PepGen (PEPG) 10-Q 8 Aug 23 2023 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2023	Aug. 01, 2023
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q2
Entity Registrant Name	PEPGEN INC.
Entity Central Index Key	0001835597
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		23,813,547
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

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 147,027	$ 181,752
Prepaid expenses and other current assets	3,351	4,331
Total current assets	150,378	186,083
Property and equipment, net	5,251	3,335
Operating lease right-of-use asset	24,754	26,549
Other assets	1,702	1,473
Total assets	182,085	217,440
Current liabilities:
Accounts payable	1,815	1,362
Accrued expenses	11,629	11,913
Operating lease liability	3,492	5,553
Total current liabilities	16,936	18,828
Operating lease liability, net of current portion	17,865	18,981
Total liabilities	34,801	37,809
Commitments and contingencies (Note 8)
Convertible preferred stock
Stockholders' equity (deficit)
Common stock	2	2
Additional paid-in capital	285,966	282,566
Accumulated other comprehensive (loss) income	13	(81)
Accumulated deficit	(138,697)	(102,856)
Total stockholders' equity	147,284	179,631
Total liabilities, convertible preferred stock, and stockholders' equity	$ 182,085	$ 217,440

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Operating Expenses [Abstract]
Research and development	$ 16,926	$ 14,240	$ 31,286	$ 24,947
General and administrative	4,218	3,401	7,889	6,587
Total operating expenses	21,144	17,641	39,175	31,534
Operating loss	(21,144)	(17,641)	(39,175)	(31,534)
Other income (expense)
Interest income	1,684	250	3,476	259
Other income (expense), net	(62)	76	(142)	134
Total other income, net	1,622	326	3,334	393
Net loss before income tax	(19,522)	(17,315)	(35,841)	(31,141)
Income tax expense				(4,420)
Net loss	$ (19,522)	$ (17,315)	$ (35,841)	$ (35,561)
Net loss per share, basic	$ (0.82)	$ (1.23)	$ (1.51)	$ (4.7)
Net loss per share, diluted	$ (0.82)	$ (1.23)	$ (1.51)	$ (4.7)
Weighted-average common shares outstanding, basic	23,790,430	14,090,455	23,776,448	7,563,283
Weighted-average common shares outstanding, diluted	23,790,430	14,090,455	23,776,448	7,563,283

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Statement of Comprehensive Income [Abstract]
Net loss	$ (19,522)	$ (17,315)	$ (35,841)	$ (35,561)
Cumulative translation adjustment arising during the period	41	(42)	94	(116)
Comprehensive loss	$ (19,481)	$ (17,357)	$ (35,747)	$ (35,677)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' DEFICIT (UNAUDITED) - USD ($) $ in Thousands	Total	Series A-1 Convertible Preferred Stock	Series A-2 Convertible Preferred Stock	Series B Convertible Preferred Stock	Common Stock Class A Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Temporary Equity Beginning Balance at Dec. 31, 2021		$ 8,454	$ 44,639	$ 112,083
Temporary Equity Beginning Balance, shares at Dec. 31, 2021		1,372,970	3,939,069	7,234,766
Beginning Balance at Dec. 31, 2021	$ (32,082)					$ 1,653	$ 17	$ (33,752)
Beginning Balance, shares at Dec. 31, 2021					963,588
Stock-based compensation expense	815					815
Net loss	(18,246)							(18,246)
Foreign currency translation adjustment	(74)						(74)
Temporary Equity Ending Balance at Mar. 31, 2022		$ 8,454	$ 44,639	$ 112,083
Temporary Equity Ending Balance, shares at Mar. 31, 2022		1,372,970	3,939,069	7,234,766
Ending Balance at Mar. 31, 2022	(49,587)					2,468	(57)	(51,998)
Ending Balance, shares at Mar. 31, 2022					963,588
Temporary Equity Beginning Balance at Dec. 31, 2021		$ 8,454	$ 44,639	$ 112,083
Temporary Equity Beginning Balance, shares at Dec. 31, 2021		1,372,970	3,939,069	7,234,766
Beginning Balance at Dec. 31, 2021	(32,082)					1,653	17	(33,752)
Beginning Balance, shares at Dec. 31, 2021					963,588
Net loss	(35,561)
Ending Balance at Jun. 30, 2022	210,219				$ 2	279,629	(99)	(69,313)
Ending Balance, shares at Jun. 30, 2022					23,562,395
Temporary Equity Beginning Balance at Mar. 31, 2022		$ 8,454	$ 44,639	$ 112,083
Temporary Equity Beginning Balance, shares at Mar. 31, 2022		1,372,970	3,939,069	7,234,766
Beginning Balance at Mar. 31, 2022	(49,587)					2,468	(57)	(51,998)
Beginning Balance, shares at Mar. 31, 2022					963,588
Stock-based compensation expense	1,228					1,228
Temporary equity, Issuance of Series A-2 stock upon exercise of warrants, shares			35,529
Temporary equity, Issuance of Series A-2 stock upon exercise of warrants			$ 574
Temprory equity, Conversion of convertible preferred stock upon initial public offering		$ 8,454	$ 45,213	$ 112,083
Temprory equity,Conversion of convertible preferred stock upon initial public offering, shares		1,372,970	3,974,598	7,234,766
Conversion of convertible preferred stock upon initial public offering					12,359,856
Conversion of convertible preferred stock upon initial public offering	165,752				$ 1	165,751
Issuance of Common Stock upon initial public offering net of underwriters' fees and issuance costs	110,183				$ 1	110,182
Issuance of Common Stock upon initial public offering net of underwriters' fees and issuance costs, shares					10,238,951
Net loss	(17,315)							(17,315)
Foreign currency translation adjustment	(42)						(42)
Ending Balance at Jun. 30, 2022	210,219				$ 2	279,629	(99)	(69,313)
Ending Balance, shares at Jun. 30, 2022					23,562,395
Temporary Equity Beginning Balance at Dec. 31, 2022
Beginning Balance at Dec. 31, 2022	179,631				$ 2	282,566	(81)	(102,856)
Beginning Balance, shares at Dec. 31, 2022					23,713,196
Stock-based compensation expense	1,348					1,348
Exercise of Stock Options	130					130
Exercise of Stock Options, Shares					68,709
Net loss	(16,319)							(16,319)
Foreign currency translation adjustment	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
Temporary Equity Beginning Balance at Dec. 31, 2022
Beginning Balance at Dec. 31, 2022	179,631				$ 2	282,566	(81)	(102,856)
Beginning Balance, shares at Dec. 31, 2022					23,713,196
Net loss	(35,841)
Temporary Equity Ending Balance at Jun. 30, 2023
Ending Balance at Jun. 30, 2023	147,284				$ 2	285,966	13	(138,697)
Ending Balance, shares at Jun. 30, 2023					23,813,547
Beginning Balance at Mar. 31, 2023	164,843				$ 2	284,044	(28)	(119,175)
Beginning Balance, shares at Mar. 31, 2023					23,781,905
Stock-based compensation expense	1,837					1,837
Exercise of Stock Options	85					85
Exercise of Stock Options, Shares					31,642
Net loss	(19,522)							(19,522)
Foreign currency translation adjustment	41						41
Temporary Equity Ending Balance at Jun. 30, 2023
Ending Balance at Jun. 30, 2023	$ 147,284				$ 2	$ 285,966	$ 13	$ (138,697)
Ending Balance, shares at Jun. 30, 2023					23,813,547

