0001564590-22-017878 | 10-Q | XBRL Viewer

Print Document View Excel Document

License and Collaboration Agreements - Summary of Changes in Balances of Receivables, Contract Assets and Deferred Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accounts receivable, net, current and non-current:
Balance, beginning of period	$ 34,701	$ 46,266
Additions	28,057	18,718
Deductions	(33,652)	(21,086)
Balance, end of period	29,106	43,898
Contract assets:
Balance, beginning of period	1,074	350
Additions	602	649
Deductions	(550)	(350)
Balance, end of period	1,126	649
Deferred revenue, current and non-current:
Balance, beginning of period	3,333	4,232
Deductions		(108)
Balance, end of period	3,333	4,124
Revenue recognized during the period from:
Amounts included in deferred revenue at beginning of period		108
Performance obligations satisfied in previous periods	$ 21,541	$ 18,651

Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2022

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):

	Three Months Ended March 31,
	2022		2021
Cash and cash equivalents	$	191,873	$	291,482
Restricted cash		2,030		1,330
Total cash and cash equivalents and restricted cash	$	193,903	$	292,812

Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Non-marketable equity securities	$ 0		$ 0
Re measurements or impairment losses on non-marketable equity securities	$ 0	$ 0

Net Loss Per Share - Schedules for Computation of Diluted Weighted-Average Shares Outstanding (Detail) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted weighted average shares outstanding	8,680	7,630
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	8,172	7,346
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	471	254
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	37	30

Marketable Securities - Additional Information (Detail)	3 Months Ended
Marketable Securities - Additional Information (Detail)	Mar. 31, 2022 USD ($) Security	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)
Investments Debt And Equity Securities [Abstract]
Available for sale debt securities remaining maturities greater than three years	$ 0		$ 0
Number of investment grade fixed income debt security \| Security	132
Allowance for credit loss	$ 0		$ 0
Other-than-temporary impaired	$ 0	$ 0

Commitments and Contingencies - Additional Information (Detail) - University of Pennsylvania [Member] $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($) Installment
Penn Letter Agreement [Member]
Other Commitments [Line Items]
Amount payable to agreement	$ 20.0
Number of equal annual installments \| Installment	4
Related party transaction expense	$ 9.2
Present value of cost of revenue	17.3
Sublicense fees previously recognized	8.1
Amount payable to net present value discount	17.4
Penn Letter Agreement [Member] \| Accounts Payable and Accrued Expenses and Other Current Liabilities [Member]
Other Commitments [Line Items]
Amount payable to net present value discount	10.0
Penn Letter Agreement [Member] \| Other Liabilities [Member]
Other Commitments [Line Items]
Amount payable to net present value discount	7.4
Sublicense Fees Due Or Owed in Future [Member]
Other Commitments [Line Items]
Amount payable to agreement	8.0
Other Past or Future Obligations to Pay Sublicense Fees [Member]
Other Commitments [Line Items]
Amount payable to agreement	12.0
First Anniversary [Member]
Other Commitments [Line Items]
Amount payable to agreement	$ 3.0

License and Collaboration Agreements

3 Months Ended

Mar. 31, 2022

Organization Consolidation And Presentation Of Financial Statements [Abstract]

License and Collaboration Agreements

8. License and Collaboration Agreements

License and Royalty Revenue

As of March 31, 2022, 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):

	Three Months Ended March 31,
	2022		2021
Zolgensma royalties	$	21,539	$	18,263
Other license and royalty revenue		679		621
Total license and royalty revenue	$	22,218	$	18,884

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 March 31, 2022, 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) $537.8 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 the 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):

	Three Months Ended March 31,
	2022			2021
Accounts receivable, net, current and non-current:
Balance, beginning of period	$	34,701		$	46,266
Additions		28,057			18,718
Deductions		(33,652	)		(21,086	)
Balance, end of period	$	29,106		$	43,898

Contract assets:
Balance, beginning of period	$	1,074		$	350
Additions		602			649
Deductions		(550	)		(350	)
Balance, end of period	$	1,126		$	649

Deferred revenue, current and non-current:
Balance, beginning of period	$	3,333		$	4,232
Additions		—			—
Deductions		—			(108	)
Balance, end of period	$	3,333		$	4,124

Revenue recognized during the period from:
Amounts included in deferred revenue at beginning of period	$	—		$	108
Performance obligations satisfied in previous periods	$	21,541		$	18,651

Additions to accounts receivable during the periods presented consisted primarily of royalties on net sales of Zolgensma and the achievement of development milestones by licensees 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, as discussed further below. 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 March 31, 2022 and December 31, 2021 are included in other current assets on the consolidated balance sheets.

As of March 31, 2022, 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 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 royalties 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):

	March 31, 2022			December 31, 2021
Current accounts receivable:
Billed to customers	$	440		$	365
Unbilled		26,582			32,074
Allowance for credit losses		—			—
Current accounts receivable, net		27,022			32,439
Non-current accounts receivable:
Unbilled		5,937			6,020
Allowance for credit losses		(3,853	)		(3,758	)
Non-current accounts receivable, net		2,084			2,262
Total accounts receivable, net	$	29,106		$	34,701

The following table presents the changes in the allowance for credit losses related to accounts receivable and contract assets for the three months ended March 31, 2022 (in thousands):

	Allowance for Credit Losses
	Accounts Receivable		Contract Assets
Balance at December 31, 2021	$	3,758	$	—
Provision for credit losses		—		—
Changes in present value discount of receivables		95		—
Write-offs		—		—
Balance at March 31, 2022	$	3,853	$	—

The Company’s allowance for credit losses as of March 31, 2022 and December 31, 2021 was related solely to accounts receivable from Abeona Therapeutics Inc. (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 was zero and $0.6 million for the three months ended March 31, 2022 and 2021, respectively, and was related solely to changes in estimates regarding the collectability of the accounts receivable due from Abeona.

Zolgensma License with Novartis Gene Therapies

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 spinal muscular atrophy (SMA) in humans by in vivo gene therapy. 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.

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

	Three Months Ended March 31,
	2022		2021
Zolgensma royalties	$	21,539	$	18,263
Total license and royalty revenue	$	21,539	$	18,263

Interest income from licensing	$	5	$	6

As of March 31, 2022 and December 31, 2021, the Company had recorded total accounts receivable of $21.0 million and $26.6 million, respectively, from Novartis Gene Therapies under the March 2014 License, which consisted primarily of Zolgensma royalties receivable. The Zolgensma royalties receivable recorded as of March 31, 2022 included $14.3 million expected to be paid to HCR in accordance with the Royalty Purchase Agreement discussed in Note 6. 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 royalty revenues are adjusted, as necessary.

