PepGen (PEPG) 10-Q 16 Jun 22 2022 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2022	Jun. 16, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
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		23,631,924
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	245 Main Street
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
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	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 118,854	$ 132,895
Other receivables	4,574	4,744
Prepaid expenses and other current assets	2,240	2,347
Total current assets	125,668	139,986
Property and equipment, net	2,569	636
Other assets	3,642	3,019
Total assets	131,879	143,641
Current liabilities:
Accounts payable (including related party amounts of $3 and $33, respectively)	1,888	3,240
Accrued expenses	14,234	7,081
Total current liabilities	16,122	10,321
Preferred stock warrant liability	168	226
Total liabilities	16,290	10,547
Commitments and Contingencies
Convertible preferred stock	165,176	165,176
Stockholders' deficit:
Additional paid-in capital	2,468	1,653
Accumulated other comprehensive (loss) income	(57)	17
Accumulated deficit	(51,998)	(33,752)
Total stockholders' deficit	(49,587)	(32,082)
Total liabilities, convertible preferred stock, and stockholders' deficit	131,879	143,641
Class A Common Stock
Stockholders' deficit:
Class A common stock, $0.0001 par value; 16,000,000 shares authorized as of March 31, 2022 and December 31, 2021; 963,588 shares issued and outstanding as of March 31, 2022 and December 31, 2021

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Dec. 31, 2018
Accounts payable related parties	$ 14	$ 33
Class A Common Stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	16,000,000	16,000,000
Common stock, shares issued	963,588	963,588	982,315
Common stock, shares outstanding	963,588	963,588

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating Expenses [Abstract]
Research and development (including related party amounts of $29 and $475,respectively)	$ 10,707	$ 5,530
General and administrative	3,186	1,098
Total operating expenses	13,893	6,628
Operating loss	(13,893)	(6,628)
Other income (expense)
Interest income	9
Other income (expense), net	58	(8)
Total other income (expense), net	67	(8)
Net loss before income tax	(13,826)	(6,636)
Income tax expense	(4,420)
Net loss	$ (18,246)	$ (6,636)
Net loss per share, basic and diluted	$ (18.94)	$ (7.42)
Weighted-average common shares outstanding, basic and diluted	963,588	894,060

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Research and development
Related party transaction expenses	$ 43	$ 143

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement of Comprehensive Income [Abstract]
Net loss	$ (18,246)	$ (6,636)
Cumulative translation adjustment arising during the period	(74)	26
Comprehensive loss	$ (18,320)	$ (6,610)

CONDENSED CONSOLIDATED STATEM_4

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	Class A Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Temporary Equity Beginning Balance at Dec. 31, 2020		$ 8,454	$ 7,680
Temporary Equity Beginning Balance, shares at Dec. 31, 2020		1,372,970	700,278
Beginning Balance at Dec. 31, 2020	$ (6,360)					$ 119	$ (8)	$ (6,471)
Beginning Balance, shares at Dec. 31, 2020					894,060
Stock-based compensation expense	188					188
Net loss	(6,636)							(6,636)
Foreign currency translation adjustment	26						26
Temporary Equity Ending Balance at Mar. 31, 2021		$ 8,454	$ 7,680
Temporary Equity Ending Balance, shares at Mar. 31, 2021		1,372,970	700,278
Ending Balance at Mar. 31, 2021	(12,782)					307	18	(13,107)
Ending Balance, shares at Mar. 31, 2021					894,060
Temporary Equity Beginning Balance at Dec. 31, 2021	165,176	$ 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	165,176	$ 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

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities:
Net loss	$ (18,246)	$ (6,636)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation	66	37
Stock-based compensation expense	815	188
Change in fair value of preferred stock warrant liability	(58)
Changes in operating assets and liabilities:
Other receivables	21	77
Prepaids and other current and non-current assets	282	(351)
Accounts payable	(1,572)	42
Accounts payable related party	(32)	38
Accrued expenses and other non-current liabilities	6,452	3,775
Net cash used in operating activities	(12,272)	(2,830)
Cash flows from investing activities:
Purchases of property and equipment	(1,614)	(305)
Net cash used in investing activities	(1,614)	(305)
Cash flows from financing activities:
Payment of deferred offering costs	(18)
Net cash used in financing activities	(18)
Effect of exchange rate changes on cash	(137)	24
Net decrease in cash, cash equivalents and restricted cash	(14,041)	(3,111)
Cash, cash equivalents and restricted cash at beginning of period	134,368	9,778
Cash, cash equivalents and restricted cash at end of period	120,327	6,667
Components of cash, cash equivalents and restricted cash
Cash and cash equivalents	118,854	$ 6,667
Restricted Cash	1,473
Supplemental noncash investing and financing activities
Property and equipment included in accounts payable and accrued expenses	399
Deferred offering costs in accounts payable and accrued expenses	$ 766

