0001558370-23-012931 | 10-Q | XBRL Viewer

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Property and equipment, net - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 39,110	$ 36,753
Less: Accumulated depreciation and amortization	(17,142)	(14,538)
Property and equipment, net	21,968	22,215
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	13,938	13,619
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,335	1,189
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,236	1,146
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	20,848	20,786
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,753	$ 13

Equity	6 Months Ended
Jun. 30, 2023
Equity
Equity	7. Equity As of June 30, 2023, our amended and restated certificate of incorporation authorizes us to issue 150,000,000 shares of common stock, par value $0.0001 per share, and 5,000,000 shares of preferred stock, par value $0.0001 per share, all of which preferred stock is undesignated. In August 2021, we entered into an “at-the-market” sales agreement pursuant to which we may, from time to time, sell shares of our common stock having an aggregate offering price of up to $250.0 million. As of August 2, 2023, the issuance date of these condensed consolidated financial statements, we have issued and sold 1,795,524 shares of our common stock pursuant to this sales agreement resulting in net proceeds of $12.3 million. In March 2023, in connection with the Share Purchase Agreement with Moderna, we issued and sold 5,859,375 shares of our common stock to Moderna at a price of $6.14 per share for an aggregate purchase price of $36.0 million. For additional information, refer to Note 4, Collaboration and License Agreements. Each share of common stock entitles the holder to one vote on all matters submitted to a vote of our stockholders. Holders of common stock are not entitled to receive dividends, unless declared by the board of directors.

Equity

6 Months Ended

Jun. 30, 2023

Equity

Equity

7. Equity

As of June 30, 2023, our amended and restated certificate of incorporation authorizes us to issue 150,000,000 shares of common stock, par value $0.0001 per share, and 5,000,000 shares of preferred stock, par value $0.0001 per share, all of which preferred stock is undesignated.

In August 2021, we entered into an “at-the-market” sales agreement pursuant to which we may, from time to time, sell shares of our common stock having an aggregate offering price of up to $250.0 million. As of August 2, 2023, the issuance date of these condensed consolidated financial statements, we have issued and sold 1,795,524 shares of our common stock pursuant to this sales agreement resulting in net proceeds of $12.3 million.

In March 2023, in connection with the Share Purchase Agreement with Moderna, we issued and sold 5,859,375 shares of our common stock to Moderna at a price of $6.14 per share for an aggregate purchase price of $36.0 million. For additional information, refer to Note 4, Collaboration and License Agreements.

Each share of common stock entitles the holder to one vote on all matters submitted to a vote of our stockholders. Holders of common stock are not entitled to receive dividends, unless declared by the board of directors.

- Definition

The entire disclosure for equity.

+ References

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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

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	$ (63,160)	$ (72,928)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	12,289	12,757
Depreciation and amortization expense	2,645	2,420
Amortization (accretion) of premium (discount) on marketable securities, net	(4,200)	(240)
Loss on sale of property and equipment	24	28
Loss on impairment of property and equipment	0	5,037
Changes in operating assets and liabilities:
Tenant receivable	55	(1,778)
Prepaid expenses and other current assets	1,390	(3,097)
Operating lease right-of-use assets	3,375	2,185
Other noncurrent assets	1,366	(3,466)
Accounts payable	1,572	(936)
Accrued expenses and other current liabilities	(3,772)	(2,179)
Deferred revenue	46,620	0
Operating lease liability	(1,075)	3,229
Net cash used in operating activities	(2,871)	(58,968)
Cash flows from investing activities:
Purchases of property and equipment	(2,207)	(7,468)
Purchases of marketable securities	(166,994)	(154,037)
Maturities of marketable securities	188,000	0
Net cash provided by (used in) investing activities	18,799	(161,505)
Cash flows from financing activities:
Payment of share issuance costs	(179)	(50)
Proceeds from exercise of stock options and other types of equity, net	367	917
Tax withholding payments related to net share settlements of restricted stock units	(317)	0
Net cash provided by financing activities	35,871	3,593
Net increase (decrease) in cash, cash equivalents and restricted cash	51,799	(216,880)
Cash, cash equivalents and restricted cash at beginning of period	98,863	380,837
Cash, cash equivalents and restricted cash at end of period	150,662	163,957
Supplemental disclosure of noncash investing and financing information:
Purchases of property and equipment included in accounts payable and accrued expenses	240	544
Unrealized gains (losses) on marketable securities	60	(339)
ModernaTX, Inc
Cash flows from financing activities:
Proceeds from issuance/sale of common stock	36,000	0
ATM Offering
Cash flows from financing activities:
Proceeds from issuance/sale of common stock	$ 0	$ 2,726

Property and equipment, net - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Property and equipment, net
Depreciation and amortization expense	$ 1,300	$ 1,200	$ 2,645	$ 2,420

Commitments and Contingencies - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2023
Commitments and Contingencies.
Defined contribution plan, percentage	4.00%

Commitments and Contingencies

6 Months Ended

Jun. 30, 2023

Commitments and Contingencies.

Commitments and Contingencies

9. Commitments and Contingencies

401(k) Plan

We have a defined-contribution plan under Section 401(k) of the Internal Revenue Code of 1986, as amended, or the 401(k) Plan. The 401(k) Plan covers all employees who meet defined minimum age and service requirements and allows participants to contribute a portion of their annual compensation on a pre-tax and/or after-tax basis. In September 2020, we adopted a match program, beginning on January 1, 2021, for employee contributions to the 401(k) Plan up to a maximum of four percent of the employee’s salary, subject to the maximums established under the U.S. Internal Revenue Code of 1986, as amended.

Indemnification agreements

In the ordinary course of business, we may provide indemnification of varying scope and terms to vendors, lessors, contract research organizations, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, we have entered into indemnification agreements with members of our board of directors and our officers that will require us, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments we could be required to make under

these indemnification agreements is, in many cases, unlimited. We have not incurred any material costs as a result of such indemnifications and are not currently aware of any indemnification claims.

Legal proceedings

We, from time to time, may be party to litigation arising in the ordinary course of business. We were not subject to any material legal proceedings during the six months ended June 30, 2023.

Property and equipment, net (Tables)

6 Months Ended

Jun. 30, 2023

Property and equipment, net.

Summary of Property and equipment, net

Property and equipment, net consisted of the following:


	June 30,		December 31,
(in thousands)	2023		2022
Laboratory equipment	$	13,938	$	13,619
Computer equipment and software		1,335		1,189
Furniture and fixtures		1,236		1,146
Leasehold improvements		20,848		20,786
Construction in progress		1,753		13
		39,110		36,753
Less: Accumulated depreciation and amortization		(17,142)		(14,538)
Total	$	21,968	$	22,215

Collaboration and License Agreement

6 Months Ended

Jun. 30, 2023

Collaboration and License Agreement

Collaboration and License Agreement

4. Collaboration and License Agreement

Moderna Collaboration and License Agreement

In March 2023, we entered into a Collaboration and License Agreement, or the Collaboration Agreement, with Moderna to collaborate on developing treatments for certain diseases by targeting delivery of nucleic acids to liver cells and certain cells outside of the liver.

Under the Collaboration Agreement, the parties have agreed to collaborate on preclinical research programs relating to lipid nanoparticle, or LNP, delivery systems and nucleic acid payloads, with each party obtaining certain rights to intellectual property used in and arising out of such research programs. Each party will be solely responsible for its own clinical development and commercialization of products under the Collaboration Agreement. Moderna will reimburse us for the internal and external costs incurred by us in conducting the research programs, to the extent consistent with such research plans and budgets.