Settlement Agreement with Abeona Therapeutics

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 in damages and accrued interest payable 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 March 31, 2022 and December 31, 2021, the Company had recorded gross accounts receivable of $8.9 million and $8.8 million, respectively, from Abeona under the Settlement Agreement. The gross accounts receivable of $8.9 million as of March 31, 2022 consisted of current accounts receivable of $5.0 million for the payment due in November 2022, and non-current accounts receivable of $3.9 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 all 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 $3.9 million and $3.8 million as of March 31, 2022 and December 31, 2021, respectively, related to the non-current accounts receivable due from Abeona. The Company recorded a provision for credit losses of zero and $0.6 million for the three months ended March 31, 2022 and 2021, 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 periods related to the accretion of the present value discount on the non-current receivable from Abeona.

AbbVie Collaboration and License Agreement

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 of 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 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 intellectual property licensed to AbbVie includes the rights to certain patents, data, know-how and other rights developed and owned by the Company, as well as other intellectual property rights exclusively licensed by the Company from various third parties. As of March 31, 2022 and December 31, 2021, the transaction price of the AbbVie Collaboration Agreement was $370.0 million, which consisted solely of the up-front payment received 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. There were no changes in the transaction price of the AbbVie Collaboration Agreement, and no revenue was recognized, during the three months ended March 31, 2022.

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 and commercialization costs in accordance with its accounting policy for collaborative arrangements. Amounts owed to AbbVie for the Company’s share of development costs or commercialization costs incurred by AbbVie are recorded as research and development expense or general and administrative expense, respectively, in the period the costs are incurred. Amounts owed to the Company for AbbVie’s share of development costs or commercialization costs incurred by the Company are recorded as a reduction of research and development expense or general and administrative expense, respectively, 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 March 31, 2022 and December 31, 2021, the Company had recorded $3.1 million and $5.9 million, respectively, due from AbbVie for reimbursement of costs incurred for activities performed under AbbVie Collaboration Agreement, which is included in other current assets on the consolidated balance sheets.

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

	Three Months Ended
	March 31, 2022
Net cost reimbursement from AbbVie for collaboration activities included in:
Research and development expense	$	2,882
General and administrative expense		92
Total net cost reimbursement from AbbVie	$	2,974

Related Party Transactions

3 Months Ended

Mar. 31, 2022

Related Party Transactions

11. 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 were $1.2 million and $1.2 million for the three months ended March 31, 2022 and 2021, respectively, and were recorded as research and development expenses in the consolidated statements of operations and comprehensive loss.

Income Taxes

3 Months Ended

Mar. 31, 2022

Income Tax Disclosure [Abstract]

Income Taxes

10. Income Taxes

The Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets as of March 31, 2022 and December 31, 2021. 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 March 31, 2022 and December 31, 2021.

- 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

Marketable Securities - Summary of Company Marketable Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	$ 584,010	$ 505,846
Unrealized Gains	6	64
Unrealized Losses	(11,096)	(1,773)
Fair Value	572,920	504,137
U.S. Government and Agency Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	175,578	60,118
Unrealized Losses	(2,041)	(229)
Fair Value	173,537	59,889
Certificates of Deposit [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	3,664	2,936
Unrealized Gains		2
Unrealized Losses	(73)	(11)
Fair Value	3,591	2,927
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	404,768	442,792
Unrealized Gains	6	62
Unrealized Losses	(8,982)	(1,533)
Fair Value	$ 395,792	$ 441,321

Liability Related to Sale of Future Royalties (Tables)

3 Months Ended

Mar. 31, 2022

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
Balance at December 31, 2021	$	171,349
Zolgensma royalties paid to HCR		(13,586	)
Interest expense recognized		6,103
Balance at March 31, 2022		163,866
Current portion of liability related to sale of future royalties		(41,352	)
Liability related to sale of future royalties, non-current	$	122,514

Supplemental Disclosures - Schedules of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Payables And Accruals [Abstract]
Accrued income taxes payable	$ 12,672	$ 11,325
Accrued external research and development expenses	10,855	11,783
Accrued sublicense fees and royalties	9,057	23,483
Accrued personnel costs	7,852	19,849
Accrued purchases of property and equipment	4,042	5,285
Accrued external general and administrative expenses	3,607	3,642
Other accrued expenses and current liabilities	338	744
Accrued expenses and other current liabilities	$ 48,423	$ 76,111

Summary of Significant Accounting Policies - Summary of Reconciliation of Cash and Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Accounting Policies [Abstract]
Cash and cash equivalents	$ 191,873	$ 345,209	$ 291,482
Restricted cash	2,030	$ 2,030	1,330
Total cash and cash equivalents and restricted cash	$ 193,903		$ 292,812

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2022	Dec. 31, 2021
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.000	$ 0.000
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	42,982,000	42,831,000
Common stock, shares outstanding	42,982,000	42,831,000

License and Collaboration Agreements - Summary of Changes in Allowance For Credit Losses (Detail) - Accounts Receivable $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($)
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	$ 3,758
Changes in present value discount of receivables	95
Ending Balance	$ 3,853

- Definition

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

+ References + Details

Consolidated Statements of Stockholders' Equity (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)
Common Stock [Member]
Issuance of Stock, transaction costs	$ 14,194

Property and Equipment, Net (Tables)

3 Months Ended

Mar. 31, 2022

Property Plant And Equipment [Abstract]

Schedule of Property and Equipment

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

	March 31, 2022			December 31, 2021
Laboratory and manufacturing equipment	$	61,043		$	56,976
Computer equipment and software		4,545			4,268
Furniture and fixtures		6,839			6,804
Leasehold improvements		94,462			92,535
Total property and equipment		166,889			160,583
Accumulated depreciation and amortization		(31,625	)		(29,036	)
Property and equipment, net	$	135,264		$	131,547

License and Collaboration Agreements (Tables)

3 Months Ended

Mar. 31, 2022

Schedule Of License and Royalty Revenue

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

	Three Months Ended March 31,
	2022		2021
Zolgensma royalties	$	21,539	$	18,263
Other license and royalty revenue		679		621
Total license and royalty revenue	$	22,218	$	18,884

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

	Three Months Ended March 31,
	2022			2021
Accounts receivable, net, current and non-current:
Balance, beginning of period	$	34,701		$	46,266
Additions		28,057			18,718
Deductions		(33,652	)		(21,086	)
Balance, end of period	$	29,106		$	43,898