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' DEFICIT (UNAUDITED) (Parenthetical) $ in Thousands	3 Months Ended
	Jun. 30, 2022 USD ($)
Common Stock
Net of issuance costs	$ 12,684

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Cash flows from operating activities:
Net loss	$ (35,841)	$ (35,561)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation	481	205
Stock-based compensation expense	3,185	2,043
Amortization and interest accretion related to operating leases	(117)
Change in fair value of preferred stock warrant liability		(58)
Changes in operating assets and liabilities:
Other receivables		26
Prepaids and other current and non-current assets	609	(926)
Accounts payable	302	1,434
Accrued expenses and other non-current liabilities	(451)	7,926
Operating lease liabilities, current and non-current	(1,265)
Net cash used in operating activities	(33,097)	(24,911)
Cash flows from investing activities:
Purchases of property and equipment	(2,190)	(2,223)
Net cash used in investing activities	(2,190)	(2,223)
Cash flows from financing activities:
Issuance of common stock upon initial public offering, net of underwriters' fees		114,267
Payment of offering costs	104	(1,277)
Proceeds from the exercise of Series A-2 warrants		406
Proceeds from employee equity plans	215
Net cash provided by financing activities	319	113,396
Effect of exchange rate changes on cash	318	(340)
Net (decrease) increase in cash, cash equivalents and restricted cash	(34,650)	85,922
Cash, cash equivalents and restricted cash at beginning of period	183,225	134,368
Cash, cash equivalents and restricted cash at end of period	148,575	220,290
Components of cash, cash equivalents and restricted cash
Cash and cash equivalents	147,027	218,817
Restricted Cash	1,548	1,473
Supplemental noncash investing and financing activities
Property and equipment included in accounts payable and accrued expenses	208	244
Deferred offering costs in accounts payable and accrued expenses	$ 42	$ 1,420

Nature of Business and Basis of

Nature of Business and Basis of Presentation	6 Months Ended
	Jun. 30, 2023
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., or the Company or PepGen, headquartered in Boston, Massachusetts, is a biopharmaceutical company developing a transformative oligonucleotide delivery technology and pipeline of product candidates to treat neuromuscular and neurologic diseases with a high unmet medical need. Initial Public Offering On May 10, 2022, the Company closed its initial public offering (IPO) in which the Company sold an aggregate of 9,000,000 shares at a public offering price of $ 12.00 per share for gross proceeds of $ 108.0 million. In connection with the IPO, the Company granted the underwriters a 30-day option to purchase 1,350,000 additional shares of common stock. On May 16, 2022, the underwriters exercised the option in part and the Company issued 1,238,951 shares of common stock for gross proceeds of $ 14.9 million. From the IPO and option exercise by the underwriters, the Company received approximately $ 122.9 million in gross proceeds and $ 110.2 million in net proceeds, after deducting underwriting discounts and offering expenses payable by the Company. Immediately prior to consummation of the IPO, all 12,546,805 outstanding shares of the Company’s redeemable convertible preferred stock, and 35,529 preferred stock warrants that were exercised on May 4, 2022 (see Note 3), converted into 12,359,856 shares of the Company’s common stock. As a result of this conversion, the Company's net loss per share for fiscal periods in 2022, basic and diluted, will be significantly different from later filings. 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 June 30, 2023, the Company had an accumulated deficit of $ 138.7 million. To date, the Company has funded operations primarily through private placements of convertible preferred stock and its IPO. As of June 30, 2023, the Company had cash and cash equivalents of $ 147.0 million. Based on its current operating plans, the Company believes that its cash and cash equivalents as of June 30, 2023, 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. 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 (GAAP). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (ASC) and Accounting Standards Update (ASU) of the Financial Accounting Standards Board (FASB). 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 June 30, 2023, and results of operations for the interim periods ended June 30, 2023 and June 30, 2022. 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, 2022 and 2021, and the notes thereto, included in the Company’s Annual Report, filed with the Securities and Exchange Commission (the SEC) on March 23, 2023, or Form 10-K.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies The Company’s significant accounting policies are disclosed in the audited financial statements for the year ended December 31, 2022 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 June 30, 2023, the Company’s cash and money market accounts were held by four financial institutions in the U.S. and one financial institution in the 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. Subsequent to the completion of the IPO in May 2022, deferred offering costs totaling $ 4.1 million were recorded within stockholders’ equity (deficit) as a reduction of additional paid-in-capital generated from the initial public offering. As of June 30, 2023, deferred offering costs of $ 0.2 million were recorded within other assets on the consolidated balance sheets related to the Company's Registration Statement on Form S-3 filed with the SEC on June 2, 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 June 30, 2023 and December 31, 2022, the Company had $ 1.5 million of restricted cash classified in other assets on the consolidated balance sheets.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The following tables (in thousands) present information about the Company’s financial assets that have been measured at fair value as of June 30, 2023 and December 31, 2022, 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. As of June 30, 2023 Total Level 1 Level 2 Level 3 US Treasury-backed money market funds $ 136,620 $ 136,620 $ — $ — Total $ 136,620 $ 136,620 $ — $ — As of December 31, 2022 Total Level 1 Level 2 Level 3 US Treasury-backed money market funds $ 18,645 $ 18,645 $ — $ — Total $ 18,645 $ 18,645 $ — $ — 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. Preferred stock warrant liability In connection with the November 24, 2020 Stock Purchase Agreement (Note 8), the Company granted warrants to purchase up to 35,529 shares of Series A-2 convertible preferred stock at a price per share equal to $ 11.42 and with a term ending upon the earlier of an underwritten public offering pursuant to an effective registration statement under the Securities Act of 1933, the consummation of a Deemed Liquidation Event, as such term is defined in the Company’s Restated Certificate of Incorporation or 10 years . As the warrants are for preferred stock, which do not qualify for equity classification, the warrants were recorded as a liability and were required to be remeasured to fair value at each reporting date. The warrants were exercised on May 4, 2022 , just prior to the completion of the IPO, for proceeds of $ 0.4 million. Immediately prior to the consummation of the IPO, the warrants were converted into 34,901 shares of the Company's common stock. As there are a number of inputs that are not observable in the market, the warrant valuation represented a Level 3 measurement within the fair value hierarchy. The Company’s valuation of the preferred stock warrant utilized the Black-Scholes option-pricing model, which incorporates assumptions and estimates to value the preferred stock warrant. The quantitative elements associated with the Company’s Level 3 inputs impacting the fair value measurement of the preferred stock warrant liability included the fair value per share of the underlying Series A-2 convertible preferred stock, the remaining contractual term of the warrant, risk-free interest rate, expected dividend yield and expected volatility of the price of the underlying preferred stock. The most significant assumption in the Black-Scholes option-pricing model impacting the fair value of the preferred stock warrant was the fair value of the Company’s Series A-2 convertible preferred stock as of each remeasurement date. The Company determined the fair value per share of the underlying preferred stock by taking into consideration its most recent sales of its convertible preferred stock. The Company historically had been a private company and lacked company-specific historical and implied volatility information of its stock. Therefore, it estimated its expected stock volatility based on the historical volatility of publicly traded peer companies for a term equal to the remaining contractual term of the warrant. The risk-free interest rate was determined by reference to the U.S. Treasury yield curve for time periods approximately equal to the remaining contractual term of the warrant. The Company had estimated a 0 % dividend yield based on the expected dividend yield and the fact that the Company has never paid or declared dividends. The Company recognized changes in the fair value of the warrant liability as a component of other income (expense) in its consolidated statements of operations and comprehensive loss. A reconciliation of the Level 3 warrant liability through exercise in the second quarter of 2022 is as follows (in thousands): Series A-2 Preferred Balance as of December 31, 2020 $ 30 Change in fair value 196 Balance as of December 31, 2021 226 Change in fair value ( 58 ) Balance as of March 31, 2022 168 Exercise of preferred stock warrants ( 168 ) Balance as of June 30, 2022 $ — Immediately prior to consummation of the IPO, all 35,529 preferred stock warrants that were exercised on May 4, 2022, converted into 34,901 shares of the Company’s common stock. As such, there is no activity during the three- or six-months ended June 30, 2023.