Moderna has exclusive options, upon payment of option exercise fees, to obtain worldwide, exclusive, sublicensable licenses under specified company intellectual property to develop, manufacture and commercialize (a) products comprising LNP delivery systems and nucleic acid payloads that are directed to (i) up to two liver targets, (ii) up to two non-liver targets and (iii) a third liver or non-liver target and (b) Exclusive Targets, which are Independent Program Products (as defined below) that include messenger RNA, or mRNA, that are directed to gene and protein targets in any of certain agreed-upon immune cell types, referred to as the Cell Target Types. Subject to the our exclusivity obligations described below, each party has granted to the other a worldwide, non-exclusive, sublicensable license under certain LNP-related intellectual property arising out of the non-liver ctLNP program, or the Joint Collaboration ctLNP Intellectual Property, to develop, manufacture and commercialize products comprising LNP delivery systems and nucleic acid payloads directed to gene and protein targets in any of the Cell Target Types, or Independent Program Products.

Each party is obligated to use commercially reasonable efforts to complete the activities assigned to it under the research plans, and Moderna is further obligated to use commercially reasonable efforts to develop, seek regulatory approval for and commercialize at least one product directed to each target for which Moderna exercises its exclusive license option in at least one indication in the United States and in specified European countries.

We have agreed not to, directly or indirectly, alone or with, for or through any third party, develop, manufacture, commercialize or exploit (a) products containing mRNA that are directed to any of the Cell Target Types, during an agreed-upon exclusivity period, which may be extended by payment of extension fees, (b) products directed to any liver target or non-liver target during the option periods for those targets, (c) products directed to any liver target or non-liver target for which Moderna has exercised its exclusive license option or (d) products containing mRNA that are directed to any Exclusive Target for which Moderna has exercised its exclusive license option.

Under the terms of the Collaboration Agreement, in April 2023, Moderna made an upfront payment to us of $40.0 million, and paid us $7.5 million in prepaid research funding. In addition, we are eligible to receive up to $1.8 billion in milestone payments upon the achievement of specified development, regulatory, commercial, and sales milestone events, research term extension fees and exclusivity extension fees. Subject to reductions in specified circumstances, we will also be entitled to receive tiered royalties: (i) ranging from high-single-digits to low-double-digits on sales of licensed products that are directed to any liver target or non-liver target with respect to which Moderna has exercised its exclusive license option, and (ii) in the single digits on sales of Independent Program Products, including the exclusively licensed Independent Program Products directed to the Exclusive Targets. In consideration for the non-exclusive license granted by Moderna to us under the Joint Collaboration ctLNP Intellectual Property, we have agreed to pay Moderna tiered royalties in the single digits on sales of Independent Program Products that include mRNA, subject to reductions in specified circumstances. Royalties will be paid by each party, on a licensed product-by-licensed product and country-by-country basis, until the latest to occur of: (i) expiration of the last-to-expire of specified licensed patent rights; (ii) expiration of regulatory exclusivity; or (iii) ten years after the first commercial sale of the applicable licensed product.

In addition, in connection with the execution of the Collaboration Agreement, we entered into a Share Purchase Agreement, or the Share Purchase Agreement, with Moderna, pursuant to which we issued and sold 5,859,375 shares of our common stock to Moderna, at a price of $6.14 per share, for an aggregate purchase price of $36.0 million, which closed concurrently with the execution of the Collaboration Agreement. Under the Share Purchase Agreement, Moderna has the right, subject to certain terms and conditions, to purchase up to 3.06% of the outstanding shares of our common stock (on a post-closing basis) in connection with a future equity financing of at least $25.0 million by us.

Moderna Agreement Assessment

We assessed the promised goods and services under the Collaboration Agreement, in accordance with ASC Topic 606, “Revenue from Contracts with Customers”, or ASC 606. At inception, the Collaboration Agreement included one combined performance obligation, which includes the license to the ctLNP technology to target indications outside of the liver and the related research services to develop such technology, as the two items are not distinct in context of the contract. The Collaboration Agreement also provides Moderna with options to receive additional research services and options to receive exclusive licenses. The options to receive exclusive licenses allow Moderna to develop and commercialize product candidates that utilize our ctLNP and ceDNA technology for targets within the liver, as well as utilizing the ctLNP technology to be developed as part of the Collaboration Agreement and our ceDNA technology for targets outside the liver. These options are considered to be a priced at a discount to its standalone selling price and therefore are considered to be material rights.

The initial transaction price included a $40.0 million upfront fee, premium paid over the fair value of the common stock of $13.3 million in connection with shares issued and sold to Moderna under the Share Purchase Agreement, and estimated revenue associated with the payment for research services, including $7.5 million in prepaid research services. We utilized the expected amount method to determine the amount of reimbursement for these activities. We utilized the most likely amount method to determine the amount of consideration to include in the transaction price related to any variable consideration related to exclusivity fees, and milestones, and the royalty payments are constrained based on the royalty constraint. No amounts are included in the transaction price related to these elements.

We allocated the transaction price to each unit of account as follows:


Performance Obligations (in thousands)	Standalone Selling Price		Transaction Price Allocated
ctLNP technology and research license	$	52,500	$	42,576
First liver program commercialization option license		7,000		5,677
Second liver program commercialization option license		7,000		5,677
First non-liver program commercialization option license		11,700		9,488
Second non-liver program commercialization option license		11,700		9,488
Third liver or non-liver program commercialization option license		6,150		4,987
Total	$	96,050	$	77,893

The transaction price was allocated to each unit of account based on the relative estimated standalone selling prices, over which management has applied significant judgment, of each element. We developed the estimated standalone selling price for combined performance obligation and each of the options to receive licenses primarily based on the probability-weighted present value of expected future cash flows associated with each license related to each specific program and an estimate of the costs to provide services including a reasonable return. In developing such estimate, we also considered applicable market conditions and relevant entity-specific factors, including those factors contemplated in negotiating the agreement, the probability of success and the time needed to commercialize a product candidate pursuant to the associated license.

We measure proportional performance of the combined performance obligation over time using an input method based on cost incurred relative to the total estimated costs on a quarterly basis by determining the proportion of effort incurred as a percentage of total effort we expect to expend. Any changes to these estimates will be recognized in the period in which they change as a cumulative catch up. All allocated consideration for the material rights is deferred until such time that Moderna exercises its options or the right to exercise the options expires. Upon exercise, we will determine the appropriate revenue recognition methodology and any other implications on the accounting treatment for the arrangement.

The following table provides a summary of the transaction price allocated to each unit of account, in addition to revenue activity during the period:


Performance Obligations	Transaction Price Allocated		Revenue Recognized During		Deferred Revenue
(in thousands)	As of June 30, 2023		Three and Six Months Ended June 30, 2023		As of June 30, 2023
ctLNP technology and research license	$	42,576	$	880	$	32,334
First liver program commercialization option license		5,677		—		4,429
Second liver program commercialization option license		5,677		—		4,429
First non-liver program commercialization option license		9,488		—		7,401
Second non-liver program commercialization option license		9,488		—		7,401
Third liver or non-liver program commercialization option license		4,987		—		3,891
Total	$	77,893	$	880	$	59,885

Marketable Securities and Fair Value Measurements

6 Months Ended

Jun. 30, 2023

Marketable Securities and Fair Value Measurements

Marketable Securities and Fair Value Measurements

3. Marketable Securities and Fair Value Measurements

The following tables present our marketable securities by security type:

As of June 30, 2023

Gross

Amortized

Unrealized

Fair

(in thousands)

Cost

Gains

Losses

Value

U.S. treasury securities

169,196

(35)

169,173

As of December 31, 2022

Gross

Amortized

Unrealized

Fair

(in thousands)

Cost

Gains

Losses

Value

U.S. treasury securities

186,003

(96)

185,920

As of June 30, 2023 and December 31, 2022, our marketable securities consisted of investments that mature within one year of their purchase date.