Contract assets:
Balance, beginning of period	$	1,074		$	350
Additions		602			649
Deductions		(550	)		(350	)
Balance, end of period	$	1,126		$	649

Deferred revenue, current and non-current:
Balance, beginning of period	$	3,333		$	4,232
Additions		—			—
Deductions		—			(108	)
Balance, end of period	$	3,333		$	4,124

Revenue recognized during the period from:
Amounts included in deferred revenue at beginning of period	$	—		$	108
Performance obligations satisfied in previous periods	$	21,541		$	18,651

Summary of Accounts Receivables, net

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

	March 31, 2022			December 31, 2021
Current accounts receivable:
Billed to customers	$	440		$	365
Unbilled		26,582			32,074
Allowance for credit losses		—			—
Current accounts receivable, net		27,022			32,439
Non-current accounts receivable:
Unbilled		5,937			6,020
Allowance for credit losses		(3,853	)		(3,758	)
Non-current accounts receivable, net		2,084			2,262
Total accounts receivable, net	$	29,106		$	34,701

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 three months ended March 31, 2022 (in thousands):

	Allowance for Credit Losses
	Accounts Receivable		Contract Assets
Balance at December 31, 2021	$	3,758	$	—
Provision for credit losses		—		—
Changes in present value discount of receivables		95		—
Write-offs		—		—
Balance at March 31, 2022	$	3,853	$	—

Schedule of AbbVie Collaboration Agreement

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

	Three Months Ended
	March 31, 2022
Net cost reimbursement from AbbVie for collaboration activities included in:
Research and development expense	$	2,882
General and administrative expense		92
Total net cost reimbursement from AbbVie	$	2,974

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):

	Three Months Ended March 31,
	2022		2021
Zolgensma royalties	$	21,539	$	18,263
Total license and royalty revenue	$	21,539	$	18,263

Interest income from licensing	$	5	$	6

Liability Related to Sale of Future Royalties

3 Months Ended

Mar. 31, 2022

6. Liability Related to Sale of Future Royalties

In December 2020, the Company entered into a royalty purchase agreement (the Royalty Purchase Agreement) with entities managed by Healthcare Royalty Management, LLC (collectively, 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, Inc. (formerly AveXis, Inc.) (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 March 31, 2022, the estimated effective interest rate under the agreement was 14.8%. 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
Balance at December 31, 2021	$	171,349
Zolgensma royalties paid to HCR		(13,586	)
Interest expense recognized		6,103
Balance at March 31, 2022		163,866
Current portion of liability related to sale of future royalties		(41,352	)
Liability related to sale of future royalties, non-current	$	122,514

License and Collaboration Agreements - Additional Information (Detail)			1 Months Ended		3 Months Ended
	May 31, 2020 USD ($)	Nov. 30, 2018 USD ($)	Nov. 30, 2021 USD ($)	Nov. 30, 2018 USD ($)	Mar. 31, 2022 USD ($) ProductCandidate	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jul. 31, 2020 USD ($)
License Revenue [Line Items]
Milestone payment upon commencement of clinical trials in humans					$ 537,800,000
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
Deferred revenue, current and non-current					3,333,000	$ 4,124,000	$ 3,333,000	$ 4,232,000
Provision for credit losses					0	565,000
Accounts receivable, current					27,022,000		32,439,000
Accounts receivable, net					2,084,000		2,262,000
Abeona Therapeutics Incorporation \| Contract Termination
License Revenue [Line Items]
Up-front and annual fees		$ 20,000,000.0		$ 20,000,000.0
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		370,000,000.0
Change in transaction price					0
Revenue recognized					0
Reimbursement of development costs					2,974,000
Abb Vie Collaboration And License Agreement \| Other Current Assets [Member]
License Revenue [Line Items]
Reimbursement of development costs					3,100,000		5,900,000
March 2014 License Agreement [Member] \| Novartis Gene Therapies [Member]
License Revenue [Line Items]
Accounts receivable					21,000,000.0		26,600,000
November Two Thousand Eighteen License Agreement \| Abeona Therapeutics Incorporation
License Revenue [Line Items]
License fee				$ 8,000,000.0
November Two Thousand Eighteen License Agreement \| Abeona Therapeutics Incorporation \| Contract Termination
License Revenue [Line Items]
Accounts receivable	$ 28,000,000.0								$ 33,600,000
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 percentage on unpaid balances under license agreement				1.50%
Settlement agreement payable					30,000,000.0
November Two Thousand Twenty One License Agreement \| Abeona Therapeutics Incorporation \| Contract Termination
License Revenue [Line Items]
Settlement agreement payable					20,000,000.0
November Two Thousand Twenty Two License Agreement \| Abeona Therapeutics Incorporation \| Contract Termination
License Revenue [Line Items]
Settlement agreement payable					5,000,000.0
November Two Thousand Twenty Four License Agreement \| Abeona Therapeutics Incorporation \| Contract Termination
License Revenue [Line Items]
Settlement agreement payable					5,000,000.0
Settlement Agreement \| Abeona Therapeutics Incorporation
License Revenue [Line Items]
Accounts receivable					8,900,000		8,800,000
Accounts receivable, current					5,000,000.0
Accounts receivable, net					3,900,000
Payments due from related party					5,000,000.0
Allowance for credit losses					3,900,000		3,800,000
Provision for credit losses					0	$ 600,000
Sales Based Milestones \| Abb Vie Collaboration And License Agreement
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		820,000,000.0
Development Milestone \| Abb Vie Collaboration And License Agreement
License Revenue [Line Items]
Milestone fee payments upon achievement of various development and commercialization			$ 562,500,000
Transaction price of license					562,500,000		$ 562,500,000
Maximum [Member]
License Revenue [Line Items]
Aggregate milestone payment for all the targets					$ 1,580,000
N A V Technology Platform [Member]
License Revenue [Line Items]
Number of commercial product candidates \| ProductCandidate					1
HCR [Member] \| March 2014 License Agreement [Member] \| Novartis Gene Therapies [Member]
License Revenue [Line Items]
Accounts receivable, current					$ 14,300,000