Property and Equipment, Net

Property and Equipment, Net	6 Months Ended
	Jun. 30, 2023
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): June 30, December 31, Lab equipment $ 4,810 $ 2,424 Computer and office equipment 1,158 171 Construction in process 154 1,129 Total property and equipment 6,122 3,724 Less: accumulated depreciation ( 871 ) ( 389 ) Total property and equipment, net $ 5,251 $ 3,335 Depreciation expense was $ 0.3 million and $ 0.1 million for the three months ended June 30, 2023 and June 30, 2022, respectively. Depreciation expense was $ 0.5 million and $ 0.2 million for the six months ended June 30, 2023 and June 30, 2022, respectively.

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2023
Accrued Liabilities, Current [Abstract]
Accrued Expenses	5. Accrued Expenses Accrued expenses consisted of the following (in thousands): June 30, December 31, Research and development expenses $ 5,960 $ 4,840 Employee-related expenses 1,150 2,440 Taxes payable 3,376 3,248 Other 1,143 1,385 Total accrued expenses $ 11,629 $ 11,913

Leases

Leases	6 Months Ended
	Jun. 30, 2023
Leases [Abstract]
Leases	6. Leases In December 2021, the Company entered into a non-cancellable operating lease agreement, as amended subsequently, or the Harrison Lease, pursuant to which the Company leases 31,668 square feet of office and laboratory space located in Boston, Massachusetts, or the Premises. The Harrison Lease commenced for accounting purposes when the Company gained access to the premises on December 29, 2022 or the Lease Commencement Date. The Harrison Lease has a term of nine years and four months from the lease commencement date. The Company’s obligation for the payment of base rent for the Premises begins in May 2023, and will be $ 0.2 million per month, increasing up to $ 0.3 million per month during the term of the Lease. The Company has one option to extend the term of the Harrison Lease, for a period of an additional five years . Due to the timing of the lease commencement date at the end of 2022, there was no fixed lease rent expense associated with the Harrison Lease in 2022. As of June 30, 2023, the Harrison Lease was the only lease for which the Company recorded a lease liability and corresponding right-of-use asset. The landlord has completed and continues to complete significant leasehold improvements to the leased space, a portion of which the Company is obligated to pay per the terms of the Harrison Lease. The Company paid $ 2.0 million for the improvements prior to lease commencement. During the three months ended June 30, 2023, the Company paid nil for the improvements and $ 2.9 million during the six months ended June 30, 2023. The Company expects approximately $ 0.5 million in additional payments for the improvements. The Company has determined that the landlord is the accounting owner of the improvements, payments made and remaining expected payments by the Company for the improvements have been included in the calculation of the right-of-use asset and lease liability. On January 14, 2022, the Company entered into a First Amendment to the Harrison Lease, which updated the Company's pro rata share of the building premises. On March 27, 2023, the Company entered into a Second Amendment to the Harrison Lease by which the term of the Harrison Lease was extended by two months until May 2032 . The Company recorded a $ 0.3 million reduction to the lease asset and liability during the period to account for this amendment. During 2022 and the first quarter of 2023, the Company leased office space in Cambridge, Massachusetts, the terms of which were month-to-month, with a 30-day written notice of cancellation . The Company terminated this lease in January 2023 . The Company also leased laboratory space at the University of Massachusetts, Mount Ida Campus in Newton, Massachusetts, with an initial lease term from February 1, 2022 to January 31, 2023, which the Company extended until March 2023. The Company also leased space at Innovation Building, University of Oxford in Oxford, United Kingdom. The Company terminated its lease in Oxford in July 2022. All of these leases had terms of under 12 months and are considered short-term lease costs and are not recognized on the consolidated balance sheets. Summary of lease costs The components of lease cost under ASC 842 for the leases were as follows (in thousands): Three Months Ended Six Months Ended 2023 2022 2023 2022 Fixed lease cost $ 951 $ — $ 1,958 $ — Variable lease cost 277 — 437 — Short-term lease cost — 257 205 574 Total lease cost $ 1,228 $ 257 $ 2,600 $ 574 Supplemental disclosure of cash flow information under ASC 842 for the leases follows (in thousands): June 30, 2023 Operating cash payments for operating leases $ 3,306 Cash payments for operating leases during the six months ended June 30, 2023 related to lease payments and landlord-owned improvements made to the office and lab space prior to the Company obtaining occupancy. These payments were recorded in the right-of-use asset at December 31, 2022. The remaining lease term for the Harrison Lease is 8.9 years, and the discount rate is 8.0 %. Future minimum lease payments under the non-cancelable operating leases consisted of the following as of June 30, 2023: Year Ending December 31, (in thousands) 2023 (July - December) $ 1,991 2024 3,019 2025 3,109 2026 3,202 2027 3,299 Thereafter 15,529 Total future minimum lease payments $ 30,149 Less: imputed interest ( 8,792 ) Present value of lease liability $ 21,357 Included in the consolidated balance sheet (in thousands) June 30, 2023 Lease liability $ 3,492 Lease liability, net of current portion 17,865 Total lease liability $ 21,357