The following tables present our assets that are measured at fair value on a recurring basis and indicate the level within the fair value hierarchy of the valuation techniques that we utilized to determine such fair value:


	Fair Value Measurements at June 30, 2023 Using:
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	49,610	$	—	$	—	$	49,610
U.S. treasury securities		12,943		—		—		12,943
Marketable securities:
U.S. treasury securities		—		169,173		—		169,173
Totals	$	62,553	$	169,173	$	—	$	231,726


	Fair Value Measurements at December 31, 2022 Using:
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	77,010	$	—	$	—	$	77,010
Marketable securities:
U.S. treasury securities		—		185,920		—		185,920
Totals	$	77,010	$	185,920	$	—	$	262,930

- Definition

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

+ References + Details

Collaboration and License Agreement (Details) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended
	Mar. 31, 2023 USD ($) item product $ / shares shares	Aug. 31, 2021 shares	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Apr. 30, 2023 USD ($)
Collaboration and License Agreement
Issuance/Sale of common stock, shares \| shares		1,795,524
Revenue recognized			$ 880	$ 0	$ 880	$ 0
Share Purchase Agreement \| Beneficial Owner [Member] \| ModernaTX, Inc
Collaboration and License Agreement
Issuance/Sale of common stock, shares \| shares	5,859,375
Collaboration and License Agreement \| ModernaTX, Inc
Collaboration and License Agreement
Upfront payments	$ 40,000						$ 40,000
Prepaid research services funding	$ 7,500						$ 7,500
Milestone payments receivable			$ 1,800,000		$ 1,800,000
Number of performance obligations \| item	1
Premium paid on common stock	$ 13,300
Variable consideration	$ 0
Collaboration and License Agreement \| ModernaTX, Inc \| Minimum
Collaboration and License Agreement
Number of products to be commercialized \| product	1
Royalty payment term	10 years
Collaboration and License Agreement \| Share Purchase Agreement \| Beneficial Owner [Member] \| ModernaTX, Inc
Collaboration and License Agreement
Issuance/Sale of common stock, shares \| shares	5,859,375
Shares issue price (in dollars per share) \| $ / shares	$ 6.14
Proceeds from issuance/sale of common stock	$ 36,000
Percent of shares to be issued	3.06%
Equity financing	$ 25,000

Nature of the Business and Basis of Presentation

6 Months Ended

Jun. 30, 2023

Accounting Policies [Abstract]

Nature of the Business and Basis of Presentation

1. Nature of the Business and Basis of Presentation

Generation Bio Co., or Generation Bio, was incorporated on October 21, 2016 as Torus Therapeutics, Inc. and subsequently changed its name to Generation Bio Co. Generation Bio Co. and its consolidated subsidiary, or the company, we, our or us, are innovating genetic medicines to provide durable, redosable treatments for potentially hundreds of millions of patients living with rare and prevalent diseases. Our non-viral genetic medicines platform incorporates our high-capacity DNA construct called closed-ended DNA, or ceDNA; our cell-targeted lipid nanoparticle delivery system, or ctLNP; and our highly scalable capsid-free manufacturing process that uses our proprietary cell-free rapid enzymatic synthesis, or RES, to produce ceDNA. Using our approach, we are developing novel genetic medicines to provide targeted delivery of genetic payloads that include large and multiple genes to a range of cell types across a broad array of diseases. We are also engineering our genetic medicines to be redosable, which may enable individualized patient titration to reach the desired therapeutic expression and to maintain efficacy throughout a patient’s life. We are headquartered in Cambridge, Massachusetts.

We are subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, the ability to establish clinical- and commercial-scale manufacturing processes and the ability to secure additional capital to fund operations. Programs currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization of a product. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if our development efforts are successful, it is uncertain when, if ever, we will realize significant revenue from product sales.

The accompanying condensed consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. Since inception, we have funded our operations with proceeds from the sale of instruments convertible into convertible preferred stock (which converted into convertible preferred stock in 2017), sales of convertible preferred stock (which converted into common stock in 2020), and sales of common stock in underwritten public offerings, “at-the-market” offerings, and in a private placement, as well as payments pursuant to our collaboration with ModernaTX, Inc., or Moderna. We have incurred recurring losses, including net losses of $63.2 million for the six months ended June 30, 2023 and $72.9 million for the six months ended June 30, 2022. As of June 30, 2023, we had an accumulated deficit of $508.0 million. We expect to continue to generate operating losses in the foreseeable future. As of August 2, 2023, the issuance date of these condensed consolidated financial statements, we expect that our cash, cash equivalents and marketable securities will be sufficient to fund our operating expenses and capital expenditure requirements for at least 12 months.

We will need to obtain additional funding through public or private equity offerings, debt financings, collaborations, strategic alliances and/or licensing arrangements. We may not be able to obtain financing on acceptable terms, or at all, and we may not be able to enter into additional collaborative or strategic alliances or licensing arrangements. The terms of any financing may adversely affect the holdings or the rights of our stockholders. Arrangements with collaborators or others may require us to relinquish rights to certain of our technologies or programs. If we are unable to obtain funding, we could be forced to delay, reduce or eliminate some or all of our research and development programs, pipeline expansion or commercialization efforts, which could adversely affect our business prospects. Although management will continue to pursue these plans, there is no assurance that we will be successful in obtaining sufficient funding on terms acceptable to us to fund continuing operations when needed or at all.

The accompanying condensed consolidated financial statements reflect the operations of Generation Bio and our wholly owned subsidiary, Generation Bio Securities Corporation. Intercompany balances and transactions have been eliminated in consolidation. The accompanying condensed consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States of America, or GAAP. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification, or ASC, and Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB.

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2022
Statement of Stockholders' Equity [Abstract]
Stock issuance of costs	$ 89	$ 89

Related Parties

6 Months Ended

Jun. 30, 2023

Related Parties

Related Parties

11. Related Parties

In March 2023, we entered into the Collaboration Agreement with Moderna. In connection with the Share Purchase Agreement, we issued and sold 5,859,375 shares of our common stock to Moderna, which resulted in Moderna becoming the beneficial owner of 8.9% of our outstanding common stock and a related party.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

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+ Details

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Pay vs Performance Disclosure
Net Income (Loss)	$ (31,066)	$ (37,929)	$ (63,160)	$ (72,928)

- Definition

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

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+ Details

Accrued Expenses (Tables)

6 Months Ended

Jun. 30, 2023

Accrued Expenses

Summary of accrued expenses

Accrued expenses and other current liabilities consisted of the following:


	June 30,		December 31,
(in thousands)	2023		2022
Accrued employee compensation and benefits	$	4,343	$	7,970
Accrued external research and development expenses		2,071		1,959
Accrued professional fees		809		1,047
Property and equipment		122		—
Other		406		426
Total	$	7,751	$	11,402

Property and equipment, net

6 Months Ended

Jun. 30, 2023

Property and equipment, net.

Property and equipment, net

5. Property and equipment, net

Property and equipment, net consisted of the following:


	June 30,		December 31,
(in thousands)	2023		2022
Laboratory equipment	$	13,938	$	13,619
Computer equipment and software		1,335		1,189
Furniture and fixtures		1,236		1,146
Leasehold improvements		20,848		20,786
Construction in progress		1,753		13
		39,110		36,753
Less: Accumulated depreciation and amortization		(17,142)		(14,538)
Total	$	21,968	$	22,215

Depreciation and amortization expense for the three and six months ended June 30, 2023 was $1.3 million and $2.6 million, respectively. Depreciation and amortization expense for the three and six months ended June 30, 2022 was $1.2 million and $2.4 million, respectively.

