0000950170-24-122330 | 10-Q | XBRL Viewer

Leases	9 Months Ended
Sep. 30, 2024
Leases [Abstract]
Leases	6. Leases New York Sublease In May 2016, the Company entered into an operating lease for office space in New York, New York (the New York Lease), which has since been amended to include additional office space and extend the term of the lease. The lease term commenced in July 2016 and expires in April 2027. In March 2024, the Company entered into an agreement to sublease its office space under the New York Lease (the New York Sublease) to a third-party subtenant. The sublease term commenced in April 2024 and will expire in April 2027 concurrent with the expiration of the New York Lease. Monthly payments under the New York Sublease commenced in July 2024 and escalate annually in accordance with the sublease agreement. As of September 30, 2024, total undiscounted future minimum lease payments to be received by the Company over the term of the New York Sublease were $1.3 million. The Company recognized sublease income of $0.1 million and $0.2 million under the New York Sublease during the three and nine months ended September 30, 2024, respectively. The New York Sublease is classified as an operating lease and the Company was not relieved of its primary obligation under the New York Lease. The Company continues to account for the New York Lease as it did prior to the commencement of the sublease. As a result of the New York Sublease, the Company determined an impairment indicator was present as of March 31, 2024 related to the long-lived asset group subject to the sublease, which included the right-of-use asset under the New York Lease, leasehold improvements and other property and equipment allocable to the New York Sublease. The Company concluded the carrying value of the asset group as of March 31, 2024 was not recoverable, as it exceeded the sum of the estimated undiscounted cash flows to be generated by the assets over their remaining lives. The Company estimated the fair value of the asset group as of March 31, 2024 using a discounted cash flow method, which incorporated unobservable inputs including the net identifiable cash flows over the term of the New York Sublease and an estimated borrowing rate of a market participant subtenant. The estimated fair value of the asset group as of March 31, 2024 represents a Level 3 nonrecurring fair value measurement. The Company concluded the carrying value of the asset group of $3.4 million exceeded its estimated fair value of $1.3 million as of March 31, 2024. As such, the Company recognized impairment losses of $2.1 million during the three months ended March 31, 2024 and the nine months ended September 30, 2024 on the long-lived asset group associated with the New York Sublease. The impairment losses were allocated to the various assets within the long-lived asset group based on their relative carrying values and consisted of $1.4 million recorded to the right-of-use assets and $0.7 million recorded to property and equipment. No material impairment losses on long-lived assets were recorded during the three months ended September 30, 2024 and the three and nine months ended September 30, 2023.

Leases

9 Months Ended

Sep. 30, 2024

6. Leases

New York Sublease

In May 2016, the Company entered into an operating lease for office space in New York, New York (the New York Lease), which has since been amended to include additional office space and extend the term of the lease. The lease term commenced in July 2016 and expires in April 2027.

In March 2024, the Company entered into an agreement to sublease its office space under the New York Lease (the New York Sublease) to a third-party subtenant. The sublease term commenced in April 2024 and will expire in April 2027 concurrent with the expiration of the New York Lease. Monthly payments under the New York Sublease commenced in July 2024 and escalate annually in accordance with the sublease agreement. As of September 30, 2024, total undiscounted future minimum lease payments to be received by the Company over the term of the New York Sublease were $1.3 million. The Company recognized sublease income of $0.1 million and $0.2 million under the New York Sublease during the three and nine months ended September 30, 2024, respectively.

The New York Sublease is classified as an operating lease and the Company was not relieved of its primary obligation under the New York Lease. The Company continues to account for the New York Lease as it did prior to the commencement of the sublease.

As a result of the New York Sublease, the Company determined an impairment indicator was present as of March 31, 2024 related to the long-lived asset group subject to the sublease, which included the right-of-use asset under the New York Lease, leasehold improvements and other property and equipment allocable to the New York Sublease. The Company concluded the carrying value of the asset group as of March 31, 2024 was not recoverable, as it exceeded the sum of the estimated undiscounted cash flows to be generated by the assets over their remaining lives. The Company estimated the fair value of the asset group as of March 31, 2024 using a discounted cash flow method, which incorporated unobservable inputs including the net identifiable cash flows over the term of the New York Sublease and an estimated borrowing rate of a market participant subtenant. The estimated fair value of the asset group as of March 31, 2024 represents a Level 3 nonrecurring fair value measurement. The Company concluded the carrying value of the asset group of $3.4 million exceeded its estimated fair value of $1.3 million as of March 31, 2024. As such, the Company recognized impairment losses of $2.1 million during the three months ended March 31, 2024 and the nine months ended September 30, 2024 on the long-lived asset group associated with the New York Sublease. The impairment losses were allocated to the various assets within the long-lived asset group based on their relative carrying values and consisted of $1.4 million recorded to the right-of-use assets and $0.7 million recorded to property and equipment. No material impairment losses on long-lived assets were recorded during the three months ended September 30, 2024 and the three and nine months ended September 30, 2023.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2024

Accounting Policies [Abstract]

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, 2023 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023, which was filed with the SEC on February 27, 2024. 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 a fair statement of the results of operations for the periods presented.

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, 2023, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023.

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 fair value measurements.

Reclassifications

Certain amounts reported in prior periods have been reclassified to conform to current period financial statement presentation. These reclassifications are not material and have no effect on previously reported financial position, results of operations and cash flows.

Restricted Cash

Restricted cash consists of deposits held at financial institutions that are used to collateralize irrevocable letters of credit required under the Company’s lease agreements and certain other agreements with third parties. The following table provides a reconciliation of cash and cash equivalents and restricted cash as reported on the consolidated balance sheets to the total of these amounts as reported at the end of the period in the consolidated statements of cash flows (in thousands):


	As of September 30,
	2024		2023
Cash and cash equivalents	$	56,617	$	53,045
Restricted cash		2,030		2,255
Total cash and cash equivalents and restricted cash	$	58,647	$	55,300

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

Leases

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

The Company identifies leases in its contracts if the contract conveys the right to control the use of identified property, plant or equipment for a period of time in exchange for consideration. The Company does not allocate lease consideration between lease and nonlease components and records a lease liability equal to the present value of the remaining fixed consideration under the lease. The interest rates implicit in the Company’s leases are generally not readily determinable. Accordingly, the Company uses its estimated incremental borrowing rate at the commencement date of the lease to determine the present value discount of the lease liability. The Company estimates its incremental borrowing rate for each lease based on an evaluation of its expected credit rating and the prevailing

market rates for collateralized debt in a similar economic environment with similar payment terms and maturity dates commensurate with the term of the lease. The right-of-use asset for each lease is equal to the lease liability, adjusted for unamortized initial direct costs and lease incentives and prepaid or accrued rent. Initial direct costs of entering into a lease are included in the right-of-use asset and amortized as lease expense over the term of the lease. Lease incentives, such as tenant improvement allowances, are recorded as a reduction of the right-of-use asset and amortized as a reduction of lease expense over the term of the lease. The Company excludes options to extend or terminate leases from the calculation of the lease liability unless it is reasonably certain the option will be exercised.

The Company evaluates its right-of-use assets for impairment in accordance with its policy for long-lived assets. To the extent an impairment of a right-of-use asset is recognized, the remaining carrying value of the asset is subsequently amortized as lease expense on a straight-line basis from the date of impairment to the earlier of the end of the right-of-use asset’s useful life or the end of the lease term.

The Company determines the classification of subleases at the inception of the sublease, as well as whether the Company has been relieved of its primary obligation under the original lease. All of the Company's subleases have been classified as operating leases and, in each case, the Company has not been relieved of its primary obligation under the original lease and continues to account for the original lease as it did prior to the commencement of the sublease. Sublease income is recognized on a straight-line basis over the term of the sublease as a reduction of the related lease expense of the original lease. Initial direct costs of entering into a sublease are deferred and amortized on a straight-line basis over the term of the sublease as a reduction of sublease income.

Impairment of Long-lived Assets

The Company's long-lived assets consist primarily of property and equipment and operating lease right-of-use assets. The Company evaluates its long-lived assets for impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparison of the book values of the assets to estimated future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book value of the assets exceed their fair value, which is measured based on the projected discounted future net cash flows arising from the assets. Please refer to Note 5 and Note 6 for further information on impairment of long-lived assets.

Fair Value Measurements

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

•

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

•

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

•

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

To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for assets and liabilities categorized in Level 3. The level within the fair value hierarchy of an asset or liability measured at fair value 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 financial 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 Company's fair value measurements.

Pre-funded Warrants

Warrants are accounted for based on the specific terms of the warrant agreements. The Company's pre-funded warrants are indexed to the Company's common stock and meet the criteria to be classified as equity. Proceeds from the issuance of pre-funded warrants are recorded within additional paid-in capital and are not subject to remeasurement. Please refer to Note 8 for further information regarding pre-funded warrants issued by the Company.

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. For purposes of computing both basic and diluted net loss per share, pre-funded warrants are considered outstanding shares upon issuance because the shares may be issued for nominal consideration and are exercisable after the original issuance date. 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.

Recent Accounting Pronouncements

Recently Adopted Accounting Pronouncements

The Company did not adopt any new accounting standards during the three and nine months ended September 30, 2024 and 2023 which had a material impact on the consolidated financial statements.

Recent Accounting Pronouncements Not Yet Adopted

In November 2023, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which enhances certain interim and annual disclosure requirements of reportable segment information, including information about significant segment expenses. Additionally, the standard requires entities with a single reportable segment to provide all disclosures required by ASC 280, Segment Reporting. The standard is effective for the Company for annual periods beginning January 1, 2024 and interim periods beginning January 1, 2025, with early adoption permitted. Upon the adoption of this standard, the Company will modify its disclosures for segment reporting, as applicable. The Company does not believe the adoption of this standard will have a material impact on its consolidated financial statements.

In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which enhances the disclosure of an entity's effective tax rate reconciliation and requires the disclosure of income taxes paid to be disaggregated by jurisdiction. The standard is effective for the Company beginning January 1, 2025, with early adoption permitted. Upon the adoption of this standard, the Company will modify its disclosures for income taxes, as applicable. The Company does not believe the adoption of this standard will have a material impact on its consolidated financial statements.

