line Items]
Milestone payment obligation	$ 136,000,000.0

Commitments and Contingencies - Summary of Expenses Incurred by Company (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Zolgensma Royalties [Member]
Cost Of Revenue [Abstract]
Royalties on net sales of Zolgensma	$ 94,978	$ 61,631	$ 20,829
GlaxoSmithKline LLC [Member]
Other Commitments [Line Items]
Total related party transaction expense	44,676	36,722	9,169
GlaxoSmithKline LLC [Member] \| Zolgensma Royalties [Member]
Cost Of Revenue [Abstract]
Royalties on net sales of Zolgensma	43,161	26,278	5,822
GlaxoSmithKline LLC [Member] \| Other Costs Of Revenue [Member]
Other Commitments [Line Items]
Total related party transaction expense	626	9,398	2,419
GlaxoSmithKline LLC [Member] \| Cost of Revenues [Member]
Other Commitments [Line Items]
Total related party transaction expense	43,787	35,676	8,241
GlaxoSmithKline LLC [Member] \| General and Administrative [Member]
Other Commitments [Line Items]
Total related party transaction expense	889	1,046	928
License Fees [Member] \| The Trustees of the University of Pennsylvania [Member]
Other Commitments [Line Items]
Total related party transaction expense	8,752	860	1,105
License Fees [Member] \| The Trustees of the University of Pennsylvania [Member] \| Cost of Revenues [Member]
Other Commitments [Line Items]
Total related party transaction expense	8,046	39
License Fees [Member] \| The Trustees of the University of Pennsylvania [Member] \| Research and Development [Member]
Other Commitments [Line Items]
Total related party transaction expense			200
License Fees [Member] \| The Trustees of the University of Pennsylvania [Member] \| General and Administrative [Member]
Other Commitments [Line Items]
Total related party transaction expense	$ 706	$ 821	$ 905

Capitalization - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Schedule of Capitalization [Line Items]
Common stock, shares authorized		100,000,000	100,000,000
Common stock, par value		$ 0.0001	$ 0.0001
Preferred stock, shares authorized		10,000,000	10,000,000
Preferred stock, par value		$ 0.0001	$ 0.0001
Common Stock [Member]
Schedule of Capitalization [Line Items]
Issuance of stock, net of transaction costs		4,899,000
Public Offering [Member]
Schedule of Capitalization [Line Items]
Issuance of stock, net of transaction costs	4,899,000
Stock issuance price per share	$ 47.00
Net proceeds from issuance of common stock	$ 216.1
Overallotment Option [Member] \| Common Stock [Member]
Schedule of Capitalization [Line Items]
Issuance of stock, net of transaction costs	639,000

Capitalization - Schedule of Shares of Common Stock Reserved for Future Issuance (Detail) - shares shares in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Capitalization [Line Items]
Reserved common shares	10,524	9,107
Equity Incentive Plans [Member]
Schedule of Capitalization [Line Items]
Reserved common shares	9,755	8,659
Employee Stock Purchase Plan [Member]
Schedule of Capitalization [Line Items]
Reserved common shares	769	448

