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Stock-Based Compensation - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 2,022	$ 1,348
Research and development
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	745	600
General and administrative
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 1,277	$ 748

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Property, Plant and Equipment [Abstract]
Depreciation expenses	$ 0.4	$ 0.2

Fair Value Measurements - Summary of Fair Value of Financial Assets Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	$ 166,334	$ 106,010
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	166,334	106,010
US Treasury-Backed Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	118,978	64,397
US Treasury-Backed Money Market Funds \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	118,978	64,397
U.S. Treasury Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	5,987	11,980
Marketable Securities	41,369	29,633
U.S. Treasury Notes \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	5,987	11,980
Marketable Securities	$ 41,369	$ 29,633

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (18,020)	$ (16,319)

- Definition

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

+ References

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+ Details

Insider Trading Arrangements - shares	3 Months Ended
Insider Trading Arrangements - shares	Mar. 31, 2024	Feb. 08, 2024
Dr. James McArthur
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	true
Rule 10b5-1 Arrangement Terminated	true
Dr. Michelle Mellion
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	true
Dr. Niels Svenstrup
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	true
Rule10B51Trading Plan \| Dr. James McArthur
Trading Arrangements, by Individual
Name	Dr. James McArthur
Title	President and Chief Executive Officer
Adoption Date	December 8, 2022
Termination Date	February 8, 2024
Aggregate Available	125,000	31,250
TrdArr Expiration Date	May 15, 2024
Rule10B51Trading Plan \| Dr. Michelle Mellion
Trading Arrangements, by Individual
Name	Dr. Michelle Mellion
Title	Senior Vice President
Adoption Date	January 19, 2024
Aggregate Available	118,984
TrdArr Expiration Date	June 16, 2025
Rule10B51Trading Plan \| Dr. Niels Svenstrup
Trading Arrangements, by Individual
Name	Dr. Niels Svenstrup
Title	Senior Vice President
Adoption Date	January 23, 2024
Aggregate Available	42,000
TrdArr Expiration Date	December 15, 2025

Nature of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands					3 Months Ended
	Feb. 09, 2024	Feb. 05, 2024	Aug. 08, 2023	Jun. 16, 2023	Mar. 31, 2024	Feb. 06, 2024	Dec. 31, 2023
Subsidiary, Sale of Stock [Line Items]
Cash, cash equivalents and marketable securities					$ 175,200
Common stock issued in connection with exercise of stock options					36,204
Accumulated deficit					$ 199,502		$ 181,482
Net proceeds issuance or sale of equity				$ 300,000
Issuance and sale of shares of common stock					9,900
IPO
Subsidiary, Sale of Stock [Line Items]
Underwriter's fees and offering costs					$ 3,730
IPO \| Common stock
Subsidiary, Sale of Stock [Line Items]
Number of shares sold					7,530,000
Follow-on Offering
Subsidiary, Sale of Stock [Line Items]
Underwriter's fees and offering costs	$ 3,700
Public offering price per share						$ 10.635
Net proceeds issuance or sale of equity	$ 76,400
Follow-on Offering \| Common stock
Subsidiary, Sale of Stock [Line Items]
Number of shares sold	7,530,000
Shares Sales agreement and Follow-on Offering
Subsidiary, Sale of Stock [Line Items]
Net proceeds issuance or sale of equity	$ 86,300
Shares sales agreement
Subsidiary, Sale of Stock [Line Items]
Public offering price per share		$ 10
Net proceeds issuance or sale of equity		$ 9,900
Shares sales agreement \| Common stock
Subsidiary, Sale of Stock [Line Items]
Number of shares sold		1,000,000
At-the-Market Equity Offering Sales Agreement \| Stifel, Nicolaus & Company
Subsidiary, Sale of Stock [Line Items]
Issuance and sale of shares of common stock			$ 100,000
Commission to sales agent for gross proceeds from sales			3.00%

Property and Equipment, Net

3 Months Ended

Mar. 31, 2024

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

4. Property and Equipment, Net

The cost and accumulated depreciation of property and equipment were as follows (in thousands):


	March 31, 2024			December 31, 2023
Lab equipment	$	4,874		$	4,821
Computer and office equipment		1,506			1,446
Construction in process		1			69
Total property and equipment		6,381			6,336
Less: accumulated depreciation		(1,941	)		(1,572	)
Total property and equipment, net	$	4,440		$	4,764

Depreciation expense was $0.4 million and $0.2 million for the three months ended March 31, 2024 and March 31, 2023, respectively.

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Accrued Liabilities, Current [Abstract]
Research and development expenses	$ 4,049	$ 9,521
Employee-related expenses	1,114	2,368
Professional services	637	715
Other	952	918
Total accrued expenses	$ 6,752	$ 13,522

Accrued Expenses

3 Months Ended

Mar. 31, 2024

Accrued Liabilities, Current [Abstract]

Accrued Expenses

5. Accrued Expenses

Accrued expenses consisted of the following (in thousands):


	March 31, 2024		December 31, 2023
Research and development expenses	$	4,049	$	9,521
Employee-related expenses		1,114		2,368
Professional Services		637		715
Other		952		918
Total accrued expenses	$	6,752	$	13,522

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY(UNAUDITED) (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Public Offering
Net of issuance costs	$ 3,730
ATM
Net of issuance costs	$ 100

Related Party Transactions

3 Months Ended

Mar. 31, 2024

Related Party Transactions

6. Related Party Transactions

Technology License Agreement with Oxford University Innovation Limited

In March 2018, the Company, Oxford University Innovation Limited, or OUI, and the Medical Research Council of United Kingdom Research and Innovation, or MRC, or collectively, the Licensors, entered into a license of technology agreement, which was subsequently amended in December 2018, further amended and restated in November 2020, and further amended in February 2022, or the License Agreement. The Licensors and affiliates held shares of Series A-1 and Series A-2 preferred stock, Series B preferred stock and Class A common stock. The License Agreement provides the Company with an exclusive world-wide license to licensed data and technology owned by OUI and MRC in respect of cell-penetrating peptides for the treatment of Duchenne muscular dystrophy, spinal muscular atrophy, and other conditions. The License Agreement provides the Company with the rights to grant and authorize sublicenses to make, use, sell, and import products and otherwise exploit the patent rights.