In November 2024, the FASB issued ASU 2024-03, Income Statement – Reporting Comprehensive Income – Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses. The new standard requires disclosures about specific types of expenses included in the expense captions presented on the face of the income statement as well as disclosures about selling expenses. The standard is effective for the Company for annual periods beginning January 1, 2027 and interim periods beginning January 1, 2028, with early adoption permitted. The standard may be applied either prospectively to financial statements issued for reporting periods after the effective date or retrospectively to any or all prior periods presented in the financial statements. The Company is evaluating the impact of this standard on its consolidated financial statements and related disclosures.

Stock-based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	9 Months Ended
	Jan. 31, 2024	Sep. 30, 2024
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense		$ 69.5
Unrecognized stock-based compensation, weighted-average period		2 years 4 months 24 days
Proceeds from stock options exercised including unsettled options		$ 1.5
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock units vested		390,000
Total intrinsic values vested		$ 6.7
2015 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional shares to be issued	1,761,849
Common stock shares authorized for issuance		19,118,989
Shares available for future grants		1,511,556
Weighted-average fair values of options granted		$ 10.06
Exercise of stock options, net of tax, shares		280,753
Total intrinsic value of options exercised		$ 3.0
2015 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares authorized for issuance		1,426,994
Shares available for future grants		912,964
Common stock shares issued to participants		105,400

Restructuring - Summary of Restructuring Liability (Details) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2023	Sep. 30, 2024	Dec. 31, 2023
Restructuring and Related Activities [Abstract]
Beginning Balance		$ 1,806,000
Restructuring charges	$ 3,700,000		$ 3,731,000
Cash payments		(1,370,000)	(1,925,000)
Other adjustments		(436,000)
Ending Balance	$ 1,806,000	$ 0	$ 1,806,000

Consolidated Statements of Stockholders' Equity (Parenthetical) - Common Stock [Member] - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Public Offering [Member]
Issuance of Stock, transaction costs		$ 534
Private Placement [Member]
Issuance of Stock, transaction costs	$ 126		$ 126

Restructuring

9 Months Ended

Sep. 30, 2024

Restructuring and Related Activities [Abstract]

Restructuring

12. Restructuring

In November 2023, the Company implemented a strategic pipeline prioritization and corporate restructuring designed to reduce operating expenses and prioritize the development of ABBV-RGX-314, RGX-202 for the treatment of Duchenne muscular dystrophy, and RGX-121 for the treatment of Mucopolysaccharidosis Type II (MPS II), while pursuing strategic alternatives for the Company's other clinical stage programs. The restructuring included a reduction in workforce and other planned operating expenses, primarily in rare neurodegenerative disease development, early research and other general and administrative areas.

In connection with the restructuring, the Company implemented a reduction in workforce of approximately 15%, which was substantially completed in the fourth quarter of 2023. The Company recorded restructuring costs of $3.7 million in the fourth quarter of 2023, which primarily consisted of employee severance, continuing healthcare benefits and other employee-related costs. During the nine months ended September 30, 2024, the Company recorded reductions in the restructuring liability of $0.4 million associated with changes in total estimated restructuring costs. As of September 30, 2024, all of the restructuring costs had been paid by the Company and no restructuring liability was recorded. The following table presents the details of the Company's restructuring liability as of September 30, 2024 (in thousands):


	Restructuring Liability
Balance at December 31, 2022	$	—
Restructuring charges		3,731
Cash payments		(1,925	)
Balance at December 31, 2023		1,806
Cash payments		(1,370	)
Other adjustments		(436	)
Balance at September 30, 2024	$	—

Stock-based Compensation - Stock-Based Compensation Expense by Award Type (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 9,884	$ 10,219	$ 28,921	$ 31,929
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	6,051	7,275	17,969	22,868
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	3,755	2,843	10,536	8,475
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 78	$ 101	$ 416	$ 586

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(v)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

Supplemental Disclosures (Tables)

9 Months Ended

Sep. 30, 2024

Payables and Accruals [Abstract]

Schedule of Other Current Assets

Other current assets consisted of the following (in thousands):


	September 30, 2024		December 31, 2023
Net cost reimbursement due from collaborators	$	20,302	$	17,745
Accrued interest on investments		1,578		1,551
Other		1,450		1,107
	$	23,330	$	20,403

Schedules of Accrued Expenses and Other Current Liabilities

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


	September 30, 2024		December 31, 2023
Accrued external research and development expenses	$	16,715	$	13,762
Accrued sublicense fees and royalties		14,628		14,234
Accrued personnel costs		14,335		18,146
Accrued external general and administrative expenses		1,843		2,717
Accrued purchases of property and equipment		334		386
Other accrued expenses and current liabilities		787		458
	$	48,642	$	49,703

Supplemental Disclosures - Additional Information (Detail) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Supplemental Disclosures of Non-cash Investing and Financing Activities [Line Items]
Purchases of property and equipment included in accounts payable and accrued expenses and other current liabilities	$ 400,000	$ 500,000
Increase (decrease) in purchases of property and equipment included in accounts payable and accrued expenses and other current liabilities				$ (2,000,000)
Offering expenses for ATM Program	$ 0	$ 400,000
Maximum [Member]
Supplemental Disclosures of Non-cash Investing and Financing Activities [Line Items]
Increase (decrease) in purchases of property and equipment included in accounts payable and accrued expenses and other current liabilities			$ 100,000

License and Collaboration Agreements

9 Months Ended

Sep. 30, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

License and Collaboration Agreements

9. License and Collaboration Agreements

License and Royalty Revenue

As of September 30, 2024, the Company’s NAV Technology Platform was being applied by NAV Technology Licensees in one commercial product, Zolgensma, and in the development of a number of other 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, (v) fees for services related to the development of licensed products and (vi) 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 September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Zolgensma royalties	$	23,872	$	28,364	$	60,849	$	63,454
Other license and royalty revenue		325		550		1,265		4,575
Total license and royalty revenue	$	24,197	$	28,914	$	62,114	$	68,029

Outstanding 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 September 30, 2024, 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 $1.51 billion, including (i) $524.9 million upon the commencement of various stages of clinical trials, (ii) $113.8 million upon the submission of regulatory approval filings or upon regulatory approval of licensed products and (iii) $870.0 million upon the achievement of specified sales targets for licensed products, including milestones payable upon the first commercial sale of licensed products. To the extent the milestone payments are realized by the Company, the Company may 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 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				Nine Months Ended
	September 30,				September 30,
	2024		2023		2024		2023
Accounts receivable, net, current and non-current:
Beginning of period	$	23,273	$	22,523	$	25,491	$	29,586
End of period	$	24,008	$	29,121	$	24,008	$	29,121

Contract assets:
Beginning of period	$	194	$	2,000	$	—	$	—
End of period	$	259	$	2,000	$	259	$	2,000

Deferred revenue:
Beginning of period	$	21	$	448	$	148	$	1,829
End of period	$	144	$	442	$	144	$	442

Revenue recognized during the period from:
Amounts included in deferred revenue at beginning of period	$	21	$	28	$	148	$	1,409
Performance obligations satisfied in previous periods	$	23,875	$	28,365	$	60,912	$	65,405

As of September 30, 2024, the Company had recorded deferred revenue of $0.1 million which represents consideration received or unconditionally due from licensees for performance obligations that have not yet been satisfied by the Company. Unsatisfied performance obligations as of September 30, 2024 consisted of research and development services to be performed by the Company related to licensed products, which will be satisfied as the services are performed. As of September 30, 2024, the aggregate transaction price of the Company’s license agreements allocated to performance obligations not yet satisfied, or partially satisfied, was $1.5 million, which is expected to be satisfied over a period of approximately two to three years.

Revenue recognized from performance obligations satisfied in previous periods, as presented in the table above, 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, resulting in a cumulative catch-up adjustment to revenue. Revenue recognized during the nine months ended September 30, 2023 included $2.0 million in cumulative catch-up adjustments for changes in the probability of achievement of development milestones. There were no cumulative catch-up adjustments to revenue for changes in the probability of achievement of development milestones during the three and nine months ended September 30, 2024 or during the three months ended September 30, 2023.

Accounts Receivable, Contract Assets and the Allowance for Credit Losses

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


	September 30, 2024			December 31, 2023
Current accounts receivable:
Billed to customers	$	105		$	265
Unbilled Zolgensma royalties		23,138			24,128
Due from Abeona, net of present value discount		4,942			4,587
Other unbilled		361			397
Allowance for credit losses		(4,942	)		(4,587	)
Current accounts receivable, net		23,604			24,790
Non-current accounts receivable:
Other unbilled		404			701
Non-current accounts receivable, net		404			701
Total accounts receivable, net	$	24,008		$	25,491

The following table presents the changes in the allowance for credit losses related to accounts receivable and contract assets for the nine months ended September 30, 2024 (in thousands):


	Allowance for Credit Losses
	Accounts Receivable		Contract Assets
Balance at December 31, 2023	$	4,587	$	—
Changes in present value discount of receivables		355		—
Balance at September 30, 2024	$	4,942	$	—

The Company’s allowance for credit losses as of September 30, 2024 and December 31, 2023 was related solely to accounts receivable from Abeona Therapeutics Inc. (Abeona). Please refer to the section below, "Settlement Agreement with Abeona Therapeutics", for further information regarding amounts due from Abeona and the associated allowance for credit losses. The Company did not record a provision for credit losses for the three and nine months ended September 30, 2024 and 2023.

Zolgensma License with Novartis Gene Therapies

In March 2014, the Company entered into an exclusive license agreement (as amended, the Novartis License) with Novartis Gene Therapies. Under the Novartis 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. In 2019, Novartis Gene Therapies launched commercial sales of Zolgensma, a licensed product under the Novartis License. In accordance with the Novartis License, the Company receives royalties on net sales of Zolgensma.

