Adverum Biotechnologies (ADVM) 10-Q 10 Aug 23 2023 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2023	Aug. 04, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2023
Document Transition Report	false
Entity File Number	001-36579
Entity Registrant Name	Adverum Biotechnologies, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-5258327
Entity Address, Address Line One	100 Cardinal Way
Entity Address, City or Town	Redwood City
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94063
City Area Code	650
Local Phone Number	656-9323
Title of 12(b) Security	Common Stock, $0.0001 par value
Trading Symbol	ADVM
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		100,993,010
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001501756
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 111,187	$ 68,431
Short-term investments	30,266	117,158
Prepaid expenses and other current assets	5,690	5,006
Total current assets	147,143	190,595
Operating lease right-of-use assets	58,287	78,934
Property and equipment, net	32,041	34,927
Restricted cash	2,650	2,503
Deposit and other long-term assets	1,308	1,413
Total assets	241,429	308,372
Current liabilities:
Accounts payable	1,418	2,238
Accrued expenses and other current liabilities	17,704	16,767
Lease liability, current portion	25,396	13,241
Total current liabilities	44,518	32,246
Lease liability, net of current portion	65,756	93,561
Other non-current liabilities	0	1,047
Total liabilities	110,274	126,854
Stockholders’ equity:
Preferred stock	0	0
Common stock	10	10
Additional paid-in capital	994,929	985,651
Accumulated other comprehensive loss	(606)	(1,531)
Accumulated deficit	(863,178)	(802,612)
Total stockholders’ equity	131,155	181,518
Total liabilities and stockholders’ equity	$ 241,429	$ 308,372

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Income Statement [Abstract]
License revenue	$ 0	$ 0	$ 3,600	$ 0
Operating expenses:
Research and development	20,599	30,265	41,658	53,229
General and administrative	12,466	13,760	25,246	28,929
Total operating expenses	33,065	44,025	66,904	82,158
Operating loss	(33,065)	(44,025)	(63,304)	(82,158)
Other income, net	1,576	283	2,776	527
Net loss before income taxes	(31,489)	(43,742)	(60,528)	(81,631)
Income tax provision	(21)	(19)	(38)	(38)
Net loss	(31,510)	(43,761)	(60,566)	(81,669)
Other comprehensive income (loss):
Net unrealized gain/(loss) on marketable securities	198	(339)	937	(1,062)
Foreign currency translation adjustment	(5)	(34)	(12)	(20)
Comprehensive loss	$ (31,317)	$ (44,134)	$ (59,641)	$ (82,751)
Net loss per share — basic (in USD per share)	$ (0.31)	$ (0.44)	$ (0.60)	$ (0.83)
Net loss per share — diluted (in USD per share)	$ (0.31)	$ (0.44)	$ (0.60)	$ (0.83)
Weighted-average common shares used to compute net loss per share - basic (in shares)	100,768	99,000	100,537	98,799
Weighted-average common shares used to compute net loss per share - diluted (in shares)	100,768	99,000	100,537	98,799

