0000950170-24-016016 | 10-K | XBRL Viewer

Print Document View Excel Document

Risks and Liquidity - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Risks And Liquidity [Abstract]
Accumulated deficit	$ (456,390)	$ (334,558)

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Marketable Securities

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Investments

4. Marketable Securities

The following is a summary of the Company’s marketable securities as of December 31, 2023 and 2022.


(in thousands)	Amortized Cost		Gross unrealized gain		Gross unrealized loss			Fair Value
December 31, 2023:
Marketable securities
Agency securities	$	10,431	$	19	$	—		$	10,450
Corporate debt securities		67,806		193		(20	)		67,979
U.S. government securities		129,184		72		(41	)		129,215
Total	$	207,421	$	284	$	(61	)	$	207,644
December 31, 2022:
Marketable securities
Corporate debt securities	$	163,208	$	7	$	(1,672	)	$	161,543
U.S. government securities		9,607		—		(27	)		9,580
Total	$	172,815	$	7	$	(1,699	)	$	171,123

The Company’s marketable securities generally have contractual maturity dates of 21 months or less. As of December 31, 2023, the Company had 19 securities with a total fair market value of $75.6 million in an unrealized loss position. The Company believes that any unrealized losses associated with the decline in value of its securities is temporary and is primarily related to the change in market interest rates since purchase and believes that it is more likely than not that it will be able to hold its debt securities to maturity.

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2023	Feb. 09, 2024	Jun. 30, 2023
Document Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Transition Report	false
Entity File Number	001-39527
Entity Interactive Data Current	Yes
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Security Exchange Name	NASDAQ
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Trading Symbol	PRLD
Entity Registrant Name	PRELUDE THERAPEUTICS INC
Entity Central Index Key	0001678660
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Shell Company	false
Entity Ex Transition Period	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-1384762
Entity Address, Address Line One	175 Innovation Boulevard
Entity Address, City or Town	Wilmington
Entity Address, State or Province	DE
Entity Address, Postal Zip Code	19805
City Area Code	302
Local Phone Number	467-1280
Entity Common Stock, Shares Outstanding		54,920,594
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Entity Public Float			$ 77.1
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	Philadelphia, Pennsylvania
Documents Incorporated by Reference	Portions of the Registrant’s Definitive Proxy Statement (“Proxy Statement”) relating to the 2024 Annual Meeting of Stockholders will be filed with the Commission within 120 days after the end of the Registrant’s 2023 fiscal year pursuant to Regulation 14A and is incorporated by reference into Part III of this Report. Except with respect to information specifically incorporated by reference in this Form 10-K, the Proxy Statement is not deemed to be filed as part of this Form 10-K.

Stock-Based Compensation - Schedule of Stock-Based Compensation Expense Recorded in Statements of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 25,616	$ 25,144
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	12,626	11,549
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 12,990	$ 13,595

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 1D
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480483/718-10-35-1D

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480483/718-10-35-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(02)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(03)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(04)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(01)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(02)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(03)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

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

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

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

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

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

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

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

+ Details

Stock-Based Compensation - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) Plan $ / shares shares	Dec. 31, 2022 USD ($) $ / shares	Jan. 01, 2024 shares	Dec. 31, 2020 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of equity incentive plans \| Plan	2
Aggregate intrinsic value of outstanding options	$ 4,900,000
Aggregate intrinsic value of exercisable options	4,700,000
Stock-based compensation expense	$ 25,616,000	$ 25,144,000
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value of options granted \| $ / shares	$ 4.87	$ 5.49
Aggregate intrinsic value of options exercised	$ 100,000	$ 1,100,000
Stock-based compensation expense	24,600,000	23,900,000
Total unrecognized compensation expense related to unvested stock option awards	$ 36,400,000
Total unrecognized compensation expense, weighted-average period	2 years 10 days
Restricted Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period	4 years
Stock-based compensation expense	$ 500,000	800,000
Total unrecognized compensation expense, weighted-average period	2 months 26 days
Share-based payment arrangement, nonvested award, unrecognized expense	$ 100,000
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period	4 years
Stock-based compensation expense	$ 300,000	200,000
Total unrecognized compensation expense, weighted-average period	2 years 1 month 13 days
Share-based payment arrangement, nonvested award, unrecognized expense	$ 600,000
2020 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized \| shares				4,680,000
Number of shares available for future grants \| shares	4,999,564
Terms of award	The total number of shares initially authorized under the Plan was 4,680,000, which was increased on January 1, 2021 and will automatically increase on January 1st of each year, continuing for ten years, in an amount equal to five percent of the total number of shares of the Company’s common stock outstanding on December 31st of the preceding calendar year, subject to the discretion of the board of directors or compensation committee to determine a lesser number of shares shall be added for such year.
Award term	10 years
Percentage of shares outstanding used to calculate annual increase in number of shares that can be issued	5.00%
2020 Equity Incentive Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period	4 years
2020 Equity Incentive Plan \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period	1 year
2020 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future grants \| shares	1,619,292
Terms of award	The number of shares of the Company’s common stock that may be issued pursuant to rights granted under the ESPP shall automatically increase on January 1st of each year and continuing for ten years beginning in 2021, in an amount equal to one percent of the total number of shares of all classes of the Company’s common stock outstanding on December 31st of the preceding calendar year, subject to the discretion of the board of directors or compensation committee to determine a lesser number of shares shall be added for such year.
Award term	10 years
Percentage of shares outstanding used to calculate annual increase in number of shares that can be issued	1.00%
Stock-based compensation expense	$ 300,000	$ 300,000
Shares issued \| shares	169,857
Eligible employees purchase common stock percentage of lower of fair market value	85.00%
Participants accrue rights to purchase maximum common stock amount	$ 25,000
2020 Employee Stock Purchase Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Eligible employees contribution percentage	15.00%
Vesting After One Year \| Restricted Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of stock options vested	25.00%
Vesting After One Year \| Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of stock options vested	25.00%
Vesting After One Year \| 2020 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of stock options vested	25.00%
Subsequent Event \| 2020 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized \| shares			2,745,712
Subsequent Event \| 2020 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock additional capital shares reserved for future issuance \| shares			549,142

Property and Equipment

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Property and Equipment

6. Property and Equipment

Property and equipment consisted of the following:


	December 31,
(in thousands)	2023			2022
Lab equipment	$	6,643		$	5,588
Leasehold improvements		1,582			875
IT equipment		470			40
Furniture and fixtures		1,858			87
Construction in progress		338			1,637
		10,891			8,227
Less accumulated depreciation		(3,566	)		(3,319	)
Property and equipment, net	$	7,325		$	4,908

Common Stock

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Common Stock

9. Common Stock

The Company has two classes of common stock; “voting common stock” and “non-voting common stock.” The holders of the voting common stock are entitled to one vote for each share of voting common stock held at all meetings of stockholders. Except as otherwise required by law, the holders of non-voting common stock shall not be entitled to vote at any meetings of stockholders (or written actions in lieu of meetings) and the shares of non-voting common stock shall not be included in determining the number of shares voting or entitled to vote on any matter. Unless required by law, there shall be no cumulative voting. Any holder of non-voting common stock may elect to convert each share of non-voting common stock into one fully paid and non-assessable share of voting common stock at any time by providing written notice to the Company; provided that as a result of such conversion, such holder, together with its affiliates and any members of a Schedule 13(d) group with such holder, would not beneficially own in excess of 9.99% of the Company’s common stock immediately prior to and following such conversion, unless otherwise as expressly provided for in the Company’s restated certificate of incorporation. However, this ownership limitation may be increased (not to exceed 19.99%) or decreased to any other percentage designated by such holder of non-voting common stock upon 61 days’ notice to the Company.

2023 financings

During the second quarter of 2023, the Company sold 6,761,200 shares of its common stock which comprised of (i) 5,312,978 shares of its voting common stock and (ii) 1,448,222 shares of its non-voting common stock at a price of $5.75 per share and to certain investors in lieu of common stock, the Company sold pre-funded warrants to purchase 12,895,256 shares of voting common stock at a price of $5.7499 per pre-funded warrant, resulting in gross proceeds to the Company of $113.0

million. Of the voting common stock issued, 2,264,456 shares were purchased by the Company’s underwriters in connection with a 30-day option at a price of $5.75 per share. Offering costs of $2.6 million, of which $0.3 million were previously paid and deferred, were recorded to additional paid-in capital in the accompanying balance sheets, resulting in net proceeds of $110.4 million.

During the fourth quarter of 2023, the Company sold in a private placement pre-funded warrants to purchase 7,936,759 shares of voting common stock at a price of $3.1499 per pre-funded warrant, resulting in net proceeds of $24.8 million after deducting offering costs of $0.2 million.

The purchase price per share of each pre-funded warrant represents the per share offering price for the common stock, minus the $0.0001 per share exercise price of such pre-funded warrant. As of December 31, 2023, no pre-funded warrants had been exercised.