The Company recognized the following amounts under the Novartis License (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Zolgensma royalties	$	23,872	$	28,364	$	60,849	$	63,454
Total license and royalty revenue	$	23,872	$	28,364	$	60,849	$	63,454

Interest income from licensing	$	6	$	7	$	20	$	22

As of September 30, 2024 and December 31, 2023, the Company had recorded total accounts receivable of $23.3 million and $24.3 million, respectively, from Novartis Gene Therapies under the Novartis License, which consisted primarily of Zolgensma royalties receivable. The Zolgensma royalties receivable recorded as of September 30, 2024 included $11.1 million expected to be paid to HCR in accordance with the Royalty Purchase Agreement discussed in Note 7. The Company recognizes royalty revenue from net sales of Zolgensma in the period in which the underlying products are sold by Novartis Gene Therapies, which in certain cases may require the Company to estimate royalty revenue for periods of net sales which have not yet been reported to the Company. Estimated royalties are reconciled to actual amounts reported in subsequent periods, and any differences are recognized as an adjustment to royalty revenue in the period the royalties are reported.

Settlement Agreement with Abeona Therapeutics

In November 2021, the Company entered into a settlement agreement and mutual release with Abeona (the Settlement Agreement) related to claims associated with a license agreement between the parties which was terminated in May 2020. The Settlement Agreement resolved all arbitration and legal proceedings and mutually released each party from any and all claims under the terminated license agreement. 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 which was paid in November 2022, 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 September 30, 2024 and December 31, 2023, the Company had recorded accounts receivable of $4.9 million and $4.6 million, respectively, associated with the remaining amounts due from Abeona under the Settlement Agreement. The receivable of $4.9 million as of September 30, 2024 consisted of the $5.0 million payment due by November 2024, net of discount to present value. 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 $4.9 million and $4.6 million as of September 30, 2024 and December 31, 2023, respectively, related to the accounts receivable due from Abeona. No credit losses or recoveries were recorded on the Abeona receivable during the three and nine months ended September 30, 2024 and 2023. The present value discount of the Abeona receivable 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 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 Abeona receivable.

Collaboration Agreements

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 ABBV-RGX-314, the Company’s product candidate for the treatment of wet age-related macular degeneration (wet AMD), diabetic retinopathy (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 ABBV-RGX-314 in the United States and an exclusive license to develop and commercialize ABBV-RGX-314 outside the United States. The Company and AbbVie will collaborate to develop ABBV-RGX-314 in the United States, and AbbVie will be responsible for the development of ABBV-RGX-314 in specified markets outside the United States. Through December 31, 2022, the Company was responsible for the development expenses related to certain ongoing clinical trials of ABBV-RGX-314 and the parties shared the additional development expenses related to ABBV-RGX-314. Beginning on January 1, 2023, AbbVie became responsible for the majority of all ABBV-RGX-314 development expenses.

The Company will lead the manufacturing of ABBV-RGX-314 for clinical development and U.S. commercial supply, and AbbVie will lead the manufacturing of ABBV-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 ABBV-RGX-314 for commercial supply outside the United States at a price specified in the agreement. AbbVie will lead the commercialization of ABBV-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 ABBV-RGX-314 in the United States. Outside the United States, AbbVie will be responsible, at its sole cost, for the commercialization of ABBV-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 ABBV-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 ASC 606, Revenue from Contracts with Customers (ASC 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 ABBV-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 September 30, 2024 and December 31, 2023, the transaction price of the AbbVie Collaboration Agreement was $370.0 million, which consisted solely of the up-front payment received from AbbVie 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 ABBV-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 ASC 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 and nine months ended September 30, 2024 and 2023.

The Company applied the requirements of ASC 808, Collaborative Arrangements (ASC 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 ABBV-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 ABBV-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 September 30, 2024 and December 31, 2023, the Company had recorded $20.3 million and $17.7 million, respectively, due from AbbVie for net reimbursement of costs incurred for activities performed under AbbVie Collaboration Agreement, which was 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 September 30,						Nine Months Ended September 30,
	2024			2023			2024			2023
Net cost reimbursement to (from) AbbVie included in:
Research and development expense	$	(20,082	)	$	(19,608	)	$	(66,330	)	$	(56,300	)
General and administrative expense		341			615			1,168			1,007
Total net cost reimbursement to (from) AbbVie	$	(19,741	)	$	(18,993	)	$	(65,162	)	$	(55,293	)

Property and Equipment Net - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Property Plant And Equipment [Line Items]
Total property and equipment	$ 189,900	$ 189,311
Accumulated depreciation and amortization	(69,349)	(57,208)
Property and equipment, net	120,551	132,103
Laboratory and Manufacturing Equipment [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	76,788	75,632
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	4,748	4,700
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	7,024	7,052
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	$ 101,340	$ 101,927

Property and Equipment, Net

9 Months Ended

Sep. 30, 2024

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

5. Property and Equipment, Net

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


	September 30, 2024			December 31, 2023
Laboratory and manufacturing equipment	$	76,788		$	75,632
Computer equipment and software		4,748			4,700
Furniture and fixtures		7,024			7,052
Leasehold improvements		101,340			101,927
Total property and equipment		189,900			189,311
Accumulated depreciation and amortization		(69,349	)		(57,208	)
Property and equipment, net	$	120,551		$	132,103

In March 2024, the Company entered into an agreement to sublease its office facilities in New York, New York. In connection with the sublease, the Company recorded impairment of property and equipment of $0.7 million in the first quarter of 2024 related to furniture and fixtures and leasehold improvements located at the subleased facility. Please refer to Note 6 for further information regarding the sublease agreement and associated impairment of long-lived assets.

License and Collaboration Agreements -Schedule of AbbVie Collaboration Agreement (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Net cost reimbursement to (from) AbbVie included in:
Total net cost reimbursement to (from) AbbVie	$ (19,741)	$ (18,993)	$ (65,162)	$ (55,293)
Abb Vie Collaboration And License Agreement \| Research and Development Expense [Member]
Net cost reimbursement to (from) AbbVie included in:
Total net cost reimbursement to (from) AbbVie	(20,082)	(19,608)	(66,330)	(56,300)
Abb Vie Collaboration And License Agreement \| General and Administrative Expense [Member]
Net cost reimbursement to (from) AbbVie included in:
Total net cost reimbursement to (from) AbbVie	$ 341	$ 615	$ 1,168	$ 1,007

License and Collaboration Agreements (Tables)

9 Months Ended

Sep. 30, 2024

Schedule Of License and Royalty Revenue

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


	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Zolgensma royalties	$	23,872	$	28,364	$	60,849	$	63,454
Other license and royalty revenue		325		550		1,265		4,575
Total license and royalty revenue	$	24,197	$	28,914	$	62,114	$	68,029

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


	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2024		2023		2024		2023
Accounts receivable, net, current and non-current:
Beginning of period	$	23,273	$	22,523	$	25,491	$	29,586
End of period	$	24,008	$	29,121	$	24,008	$	29,121

Contract assets:
Beginning of period	$	194	$	2,000	$	—	$	—
End of period	$	259	$	2,000	$	259	$	2,000

Deferred revenue:
Beginning of period	$	21	$	448	$	148	$	1,829
End of period	$	144	$	442	$	144	$	442

Revenue recognized during the period from:
Amounts included in deferred revenue at beginning of period	$	21	$	28	$	148	$	1,409
Performance obligations satisfied in previous periods	$	23,875	$	28,365	$	60,912	$	65,405

Summary of Accounts Receivables, net

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


	September 30, 2024			December 31, 2023
Current accounts receivable:
Billed to customers	$	105		$	265
Unbilled Zolgensma royalties		23,138			24,128
Due from Abeona, net of present value discount		4,942			4,587
Other unbilled		361			397
Allowance for credit losses		(4,942	)		(4,587	)
Current accounts receivable, net		23,604			24,790
Non-current accounts receivable:
Other unbilled		404			701
Non-current accounts receivable, net		404			701
Total accounts receivable, net	$	24,008		$	25,491

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 nine months ended September 30, 2024 (in thousands):


	Allowance for Credit Losses
	Accounts Receivable		Contract Assets
Balance at December 31, 2023	$	4,587	$	—
Changes in present value discount of receivables		355		—
Balance at September 30, 2024	$	4,942	$	—

Schedule of AbbVie Collaboration Agreement

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


	Three Months Ended September 30,						Nine Months Ended September 30,
	2024			2023			2024			2023
Net cost reimbursement to (from) AbbVie included in:
Research and development expense	$	(20,082	)	$	(19,608	)	$	(66,330	)	$	(56,300	)
General and administrative expense		341			615			1,168			1,007
Total net cost reimbursement to (from) AbbVie	$	(19,741	)	$	(18,993	)	$	(65,162	)	$	(55,293	)

Novartis Gene Therapies [Member]

Schedule Of License and Royalty Revenue

The Company recognized the following amounts under the Novartis License (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Zolgensma royalties	$	23,872	$	28,364	$	60,849	$	63,454
Total license and royalty revenue	$	23,872	$	28,364	$	60,849	$	63,454

Interest income from licensing	$	6	$	7	$	20	$	22

Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2024

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 fair value hierarchy discussed in Note 2 (in thousands):


	Level 1		Level 2		Level 3		Total
September 30, 2024
Cash equivalents:
Money market mutual funds	$	—	$	43,771	$	—	$	43,771
Total cash equivalents		—		43,771		—		43,771
Marketable securities:
U.S. government and agency securities		—		50,133		—		50,133
Certificates of deposit		—		4,389		—		4,389
Corporate bonds		—		167,429		—		167,429
Total marketable securities		—		221,951		—		221,951
Total cash equivalents and marketable securities	$	—	$	265,722	$	—	$	265,722


	Level 1		Level 2		Level 3		Total
December 31, 2023
Cash equivalents:
Money market mutual funds	$	—	$	13,024	$	—	$	13,024
Total cash equivalents		—		13,024		—		13,024
Marketable securities:
U.S. government and agency securities		—		70,569		—		70,569
Certificates of deposit		—		6,466		—		6,466
Corporate bonds		—		202,572		—		202,572
Total marketable securities		—		279,607		—		279,607
Total cash equivalents and marketable securities	$	—	$	292,631	$	—	$	292,631