As consideration for the license, the Company made an initial upfront payment in 2018, as well as a Restatement Completion Fee and a License Data Fee in 2020 totaling $0.1 million.

The Company could be required to make milestone payments to the Licensors upon achievement of certain patent and commercial milestones related to the patents and commercialization of certain of the Company’s product candidates. The aggregate potential milestone payments are $0.1 million. The Company also agreed to pay the Licensors low single digit royalties on net sales of any licensed products that are commercialized by the Company in excess of a threshold amount between £20 million and £30 million ($25.2 million and $37.9 million as of March 31, 2024), subject to certain adjustments. The term of the License Agreement continues until the later of (i) the date on which all the patents and patent applications covered thereunder have been abandoned or allowed to lapse or expired or been rejected or revoked or (ii) 20 years from the date of the original license agreement.

Upon completion of the IPO, the Company became obligated to pay OUI an exit fee between 0.5% to 2% of the value determined in an acquisition or initial public offering, not to exceed £5 million ($6.2 million as of the IPO date). The exit fee due to OUI, based on the proceeds of the IPO, was $1.4 million, which was paid during the second quarter of 2022 and included in research and development expense on the condensed consolidated statement of operations. One member of the Company’s board of directors is also employed by Oxford Science Enterprises, or OSE, which is an affiliate by OUI.

OSE is related to OUI and as of March 31, 2024 owned 14.7% of the Company’s outstanding common stock. One member of the Company’s board of directors, Dr. Christopher Ashton, is affiliated with OSE. Pursuant to the terms of Dr. Ashton's employment agreement with OSE, he is obligated to transfer any cash compensation from the Company to OSE. Fees paid in cash for Dr. Ashton's service on the Company's board of directors were paid directly to OSE. The Company paid $11,875 during the three months ended March 31, 2024 and 2023 to OSE as compensation for Dr. Ashton's service on the board of directors.

RA Capital Management, L.P.

Entities affiliated with RA Capital Management, L.P., or RA Capital, purchased common stock in the Company’s IPO in May 2022 and the Company’s Follow-on Offering in February 2024. As of March 31, 2024, entities affiliated with RA Capital owned 33.0% of the Company’s outstanding common stock.

Two members of the Company’s board of directors, Dr. Joshua Resnick and Habib Dable, are affiliated with RA Capital. Pursuant to the governing legal documents of RA Capital, Dr. Resnick is obligated to transfer any cash compensation from the Company to RA Capital. Fees paid in cash for Dr. Resnick's service on the Company's board of directors were paid directly to RA Capital. The Company paid $10,750 during the three months ended March 31, 2024 and 2023 to RA Capital for Dr. Resnick’s service on the board of directors.

- Definition

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

+ References

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+ Details

Stockholders' Equity - Schedule of Reserved Shares of Common Stock for Issuance, on an As-Converted Basis (Details) - shares	Mar. 31, 2024	Dec. 31, 2023
Class of Stock [Line Items]
Reserved shares of common stock for issuance	6,933,886	5,540,696
Stock Options Issued and Outstanding
Class of Stock [Line Items]
Reserved shares of common stock for issuance	5,284,400	4,233,203
Unvested Restricted Stock and Performance Stock Units
Class of Stock [Line Items]
Reserved shares of common stock for issuance	106,200
Authorized for Future Stock Awards or Option Grants
Class of Stock [Line Items]
Reserved shares of common stock for issuance	1,088,748	1,091,187
Authorized for Future Issuance under Employee Stock Purchase Plan
Class of Stock [Line Items]
Reserved shares of common stock for issuance	454,538	216,306

- Definition

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

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Reference 1: http://www.xbrl.org/2003/role/exampleRef
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+ Details

Nature of Business and Basis of Presentation

3 Months Ended

Mar. 31, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Nature of Business and Basis of Presentation

1. Nature of Business and Basis of Presentation

PepGen Inc., hereinafter referred to as PepGen or the Company, is a clinical-stage biotechnology company advancing the next generation of oligonucleotide therapeutics with the goal of transforming the treatment of severe neuromuscular and neurologic diseases. The Company's principal offices are located in Boston, Massachusetts.

The Company was initially formed as PepGen Limited on January 25, 2018, in the United Kingdom, or the U.K. On November 9, 2020, PepGen Limited completed a corporate reorganization, or the Reorganization. As part of the Reorganization, PepGen Limited formed PepGen Inc., a Delaware corporation with nominal assets and liabilities, for the purpose of consummating the Reorganization. In connection with the Reorganization, the existing stockholders of PepGen Limited exchanged each of its classes of shares of PepGen Limited for the same number and class of common stock of PepGen Inc. on a one-to-one basis. The newly issued stock of PepGen Inc. had substantially identical rights to the exchanged shares of PepGen Limited. As a result of the exchange, PepGen Inc. became the sole stockholder of PepGen Limited. Upon the completion of the Reorganization on November 23, 2020, the historical financial statements of PepGen Limited became the historical financial statements of PepGen Inc. as the Reorganization was deemed to be between entities under common control.