License and Collaboration Agreements - Additional Information (Detail)	1 Months Ended							3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2021 USD ($)	May 31, 2020 USD ($)	Apr. 30, 2020 USD ($)	Jul. 31, 2019	Nov. 30, 2018 USD ($)	Jan. 31, 2018 USD ($)	Mar. 31, 2014 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2021 USD ($) ProductCandidate	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jul. 31, 2020 USD ($)	Dec. 31, 2018 USD ($)	May 31, 2018 USD ($)
License Revenue [Line Items]
Milestone payment upon commencement of clinical trials in humans											$ 538,300,000
Milestone payment upon submission of regulatory approval filings											21,000,000.0
Milestone payment upon approval of commercial products by regulatory agencies											141,000,000.0
Milestone payment upon achievement of specified sales targets for licensed products											877,000,000.0
Accounts Receivable, after Allowance for Credit Loss											34,701,000	$ 46,266,000	$ 42,303,000		$ 31,599,000
Deferred revenue, current and non-current											3,333,000	4,232,000	3,333,000		$ 3,933,000
Provision for credit losses (recoveries)											(2,569,000)	7,678,000	0
Allowance for credit losses													0
License Revenue												3,500,000	3,500,000
Interest income from licensing											719,000	4,271,000	2,951,000
Accounts receivable, current											32,439,000	42,999,000
Accounts receivable (net of allowance of $3,758 as of December 31, 2021)											2,262,000	3,267,000
Abb Vie Global Enterprises Ltd
License Revenue [Line Items]
Accounts Receivable, after Allowance for Credit Loss											370,000,000.0
Novartis Gene Therapies [Member]
License Revenue [Line Items]
Accounts Receivable, after Allowance for Credit Loss												80,000,000.0
Interest income from licensing											22,000	26,000	29,000
Novartis Gene Therapies [Member] \| March 2014 License Agreement [Member]
License Revenue [Line Items]
Milestone payment upon achievement of specified sales targets for licensed products										$ 1,000,000,000.0
Up-front fee paid							$ 2,000,000.0
License Fees						$ 180,000,000.0
Cumulative payments																$ 12,300,000
Sales based milestone payments receivable								$ 80,000,000.0	$ 80,000,000.0
Revenue Recognition, Milestone Method, Revenue Recognized										$ 80,000,000.0
License Revenue												3,500,000	3,500,000
Accounts receivable											26,600,000	19,600,000
Zolgensma Royalties [Member] \| March 2014 License Agreement [Member]
License Revenue [Line Items]
Milestone payment upon achievement of specified sales targets for licensed products								$ 1,000,000,000.0	$ 1,000,000,000.0
Abeona Therapeutics Incorporation \| Contract Termination
License Revenue [Line Items]
Up-front and annual fees					$ 20,000.0
Abeona Therapeutics Incorporation \| November Two Thousand Eighteen License Agreement
License Revenue [Line Items]
Allowance for credit losses												7,700,000
Accounts receivable											30,100,000	30,100,000
License fee		$ 20,000,000.0	$ 8,000,000.0		$ 8,000.0
Abeona Therapeutics Incorporation \| November Two Thousand Eighteen License Agreement \| Contract Termination
License Revenue [Line Items]
Accounts receivable		$ 28,000.0									28,000.0			$ 33,600
Interest percentage on unpaid balances under license agreement					1.50%
License agreement termination claims, description		after the termination of the November 2018 License, Abeona filed a claim in arbitration alleging that the Company had breached certain responsibilities to communicate with Abeona regarding the Company’s prosecution of licensed patents under the November 2018 License. The Company disputed Abeona’s claim and filed a counterclaim in arbitration demanding payment of the $28.0 million of unpaid fees from Abeona, plus accrued interest.			As a result of the termination, Abeona was required to pay an additional $20.0 million license fee to the Company within 15 days of the termination date, which otherwise would have been due to the Company in November 2020.
Interest receivable		$ 5,600
Settlement agreement payable											30,000.0
Interest income from licensing												2,100,000
Abeona Therapeutics Incorporation \| November Two Thousand Twenty One License Agreement \| Contract Termination
License Revenue [Line Items]
Settlement agreement payable											20,000.0
Abeona Therapeutics Incorporation \| November Two Thousand Twenty Two License Agreement \| Contract Termination
License Revenue [Line Items]
Settlement agreement payable											5,000.0
Abeona Therapeutics Incorporation \| November Two Thousand Twenty Four License Agreement \| Contract Termination
License Revenue [Line Items]
Settlement agreement payable											5,000.0
Abeona Therapeutics Incorporation \| Settlement Agreement
License Revenue [Line Items]
Allowance for credit losses											3,800,000
Accounts receivable											8,800,000
Cash acquired in excess of payments to acquire business											20,000,000.0
Accounts receivable, current											5,000,000.0
Accounts receivable (net of allowance of $3,758 as of December 31, 2021)											3,800,000
Payments due from related party											5,000,000.0
Provision for credit losses (recoveries)											(2,600,000)	7,700,000
Abb Vie Collaboration And License Agreement
License Revenue [Line Items]
Up-front fee paid	$ 370,000,000.0
Milestone fee payments upon achievement of various development and commercialization	1,380,000,000
Transaction price of license											370,000,000.0
Reimbursement of development costs											5,900,000
Abb Vie Collaboration And License Agreement \| Development Milestone
License Revenue [Line Items]
Milestone fee payments upon achievement of various development and commercialization	562,500,000
Transaction price of license											562,500,000
Abb Vie Collaboration And License Agreement \| Sales Based Milestones
License Revenue [Line Items]
Milestone fee payments upon achievement of various development and commercialization	$ 820,000,000.0
Transaction price of license											820,000,000.0
Neurimmune
License Revenue [Line Items]
Reimbursement of development costs											400,000	300,000
Period for sharing of research and development cost				2 years
Percentage of partnership in collaboration				50.00%
Neurimmune \| Research and Development [Member]
License Revenue [Line Items]
Reimbursement of development costs											200,000	$ 300,000
Maximum [Member]
License Revenue [Line Items]
Aggregate milestone payment for all the targets											$ 1,580,000,000
Maximum [Member] \| Neurimmune \| Research and Development [Member]
License Revenue [Line Items]
Reimbursement of development costs													$ 100,000
N A V Technology Platform [Member]
License Revenue [Line Items]
Number of commercial product candidates \| ProductCandidate											1
HCR [Member] \| Novartis Gene Therapies [Member] \| March 2014 License Agreement [Member]
License Revenue [Line Items]
Accounts receivable, current											$ 12,800,000