The pre-funded warrants were classified as a component of permanent stockholders’ equity within additional paid-in capital and were recorded at the issuance date using a relative fair value allocation method. The pre-funded warrants are equity classified because they (i) are freestanding financial instruments that are legally detachable and separately exercisable from the equity instruments, (ii) are immediately exercisable, (iii) do not embody an obligation for the Company to repurchase its shares, (iv) permit the holders to receive a fixed number of shares of common stock upon exercise, (v) are indexed to the Company’s common stock and (vi) meet the equity classification criteria. In addition, such pre-funded warrants do not provide any guarantee of value or return.

- Definition

The entire disclosure for equity.

+ References

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

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481004/946-505-50-6

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480237/815-40-50-6

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//505/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

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

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-16

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

+ Details

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

3. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying financial statements have been prepared in accordance with generally accepted accounting principles (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) promulgated by the Financial Accounting Standards Board (“FASB”).

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 and disclosure of contingent assets and contingent liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates.

Estimates and assumptions are periodically reviewed, and the effects of the revisions are reflected in the accompanying financial statements in the period they are determined to be necessary. The most significant estimate relates to accrued clinical trial expenses.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to significant concentrations of credit risk consist of cash, cash equivalents, and marketable securities. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant credit risk beyond the normal credit risk associated with commercial banking relationships.

Segment Information

Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company views and manages its operations as a single operating segment.

Fair Value of Financial Instruments

Management believes that the carrying amounts of the Company’s financial instruments, including cash, restricted cash, accounts payable, and accrued expenses, approximate fair value due to the short-term nature of these instruments.

Cash, Cash Equivalents and Restricted cash

The Company’s cash equivalents include short-term highly liquid investments with an original maturity of 90 days or less when purchased and are carried at fair value in the accompanying balance sheets.

Restricted cash comprises a letter of credit with Silicon Valley Bank for the benefit of the landlord in connection with the Company’s new lease facility. See Note 8 (Commitments) for further details.

The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the balance sheet that total to the amounts shown in the statement of cash flows:


	December 31,
(in thousands)	2023		2022
Cash and cash equivalents	$	25,291	$	30,605
Restricted cash		4,044		4,044
Total cash, cash equivalents, and restricted cash shown in statement of cash flows	$	29,335	$	34,649

Marketable Securities

The Company’s marketable securities consist of investments in corporate debt securities, United States, or U.S., government debt securities, and agency securities that are classified as available-for-sale. The securities are carried at fair value with the unrealized gains and losses, net of tax, included in accumulated other comprehensive income (loss), a component of stockholders’ equity. Realized gains and losses as well as credit losses, if any, on marketable securities are included in the Company’s statements of operations. The Company classifies marketable securities that are available for use in current operations as current assets on the balance sheets.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation expense is recognized using the straight-line method over the estimated useful life of the asset, ranging from 5-7 years as follows:


Fixed Asset Type		Estimated useful life
Lab equipment		5 years
IT equipment		5 years
Furniture and fixtures		7 years

Leasehold improvements are amortized over the shorter of the estimated useful life of the assets or the remaining lease term.

Expenditures for repairs and maintenance of assets are charged to expense as incurred, while major betterments are capitalized. Upon retirement or sale, the cost and related accumulated depreciation of assets disposed of are removed from the accounts and any resulting gain or loss is included in the statements of operations.

The Company reviews long-lived assets, such as property and equipment, for impairment when events or changes in circumstances indicate the carrying amount of the assets may not be recoverable. If indicators of impairment are present, the assets are tested for recoverability by comparing the carrying amount of the assets to the related estimated future undiscounted cash flows that the assets are expected to generate. If the expected cash flows are less than the carrying value of the asset, then the asset is considered to be impaired and its carrying value is written down to fair value, based on the related estimated discounted future cash flows.

Leases

The Company accounts for leases in accordance with ASC Topic 842, Leases. The Company's lease for office and laboratory space located in Wilmington, DE is classified as an operating lease. The lease results in an operating right-of-use (ROU) asset, a current operating lease liability, and a non-current operating lease liability in the balance sheet and has a remaining lease term of 162 months. The Company does not have any financing leases. Leases with a term of 12 months or less are considered short-term and a ROU asset and lease obligation are not recognized.

ROU assets represent the right to use an underlying asset for the lease term and the lease liabilities represent an obligation to make lease payments arising from the lease, measured at the present value of the lease payments not yet paid discounted using the discount rate for the lease established at the lease commencement date. The operating lease ROU asset also includes any prepaid lease payments made. Lease expense is recognized over the expected lease term on a straight-line basis.

Comprehensive loss

Comprehensive loss includes net loss and certain changes in stockholders’ equity that are excluded from net loss. The Company’s comprehensive loss for the years ended December 31, 2023 and 2022 comprised net loss and unrealized gain or loss on marketable securities.

Stock-Based Compensation

The Company measures share-based awards at their grant-date fair value and records compensation expense on a straight-line basis over the vesting period of the awards.

Estimating the fair value of share-based awards requires the input of subjective assumptions, including, for stock options, the expected life of the options and stock price volatility. The Company accounts for forfeitures for stock option awards as they occur. The Company uses the Black-Scholes option pricing model to value its stock option awards. The assumptions used in estimating the fair value of share-based awards represent management’s estimate and involve inherent uncertainties and the application of management’s judgment. As a result, if factors change and management uses different assumptions, share-based compensation expense could be materially different for future awards.

The expected life of the stock options is estimated using the “simplified method”, as the Company has limited historical information from which to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior for its stock option grants. The simplified method is the midpoint between the vesting period and the contractual term of the option. For stock price volatility, the Company uses its own historical volatility along with comparable public companies as a basis for its expected volatility to calculate the fair value of option grants. The risk-free rate is based on the U.S. Treasury yield curve commensurate with the expected life of the option.

Grant Income and Research and Development Tax Credits

The Company recognizes grants related to income and Delaware research and development tax credits in other income, net in the statements of operations when the necessary qualifying conditions, as stated in the agreements, are met and all contingencies have been resolved. For the years ended December 31, 2023 and 2022, the Company recorded other income of $1.5 million and $6.1 million, respectively. The Company recognizes grants related to assets as deferred income on the balance sheet. The deferred income is then recognized as grant income over the useful life of the related assets.

Research and Development

Research and development costs are expensed as incurred. Research and development expenses consist principally of personnel costs, including salaries, stock-based compensation, and benefits of employees, and other operational costs related to the Company’s research and development activities, including allocated facility-related expenses and external costs of outside vendors, such as clinical research organizations and clinical manufacturing organizations, and other direct and indirect costs.

Management makes estimates of the Company’s accrued research and development expenses as of each balance sheet date in the Company’s financial statements based on facts and circumstances known to the Company at that time. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Nonrefundable advance payments for goods and services, including fees for process development or manufacturing and distribution of clinical supplies that will be used in future research and development activities, are deferred and recognized as expense in the period that the related goods are consumed or services are performed.

Income Taxes

Income taxes are accounted for under the asset-and-liability method as required by FASB ASC Topic 740, Income Taxes (“ASC 740”). Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period corresponding to the enactment date. Under ASC 740, a valuation allowance is required when it is more likely than not all or some portion of the deferred tax assets will not be realized through generating sufficient future taxable income.

FASB ASC Subtopic 740-10, Accounting for Uncertainty of Income Taxes, (“ASC 740-10”) defines the criterion an individual tax position must meet for any part of the benefit of the tax position to be recognized in financial statements prepared in conformity with GAAP. The Company may recognize the tax benefit from an uncertain tax position only if it is more likely than not such tax position will be sustained on examination by the taxing authorities, based solely on the

technical merits of the respective tax position. The tax benefits recognized in the financial statements from such a tax position should be measured based on the largest benefit having a greater than 50% likelihood of being realized upon ultimate settlement with the tax authority. In accordance with the disclosure requirements of ASC 740-10, the Company’s policy on income statement classification of interest and penalties related to income tax obligations is to include such items as a component of income tax expense.

Net Loss Per Share

Basic net loss per share of common stock is computed by dividing net loss by the weighted-average number of shares of common stock outstanding during each period, including pre-funded warrants to purchase shares of common stock that were issued in a financing transaction in 2023 (Note 9). The weighted-average number of shares of common stock outstanding used in the basic net loss per share calculation does not include unvested restricted stock awards as these instruments are considered contingently issuable shares until they vest. Diluted net loss per share of common stock includes the effect, if any, from the potential exercise of securities, such as stock options, and the effect from unvested restricted stock awards and restricted stock units which would result in the issuance of incremental shares of common stock. For diluted net loss per share, the weighted-average number of shares of common stock is the same for basic net loss per share due to the fact that when a net loss exists, dilutive securities are not included in the calculation as the impact is anti-dilutive. The Company’s unvested restricted stock awards entitle the holder to participate in dividends and earnings of the Company, and, if the Company were to recognize net income, it would have to use the two-class method to calculate earnings per share. The two-class method is not applicable during periods with a net loss, as the holders of the unvested restricted stock awards have no obligation to fund losses.