Liquidity and Capital Resources

Since inception, the Company has not generated any revenue from product sales or other sources and has incurred significant operating losses and negative cash flows from operations. The Company’s primary uses of cash and cash equivalents to date have been to fund research and development activities, business planning, establishing and maintaining the Company’s intellectual property portfolio, hiring personnel, leasing premises and associated capital expenditures, raising capital, and providing general and administrative support for these operations. As of March 31, 2024, the Company had an accumulated deficit of $199.5 million. To date, the Company has funded operations primarily through private placements of convertible preferred stock, the sale of shares of common stock in its initial public offering, or IPO, the sale of shares of common stock under its At-the-Market Equity Offering Sales Agreement, or Sales Agreement, with Stifel, Nicolaus & Company, Incorporated, or Stifel, and through the sale of shares of common stock in a follow-on offering, referred to as the Follow-on Offering. As of March 31, 2024, the Company had cash, cash equivalents, and marketable securities of $175.2 million. The Company believes that its cash, cash equivalents, and marketable securities as of March 31, 2024, will be sufficient to fund its currently planned operations for at least the next 12 months from the filing of these condensed consolidated financial statements.

The Company filed a shelf registration statement on Form S-3 with the United States Securities and Exchange Commission, or SEC, which covers the offering, issuance and sale of an amount up to $300.0 million in the aggregate of shares of common stock, preferred stock, debt securities, warrants, and/or units or any combination thereof, which was declared effective on June 16, 2023. On August 8, 2023, the Company filed a prospectus supplement and entered into the Sales Agreement with Stifel, as sales agent, which provides for the issuance and sale by the Company of up to $100.0 million of shares of common stock from time to time in “at-the-market” offerings. The sales agent is entitled to receive a commission of up to 3.0% of gross proceeds from sales under the Sales Agreement. On February 5, 2024, the Company sold 1,000,000 shares of common stock at a price of $10.00 per share under the Sales Agreement, resulting in net proceeds of $9.9 million. On February 9, 2024, the Company sold 7,530,000 shares of common stock in the Follow-on Offering, pursuant to an underwriting agreement with Leerink Partners LLC dated as of February 6, 2024, at a price of $10.635 per share resulting in net proceeds of $76.4 million after deducting underwriting fees and offering costs of $3.7 million. Net proceeds from sales under the Sales Agreement and Follow-on Offering, after deducting underwriters' fees and costs, were $86.3 million.

As the Company continues to pursue its business plan to successfully develop and obtain regulatory approval for the Company’s product candidates, it expects to finance its operations through the sale of equity, debt financings or other capital resources, which could include income from collaborations, strategic partnerships or marketing, distribution, licensing or other strategic arrangements with third parties, or from grants. However, there can be no assurance that any additional financing or strategic transactions will be available to the Company on acceptable terms, if at all. If events or circumstances occur such that the Company does not obtain additional funding, it may need to delay, reduce or eliminate its product development or future commercialization efforts, which could have a material adverse effect on the Company’s business, results of operations or financial condition.

Basis of Presentation and Consolidation

The accompanying condensed consolidated financial statements are unaudited and have been prepared in conformity with generally accepted accounting principles in the United States of America, or GAAP. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification and Accounting Standards Update of the Financial Accounting Standards Board. The condensed consolidated financial statements have been prepared on the same basis as the audited annual financial statements. Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. These condensed consolidated financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position as of March 31, 2024, and results of operations for the interim periods ended March 31, 2024 and March 31, 2023.

The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full year. These condensed consolidated financial statements should be read in conjunction with the audited financial statements as of and for the years ended December 31, 2023 and 2022, and the notes thereto, included in the Company’s Annual Report on Form 10-K, filed with the SEC on March 6, 2024, or Form 10-K, as amended by the Form 10-K/A filed on March 29, 2024.

Income Taxes - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 01, 2022	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2022
Income Taxes [Line Items]
Income tax expense
Uncertain tax position		$ 0.7
Expected market return	40.00%
Her Majesty's Revenue and Customs \| Accrued Expenses
Income Taxes [Line Items]
Income tax liabilities				$ 4.4
Uncertain tax position				$ 0.7

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2024

Share-Based Payment Arrangement [Abstract]

Summary of Stock Options Activity

Stock option activity under the 2020 Plan and the 2022 Plan, is as follows:


	Stock Options			Weighted-Average Exercise Price
Outstanding as of December 31, 2023		4,233,203		$	10.83
Granted		1,316,400			15.69
Exercised		(36,204	)		10.92
Canceled/Forfeited		(228,999	)		13.06
Outstanding as of March 31, 2024		5,284,400		$	11.94

Summary of Restricted Stock Units

A summary of the Company’s RSU and PSU activity and related information for the three months ended March 31, 2024 is as follows:


	Time-based RSUs		PSUs		Weighted-Average Grant Date Fair Value
Outstanding as of December 31, 2023		—		—	$	—
Granted		77,645		28,555		10.64
Vested		—		—		—
Forfeited		—		—		—
Issued and unvested as of March 31, 2024		77,645		28,555	$	10.64

Summary of Stock-based Compensation Expense

Stock-based compensation expense associated with stock options, RSUs, PSUs, and the Company’s ESPP included in the accompanying condensed consolidated statements of operations and comprehensive loss is as follows (in thousands):


	Three Months Ended March 31,
	2024		2023
Research and development	$	745	$	600
General and administrative		1,277		748
Total stock-based compensation expense	$	2,022	$	1,348

Property and Equipment, Net (Tables)

3 Months Ended

Mar. 31, 2024

Property, Plant and Equipment [Abstract]

Summary of Cost and Accumulated Depreciation of Property and Equipment

The cost and accumulated depreciation of property and equipment were as follows (in thousands):