Insider Trading Arrangements - Directors or Section 16 Reporting Officers [Member]	3 Months Ended
	Sep. 30, 2024
Trading Arrangements, by Individual
Title	directors or Section 16 reporting officers
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Liability Related to Sale of Future Royalties - Additional Information (Details) $ in Millions	9 Months Ended
	Sep. 30, 2024 USD ($)
Liability Related To Sale Of Future Royalties [Line Items]
Repurchase of call option amount	$ 300.0
November 7, 2024
Liability Related To Sale Of Future Royalties [Line Items]
Repurchase of call option amount, before exercised	1.0
HCR [Member]
Liability Related To Sale Of Future Royalties [Line Items]
Proceeds from Royalties Received	4.0
Proceeds from sale of future royalties	196.0
Deferred Transaction Cost	3.5
Interest expense	$ 192.5
Interest Rate, Effective Percentage	4.20%
HCR [Member] \| November 7, 2024
Liability Related To Sale Of Future Royalties [Line Items]
Royalty Payment Cap Amount	$ 260.0
HCR [Member] \| November 8, 2024
Liability Related To Sale Of Future Royalties [Line Items]
Royalty Payment Cap Amount	300.0
HCR [Member] \| Royalty Agreements
Liability Related To Sale Of Future Royalties [Line Items]
Purchase Agreement	$ 200.0

Net Loss Per Share - Schedules for Computation of Diluted Weighted-Average Shares Outstanding (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted weighted average shares outstanding	12,099	10,286	12,099	10,286
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	10,017	8,856	10,017	8,856
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	2,035	1,394	2,035	1,394
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	47	36	47	36

Nature of Business - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ (880,963)	$ (705,047)
Cash, cash equivalents and marketable securities	$ 278,600

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Mar. 31, 2024	Sep. 30, 2024
Property, Plant and Equipment [Line Items]
Impairment of property and equipment		$ 2,101
Furniture Fixtures and Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Impairment of property and equipment	$ 700

Property and Equipment, Net (Tables)

9 Months Ended

Sep. 30, 2024

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment

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


	September 30, 2024			December 31, 2023
Laboratory and manufacturing equipment	$	76,788		$	75,632
Computer equipment and software		4,748			4,700
Furniture and fixtures		7,024			7,052
Leasehold improvements		101,340			101,927
Total property and equipment		189,900			189,311
Accumulated depreciation and amortization		(69,349	)		(57,208	)
Property and equipment, net	$	120,551		$	132,103

Marketable Securities

9 Months Ended

Sep. 30, 2024

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
September 30, 2024
U.S. government and agency securities	$	50,350	$	16	$	(233	)	$	50,133
Certificates of deposit		4,404		—		(15	)		4,389
Corporate bonds		166,919		583		(73	)		167,429
	$	221,673	$	599	$	(321	)	$	221,951


	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2023
U.S. government and agency securities	$	71,811	$	6	$	(1,248	)	$	70,569
Certificates of deposit		6,572		—		(106	)		6,466
Corporate bonds		204,793		143		(2,364	)		202,572
	$	283,176	$	149	$	(3,718	)	$	279,607

As of September 30, 2024 and December 31, 2023, 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 September 30, 2024 and December 31, 2023, 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. The Company did not recognize any realized gains or losses on available-for-sales securities during the three and nine months ended September 30, 2024 and 2023, and no income tax effects or reclassification adjustments were recorded in accumulated other comprehensive loss during the periods.

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
September 30, 2024
U.S. government and agency securities	$	—	$	—		$	30,252	$	(233	)	$	30,252	$	(233	)
Certificates of deposit		484		(1	)		3,170		(14	)		3,654		(15	)
Corporate bonds		4,995		(1	)		21,290		(72	)		26,285		(73	)
	$	5,479	$	(2	)	$	54,712	$	(319	)	$	60,191	$	(321	)


	Less than 12 Months					12 Months or Greater					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
December 31, 2023
U.S. government and agency securities	$	12,877	$	(16	)	$	52,686	$	(1,232	)	$	65,563	$	(1,248	)
Certificates of deposit		965		(2	)		5,257		(104	)		6,222		(106	)
Corporate bonds		25,051		(48	)		144,642		(2,316	)		169,693		(2,364	)
	$	38,893	$	(66	)	$	202,585	$	(3,652	)	$	241,478	$	(3,718	)

As of September 30, 2024, available-for-sale debt securities held by the Company in an unrealized loss position consisted of 36 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 September 30, 2024 or December 31, 2023, and no impairment or credit losses on available-for-sale debt securities were recorded during the three and nine months ended September 30, 2024 and 2023.

Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2024

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 September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Stock options	$	6,051	$	7,275	$	17,969	$	22,868
Restricted stock units		3,755		2,843		10,536		8,475
Employee stock purchase plan		78		101		416		586
	$	9,884	$	10,219	$	28,921	$	31,929

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 September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Research and development	$	4,301	$	5,131	$	13,893	$	16,670
General and administrative		5,583		5,088		15,028		15,259
	$	9,884	$	10,219	$	28,921	$	31,929

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, 2023		1,309		$	25.89
Granted		1,188		$	16.22
Vested		(390	)	$	27.20
Forfeited		(72	)	$	22.45
Unvested balance at September 30, 2024		2,035		$	20.11

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, 2023		8,581		$	32.62		6.2	$	7,011
Granted		2,263		$	16.24
Exercised		(281	)	$	5.25
Cancelled or forfeited		(546	)	$	35.56
Outstanding at September 30, 2024		10,017		$	29.53		6.4	$	529
Exercisable at September 30, 2024		6,609		$	34.38		5.1	$	529
Vested and expected to vest at September 30, 2024		10,017		$	29.53		6.4	$	529

(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.

License and Collaboration Agreements - Schedule Of License and Royalty Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Other license and royalty revenue	$ 325	$ 550	$ 1,265	$ 4,575
Total license and royalty revenue	24,197	28,914	62,114	68,029
Zolgensma Royalties [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Zolgensma royalties	$ 23,872	$ 28,364	$ 60,849	$ 63,454

- 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
-Topic 280
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-Name Accounting Standards Codification
-Section 50
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
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-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Section 50
-Paragraph 32
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-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 4: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
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-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (b)
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-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 5: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
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-Name Accounting Standards Codification
-Section 50
-Paragraph 32
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 924
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-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
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-URI https://asc.fasb.org/1943274/2147479941/924-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
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-URI https://asc.fasb.org/1943274/2147479806/606-10-50-5

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-42

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Name Accounting Standards Codification
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-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-40

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-4

+ Details

Restructuring - Additional Information (Details) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2023	Sep. 30, 2024	Dec. 31, 2023
Restructuring Cost and Reserve [Line Items]
Percentage of reduction in workforce	15.00%
Restructuring costs	$ 3,700,000		$ 3,731,000
Reductions in restructuring liability		$ (400,000)
Restructuring liability	$ 1,806,000	$ 0	$ 1,806,000

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Net Loss Per Share

9 Months Ended

Sep. 30, 2024

Earnings Per Share [Abstract]

Net Loss Per Share

13. Net Loss Per Share

Since the Company incurred net losses for the three and nine months ended September 30, 2024 and 2023, common stock equivalents were excluded from the calculation of diluted net loss per share for such periods as their effect would be anti-dilutive. Accordingly, basic and diluted net loss per share were the same for such periods. The weighted-average number of common shares outstanding used in the basic and diluted net loss per share calculations includes the weighted-average effect of pre-funded warrants to purchase shares of the Company's common stock, as the pre-funded warrants are exercisable at any time for nominal cash consideration. 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 and Nine Months Ended September 30,
	2024		2023
Stock options issued and outstanding		10,017		8,856
Unvested restricted stock units outstanding		2,035		1,394
Employee stock purchase plan		47		36
		12,099		10,286

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	49,534,000	44,046,000
Common stock, shares outstanding	49,534,000	44,046,000

License and Collaboration Agreements - Summary of Changes in Allowance For Credit Losses (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2024 USD ($)
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	$ 4,587
Changes in present value discount of receivables	355
Ending Balance	$ 4,942

- 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 Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenues
Revenues	$ 24,197	$ 28,914	$ 62,114	$ 68,029
Operating Expenses
Cost of revenues	12,387	12,388	27,249	25,975
Research and development	54,429	58,183	158,142	176,585
General and administrative	19,422	23,083	56,568	69,415
Impairment of long-lived assets			2,101
Other operating expenses	37	220	32	279
Total operating expenses	86,275	93,874	244,092	272,254
Loss from operations	(62,078)	(64,960)	(181,978)	(204,225)
Other Income (Expense)
Interest income from licensing	25	56	91	166
Investment income	3,276	4,660	9,213	8,953
Interest expense	(820)	(1,624)	(3,242)	(5,499)
Total other income	2,481	3,092	6,062	3,620
Net loss	(59,597)	(61,868)	(175,916)	(200,605)
Other Comprehensive Income
Unrealized gain on available-for-sale securities, net	1,684	2,685	3,847	7,988
Total other comprehensive income	1,684	2,685	3,847	7,988
Comprehensive loss	$ (57,913)	$ (59,183)	$ (172,069)	$ (192,617)
Net loss per share, basic	$ (1.17)	$ (1.41)	$ (3.59)	$ (4.6)
Net loss per share, diluted	$ (1.17)	$ (1.41)	$ (3.59)	$ (4.6)
Weighted-average common shares outstanding, basic	50,800	43,945	49,051	43,644
Weighted-average common shares outstanding, diluted	50,800	43,945	49,051	43,644
License and royalty [Member]
Revenues
Revenues	$ 24,197	$ 28,914	$ 62,114	$ 68,029