In July 2021, we entered into a lease agreement to build out a current Good Manufacturing Practice-, or cGMP-, compliant manufacturing facility in Waltham, Massachusetts in order to scale ceDNA manufacturing utilizing RES for clinical and initial commercial supply. We decided to transition from building out the cGMP compliant manufacturing facility to utilizing an external cleanroom facility after achieving increased scalability of the RES development process in the second half of 2022. Consequently, we are seeking one or more third parties to assume our lease or sublease the property. The balance of construction in progress at June 30, 2023, was comprised primarily of the capitalization of construction costs to renovate the property for alternative use.

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Revenues:
Collaboration revenue	$ 880	$ 0	$ 880	$ 0
Operating expenses:
Research and development	21,832	28,365	43,832	53,919
General and administrative	12,967	10,116	25,833	19,906
Total operating expenses	34,799	38,481	69,665	73,825
Loss from operations	(33,919)	(38,481)	(68,785)	(73,825)
Other income:
Other income and interest income, net	2,853	552	5,625	897
Net loss and net loss attributable to common stockholders	$ (31,066)	$ (37,929)	$ (63,160)	$ (72,928)
Net loss per share attributable to common stockholders, basic	$ (0.47)	$ (0.66)	$ (1.00)	$ (1.28)
Net loss per share attributable to common stockholders, diluted	$ (0.47)	$ (0.66)	$ (1.00)	$ (1.28)
Weighted average common shares outstanding, basic	65,656,151	57,149,474	62,957,556	57,107,917
Weighted average common shares outstanding, diluted	65,656,151	57,149,474	62,957,556	57,107,917
Comprehensive loss:
Net loss	$ (31,066)	$ (37,929)	$ (63,160)	$ (72,928)
Other comprehensive loss:
Unrealized gains (losses) on marketable securities	(57)	(339)	60	(339)
Comprehensive loss	$ (31,123)	$ (38,268)	$ (63,100)	$ (73,267)

Insider Trading Arrangements

3 Months Ended

Jun. 30, 2023

Trading Arrangements, by Individual

Material Terms of Trading Arrangement

The following table describes, for the period covered by this Quarterly Report, each trading arrangement for the sale or purchase of Company securities adopted or terminated by our directors and officers that is a contract, instruction or written plan intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) (a “Rule 10b5-1 trading arrangement”). For the period covered by this Quarterly Report, none of our directors or officers adopted or terminated a “non-Rule 10b5-1 trading arrangement” (as defined in Item 408(c) of Regulation S-K).


Name	Title	Action Taken	Date	Shares to be Sold	Expiration Date
Matthew Stanton	Chief Scientific Officer	Adoption	April 14, 2023	20,000	January 13, 2024
Antoinette Paone	Chief Operating Officer	Adoption	April 24, 2023	155,472*	August 30, 2024
Douglas Kerr	Chief Medical Officer	Adoption	April 24, 2023	24,968	October 24, 2024
Phillip Samayoa	Chief Strategy Officer	Adoption	June 29, 2023	100,947*	May 15, 2024

*In addition to the number of shares acquired through our Employee Stock Purchase Program, which number cannot be determined at this time.

Rule 10b5-1 Arrangement Adopted

true

Non-Rule 10b5-1 Arrangement Adopted

true

Rule 10b5-1 Arrangement Terminated

false

Non-Rule 10b5-1 Arrangement Terminated

false

Matthew Stanton

Trading Arrangements, by Individual

Name

Matthew Stanton

Title

Chief Scientific Officer

April 14, 2023

20,000

January 13, 2024

Trading Arrangements, by Individual

Name

Antoinette Paone

Title

Chief Operating Officer

April 24, 2023

155,472

August 30, 2024

Trading Arrangements, by Individual

Name

Douglas Kerr

Title

Chief Medical Officer

April 24, 2023

24,968

October 24, 2024

Trading Arrangements, by Individual

Name

Phillip Samayoa

Title

Chief Strategy Officer

Adoption Date

June 29, 2023

Aggregate Available

100,947

Expiration Date

May 15, 2024

Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2023

Stock-Based Compensation

Summary of stock-based compensation expense was classified in the statements of operations and comprehensive loss


	Three Months Ended June 30,				Six Months Ended June 30,
(in thousands)	2023		2022		2023		2022
Research and development expenses	$	2,879	$	3,476	$	5,734	$	6,628
General and administrative expenses		3,144		3,215		6,555		6,129
Total	$	6,023	$	6,691	$	12,289	$	12,757

Net Loss per Share - Summary of Potential Dilutive Securities, Presented Based on Amounts Outstanding (Detail) - shares	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive net loss per share	11,605,343	10,191,638
Unvested restricted common stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive net loss per share	1,356,667	1,533,821
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive net loss per share	10,248,676	8,657,817

Related Parties (Details) - shares	1 Months Ended
Related Parties (Details) - shares	Mar. 31, 2023	Aug. 31, 2021
Related Party Transaction [Line Items]
Shares issued during the period		1,795,524
Beneficial Owner [Member] \| ModernaTX, Inc [Member] \| Share Purchase Agreement
Related Party Transaction [Line Items]
Shares issued during the period	5,859,375
Beneficial ownership percentage	8.90%

Collaboration and License Agreement - Schedule of Allocated Transaction Price and Revenue Activity (Details) - ModernaTX, Inc $ in Thousands	6 Months Ended
	Jun. 30, 2023 USD ($)
Collaboration and License Agreement
Standalone Selling Price	$ 96,050
Transaction Price Allocated	77,893
Revenue Recognized	880
Revenue Recognized	59,885
ctLNP technology and research license
Collaboration and License Agreement
Standalone Selling Price	52,500
Transaction Price Allocated	42,576
Revenue Recognized	880
Revenue Recognized	32,334
First liver program commercialization option license
Collaboration and License Agreement
Standalone Selling Price	7,000
Transaction Price Allocated	5,677
Revenue Recognized	0
Revenue Recognized	4,429
Second liver program commercialization option license
Collaboration and License Agreement
Standalone Selling Price	7,000
Transaction Price Allocated	5,677
Revenue Recognized	0
Revenue Recognized	4,429
First non-liver program commercialization option license
Collaboration and License Agreement
Standalone Selling Price	11,700
Transaction Price Allocated	9,488
Revenue Recognized	0
Revenue Recognized	7,401
Second non-liver program commercialization option license
Collaboration and License Agreement
Standalone Selling Price	11,700
Transaction Price Allocated	9,488
Revenue Recognized	0
Revenue Recognized	7,401
Third liver or non-liver program commercialization option license
Collaboration and License Agreement
Standalone Selling Price	6,150
Transaction Price Allocated	4,987
Revenue Recognized	0
Revenue Recognized	$ 3,891

Marketable Securities and Fair Value Measurements - Summary of marketable securities (Detail) - Fair Value, Recurring [Member] - U.S. treasury securities - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Marketable Securities [Line Items]
Amortized Cost	$ 169,196	$ 186,003
Gross Unrealized Gains	12	13
Gross Unrealized Losses	(35)	(96)
Fair Value	$ 169,173	$ 185,920