	March 31, 2024			December 31, 2023
Lab equipment	$	4,874		$	4,821
Computer and office equipment		1,506			1,446
Construction in process		1			69
Total property and equipment		6,381			6,336
Less: accumulated depreciation		(1,941	)		(1,572	)
Total property and equipment, net	$	4,440		$	4,764

Stockholders' Equity - Additional Information (Details)	3 Months Ended
Stockholders' Equity - Additional Information (Details)	Mar. 31, 2024 USD ($) Vote $ / shares shares	Mar. 31, 2023 USD ($)
Class of Stock [Line Items]
Common stock, shares authorized \| shares	500,000,000
Common stock, par value \| $ / shares	$ 0.0001
Cash dividend \| $	$ 0	$ 0
Number of Common Stock Vote \| Vote	1
Undesignated Preferred Stock
Class of Stock [Line Items]
Preferred stock authorized \| shares	10,000,000
Preferred stock par value \| $ / shares	$ 0.0001

- 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 Measurements

3 Months Ended

Mar. 31, 2024

Fair Value Disclosures [Abstract]

Fair Value Measurements

3. Fair Value Measurements

The following tables present information about the Company’s financial assets that have been measured at fair value as of March 31, 2024 and December 31, 2023, and indicate the fair value of the hierarchy of the valuation inputs utilized to determine such fair value. In general, fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair value determined by Level 2 inputs utilize observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted market prices in markets that are not active or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities. Fair values determined by Level 3 inputs are unobservable data points for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. The following tables set forth marketable securities as of March 31, 2024 and December 31, 2023 (in thousands):


	As of March 31, 2024
	Amortized Cost		Unrealized Gains		Unrealized Losses			Total
U.S. Treasury notes		41,389		—		(20	)		41,369
Total	$	41,389	$	—	$	(20	)	$	41,369


	As of December 31, 2023
	Amortized Cost		Unrealized Gains		Unrealized Losses		Total
U.S. Treasury notes		29,622		11		—		29,633
Total	$	29,622	$	11	$	—	$	29,633

The following tables set forth the fair value of the Company’s financial assets measured at fair value on a recurring basis and indicate the level within the fair value hierarchy utilized to determine such values (in thousands):


	As of March 31, 2024
	Total		Level 1		Level 2		Level 3
Cash Equivalents:
U.S. Treasury-backed money market funds	$	118,978	$	118,978	$	—	$	—
U.S. Treasury notes		5,987		5,987		—		—
Marketable Securities
U.S. Treasury notes		41,369		41,369		—		—
Total	$	166,334	$	166,334	$	—	$	—


	As of December 31, 2023
	Total		Level 1		Level 2		Level 3
Cash Equivalents:
U.S. Treasury-backed money market funds	$	64,397	$	64,397	$	—	$	—
U.S. Treasury notes		11,980		11,980		—		—
Marketable Securities:
U.S. Treasury notes		29,633		29,633		—		—
Total	$	106,010	$	106,010	$	—	$	—

Money market funds are highly liquid investments that are valued based on quoted market prices in active markets, which represent a Level 1 measurement within the fair value hierarchy. These money market funds are classified on the balance sheet under cash and cash equivalents.

- 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

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net loss	$ (18,020)	$ (16,319)
Cumulative translation adjustment arising during the period	(51)	53
Unrealized loss on marketable securities	(20)
Comprehensive loss	$ (18,091)	$ (16,266)

- Definition

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

+ References

+ Details

Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2024

Equity [Abstract]

Schedule of Reserved Shares of Common Stock for Issuance, on an As-Converted Basis

The Company has reserved shares of common stock for issuance, on an as-converted basis, as follows:


	March 31, 2024		December 31, 2023
Stock options issued and outstanding		5,284,400		4,233,203
Unvested restricted stock and performance stock units		106,200		—
Authorized for future stock awards or option grants		1,088,748		1,091,187
Authorized for future issuance under employee stock purchase plan		454,538		216,306
Total		6,933,886		5,540,696

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2024

Fair Value Disclosures [Abstract]

Summary of Marketable Securities

The following tables set forth marketable securities as of March 31, 2024 and December 31, 2023 (in thousands):


	As of March 31, 2024
	Amortized Cost		Unrealized Gains		Unrealized Losses			Total
U.S. Treasury notes		41,389		—		(20	)		41,369
Total	$	41,389	$	—	$	(20	)	$	41,369


	As of December 31, 2023
	Amortized Cost		Unrealized Gains		Unrealized Losses		Total
U.S. Treasury notes		29,622		11		—		29,633
Total	$	29,622	$	11	$	—	$	29,633

Summary of Fair Value of Financial Assets Measured at Fair Value on Recurring Basis


	As of March 31, 2024
	Total		Level 1		Level 2		Level 3
Cash Equivalents:
U.S. Treasury-backed money market funds	$	118,978	$	118,978	$	—	$	—
U.S. Treasury notes		5,987		5,987		—		—
Marketable Securities
U.S. Treasury notes		41,369		41,369		—		—
Total	$	166,334	$	166,334	$	—	$	—


	As of December 31, 2023
	Total		Level 1		Level 2		Level 3
Cash Equivalents:
U.S. Treasury-backed money market funds	$	64,397	$	64,397	$	—	$	—
U.S. Treasury notes		11,980		11,980		—		—
Marketable Securities:
U.S. Treasury notes		29,633		29,633		—		—
Total	$	106,010	$	106,010	$	—	$	—

Stock-Based Compensation - Summary of Stock Options Activity (Details)	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock Options Outstanding as of December 31, 2022 \| shares	4,233,203
Stock Options, Granted \| shares	1,316,400
Exercise of stock options, Shares \| shares	(36,204)
Stock Options, Canceled/Forfeited \| shares	(228,999)
Stock Options, Outstanding as of March 31, 2023 \| shares	5,284,400
Weighted Average Exercise Price, Outstanding as of December 31, 2021 \| $ / shares	$ 10.83
Weighted Average Exercise Price, Granted \| $ / shares	15.69
Weighted average exercise price, exercised \| $ / shares	10.92
Weighted average exercise price, canceled/forfeited \| $ / shares	13.06
Weighted Average Exercise Price, Outstanding as of March 31, 2022 \| $ / shares	$ 11.94

- 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
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-Name Accounting Standards Codification
-Section 35
-Paragraph 1D
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+ Details

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2024

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

The Company’s significant accounting policies are disclosed in the audited financial statements for the year ended December 31, 2023 included in the Form 10-K. Since the date of those financial statements, there have been no changes to the Company’s significant accounting policies.