License and Collaboration Agreements - Schedule Of License and Royalty Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Other license and royalty revenue	$ 5,369	$ 12,936	$ 14,404
Total license and royalty revenue	470,347	154,567	35,233
Abb Vie Collaboration And License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalties on net sales of Zolgensma	370,000
Zolgensma Royalties [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalties on net sales of Zolgensma	$ 94,978	61,631	$ 20,829
Achievement Of Sales Based Milestone For Zolgensma [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalties on net sales of Zolgensma		$ 80,000

- Definition

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9038-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
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-Section 50
-Paragraph 5
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 280
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-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

+ Details

License and Collaboration Agreements - Summary of Changes in Balances of Receivables, Contract Assets and Deferred Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts receivable, net, current and non-current:
Balance, beginning of period	$ 46,266	$ 42,303	$ 31,599
Additions	472,347	158,682	39,203
Deductions	(483,912)	(154,719)	(28,499)
Balance, end of period	34,701	46,266	42,303
Contract assets:
Balance, beginning of period	350		750
Additions	1,074	350	1,000
Deductions	(350)		(1,750)
Balance, end of period	1,074	350
Deferred revenue, current and non-current:
Balance, beginning of period	4,232	3,333	3,933
Additions		1,124
Deductions	(899)	(225)	(600)
Balance, end of period	3,333	4,232	3,333
Revenue recognized during the period from:
Amounts included in deferred revenue at beginning of period	390		600
Performance obligations satisfied in previous periods	$ 98,575	$ 146,772	$ 26,689

License and Collaboration Agreements - Summary of Accounts Recerivable, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current accounts receivable:
Billed to customers	$ 365	$ 30,573
Unbilled	32,074	20,104
Allowance for credit losses		(7,678)
Current accounts receivable, net	32,439	42,999
Non-current accounts receivable:
Unbilled	6,020	3,267
Allowance for credit losses	(3,758)
Non-current accounts receivable, net	2,262	3,267
Total accounts receivable, net	$ 34,701	$ 46,266

License and Collaboration Agreements - Summary of Changes in Allowance For Credit Losses (Detail) - Accounts Receivable - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	$ 7,678
Provision for credit losses (recoveries)	(2,569)	$ 7,678
Write-offs	108
Ending Balance	3,758	$ 7,678
Changes in present value discount of receivables	(1,243)
Write-offs	$ (108)

- Definition

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

+ References + Details

License and Collaboration Agreements - Schedule Of License Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License Revenue		$ 3,500	$ 3,500
Interest income from licensing	$ 719	4,271	2,951
Novartis Gene Therapies [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total license and royalty revenue	94,978	145,131	24,329
Interest income from licensing	22	26	29
Zolgensma Royalties [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total license and royalty revenue	$ 94,978	61,631	$ 20,829
Achievement Of Sales Based Milestone For Zolgensma [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total license and royalty revenue		$ 80,000

- Definition

+ References

+ Details

License and Collaboration Agreements -Schedule of AbbVie Collaboration Agreement (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
License Revenue [Line Items]
Total license and royalty revenue	$ 470,347	$ 154,567	$ 35,233
Abb Vie Collaboration And License Agreement
License Revenue [Line Items]
Total license and royalty revenue	370,000
Reduction of research and development expense for costs reimbursable by AbbVie	$ 5,866