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2023
Related Party Transactions [Abstract]
Related Party Transactions	7. Related Party Transactions Technology license agreement In March 2018, the Company, Oxford University Innovation Limited (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, or the License Agreement, which was subsequently amended in December 2018, November 2020, and further amended and restated in February 2022. The Licensors and affiliates hold shares of the Company's 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 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 of $ 0.1 million upon transfer of the license technology and data and in 2020 upon amending and restating the License Agreement made two additional payments of $ 19,000 each for a Restatement Completion Fee and License Data Fee. The Company determined that the upfront payment and subsequent Restatement Completion Fee and License Data Fee as part of the license agreement would be expensed upon execution of the original contract and subsequent amendment as the license was acquired for research and development purposes which does not have alternative future uses, and the underlying technology has not reached technological feasibility. The Company could be required to make milestone payments to the Licensors upon completion 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 or sublicensees in excess of a threshold amount between £ 20 million and £ 30 million ($ 25.3 million and $ 37.9 million as of June 30, 2023), 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 agreement. Upon completion of the Company’s IPO in May 2022, 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 IPO raise, was $ 1.4 million, which was paid during the second quarter of 2022 and included in research and development expense on the consolidated statement of operations. Additionally, the Company paid office space rent to OUI through the termination of the lease in July 2022. For the three and six months ended June 30, 2023 total rent payments were not material. For the three and six months ended June 30, 2022 total rent expense and other costs paid to OUI and affiliates was $ 0.1 million and $ 0.2 million, respectively. As of June 30, 2023 and December 31, 2022, nil was due to OUI by the Company for rent payments. Services agreement In November 2020, the Company entered into an agreement, or the Services Agreement, with Carnot Pharma, LLC, or Carnot, under which Carnot provides research and other services to the Company. Carnot is an entity controlled by RA Capital Management, L.P. Entities affiliated with RA Capital Management, L.P. purchased shares of Series A-2 convertible preferred stock in the Company’s preferred stock financing in November of 2020 and May and July of 2021, which were converted to shares of the Company's common stock in connection with the IPO. In addition, entities affiliated with RA Capital Management, L.P. purchased shares of our Series B convertible preferred stock in the Company’s preferred stock financing in July 2021 which were also converted into shares of the Company's common stock in connection with the IPO, and purchased our common stock in the IPO. At the time the Services Agreement was entered into, one member of the Company’s Board of Directors was affiliated with RA Capital Management, L.P., and currently two members of the Company’s Board of Directors are affiliated with R.A. Capital Management, L.P. Under the terms of the Services Agreement, the Company compensates Carnot on a fully burdened cost basis for personal time devoted to Company projects. In addition, the Company reimburses Carnot on a costs basis for any subcontractor costs incurred. The Company pays Carnot on a quarterly basis, in arrears, for services performed and costs incurred. The Services Agreement is for a term of the later of (A) two ( 2 ) years and (B) the later of (a) completion of the Services or (b) latest-to-occur delivery of a final report or any other items required to be delivered to the Company under the last ongoing project as part of the services, if any. The Company may terminate the services agreement by giving 30 days’ prior notice and either party can terminate the services agreement for a material breach, if not cured within 30 days following notice by the nonbreaching party. The Services Agreement was terminated on April 15, 2022 . Expenses incurred by the Company under the Services Agreement with Carnot for the three months ended June 30, 2023 and June 30, 2022, were nil and $ 0.1 million, respectively. Expenses incurred under the Services Agreement with Carnot for the six months ended June 30, 2023 and June 30, 2022, were nil and $ 0.1 million, respectively. As of June 30, 2023 and December 31, 2022, the amounts included in accounts payable related to the Services Agreement and owing to Carnot by the Company were nil , respectively.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. 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 June 30, 2023. 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.