Concentration of Credit Risk

Financial instruments, which potentially subject the Company to concentrations of credit risk, consist of cash and money market accounts. As of March 31, 2024, the Company’s cash and money market accounts were held by three financial institutions in the United States, or U.S., and one financial institution in the United Kingdom, or U.K. At times, the Company’s deposits held in the U.S. and U.K. may exceed the respective insured limits of the Federal Depository Insurance Corporation and Financial Services Compensation Scheme.

Deferred Offering Costs

The Company capitalizes within other long-term assets certain legal, accounting, and other third-party fees that are directly related to the Company’s in-process equity financings, until such financings are consummated. After consummation of the equity financing, these costs are recorded as a reduction of the proceeds received as a result of the offering. Should a planned equity financing be abandoned, terminated, or significantly delayed, the deferred offering costs are immediately written off to operating expenses. As of March 31, 2024, deferred offering costs of $0.3 million were recorded within other assets on the condensed consolidated balance sheets related to the Company’s Registration Statement on Form S-3 filed with the SEC on June 2, 2023 and Prospectus Supplement filed on August 8, 2023.

Income Taxes

Income taxes are accounted for using the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts or existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using the 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 of enactment. The Company records a valuation allowance to reduce deferred tax assets to an amount for which realization is more likely than not.

The Company recognizes the tax benefit from an uncertain tax position if it is more likely than not that the tax position will be sustained upon examination by the tax authorities, based on the merits of the position. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to the unrecognized tax benefits.

Restricted Cash

The Company classifies all cash whose use is limited by contractual provisions as restricted cash. Restricted cash arises from the requirement for the Company to maintain cash of $1.5 million as collateral under a lease agreement. As of March 31, 2024 and December 31, 2023, the Company had $1.5 million of restricted cash classified in other assets on the condensed consolidated balance sheets.

Property and Equipment, Net - Summary of Cost and Accumulated Depreciation of Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 6,381	$ 6,336
Less: accumulated depreciation	(1,941)	(1,572)
Total property and equipment, net	4,440	4,764
Lab Equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	4,874	4,821
Computer and Office Equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	1,506	1,446
Construction in Process
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 1	$ 69

Income Taxes

3 Months Ended

Mar. 31, 2024

Income Tax Disclosure [Abstract]

Income Taxes

10. Income Taxes

The Company recorded income tax expense of nil for the three months ended March 31, 2024 and 2023.

On January 1, 2022, or the Transfer Date, the Company’s wholly owned subsidiary, PepGen Limited, transferred all intellectual property, or IP, assets to the parent company, PepGen Inc., in an arm’s length transaction at fair value pursuant to an asset transfer agreement. The fair value of the IP assets is a non-recurring fair value measurement. The Company engaged valuation specialists to calculate the IP value, and the IP value was measured using the historical cost method. The historical cost method estimated the fair value of the IP assets using the historical cost base of the IP assets and the expected market return as of the Transfer Date. The significant assumption inherent in estimating the fair value using the historical cost method was the expected market return. The Company utilized a 40% expected market return, which a third-party investor may expect as a return on their investment, and which is based on studies of venture capital investment returns. The Company calculated the fair value of the IP assets by computing the present value of the historical cost base using the 40% expected market return. The assumptions used in the estimation of the IP assets represent level 3 inputs of the fair value hierarchy.

The transfer of the IP assets resulted in an estimated tax charge during 2022 to His Majesty’s Revenue & Customs, or HMRC, after considering net operating loss carryforwards, of $4.4 million, inclusive of the $0.7 million uncertain tax position. The Company paid amounts owed to HMRC in September 2023.

The Company recognizes the impact of an uncertain income tax position taken on its income tax returns at the amount that is more likely than not to be sustained upon audit by the relevant taxing authority. An uncertain income tax position will be recognized if it has less than a 50% likelihood of being sustained. The tax positions are analyzed at least quarterly, and adjustments are made as events occur that warrant adjustments for those positions. As of March 31, 2024, the Company maintains the liability for the uncertain tax position related to the IP transfer of $0.7 million, which is accounted for in accrued expenses on the condensed consolidated balance sheet.

- 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
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 133,854	$ 80,774
Marketable securities	41,369	29,633
Prepaid expenses and other current assets	2,396	2,271
Total current assets	177,619	112,678
Property and equipment, net	4,440	4,764
Operating lease right-of-use asset	23,083	23,620
Other assets	1,858	1,990
Total assets	207,000	143,052
Current liabilities:
Accounts payable	1,480	1,005
Accrued expenses	6,752	13,522
Operating lease liability	3,026	3,004
Total current liabilities	11,258	17,531
Operating lease liability, net of current portion	16,743	17,100
Total liabilities	28,001	34,631
Commitments and contingencies (Note 7)
Stockholders' equity
Preferred stock
Common stock	3	2
Additional paid-in capital	378,535	289,867
Accumulated other comprehensive (loss) income	(37)	34
Accumulated deficit	(199,502)	(181,482)
Total stockholders' equity	178,999	108,421
Total liabilities and stockholders' equity	$ 207,000	$ 143,052

Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2024
Accounting Policies [Abstract]
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments, which potentially subject the Company to concentrations of credit risk, consist of cash and money market accounts. As of March 31, 2024, the Company’s cash and money market accounts were held by three financial institutions in the United States, or U.S., and one financial institution in the United Kingdom, or U.K. At times, the Company’s deposits held in the U.S. and U.K. may exceed the respective insured limits of the Federal Depository Insurance Corporation and Financial Services Compensation Scheme.
Deferred Offering Costs	Deferred Offering Costs The Company capitalizes within other long-term assets certain legal, accounting, and other third-party fees that are directly related to the Company’s in-process equity financings, until such financings are consummated. After consummation of the equity financing, these costs are recorded as a reduction of the proceeds received as a result of the offering. Should a planned equity financing be abandoned, terminated, or significantly delayed, the deferred offering costs are immediately written off to operating expenses. As of March 31, 2024, deferred offering costs of $0.3 million were recorded within other assets on the condensed consolidated balance sheets related to the Company’s Registration Statement on Form S-3 filed with the SEC on June 2, 2023 and Prospectus Supplement filed on August 8, 2023.
Income Taxes	Income Taxes Income taxes are accounted for using the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts or existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using the 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 of enactment. The Company records a valuation allowance to reduce deferred tax assets to an amount for which realization is more likely than not. The Company recognizes the tax benefit from an uncertain tax position if it is more likely than not that the tax position will be sustained upon examination by the tax authorities, based on the merits of the position. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to the unrecognized tax benefits.
Restricted Cash	Restricted Cash The Company classifies all cash whose use is limited by contractual provisions as restricted cash. Restricted cash arises from the requirement for the Company to maintain cash of $1.5 million as collateral under a lease agreement. As of March 31, 2024 and December 31, 2023, the Company had $1.5 million of restricted cash classified in other assets on the condensed consolidated balance sheets.

- Definition

Disclosure of accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.

+ References + Details

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Public Offering	ATM	Common Stock	Common Stock Public Offering	Common Stock ATM	Additional Paid-in Capital	Additional Paid-in Capital Public Offering	Additional Paid-in Capital ATM	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Beginning Balance at Dec. 31, 2022	$ 179,631			$ 2			$ 282,566			$ (81)	$ (102,856)
Beginning Balance, shares at Dec. 31, 2022				23,713,196
Exercise of stock options , Shares				68,709
Stock-based compensation expense	1,348						1,348
Exercise of Stock Options	130						130
Net loss	(16,319)										(16,319)
Cumulative translation adjustment arising during the period	53									53
Ending Balance at Mar. 31, 2023	164,843			$ 2			284,044			(28)	(119,175)
Ending Balance, shares at Mar. 31, 2023				23,781,905
Beginning Balance at Dec. 31, 2023	108,421			$ 2			289,867			34	(181,482)
Beginning Balance, shares at Dec. 31, 2023				23,823,241
Exercise of stock options , Shares				36,194
Stock-based compensation expense	2,022						2,022
Unrealized loss on marketable securities	(20)									(20)
Issuance of common stock		$ 76,352	$ 9,900		$ 1			$ 76,351	$ 9,900
Issuance of common stock, Shares					7,530,000	1,000,000
Exercise of Stock Options	395						395
Net loss	(18,020)										(18,020)
Cumulative translation adjustment arising during the period	(51)									(51)
Ending Balance at Mar. 31, 2024	$ 178,999			$ 3			$ 378,535			$ (37)	$ (199,502)
Ending Balance, shares at Mar. 31, 2024				32,389,435

Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2024	May 01, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001835597
Entity Registrant Name	PEPGEN INC.
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		32,417,181
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Title of 12(b) Security	Common stock, par value $0.0001 per share
Trading Symbol	PEPG
Security Exchange Name	NASDAQ
Entity File Number	001-41374
Entity Tax Identification Number	85-3819886
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	321 Harrison Ave. 8th Floor
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02118
City Area Code	781
Local Phone Number	797-0979
Document Quarterly Report	true
Document Transition Report	false

Fair Value Measurements - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Option, Quantitative Disclosures [Line Items]
Amortized Cost	$ 41,389	$ 29,622
Unrealized Gains		11
Unrealized Losses	(20)
Total	41,369	29,633
US Treasury-Backed Money Market Funds
Fair Value, Option, Quantitative Disclosures [Line Items]
Amortized Cost	41,389	29,622
Unrealized Gains		11
Unrealized Losses	(20)
Total	$ 41,369	$ 29,633

Stock-Based Compensation

3 Months Ended

Mar. 31, 2024

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

9. Stock-Based Compensation

The Company maintains three equity compensation plans; the 2020 Stock Plan, or the 2020 Plan, the 2022 Stock Option and Incentive Plan, or the 2022 Plan, and the 2022 Employee Stock Purchase Plan, or the ESPP. As of the Company's IPO in May 2022, the Company's board of directors determined that no further awards would be made under the 2020 Plan. The number of shares of common stock that may be issued under the 2022 Plan is subject to increase by the number of shares under any outstanding stock options forfeited and not exercised under the 2020 Plan. Additionally, the number of shares reserved for issuance under the 2022 Plan automatically increases on the first day of each fiscal year in an amount equal to the lower of (1) 5% of the shares of common stock outstanding on such date and (2) an amount determined by the Company’s board of directors. The 2022 Plan allows the board of directors to grant incentive stock options, non-qualified stock options, stock appreciation rights, restricted stock awards, restricted stock units, unrestricted stock awards, cash-based awards, and dividend equivalent rights to the Company’s officers, employees, directors and other key persons. As of March 31, 2024, 1,088,748 shares remained available for grant under the 2022 Plan and 454,538 shares remained available for issuance under the ESPP.