Stock-based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
	Sep. 16, 2015	Jan. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense			$ 67,900
Unrecognized stock-based compensation, weighted-average period			2 years 3 months 18 days
Proceeds from exercise of stock options			$ 4,281	$ 5,623	$ 7,062
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock units vested			0	0
Total intrinsic values vested					$ 1,800
2015 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of annual increase in number of shares available for future issuance			4.00%
Common stock shares authorized for issuance			13,911,954
Shares available for future grants			2,352,346
Stock options expiration date			10 years
Stock options vesting period			4 years
Stock plan expiration date			2025-06
Weighted-average fair values of options granted			$ 26.01	$ 23.82	$ 31.19
Exercise of stock options, Shares			404,263	434,534	796,847
Total intrinsic value of options exercised			$ 11,900	$ 11,500	$ 30,800
2015 Equity Incentive Plan [Member] \| Subsequent Event [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional shares to be issued		1,713,246
2015 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares authorized for issuance			998,683
Shares available for future grants			769,174
Share-based compensation arrangement by share-based payment award, description			The number of authorized shares reserved for issuance under the 2015 ESPP automatically increases on the first business day of each fiscal year
Share-based compensation arrangement by share-based payment award, percentage of outstanding stock minimum	1.00%
Common stock shares issued to participants			53,596	55,499	35,994
2015 Employee Stock Purchase Plan [Member] \| Subsequent Event [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional shares to be issued		428,311

Stock-based Compensation - Stock-Based Compensation Expense by Award Type (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 38,808	$ 31,949	$ 26,854
Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	35,320	31,178	25,964
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	2,835		257
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 653	$ 771	$ 633

Stock-based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 38,808	$ 31,949	$ 26,854
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	19,602	16,280	13,031
General and Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 19,206	$ 15,669	$ 13,823

Stock-based Compensation - Summary of Stock Option Activity (Detail) - 2014 and 2015 Equity Incentive Plan [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Shares Outstanding, Beginning Balance	6,361
Shares, Granted	1,437
Shares, Exercised	(404)
Shares, Cancelled or forfeited	(268)
Shares Outstanding, Ending Balance	7,126	6,361
Shares, Exercisable	4,566
Shares, Vested and expected to vest	7,126
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-average Exercise Price Outstanding, Beginning Balance	$ 31.21
Weighted-average Exercise Price, Granted	43.04
Weighted-average Exercise Price, Exercised	11.46
Weighted-average Exercise Price, Cancelled or forfeited	45.98
Weighted-average Exercise Price, Outstanding, Ending Balance	34.16	$ 31.21
Weighted-average Exercise Price, Exercisable	29.62
Weighted-average Exercise Price, Vested and expected to vest	$ 34.16
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-average Remaining Contractual Life (Years) Outstanding	7 years 2 months 12 days	7 years 6 months
Weighted-average Remaining Contractual Life (Years), Exercisable	6 years 2 months 12 days
Weighted-average Remaining Contractual Life (Years), Vested and expected to vest	7 years 2 months 12 days
Aggregate Intrinsic Value Outstanding	$ 41,128	$ 101,356
Aggregate Intrinsic Value, Exercisable	40,607
Aggregate Intrinsic Value, Vested and expected to vest	$ 41,128

Stock-based Compensation - Schedule of Fair Value of Options Granted on Weighted-Average Assumptions (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]
Expected volatility	68.00%	71.00%	74.00%
Expected term (years)	6 years	6 years	6 years 1 month 6 days
Risk-free interest rate	0.60%	1.40%	2.30%
Expected dividend yield	0.00%	0.00%	0.00%

Stock-based Compensation - Summary of Unvested RSUs Activity Under 2015 Plan (Details) - Restricted Stock Units (RSUs) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Granted	291,000
Vested	0	0
Forfeited	(14,000)
Unvested balance at December 31, 2021	277,000
Weighted-average Grant Date Fair Value, Granted	$ 43.67
Weighted-average Grant Date Fair Value, Forfeited	44.55
Weighted-average Grant Date Fair Value, Unvested Beginning Balance	$ 43.62

Retirement Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Employer matching contribution expense	$ 2.6	$ 2.2	$ 1.8

Income Taxes - Components of Income (Loss) Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
United States	$ 141,303	$ (105,960)	$ (97,435)
Foreign	(56)	(50)	(53)
Income (loss) before income taxes	$ 141,247	$ (106,010)	$ (97,488)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

Income Taxes - Components of the Provision For Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current:
Federal	$ 4,107
State	9,300	$ 5,240	$ (2,288)
Total current	13,407	5,240	(2,288)
Deferred:
Federal			(284)
State			(183)
Total deferred			(467)
Total income tax expense (benefit)	$ 13,407	$ 5,240	$ (2,755)