License and Collaboration Agreements - Additional Information (Detail)	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2024 USD ($) ProductCandidate	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) ProductCandidate	Sep. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment upon commencement of clinical trials in humans				$ 524,900,000
Milestone payment upon submission of regulatory approval filings				113,800,000
Milestone payment upon achievement of specified sales targets for licensed products				870,000,000
Deferred revenue, current and non-current		$ 144,000	$ 442,000	144,000	$ 442,000	$ 21,000	$ 148,000	$ 448,000	$ 1,829,000
Contract assets		259,000	2,000,000	259,000	2,000,000	194,000		2,000,000
Aggregate transaction price of license agreements				1,500,000
Revenue recognized upon achievement of development milestones		0	0	0	2,000,000
Provision for credit losses		0	0	0	0
Accounts receivable		24,008,000	29,121,000	24,008,000	29,121,000	$ 23,273,000	25,491,000	$ 22,523,000	$ 29,586,000
Due from related parties, current		4,942,000		4,942,000			4,587,000
Abb Vie Collaboration And License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [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			370,000,000.0
Change in transaction price		0	0	0	0
Abb Vie Collaboration And License Agreement \| Other Current Assets [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Due from related parties, current		20,300,000		20,300,000			17,700,000
Novartis License Agreement [Member] \| Novartis Gene Therapies [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable		23,300,000		23,300,000			24,300,000
November Two Thousand Eighteen License Agreement \| Abeona Therapeutics Incorporation \| Contract Termination
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Settlement agreement payable				30,000,000
November Two Thousand Twenty One License Agreement \| Abeona Therapeutics Incorporation \| Contract Termination
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Settlement agreement payable				20,000,000
November Two Thousand Twenty Two License Agreement \| Abeona Therapeutics Incorporation \| Contract Termination
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Settlement agreement payable				5,000,000
November Two Thousand Twenty Four License Agreement \| Abeona Therapeutics Incorporation \| Contract Termination
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Settlement agreement payable				5,000,000
Settlement Agreement \| Abeona Therapeutics Incorporation
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable		4,900,000		4,900,000			4,600,000
Due from related parties		5,000,000.0		5,000,000.0
Allowance for credit losses		4,900,000		4,900,000			4,600,000
Provision for credit losses		0	$ 0	0	$ 0
Sales Based Milestones \| Abb Vie Collaboration And License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [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			820,000,000.0
Development Milestone \| Abb Vie Collaboration And License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [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			$ 562,500,000
Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate milestone payment for all the targets				1,510,000,000
Deferred revenue, current and non-current		$ 100,000		$ 100,000
Aggregate transaction price of license agreements, expected satisfaction period				3 years
Minimum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate transaction price of license agreements, expected satisfaction period				2 years
N A V Technology Platform [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of commercial product candidates \| ProductCandidate		1		1
HCR [Member] \| Novartis License Agreement [Member] \| Novartis Gene Therapies [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable, current		$ 11,100,000		$ 11,100,000

Restructuring (Tables)

9 Months Ended

Sep. 30, 2024

Restructuring and Related Activities [Abstract]

Summary of Restructuring Liability

The following table presents the details of the Company's restructuring liability as of September 30, 2024 (in thousands):


	Restructuring Liability
Balance at December 31, 2022	$	—
Restructuring charges		3,731
Cash payments		(1,925	)
Balance at December 31, 2023		1,806
Cash payments		(1,370	)
Other adjustments		(436	)
Balance at September 30, 2024	$	—

Supplemental Disclosures - Schedules of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued external research and development expenses	$ 16,715	$ 13,762
Accrued sublicense fees and royalties	14,628	14,234
Accrued personnel costs	14,335	18,146
Accrued external general and administrative expenses	1,843	2,717
Accrued purchases of property and equipment	334	386
Other accrued expenses and current liabilities	787	458
Accrued expenses and other current liabilities	$ 48,642	$ 49,703

Marketable Securities - Summary of Company Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	$ 221,673	$ 283,176
Unrealized Gains	599	149
Unrealized Losses	(321)	(3,718)
Fair Value	221,951	279,607
U.S. Government and Agency Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	50,350	71,811
Unrealized Gains	16	6
Unrealized Losses	(233)	(1,248)
Fair Value	50,133	70,569
Certificates of Deposit [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	4,404	6,572
Unrealized Losses	(15)	(106)
Fair Value	4,389	6,466
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost / Cost	166,919	204,793
Unrealized Gains	583	143
Unrealized Losses	(73)	(2,364)
Fair Value	$ 167,429	$ 202,572

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

License and Collaboration Agreements - Summary of Accounts Recerivable, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current accounts receivable:
Billed to customers	$ 105	$ 265
Unbilled Zolgensma royalties	23,138	24,128
Due from Abeona, net of present value discount	$ 4,942	$ 4,587
Other Receivable, after Allowance for Credit Loss, Current, Related Party [Extensible Enumeration]	Related Party [Member]	Related Party [Member]
Other unbilled	$ 361	$ 397
Allowance for credit losses	(4,942)	(4,587)
Current accounts receivable, net	23,604	24,790
Non-current accounts receivable:
Other unbilled	404	701
Non-current accounts receivable, net	404	701
Total accounts receivable, net	$ 24,008	$ 25,491

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2024	Oct. 31, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Trading Symbol	RGNX
Entity Registrant Name	REGENXBIO Inc.
Entity Central Index Key	0001590877
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-37553
Entity Tax Identification Number	47-1851754
Entity Address, Address Line One	9804 Medical Center Drive
Entity Address, City or Town	Rockville
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	20850
City Area Code	240
Local Phone Number	552-8181
Entity Common Stock, Shares Outstanding		49,545,071
Document Transition Report	false
Document Quarterly Report	true
Entity Interactive Data Current	Yes
Security Exchange Name	NASDAQ
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Entity Incorporation, State or Country Code	DE

Income Taxes

9 Months Ended

Sep. 30, 2024

Income Tax Disclosure [Abstract]

Income Taxes

11. Income Taxes

The Company evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets as of September 30, 2024 and December 31, 2023. 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 September 30, 2024 and December 31, 2023.

- Definition

The entire disclosure for income tax.

+ References

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+ Details

Liability Related to Sale of Future Royalties

9 Months Ended

Sep. 30, 2024

7. 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 Royalty Purchase Agreement, HCR purchased the Company’s rights to a capped amount of Zolgensma royalty payments under the Company’s license agreement (the Novartis License) 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 Royalty Purchase Agreement, Zolgensma royalty payments, up to a specified threshold, shall 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 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 Royalty Purchase 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 Novartis License. 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 Novartis License.

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 Royalty Purchase 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 Novartis License, 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 September 30, 2024, the estimated effective interest rate under the Royalty Purchase Agreement was 4.2%. 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, 2023	$	94,052
Zolgensma royalties paid to HCR		(35,072	)
Interest expense recognized		2,769
Balance at September 30, 2024		61,749
Current portion of liability related to sale of future royalties		(26,697	)
Liability related to sale of future royalties, non-current	$	35,052

Supplemental Disclosures

9 Months Ended

Sep. 30, 2024

Payables and Accruals [Abstract]

Supplemental Disclosures

14. Supplemental Disclosures

Other Current Assets

Other current assets consisted of the following (in thousands):


	September 30, 2024		December 31, 2023
Net cost reimbursement due from collaborators	$	20,302	$	17,745
Accrued interest on investments		1,578		1,551
Other		1,450		1,107
	$	23,330	$	20,403

Accrued Expenses and Other Current Liabilities

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


	September 30, 2024		December 31, 2023
Accrued external research and development expenses	$	16,715	$	13,762
Accrued sublicense fees and royalties		14,628		14,234
Accrued personnel costs		14,335		18,146
Accrued external general and administrative expenses		1,843		2,717
Accrued purchases of property and equipment		334		386
Other accrued expenses and current liabilities		787		458
	$	48,642	$	49,703

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 $0.4 million as of September 30, 2024, a net decrease of less than $0.1 million from December 31, 2023, and $0.5 million as of September 30, 2023, a net decrease of $2.0 million from December 31, 2022.

Offering expenses for the ATM Program included in accounts payable and accrued expenses and other liabilities were $0.4 million as of September 30, 2023. No such amounts were recorded as of September 30, 2024.

Stock-based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 9,884	$ 10,219	$ 28,921	$ 31,929
Research and Development Expense [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	4,301	5,131	13,893	16,670
General and Administrative Expense [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 5,583	$ 5,088	$ 15,028	$ 15,259

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities
Net loss	$ (175,916)	$ (200,605)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation expense	28,921	31,929
Depreciation and amortization	12,192	12,985
Net amortization of premiums (accretion of discounts) on marketable debt securities	(3,027)	929
Net realized gain on investments		(2,205)
Impairment of long-lived assets	2,101
Non-cash interest expense	412	(569)
Other non-cash adjustments	(60)	(1)
Changes in operating assets and liabilities
Accounts receivable	1,574	566
Prepaid expenses	3,518	1,339
Other current assets	(2,804)	(13,573)
Operating lease right-of-use assets	4,586	4,245
Other assets	475	1,728
Accounts payable	(3,330)	(4,011)
Accrued expenses and other current liabilities	(1,448)	(1,546)
Deferred revenue	(4)	(1,218)
Operating lease liabilities	(6,021)	(5,004)
Other liabilities	(2,670)	(2,636)
Net cash used in operating activities	(141,501)	(177,647)
Cash flows from investing activities
Purchases of marketable debt securities	(173,916)	(67,925)
Maturities of marketable debt securities	238,446	231,753
Sales of equity securities		1,975
Purchases of property and equipment	(1,357)	(8,834)
Net cash provided by investing activities	63,173	156,969
Cash flows from financing activities
Proceeds from exercise of stock options	1,474	1,312
Taxes paid related to net settlement of stock-based awards	(910)	(419)
Proceeds from issuance of common stock under employee stock purchase plan	1,191	1,826
Proceeds from public offering of common stock and pre-funded warrants, net of issuance costs	131,067
Proceeds from private placement of common stock, net of issuance costs		4,874
Offering expenses related to at-the-market offering program	(158)	(51)
Repayments under liability related to sale of future royalties, net of imputed interest	(32,241)	(30,546)
Net cash provided by (used in) financing activities	100,423	(23,004)
Net increase (decrease) in cash and cash equivalents and restricted cash	22,095	(43,682)
Cash and cash equivalents and restricted cash
Beginning of period	36,552	98,982
End of period	$ 58,647	$ 55,300