Stock Option Activity

Stock option activity under the 2020 Plan and the 2022 Plan, is as follows:


	Stock Options			Weighted-Average Exercise Price
Outstanding as of December 31, 2023		4,233,203		$	10.83
Granted		1,316,400			15.69
Exercised		(36,204	)		10.92
Canceled/Forfeited		(228,999	)		13.06
Outstanding as of March 31, 2024		5,284,400		$	11.94

The weighted-average grant date fair value of options granted during the three months ended March 31, 2024 was $11.25 per share. The Company had 5,284,400 unvested stock options outstanding as of March 31, 2024. As of March 31, 2024, total unrecognized compensation cost related to stock options was $32.6 million. This amount is expected to be recognized over a weighted average period of approximately 2.84 years.

Restricted Stock Units

A restricted stock unit, or RSU, represents the right to receive one share of common stock upon vesting of the RSU. In February 2024, the Company granted employees a one-time RSU award that vests fully on the one-year anniversary of the grant date, provided that the employee remains employed with the Company. Certain employees, including employees who are executive officers of the Company, received a one-time RSU award that vests upon the achievement of certain performance-based clinical development milestones, or PSUs. Such awards cannot vest in less than one year, regardless of when the performance milestone is achieved. The Company’s chief executive officer did not receive any RSU or PSU awards. A summary of the Company’s RSU and PSU activity and related information for the three months ended March 31, 2024 is as follows:


	Time-based RSUs		PSUs		Weighted-Average Grant Date Fair Value
Outstanding as of December 31, 2023		—		—	$	—
Granted		77,645		28,555		10.64
Vested		—		—		—
Forfeited		—		—		—
Issued and unvested as of March 31, 2024		77,645		28,555	$	10.64

The weighted average grant date fair value of the time-based RSUs and PSUs granted during the three months ended March 31, 2024 was $10.64. As of March 31, 2024, there was $0.7 million of unrecognized compensation costs related to unvested time-based RSUs, which are expected to be recognized over a weighted-average period of 0.9 years and $0.3 million of unrecognized compensation costs related to unvested PSUs, dependent upon achievement of aforementioned clinical development milestones.

Stock-Based Compensation Expense


	Three Months Ended March 31,
	2024		2023
Research and development	$	745	$	600
General and administrative		1,277		748
Total stock-based compensation expense	$	2,022	$	1,348

Accrued Expenses (Tables)

3 Months Ended

Mar. 31, 2024

Accrued Liabilities, Current [Abstract]

Schedule of Accrued Expenses

Accrued expenses consisted of the following (in thousands):


	March 31, 2024		December 31, 2023
Research and development expenses	$	4,049	$	9,521
Employee-related expenses		1,114		2,368
Professional Services		637		715
Other		952		918
Total accrued expenses	$	6,752	$	13,522

Related Party Transactions - Additional Information (Details) £ in Millions			3 Months Ended
	May 31, 2022 GBP (£)	May 31, 2022 USD ($)	Mar. 31, 2024 GBP (£)	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Jun. 30, 2022 USD ($)
RA Capital Management, L.P
Related Party Transaction [Line Items]
Percentage of holding in outstanding common stock			33.00%	33.00%
Rent expense				$ 10,750	$ 10,750
Oxford University Innovation Limited
Related Party Transaction [Line Items]
Percentage of holding in outstanding common stock			14.70%	14.70%
Rent expense				$ 11,875	$ 11,875
Technology License Agreement
Related Party Transaction [Line Items]
Additional payments of restatement completion fee and license data fee				100,000
Aggregate potential milestone payments				$ 100,000
Term of license agreement			20 years	20 years
Technology License Agreement \| Minimum
Related Party Transaction [Line Items]
Sublicensees threshold amount			£ 20	$ 37,900,000
Technology License Agreement \| Maximum
Related Party Transaction [Line Items]
Sublicensees threshold amount			£ 30	$ 25,200,000
Technology License Agreement \| Oxford University Innovation Limited \| IPO
Related Party Transaction [Line Items]
Required to pay exit fee amount						$ 1,400,000
Technology License Agreement \| Oxford University Innovation Limited \| Minimum \| IPO
Related Party Transaction [Line Items]
Percentage of exit fee	0.50%	0.50%
Technology License Agreement \| Oxford University Innovation Limited \| Maximum \| IPO
Related Party Transaction [Line Items]
Percentage of exit fee	2.00%	2.00%
Required to pay exit fee amount	£ 5	$ 6,200,000

Summary of Significant Accounting Policies - Additional Information) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Summary of Significant Accounting Policies [Line Items]
Deferred offering costs	$ 300,000
Cash	1,500,000
Restricted cash	$ 1,500,000	$ 1,500,000
Restricted Cash, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other Assets, Noncurrent	Other Assets, Noncurrent
Unrecognized tax benefits, interest on income taxes expense	$ 0
Unrecognized tax benefits, income tax penalties	$ 0

- Definition

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

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-URI https://asc.fasb.org//1943274/2147480424/946-10-50-3

+ Details

Stockholders' Equity

3 Months Ended

Mar. 31, 2024

Equity [Abstract]

Stockholders' Equity

8. Stockholders’ Equity

Under the Third Amended and Restated Certificate of Incorporation, dated May 10, 2022, as currently in effect, the Company has the authority to issue a total of 500,000,000 shares of common stock (par value of $0.0001 per share) and 10,000,000 shares of undesignated preferred stock (par value of $0.0001 per share). In connection with the IPO, the Company re-designated all shares of Class A common stock as shares of common stock. Each share of common stock has the right to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when declared by the board of directors, subject to the prior rights of holders of all classes of stock outstanding having priority rights as to dividends. No cash dividends were declared by the board of directors during the three months ended March 31, 2024 and March 31, 2023.