Convertible Preferred Stock and

Convertible Preferred Stock and Stockholders' Equity	6 Months Ended
	Jun. 30, 2023
Equity [Abstract]
Convertible Preferred Stock and Stockholders' Equity	9. Convertible Preferred Stock and Stockholders’ Equity Reverse Stock Split On April 29, 2022, the Company filed a charter amendment to effect a 1.018 for 1 reverse stock split of its issued and outstanding shares of common stock, which resulted in a proportional adjustment to the existing conversion ratios for each series of the Company’s preferred stock. Accordingly, all share and per share amounts for all periods presented in the accompanying consolidated financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect this reverse stock split and adjustment of the preferred stock conversion ratios. Series A-1 convertible preferred stock and Series A-2 convertible preferred stock In connection with the November 24, 2020 Stock Purchase Agreement, the Company agreed to issue an aggregate of 3,939,069 shares of Series A-2 convertible preferred stock to new and existing investors at a price of $ 11.42 per share, in three closings, and elected to convert 1,348,693 shares of outstanding Class A and Class B common stock into 1,372,970 shares of Series A-1 convertible preferred stock. A total of 1,033,117 shares of Class A common stock held by certain founding investors and employees were not modified and continue to exist as Class A common stock. The Series A-1 and Series A-2 convertible preferred stock was converted to common stock immediately prior to the consummation of the Company’s IPO in May 2022 (see Note 1). Series B convertible preferred stock In July 2021 the Company entered into the Series B Stock Purchase Agreement, whereby the Company agreed to issue and sold an aggregate of 7,234,766 shares of Series B convertible stock to new and existing investors at a per share price of $ 15.55 per share for aggregate gross proceeds of $ 112.5 million. The Series B convertible preferred stock was converted to common stock immediately prior to the consummation of the Company's IPO in May 2022 (see Note 1). Common stock 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 have been declared by the board of directors during the three and six months ended June 30, 2023 and June 30, 2022. The Company has reserved the following shares of common stock for issuance, on an as-converted basis, as follows: June 30, December 31, Stock options issued and outstanding 4,217,326 3,341,834 Authorized for future stock awards or option grants 1,111,279 901,462 Authorized for future issuance under employee stock purchase plan 226,000 226,000 Total 5,554,605 4,469,296 Shares of Common Stock Subject to Repurchase In November 2020, in connection with the Series A-2 convertible preferred stock financing, two founding stockholders entered into Stock Restriction Agreements, or Restriction Agreements, whereby 139,057 shares that were previously vested and not subject to repurchase became restricted and subject to repurchase. The repurchase rights lapse 50 % on the one-year anniversary of the Restriction Agreements and 50 % on the second anniversary of the Restriction Agreements. Shares subject to repurchase by the Company are not deemed, for accounting purposes, to be outstanding until those shares vest and therefore are not included in the shares outstanding on the condensed consolidated balance sheet. In connection with the vesting restrictions placed on these previously vested shares, the Company was required to determine the measurement date fair value of the shares, which was $ 2.37 per share or $ 0.3 million in aggregate. The measurement date fair value of the restricted stock will be recognized as stock-based compensation expense over the vesting period. The final shares subject to restriction were released in November 2022, and as of June 30, 2023 and December 31, 2022, zero shares of restricted stock were subject to repurchase by the Company, respectively.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	10 . Stock-Based Compensation The Company maintains three equity compensation plans; the 2020 Stock Plan, or the 2020 Plan, the 2022 Stock Option Incentive Plan, or the 2022 Plan, and the 2022 Employee Stock Purchase Plan, or the ESPP. The number of shares of common stock that may be issued under the 2022 Plan is subject to increase by the number of shares 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 board of directors has determined not to make any further awards under the 2020 Plan. On January 1, 2023, an additional 1,185,660 shares were added to the 2022 Plan as a result of the evergreen provision. As of June 30, 2023, 1,111,279 shares remained available for grant under the 2022 Plan and 226,000 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 Weighted-Average Outstanding as of December 31, 2022 3,341,834 $ 9.52 Granted 1,229,550 $ 14.95 Exercised ( 100,351 ) $ 2.12 Canceled/Forfeited ( 253,707 ) $ 12.64 Outstanding as of June 30, 2023 4,217,326 $ 11.09 The weighted-average grant date fair value of options granted during the six months ended June 30, 2023 was $ 9.31 per share. Stock-Based Compensation Expense Stock based compensation expense recognized for stock option grants included in the accompanying condensed consolidated statements of operations and comprehensive loss is as follows (in thousands): Three Months Ended Six Months Ended 2023 2022 2023 2022 Research and development $ 782 $ 372 $ 1,382 $ 628 General and administrative 1,055 857 1,803 1,415 Total stock-based compensation expense $ 1,837 $ 1,229 $ 3,185 $ 2,043 The Company had 4,217,326 unvested stock options outstanding as of June 30, 2023. As of June 30, 2023, total unrecognized compensation cost related to stock options was $ 23.7 million. This amount is expected to be recognized over a weighted average period of approximately 2.84 years.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2023
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes The Company recorded income tax expense of nil for the three and six months ended June 30, 2023, nil for the three months ended June 30, 2022 and $ 4.4 million for the six months ended June 30, 2022. The income tax expense for the six months ended June 30, 2022 was due to the intellectual property (IP) transfer noted in the paragraph below. On January 1, 2022, or the Transfer Date, the Company’s wholly owned subsidiary, PepGen Limited, transferred all 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 (see Note 3). 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 June 30, 2023, the Company has a liability for the uncertain tax position relative to the IP transfer of $ 0.7 million recorded. The transfer of the intellectual property assets resulted in an estimated tax charge during the six months ended June 30, 2022 to His Majesty’s Revenue & Customs, after considering net operating loss carryforwards, of $ 4.4 million, inclusive of the $ 0.7 million uncertain tax position. The Company maintains a tax liability of $ 3.4 million as of June 30, 2023 related to the estimated tax charge which is accounted for in accrued expenses on the condensed consolidated balance sheet.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2023
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events We filed a shelf registration statement on Form S-3 with the Securities and Exchange Commission, which covers the offering, issuance and sale of an amount up to $ 300.0 million in the aggregate of shares of our 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, we entered into an At-the-Market Equity Offering Sales Agreement with Stifel, Nicolaus & Company, Incorporated, as sales agent. This agreement provides for the issuance and sale by us of up to $ 100.0 million of shares of our 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 this facility.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2023
Accounting Policies [Abstract]
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. Subsequent to the completion of the IPO in May 2022, deferred offering costs totaling $ 4.1 million were recorded within stockholders’ equity (deficit) as a reduction of additional paid-in-capital generated from the initial public offering. As of June 30, 2023, deferred offering costs of $ 0.2 million were recorded within other assets on the consolidated balance sheets related to the Company's Registration Statement on Form S-3 filed with the SEC on June 2, 2023.
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 June 30, 2023, the Company’s cash and money market accounts were held by four financial institutions in the U.S. and one financial institution in the 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.
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 June 30, 2023 and December 31, 2022, the Company had $ 1.5 million of restricted cash classified in other assets on the consolidated balance sheets.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2023
Fair Value Disclosures [Abstract]
Summary of Fair Value of Financial Assets Measure at Fair Value on Recurring Basis	The following tables (in thousands) present information about the Company’s financial assets that have been measured at fair value as of June 30, 2023 and December 31, 2022, 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. As of June 30, 2023 Total Level 1 Level 2 Level 3 US Treasury-backed money market funds $ 136,620 $ 136,620 $ — $ — Total $ 136,620 $ 136,620 $ — $ — As of December 31, 2022 Total Level 1 Level 2 Level 3 US Treasury-backed money market funds $ 18,645 $ 18,645 $ — $ — Total $ 18,645 $ 18,645 $ — $ —
Summary of Reconciliation of Warrant Liabilities	Series A-2 Preferred Balance as of December 31, 2020 $ 30 Change in fair value 196 Balance as of December 31, 2021 226 Change in fair value ( 58 ) Balance as of March 31, 2022 168 Exercise of preferred stock warrants ( 168 ) Balance as of June 30, 2022 $ — Immediately prior to consummation of the IPO, all 35,529 preferred stock warrants that were exercised on May 4, 2022, converted into 34,901 shares of the Company’s common stock. As such, there is no activity during the three- or six-months ended June 30, 2023.