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets
Cash and cash equivalents	$ 191,873	$ 345,209
Marketable securities	202,261	112,230
Accounts receivable, net	27,022	32,439
Prepaid expenses	18,542	18,752
Other current assets	7,179	10,196
Total current assets	446,877	518,826
Marketable securities	370,659	391,907
Accounts receivable, net	2,084	2,262
Property and equipment, net	135,264	131,547
Operating lease right-of-use assets	59,925	60,904
Restricted cash	2,030	2,030
Other assets	8,529	6,428
Total assets	1,025,368	1,113,904
Current liabilities
Accounts payable	24,708	11,387
Accrued expenses and other current liabilities	48,423	76,111
Deferred revenue	3,333	3,333
Operating lease liabilities	2,121	1,752
Liability related to sale of future royalties	41,352	37,889
Total current liabilities	119,937	130,472
Operating lease liabilities	85,568	84,929
Liability related to sale of future royalties	122,514	133,460
Other liabilities	7,680	745
Total liabilities	335,699	349,606
Stockholders’ equity
Preferred stock; $0.0001 par value; 10,000 shares authorized, no shares issued and outstanding at March 31, 2022 and December 31, 2021
Common stock; $0.0001 par value; 100,000 shares authorized at March 31, 2022 and December 31, 2021; 42,982 and 42,831 shares issued and outstanding at March 31, 2022 and December 31, 2021, respectively	4	4
Additional paid-in capital	939,570	928,095
Accumulated other comprehensive loss	(11,950)	(2,569)
Accumulated deficit	(237,955)	(161,232)
Total stockholders’ equity	689,669	764,298
Total liabilities and stockholders’ equity	$ 1,025,368	$ 1,113,904

Nature of Business - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accumulated deficit	$ (237,955)	$ (161,232)
Cash, cash equivalents and marketable securities	$ 764,800

- Definition

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

+ References + Details

Stock-based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 10,800	$ 9,920
Research and Development Expense [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	5,670	5,031
General and Administrative Expense [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 5,130	$ 4,889

Supplemental Disclosures

3 Months Ended

Mar. 31, 2022

Payables And Accruals [Abstract]

Supplemental Disclosures

13. Supplemental Disclosures

Accrued Expenses and Other Current Liabilities

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

	March 31, 2022		December 31, 2021
Accrued income taxes payable	$	12,672	$	11,325
Accrued external research and development expenses		10,855		11,783
Accrued sublicense fees and royalties		9,057		23,483
Accrued personnel costs		7,852		19,849
Accrued purchases of property and equipment		4,042		5,285
Accrued external general and administrative expenses		3,607		3,642
Other accrued expenses and current liabilities		338		744
	$	48,423	$	76,111

Supplemental Disclosures of Non-cash Investing and Financing Activities

Purchases of property and equipment included in accounts payable and accrued expenses and other current liabilities were $5.4 million as of March 31, 2022, a net decrease of $4.7 million from December 31, 2021, and $13.3 million as of March 31, 2021, a net increase of $3.8 million from December 31, 2020.

Proceeds due to the Company for sales of non-marketable equity securities included in other current assets as of March 31, 2022 were $0.6 million. No such amounts were recorded as of March 31, 2021.

Marketable Securities

3 Months Ended

Mar. 31, 2022

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
March 31, 2022
U.S. government and agency securities	$	175,578	$	—	$	(2,041	)	$	173,537
Certificates of deposit		3,664		—		(73	)		3,591
Corporate bonds		404,768		6		(8,982	)		395,792
	$	584,010	$	6	$	(11,096	)	$	572,920

	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

As of March 31, 2022 and December 31, 2021, 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 March 31, 2022 and December 31, 2021, 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. 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. 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. Unrealized loss on available-for-sale securities, net, as presented in the statements of operations and comprehensive loss consisted of the following (in thousands):

	Three Months Ended March 31,
	2022			2021
Unrealized loss before reclassifications	$	(9,381	)	$	(1,001	)
Realized gains reclassified to investment income		—			(7	)
Income tax expense		—			—
Unrealized loss on available-for-sale securities, net	$	(9,381	)	$	(1,008	)

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
March 31, 2022
U.S. government and agency securities	$	173,537	$	(2,041	)	$	—	$	—		$	173,537	$	(2,041	)
Certificates of deposit		3,591		(73	)		—		—			3,591		(73	)
Corporate bonds		318,265		(7,503	)		72,721		(1,479	)		390,986		(8,982	)
	$	495,393	$	(9,617	)	$	72,721	$	(1,479	)	$	568,114	$	(11,096	)

	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	)

As of March 31, 2022, available-for-sale debt securities held by the Company which were in an unrealized loss position consisted of 132 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 record an allowance for credit losses on its available-for-sale debt securities as of March 31, 2022 or December 31, 2021. The Company did not recognize any impairment or credit losses on available-for-sale debt securities during the three months ended March 31, 2022 and 2021.

Property and Equipment Net - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Property Plant And Equipment [Line Items]
Total property and equipment	$ 166,889	$ 160,583
Accumulated depreciation and amortization	(31,625)	(29,036)
Property and equipment, net	135,264	131,547
Laboratory and Manufacturing Equipment [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	61,043	56,976
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	4,545	4,268
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	6,839	6,804
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	$ 94,462	$ 92,535

Property and Equipment, Net

3 Months Ended

Mar. 31, 2022

Property Plant And Equipment [Abstract]

Property and Equipment, Net

5. Property and Equipment, Net

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

	March 31, 2022			December 31, 2021
Laboratory and manufacturing equipment	$	61,043		$	56,976
Computer equipment and software		4,545			4,268
Furniture and fixtures		6,839			6,804
Leasehold improvements		94,462			92,535
Total property and equipment		166,889			160,583
Accumulated depreciation and amortization		(31,625	)		(29,036	)
Property and equipment, net	$	135,264		$	131,547

License and Collaboration Agreements - Summary of Accounts Recerivable, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current accounts receivable:
Billed to customers	$ 440	$ 365
Unbilled	26,582	32,074
Current accounts receivable, net	27,022	32,439
Non-current accounts receivable:
Unbilled	5,937	6,020
Allowance for credit losses	(3,853)	(3,758)
Non-current accounts receivable, net	2,084	2,262
Total accounts receivable, net	$ 29,106	$ 34,701

Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2022

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
March 31, 2022
U.S. government and agency securities	$	175,578	$	—	$	(2,041	)	$	173,537
Certificates of deposit		3,664		—		(73	)		3,591
Corporate bonds		404,768		6		(8,982	)		395,792
	$	584,010	$	6	$	(11,096	)	$	572,920

	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

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

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

	Three Months Ended March 31,
	2022			2021
Unrealized loss before reclassifications	$	(9,381	)	$	(1,001	)
Realized gains reclassified to investment income		—			(7	)
Income tax expense		—			—
Unrealized loss on available-for-sale securities, net	$	(9,381	)	$	(1,008	)