Equity - Additional Information (Detail) $ / shares in Units, $ in Millions	1 Months Ended		6 Months Ended
	Mar. 31, 2023 USD ($) $ / shares shares	Aug. 31, 2021 USD ($) shares	Jun. 30, 2023 security $ / shares shares	Dec. 31, 2022 $ / shares shares
Common stock, shares authorized			150,000,000	150,000,000
Common stock, par value per share \| $ / shares			$ 0.0001	$ 0.0001
Preferred stock, shares authorized			5,000,000	5,000,000
Preferred stock, par value per share \| $ / shares			$ 0.0001	$ 0.0001
Shares issued during the period		1,795,524
Net proceeds from shares issued \| $		$ 12.3
Number of vote per common share \| security			1
Beneficial Owner [Member] \| ModernaTX, Inc \| Share Purchase Agreement
Shares issued during the period	5,859,375
Maximum [Member]
Aggregate gross offering price \| $		$ 250.0
Share Purchase Agreement \| Beneficial Owner [Member] \| ModernaTX, Inc \| Share Purchase Agreement
Shares issued during the period	5,859,375
Shares issue price (in dollars per share) \| $ / shares	$ 6.14
Proceeds from Issuance of Common Stock \| $	$ 36.0

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 144,970	$ 93,171
Marketable securities	169,173	185,920
Tenant receivable	340	395
Prepaid expenses and other current assets	6,140	7,530
Total current assets	320,623	287,016
Property and equipment, net	21,968	22,215
Operating lease right-of-use assets	55,834	59,208
Restricted cash	5,692	5,692
Deferred offering costs	433	434
Other long-term assets	333	1,699
Total assets	404,883	376,264
Current liabilities:
Accounts payable	2,328	662
Accrued expenses and other current liabilities	7,751	11,402
Deferred revenue	8,265	0
Operating lease liability	8,135	7,086
Total current liabilities	26,479	19,150
Deferred revenue, net of current portion	51,620	0
Operating lease liability, net of current portion	72,497	74,621
Total liabilities	150,596	93,771
Commitments and contingencies (Note 9)
Stockholders' equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized and no shares issued or outstanding at June 30, 2023 and December 31, 2022	0	0
Common stock, $0.0001 par value; 150,000,000 shares authorized at June 30, 2023 and December 31, 2022; 65,784,250 and 59,505,437 shares issued and outstanding at June 30, 2023 and December 31, 2022, respectively	7	6
Additional paid-in capital	762,228	727,335
Accumulated other comprehensive loss	(23)	(83)
Accumulated deficit	(507,925)	(444,765)
Total stockholders' equity	254,287	282,493
Total liabilities and stockholders' equity	$ 404,883	$ 376,264

Accrued Expenses

6 Months Ended

Jun. 30, 2023

Accrued Expenses

Accrued Expenses

6. Accrued Expenses

Accrued expenses and other current liabilities consisted of the following:


	June 30,		December 31,
(in thousands)	2023		2022
Accrued employee compensation and benefits	$	4,343	$	7,970
Accrued external research and development expenses		2,071		1,959
Accrued professional fees		809		1,047
Property and equipment		122		—
Other		406		426
Total	$	7,751	$	11,402

Marketable Securities and Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2023

Marketable Securities and Fair Value Measurements

Summary of marketable securities

The following tables present our marketable securities by security type:

As of June 30, 2023

Gross

Amortized

Unrealized

Fair

(in thousands)

Cost

Gains

Losses

Value

U.S. treasury securities

169,196

(35)

169,173

As of December 31, 2022

Gross

Amortized

Unrealized

Fair

(in thousands)

Cost

Gains

Losses

Value

U.S. treasury securities

186,003

(96)

185,920

Summary of assets measured at fair value on a recurring basis


	Fair Value Measurements at June 30, 2023 Using:
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	49,610	$	—	$	—	$	49,610
U.S. treasury securities		12,943		—		—		12,943
Marketable securities:
U.S. treasury securities		—		169,173		—		169,173
Totals	$	62,553	$	169,173	$	—	$	231,726


	Fair Value Measurements at December 31, 2022 Using:
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	77,010	$	—	$	—	$	77,010
Marketable securities:
U.S. treasury securities		—		185,920		—		185,920
Totals	$	77,010	$	185,920	$	—	$	262,930

Marketable Securities and Fair Value Measurements - Summary of assets measured at fair value on a recurring basis (Detail) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Marketable securities:
Total	$ 231,726	$ 262,930
Level 1
Marketable securities:
Total	62,553	77,010
Level 2
Marketable securities:
Total	169,173	185,920
Level 3
Marketable securities:
Total	0	0
Money Market Funds
Cash equivalents:
Cash equivalents	49,610	77,010
Money Market Funds \| Level 1
Cash equivalents:
Cash equivalents	49,610	77,010
Money Market Funds \| Level 2
Cash equivalents:
Cash equivalents	0	0
Money Market Funds \| Level 3
Cash equivalents:
Cash equivalents	0	0
U.S. treasury securities
Cash equivalents:
Cash equivalents	12,943
Marketable securities:
Marketable securities	169,173	185,920
U.S. treasury securities \| Level 1
Cash equivalents:
Cash equivalents	12,943
Marketable securities:
Marketable securities	0	0
U.S. treasury securities \| Level 2
Cash equivalents:
Cash equivalents	0
Marketable securities:
Marketable securities	169,173	185,920
U.S. treasury securities \| Level 3
Cash equivalents:
Cash equivalents	0
Marketable securities:
Marketable securities	$ 0	$ 0

Stock-Based Compensation

6 Months Ended

Jun. 30, 2023

Stock-Based Compensation

Stock-Based compensation

8. Stock-Based Compensation

Stock incentive plans

Our 2017 Stock Incentive Plan, or the 2017 Plan, provided for us to grant incentive stock options or nonstatutory stock options, restricted stock, restricted stock units and other equity awards to employees, non-employees, and directors.

In May 2020, our board of directors adopted, and in June 2020, our stockholders approved, the 2020 Stock Incentive Plan, or the 2020 Plan, and together with the 2017 Plan, the Plans, which became effective on June 11, 2020. The 2020 Plan provides for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. The number of shares of common stock reserved for issuance under the 2020 Plan is the sum of (1) 2,547,698 shares; plus (2) the number of shares (up to a maximum of 7,173,014 shares) as was equal to the sum of (x) the number of shares of common stock reserved for issuance under the 2017 Plan that remained available for grant under the 2017 Plan on June 11, 2020 and (y) the number of shares of common stock subject to outstanding awards granted under the 2017 Plan that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by us at their original issuance price pursuant to a contractual repurchase right; plus (3) an annual increase, to be added on the first day of each fiscal year, beginning with the fiscal year ending December 31, 2021 and continuing until, and including, the fiscal year ending December 31, 2030, equal to the lesser of (i) 4% of the number of shares of common stock outstanding on such date, and (ii) an amount determined by the board of directors. In January 2021, 2022 and 2023, the number of shares of common stock authorized for issuance under the 2020 Plan was increased from 10,275,717 shares to 12,154,517 shares, from 12,154,517 shares to 14,433,745 shares, and from 14,433,745 shares to 16,813,962 shares, respectively. Upon the effectiveness of the 2020 Plan, we ceased granting additional awards under the 2017 Plan.

The Plans are administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of directors. The exercise prices, vesting and other restrictions on any award under the Plans are determined at the discretion of the board of directors, or its committee if so delegated. Stock options granted under the Plans with service-based vesting conditions generally vest over four years and expire after ten years. The exercise price for stock options granted is not less than the fair value of common stock as of the date of grant. Prior to our IPO, fair value of common stock was determined by the board of directors. Subsequent to our IPO, fair value of common stock is based on quoted market prices.

As of June 30, 2023, 883,445 shares remained available for future issuance under the 2020 Plan. Shares subject to outstanding awards granted under the Plans that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by us at their original issuance price pursuant to a contractual repurchase right will be available for future awards under the 2020 Plan. In July 2023, an additional 499,952 shares became available for future issuance under the 2020 Plan as a result of the expiration of performance-based stock options granted in March 2020.

Grant of stock options

During the six months ended June 30, 2023, we granted time-based options to certain employees for the purchase of an aggregate of 1,705,581 shares of common stock with a weighted average grant date fair value of $3.66 per share that vest over a weighted average period of approximately four years.