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss)/Income	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2021		98,381,000
Beginning balance at Dec. 31, 2021	$ 316,185	$ 10	$ 964,965	$ (714)	$ (648,076)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	5,381		5,381
Common stock issued upon exercise of stock options (in shares)		15,000
Common stock issued upon exercise of stock options	3		3
Common stock issued upon release of restricted stock units (in shares)		371,000
Foreign currency translation adjustments	14			14
Unrealized gain on marketable securities, net	(723)			(723)
Net loss	(37,908)				(37,908)
Ending balance (in shares) at Mar. 31, 2022		98,767,000
Ending balance at Mar. 31, 2022	282,952	$ 10	970,349	(1,423)	(685,984)
Beginning balance (in shares) at Dec. 31, 2021		98,381,000
Beginning balance at Dec. 31, 2021	316,185	$ 10	964,965	(714)	(648,076)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation adjustments	(20)
Unrealized gain on marketable securities, net	(1,062)
Net loss	(81,669)
Ending balance (in shares) at Jun. 30, 2022		99,271,000
Ending balance at Jun. 30, 2022	244,122	$ 10	975,653	(1,796)	(729,745)
Beginning balance (in shares) at Mar. 31, 2022		98,767,000
Beginning balance at Mar. 31, 2022	282,952	$ 10	970,349	(1,423)	(685,984)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	4,942		4,942
Common stock issued upon release of restricted stock units (in shares)		5,000
Common stock issued under employee stock purchase plan (in shares)		499,000
Common stock issued under employee stock purchase plan	362		362
Foreign currency translation adjustments	(34)			(34)
Unrealized gain on marketable securities, net	(339)			(339)
Net loss	(43,761)				(43,761)
Ending balance (in shares) at Jun. 30, 2022		99,271,000
Ending balance at Jun. 30, 2022	244,122	$ 10	975,653	(1,796)	(729,745)
Beginning balance (in shares) at Dec. 31, 2022		100,117,000
Beginning balance at Dec. 31, 2022	181,518	$ 10	985,651	(1,531)	(802,612)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	4,563		4,563
Common stock issued upon release of restricted stock units (in shares)		456,000
Foreign currency translation adjustments	(7)			(7)
Unrealized gain on marketable securities, net	739			739
Net loss	(29,056)				(29,056)
Ending balance (in shares) at Mar. 31, 2023		100,573,000
Ending balance at Mar. 31, 2023	157,757	$ 10	990,214	(799)	(831,668)
Beginning balance (in shares) at Dec. 31, 2022		100,117,000
Beginning balance at Dec. 31, 2022	$ 181,518	$ 10	985,651	(1,531)	(802,612)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued upon exercise of stock options (in shares)	0
Foreign currency translation adjustments	$ (12)
Unrealized gain on marketable securities, net	937
Net loss	(60,566)
Ending balance (in shares) at Jun. 30, 2023		100,993,000
Ending balance at Jun. 30, 2023	131,155	$ 10	994,929	(606)	(863,178)
Beginning balance (in shares) at Mar. 31, 2023		100,573,000
Beginning balance at Mar. 31, 2023	157,757	$ 10	990,214	(799)	(831,668)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	4,469		4,469
Common stock issued upon release of restricted stock units (in shares)		2,000
Common stock issued under employee stock purchase plan (in shares)		418,000
Common stock issued under employee stock purchase plan	246		246
Foreign currency translation adjustments	(5)			(5)
Unrealized gain on marketable securities, net	198			198
Net loss	(31,510)				(31,510)
Ending balance (in shares) at Jun. 30, 2023		100,993,000
Ending balance at Jun. 30, 2023	$ 131,155	$ 10	$ 994,929	$ (606)	$ (863,178)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Cash flows from operating activities:
Net loss	$ (60,566)	$ (81,669)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,126	3,028
Stock-based compensation expense	9,032	10,323
Net (accretion) amortization of (discount) premium on marketable securities	(1,675)	258
Non-cash lease expense	6,936	2,234
Loss on disposal of property and equipment	0	101
Impairment of long-lived assets	0	2,011
Other	(306)	(76)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	775	(4,165)
Other assets	105	(3,403)
Accounts payable	(944)	3,216
Accrued expenses and other liabilities	(525)	2,134
Lease liability and lease incentive receivable	(1,619)	8,200
Net cash used in operating activities	(45,661)	(57,808)
Cash flows from investing activities:
Purchases of marketable securities	(20,232)	(57,674)
Maturities of marketable securities	108,909	183,599
Purchases of property and equipment	(121)	(10,807)
Net cash provided by investing activities	88,556	115,118
Cash flows from financing activities:
Proceeds from issuance of common stock pursuant to option exercises	0	3
Payment of deferred offering costs	(238)	0
Proceeds from employee stock purchase plan	246	362
Net cash provided by financing activities	8	365
Net increase in cash and cash equivalents and restricted cash	42,903	57,675
Cash and cash equivalents and restricted cash at beginning of period	70,934	36,698
Cash and cash equivalents and restricted cash at end of period	113,837	94,373
Cash and cash equivalents	111,187	91,870
Restricted cash	2,650	2,503
Cash and cash equivalents and restricted cash at end of period	113,837	94,373
Supplemental schedule of noncash investing and financing information
Remeasurement of operating lease right-of-use assets	13,711	0
Fixed assets in accounts payable, accrued expenses and other current liabilities	496	908
Deferred offering costs included in accounts payable	$ 107	$ 0