License and Collaboration Agreements - Summary of Changes in Balances of Receivables, Contract Assets and Deferred Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accounts receivable, net, current and non-current:
Balance, beginning of period	$ 23,273	$ 22,523	$ 25,491	$ 29,586
Balance, end of period	24,008	29,121	24,008	29,121
Contract assets:
Balance, beginning of period	194	2,000
Balance, end of period	259	2,000	259	2,000
Deferred revenue:
Balance, beginning of period	21	448	148	1,829
Balance, end of period	144	442	144	442
Revenue recognized during the period from:
Amounts included in deferred revenue at beginning of period	21	28	148	1,409
Performance obligations satisfied in previous periods	$ 23,875	$ 28,365	$ 60,912	$ 65,405

Stock-based Compensation - Summary of Stock Option Activity (Detail) - 2014 and 2015 Equity Incentive Plan [Member] $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2024 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Shares Outstanding, Beginning Balance \| shares	8,581
Shares, Granted \| shares	2,263
Shares, Exercised \| shares	(281)
Shares, Cancelled or forfeited \| shares	(546)
Shares Outstanding, Ending Balance \| shares	10,017	8,581
Shares, Exercisable \| shares	6,609
Shares, Vested and expected to vest \| shares	10,017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-average Exercise Price Outstanding, Beginning Balance \| $ / shares	$ 32.62
Weighted-average Exercise Price, Granted \| $ / shares	16.24
Weighted-average Exercise Price, Exercised \| $ / shares	5.25
Weighted-average Exercise Price, Cancelled or forfeited \| $ / shares	35.56
Weighted-average Exercise Price, Outstanding, Ending Balance \| $ / shares	29.53	$ 32.62
Weighted-average Exercise Price, Exercisable \| $ / shares	34.38
Weighted-average Exercise Price, Vested and expected to vest \| $ / shares	$ 29.53
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-average Remaining Contractual Life (Years) Outstanding	6 years 4 months 24 days	6 years 2 months 12 days
Weighted-average Remaining Contractual Life (Years), Exercisable	5 years 1 month 6 days
Weighted-average Remaining Contractual Life (Years), Vested and expected to vest	6 years 4 months 24 days
Aggregate Intrinsic Value Outstanding \| $	$ 529	$ 7,011
Aggregate Intrinsic Value, Exercisable \| $	529
Aggregate Intrinsic Value, Vested and expected to vest \| $	$ 529

Liability Related to Sale of Future Royalties -Schedule of Activity Within Liability Related to Sale of Future Royalties (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Liability Related To Sale Of Future Royalties [Line Items]
Current portion of liability related to sale of future royalties	$ (26,697)	$ (50,567)
Liability related to sale of future royalties, non-current	35,052	$ 43,485
Royalty Agreements
Liability Related To Sale Of Future Royalties [Line Items]
Beginning balance	94,052
Zolgensma royalties paid to HCR	(35,072)
Interest expense recognized	2,769
Ending balance	61,749
Current portion of liability related to sale of future royalties	(26,697)
Liability related to sale of future royalties, non-current	$ 35,052

Summary of Significant Accounting Policies - Summary of Reconciliation of Cash and Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Accounting Policies [Abstract]
Cash and cash equivalents	$ 56,617	$ 34,522	$ 53,045
Restricted cash	2,030	$ 2,030	2,255
Total cash and cash equivalents and restricted cash	$ 58,647		$ 55,300

Net Loss Per Share (Tables)

9 Months Ended

Sep. 30, 2024

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 and Nine Months Ended September 30,
	2024		2023
Stock options issued and outstanding		10,017		8,856
Unvested restricted stock units outstanding		2,035		1,394
Employee stock purchase plan		47		36
		12,099		10,286

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current assets
Cash and cash equivalents	$ 56,617	$ 34,522
Marketable securities	198,843	240,736
Accounts receivable, net	23,604	24,790
Prepaid expenses	11,002	14,520
Other current assets	23,330	20,403
Total current assets	313,396	334,971
Marketable securities	23,108	38,871
Accounts receivable	404	701
Property and equipment, net	120,551	132,103
Operating lease right-of-use assets	55,293	60,487
Restricted cash	2,030	2,030
Other assets	4,332	4,807
Total assets	519,114	573,970
Current liabilities
Accounts payable	19,522	22,786
Accrued expenses and other current liabilities	48,642	49,703
Deferred revenue	144	148
Operating lease liabilities	7,720	7,068
Liability related to sale of future royalties	26,697	50,567
Total current liabilities	102,725	130,272
Operating lease liabilities	76,342	82,222
Liability related to sale of future royalties	35,052	43,485
Other liabilities	3,579	6,249
Total liabilities	217,698	262,228
Stockholders’ equity
Preferred stock; $0.0001 par value; 10,000 shares authorized, no shares issued and outstanding at September 30, 2024 and December 31, 2023
Common stock; $0.0001 par value; 100,000 shares authorized at September 30, 2024 and December 31, 2023; 49,534 and 44,046 shares issued and outstanding at September 30, 2024 and December 31, 2023, respectively	5	4
Additional paid-in capital	1,182,956	1,021,214
Accumulated other comprehensive loss	(582)	(4,429)
Accumulated deficit	(880,963)	(705,047)
Total stockholders’ equity	301,416	311,742
Total liabilities and stockholders’ equity	$ 519,114	$ 573,970

Leases - Additional Information (Detail) - USD ($)	3 Months Ended			9 Months Ended
Leases - Additional Information (Detail) - USD ($)	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Other Commitments [Line Items]
Total undiscounted payments	$ 1,300,000			$ 1,300,000
Impairment losses of long-lived assets				2,101,000
New York Sublease [Member]
Other Commitments [Line Items]
Sublease income	100,000			200,000
Carrying value of the asset		$ 3,400,000
Estimated fair value of asset		1,300,000
Impairment losses of long-lived assets	$ 0	2,100,000	$ 0	$ 2,100,000	$ 0
Impairment losses recorded to right-of-use assets		1,400,000
Impairment losses recorded to property and equipment		$ 700,000

Marketable Securities - Additional Information (Detail)	3 Months Ended		9 Months Ended
Marketable Securities - Additional Information (Detail)	Sep. 30, 2024 USD ($) Security	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) Security	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Investments, Debt and Equity Securities [Abstract]
Available for sale debt securities remaining maturities greater than three years	$ 0		$ 0		$ 0
Number of investment grade fixed income debt security \| Security	36		36
Allowance for credit loss	$ 0		$ 0		$ 0
Realized gains or losses on available-for-sales securities	$ 0	$ 0	$ 0	$ 0

Capitalization - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended
	Mar. 31, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Schedule of Capitalization [Line Items]
Proceeds from private placement						$ 4,874
Percentage of common stock owned	9.99%
Percentage of voting power	9.99%
Maximum [Member]
Schedule of Capitalization [Line Items]
Percentage of common stock owned	19.99%
Minimum [Member]
Schedule of Capitalization [Line Items]
Percentage of common stock owned	4.99%
March 2024 Public Offering [Member]
Schedule of Capitalization [Line Items]
Number of shares sold	4,565,260
Purchase price of share	$ 23
Net proceeds from issuance of common stock	$ 131,100
March 2024 Public Offering [Member] \| Pre Funded Warrants [Member]
Schedule of Capitalization [Line Items]
Purchase price of share	$ 22.9999
Number of warrants issued	1,521,740
Exercise price of warrants	$ 0.0001
Pre-funded warrants exercised			0		0
Pre-funded warrants remained outstanding			1,324,740		1,324,740
At the Market Offering Program
Schedule of Capitalization [Line Items]
Aggregate offering price		$ 150,000
Common Stock [Member] \| Private Placement [Member]
Schedule of Capitalization [Line Items]
Number of shares sold				257,000		257,000
Common Stock [Member] \| March 2024 Public Offering [Member]
Schedule of Capitalization [Line Items]
Number of shares sold			197,000		197,000
Common Stock [Member] \| At the Market Offering Program
Schedule of Capitalization [Line Items]
Number of shares sold					0

Fair Value Measurements

9 Months Ended

Sep. 30, 2024

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. Fair Value Measurements

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 fair value hierarchy discussed in Note 2 (in thousands):


	Level 1		Level 2		Level 3		Total
September 30, 2024
Cash equivalents:
Money market mutual funds	$	—	$	43,771	$	—	$	43,771
Total cash equivalents		—		43,771		—		43,771
Marketable securities:
U.S. government and agency securities		—		50,133		—		50,133
Certificates of deposit		—		4,389		—		4,389
Corporate bonds		—		167,429		—		167,429
Total marketable securities		—		221,951		—		221,951
Total cash equivalents and marketable securities	$	—	$	265,722	$	—	$	265,722


	Level 1		Level 2		Level 3		Total
December 31, 2023
Cash equivalents:
Money market mutual funds	$	—	$	13,024	$	—	$	13,024
Total cash equivalents		—		13,024		—		13,024
Marketable securities:
U.S. government and agency securities		—		70,569		—		70,569
Certificates of deposit		—		6,466		—		6,466
Corporate bonds		—		202,572		—		202,572
Total marketable securities		—		279,607		—		279,607
Total cash equivalents and marketable securities	$	—	$	292,631	$	—	$	292,631

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 and certain non-current payables reported as other liabilities are recorded at their present values using a discount rate that is based on prevailing market rates on the date the amounts were 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 September 30, 2024 to determine the present value of these instruments. 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 7, 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 by the Company over the life of the arrangement, which are considered Level 3 inputs.

Long-lived assets, if determined to be not recoverable and impaired, are measured at fair value on a nonrecurring basis using Level 3 inputs. Please refer to Note 6 for further information on nonrecurring fair value measurements of long-lived assets during the three and nine months ended September 30, 2024 and 2023.