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	6 Months Ended
	Jun. 30, 2023
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): June 30, December 31, Lab equipment $ 4,810 $ 2,424 Computer and office equipment 1,158 171 Construction in process 154 1,129 Total property and equipment 6,122 3,724 Less: accumulated depreciation ( 871 ) ( 389 ) Total property and equipment, net $ 5,251 $ 3,335

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2023
Accrued Liabilities, Current [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following (in thousands): June 30, December 31, Research and development expenses $ 5,960 $ 4,840 Employee-related expenses 1,150 2,440 Taxes payable 3,376 3,248 Other 1,143 1,385 Total accrued expenses $ 11,629 $ 11,913

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2023
Leases [Abstract]
Components of Lease Cost	The components of lease cost under ASC 842 for the leases were as follows (in thousands): Three Months Ended Six Months Ended 2023 2022 2023 2022 Fixed lease cost $ 951 $ — $ 1,958 $ — Variable lease cost 277 — 437 — Short-term lease cost — 257 205 574 Total lease cost $ 1,228 $ 257 $ 2,600 $ 574
Supplemental Disclosure of Cash Flow Information Related to Leases	Supplemental disclosure of cash flow information under ASC 842 for the leases follows (in thousands): June 30, 2023 Operating cash payments for operating leases $ 3,306
Schedule of Future Minimum Lease Payments Under Non-cancelable Operating Leases	Future minimum lease payments under the non-cancelable operating leases consisted of the following as of June 30, 2023: Year Ending December 31, (in thousands) 2023 (July - December) $ 1,991 2024 3,019 2025 3,109 2026 3,202 2027 3,299 Thereafter 15,529 Total future minimum lease payments $ 30,149 Less: imputed interest ( 8,792 ) Present value of lease liability $ 21,357 Included in the consolidated balance sheet (in thousands) June 30, 2023 Lease liability $ 3,492 Lease liability, net of current portion 17,865 Total lease liability $ 21,357

Convertible Preferred Stock a_2

Convertible Preferred Stock and Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2023
Equity [Abstract]
Schedule of Reserved Shares of Common Stock for Issuance, on an As-Converted Basis	The Company has reserved the following shares of common stock for issuance, on an as-converted basis, as follows: June 30, December 31, Stock options issued and outstanding 4,217,326 3,341,834 Authorized for future stock awards or option grants 1,111,279 901,462 Authorized for future issuance under employee stock purchase plan 226,000 226,000 Total 5,554,605 4,469,296

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2023
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 Weighted-Average Outstanding as of December 31, 2022 3,341,834 $ 9.52 Granted 1,229,550 $ 14.95 Exercised ( 100,351 ) $ 2.12 Canceled/Forfeited ( 253,707 ) $ 12.64 Outstanding as of June 30, 2023 4,217,326 $ 11.09
Summary of Stock-based Compensation Expense	Stock based compensation expense recognized for stock option grants included in the accompanying condensed consolidated statements of operations and comprehensive loss is as follows (in thousands): Three Months Ended Six Months Ended 2023 2022 2023 2022 Research and development $ 782 $ 372 $ 1,382 $ 628 General and administrative 1,055 857 1,803 1,415 Total stock-based compensation expense $ 1,837 $ 1,229 $ 3,185 $ 2,043

Nature of Business and Basis _2

Nature of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands				6 Months Ended
	May 16, 2022	May 10, 2022	Apr. 29, 2022	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022	May 04, 2022
Subsidiary, Sale of Stock [Line Items]
Received from IPO and option exercise by underwriters				$ 122,900
Net Received from IPO and option exercise by underwriters				110,200
Reverse stock split, description			1.018 for 1 reverse stock split
Accumulated deficit				138,697	$ 102,856
Cash and cash equivalents				$ 147,027	$ 181,752	$ 218,817
Common stock
Subsidiary, Sale of Stock [Line Items]
Common stock issued in connection with exercise of stock options	1,238,951
Gross proceeds from underwriters exercised option	$ 14,900
IPO
Subsidiary, Sale of Stock [Line Items]
Number of shares sold		9,000,000
Public offering price per share		$ 12
Gross proceeds from sale of shares		$ 108,000
Shares issued upon conversion of redeemable convertible preferred stock							12,359,856
Preferred stock warrants exercised							35,529
IPO | Redeemable Convertible Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Outstanding shares							12,546,805
IPO | Common stock
Subsidiary, Sale of Stock [Line Items]
Option to purchase		1,350,000
Shares issued upon conversion of redeemable convertible preferred stock							34,901

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Additional Information) (Details) - USD ($)	6 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Summary of Significant Accounting Policies [Line Items]
Deferred offering costs	$ 4,100,000
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
Other Assets
Summary of Significant Accounting Policies [Line Items]
Deferred offering costs	$ 200,000