Organization and Basis of Prese

Organization and Basis of Presentation	6 Months Ended
	Jun. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation Adverum Biotechnologies, Inc. (the “Company” or “Adverum”) was incorporated in Delaware on July 17, 2006 and is headquartered in Redwood City, California. The Company aims to establish gene therapy as a new standard of care for a number of highly prevalent ocular diseases. The Company develops gene therapy product candidates intended to provide durable efficacy by inducing sustained expression of a therapeutic protein. The Company has not generated any revenue from the sale of products since its inception. The Company has experienced net losses since its inception and had an accumulated deficit of $863.2 million as of June 30, 2023. The Company expects to incur losses and have negative net cash flows from operating activities as it engages in further research and development activities. As of June 30, 2023, the Company had cash, cash equivalents and short-term investments of $141.5 million, which the Company believes will be sufficient to fund its operations for at least twelve months from the date of issuance of these financial statements. Basis of Presentation — The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and follow the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, which are necessary for a fair statement of the Company’s consolidated financial information. The results of operations for the three and six months ended June 30, 2023 are not necessarily indicative of the results to be expected for the full year or any other future period. The balance sheet as of December 31, 2022 is derived from the audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete consolidated financial statements. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2022 filed with the SEC.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Use of Estimates The accompanying condensed consolidated financial statements have been prepared in accordance with U.S. GAAP. The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities and the reported amounts of expenses in the condensed consolidated financial statements and the accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to clinical trial accruals, fair value of assets and liabilities, impairment of long-lived assets, income taxes, and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates. Accrued Interest Receivable Accrued interest receivable related to the Company’s available-for-sale debt securities is presented within prepaid expenses and other current assets on the Company’s condensed consolidated balance sheets. The Company has elected to exclude accrued interest receivable from both the fair value and the amortized cost basis of available-for-sale debt securities for the purposes of identifying and measuring any impairment. The Company writes off accrued interest receivable once it has determined that the asset is not realizable. Any write offs of accrued interest receivable are recorded by reversing interest income, recognizing credit loss expense, or a combination of both. To date, the Company has not written off any accrued interest receivables associated with its available-for-sale debt securities. Recently Adopted Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments – Credit Losses: Measurement of Credit Losses on Financial Instruments (“ Topic 326 ”) and also issued subsequent amendments to the initial guidance: ASU 2018-19, ASU 2019-04, ASU 2019-05, and ASU 2019-11. The standard requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts that affect collectability. Topic 326 also eliminates the concept of “other-than-temporary” impairment when evaluating available-for-sale debt securities and instead focuses on determining whether any impairment is a result of a credit loss or other factors. An entity will recognize an allowance for credit losses on available-for-sale debt securities rather than an other-than-temporary impairment that reduces the cost basis of the investment. The Company adopted ASU 2016-13 on January 1, 2023, using the modified retrospective approach. The adoption of ASU 2016-13 had no significant impact on the Company’s condensed consolidated financial statements.