- 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

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 107
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-107

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
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-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 940
-SubTopic 820
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478119/940-820-50-1

+ Details

License and Collaboration Agreements - Schedule Of License Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Interest income from licensing	$ 25	$ 56	$ 91	$ 166
Novartis Gene Therapies [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total license and royalty revenue	23,872	28,364	60,849	63,454
Interest income from licensing	6	7	20	22
Zolgensma Royalties [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total license and royalty revenue	$ 23,872	$ 28,364	$ 60,849	$ 63,454

- Definition

+ References

+ Details

Stock-based Compensation - Summary of Unvested RSUs Activity Under 2015 Plan (Detail) - Restricted Stock Units (RSUs)	9 Months Ended
	Sep. 30, 2024 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested balance at December 31, 2023 \| shares	1,309,000
Shares, Granted \| shares	1,188,000
Vested \| shares	(390,000)
Forfeited \| shares	(72,000)
Unvested balance at June 30, 2024 \| shares	2,035,000
Weighted-average Grant Date Fair Value, Unvested Beginning Balance \| $ / shares	$ 25.89
Weighted-average Grant Date Fair Value, Granted \| $ / shares	16.22
Weighted-average Grant Date Fair Value, Vested \| $ / shares	27.2
Weighted-average Grant Date Fair Value, Forfeited \| $ / shares	22.45
Weighted-average Grant Date Fair Value, Unvested Ending Balance \| $ / shares	$ 20.11

Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2024

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
September 30, 2024
U.S. government and agency securities	$	50,350	$	16	$	(233	)	$	50,133
Certificates of deposit		4,404		—		(15	)		4,389
Corporate bonds		166,919		583		(73	)		167,429
	$	221,673	$	599	$	(321	)	$	221,951


	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2023
U.S. government and agency securities	$	71,811	$	6	$	(1,248	)	$	70,569
Certificates of deposit		6,572		—		(106	)		6,466
Corporate bonds		204,793		143		(2,364	)		202,572
	$	283,176	$	149	$	(3,718	)	$	279,607

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
September 30, 2024
U.S. government and agency securities	$	—	$	—		$	30,252	$	(233	)	$	30,252	$	(233	)
Certificates of deposit		484		(1	)		3,170		(14	)		3,654		(15	)
Corporate bonds		4,995		(1	)		21,290		(72	)		26,285		(73	)
	$	5,479	$	(2	)	$	54,712	$	(319	)	$	60,191	$	(321	)


	Less than 12 Months					12 Months or Greater					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
December 31, 2023
U.S. government and agency securities	$	12,877	$	(16	)	$	52,686	$	(1,232	)	$	65,563	$	(1,248	)
Certificates of deposit		965		(2	)		5,257		(104	)		6,222		(106	)
Corporate bonds		25,051		(48	)		144,642		(2,316	)		169,693		(2,364	)
	$	38,893	$	(66	)	$	202,585	$	(3,652	)	$	241,478	$	(3,718	)

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-9

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

+ Details

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	Sep. 30, 2024	Dec. 31, 2023
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 5,479	$ 38,893
Less than 12 Months, Unrealized Losses	(2)	(66)
12 Months or Greater, Fair Value	54,712	202,585
12 Months or Greater, Unrealized Losses	(319)	(3,652)
Total, Fair Value	60,191	241,478
Total, Unrealized Losses	(321)	(3,718)
U.S. Government and Agency Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value		12,877
Less than 12 Months, Unrealized Losses		(16)
12 Months or Greater, Fair Value	30,252	52,686
12 Months or Greater, Unrealized Losses	(233)	(1,232)
Total, Fair Value	30,252	65,563
Total, Unrealized Losses	(233)	(1,248)
Certificates of Deposit [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	484	965
Less than 12 Months, Unrealized Losses	(1)	(2)
12 Months or Greater, Fair Value	3,170	5,257
12 Months or Greater, Unrealized Losses	(14)	(104)
Total, Fair Value	3,654	6,222
Total, Unrealized Losses	(15)	(106)
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	4,995	25,051
Less than 12 Months, Unrealized Losses	(1)	(48)
12 Months or Greater, Fair Value	21,290	144,642
12 Months or Greater, Unrealized Losses	(72)	(2,316)
Total, Fair Value	26,285	169,693
Total, Unrealized Losses	$ (73)	$ (2,364)

Fair Value Measurements - Schedule of Fair Value of Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Marketable securities:
Fair Value	$ 221,951	$ 279,607
Cash Equivalents and Marketable Securities [Member]
Marketable securities:
Total cash equivalents and marketable securities	265,722	292,631
Corporate Bonds [Member]
Marketable securities:
Fair Value	167,429	202,572
Cash Equivalents [Member]
Cash equivalents:
Total cash equivalents	43,771	13,024
US Government and Agency Securities [Member]
Marketable securities:
Fair Value	50,133	70,569
Certificates of Deposit [Member]
Marketable securities:
Fair Value	4,389	6,466
Money Market Mutual Funds [Member] \| Cash Equivalents [Member]
Cash equivalents:
Total cash equivalents	43,771	13,024
Level 2 [Member]
Marketable securities:
Fair Value	221,951	279,607
Level 2 [Member] \| Cash Equivalents and Marketable Securities [Member]
Marketable securities:
Total cash equivalents and marketable securities	265,722	292,631
Level 2 [Member] \| Corporate Bonds [Member]
Marketable securities:
Fair Value	167,429	202,572
Level 2 [Member] \| Cash Equivalents [Member]
Cash equivalents:
Total cash equivalents	43,771	13,024
Level 2 [Member] \| US Government and Agency Securities [Member]
Marketable securities:
Fair Value	50,133	70,569
Level 2 [Member] \| Certificates of Deposit [Member]
Marketable securities:
Fair Value	4,389	6,466
Level 2 [Member] \| Money Market Mutual Funds [Member] \| Cash Equivalents [Member]
Cash equivalents:
Total cash equivalents	$ 43,771	$ 13,024

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (59,597)	$ (61,868)	$ (175,916)	$ (200,605)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
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-Name Accounting Standards Codification
-Section 50
-Paragraph 9
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-URI https://asc.fasb.org/1943274/2147483443/250-10-50-9

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
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-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476176/805-60-65-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Section 65
-Paragraph 2
-Subparagraph (g)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478666/740-323-65-2

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 10
-Name Accounting Standards Codification
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-Subparagraph (SX 210.4-08(g)(1)(ii))
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
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-Name Accounting Standards Codification
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-Subparagraph (f)
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-URI https://asc.fasb.org/1943274/2147482907/825-10-50-28

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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-URI https://asc.fasb.org/1943274/2147482765/220-10-50-6

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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-URI https://asc.fasb.org/1943274/2147483443/250-10-50-3

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
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-Subparagraph (b)(2)
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-8

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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-Subparagraph (a)
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-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
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-Name Accounting Standards Codification
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
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Reference 17: http://www.xbrl.org/2003/role/exampleRef
-Topic 946
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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Reference 20: http://www.xbrl.org/2003/role/disclosureRef
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Reference 21: http://www.xbrl.org/2003/role/disclosureRef
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Reference 22: http://www.xbrl.org/2003/role/disclosureRef
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Reference 23: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 24: http://www.xbrl.org/2003/role/disclosureRef
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Reference 25: http://www.xbrl.org/2003/role/disclosureRef
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Reference 26: http://www.xbrl.org/2003/role/disclosureRef
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Reference 27: http://www.xbrl.org/2003/role/disclosureRef
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Reference 28: http://www.xbrl.org/2003/role/disclosureRef
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Reference 29: http://www.xbrl.org/2003/role/disclosureRef
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Reference 30: http://www.xbrl.org/2003/role/disclosureRef
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Reference 31: http://www.xbrl.org/2003/role/disclosureRef
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Reference 33: http://www.xbrl.org/2003/role/disclosureRef
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Reference 34: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 35: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1A

Reference 36: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1B

Reference 37: http://fasb.org/us-gaap/role/ref/legacyRef
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-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

+ Details

Supplemental Disclosures - Schedule of Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Other Current Assets [Line Items]
Due from related parties, current	$ 4,942	$ 4,587
Other Assets, Current, Total	23,330	20,403
Other Current Assets [Member]
Other Current Assets [Line Items]
Accrued Interest on Investments	1,578	1,551
Other	1,450	1,107
Other Current Assets [Member] \| Related Party [Member]
Other Current Assets [Line Items]
Due from related parties, current	$ 20,302	$ 17,745

Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2024

Accounting Policies [Abstract]

Summary of Reconciliation of Cash and Cash Equivalents and Restricted Cash

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


	As of September 30,
	2024		2023
Cash and cash equivalents	$	56,617	$	53,045
Restricted cash		2,030		2,255
Total cash and cash equivalents and restricted cash	$	58,647	$	55,300

Stock-based Compensation

9 Months Ended

Sep. 30, 2024

Share-Based Payment Arrangement [Abstract]

Stock-based Compensation

10. Stock-based Compensation

Effective in January 2024, an additional 1,761,849 shares were authorized for issuance under the 2015 Equity Incentive Plan (the 2015 Plan). As of September 30, 2024, the total number of shares of common stock authorized for issuance under the 2015 Plan and the 2014 Stock Plan (the 2014 Plan) was 19,118,989, of which 1,511,556 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 September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Stock options	$	6,051	$	7,275	$	17,969	$	22,868
Restricted stock units		3,755		2,843		10,536		8,475
Employee stock purchase plan		78		101		416		586
	$	9,884	$	10,219	$	28,921	$	31,929

As of September 30, 2024, the Company had $69.5 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 2.4 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 September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Research and development	$	4,301	$	5,131	$	13,893	$	16,670
General and administrative		5,583		5,088		15,028		15,259
	$	9,884	$	10,219	$	28,921	$	31,929

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, 2023		8,581		$	32.62		6.2	$	7,011
Granted		2,263		$	16.24
Exercised		(281	)	$	5.25
Cancelled or forfeited		(546	)	$	35.56
Outstanding at September 30, 2024		10,017		$	29.53		6.4	$	529
Exercisable at September 30, 2024		6,609		$	34.38		5.1	$	529
Vested and expected to vest at September 30, 2024		10,017		$	29.53		6.4	$	529

The weighted-average grant date fair value per share of options granted during the nine months ended September 30, 2024 was $10.06. During the nine months ended September 30, 2024, the total number of stock options exercised was 280,753, resulting in total proceeds of $1.5 million. The total intrinsic value of options exercised during the nine months ended September 30, 2024 was $3.0 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, 2023		1,309		$	25.89
Granted		1,188		$	16.22
Vested		(390	)	$	27.20
Forfeited		(72	)	$	22.45
Unvested balance at September 30, 2024		2,035		$	20.11

The total intrinsic value of restricted stock units vested during the nine months ended September 30, 2024 was $6.7 million.