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Fair Value of Financial Assets Measure at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	$ 136,620	$ 18,645
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	136,620	18,645
US Treasury-Backed Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	136,620	18,645
US Treasury-Backed Money Market Funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	$ 136,620	$ 18,645

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) $ / shares in Units, $ in Thousands		6 Months Ended
	May 04, 2022 USD ($) shares	Jun. 30, 2023	Jun. 30, 2022 USD ($)	Nov. 24, 2020 $ / shares shares
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Warrants term				10 years
Warrants exercised, date		May 04, 2022
Proceeds from warrant exercises | $			$ 406
IPO
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Number of warrants purchase granted	35,529
Proceeds from warrant exercises | $	$ 400
Class of warrants or rights number of shares converted into common stock	34,901
Shares issued upon conversion of redeemable convertible preferred stock	12,359,856
IPO | Common Stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Shares issued upon conversion of redeemable convertible preferred stock	34,901
Dividend Yield
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Expected dividend yield				0
Series A-2 Convertible Preferred Stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Number of warrants purchase granted				35,529
Preferred stock par value | $ / shares				$ 11.42

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Reconciliation of Warrant Liabilities (Details) - Series A-2 Preferred Stock Warrant Liability - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 168	$ 226	$ 30
Change in fair value		(58)	196
Exercise of preferred stock warrants	$ (168)
Ending balance		$ 168	$ 226

Property and Equipment, Net - S

Property and Equipment, Net - Summary of Cost and Accumulated Depreciation of Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 6,122	$ 3,724
Less: accumulated depreciation	(871)	(389)
Total property and equipment, net	5,251	3,335
Lab Equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	4,810	2,424
Computer and Office Equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	1,158	171
Construction in Process
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 154	$ 1,129

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Property, Plant and Equipment [Abstract]
Depreciation expenses	$ 0.3	$ 0.1	$ 0.5	$ 0.2

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Accrued Liabilities, Current [Abstract]
Research and development expenses	$ 5,960	$ 4,840
Employee-related expenses	1,150	2,440
Taxes payable	3,376	3,248
Other	1,143	1,385
Total accrued expenses	$ 11,629	$ 11,913

Leases - Additional Information

Leases - Additional Information (Details)		1 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended
	Dec. 28, 2022 USD ($)	Dec. 31, 2021 USD ($) ft²	Jun. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Lessee, Lease, Description [Line Items]
Lease, description				On March 27, 2023, the Company entered into a Second Amendment to the Harrison Lease by which the term of the Harrison Lease was extended by two months until May 2032
Operating lease cost improvements			$ 951,000	$ 1,958,000
Reduction to the lease asset and liability				$ 300,000
Cambridge Massachusetts
Lessee, Lease, Description [Line Items]
Lease term						12 months
Lease, description						the Company leased office space in Cambridge, Massachusetts, the terms of which were month-to-month, with a 30-day written notice of cancellation
Lease termination term						the terms of which were month-to-month, with a 30-day written notice of cancellation
Lease, Existence of Option to Terminate [true false]						true
Lease terimation						2023-01
Newton, Massachusetts
Lessee, Lease, Description [Line Items]
Lease, description						The Company terminated this lease in January 2023. The Company also leased laboratory space at the University of Massachusetts, Mount Ida Campus in Newton, Massachusetts, with an initial lease term from February 1, 2022 to January 31, 2023, which the Company extended until March 2023.
Harrison Lease
Lessee, Lease, Description [Line Items]
Leased space | ft²		31,668
Lease commencement date		Dec. 29, 2022
Lease term		9 years 4 months
Lease, description				The Company’s obligation for the payment of base rent for the Premises begins in May 2023, and will be $0.2 million per month, increasing up to $0.3 million per month during the term of the Lease. The Company has one option to extend the term of the Harrison Lease, for a period of an additional five years.
Monthly rent expense		$ 200,000
Increase in monthly rent expense		$ 300,000
Option to extend lease				The Company has one option to extend the term of the Harrison Lease, for a period of an additional five years.
Option to extend lease term				true
Additional period of lease		5 years
Fixed lease rent expense						$ 0
Remaining lease term			8 years 10 months 24 days	8 years 10 months 24 days
Lease discount rate			8%	8%
Harrison Lease | Leaseholds and Leasehold Improvements
Lessee, Lease, Description [Line Items]
Operating lease cost improvements	$ 2,000,000			$ 2,900,000
Harrison Lease | Leaseholds and Leasehold Improvements | Forecast
Lessee, Lease, Description [Line Items]
Operating lease cost improvements					$ 500,000

Leases - Summary of Components

Leases - Summary of Components of Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Leases [Abstract]
Fixed lease cost	$ 951		$ 1,958
Variable lease cost	277		437
Short-term lease cost		$ 257	205	$ 574
Total lease cost	$ 1,228	$ 257	$ 2,600	$ 574

Leases - Summary of Supplementa

Leases - Summary of Supplemental Disclosure of Cash Flow Information Related to Leases (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2023 USD ($)
Leases [Abstract]
Operating cash payments for operating leases	$ 3,306

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Lease Payments under Non-Cancelable Operating Leases (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Leases [Abstract]
2023 (July - December)	$ 1,991
2024	3,019
2025	3,109
2026	3,202
2027	3,299
Thereafter	15,529
Total future minimum lease payments	30,149
Less: imputed interest	(8,792)
Present value of lease liability	21,357
Lease liability	3,492	$ 5,553
Lease liability, net of current portion	$ 17,865	$ 18,981

Related Party Transactions - Ad

Related Party Transactions - Additional Information) (Details) € in Millions, £ in Millions			1 Months Ended		3 Months Ended		6 Months Ended
	May 31, 2022 USD ($)	May 31, 2022 EUR (€)	Nov. 30, 2020	Mar. 31, 2018 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2023 GBP (£)	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Related Party Transaction [Line Items]
Due to related party for service rendered					$ 1,815,000		$ 1,815,000			$ 1,362,000
Technology License Agreement
Related Party Transaction [Line Items]
Initial upfront payment				$ 100,000
Additional payments of restatement completion fee and license data fee							19,000
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							$ 37,900,000	£ 20
Technology License Agreement | Maximum
Related Party Transaction [Line Items]
Sublicensees threshold amount							25,300,000	£ 30
Technology License Agreement | Oxford University Innovation Limited
Related Party Transaction [Line Items]
Rent payable to related parties					0		0			0
Rent expense						$ 100,000			$ 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%	2%
Required to pay exit fee amount	$ 6,200,000	€ 5
Services Agreement [Member] | Carnot Pharma, LLC
Related Party Transaction [Line Items]
Term of services agreement			2 years
Services agreement terminate prior notice period			30 days
Services agreement terminated date			Apr. 15, 2022
Related party transaction expenses					0	$ 100,000	0		$ 100,000
Due to related party for service rendered					$ 0		$ 0			$ 0