Fair Value Measurements and Fai

Fair Value Measurements and Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements and Fair Value of Financial Instruments	Fair Value Measurements and Fair Value of Financial Instruments The authoritative guidance on the fair value hierarchy for disclosure of fair value measurements is as follows: Level 1 : Quoted prices in active markets for identical assets or liabilities. Level 2 : Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 : Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The fair value of Level 1 securities is determined using quoted prices in active markets for identical assets. Level 1 securities consist of highly liquid money market funds. Financial assets and liabilities are considered Level 2 when their fair values are determined using inputs that are observable in the market or can be derived principally from or corroborated by observable market data such as pricing for similar securities, recently executed transactions, cash flow models with yield curves, and benchmark securities. In addition, Level 2 financial instruments are valued using comparisons to like-kind financial instruments and models that use readily observable market data as their basis. U.S. government and agency securities, commercial paper, and corporate bonds are valued primarily using market prices of comparable securities, bid/ask quotes, interest rate yields and prepayment spreads and are included in Level 2. The following is a summary of the Company’s cash equivalents and short-term investments: June 30, 2023 Amortized Cost Basis Unrealized Gains Unrealized Estimated Fair Value (In thousands) Level 1: Money market funds $ 10,541 $ — $ — $ 10,541 Level 2: Commercial paper 101,677 — (27) 101,650 U.S. government and agency securities 24,418 2 (143) 24,277 Total cash equivalents and short-term investments 136,636 2 (170) 136,468 Less: cash equivalents (106,218) (2) 18 (106,202) Total short-term investments $ 30,418 $ — $ (152) $ 30,266 December 31, 2022 Amortized Cost Basis Unrealized Gains Unrealized Estimated Fair Value (In thousands) Level 1: Money market funds $ 10,235 $ — $ — $ 10,235 Level 2: Commercial paper 102,722 — (246) 102,476 U.S. government and agency securities 59,487 — (824) 58,663 Corporate bonds 2,059 — (35) 2,024 Total cash equivalents and short-term investments 174,503 — (1,105) 173,398 Less: cash equivalents (56,256) — 16 (56,240) Total short-term investments $ 118,247 $ — $ (1,089) $ 117,158 As of June 30, 2023, all marketable securities have a remaining maturity of less than one year. The aggregate fair value of debt securities in an unrealized loss position at June 30, 2023 and December 31, 2022 was $116.0 million and $155.5 million, respectively, which are highly liquid funds with high credit ratings that have final maturity of less than two years from date of purchase. The Company has not recorded an allowance for credit losses as of June 30, 2023 and December 31, 2022 related to these securities. The accrued interest receivable on available-for-sale marketable securities was immaterial at June 30, 2023 and December 31, 2022. The Company held 27 securities that were in unrealized loss positions as of June 30, 2023. There were no individual securities that were in a significant unrealized loss position as of June 30, 2023 and December 31, 2022. The Company regularly reviews the securities in an unrealized loss position and evaluates the current expected credit loss by considering factors such as historical experience, market data, issuer-specific factors, and current economic conditions. The Company does not intend to sell the investments and it is not more likely than not that the Company will be required to sell the investments before recovery of their amortized cost bases. The Company has not recorded any impairment charges on available-for-sale securities.

License Revenue

License Revenue	6 Months Ended
	Jun. 30, 2023
Revenue from Contract with Customer [Abstract]
License Revenue	License Revenue Lexeo - On January 25, 2021, the Company and Lexeo Therapeutics, Inc (“Lexeo”) entered into a License Agreement pursuant to which the Company granted Lexeo an exclusive, worldwide, royalty-bearing license to certain of the Company’s intellectual property to develop, manufacture, and commercialize a gene therapy product to treat cardiomyopathy due to Friedreich’s Ataxia. Under the terms of the agreement, the Company is eligible to receive additional payments upon the achievement of certain milestones. Additionally, the Company will receive royalty payments on net sales subject to a cap and reductions based on patent expiry, anti-stacking, and a defined royalty floor percentage. In February 2023, Lexeo notified the Company that it achieved the first development milestone; accordingly the Company is eligible to receive additional payments. Therefore, the Company recognized $3.5 million of license revenue during the six months ended June 30, 2023.

Leases

Leases	6 Months Ended
	Jun. 30, 2023
Leases [Abstract]
Leases	Leases Redwood City, California The Company has a lease for facilities in Redwood City, California (“Redwood City Premises”). Related to this lease, the Company provided the landlord with a letter of credit in the amount of $2.5 million, which is classified as restricted cash under long term assets on the Company’s condensed consolidated balance sheets. In March 2023, the Company entered into an amendment to accelerate the expiration of one of its Redwood City Premises under the existing lease from December 31, 2031 to September 30, 2023. Concurrently, the Company entered into an agreement for additional tenant improvement allowance towards its other Redwood City premises. As a result of the modification the Company revalued the lease liability based on the new and remaining lease terms, which resulted in a reduction to the lease liability of $8.3 million, and recognized the remeasurement to the lease liabilities as an adjustment to the right-of-use asset. The estimated value of non-cash consideration, composed primarily of leasehold improvements and furniture and fixtures, was $14.9 million. Durham, North Carolina The Company has an operating lease agreement for a building in Durham, North Carolina (“NC Premises”). The lease commenced in April 2021 when the Company obtained control of the NC Premises, and the lease term expires in October 2037 with two options to extend the lease term for a period of five years each. In April 2023, the Company entered into an amendment to reduce the rent payments for the NC Premises, effective as of May 1, 2023. On October 26, 2021, the Company entered into a sublease agreement with a subtenant for the NC Premises through October 2037, the remainder of the lease term. In line with the amendment to the NC Premises’ lease, sublease rent payments were correspondingly reduced. Sublease income for operating leases is recognized on a cash basis over the lease term based on assessment of probability of collection. Sublease income was $1.4 million and $2.8 million for the three and six months ended June 30, 2023, respectively, and $1.7 million and $3.4 million for the three and six months ended June 30, 2022, respectively. The sublease income is classified as a reduction of rent expense in operating expenses. As of June 30, 2023, undiscounted future non-cancellable lease payments under the lease agreements are as follows (in thousands): Year ending December 31, Operating Leases Sublease Payments Receivable 2023 (remaining six months) $ 20,915 $ 2,573 2024 11,086 5,248 2025 11,448 5,405 2026 11,821 5,567 2027 12,207 5,735 Thereafter 94,653 66,416 Total undiscounted lease payments $ 162,130 $ 90,944 Less: Present value adjustments $ (70,978) Total lease liability $ 91,152