The following potentially dilutive securities have been excluded from the computation of diluted weighted-average shares of common stock outstanding, as they would be anti-dilutive:


	December 31,
	2023		2022
Unvested restricted stock awards		27,008		201,716
Unvested restricted stock units		103,750		165,000
Stock options		11,898,446		9,390,930
		12,029,204		9,757,646

Amounts in the above table reflect the common stock equivalents.

Recently Issued Accounting Pronouncements

Emerging Growth Company Status

The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act, until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it (i) is no longer an emerging growth company or (ii) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. The Company will remain an emerging growth company until the earliest of (i) the last day of the Company's first fiscal year (a) in which the Company has total annual gross revenues of at least $1.235 billion, or (b) in which the Company is deemed to be a large accelerated filer, which means the market value of the Company's common stock that is held by non-affiliates exceeds $700.0 million as of the prior June 30, (ii) the date on which the Company has issued more than $1.0 billion in non-convertible debt securities during the prior three-year period and (iii) December 31, 2025. As a result, these financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates.

Recently Adopted Accounting Pronouncements

In August 2020, the FASB issued ASU Update No. 2020-06, Debt — Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging — Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity (ASU 2020-06) (“ASU 2020-06”). ASU 2020-06 eliminated the beneficial conversion and cash conversion accounting models in ASC 470-20 which required separate

accounting for embedded conversion features and simplified the settlement assessment to determine whether an instrument qualifies for equity classification. The Company early adopted the new standard on January 1, 2023. The adoption did not have a material impact on the financial statements.

Accounting guidance not yet adopted

In December 2023, the FASB issued ASU Updated No. 2023-09, Income Taxes - Improvements to Income Tax Disclosures. ASU 2023-09 requires enhanced income tax disclosures related to the rate reconciliation and income taxes paid information. For public business entities, the amendments in this Update are effective for annual periods beginning after December 15, 2024 with early adoption permitted. The Company is currently evaluating the impact of this standard but does not expect that it will have a material impact on the financial statements and related disclosures.

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment

Property and equipment consisted of the following:


	December 31,
(in thousands)	2023			2022
Lab equipment	$	6,643		$	5,588
Leasehold improvements		1,582			875
IT equipment		470			40
Furniture and fixtures		1,858			87
Construction in progress		338			1,637
		10,891			8,227
Less accumulated depreciation		(3,566	)		(3,319	)
Property and equipment, net	$	7,325		$	4,908

Commitments - Schedule of Future Minimum Lease Payments Under Lease (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Lease Liability [Line Items]
Operating lease liability	$ 1,481	$ 1,832
Chestnut Run Lease
Lease Liability [Line Items]
2024	1,615
2025	2,746
2026	2,979
2027	3,054
2028	3,130
Thereafter	$ 29,635

STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock Voting Common Stock	Common Stock Non-voting Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2021	$ 285,897	$ 4	$ 1	$ 505,723	$ (711)	$ (219,120)
Beginning balance (shares) at Dec. 31, 2021		36,200,299	11,402,037
Issuance of common stock upon exercise of stock options & vesting of RSUs	389			389
Issuance of common stock upon exercise of stock options & vesting of RSUs, (shares)		222,905
Issuance of common stock under ESPP	426			426
Issuance of common stock under ESPP, (shares)		97,206
Unrealized gain on marketable securities, net of tax	(981)				(981)
Stock-based compensation expense, net of forfeitures of restricted stock	25,144			25,144
Stock-based compensation expense, net of forfeitures of restricted stock (shares)		(23,416)
Net loss	(115,438)					(115,438)
Ending balance at Dec. 31, 2022	195,437	$ 4	$ 1	531,682	(1,692)	(334,558)
Ending balance (shares) at Dec. 31, 2022		36,496,994	11,402,037
Issuance of common stock and prefunded warrants, net of issuance costs of $2.6 million	135,290			135,290
Issuance of common stock and prefunded warrants, net of issuance costs of $2.6 million (shares)		5,312,978	1,448,222
Issuance of common stock upon exercise of stock options & vesting of RSUs	30			30
Issuance of common stock upon exercise of stock options & vesting of RSUs, (shares)		84,166
Issuance of common stock under ESPP	634			634
Issuance of common stock under ESPP, (shares)		169,857
Unrealized gain on marketable securities, net of tax	1,915				1,915
Stock-based compensation expense, net of forfeitures of restricted stock	25,616			25,616
Net loss	(121,832)					(121,832)
Ending balance at Dec. 31, 2023	$ 237,090	$ 4	$ 1	$ 693,252	$ 223	$ (456,390)
Ending balance (shares) at Dec. 31, 2023		42,063,995	12,850,259

Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Weighted-average Shares of Common Stock Outstanding (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	12,029,204	9,757,646
Unvested Restricted Stock Awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	27,008	201,716
Unvested Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	103,750	165,000
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	11,898,446	9,390,930

Common Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2023
Class Of Stock [Line Items]
Gross proceeds from issuance of common stock and prefunded warrants		$ 113.0
Offering costs	$ 0.2	2.6	$ 0.2
Offering costs previously paid and deferred		0.3
Net proceeds from issuance	$ 24.8	$ 110.4
Pre-Funded Warrants
Class Of Stock [Line Items]
Warrants exercise price per share	$ 0.0001		$ 0.0001
Warrants exercised	0		0
Pre-Funded Warrants \| Voting Common Stock
Class Of Stock [Line Items]
Shares issued price per share		$ 5.7499
Warrants to purchase common stock		12,895,256
Pre-Funded Warrants \| Voting Common Stock \| Private Placement
Class Of Stock [Line Items]
Shares issued price per share	$ 3.1499		$ 3.1499
Warrants to purchase common stock	7,936,759		7,936,759
Common Stock
Class Of Stock [Line Items]
Common stock, voting rights			The holders of the voting common stock are entitled to one vote for each share of voting common stock held at all meetings of stockholders
Number of shares sold		6,761,200
Shares issued price per share		$ 5.75
Common Stock \| Minimum
Class Of Stock [Line Items]
Beneficial ownership percentage			9.99%
Common Stock \| Maximum
Class Of Stock [Line Items]
Beneficial ownership percentage			19.99%
Common Stock \| Voting Common Stock
Class Of Stock [Line Items]
Number of shares sold		5,312,978
Shares issued during period		2,264,456	5,312,978
Common Stock \| Non-voting Common Stock
Class Of Stock [Line Items]
Number of shares sold		1,448,222
Shares issued during period			1,448,222

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 71,963	$ 66,067
Research and development credits	20,555	15,234
Research and development capitalization	39,867	19,900
Stock-based compensation	12,990	8,725
Accrued expense	2,539	1,190
Lease liabilities	4,715	511
Gross deferred tax assets	152,629	111,627
Less: valuation allowance	(147,616)	(111,053)
Total deferred tax asset	5,013	574
Deferred tax liability
Right-of-use assets	(4,641)	(500)
Depreciation	(372)	(74)
Total deferred tax liabilities	(5,013)	(574)
Net deferred tax assets	$ 0	$ 0

Nature of Operations

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Nature of Operations

1. Nature of Operations

Prelude Therapeutics Incorporated (the “Company”) is a clinical-stage fully integrated oncology company built on a foundation of drug discovery excellence to deliver novel precision cancer medicines to underserved patients. Since beginning operations in 2016, the Company has devoted substantially all its efforts to research and development, conducting preclinical and clinical studies, recruiting management and technical staff, administration, and raising capital.

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

11. Income Taxes

The tax effects of temporary differences that gave rise to significant portions of the deferred tax assets and liabilities were as follows:


	December 31,
(in thousands)	2023			2022
Deferred tax assets:
Net operating loss carryforwards	$	71,963		$	66,067
Research and development credits		20,555			15,234
Research and development capitalization		39,867			19,900
Stock-based compensation		12,990			8,725
Accrued expense		2,539			1,190
Lease liabilities		4,715			511
Gross deferred tax assets		152,629			111,627
Less: valuation allowance		(147,616	)		(111,053	)
Total deferred tax asset		5,013			574
Deferred tax liability
Right-of-use assets		(4,641	)		(500	)
Depreciation		(372	)		(74	)
Total deferred tax liabilities		(5,013	)		(574	)
Net deferred tax assets	$	—		$	—

The deferred tax assets as of December 31, 2023 and 2022, includes capitalized research and development expenses of $39.9 million and $19.9 million, respectively. The Tax Cuts and Jobs Act passed in 2017 included a provision which requires taxpayers to capitalize and amortize U.S. based research development expenses over a period of five years and non-U.S. based research and development expenses over a period of 15 years effective for tax years beginning after December 31, 2021. In assessing the need for a valuation allowance, management must determine that there will be sufficient taxable income to allow for the realization of deferred tax assets. Based upon the historical and anticipated future losses, management has determined that the deferred tax assets do not meet the more likely than not threshold for realizability. Accordingly, a full valuation allowance has been recorded against the Company’s net deferred tax assets as of December 31, 2023 and December 31, 2022. The valuation allowance increased by $36.6 million and $35.7 million during the years ended December 31, 2023 and 2022, respectively.