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
March 31, 2022
U.S. government and agency securities	$	173,537	$	(2,041	)	$	—	$	—		$	173,537	$	(2,041	)
Certificates of deposit		3,591		(73	)		—		—			3,591		(73	)
Corporate bonds		318,265		(7,503	)		72,721		(1,479	)		390,986		(8,982	)
	$	495,393	$	(9,617	)	$	72,721	$	(1,479	)	$	568,114	$	(11,096	)

	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	)

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities
Net loss	$ (76,723)	$ (50,139)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation expense	10,800	9,920
Depreciation and amortization	2,591	1,929
Provision for credit losses	0	565
Net amortization of premiums on marketable debt securities	1,460	1,288
Net gains on investments		(7)
Imputed interest income from licensing	(94)	(29)
Non-cash interest expense	54	3,786
Other non-cash adjustments	(43)	(154)
Changes in operating assets and liabilities
Accounts receivable	5,689	1,618
Prepaid expenses	210	(3,334)
Other current assets	3,042	(873)
Operating lease right-of-use assets	979	1,232
Other assets	(2,101)	(3,789)
Accounts payable	16,755	278
Accrued expenses and other current liabilities	(26,473)	(10,544)
Operating lease liabilities	1,008	4,244
Other liabilities	6,935	(38)
Net cash used in operating activities	(55,911)	(44,047)
Cash flows from investing activities
Purchases of marketable debt securities	(129,486)	(233,627)
Maturities of marketable debt securities	49,862	50,465
Purchases of property and equipment	(10,967)	(31,021)
Net cash used in investing activities	(90,591)	(214,183)
Cash flows from financing activities
Proceeds from exercise of stock options	337	1,292
Taxes paid related to net settlement of stock-based awards	(284)
Proceeds from issuance of common stock under employee stock purchase plan	622	627
Proceeds from public offering of common stock, net of underwriting discounts and commissions		216,438
Issuance costs for public offering of common stock		(251)
Repayments under liability related to sale of future royalties, net of imputed interest	(7,509)	(6,555)
Transaction costs for sale of future royalties		(265)
Net cash provided by (used in) financing activities	(6,834)	211,286
Net decrease in cash and cash equivalents and restricted cash	(153,336)	(46,944)
Cash and cash equivalents and restricted cash
Beginning of period	347,239	339,756
End of period	$ 193,903	$ 292,812

Commitments and Contingencies

3 Months Ended

Mar. 31, 2022

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

7. Commitments and Contingencies

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) (the Penn License) 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. In March 2022, the Company and Penn entered into a letter agreement (the Penn Letter Agreement) pursuant to which the Company will pay to Penn a total of $20.0 million, consisting of (i) $8.0 million to satisfy payment of any sublicense fees due or owed in the future under the Penn License as a result of the Company’s collaboration and license agreement with AbbVie Global Enterprises Ltd., which is payable within 30 days of the effective date of the Penn Letter Agreement, and (ii) $12.0 million to satisfy any other past or future obligations of the Company to pay sublicense fees under the Penn License, which is payable in four equal annual installments of $3.0 million beginning on first anniversary of the effective date of the Penn Letter Agreement. The Penn Letter Agreement amended the Penn License to remove the Company’s obligations to pay sublicense fees under the license agreement. The Company will continue to be obligated to pay Penn royalties on net sales of licensed products, milestone fees and reimbursement of certain patent maintenance costs in accordance with the Penn License.

In connection with the execution of the Penn Letter Agreement, the Company’s royalty obligations under its March 2009 license agreement with GlaxoSmithKline LLC (GSK) (the GSK License) were assigned by GSK to Penn. Beginning upon the effective date of the Penn Letter Agreement in March 2022, any royalties payable by the Company under the GSK License will be paid to Penn rather than GSK. The Company will continue to be obligated to pay GSK sublicense fees and reimbursement of certain patent maintenance costs in accordance with the GSK License.

The Company recognized a charge of $9.2 million as cost of revenues during the three months ended March 31, 2022 related to the execution of Penn Letter Agreement, which consisted of $17.3 million representing the present value of the $20.0 million payable under the Penn Letter Agreement, less $8.1 million in sublicense fees previously recognized as expense by the Company in prior periods and accrued as liabilities prior to the effectiveness of the Penn Letter Agreement. The present value discount is accreted as interest expense over the contractual payment period using the effective interest method. In addition to other amounts payable under the Penn License, as of March 31, 2022, the Company had recorded a total of $17.4 million payable to Penn under the Penn Letter Agreement, net of present value discount, of which $10.0 million was included in accounts payable and accrued expenses and other current liabilities and $7.4 million was included in other liabilities on the consolidated balance sheet.

License and Collaboration Agreements -Schedule of AbbVie Collaboration Agreement (Detail) - Abb Vie Collaboration And License Agreement $ in Thousands	Mar. 31, 2022 USD ($)
Net cost reimbursement from AbbVie for collaboration activities included in:
Reimbursement of development costs	$ 2,974
Research and Development Expense [Member]
Net cost reimbursement from AbbVie for collaboration activities included in:
Reimbursement of development costs	2,882
General and Administrative Expense [Member]
Net cost reimbursement from AbbVie for collaboration activities included in:
Reimbursement of development costs	$ 92

- Definition

The aggregate amount of receivables to be collected from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth, at the financial statement date. which are usually due within one year (or one business cycle).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(C))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(11))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(B))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3)(a)(2))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=124098289&loc=d3e6676-107765

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(1))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

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	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Shares Outstanding, Beginning Balance	7,126
Shares, Granted	1,224
Shares, Exercised	(80)
Shares, Cancelled or forfeited	(98)
Shares Outstanding, Ending Balance	8,172	7,126
Shares, Exercisable	5,028
Shares, Vested and expected to vest	8,172
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-average Exercise Price Outstanding, Beginning Balance	$ 34.16
Weighted-average Exercise Price, Granted	33.93
Weighted-average Exercise Price, Exercised	4.61
Weighted-average Exercise Price, Cancelled or forfeited	38.57
Weighted-average Exercise Price, Outstanding, Ending Balance	34.37	$ 34.16
Weighted-average Exercise Price, Exercisable	31.52
Weighted-average Exercise Price, Vested and expected to vest	$ 34.37
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-average Remaining Contractual Life (Years) Outstanding	7 years 1 month 6 days	6 years 9 months 18 days
Weighted-average Remaining Contractual Life (Years), Exercisable	6 years
Weighted-average Remaining Contractual Life (Years), Vested and expected to vest	7 years 1 month 6 days
Aggregate Intrinsic Value Outstanding	$ 40,352	$ 41,128
Aggregate Intrinsic Value, Exercisable	39,522
Aggregate Intrinsic Value, Vested and expected to vest	$ 40,352

Stock-based Compensation

3 Months Ended

Mar. 31, 2022

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-based Compensation

9. Stock-based Compensation

In January 2022, the Board of Directors authorized an additional 1,713,246 shares to be issued under the 2015 Equity Incentive Plan (the 2015 Plan). As of March 31, 2022, the total number of shares of common stock authorized for issuance under the 2015 Plan and the 2014 Stock Plan (the 2014 Plan) was 15,625,200, of which 2,693,341 remained available for future grants under the 2015 Plan.