Balance Sheet Components

Balance Sheet Components	6 Months Ended
	Jun. 30, 2023
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	Balance Sheet Components Property and Equipment, Net Property and equipment, net consists of the following: June 30, 2023 December 31, 2022 (In thousands) Leasehold improvements $ 34,376 $ 34,336 Laboratory equipment 14,419 14,382 Computer equipment and software 1,325 1,325 Furniture and fixtures 868 868 Construction in progress 1,173 1,010 Total property and equipment 52,161 51,921 Less accumulated depreciation and amortization (20,120) (16,994) Property and equipment, net $ 32,041 $ 34,927 Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consist of the following: June 30, 2023 December 31, 2022 (In thousands) Accrued nonclinical, clinical and process development costs $ 8,213 $ 6,854 Employee compensation 6,791 8,710 Accrued professional services 631 532 State income tax payable 71 254 Other 1,998 417 Total accrued expenses and other current liabilities $ 17,704 $ 16,767

Equity Incentive Awards

Equity Incentive Awards	6 Months Ended
	Jun. 30, 2023
Share-Based Payment Arrangement [Abstract]
Equity Incentive Awards	Equity Incentive Awards Stock Options The following table summarizes the Company’s option activity and related information: Number of Weighted- Balance at December 31, 2022 19,320 $ 5.79 Options granted 4,736 0.81 Options exercised — — Options forfeited (541) 5.13 Balance at June 30, 2023 23,515 $ 4.80 Exercisable as of June 30, 2023 8,867 $ 8.82 Restricted Stock Units (“RSUs”) The following table summarizes the Company’s RSUs activity and related information: Number of Units Weighted- Outstanding at December 31, 2022 1,693 $ 2.90 Granted 534 0.76 Vested and released (458) 3.25 Forfeited (44) 3.14 Outstanding at June 30, 2023 1,725 $ 2.14 Stock-Based Compensation Expense The following table presents, by operating expense, the Company’s stock-based compensation expense: Three Months Ended Six Months Ended 2023 2022 2023 2022 (In thousands) Research and development $ 1,380 $ 1,830 $ 2,761 $ 3,763 General and administrative 3,089 3,112 6,271 6,560 Total stock-based compensation expense $ 4,469 $ 4,942 $ 9,032 $ 10,323

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2023
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period. Diluted net loss per share is computed by giving effect to all potential dilutive common stock equivalents outstanding for the period using the treasury stock method. Outstanding stock options, RSUs, rights under the employee stock purchase plan (“ESPP”) and warrants are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. The following common stock equivalents outstanding at the end of the periods presented were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect: June 30, 2023 June 30, 2022 (In thousands) Stock options 23,515 16,798 Restricted stock units 1,726 2,387 ESPP 249 303 25,490 19,488