The Company has reserved shares of common stock for issuance, on an as-converted basis, as follows:


	March 31, 2024		December 31, 2023
Stock options issued and outstanding		5,284,400		4,233,203
Unvested restricted stock and performance stock units		106,200		—
Authorized for future stock awards or option grants		1,088,748		1,091,187
Authorized for future issuance under employee stock purchase plan		454,538		216,306
Total		6,933,886		5,540,696

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Section 50
-Paragraph 13
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Stock-Based Compensation - Additional Information (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($) $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Outstanding unvested stock options	$ 5,284,400
Expected recognition period of unrecognized compensation cost related to unvested share options	2 years 10 months 2 days
Unrecognized compensation cost related to unvested share options	$ 32,600
Employee Stock Option
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Weighted average grant date fair value of options granted \| $ / shares	$ 11.25
Time Based RSU
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Unrecognized compensation costs related to unvested RSUs	$ 700
Expected recognition period of unrecognized compensation cost related to unvested share options	10 months 24 days
PSUs
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Unrecognized compensation cost related to unvested share options	$ 300
Restricted Stock Units
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Weighted Average Grant Date Fair Value, Granted \| $ / shares	$ 10.64
2022 Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock outstanding percentage	5.00%
Shares remaining available for issuance \| shares	1,088,748
2022 Employee Stock Purchase Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of shares authorized and reserved for issuance \| shares	454,538

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating Expenses [Abstract]
Research and development	$ 14,732	$ 14,360
General and administrative	5,066	3,671
Total operating expenses	19,798	18,031
Operating loss	(19,798)	(18,031)
Other income (expense)
Interest income	1,735	1,792
Other income (expense), net	43	(80)
Total other income, net	1,778	1,712
Net loss before income tax	(18,020)	(16,319)
Net loss	$ (18,020)	$ (16,319)
Net loss per share, basic	$ (0.63)	$ (0.69)
Net loss per share, diluted	$ (0.63)	$ (0.69)
Weighted-average common stock outstanding, basic	28,656,401	23,761,915
Weighted-average common stock outstanding, diluted	28,656,401	23,761,915

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows from operating activities:
Net loss	$ (18,020)	$ (16,319)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation	376	150
Stock-based compensation expense	2,022	1,348
Amortization and interest accretion related to operating lease	(135)	37
Amortization of premium and discounts on marketable securities, net	(516)
Other non-cash adjustments	20
Changes in operating assets and liabilities:
Prepaids and other current and non-current assets	62	1,267
Accounts payable	88	(120)
Accrued expenses and other non-current liabilities	(6,765)	166
Operating lease liabilities, current and non-current	336	(1,951)
Net cash used in operating activities	(22,532)	(15,422)
Cash flows from investing activities:
Purchases of property and equipment	(53)	(1,181)
Purchases of marketable securities	(29,239)
Maturities of marketable securities	18,000
Net cash used in investing activities	(11,292)	(1,181)
Cash flows from financing activities:
Issuance of common stock in public offering, net of underwriters' fees	76,878
Payment of offering costs	(206)
Issuance of common stock from At-the-Market Sales Agreement, net of underwriters' fees	9,900
Proceeds from employee equity plans	395	130
Net cash provided by financing activities	86,967	130
Effect of exchange rate changes on cash	(63)	124
Net increase (decrease) in cash, cash equivalents and restricted cash	53,080	(16,349)
Cash, cash equivalents and restricted cash at beginning of period	82,322	183,225
Cash, cash equivalents and restricted cash at end of period	135,402	166,876
Components of cash, cash equivalents and restricted cash
Cash and cash equivalents	133,854	165,403
Restricted Cash	1,548	1,473
Total cash, cash equivalents and restricted cash at end of period	135,402	166,876
Supplemental noncash investing and financing activities
Property and equipment included in accounts payable and accrued expenses	19	$ 974
Deferred offering costs in accounts payable and accrued expenses	$ 188

Commitments and Contingencies

3 Months Ended

Mar. 31, 2024

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

7. Commitments and Contingencies

Legal proceedings

From time to time, the Company may have certain contingent liabilities that arise in the ordinary course of its business activities. The Company accrues a liability for such matters when it is probable that future expenditures will be made and that such expenditures can be reasonably estimated.

The Company is not party to any litigation and does not have contingency reserves established for any litigation liabilities.

Other

The Company enters into standard indemnification agreements in the ordinary course of business. Pursuant to the agreements, the Company agrees to indemnify, hold harmless, and to reimburse the indemnified party for losses suffered or incurred by the indemnified party, including in connection with any U.S. patent or any copyright or other intellectual property infringement claim by any third-party with respect to the Company’s products. Further, the Company indemnifies its directors and officers who are, or were, serving at the Company’s request in such capacities. The Company’s maximum exposure under these arrangements is unknown as of March 31, 2024. The Company does not anticipate recognizing any significant losses relating to these arrangements. The term of these indemnification agreements is generally perpetual any time after execution of the agreement. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements may be unlimited. The Company has never incurred costs to defend lawsuits or settle claims related to these indemnification agreements.

Stock-Based Compensation - Summaey of Restricted Stock Units (Details)	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Restricted Stock Units
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Weighted Average Grant Date Fair Value, Granted \| $ / shares	$ 10.64
Weighted Average Grant Date Fair Value, Issued and unvested \| $ / shares	$ 10.64
Time Based RSU
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of Shares, Granted	77,645
Number of Shares, Issued and unvested	77,645
PSUs
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of Shares, Granted	28,555
Number of Shares, Issued and unvested	28,555

- 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