Convertible Preferred Stock a_3

Convertible Preferred Stock and Stockholders' Equity - Additional Information (Details)			1 Months Ended		3 Months Ended		6 Months Ended
	Apr. 29, 2022	Nov. 24, 2020 $ / shares shares	Jul. 31, 2021 USD ($) $ / shares shares	Nov. 30, 2020 USD ($) Stockholder $ / shares shares	Jun. 30, 2023 USD ($) $ / shares shares	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) $ / shares shares	Jun. 30, 2022 USD ($)	Dec. 31, 2022 shares
Class of Stock [Line Items]
Reverse stock split, description	1.018 for 1 reverse stock split
Reverse stock split, conversion ratio	0.982
Common stock, shares authorized					500,000,000		500,000,000
Common stock, par value | $ / shares					$ 0.0001		$ 0.0001
Cash dividend | $					$ 0	$ 0	$ 0	$ 0
Series A-2 Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock par value | $ / shares		$ 11.42
Undesignated Preferred Stock
Class of Stock [Line Items]
Preferred stock authorized					10,000,000		10,000,000
Preferred stock par value | $ / shares					$ 0.0001		$ 0.0001
Stock Purchase Agreement | Series A-2 Convertible Preferred Stock
Class of Stock [Line Items]
Number of shares agreed to issue		3,939,069
Price per share | $ / shares		$ 11.42
Stock Purchase Agreement | Class A and Class B Common Stock
Class of Stock [Line Items]
Common stock, shares outstanding		1,348,693
Stock Purchase Agreement | Series A-1 Convertible Preferred Stock
Class of Stock [Line Items]
Number of shares converted		1,372,970
Stock Purchase Agreement | Class A Common Stock
Class of Stock [Line Items]
Common stock, shares outstanding		1,033,117
Series B Stock Purchase Agreement | Series B Convertible Preferred Stock
Class of Stock [Line Items]
Number of shares agreed to issue			7,234,766
Price per share | $ / shares			$ 15.55
Gross proceeds from issuance of convertible preferred stock | $			$ 112,500,000
Stock Restriction Agreements
Class of Stock [Line Items]
Number of shares became restricted and subject to repurchase				139,057
Number of founding stockholders entered | Stockholder				2
Percentage of repurchase rights lapse on one-year anniversary.				50%
Percentage of repurchase rights lapse on second anniversary				50%
Measurement date fair value of shares vested per share | $ / shares				$ 2.37
Measurement date aggregate fair value of shares | $				$ 300,000
Shares subject to repurchase					0		0		0

Convertible Preferred Stock a_4

Convertible Preferred Stock and Stockholders' Equity - Schedule of Reserved Shares of Common Stock for Issuance, on an As-Converted Basis (Details) - shares	Jun. 30, 2023	Dec. 31, 2022
Class of Stock [Line Items]
Reserved shares of common stock for issuance	5,554,605	4,469,296
Stock Options Issued and Outstanding
Class of Stock [Line Items]
Reserved shares of common stock for issuance	4,217,326	3,341,834
Authorized for Future Stock Awards or Option Grants
Class of Stock [Line Items]
Reserved shares of common stock for issuance	1,111,279	901,462
Authorized for Future Issuance under Employee Stock Purchase Plan
Class of Stock [Line Items]
Reserved shares of common stock for issuance	226,000	226,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Jan. 01, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Outstanding unvested stock options	$ 4,217,326
Unrecognized compensation cost related to unvested share options	$ 23,700,000
Expected recognition period of unrecognized compensation cost related to unvested share options	2 years 10 months 2 days
Stock Option Activity
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Weighted average grant date fair value of options granted	$ 9.31
2022 Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock outstanding percentage	5%
Additonal shares of evergreen provision			1,185,660
Shares remaining available for issuance	1,111,279
2022 Employee Stock Purchase Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of shares authorized and reserved for issuance		226,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Options Activity (Details) - 2020 Plan and 2022 Plan	6 Months Ended
	Jun. 30, 2023 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock Options Outstanding as of December 31, 2022 | shares	3,341,834
Stock Options, Granted | shares	1,229,550
Exercise of stock options, Shares | shares	(100,351)
Stock Options, Canceled/Forfeited | shares	(253,707)
Stock Options, Outstanding as of March 31, 2023 | shares	4,217,326
Weighted Average Exercise Price, Outstanding as of December 31, 2021 | $ / shares	$ 9.52
Weighted Average Exercise Price, Granted | $ / shares	14.95
Weighted average exercise price, exercised | $ / shares	2.12
Weighted average exercise price, canceled/forfeited | $ / shares	12.64
Weighted Average Exercise Price, Outstanding as of March 31, 2022 | $ / shares	$ 11.09

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 1,837	$ 1,229	$ 3,185	$ 2,043
Research and development
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	782	372	1,382	628
General and administrative
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 1,055	$ 857	$ 1,803	$ 1,415

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2022	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Income Taxes [Line Items]
Income tax expense					$ 4,420
Uncertain tax position		700		700
Expected market return	40%
Her Majesty's Revenue and Customs | Accrued Expenses
Income Taxes [Line Items]
Income tax liabilities		$ 3,400	4,400	$ 3,400	4,400
Uncertain tax position			$ 700		$ 700

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - USD ($) $ in Thousands			6 Months Ended
	Aug. 08, 2023	Jun. 16, 2023	Jun. 30, 2022
Subsequent Event [Line Items]
Amount of offering, issuance and sale of equity		$ 300,000
Issuance and sale of shares of common stock			$ 114,267
Stifel, Nicolaus & Company | At-the-Market Equity Offering Sales Agreement | Subsequent Event
Subsequent Event [Line Items]
Issuance and sale of shares of common stock	$ 100,000
Commission to sales agent for gross proceeds from sales	3%