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation — The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and follow the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, which are necessary for a fair statement of the Company’s consolidated financial information. The results of operations for the three and six months ended June 30, 2023 are not necessarily indicative of the results to be expected for the full year or any other future period. The balance sheet as of December 31, 2022 is derived from the audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete consolidated financial statements.
Use of Estimates	Use of Estimates The accompanying condensed consolidated financial statements have been prepared in accordance with U.S. GAAP. The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities and the reported amounts of expenses in the condensed consolidated financial statements and the accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to clinical trial accruals, fair value of assets and liabilities, impairment of long-lived assets, income taxes, and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Accrued Interest Receivable	Accrued Interest Receivable Accrued interest receivable related to the Company’s available-for-sale debt securities is presented within prepaid expenses and other current assets on the Company’s condensed consolidated balance sheets. The Company has elected to exclude accrued interest receivable from both the fair value and the amortized cost basis of available-for-sale debt securities for the purposes of identifying and measuring any impairment. The Company writes off accrued interest receivable once it has determined that the asset is not realizable. Any write offs of accrued interest receivable are recorded by reversing interest income, recognizing credit loss expense, or a combination of both. To date, the Company has not written off any accrued interest receivables associated with its available-for-sale debt securities.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments – Credit Losses: Measurement of Credit Losses on Financial Instruments (“ Topic 326 ”) and also issued subsequent amendments to the initial guidance: ASU 2018-19, ASU 2019-04, ASU 2019-05, and ASU 2019-11. The standard requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts that affect collectability. Topic 326 also eliminates the concept of “other-than-temporary” impairment when evaluating available-for-sale debt securities and instead focuses on determining whether any impairment is a result of a credit loss or other factors. An entity will recognize an allowance for credit losses on available-for-sale debt securities rather than an other-than-temporary impairment that reduces the cost basis of the investment. The Company adopted ASU 2016-13 on January 1, 2023, using the modified retrospective approach. The adoption of ASU 2016-13 had no significant impact on the Company’s condensed consolidated financial statements.

Fair Value Measurements and F_2

Fair Value Measurements and Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2023
Fair Value Disclosures [Abstract]
Schedule of Cash Equivalents and Short-term Investments	The following is a summary of the Company’s cash equivalents and short-term investments: June 30, 2023 Amortized Cost Basis Unrealized Gains Unrealized Estimated Fair Value (In thousands) Level 1: Money market funds $ 10,541 $ — $ — $ 10,541 Level 2: Commercial paper 101,677 — (27) 101,650 U.S. government and agency securities 24,418 2 (143) 24,277 Total cash equivalents and short-term investments 136,636 2 (170) 136,468 Less: cash equivalents (106,218) (2) 18 (106,202) Total short-term investments $ 30,418 $ — $ (152) $ 30,266 December 31, 2022 Amortized Cost Basis Unrealized Gains Unrealized Estimated Fair Value (In thousands) Level 1: Money market funds $ 10,235 $ — $ — $ 10,235 Level 2: Commercial paper 102,722 — (246) 102,476 U.S. government and agency securities 59,487 — (824) 58,663 Corporate bonds 2,059 — (35) 2,024 Total cash equivalents and short-term investments 174,503 — (1,105) 173,398 Less: cash equivalents (56,256) — 16 (56,240) Total short-term investments $ 118,247 $ — $ (1,089) $ 117,158

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2023
Leases [Abstract]
Schedule of Undiscounted Future Lease Payments under Operating Lease	As of June 30, 2023, undiscounted future non-cancellable lease payments under the lease agreements are as follows (in thousands): Year ending December 31, Operating Leases Sublease Payments Receivable 2023 (remaining six months) $ 20,915 $ 2,573 2024 11,086 5,248 2025 11,448 5,405 2026 11,821 5,567 2027 12,207 5,735 Thereafter 94,653 66,416 Total undiscounted lease payments $ 162,130 $ 90,944 Less: Present value adjustments $ (70,978) Total lease liability $ 91,152
Schedule of Undiscounted Future Sublease Payments Receivable under Operating Lease	As of June 30, 2023, undiscounted future non-cancellable lease payments under the lease agreements are as follows (in thousands): Year ending December 31, Operating Leases Sublease Payments Receivable 2023 (remaining six months) $ 20,915 $ 2,573 2024 11,086 5,248 2025 11,448 5,405 2026 11,821 5,567 2027 12,207 5,735 Thereafter 94,653 66,416 Total undiscounted lease payments $ 162,130 $ 90,944 Less: Present value adjustments $ (70,978) Total lease liability $ 91,152