Stock-based Compensation Expense

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

	Three Months Ended March 31,
	2022		2021
Stock options	$	9,267	$	9,015
Restricted stock units		1,254		679
Employee stock purchase plan		279		226
	$	10,800	$	9,920

As of March 31, 2022, the Company had $88.9 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 2.7 years.

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

	Three Months Ended March 31,
	2022		2021
Research and development	$	5,670	$	5,031
General and administrative		5,130		4,889
	$	10,800	$	9,920

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, 2021		7,126		$	34.16		6.8	$	41,128
Granted		1,224		$	33.93
Exercised		(80	)	$	4.61
Cancelled or forfeited		(98	)	$	38.57
Outstanding at March 31, 2022		8,172		$	34.37		7.1	$	40,352
Exercisable at March 31, 2022		5,028		$	31.52		6.0	$	39,522
Vested and expected to vest at March 31, 2022		8,172		$	34.37		7.1	$	40,352

(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 three months ended March 31, 2022 was $20.37. During the three months ended March 31, 2022, the total number of stock options exercised was 80,123, resulting in total proceeds of $0.4 million. The total intrinsic value of options exercised during the three months ended March 31, 2022 was $1.8 million.

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, 2021		277		$	43.62
Granted		265		$	33.92
Vested		(61	)	$	44.94
Forfeited		(10	)	$	38.80
Unvested balance at March 31, 2022		471		$	38.10

The total intrinsic value of restricted stock units vested during the three months ended March 31, 2022 was $2.0 million. No restricted stock units vested during the three months ended March 31, 2021.

Employee Stock Purchase Plan

In January 2022, the Board of Directors authorized an additional 428,311 shares to be issued under the 2015 ESPP. As of March 31, 2022, the total number of shares of common stock authorized for issuance under the 2015 ESPP was 1,426,994, of which 1,175,112 remained available for future issuance. During the three months ended March 31, 2022, 22,373 shares of common stock were issued under the 2015 ESPP.

Fair Value of Financial Instruments

3 Months Ended

Mar. 31, 2022

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
March 31, 2022
Cash equivalents:
Money market mutual funds	$	—	$	124,116	$	—	$	124,116
Total cash equivalents		—		124,116		—		124,116
Marketable securities:
U.S. government and agency securities		—		173,537		—		173,537
Certificates of deposit		—		3,591		—		3,591
Corporate bonds		—		395,792		—		395,792
Total marketable securities		—		572,920		—		572,920
Total cash equivalents and marketable securities	$	—	$	697,036	$	—	$	697,036

	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

Management estimates that the carrying values 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. Certain non-current payables reported as other liabilities on the consolidated balance sheets are recorded at their present values using a discount rate that is based on prevailing market rates and the credit profile of the Company 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 March 31, 2022 to determine the present value of these receivables and liabilities. Accordingly, management estimates that the carrying values of its non-current accounts receivable and other liabilities approximate 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 6, the carrying value of the liability related to the sale of future royalties is based on the Company’s estimate of future royalties 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 March 31, 2022 and December 31, 2021, the Company did not hold any non-marketable equity securities. No remeasurements or impairment losses were recorded on non-marketable equity securities during the three months ended March 31, 2022 and 2021.

- 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

License and Collaboration Agreements - Schedule Of License Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
License Revenue [Line Items]
Interest income from licensing	$ 94	$ 29
Novartis Gene Therapies [Member]
License Revenue [Line Items]
Total license and royalty revenue	21,539	18,263
Interest income from licensing	5	6
Zolgensma Royalties [Member]
License Revenue [Line Items]
Total license and royalty revenue	$ 21,539	$ 18,263

- 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
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130545-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-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
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130543-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9054-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9031-108599

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-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 - Schedule Of License and Royalty Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
License Revenue [Line Items]
Other license and royalty revenue	$ 679	$ 621
Total license and royalty revenue	22,218	18,884
Zolgensma Royalties [Member]
License Revenue [Line Items]
Zolgensma royalties	$ 21,539	$ 18,263

- Definition

+ References

+ Details

Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2022

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
March 31, 2022
Cash equivalents:
Money market mutual funds	$	—	$	124,116	$	—	$	124,116
Total cash equivalents		—		124,116		—		124,116
Marketable securities:
U.S. government and agency securities		—		173,537		—		173,537
Certificates of deposit		—		3,591		—		3,591
Corporate bonds		—		395,792		—		395,792
Total marketable securities		—		572,920		—		572,920
Total cash equivalents and marketable securities	$	—	$	697,036	$	—	$	697,036

	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

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
FOXKISER LLP [Member] \| Service Agreements [Member] \| Research and Development Expense [Member]
Related Party Transaction [Line Items]
Related party transaction expense	$ 1.2	$ 1.2

Net Loss Per Share

3 Months Ended

Mar. 31, 2022

Earnings Per Share [Abstract]

Net Income (Loss) Per Share

12. Net Loss Per Share

Since the Company incurred net losses for the three months ended March 31, 2022 and 2021, 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):

	Three Months Ended March 31,
	2022		2021
Stock options issued and outstanding		8,172		7,346
Unvested restricted stock units outstanding		471		254
Employee stock purchase plan		37		30
		8,680		7,630

Supplemental Disclosures (Tables)

3 Months Ended

Mar. 31, 2022

Payables And Accruals [Abstract]

Schedules of Accrued Expenses and Other Current Liabilities

Accrued Expenses and Other Current Liabilities

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

	March 31, 2022		December 31, 2021
Accrued income taxes payable	$	12,672	$	11,325
Accrued external research and development expenses		10,855		11,783
Accrued sublicense fees and royalties		9,057		23,483
Accrued personnel costs		7,852		19,849
Accrued purchases of property and equipment		4,042		5,285
Accrued external general and administrative expenses		3,607		3,642
Other accrued expenses and current liabilities		338		744
	$	48,423	$	76,111

Liability Related to Sale of Future Royalties - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Liability Related To Sale Of Future Royalties [Line Items]
Repurchase of call option amount	$ 300,000
Interest expense	6,130	$ 6,702
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	14.80%
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
HCR [Member] \| Royalty Agreements
Liability Related To Sale Of Future Royalties [Line Items]
Purchase Agreement	$ 200,000