Restricted stock units

During the six months ended June 30, 2023, we issued 828,920 restricted stock units with a fair value of $3.8 million that vest over a weighted average period of approximately four years.

Employee stock purchase plan

In May 2020, our board of directors adopted, and in June 2020, our stockholders approved, the 2020 Employee Stock Purchase Plan, or the 2020 ESPP, which became effective June 11, 2020. The 2020 ESPP is administered by our board of directors or by a committee appointed by the board of directors. The number of shares of common stock authorized for issuance under the 2020 ESPP automatically increases on the first day of each fiscal year, beginning with the fiscal year that commenced on January 1, 2021 and continuing for each fiscal year until, and including the fiscal year commencing on, January 1, 2030, in an amount equal to the lowest of (1) 1,302,157 shares of common stock, (2) 1% of the number of shares of common stock outstanding on such date, and (3) an amount determined by the board of directors. In January 2021, 2022, and 2023, the number of shares of common stock authorized for issuance under the 2020 ESPP was increased from 481,231 shares to 950,931 shares, from 950,931 shares to 1,520,738 shares, and from 1,520,738 shares to 2,115,792 shares, respectively. As of June 30, 2023, 1,826,149 shares remained available for issuance under the 2020 ESPP.

Stock-based compensation

Stock-based compensation expense was classified in the condensed consolidated statements of operations and comprehensive loss as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
(in thousands)	2023		2022		2023		2022
Research and development expenses	$	2,879	$	3,476	$	5,734	$	6,628
General and administrative expenses		3,144		3,215		6,555		6,129
Total	$	6,023	$	6,691	$	12,289	$	12,757

As of June 30, 2023, total unrecognized compensation cost related to unvested time-based stock options and restricted stock units was $38.1 million, with $32.2 million expected to be recognized over a weighted average period of 2.7 years and $5.9 million expected to be recognized over a weighted average period of 2.3 years, respectively. Additionally, as of June 30, 2023, we had unrecognized compensation cost related to unvested stock options with performance-based vesting conditions for which performance has not been deemed probable of $1.7 million.

Stock-Based Compensation - Summary of Stock-Based Compensation Expense was Classified in the Statements of Operations and Comprehensive Loss (Detail) - 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]
Stock-based compensation expense	$ 6,023	$ 6,691	$ 12,289	$ 12,757
Research and development expense [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	2,879	3,476	5,734	6,628
General and administrative expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 3,144	$ 3,215	$ 6,555	$ 6,129

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2023

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Use of estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses and stock-based compensation expense. We base our estimates on historical experience, known trends and other market-specific or other relevant factors that we believe to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates, as there are changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results may differ from those estimates or assumptions.

Unaudited interim financial information

The condensed consolidated balance sheet as of December 31, 2022 was derived from audited financial statements but does not include all disclosures required by GAAP. The accompanying unaudited financial statements as of June 30, 2023 and for the three and six months ended June 30, 2023 and 2022 have been prepared by us pursuant to the rules and regulations of the Securities and Exchange Commission, or SEC, for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. These financial statements should be read in conjunction with our audited financial statements included in our Annual Report on Form 10-K that was most recently filed with the SEC. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair presentation of our financial position as of June 30, 2023, the results of operations for the three and six months ended June 30, 2023 and 2022, and cash flows for the six months ended June 30, 2023 and 2022 have been made. The results of operations for the three and six months ended June 30, 2023 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2023 or any other period.

Our significant accounting policies are described in Note 2 of the Notes to Consolidated Financial Statements included in our Annual Report on Form 10-K that was most recently filed with the SEC.

Concentrations of credit risk and of significant suppliers

Financial instruments that potentially expose us to concentrations of credit risk consist primarily of cash, cash equivalents, and marketable securities. We believe that we are not exposed to significant credit risk due to the financial strength of the national depository institutions in which our cash, cash equivalents, and marketable securities are held. We maintain our cash equivalents in money market funds that invest in U.S. treasury securities. We have adopted an investment policy that limits the amounts that we may invest in the securities of a single issuer with the exclusion of the U.S. government. We have not experienced any credit losses.

We are dependent on a small number of third-party suppliers for our drug substance and drug product. In particular, we rely, and expect to continue to rely, on third-party suppliers for certain materials and components required for the production of any product candidates we may develop for our programs. These programs could be adversely affected by a significant interruption in the supply process.

Revenue Recognition

We enter into collaboration agreements that are within the scope of ASC Topic 606, “Revenue from Contracts with Customers”, or ASC 606, under which we license rights to certain of our potential product candidates and perform research and development services. The terms of these contracts typically include payment of the following: non-refundable, upfront fees; reimbursement of research and development costs; development, regulatory, and commercial milestone payments; royalties on net sales of licensed products, and a premium or discount on the sale of our common stock.

Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized for contracts determined to be within the scope of ASC 606, we perform the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when, or as, we satisfy each performance obligation. We only apply the five-step model to contracts when it is probable that we will collect consideration we are entitled to in exchange for the goods or services we transfer to the customer.

The promised goods or services in our arrangements typically consist of license rights to our intellectual property and research and development services. We provide options to additional items in the contract, which will be accounted for as separate contracts if and when the other party elects to exercise such options, unless the option provides a material right to such party. We evaluate the other party’s options for material rights, or options to acquire additional goods or services for free or at a discount. If the other party’s options are determined to represent a material right, the material right is recognized as a separate performance obligation at the outset of the contract. Performance obligations are promised goods or services in a contract to transfer a distinct good or service to the other party and are considered distinct when (i) the other party can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised goods or services are distinct, we consider factors such as the stage of development of the underlying intellectual property, the capabilities of the other party to develop the intellectual property on its own or whether the required expertise is readily available and whether the goods or services are integral or dependent to other goods or services in the contract.

We estimate the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration or variable consideration. At the inception of each contract that includes variable consideration, we evaluate the number of potential payments and the likelihood that the payments will be received. We utilize either the most likely amount method or expected amount method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period.

Our contracts include development, regulatory, and commercial milestone payments that will be assessed under the most likely amount method and constrained if it is probable that a significant revenue reversal would occur. Milestone payments that are not within our control or the counterparty’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, we re-evaluate the probability of achievement of such development, regulatory, and commercial milestones and any related constraint, and if necessary, we adjust our estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration revenues in the period of adjustment. To date, we have not recognized any consideration related to the achievement of development, regulatory, or commercial milestone revenue resulting from our collaboration contracts.

For contracts that include sales-based royalties, including milestone payments based on the level of sales, and where the license is deemed to be the predominant item to which the royalties relate, we recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, we have not recognized any consideration related to sales-based royalty revenue resulting from our collaboration contract.

We allocate the transaction price based on the estimated stand-alone selling price of each of the performance obligations. We must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. We utilize key assumptions to determine the stand-alone selling price for service obligations, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs. Additionally, in determining the standalone selling price for material rights, we utilize comparable transactions, clinical trial success probabilities, and estimates of option exercise likelihood. Variable consideration is

allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts we would expect to receive for the satisfaction of each performance obligation.

The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations that consist of licenses and other promises, we utilize judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. We evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition.

Upfront payments and fees are recorded as deferred revenue upon receipt or when due until we perform our obligations. Amounts are recorded as accounts receivable when our right to consideration is unconditional.