Balance Sheet Components (Table

Balance Sheet Components (Tables)	6 Months Ended
	Jun. 30, 2023
Balance Sheet Related Disclosures [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consists of the following: June 30, 2023 December 31, 2022 (In thousands) Leasehold improvements $ 34,376 $ 34,336 Laboratory equipment 14,419 14,382 Computer equipment and software 1,325 1,325 Furniture and fixtures 868 868 Construction in progress 1,173 1,010 Total property and equipment 52,161 51,921 Less accumulated depreciation and amortization (20,120) (16,994) Property and equipment, net $ 32,041 $ 34,927
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following: June 30, 2023 December 31, 2022 (In thousands) Accrued nonclinical, clinical and process development costs $ 8,213 $ 6,854 Employee compensation 6,791 8,710 Accrued professional services 631 532 State income tax payable 71 254 Other 1,998 417 Total accrued expenses and other current liabilities $ 17,704 $ 16,767

Equity Incentive Awards (Tables

Equity Incentive Awards (Tables)	6 Months Ended
	Jun. 30, 2023
Share-Based Payment Arrangement [Abstract]
Schedule of Stock Options Activity	The following table summarizes the Company’s option activity and related information: Number of Weighted- Balance at December 31, 2022 19,320 $ 5.79 Options granted 4,736 0.81 Options exercised — — Options forfeited (541) 5.13 Balance at June 30, 2023 23,515 $ 4.80 Exercisable as of June 30, 2023 8,867 $ 8.82
Schedule of Restricted Stock Units Activity	The following table summarizes the Company’s RSUs activity and related information: Number of Units Weighted- Outstanding at December 31, 2022 1,693 $ 2.90 Granted 534 0.76 Vested and released (458) 3.25 Forfeited (44) 3.14 Outstanding at June 30, 2023 1,725 $ 2.14
Schedule of Stock-Based Compensation Expense	The following table presents, by operating expense, the Company’s stock-based compensation expense: Three Months Ended Six Months Ended 2023 2022 2023 2022 (In thousands) Research and development $ 1,380 $ 1,830 $ 2,761 $ 3,763 General and administrative 3,089 3,112 6,271 6,560 Total stock-based compensation expense $ 4,469 $ 4,942 $ 9,032 $ 10,323

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2023
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following common stock equivalents outstanding at the end of the periods presented were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect: June 30, 2023 June 30, 2022 (In thousands) Stock options 23,515 16,798 Restricted stock units 1,726 2,387 ESPP 249 303 25,490 19,488

Organization and Basis of Pre_2

Organization and Basis of Presentation (Detail) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ 863,178	$ 802,612
Cash, cash equivalents, and short-term investments	$ 141,500

Fair Value Measurements and F_3

Fair Value Measurements and Fair Value of Financial Instruments - Summary of Cash Equivalents and Short-term Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	$ 30,418	$ 118,247
Unrealized Gains	0	0
Unrealized Losses	(152)	(1,089)
Estimated Fair Value	30,266	117,158
Less: cash equivalents, amortized cost basis	(106,218)	(56,256)
Less: cash equivalents, unrealized gains	(2)	0
Less: cash equivalents, unrealized losses	18	16
Less: cash equivalents, estimated fair value	(106,202)	(56,240)
Money market funds | Level 1:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	10,541	10,235
Unrealized Gains	0	0
Unrealized Losses	0	0
Estimated Fair Value	10,541	10,235
Commercial paper | Level 2:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	101,677	102,722
Unrealized Gains	0	0
Unrealized Losses	(27)	(246)
Estimated Fair Value	101,650	102,476
U.S. government and agency securities | Level 2:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	24,418	59,487
Unrealized Gains	2	0
Unrealized Losses	(143)	(824)
Estimated Fair Value	24,277	58,663
Corporate bonds | Level 2:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis		2,059
Unrealized Gains		0
Unrealized Losses		(35)
Estimated Fair Value		2,024
Total cash equivalents and short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	136,636	174,503
Unrealized Gains	2	0
Unrealized Losses	(170)	(1,105)
Estimated Fair Value	$ 136,468	$ 173,398

Fair Value Measurements and F_4

Fair Value Measurements and Fair Value of Financial Instruments - Additional Information (Details) $ in Millions	Jun. 30, 2023 USD ($) security	Dec. 31, 2022 USD ($)
Fair Value Disclosures [Abstract]
Marketable securities in an unrealized loss | $	$ 116	$ 155.5
Number of securities, unrealized loss position | security	27

License Revenue (Detail)

License Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
License revenue	$ 0	$ 0	$ 3,600	$ 0
Lexeo Therapeutics, Inc
Disaggregation of Revenue [Line Items]
License revenue			$ 3,500

Leases (Detail)

Leases (Detail) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2023 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) contract	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Lessee, Lease, Description [Line Items]
Restricted cash		$ 2,650	$ 2,503	$ 2,650	$ 2,503	$ 2,503
Reduction in lease liability	$ 8,300
Estimated value of non-cash consideration	$ 14,900
Sublease income		1,400	$ 1,700	2,800	$ 3,400
Building
Lessee, Lease, Description [Line Items]
Restricted cash		$ 2,500		$ 2,500
Manufacturing Facility
Lessee, Lease, Description [Line Items]
Number of renewal contracts | contract				2
Lease renewal term		5 years		5 years

Leases - Schedule of Undiscount

Leases - Schedule of Undiscounted Future Lease Payments under Operating Lease (Detail) $ in Thousands	Jun. 30, 2023 USD ($)
Operating Leases
2023 (remaining six months)	$ 20,915
2024	11,086
2025	11,448
2026	11,821
2027	12,207
Thereafter	94,653
Total undiscounted lease payments	162,130
Less: Present value adjustments	(70,978)
Total lease liability	91,152
Sublease Payments Receivable
2023 (remaining six months)	2,573
2024	5,248
2025	5,405
2026	5,567
2027	5,735
Thereafter	66,416
Total undiscounted lease payments	$ 90,944

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 52,161	$ 51,921
Less accumulated depreciation and amortization	(20,120)	(16,994)
Property and equipment, net	32,041	34,927
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	34,376	34,336
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	14,419	14,382
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property and equipment	1,325	1,325
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	868	868
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 1,173	$ 1,010

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Accrued nonclinical, clinical and process development costs	$ 8,213	$ 6,854
Employee compensation	6,791	8,710
Accrued professional services	631	532
State income tax payable	71	254
Other	1,998	417
Total accrued expenses and other current liabilities	$ 17,704	$ 16,767

Equity Incentive Awards - Summa

Equity Incentive Awards - Summary of Stock Options Activity (Details) shares in Thousands	6 Months Ended
	Jun. 30, 2023 $ / shares shares
Number of Options (in thousands)
Beginning balance (in shares) | shares	19,320
Options granted (in shares) | shares	4,736
Options exercised (in shares) | shares	0
Options forfeited (in shares) | shares	(541)
Ending balance (in shares) | shares	23,515
Exercisable (in shares) | shares	8,867
Weighted- Average Grant- Date Fair Value
Beginning balance (in USD per share) | $ / shares	$ 5.79
Options granted (in USD per share) | $ / shares	0.81
Options exercised (in USD per share) | $ / shares	0
Options forfeited (in USD per share) | $ / shares	5.13
Ending balance (in USD per share) | $ / shares	4.80
Exercisable (in USD per share) | $ / shares	$ 8.82

Equity Incentive Awards - Sum_2

Equity Incentive Awards - Summary of Restricted Stock Units Activity (Details) - Restricted stock units shares in Thousands	6 Months Ended
	Jun. 30, 2023 $ / shares shares
Number of Units (in thousands)
Beginning balance (in shares) | shares	1,693
Granted (in shares) | shares	534
Vested and released (in shares) | shares	(458)
Forfeited (in shares) | shares	(44)
Ending balance (in shares) | shares	1,725
Weighted- Average Grant- Date Fair Value
Beginning balance (in USD per share) | $ / shares	$ 2.90
Granted (in USD per share) | $ / shares	0.76
Vested and released (in USD per share) | $ / shares	3.25
Forfeited (in USD per share) | $ / shares	3.14
Ending balance (in USD per share) | $ / shares	$ 2.14

Equity Incentive Awards - Sum_3

Equity Incentive Awards - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 4,469	$ 4,942	$ 9,032	$ 10,323
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	1,380	1,830	2,761	3,763
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 3,089	$ 3,112	$ 6,271	$ 6,560

Net Loss per Share - Schedule o

Net Loss per Share - Schedule of Common Stock Equivalents Outstanding (Details) - shares shares in Thousands	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (in shares)	25,490	19,488
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (in shares)	23,515	16,798
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (in shares)	1,726	2,387
ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (in shares)	249	303