A reconciliation of the federal income tax rate to the Company’s effective tax rate is as follows:


	Year ended December 31,
	2023			2022
Federal tax benefit at statutory rate		(21.0	)%		(21.0	)%
State tax, net of federal benefit		(6.6	)		(6.6	)
Permanent differences		1.1			0.8
Research and development		(4.4	)		(3.5	)
Change in valuation allowance		30.0			30.9
Share-based compensation		0.9			-
Other		-			(0.6	)
		0	%		0	%

The following table summarizes carryforwards of federal and state net operating losses (“NOL”) and research tax credits:


	December 31,
(in thousands)	2023		2022
NOL carryforwards - Federal	$	257,976	$	236,898
NOL carryforwards - State		259,051		237,565
Research tax credits - Federal		20,521		15,201
Research tax credits - State		43		43

The NOL carryforwards begin expiring in 2036 for federal and Delaware state income tax purposes, however; all federal, Delaware state, and Kansas state NOL carryforwards generated subsequent to January 1, 2018, are able to be carried forward indefinitely. The NOL carryforwards begin expiring in 2037 and 2042 for Tennessee and Massachusetts, respectively. As of December 31, 2023, the Company also had federal and Delaware research and development tax credit carryforwards of $20.5 million and $43 thousand, respectively, that will begin to expire in 2039 and 2031, respectively, unless previously utilized.

The NOL and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. NOL and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. To date, the Company has not performed an analysis to determine whether or not ownership changes have occurred since inception. Delaware state NOLs may also be limited.

As of December 31, 2023, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company’s statement of operations. Due to NOL and tax credit carry-forwards that remain unutilized, income tax returns for all tax years remain subject to examination by the taxing jurisdictions. The NOL carryforwards remain subject to review until utilized.

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-21

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482526/740-270-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-17

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating expenses:
Research and development	$ 103,393	$ 92,889
General and administrative	28,884	30,651
Total operating expenses	132,277	123,540
Loss from operations	(132,277)	(123,540)
Other income, net	10,445	8,102
Net loss	$ (121,832)	$ (115,438)
Per share information:
Net loss per share of common stock, basic	$ (2.02)	$ (2.44)
Net loss per share of common stock, diluted	$ (2.02)	$ (2.44)
Weighted average common shares outstanding, basic	60,357,052	47,371,589
Weighted average common shares outstanding diluted	60,357,052	47,371,589
Comprehensive loss
Net loss	$ (121,832)	$ (115,438)
Unrealized gain (loss) on marketable securities, net of tax	1,915	(981)
Comprehensive loss	$ (119,917)	$ (116,419)

Fair Value of Financial Instruments - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, assets	$ 207,644	$ 171,123
Agency Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, assets	10,450
Corporate Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, assets	67,979	161,543
U.S. Government Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, assets	129,215	9,580
Recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, assets	24,369	25,996
Recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Money Market Funds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, assets	24,369	25,996
Recurring basis \| Significant other observable inputs (Level 2)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, assets	207,644	171,123
Recurring basis \| Significant other observable inputs (Level 2) \| Agency Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, assets	10,450
Recurring basis \| Significant other observable inputs (Level 2) \| Corporate Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, assets	67,979	161,543
Recurring basis \| Significant other observable inputs (Level 2) \| U.S. Government Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, assets	$ 129,215	$ 9,580

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2023

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

7. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:


	December 31,
(in thousands)	2023		2022
Compensation and related benefits	$	9,157	$	5,682
Research and development		5,666		6,887
Other		945		524
	$	15,768	$	13,093

Stock-Based Compensation

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

10. Stock-Based Compensation

The Company has two equity incentive plans: the 2016 Equity Incentive Plan, as amended, and the 2020 Equity Incentive Plan. New awards can only be granted under the 2020 Equity Incentive Plan (the “Plan”). The total number of shares initially authorized under the Plan was 4,680,000, which was increased on January 1, 2021 and will automatically increase on January 1st of each year, continuing for ten years, in an amount equal to five percent of the total number of shares of the Company’s common stock outstanding on December 31st of the preceding calendar year, subject to the discretion of the board of directors or compensation committee to determine a lesser number of shares shall be added for such year. At December 31, 2023, 4,999,564 shares were available for future grants and on January 1, 2024, 2,745,712 shares were added to the Plan. The Plan provides for the granting of common stock, incentive stock options, nonqualified stock options, restricted stock awards, restricted stock units and/or stock appreciation rights to employees, directors, and other persons, as determined by the Company’s board of directors. The Company’s stock options vest based on the terms in each award agreement, generally over four-year periods with 25% of options vesting after 1 year and then monthly thereafter, and have a term of ten years.

The Company measures stock-based awards at their grant-date fair value and records compensation expense on a straight-line basis over the vesting period of the awards. The Company recorded stock-based compensation expense in the following expense categories in its accompanying statements of operations:


	Year Ended December 31,
(in thousands)	2023		2022
Research and development	$	12,626	$	11,549
General and administrative		12,990		13,595
	$	25,616	$	25,144

Stock Options

The following table summarizes stock option activity for the Plan in the years indicated:


	Number of shares			Weighted average exercise price per share		Weighted average remaining contractual term (years)
Outstanding at January 1, 2022		7,179,482		$	15.36		8.66
Granted		3,884,429		$	7.58
Exercised		(217,905	)	$	1.78
Forfeited		(1,455,076	)	$	17.84
Outstanding at December 31, 2022		9,390,930		$	12.08		8.31
Granted		3,238,898		$	6.68
Exercised		(26,899	)	$	1.78
Forfeited		(704,483	)	$	12.58
Outstanding at December 31, 2023		11,898,446		$	10.60		7.77
Exercisable at December 31, 2023		6,084,483		$	11.62		6.96

The aggregate intrinsic value of options exercised was $0.1 million and $1.1 million during the year ended December 31, 2023 and 2022, respectively. At December 31, 2023, the aggregate intrinsic value of outstanding options and exercisable options was $4.9 million and $4.7 million, respectively.

The following table summarizes information about stock options outstanding and exercisable at December 31, 2023 under the Plan:


	Options Outstanding						Options Exercisable
Range of Exercise Prices	Number Outstanding		Weighted Average Remaining Contractual Life (in years)		Weighted Average Exercise Price		Number Exercisable		Weighted Average Exercise Price
$0.31 - $4.88		3,061,004		6.82	$	2.80		2,400,106	$	2.40
$4.89 - $7.50		3,905,574		8.99		6.57		366,158		5.83
$7.51 - $13.04		3,141,601		7.28		11.87		2,149,353		12.19
$13.05 - $88.98		1,790,267		7.56		30.51		1,168,866		31.32
		11,898,446						6,084,483

The weighted-average grant date fair value of options granted was $4.87 and $5.49 per share for the years ended December 31, 2023 and 2022, respectively. The Company recorded stock-based compensation expense of $24.6 million and $23.9 million for the years ended December 31, 2023 and 2022, respectively, related to stock options. As of December 31, 2023, the total unrecognized compensation expense related to unvested stock option awards was $36.4 million, which the Company expects to recognize over a weighted-average period of 2.03 years.

The fair value of each option was estimated on the date of grant using the weighted average assumptions in the table below:


	Year Ended December 31,
	2023			2022
Expected volatility		83.57	%		84.67	%
Risk-free interest rate		3.82	%		2.73	%
Expected life (in years)		6.02			6.03
Expected dividend yield		—			—

Restricted Stock Awards and Units

The Company issues restricted stock awards (“RSA”) to employees that generally vest over a four-year period with 25% of awards vesting after 1 year and then monthly thereafter. Any unvested shares will be forfeited upon termination of services. The fair value of an RSA is equal to the fair market value price of the Company’s common stock on the date of grant. RSA expense is recorded on a straight-line basis over the vesting period.

The following table summarizes activity related to RSA stock-based payment awards:


	Number of shares			Weighted- average grant date fair value
Unvested balance at January 1, 2022		611,608		$	2.29
Vested		(386,476	)	$	2.05
Forfeited		(23,416	)	$	1.89
Unvested balance at December 31, 2022		201,716		$	2.81
Vested		(174,708	)	$	2.74
Unvested balance at December 31, 2023		27,008		$	3.26

The Company recorded stock-based compensation expense of $0.5 million and $0.8 million for the years ended December 31, 2023 and 2022, respectively, related to RSAs. As of December 31, 2023, the total unrecognized expense related to all RSAs was $0.1 million, which the Company expects to recognize over a weighted-average period of 0.24 years.

The Company issues restricted stock units (“RSU”) to employees that generally vest over a four-year period with 25% of awards vesting after 1 year and then quarterly thereafter. Any unvested shares will be forfeited upon termination of services.