Collaboration And License Agreement (Tables)

6 Months Ended

Jun. 30, 2023

Collaboration and License Agreement

Summary of allocation of transaction price to each unit of account


Performance Obligations (in thousands)	Standalone Selling Price		Transaction Price Allocated
ctLNP technology and research license	$	52,500	$	42,576
First liver program commercialization option license		7,000		5,677
Second liver program commercialization option license		7,000		5,677
First non-liver program commercialization option license		11,700		9,488
Second non-liver program commercialization option license		11,700		9,488
Third liver or non-liver program commercialization option license		6,150		4,987
Total	$	96,050	$	77,893

Summary of transaction price allocated with revenue activity


Performance Obligations	Transaction Price Allocated		Revenue Recognized During		Deferred Revenue
(in thousands)	As of June 30, 2023		Three and Six Months Ended June 30, 2023		As of June 30, 2023
ctLNP technology and research license	$	42,576	$	880	$	32,334
First liver program commercialization option license		5,677		—		4,429
Second liver program commercialization option license		5,677		—		4,429
First non-liver program commercialization option license		9,488		—		7,401
Second non-liver program commercialization option license		9,488		—		7,401
Third liver or non-liver program commercialization option license		4,987		—		3,891
Total	$	77,893	$	880	$	59,885

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	6 Months Ended
	Jun. 11, 2020	Aug. 31, 2021	Jun. 30, 2023	Jul. 31, 2023	Jan. 31, 2023	Dec. 31, 2022	Jan. 31, 2022	Dec. 31, 2021	Jan. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock compensation on account of unvested options			$ 38.1
Unrecognized stock compensation on account of unvested options remaining period over which the compensation is to be recognized			2 years 8 months 12 days
Shares issued during the period		1,795,524
Unvested Stock Awards for Which Performance is not Probable
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock compensation on account of unvested options			$ 1.7
Service Based Options [Member] \| Certain Employees Directors And Consultants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation by share based payment arrangement number of options granted			1,705,581
Share based compensation by share based fair value			$ 3.66
Share based compensation by share based payment weighted average period			4 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock compensation on account of unvested options remaining period over which the compensation is to be recognized			2 years 3 months 18 days
Unrecognized stock compensation on account of restricted common stock			$ 5.9
Shares issued			828,920
Fair value			$ 3.8
Weighted average period			4 years
2020 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock reserved for future issuance	2,547,698
Stock based compensation vesting period service based			4 years
Stock based compensation period of expiry			10 years
Common stock shares available for future issuance			883,445
Unrecognized stock compensation on account of unvested options			$ 32.2
2020 Stock Incentive Plan \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares available for future issuance				499,952
2020 Stock Incentive Plan \| Maximum [Member] \| Additional From 2017 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock reserved for future issuance	7,173,014
2020 Stock Incentive Plan \| Maximum [Member] \| Annual Increase 2021 To 2030
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of common stock shares additionally reserved for issuance	4.00%
Employee Stock Purchase Plan 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock reserved for future issuance					2,115,792	1,520,738	1,520,738	950,931	950,931	481,231
Shares issued			1,826,149
Employee Stock Purchase Plan 2020 \| Maximum [Member] \| Annual Increase 2021 To 2030
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of common stock shares additionally reserved for issuance	1.00%
Number of share instruments newly issued under a share-based compensation plan	1,302,157
Common Stock [Member] \| 2020 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation by share based payment arrangement number of shares authorized for issuance					16,813,962	14,433,745	14,433,745	12,154,517	12,154,517	10,275,717

Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2023
Accounting Policies [Abstract]
Use of estimates	Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses and stock-based compensation expense. We base our estimates on historical experience, known trends and other market-specific or other relevant factors that we believe to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates, as there are changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results may differ from those estimates or assumptions.
Unaudited interim financial information	Unaudited interim financial information The condensed consolidated balance sheet as of December 31, 2022 was derived from audited financial statements but does not include all disclosures required by GAAP. The accompanying unaudited financial statements as of June 30, 2023 and for the three and six months ended June 30, 2023 and 2022 have been prepared by us pursuant to the rules and regulations of the Securities and Exchange Commission, or SEC, for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. These financial statements should be read in conjunction with our audited financial statements included in our Annual Report on Form 10-K that was most recently filed with the SEC. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair presentation of our financial position as of June 30, 2023, the results of operations for the three and six months ended June 30, 2023 and 2022, and cash flows for the six months ended June 30, 2023 and 2022 have been made. The results of operations for the three and six months ended June 30, 2023 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2023 or any other period. Our significant accounting policies are described in Note 2 of the Notes to Consolidated Financial Statements included in our Annual Report on Form 10-K that was most recently filed with the SEC.
Concentrations of credit risk and of significant suppliers	Concentrations of credit risk and of significant suppliers Financial instruments that potentially expose us to concentrations of credit risk consist primarily of cash, cash equivalents, and marketable securities. We believe that we are not exposed to significant credit risk due to the financial strength of the national depository institutions in which our cash, cash equivalents, and marketable securities are held. We maintain our cash equivalents in money market funds that invest in U.S. treasury securities. We have adopted an investment policy that limits the amounts that we may invest in the securities of a single issuer with the exclusion of the U.S. government. We have not experienced any credit losses. We are dependent on a small number of third-party suppliers for our drug substance and drug product. In particular, we rely, and expect to continue to rely, on third-party suppliers for certain materials and components required for the production of any product candidates we may develop for our programs. These programs could be adversely affected by a significant interruption in the supply process.
Revenue Recognition	Revenue Recognition We enter into collaboration agreements that are within the scope of ASC Topic 606, “Revenue from Contracts with Customers”, or ASC 606, under which we license rights to certain of our potential product candidates and perform research and development services. The terms of these contracts typically include payment of the following: non-refundable, upfront fees; reimbursement of research and development costs; development, regulatory, and commercial milestone payments; royalties on net sales of licensed products, and a premium or discount on the sale of our common stock. Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized for contracts determined to be within the scope of ASC 606, we perform the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when, or as, we satisfy each performance obligation. We only apply the five-step model to contracts when it is probable that we will collect consideration we are entitled to in exchange for the goods or services we transfer to the customer. The promised goods or services in our arrangements typically consist of license rights to our intellectual property and research and development services. We provide options to additional items in the contract, which will be accounted for as separate contracts if and when the other party elects to exercise such options, unless the option provides a material right to such party. We evaluate the other party’s options for material rights, or options to acquire additional goods or services for free or at a discount. If the other party’s options are determined to represent a material right, the material right is recognized as a separate performance obligation at the outset of the contract. Performance obligations are promised goods or services in a contract to transfer a distinct good or service to the other party and are considered distinct when (i) the other party can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised goods or services are distinct, we consider factors such as the stage of development of the underlying intellectual property, the capabilities of the other party to develop the intellectual property on its own or whether the required expertise is readily available and whether the goods or services are integral or dependent to other goods or services in the contract. We estimate the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration or variable consideration. At the inception of each contract that includes variable consideration, we evaluate the number of potential payments and the likelihood that the payments will be received. We utilize either the most likely amount method or expected amount method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. Our contracts include development, regulatory, and commercial milestone payments that will be assessed under the most likely amount method and constrained if it is probable that a significant revenue reversal would occur. Milestone payments that are not within our control or the counterparty’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, we re-evaluate the probability of achievement of such development, regulatory, and commercial milestones and any related constraint, and if necessary, we adjust our estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration revenues in the period of adjustment. To date, we have not recognized any consideration related to the achievement of development, regulatory, or commercial milestone revenue resulting from our collaboration contracts. For contracts that include sales-based royalties, including milestone payments based on the level of sales, and where the license is deemed to be the predominant item to which the royalties relate, we recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, we have not recognized any consideration related to sales-based royalty revenue resulting from our collaboration contract. We allocate the transaction price based on the estimated stand-alone selling price of each of the performance obligations. We must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. We utilize key assumptions to determine the stand-alone selling price for service obligations, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs. Additionally, in determining the standalone selling price for material rights, we utilize comparable transactions, clinical trial success probabilities, and estimates of option exercise likelihood. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts we would expect to receive for the satisfaction of each performance obligation. The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations that consist of licenses and other promises, we utilize judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. We evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition. Upfront payments and fees are recorded as deferred revenue upon receipt or when due until we perform our obligations. Amounts are recorded as accounts receivable when our right to consideration is unconditional.