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Line Items]
Elimination of limitation in net operating losses deductions as percentage of current year taxable income, percentage		80.00%
Recovery period on qualified improvement of property		15 years
Current income tax benefit	$ 13,407,000	$ 5,240,000	$ (2,288,000)
Amortization Period	5 years
Federal statutory income tax rate, percent	21.00%
Increase (decrease) in valuation allowance	$ (32,200,000)	45,400,000
Research and development and orphan drug tax credit carryforwards	45,576,000	47,970,000
Net of unrecognized tax benefits	$ 100,000	$ 100,000	100,000
Tax credit carryforwards, expiration year	2035	2041
Reserve for uncertain tax positions placed against credit carryforwards	$ 100,000	$ 100,000	100,000
Reserve for uncertain tax positions placed against qualified expenses	$ 0	0	0
Unrecognized tax benefits period	12 months
Cumulative changes in ownership Interest percentage threshold, subject to annual limitation of NOL and tax credit carryforwards	50.00%
Ownership interest change period	3 years
Domestic Country [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards		0	44,700,000
Operating Loss Carryforwards Expiration Year	2034
Research and development and orphan drug tax credit carryforwards		45,600,000	48,000,000.0
U. S State Tax Authority [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards		59,900,000	$ 79,700,000
Operating Loss Carryforwards Expiration Year	2041
2018 Tax Year [Member]
Income Tax Disclosure [Line Items]
Current income tax benefit		$ (500,000)

Income Taxes - Schedule of Reconciliation of Effective Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal income tax expense (benefit) at statutory rate	$ 29,662	$ (22,263)	$ (20,473)
State income tax expense (benefit), net of federal tax effect	9,183	(11,495)	(15,323)
Research and development credits	(10,059)	(7,793)	(11,075)
Stock-based compensation	755	587	(2,134)
Executive compensation	1,511	202
Other non-deductible expenses and reconciling items	329	684	144
Change in corporate tax rates	14,772	109	130
Change in valuation allowance	(32,746)	45,209	45,976
Total income tax expense (benefit)	$ 13,407	$ 5,240	$ (2,755)

Income Taxes - Components of Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforwards	$ 3,981	$ 14,683
Research and development tax credits	45,576	47,970
Stock-based compensation	18,303	15,644
Lease liabilities	23,430	21,961
Liability related sale of future royalties	43,234	62,089
Accruals and other	6,230	7,370
Total deferred tax assets before valuation allowance	140,754	169,717
Valuation allowance	(110,756)	(142,907)
Total deferred tax assets	29,998	26,810
Deferred tax liabilities:
Unrealized gains on marketable securities		(163)
Right-of-use assets	(16,363)	(21,094)
Depreciation and amortization	(13,635)	(5,155)
Other		(398)
Total deferred tax liabilities	$ (29,998)	$ (26,810)

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
FOXKISER LLP [Member] \| Service Agreements [Member] \| Research and Development [Member]
Related Party Transaction [Line Items]
Related party transaction expense	$ 4.8	$ 4.8	$ 4.1

Net Income (Loss) Per Share - Computations of Basic and Diluted Net Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Basic net income (loss) per share:
Net income (loss)	$ 127,840	$ (111,250)	$ (94,733)
Shares used in computation:
Weighted-average common shares outstanding	42,438	37,281	36,690
Basic net income (loss) per share	$ 3.01	$ (2.98)	$ (2.58)
Diluted net income (loss) per share:
Net income (loss)	$ 127,840	$ (111,250)	$ (94,733)
Shares used in computation:
Weighted-average common shares outstanding	42,438	37,281	36,690
Weighted-average diluted common shares	43,913	37,281	36,690
Diluted net income (loss) per share	$ 2.91	$ (2.98)	$ (2.58)
Stock Option [Member]
Shares used in computation:
Weighted-average diluted common shares	1,467
Restricted Stock Units (RSUs)
Shares used in computation:
Weighted-average diluted common shares	2
Employee Stock Purchase Plan [Member]
Shares used in computation:
Weighted-average diluted common shares	6

Net Income (Loss) Per Share - Schedules for Computation of Diluted Weighted-Average Shares Outstanding (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted weighted average shares outstanding	5,187	6,380	5,561
Stock Options Issued and Outstanding [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted weighted average shares outstanding	4,939	6,361	5,544
Unvested Restricted Stock Units Outstanding [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted weighted average shares outstanding	248
Employee Stock Purchase Plan [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted weighted average shares outstanding		19	17

Supplemental Disclosures - Schedules of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued sublicense fees and royalties	$ 23,483	$ 12,160
Accrued personnel costs	19,849	13,155
Accrued external research and development expenses	11,783	9,738
Accrued income taxes payable	11,325	3,135
Accrued purchases of property and equipment	5,285	7,853
Accrued external general and administrative expenses	3,642	2,865
Other accrued expenses and current liabilities	744	176
Accrued expenses and other current liabilities	$ 76,111	$ 49,082