The following table summarizes activity related to RSU stock-based payment awards:


	Number of shares			Weighted- average grant date fair value
Outstanding at January 1, 2022		20,000		$	18.32
Granted		150,000		$	4.86
Forfeited		(5,000	)	$	18.32
Outstanding at December 31, 2022		165,000		$	6.08
Vested		(61,250	)	$	5.96
Outstanding at December 31, 2023		103,750		$	6.16

The Company recorded stock-based compensation expense of $0.3 million and $0.2 million for the years ended December 31, 2023 and 2022, respectively, related to RSUs. At December 31, 2023 the total unrecognized expense related to the RSUs was $0.6 million, which the Company expects to recognize over 2.12 years.

Employee Stock Purchase Plan

The Company has an Employee Stock Purchase Plan (the “ESPP”), which as of December 31, 2023 had 1,619,292 shares of common stock reserved for future issuance. The Company issued 169,857 shares under the ESPP in 2023. The number of shares of the Company’s common stock that may be issued pursuant to rights granted under the ESPP shall automatically increase on January 1st of each year and continuing for ten years beginning in 2021, in an amount equal to one percent of the total number of shares of all classes of the Company’s common stock outstanding on December 31st of the preceding calendar year, subject to the discretion of the board of directors or compensation committee to determine a lesser number of shares shall be added for such year. As such, on January 1, 2024, 549,142 shares were added to the ESPP.

Under the ESPP, eligible employees can purchase the Company’s common stock through accumulated payroll deductions at such times as are established by the compensation committee. Eligible employees may purchase the Company’s common stock at 85% of the lower of the fair market value of the Company’s common stock on the first day of the offering

period or on the last day of the offering period. Eligible employees may contribute up to 15% of their eligible compensation. Under the ESPP, a participant may not accrue rights to purchase more than $25,000 worth of the Company’s common stock for each calendar year in which such right is outstanding.

The ESPP is considered compensatory under the FASB stock compensation rules. Accordingly, share-based compensation expense is determined based on the option’s grant-date fair value as estimated by applying the Black Scholes option-pricing model and is recognized over the withholding period. The Company recognized share-based compensation expense of $0.3 million for both years ended December 31, 2023 and 2022 related to the ESPP.

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Summary of Significant Accounting Policies [Line Items]
Change in accounting principle, ASU, adopted	true
Change in accounting principle, ASU, adoption date	Jan. 01, 2023
Accounting Standards Update [Extensible Enumeration]	us-gaap:AccountingStandardsUpdate202006Member
Other income	$ 10,445	$ 8,102
Remaining lease term	162 months
Lessee finance lease description	The Company does not have any financing leases.
Research and Development Tax Credits
Summary of Significant Accounting Policies [Line Items]
Other income	$ 1,500	$ 6,100
Minimum
Summary of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	5 years
Property, Plant and Equipment, Depreciation Method [Extensible Enumeration]	us-gaap:UsefulLifeTermOfLeaseMember
Maximum
Summary of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	7 years
Property, Plant and Equipment, Depreciation Method [Extensible Enumeration]	us-gaap:UsefulLifeTermOfLeaseMember
Percentage of tax benefit recognized upon settlement	50.00%
Emerging growth revenue	$ 1,235,000
Common stock held by non-affiliates	700,000
Maximum \| Non-Convertible Debt Securities [Member]
Summary of Significant Accounting Policies [Line Items]
Emerging growth debt	$ 1,000,000

Commitments (Tables)

12 Months Ended

Dec. 31, 2023

Chestnut Run Lease

Schedule of Future Minimum Lease Payments Under Lease

he estimated rent payments related to the Chestnut Run Lease are as follows:


(in thousands)
2024	$	1,615
2025		2,746
2026		2,979
2027		3,054
2028		3,130
Thereafter		29,635

Stock-Based Compensation - Summary of Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Payment Arrangement [Abstract]
Number of shares, Outstanding at beginning of period	9,390,930	7,179,482
Number of shares, Granted	3,238,898	3,884,429
Number of shares, Exercised	(26,899)	(217,905)
Number of shares, Forfeited	(704,483)	(1,455,076)
Number of shares, Outstanding at end of period	11,898,446	9,390,930	7,179,482
Number of shares, Exercisable at December 31, 2023	6,084,483
Weighted average exercise price per share, Outstanding at beginning of period	$ 12.08	$ 15.36
Weighted average exercise price per share, Granted	6.68	7.58
Weighted average exercise price per share, Exercised	1.78	1.78
Weighted average exercise price per share, Forfeited	12.58	17.84
Weighted average exercise price per share, Outstanding at end of period	10.6	$ 12.08	$ 15.36
Weighted average exercise price per share, Exercisable at December 31, 2023	$ 11.62
Weighted average remaining contractual term (years), Outstanding	7 years 9 months 7 days	8 years 3 months 21 days	8 years 7 months 28 days
Weighted average remaining contractual term (years), Exercisable	6 years 11 months 15 days

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Compensation and related benefits	$ 9,157	$ 5,682
Research and development	5,666	6,887
Other	945	524
Accrued expenses and other current liabilities	$ 15,768	$ 13,093

Income Taxes - Schedule of Federal and State Net Operating Losses and Research Tax Credits (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Operating Loss Carryforwards [Line Items]
NOL carryforwards	$ 71,963	$ 66,067
Federal
Operating Loss Carryforwards [Line Items]
NOL carryforwards	257,976	236,898
Research tax credits	20,521	15,201
State
Operating Loss Carryforwards [Line Items]
NOL carryforwards	259,051	237,565
Research tax credits	$ 43	$ 43

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of Stock-Based Compensation Expense Recorded in Statements of Operations

The Company recorded stock-based compensation expense in the following expense categories in its accompanying statements of operations:


	Year Ended December 31,
(in thousands)	2023		2022
Research and development	$	12,626	$	11,549
General and administrative		12,990		13,595
	$	25,616	$	25,144

Summary of Stock Option Activity

The following table summarizes stock option activity for the Plan in the years indicated:


	Number of shares			Weighted average exercise price per share		Weighted average remaining contractual term (years)
Outstanding at January 1, 2022		7,179,482		$	15.36		8.66
Granted		3,884,429		$	7.58
Exercised		(217,905	)	$	1.78
Forfeited		(1,455,076	)	$	17.84
Outstanding at December 31, 2022		9,390,930		$	12.08		8.31
Granted		3,238,898		$	6.68
Exercised		(26,899	)	$	1.78
Forfeited		(704,483	)	$	12.58
Outstanding at December 31, 2023		11,898,446		$	10.60		7.77
Exercisable at December 31, 2023		6,084,483		$	11.62		6.96

Summary of Information about Stock Options Outstanding

The following table summarizes information about stock options outstanding and exercisable at December 31, 2023 under the Plan:


	Options Outstanding						Options Exercisable
Range of Exercise Prices	Number Outstanding		Weighted Average Remaining Contractual Life (in years)		Weighted Average Exercise Price		Number Exercisable		Weighted Average Exercise Price
$0.31 - $4.88		3,061,004		6.82	$	2.80		2,400,106	$	2.40
$4.89 - $7.50		3,905,574		8.99		6.57		366,158		5.83
$7.51 - $13.04		3,141,601		7.28		11.87		2,149,353		12.19
$13.05 - $88.98		1,790,267		7.56		30.51		1,168,866		31.32
		11,898,446						6,084,483

Schedule of Fair Value of Each Option Estimated on Date of Grant Using Weighted Average Assumptions

The fair value of each option was estimated on the date of grant using the weighted average assumptions in the table below:


	Year Ended December 31,
	2023			2022
Expected volatility		83.57	%		84.67	%
Risk-free interest rate		3.82	%		2.73	%
Expected life (in years)		6.02			6.03
Expected dividend yield		—			—

Summary of Activity related to RSA Stock-Based Payment Awards

The following table summarizes activity related to RSA stock-based payment awards:


	Number of shares			Weighted- average grant date fair value
Unvested balance at January 1, 2022		611,608		$	2.29
Vested		(386,476	)	$	2.05
Forfeited		(23,416	)	$	1.89
Unvested balance at December 31, 2022		201,716		$	2.81
Vested		(174,708	)	$	2.74
Unvested balance at December 31, 2023		27,008		$	3.26

Summary of Activity related to RSU Stock-Based Payment Awards

The following table summarizes activity related to RSU stock-based payment awards:


	Number of shares			Weighted- average grant date fair value
Outstanding at January 1, 2022		20,000		$	18.32
Granted		150,000		$	4.86
Forfeited		(5,000	)	$	18.32
Outstanding at December 31, 2022		165,000		$	6.08
Vested		(61,250	)	$	5.96
Outstanding at December 31, 2023		103,750		$	6.16