Stock-based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	Jan. 31, 2022	Mar. 31, 2022	Mar. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense		$ 88.9
Unrecognized stock-based compensation, weighted-average period		2 years 8 months 12 days
Proceeds from stock options exercised including unsettled options		$ 0.4
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock units vested		61,000	0
Total intrinsic values vested		$ 2.0
2015 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional shares to be issued	1,713,246
Common stock shares authorized for issuance		15,625,200
Shares available for future grants		2,693,341
Weighted-average fair values of options granted		$ 20.37
Exercise of stock options, Shares		80,123
Total intrinsic value of options exercised		$ 1.8
2015 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional shares to be issued	428,311
Common stock shares authorized for issuance		1,426,994
Shares available for future grants		1,175,112
Common stock shares issued to participants		22,373

Stock-based Compensation - Summary of Unvested RSUs Activity Under 2015 Plan (Detail) - Restricted Stock Units (RSUs) - $ / shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested balance at December 31, 2021	277,000
Shares, Granted	265,000
Vested	(61,000)	0
Forfeited	(10,000)
Unvested balance at March 31, 2022	471,000
Weighted-average Grant Date Fair Value, Unvested Beginning Balance	$ 43.62
Weighted-average Grant Date Fair Value, Granted	33.92
Weighted-average Grant Date Fair Value, Vested	44.94
Weighted-average Grant Date Fair Value, Forfeited	38.80
Weighted-average Grant Date Fair Value, Unvested Beginning Balance	$ 38.10

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2022

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 are unaudited and have been prepared in conformity with accounting principles generally accepted in the United States of America (GAAP). The interim unaudited consolidated financial statements have been prepared on the same basis as the annual audited consolidated financial statements as of and for the year ended December 31, 2021 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021, which was filed with the SEC on March 1, 2022. Certain information and footnote disclosures required by GAAP which are normally included in the Company’s annual consolidated financial statements have been omitted pursuant to SEC rules and regulations for interim reporting. In the opinion of management, the accompanying consolidated financial statements reflect all adjustments, which are normal and recurring in nature, necessary for fair financial statement presentation.

The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full year, any other interim periods, or any future year or period. These interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements as of and for the year ended December 31, 2021, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021.

The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

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 remains 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.

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):

	Three Months Ended March 31,
	2022		2021
Cash and cash equivalents	$	191,873	$	291,482
Restricted cash		2,030		1,330
Total cash and cash equivalents and restricted cash	$	193,903	$	292,812

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 8 for further information regarding the allowance for credit losses related to accounts receivable.

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. Accounting Standards Codification (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.

Net Loss Per Share

Basic net loss per share is calculated by dividing net loss applicable to common stockholders by the weighted-average common shares outstanding during the period, without consideration for common stock equivalents. Diluted net 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 loss per share until the contingency has been fully met. For purposes of the diluted net loss per share calculation, common stock equivalents are excluded from the calculation of diluted net loss per share if their effect would be anti-dilutive.

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 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 determined the 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 has been effected in the accompanying consolidated statement of cash flows for the three months ended March 31, 2021, and will be effected in connection with its future filings of Form 10-Q for the interim periods ended June 30, 2022 and September 30, 2022. The accompanying consolidated statement of cash flows for the three months ended March 31, 2021 reflects the as corrected impact of correcting the error, resulting in an increase in net cash used in operating activities and a corresponding increase in net cash provided by financing activities of $2.9 million as compared to the previously issued interim financial statements for the period ended March 31, 2021.

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Revenues
Revenues	$ 22,218	$ 18,884
Operating Expenses
Cost of revenues	15,717	4,851
Research and development	55,627	39,722
General and administrative	22,318	17,838
Credit losses and other	83	515
Total operating expenses	93,745	62,926
Loss from operations	(71,527)	(44,042)
Other Income (Expense)
Interest income from licensing	94	29
Investment income	799	580
Interest expense	(6,130)	(6,702)
Total other income (expense)	(5,237)	(6,093)
Loss before income taxes	(76,764)	(50,135)
Income Tax Benefit (Expense)	41	(4)
Net loss	(76,723)	(50,139)
Other Comprehensive Loss
Unrealized loss on available-for-sale securities, net	(9,381)	(1,008)
Total other comprehensive loss	(9,381)	(1,008)
Comprehensive loss	$ (86,104)	$ (51,147)
Net loss per share, basic and diluted	$ (1.79)	$ (1.20)
Weighted-average common shares outstanding, basic and diluted	42,944	41,819
License and royalty [Member]
Revenues
Revenues	$ 22,218	$ 18,884

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2022

Accounting Policies [Abstract]

Basis of Presentation and Principles of Consolidation

Use of Estimates

Restricted Cash

	Three Months Ended March 31,
	2022		2021
Cash and cash equivalents	$	191,873	$	291,482
Restricted cash		2,030		1,330
Total cash and cash equivalents and restricted cash	$	193,903	$	292,812

Accounts Receivable

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.

Net Loss Per Share

Correction of Previously Issued Financial Statements

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	9 Months Ended
	Mar. 31, 2021	Jun. 30, 2021	Sep. 30, 2021
Royalty Agreements
Significant Accounting Policies [Line Items]
Non Cash Interest Expense	$ 2.9	$ 9.1	$ 15.3

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	Mar. 31, 2022	Dec. 31, 2021
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 495,393	$ 447,199
Less than 12 Months, Unrealized Losses	(9,617)	(1,773)
12 Months or Greater, Fair Value	72,721
12 Months or Greater, Unrealized Losses	(1,479)
Total, Fair Value	568,114	447,199
Total, Unrealized Losses	(11,096)	(1,773)
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	318,265	385,115
Less than 12 Months, Unrealized Losses	(7,503)	(1,533)
12 Months or Greater, Fair Value	72,721
12 Months or Greater, Unrealized Losses	(1,479)
Total, Fair Value	390,986	385,115
Total, Unrealized Losses	(8,982)	(1,533)
U.S. Government and Agency Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	173,537	59,889
Less than 12 Months, Unrealized Losses	(2,041)	(229)
Total, Fair Value	173,537	59,889
Total, Unrealized Losses	(2,041)	(229)
Certificates of Deposit [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	3,591	2,195
Less than 12 Months, Unrealized Losses	(73)	(11)
Total, Fair Value	3,591	2,195
Total, Unrealized Losses	$ (73)	$ (11)