Employee Stock Purchase Plan

As of September 30, 2024, the total number of shares of common stock authorized for issuance under the 2015 ESPP was 1,426,994, of which 912,964 remained available for future issuance. During the nine months ended September 30, 2024, 105,400 shares of common stock were issued under the 2015 ESPP.

Liability Related to Sale of Future Royalties (Tables)

9 Months Ended

Sep. 30, 2024

Schedule of Changes in 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, 2023	$	94,052
Zolgensma royalties paid to HCR		(35,072	)
Interest expense recognized		2,769
Balance at September 30, 2024		61,749
Current portion of liability related to sale of future royalties		(26,697	)
Liability related to sale of future royalties, non-current	$	35,052

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Public Offering [Member]	Private Placement [Member]	Common Stock [Member]	Common Stock [Member] Public Offering [Member]	Common Stock [Member] Private Placement [Member]	Additional paid in capital [Member]	Additional paid in capital [Member] Public Offering [Member]	Additional paid in capital [Member] Private Placement [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Balances at Dec. 31, 2022	$ 516,195			$ 4			$ 973,145			$ (15,401)	$ (441,553)
Balances (Shares) at Dec. 31, 2022				43,299
Vesting of restricted stock units, net of tax	(419)						(419)
Vesting of restricted stock units, net of tax, shares				161
Exercise of stock options, net of tax	1,312						1,312
Exercise of stock options, net of tax, shares				171
Issuance of common stock under employee stock purchase plan	1,826						1,826
Issuance of common stock under employee stock purchase plan, shares				103
Issuance of common stock and pre-funded warrants			$ 4,874						$ 4,874
Issuance of common stock and pre-funded warrants, shares						257
Stock-based compensation expense	31,929						31,929
Unrealized gain on available-for-sale securities, net	7,988									7,988
Net loss	(200,605)										(200,605)
Balances at Sep. 30, 2023	363,100			$ 4			1,012,667			(7,413)	(642,158)
Balances (Shares) at Sep. 30, 2023				43,991
Balances at Jun. 30, 2023	405,855			$ 4			996,239			(10,098)	(580,290)
Balances (Shares) at Jun. 30, 2023				43,621
Vesting of restricted stock units, net of tax, shares				34
Exercise of stock options, net of tax	92						92
Exercise of stock options, net of tax, shares				6
Issuance of common stock under employee stock purchase plan	1,243						1,243
Issuance of common stock under employee stock purchase plan, shares				73
Issuance of common stock and pre-funded warrants			$ 4,874						$ 4,874
Issuance of common stock and pre-funded warrants, shares						257
Stock-based compensation expense	10,219						10,219
Unrealized gain on available-for-sale securities, net	2,685									2,685
Net loss	(61,868)										(61,868)
Balances at Sep. 30, 2023	363,100			$ 4			1,012,667			(7,413)	(642,158)
Balances (Shares) at Sep. 30, 2023				43,991
Balances at Dec. 31, 2023	311,742			$ 4			1,021,214			(4,429)	(705,047)
Balances (Shares) at Dec. 31, 2023				44,046
Vesting of restricted stock units, net of tax	(910)						(910)
Vesting of restricted stock units, net of tax, shares				340
Exercise of stock options, net of tax	1,474						1,474
Exercise of stock options, net of tax, shares				281
Exercise of pre-funded warrants				197
Issuance of common stock under employee stock purchase plan	1,191						1,191
Issuance of common stock under employee stock purchase plan, shares				105
Issuance of common stock and pre-funded warrants		$ 131,067			$ 1			$ 131,066
Issuance of common stock and pre-funded warrants, shares					4,565
Stock-based compensation expense	28,921						28,921
Unrealized gain on available-for-sale securities, net	3,847									3,847
Net loss	(175,916)										(175,916)
Balances at Sep. 30, 2024	301,416			$ 5			1,182,956			(582)	(880,963)
Balances (Shares) at Sep. 30, 2024				49,534
Balances at Jun. 30, 2024	348,267			$ 5			1,171,894			(2,266)	(821,366)
Balances (Shares) at Jun. 30, 2024				49,317
Vesting of restricted stock units, net of tax, shares				31
Exercise of stock options, net of tax	398						398
Exercise of stock options, net of tax, shares				108
Issuance of common stock under employee stock purchase plan	780						780
Issuance of common stock under employee stock purchase plan, shares				78
Stock-based compensation expense	9,884						9,884
Unrealized gain on available-for-sale securities, net	1,684									1,684
Net loss	(59,597)										(59,597)
Balances at Sep. 30, 2024	$ 301,416			$ 5			$ 1,182,956			$ (582)	$ (880,963)
Balances (Shares) at Sep. 30, 2024				49,534

Nature of Business

9 Months Ended

Sep. 30, 2024

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's investigational gene therapies use adeno-associated virus (AAV) vectors from its proprietary gene delivery platform (NAV Technology Platform). The NAV® Technology Platform consists of exclusive rights to a large portfolio of AAV vectors, including commonly used AAV8 and AAV9. The Company has developed a broad pipeline of gene therapy product candidates using the NAV Technology Platform as a one-time treatment to address an array of diseases. In addition to its internal product development efforts, the Company also selectively licenses the NAV Technology Platform and other intellectual property rights to other leading biotechnology and pharmaceutical companies (NAV Technology Licensees). As of September 30, 2024, the NAV Technology Platform was being applied by NAV Technology Licensees in one commercial product, Zolgensma®, and in the preclinical and clinical development of a number of other 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.

The Company has incurred cumulative losses since inception and as of September 30, 2024, had generated an accumulated deficit of $881.0 million. The Company's ability to transition to recurring profitability is dependent upon achieving a level of revenues adequate to support its 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, will continue to need to raise additional capital through equity offerings, licensing and collaboration arrangements, or other non-dilutive financings. There is no assurance that the Company will be able to raise sufficient capital or obtain financing on favorable terms, or at all. If the Company is unable to raise capital sufficient to meet its working capital needs in the future, it may be forced to delay expenditures, reduce the scope of its development activities or make other changes to its operating plans. As of September 30, 2024, the Company had cash, cash equivalents and marketable securities of $278.6 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.

Capitalization

9 Months Ended

Sep. 30, 2024

Equity [Abstract]

Capitalization

8. Capitalization

March 2024 Public Offering

In March 2024, the Company completed a public offering of 4,565,260 shares of its common stock at a price of $23.00 per share and 1,521,740 pre-funded warrants to purchase shares of its common stock at a price of $22.9999 per pre-funded warrant, which equaled the public offering price per share of the common stock less the $0.0001 exercise price of each pre-funded warrant. The aggregate net proceeds received by the Company from the offering were $131.1 million, net of underwriting discounts and commissions and offering expenses payable by the Company.

The rights and privileges of the pre-funded warrants issued under the March 2024 offering are set forth in the warrant agreement between the Company and each of the respective warrant holders. The pre-funded warrants are exercisable at the option of the warrant holder at any time and do not expire. However, as set forth in the warrant agreements with each holder, the number of pre-funded warrants that may be exercised at any given time may be limited if, upon exercise, the warrant holder and any of its affiliates would beneficially own more than 9.99% of the Company’s common stock, or have voting power of more than 9.99% of the Company's common stock. The limitation threshold may be increased or decreased by the warrant holder, with advance notice to the Company, to any other percentage not less than 4.99% nor in excess of 19.99%. Pre-funded warrants do not provide any of the rights or privileges provided by the Company's common stock, including any voting rights, until the pre-funded warrants are exercised and settled in underlying shares of common stock.

The Company evaluated the pre-funded warrants issued under the March 2024 offering and concluded the warrants are indexed to the Company's common stock, meet the criteria to be classified as equity and are not subject to remeasurement. The proceeds received from the issuance of the pre-funded warrants were recorded as additional paid-in capital. The Company issued 197,000 shares of common stock upon the exercise of pre-funded warrants during the nine months ended September 30, 2024. There were no exercises of pre-funded warrants during the three months ended September 30, 2024. As of September 30, 2024, 1,324,740 pre-funded warrants remained outstanding.

At-the-Market Offering Program

In September 2023, the Company entered into an ATM Equity OfferingSM Sales Agreement with BofA Securities, Inc. (BofA) pursuant to which the Company may offer and sell shares of its common stock having an aggregate offering price of up to $150.0 million from time to time through BofA, acting as the Company's sales agent (the ATM Program). As of September 30, 2024, no shares of common stock had been sold under the ATM Program.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
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-Paragraph 13
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-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 505
-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478448/946-505-50-6

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
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-Section 50
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-URI https://asc.fasb.org/1943274/2147480237/815-40-50-6

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Paragraph 1
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Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2024

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation and Principles of Consolidation

Use of Estimates

Reclassifications

Restricted Cash


	As of September 30,
	2024		2023
Cash and cash equivalents	$	56,617	$	53,045
Restricted cash		2,030		2,255
Total cash and cash equivalents and restricted cash	$	58,647	$	55,300

Accounts Receivable

Leases

Impairment of Long-lived Assets

Fair Value Measurements

•

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.

Pre-funded Warrants

Net Loss Per Share

Recent Accounting Pronouncements

Recently Adopted Accounting Pronouncements

The Company did not adopt any new accounting standards during the three and nine months ended September 30, 2024 and 2023 which had a material impact on the consolidated financial statements.

Recent Accounting Pronouncements Not Yet Adopted