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Line Items]
Deferred tax assets, valuation allowance increase	$ 36,600,000	$ 35,700,000
Research and development tax credits	20,555,000	15,234,000
Deferred tax assets, capitalized research and development expense	$ 39,867,000	$ 19,900,000
NOL and tax credit carryforwards	The NOL and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. NOL and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions.
Accrued interest related to uncertain tax positions	$ 0
Accrued penalties related to uncertain tax positions	0
Interest related to uncertain tax positions	0
Penalties related to uncertain tax positions	$ 0
Non-U.S. Based
Income Tax Disclosure [Line Items]
Taxpayers required period to capitalize and amortize research development expense	15 years
U.S. Based
Income Tax Disclosure [Line Items]
Taxpayers required period to capitalize and amortize research development expense	5 years
Tennessee
Income Tax Disclosure [Line Items]
NOL carryforwards expiration year	2037
Massachusetts
Income Tax Disclosure [Line Items]
NOL carryforwards expiration year	2042
Internal Revenue Service (IRS)
Income Tax Disclosure [Line Items]
Research and development tax credits	$ 20,500,000
Tax credits expiration year	2039
Delaware
Income Tax Disclosure [Line Items]
Research and development tax credits	$ 43,000
Tax credits expiration year	2031

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accounting Policies [Abstract]
Cash and cash equivalents	$ 25,291	$ 30,605
Restricted cash	4,044	4,044
Total cash, cash equivalents, and restricted cash shown in statement of cash flows	$ 29,335	$ 34,649

Marketable Securities - Schedule of Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Marketable Securities [Line Items]
Marketable securities, Amortized cost	$ 207,421	$ 172,815
Marketable securities, Gross unrealized gain	284	7
Marketable securities, Gross unrealized loss	(61)	(1,699)
Marketable securities, Fair value	207,644	171,123
Agency Securities
Marketable Securities [Line Items]
Marketable securities, Amortized cost	10,431
Marketable securities, Gross unrealized gain	19
Marketable securities, Fair value	10,450
Corporate Debt Securities
Marketable Securities [Line Items]
Marketable securities, Amortized cost	67,806	163,208
Marketable securities, Gross unrealized gain	193	7
Marketable securities, Gross unrealized loss	(20)	(1,672)
Marketable securities, Fair value	67,979	161,543
U.S. Government Securities
Marketable Securities [Line Items]
Marketable securities, Amortized cost	129,184	9,607
Marketable securities, Gross unrealized gain	72
Marketable securities, Gross unrealized loss	(41)	(27)
Marketable securities, Fair value	$ 129,215	$ 9,580

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Schedule of Deferred Tax Assets and Liabilities

The tax effects of temporary differences that gave rise to significant portions of the deferred tax assets and liabilities were as follows:


	December 31,
(in thousands)	2023			2022
Deferred tax assets:
Net operating loss carryforwards	$	71,963		$	66,067
Research and development credits		20,555			15,234
Research and development capitalization		39,867			19,900
Stock-based compensation		12,990			8,725
Accrued expense		2,539			1,190
Lease liabilities		4,715			511
Gross deferred tax assets		152,629			111,627
Less: valuation allowance		(147,616	)		(111,053	)
Total deferred tax asset		5,013			574
Deferred tax liability
Right-of-use assets		(4,641	)		(500	)
Depreciation		(372	)		(74	)
Total deferred tax liabilities		(5,013	)		(574	)
Net deferred tax assets	$	—		$	—

Schedule of Reconciliation of the Federal Income tax Rate to Effective Tax Rate

A reconciliation of the federal income tax rate to the Company’s effective tax rate is as follows:


	Year ended December 31,
	2023			2022
Federal tax benefit at statutory rate		(21.0	)%		(21.0	)%
State tax, net of federal benefit		(6.6	)		(6.6	)
Permanent differences		1.1			0.8
Research and development		(4.4	)		(3.5	)
Change in valuation allowance		30.0			30.9
Share-based compensation		0.9			-
Other		-			(0.6	)
		0	%		0	%

Schedule of Federal and State Net Operating Losses and Research Tax Credits

The following table summarizes carryforwards of federal and state net operating losses (“NOL”) and research tax credits:


	December 31,
(in thousands)	2023		2022
NOL carryforwards - Federal	$	257,976	$	236,898
NOL carryforwards - State		259,051		237,565
Research tax credits - Federal		20,521		15,201
Research tax credits - State		43		43

Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis

The following fair value hierarchy table presents information about the Company’s assets and liabilities measured at fair value on a recurring basis:


	Fair value measurement at reporting date using
(in thousands)	Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
December 31, 2023:
Assets:
Cash equivalents (Money Market Funds)	$	24,369	$	—	$	—
Marketable securities
Agency securities				10,450
Corporate debt securities		—		67,979		—
U.S. government securities		—		129,215		—
Total	$	24,369	$	207,644	$	—

December 31, 2022:
Assets:
Cash equivalents (Money Market Funds)	$	25,996	$	—	$	—
Marketable securities
Corporate debt securities		—		161,543		—
U.S. government securities		—		9,580		—
Total	$	25,996	$	171,123	$	—

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2023

Payables and Accruals [Abstract]

Summary of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:


	December 31,
(in thousands)	2023		2022
Compensation and related benefits	$	9,157	$	5,682
Research and development		5,666		6,887
Other		945		524
	$	15,768	$	13,093

STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (PARENTHETICAL) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) shares
Issuance costs \| $	$ 2.8
Shares withheld for employee taxes \| shares	3,983

BALANCE SHEETS (PARENTHETICAL) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Voting Common Stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	487,149,741	487,149,741
Common stock, shares, issued	42,063,995	36,496,994
Common stock, shares, outstanding	42,063,995	36,496,994
Non-voting Common Stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	12,850,259	12,850,259
Common stock, shares, issued	12,850,259	11,402,037
Common stock, shares, outstanding	12,850,259	11,402,037

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of presentation

Basis of Presentation

Use of estimates

Use of Estimates

Concentration of Credit Risk

Segment Information

Fair Value of Financial Instruments

Cash, Cash Equivalents and Restricted Cash

Cash, Cash Equivalents and Restricted cash

The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the balance sheet that total to the amounts shown in the statement of cash flows:


	December 31,
(in thousands)	2023		2022
Cash and cash equivalents	$	25,291	$	30,605
Restricted cash		4,044		4,044
Total cash, cash equivalents, and restricted cash shown in statement of cash flows	$	29,335	$	34,649

Marketable Securities

Property and Equipment


Fixed Asset Type		Estimated useful life
Lab equipment		5 years
IT equipment		5 years
Furniture and fixtures		7 years

Leasehold improvements are amortized over the shorter of the estimated useful life of the assets or the remaining lease term.

Leases

Comprehensive Loss

Comprehensive loss

Stock-Based Compensation

The Company measures share-based awards at their grant-date fair value and records compensation expense on a straight-line basis over the vesting period of the awards.

Grant Income and Research and Development Tax Credits

Research and Development

Income taxes

Income Taxes

Net Loss Per Share

The following potentially dilutive securities have been excluded from the computation of diluted weighted-average shares of common stock outstanding, as they would be anti-dilutive:


	December 31,
	2023		2022
Unvested restricted stock awards		27,008		201,716
Unvested restricted stock units		103,750		165,000
Stock options		11,898,446		9,390,930
		12,029,204		9,757,646

Amounts in the above table reflect the common stock equivalents.

Recently Issued Accounting Pronouncements

Emerging Growth Company Status

Recently Adopted Accounting Pronouncements

Accounting guidance not yet adopted

Commitments

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments

8. Commitments

Leases

The Company leased office and laboratory space in Wilmington, Delaware under a noncancelable lease (the “Lease”) for which the lease term ended on December 31, 2023. The discount rate used to account for the Company’s operating lease under ASC 842, Leases, was the Company’s estimated incremental borrowing rate of 9.5%.

In 2021, the Company entered into a lease agreement for office and lab space at Chestnut Run Plaza in Wilmington, Delaware (the “Chestnut Run Lease”). The premises includes approximately 81,000 rentable square feet and has an initial term of 162 months with 3 five-year extension options and certain expansion rights. Neither the option to extend nor the expansion rights were recognized as part of the Company's measurement of the ROU asset and operating lease liability as of December 31, 2023. Under the terms of the Chestnut Run Lease, the landlord provided an allowance towards the cost of completing tenant improvements for the premises. The Company concluded that the improvements resulting from both the landlord's build-out and the tenant improvements are the landlord's assets for accounting purposes. Costs incurred by the Company related to tenant improvements in excess of the landlord's allowance have been treated as prepaid rent and increased the right-of-use asset on the commencement date. The Chestnut Run Lease commenced for accounting purposes in December 2023 when the Company took control of the leased space. On the commencement date, the Company recorded approximately $30.6 million and $16.7 million of right-of-use asset and lease liability, respectively. The right-of-use asset includes approximately $13.9 million related to prepaid rent which was reclassified from long-term prepaid assets. The discount rate used to account for the Company’s operating lease under ASC 842, Leases, is the Company’s estimated incremental borrowing rate of 15.0%. The Company's incremental borrowing rate reflects a collateralized borrowing with a similar term and amount as the Chestnut Run Lease.