Liability Related to Sale of Future Royalties -Schedule of Activity Within Liability Related to Sale of Future Royalties (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Liability Related To Sale Of Future Royalties [Line Items]
Current portion of liability related to sale of future royalties	$ (41,352)	$ (37,889)
Liability related to sale of future royalties	122,514	$ 133,460
Royalty Agreements
Liability Related To Sale Of Future Royalties [Line Items]
Balance at December 31, 2021	171,349
Zolgensma royalties paid to HCR	(13,586)
Interest expense recognized	6,103
Balance at March 31, 2022	163,866
Current portion of liability related to sale of future royalties	(41,352)
Liability related to sale of future royalties	$ 122,514

Stock-based Compensation - Stock-Based Compensation Expense by Award Type (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 10,800	$ 9,920
Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	9,267	9,015
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	1,254	679
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 279	$ 226

Fair Value of Financial Instruments - Schedule of Fair Value of Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Marketable securities:
Fair Value	$ 572,920	$ 504,137
Cash Equivalents and Marketable Securities [Member]
Marketable securities:
Total cash equivalents and marketable securities	697,036	740,477
Corporate Bonds [Member]
Marketable securities:
Fair Value	395,792	441,321
Cash Equivalents [Member]
Cash equivalents:
Total cash equivalents	124,116	236,340
US Government Agencies And Agency Securities
Marketable securities:
Fair Value	173,537	59,889
Certificates of Deposit [Member]
Marketable securities:
Fair Value	3,591	2,927
Money Market Mutual Funds [Member] \| Cash Equivalents [Member]
Cash equivalents:
Total cash equivalents	124,116	236,340
Significant Other Observable Inputs (Level 2) [Member]
Marketable securities:
Fair Value	572,920	504,137
Significant Other Observable Inputs (Level 2) [Member] \| Cash Equivalents and Marketable Securities [Member]
Marketable securities:
Total cash equivalents and marketable securities	697,036	740,477
Significant Other Observable Inputs (Level 2) [Member] \| Corporate Bonds [Member]
Marketable securities:
Fair Value	395,792	441,321
Significant Other Observable Inputs (Level 2) [Member] \| Cash Equivalents [Member]
Cash equivalents:
Total cash equivalents	124,116	236,340
Significant Other Observable Inputs (Level 2) [Member] \| US Government Agencies And Agency Securities
Marketable securities:
Fair Value	173,537	59,889
Significant Other Observable Inputs (Level 2) [Member] \| Certificates of Deposit [Member]
Marketable securities:
Fair Value	3,591	2,927
Significant Other Observable Inputs (Level 2) [Member] \| Money Market Mutual Funds [Member] \| Cash Equivalents [Member]
Cash equivalents:
Total cash equivalents	$ 124,116	$ 236,340

Nature of Business

3 Months Ended

Mar. 31, 2022

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 March 31, 2022, 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 March 31, 2022, the Company had generated an accumulated deficit of $238.0 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 March 31, 2022, the Company had cash, cash equivalents and marketable securities of $764.8 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.

Supplemental Disclosures - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Payables And Accruals [Abstract]
Purchases of property and equipment included in accounts payable and accrued expenses and other current liabilities	$ 5,400,000	$ 13,300,000
Increase (decrease) in purchases of property and equipment included in accounts payable and accrued expenses and other current liabilities	(4,700,000)	3,800,000
Proceeds due to Company for sales of non-marketable equity securities	$ 600,000	$ 0

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional paid in capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
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	1,292		1,292
Exercise of stock options, Shares		111
Issuance of common stock under employee stock purchase plan	627		627
Issuance of common stock under employee stock purchase plan, shares		19
Stock-based compensation expense	9,920		9,920
Unrealized loss on available-for-sale securities, net	(1,008)			(1,008)
Net loss	(50,139)				(50,139)
Balances at Mar. 31, 2021	554,504	$ 4	895,079	(1,368)	(339,211)
Balances (Shares) at Mar. 31, 2021		42,505
Balances at Dec. 31, 2021	764,298	$ 4	928,095	(2,569)	(161,232)
Balances (Shares) at Dec. 31, 2021		42,831
Vesting of restricted stock units, net of tax	(284)		(284)
Vesting of restricted stock units, Shares		52
Exercise of stock options	337		337
Exercise of stock options, Shares		76
Issuance of common stock under employee stock purchase plan	622		622
Issuance of common stock under employee stock purchase plan, shares		22
Stock-based compensation expense	10,800		10,800
Unrealized loss on available-for-sale securities, net	(9,381)			(9,381)
Net loss	(76,723)				(76,723)
Balances at Mar. 31, 2022	$ 689,669	$ 4	$ 939,570	$ (11,950)	$ (237,955)
Balances (Shares) at Mar. 31, 2022		42,982

Marketable Securities - Summary of unrealized loss on available-for-sale securities, net, presented in the statements of operations and comprehensive loss (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Investments Debt And Equity Securities [Abstract]
Unrealized loss before reclassifications	$ (9,381)	$ (1,001)
Realized gains reclassified to investment income		(7)
Unrealized loss on available-for-sale securities, net	$ (9,381)	$ (1,008)

Net Loss Per Share (Tables)

3 Months Ended

Mar. 31, 2022

Earnings Per Share [Abstract]

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):

	Three Months Ended March 31,
	2022		2021
Stock options issued and outstanding		8,172		7,346
Unvested restricted stock units outstanding		471		254
Employee stock purchase plan		37		30
		8,680		7,630

Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2022

Stock-Based Compensation Expense by Award Type

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

	Three Months Ended March 31,
	2022		2021
Stock options	$	9,267	$	9,015
Restricted stock units		1,254		679
Employee stock purchase plan		279		226
	$	10,800	$	9,920

Stock-Based Compensation Expense

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

	Three Months Ended March 31,
	2022		2021
Research and development	$	5,670	$	5,031
General and administrative		5,130		4,889
	$	10,800	$	9,920

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, 2021		277		$	43.62
Granted		265		$	33.92
Vested		(61	)	$	44.94
Forfeited		(10	)	$	38.80
Unvested balance at March 31, 2022		471		$	38.10

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, 2021		7,126		$	34.16		6.8	$	41,128
Granted		1,224		$	33.93
Exercised		(80	)	$	4.61
Cancelled or forfeited		(98	)	$	38.57
Outstanding at March 31, 2022		8,172		$	34.37		7.1	$	40,352
Exercisable at March 31, 2022		5,028		$	31.52		6.0	$	39,522
Vested and expected to vest at March 31, 2022		8,172		$	34.37		7.1	$	40,352

(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.