Nature of the Business and Basis of Presentation - Additional information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Aug. 31, 2021	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Date of incorporation				Oct. 21, 2016
Shares issued during the period	1,795,524
Net proceeds from shares issued	$ 12,300
Net Income (Loss)		$ (31,066)	$ (37,929)	$ (63,160)	$ (72,928)
Accumulated deficit		$ (507,925)		$ (507,925)		$ (444,765)

- Definition

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

+ References

+ Details

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Condensed Consolidated Statements of Stockholders' Equity - USD ($)	Common Stock [Member] ModernaTX, Inc	Common Stock [Member] ATM Offering	Common Stock [Member]	Additional Paid-in Capital [Member] ModernaTX, Inc	Additional Paid-in Capital [Member] ATM Offering	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member] ModernaTX, Inc	Accumulated Other Comprehensive Income [Member] ATM Offering	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member] ModernaTX, Inc	Accumulated Deficit [Member] ATM Offering	Accumulated Deficit [Member]	ModernaTX, Inc	ATM Offering	Total
Beginning balance at Dec. 31, 2021			$ 6,000			$ 689,866,000			$ 0			$ (308,126,000)			$ 381,746,000
Beginning balance, shares at Dec. 31, 2021			56,969,618
Issuance/Sale of common stock		$ 0			$ 2,721,000			$ 0			$ 0			$ 2,721,000
Issuance/Sale of common stock, shares		415,637
Issuance of common stock upon exercise of stock options			$ 0			554,000			0			0			554,000
Issuance of common stock upon exercise of stock options, shares			132,374
Vesting of restricted common stock			$ 0			0			0			0			0
Vesting of restricted common stock, shares			14,363
Issuance of common stock under other equity plans			$ 0			363,000			0			0			363,000
Issuance of common stock under other equity plans, shares			65,149
Stock-based compensation expense			$ 0			12,757,000			0			0			12,757,000
Unrealized gains (losses) on marketable securities			0			0			(339,000)			0			(339,000)
Net loss			0			0			0			(72,928,000)			(72,928,000)
Ending balance at Jun. 30, 2022			$ 6,000			706,261,000			(339,000)			(381,054,000)			324,874,000
Ending balance, shares at Jun. 30, 2022			57,597,141
Beginning balance at Mar. 31, 2022			$ 6,000			696,034,000			0			(343,125,000)			352,915,000
Beginning balance, shares at Mar. 31, 2022			57,004,128
Issuance/Sale of common stock		$ 0			$ 2,721,000			$ 0			$ 0			$ 2,721,000
Issuance/Sale of common stock, shares		415,637
Issuance of common stock upon exercise of stock options			$ 0			452,000			0			0			452,000
Issuance of common stock upon exercise of stock options, shares			110,587
Vesting of restricted common stock			$ 0			0			0			0			0
Vesting of restricted common stock, shares			1,640
Issuance of common stock under other equity plans						363,000			0			0			363,000
Issuance of common stock under other equity plans, shares			65,149
Stock-based compensation expense			$ 0			6,691,000			0			0			6,691,000
Unrealized gains (losses) on marketable securities			0			0			(339,000)			0			(339,000)
Net loss			0			0			0			(37,929,000)			(37,929,000)
Ending balance at Jun. 30, 2022			$ 6,000			706,261,000			(339,000)			(381,054,000)			324,874,000
Ending balance, shares at Jun. 30, 2022			57,597,141
Beginning balance at Dec. 31, 2022			$ 6,000			727,335,000			(83,000)			(444,765,000)			282,493,000
Beginning balance, shares at Dec. 31, 2022			59,505,437
Issuance/Sale of common stock	$ 1,000			$ 22,555,000			$ 0			$ 0			$ 22,556,000
Issuance/Sale of common stock, shares	5,859,375
Vesting of restricted common stock			$ 0			(318,000)			0			0			(318,000)
Vesting of restricted common stock, shares			311,757
Issuance of common stock under other equity plans			$ 0			367,000			0			0			367,000
Issuance of common stock under other equity plans, shares			107,681
Stock-based compensation expense			$ 0			12,289,000			0			0			12,289,000
Unrealized gains (losses) on marketable securities			0			0			60,000			0			60,000
Net loss			0			0			0			(63,160,000)			(63,160,000)
Ending balance at Jun. 30, 2023			$ 7,000			762,228,000			(23,000)			(507,925,000)			254,287,000
Ending balance, shares at Jun. 30, 2023			65,784,250
Beginning balance at Mar. 31, 2023			$ 7,000			755,957,000			34,000			(476,859,000)			279,139,000
Beginning balance, shares at Mar. 31, 2023			65,535,663
Vesting of restricted common stock			$ 0			(119,000)			0			0			(119,000)
Vesting of restricted common stock, shares			140,906
Issuance of common stock under other equity plans			$ 0			367,000			0			0			367,000
Issuance of common stock under other equity plans, shares			107,681
Stock-based compensation expense			$ 0			6,023,000			0			0			6,023,000
Unrealized gains (losses) on marketable securities			0			0			(57,000)			0			(57,000)
Net loss			0			0			0			(31,066,000)			(31,066,000)
Ending balance at Jun. 30, 2023			$ 7,000			$ 762,228,000			$ (23,000)			$ (507,925,000)			$ 254,287,000
Ending balance, shares at Jun. 30, 2023			65,784,250

Net Loss per Share (Tables)

6 Months Ended

Jun. 30, 2023

Net Loss per Share

Summary of potential dilutive securities, presented based on amounts outstanding


	June 30,
	2023	2022
Unvested restricted stock units	1,356,667	1,533,821
Stock options to purchase common stock	10,248,676	8,657,817
Total	11,605,343	10,191,638

Cover Page - shares	6 Months Ended
Cover Page - shares	Jun. 30, 2023	Jul. 28, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2023
Document Fiscal Year Focus	2023
Document Transition Report	false
Entity File Number	001-39319
Entity Registrant Name	GENERATION BIO CO.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-4301284
Entity Address, Address Line One	301 Binney Street
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
City Area Code	617
Local Phone Number	655-7500
Title of 12(b) Security	Common Stock, $0.0001 Par Value
Trading Symbol	GBIO
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		65,928,503
Entity Central Index Key	0001733294
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q2
Amendment Flag	false

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value per share	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value per share	$ 0.0001	$ 0.0001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	65,784,250	59,505,437
Common stock, shares outstanding	65,784,250	59,505,437

Accrued Expenses - Summary of Accrued expenses (Detail) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Accrued Expenses
Accrued employee compensation and benefits	$ 4,343	$ 7,970
Accrued external research and development expenses	2,071	1,959
Accrued professional fees	809	1,047
Property and equipment	122	0
Other	406	426
Total	$ 7,751	$ 11,402

Net Loss per Share

6 Months Ended

Jun. 30, 2023

Net Loss per Share

Net Loss per Share

10. Net Loss per Share

We have generated a net loss in all periods presented, therefore the basic and diluted net loss per share attributable to common stockholders are the same as the inclusion of the potentially dilutive securities would be anti-dilutive. We excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated:


	June 30,
	2023	2022
Unvested restricted stock units	1,356,667	1,533,821
Stock options to purchase common stock	10,248,676	8,657,817
Total	11,605,343	10,191,638