Lease cost for the year ended December 31, 2023 was $2.5 million, including $0.2 million of short-term lease cost. Lease cost for the year ended December 31, 2022 was $2.1 million, including $0.3 million of short-term lease cost. Cash paid for amounts included in the measurement of operating lease liabilities for the years ended December 31, 2023 and 2022 was $1.9 million and $1.8 million, respectively.

As of December 31, 2023 the estimated rent payments related to the Chestnut Run Lease are as follows:


(in thousands)
2024	$	1,615
2025		2,746
2026		2,979
2027		3,054
2028		3,130
Thereafter		29,635

The Company paid a security deposit in the form of a letter of credit with Silicon Valley Bank of $4.0 million which is included in the balance sheet as restricted cash as of December 31, 2023 and 2022. The security deposit may be reduced to $0.5 million over time in accordance with the terms of the Chestnut Run Lease.

In connection with the Company’s expansion of operations in the State of Delaware, the Company was approved for a grant from the State of Delaware in 2021 that will provide up to $5.5 million in reimbursements over three years for the development of lab space in addition to increasing jobs in Delaware to meet specific targeted levels through 2023. During the third quarter of 2022, the Company was approved for an additional grant from the State of Delaware for the development of lab space in the amount of $1.0 million. In 2022, the Company received cash of $3.4 million from the grants for the development of lab space. The Company has met the minimum requirements stated in the grant agreement in order to not be required to pay back any portion of the $3.4 million disbursed. The Company has deferred the recognition of these grant funds as they relate to capitalized costs and has classified them as long-term liabilities on the balance sheet. In December 2023, the Company began to recognize the grant funds in other income and will continue to do so over the useful life of the related assets. If the Company leaves the State of Delaware within five years of the disbursement, the Company is required to return an amount equal to the amount of grant funds disbursed on a pro-rated basis.

Employment Agreements

The Company entered into employment agreements with key personnel providing for compensation and severance in certain circumstances, as defined in the respective employment agreements.

401(k) Defined Contribution Plan

The Company sponsors a 401(k) defined‑contribution plan covering all employees. Participants are permitted to contribute up to 100% of their eligible annual pretax compensation up to an established federal limit on aggregate participant contributions. The Company provides a match with a maximum amount of 3% of the participant’s compensation. During the years ended December 31, 2023 and 2022 the Company made matching contributions of $0.7 million and $0.6 million, respectively.

Research Collaboration Agreement

In November 2023, the Company entered into a multi-year, multi-program agreement with AbCellera to jointly discover, develop, and commercialize novel oncology medicines for up to five programs. Under the terms of the agreement, AbCellera will lead manufacturing activities and the Company will lead clinical development and global commercialization, subject to AbCellera’s option to co-promote any resulting commercial products in the United States. If, at any point one party in the collaboration opts-out of future co-development cost sharing, that party will be entitled to a royalty from commercialization of the collaboration target, dependent on the proportion of their co-development contributions compared to the total development costs of a target as defined within the agreement. The Company concluded that the agreement with AbCellera will be accounted for under the scope of ASC 808 as both parties will actively participate in joint operating activities and are exposed to significant risks and rewards. Under ASC 808, certain transactions between collaborative arrangement participants should follow the accounting for revenue under ASC 606 when the collaborative arrangement participant is a customer for a distinct good or service. The Company determined that co-development arrangement as defined in our agreement with AbCellera does not meet the definition of a customer as defined by ASC 606. As a result, these activities will be accounted for as research and development costs. Costs related to the AbCellera collaboration were not material for the year ended December 31, 2023.

Other Research and Development Arrangements

The Company enters into agreements with CROs to assist in the performance of research and development activities. Expenditures to CROs will represent a significant cost in clinical development for the Company.

BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 25,291	$ 30,605
Marketable securities	207,644	171,123
Prepaid expenses and other current assets	2,654	2,652
Total current assets	235,589	204,380
Restricted cash	4,044	4,044
Property and equipment, net	7,325	4,908
Right-of-use asset	30,412	1,792
Prepaid expenses and other non-current assets	295	5,376
Total assets	277,665	220,500
Current liabilities:
Accounts payable	4,580	6,777
Accrued expenses and other current liabilities	15,768	13,093
Operating lease liability	1,481	1,832
Total current liabilities	21,829	21,702
Other liabilities	3,339	3,361
Operating lease liability	15,407
Total liabilities	40,575	25,063
Commitments (note 8)
Stockholders’ equity:
Additional paid-in capital	693,252	531,682
Accumulated other comprehensive income (loss)	223	(1,692)
Accumulated deficit	(456,390)	(334,558)
Total stockholders’ equity	237,090	195,437
Total liabilities and stockholders’ equity	277,665	220,500
Voting Common Stock
Stockholders’ equity:
Common stock	4	4
Non-voting Common Stock
Stockholders’ equity:
Common stock	$ 1	$ 1

Income Taxes - Schedule of Reconciliation of the Federal Income tax Rate to Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal tax benefit at statutory rate	(21.00%)	(21.00%)
State tax, net of federal benefit	6.60%	(6.60%)
Permanent differences	(1.10%)	0.80%
Research and development	4.40%	(3.50%)
Change in valuation allowance	(30.00%)	30.90%
Share-based compensation	0.90%
Other		(0.60%)
Effective tax rate	0.00%	0.00%

Stock-Based Compensation - Summary of Activity related to RSA Stock-Based Payment Awards (Details) - Restricted Stock Awards - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, Unvested balance at beginning of period	201,716	611,608
Number of shares, Vested	(174,708)	(386,476)
Number of shares, Forfeited		(23,416)
Number of shares, Unvested balance at end of period	27,008	201,716
Weighted-average grant date fair value, Unvested balance at beginning of period	$ 2.81	$ 2.29
Weighted-average grant date fair value, Vested	2.74	2.05
Weighted-average grant date fair value, Forfeited		1.89
Weighted-average grant date fair value, Unvested balance at end of period	$ 3.26	$ 2.81

- Definition

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

+ References

+ Details

Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

5. Fair Value of Financial Instruments

Fair value is the price that could be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value determination in accordance with applicable accounting guidance requires that a number of significant judgments be made. Additionally, fair value is used on a nonrecurring basis to evaluate assets for impairment or as required for disclosure purposes by applicable accounting guidance on disclosures about fair value of financial instruments. Depending on the nature of the assets and liabilities, various valuation techniques and assumptions are used when estimating fair value. The Company follows the provisions of ASC 820, Fair Value Measurement, for financial assets and liabilities measured on a recurring basis. The guidance requires fair value measurements be classified and disclosed in one of the following three categories:

•

Level 1: Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities.

•

Level 2: Quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liabilities.

•

Level 3: Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).

The following fair value hierarchy table presents information about the Company’s assets and liabilities measured at fair value on a recurring basis:


	Fair value measurement at reporting date using
(in thousands)	Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
December 31, 2023:
Assets:
Cash equivalents (Money Market Funds)	$	24,369	$	—	$	—
Marketable securities
Agency securities				10,450
Corporate debt securities		—		67,979		—
U.S. government securities		—		129,215		—
Total	$	24,369	$	207,644	$	—

December 31, 2022:
Assets:
Cash equivalents (Money Market Funds)	$	25,996	$	—	$	—
Marketable securities
Corporate debt securities		—		161,543		—
U.S. government securities		—		9,580		—
Total	$	25,996	$	171,123	$	—

- 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

Risks and Liquidity

12 Months Ended

Dec. 31, 2023

Risks And Liquidity [Abstract]

Risks and Liquidity

2. Risks and Liquidity

The Company is subject to a number of risks common to early-stage companies in the biotechnology industry. Principal among these risks are the uncertainties in the development process, development of the same or similar technological innovations by competitors, protection of proprietary technology, dependence on key personnel, compliance with government regulations and approval requirements, and the need to obtain additional financing to fund operations. Product candidates currently under development will require significant additional research and development efforts, including extensive pre-clinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure, and extensive compliance-reporting capabilities. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s technology will be obtained, that any products developed will obtain necessary government regulatory approval, or that any approved products will be commercially viable. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees, consultants and contractors.

Since its inception, the Company has incurred operating losses and had an accumulated deficit of $456.4 million at December 31, 2023. The Company has no revenue to date and devotes its efforts to research and development. The Company anticipates incurring additional losses until such time, if ever, that it can generate significant sales of its product candidates currently in development.

The Company believes that its cash, cash equivalents and marketable securities as of December 31, 2023 will be sufficient to fund its operating expenses and capital expenditure requirements into 2026.

To fund its operating expenses and capital expenditure requirements after that date, the Company plans to seek additional funding through public or private equity offerings, debt financings, collaborations, strategic alliances and licensing arrangements. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into strategic alliances or other arrangements on favorable terms, or at all. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. If the Company is unable to obtain funding, the Company could be required to delay, reduce or eliminate research and development programs, product portfolio expansion or future commercialization efforts, which could adversely affect its business prospects.

Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Schedule of Marketable Securities

The following is a summary of the Company’s marketable securities as of December 31, 2023 and 2022.


(in thousands)	Amortized Cost		Gross unrealized gain		Gross unrealized loss			Fair Value
December 31, 2023:
Marketable securities
Agency securities	$	10,431	$	19	$	—		$	10,450
Corporate debt securities		67,806		193		(20	)		67,979
U.S. government securities		129,184		72		(41	)		129,215
Total	$	207,421	$	284	$	(61	)	$	207,644
December 31, 2022:
Marketable securities
Corporate debt securities	$	163,208	$	7	$	(1,672	)	$	161,543
U.S. government securities		9,607		—		(27	)		9,580
Total	$	172,815	$	7	$	(1,699	)	$	171,123

Stock-Based Compensation - Summary of Information about Stock Options Outstanding (Details)	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options Outstanding, Number \| shares	11,898,446
Options Exercisable, Number Exercisable \| shares	6,084,483
$0.31 - $4.88
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Range of Exercise Prices, Minimum	$ 0.31
Range of Exercise Prices, Maximum	$ 4.88
Options Outstanding, Number \| shares	3,061,004
Options Outstanding, Weighted Average Remaining Contractual Life (in years)	6 years 9 months 25 days
Options Outstanding, Weighted Average Exercise Price	$ 2.80
Options Exercisable, Number Exercisable \| shares	2,400,106
Options Exercisable, Weighted Average Exercise Price	$ 2.40
$4.89 - $7.50
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Range of Exercise Prices, Minimum	4.89
Range of Exercise Prices, Maximum	$ 7.50
Options Outstanding, Number \| shares	3,905,574
Options Outstanding, Weighted Average Remaining Contractual Life (in years)	8 years 11 months 26 days
Options Outstanding, Weighted Average Exercise Price	$ 6.57
Options Exercisable, Number Exercisable \| shares	366,158
Options Exercisable, Weighted Average Exercise Price	$ 5.83
$7.51 - $13.04
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Range of Exercise Prices, Minimum	7.51
Range of Exercise Prices, Maximum	$ 13.04
Options Outstanding, Number \| shares	3,141,601
Options Outstanding, Weighted Average Remaining Contractual Life (in years)	7 years 3 months 10 days
Options Outstanding, Weighted Average Exercise Price	$ 11.87
Options Exercisable, Number Exercisable \| shares	2,149,353
Options Exercisable, Weighted Average Exercise Price	$ 12.19
$13.05 - $88.98
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Range of Exercise Prices, Minimum	13.05
Range of Exercise Prices, Maximum	$ 88.98
Options Outstanding, Number \| shares	1,790,267
Options Outstanding, Weighted Average Remaining Contractual Life (in years)	7 years 6 months 21 days
Options Outstanding, Weighted Average Exercise Price	$ 30.51
Options Exercisable, Number Exercisable \| shares	1,168,866
Options Exercisable, Weighted Average Exercise Price	$ 31.32

Stock-Based Compensation - Summary of Activity related to RSU Stock-Based Payment Awards (Details) - Restricted Stock Units - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, Unvested balance at beginning of period	165,000	20,000
Number of shares, Granted		150,000
Number of shares, Forfeited		(5,000)
Number of shares, Vested	(61,250)
Number of shares, Unvested balance at end of period	103,750	165,000
Weighted-average grant date fair value, Unvested balance at beginning of period	$ 6.08	$ 18.32
Weighted-average grant date fair value, Granted		4.86
Weighted-average grant date fair value, Forfeited		18.32
Weighted-average grant date fair value, Vested	5.96
Weighted-average grant date fair value, Unvested balance at end of period	$ 6.16	$ 6.08

STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Cash flows used in operating activities:
Net loss	$ (121,832)	$ (115,438)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,169	1,324
Noncash lease expense	1,936	1,718
Stock-based compensation	25,616	25,144
Amortization of premium and discount on marketable securities, net	(3,473)	2,591
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(297)	(3,843)
Accounts payable	(2,270)	(347)
Accrued expenses and other liabilities	2,522	6,833
Long-term prepaid expenses and other long-term assets	(8,810)
Operating lease liabilities	(1,624)	(1,711)
Net cash used in operating activities	(107,063)	(83,729)
Cash flows (used in) provided by investing activities:
Purchases of marketable securities	(221,633)	(119,223)
Proceeds from maturities of marketable securities	190,500	203,933
Purchases of property and equipment	(3,513)	(3,019)
Net cash (used in) provided by investing activities	(34,646)	81,691
Cash flows provided by financing activities:
Proceeds from issuance of common stock and pre-funded warrants, net of offering costs	135,731
Proceeds from issuance of common stock in connection with the exercise of stock options	47	389
Proceeds from the issuance of common stock under ESPP	634	426
Payment of withholding taxes related to stock-based compensation to employees	(17)
Net cash provided by financing activities	136,395	815
Net decrease in cash and cash equivalents	(5,314)	(1,223)
Cash, cash equivalents and restricted cash at beginning of year	34,649	35,872
Cash, cash equivalents and restricted cash at end of year	29,335	34,649
Supplemental disclosures:
Operating lease right-of-use assets obtained in exchange for operating lease liabilities	16,680	1,803
Property and equipment in accounts payable	163	90
Unrealized gain (loss) on marketable securities	1,915	$ (981)
Offering costs in accrued expenses and other current liabilities	$ 131

Summary of Significant Accounting Policies - Schedule of Property Plant and Equipment Useful Life (Details)	Dec. 31, 2023
Lab equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years
IT equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	7 years

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Schedule of Reconciliation of Cash and Cash Equivalents and Restricted Cash

The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the balance sheet that total to the amounts shown in the statement of cash flows:


	December 31,
(in thousands)	2023		2022
Cash and cash equivalents	$	25,291	$	30,605
Restricted cash		4,044		4,044
Total cash, cash equivalents, and restricted cash shown in statement of cash flows	$	29,335	$	34,649

Schedule of Property Plant and Equipment Useful Life


Fixed Asset Type		Estimated useful life
Lab equipment		5 years
IT equipment		5 years
Furniture and fixtures		7 years

Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Weighted-average Shares of Common Stock Outstanding

The following potentially dilutive securities have been excluded from the computation of diluted weighted-average shares of common stock outstanding, as they would be anti-dilutive:


	December 31,
	2023		2022
Unvested restricted stock awards		27,008		201,716
Unvested restricted stock units		103,750		165,000
Stock options		11,898,446		9,390,930
		12,029,204		9,757,646

Commitments - Additional Information (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2022 USD ($)	Dec. 31, 2023 USD ($) ft² Extension	Dec. 31, 2022 USD ($)
Other Commitments [Line Items]
Operating lease estimated incremental borrowing rate percent		9.50%
Right-of-use asset		$ 30,412	$ 1,792
Lease cost		2,500	2,100
Short-term lease cost		200	300
Cash paid in the measurement of operating lease liabilities		1,900	1,800
Reimbursements for development of lab space		$ 5,500
Reimbursements for development of lab space period		3 years
Reimbursements for development of lab space expiration year		2023
Additional grant for development of lab space	$ 1,000
Grant for development of lab space		$ 3,400
Defined contribution plan, maximum annual contributions per employee, percent		100.00%
Defined contribution plan, employer matching contribution, percent of employee's gross pay		3.00%
Defined contribution plan, employer discretionary contribution amount		$ 700	600
Research and development		$ 103,393	$ 92,889
Chestnut Run Lease
Other Commitments [Line Items]
Lease renewal period			5 years
Operating lease estimated incremental borrowing rate percent		15.00%
Area of lease premises \| ft²		81,000
Initial term of lease		162 months
Number of lease extensions \| Extension		3
Prepaid rent		$ 13,900
Right-of-use asset		30,600
Lease liability		16,700
Chestnut Run Lease \| Letter of Credit \| Pro Forma
Other Commitments [Line Items]
Security deposit		500
Chestnut Run Lease \| Letter of Credit \| Silicon Valley Bank
Other Commitments [Line Items]
Security deposit		$ 4,000	$ 4,000

Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 10,891	$ 8,227
Less accumulated depreciation	(3,566)	(3,319)
Property and equipment, net	7,325	4,908
Lab equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,643	5,588
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,582	875
IT equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	470	40
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,858	87
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 338	$ 1,637

Marketable Securities - Additional Information (Details) $ in Millions	Dec. 31, 2023 USD ($) Security
Investments, Debt and Equity Securities [Abstract]
Number of marketable securities \| Security	19
Securities fair market value unrealized loss position \| $	$ 75.6

Stock-Based Compensation - Schedule of Fair Value of Each Option Estimated on Date of Grant Using Weighted Average Assumptions (Details) - Stock Options	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	83.57%	84.67%
Risk-free interest rate	3.82%	2.73%
Expected life (in years)	6 years 7 days	6 years 10 days

- Definition

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

+ References

+ Details