Nature of Business and Basis of

Nature of Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2022
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 estimated 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, basic and diluted, will be significantly different in future 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 March 31, 2022, the Company had an accumulated deficit of $ 52.0 million. To date, the Company has funded operations primarily through private placements of convertible preferred stock and its IPO. As of March 31, 2022, the Company had cash and cash equivalents of $ 118.9 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 (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 March 31, 2022, and results of operations for the interim periods ended March 31, 2022 and March 31, 2021. 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, 2021 and 2020, and the notes thereto, included in the Company’s final prospectus related to the IPO, dated May 5, 2022 and filed with the Securities and Exchange Commission (the SEC) pursuant to Rule 424(b)(4) on May 9, 2022 (Final Prospectus).

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2022
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 years ended December 31, 2021 and 2020 included in the Final Prospectus. Since the date of those financial statements, there have been no changes to the Company’s significant accounting policies. Deferred Offering Costs The Company capitalized incremental legal, professional accounting and other third-party fees that are directly associated with the IPO as other non-current assets until the IPO was consummated. After consummation of the IPO, these costs were recorded in stockholders’ equity as a reduction of additional paid-in-capital generated as a result of the offering. As of March 31, 2022, the Company included $ 2.2 million in other non-current assets. The IPO was completed in May 2022 and all deferred offering costs were subsequently recorded within stockholders’ equity as a reduction of additional paid-in-capital generated from the offering. 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, 2022 and December 31, 2021, the Company had $ 1.5 million of restricted cash classified in other assets on the condensed consolidated balance sheets. Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), The amendment relates to leases to increase transparency and comparability among organizations by requiring the recognition of right-of-use, or the ROU, assets obtained in exchange for lease liabilities on the balance sheet. Most prominent among the changes in the standard is the recognition of ROU assets and lease liabilities by lessees for those leases classified as operating leases. Under the standard, disclosures are required to meet the objective of enabling users of condensed consolidated financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. The amendment is effective for the Company as of January 1, 2022. As of January 1, 2022, the Company does not have any leases with initial terms greater than twelve months that have commenced for accounting purposes. For any future leases with initial terms greater than twelve months, the Company will record a lease liability and corresponding ROU asset on is balance sheet and provide required disclosures under Topic 842.

Property and Equipment, Net

Property and Equipment, Net	3 Months Ended
	Mar. 31, 2022
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, December 31, Lab equipment $ 2,063 $ 975 Computer and office equipment $ 42 $ 91 Construction in process 935 — Total property and equipment 3,040 1,066 Less: accumulated depreciation ( 471 ) ( 430 ) Total property and equipment, net $ 2,569 $ 636 Depreciation expense was $ 0.1 million and $ 0.05 million for the three months ended March 31, 2022 and March 31, 2021, respectively.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2022
Related Party Transactions [Abstract]
Related Party Transactions	6. 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 and further amended and restated in November 2020. 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 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 ($ 26.3 million and $ 39.5 million as of March 31, 2022), 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. Additionally, the Company could be required to pay OUI an exit fee between 0.5 % to 2 % of the value determined in an acquisition or IPO, not to exceed £ 5 million ($ 6.6 million as of March 31, 2022), if the Company enters into a transaction with a third-party whereby the party obtains direct or indirect control of the Company, or the Company sells shares on an exchange in an IPO. In lieu of paying the exit fee, the Company has the option to pay a buy out fee, which can be paid at any time to release the Company from its obligation to pay the exit fee. As of March 31, 2022 and December 31, 2021, the Company concluded the exit event was not probable and therefore no obligation was recorded (see Note 11 for final exit fee). Additionally, the Company pays office space rent to OUI. For the three months ended March 31, 2022 and March 31, 2021, total rent payments were not material. As of December 31, 2021, $ 30,000 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. One member of the Company’s Board of Directors is also affiliated with RA 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 March 31, 2022 and March 31, 2021, totaled $ 43,000 and $ 143,000 , respectively. As of March 31, 2022 and December 31, 2021, included in accounts payable was approximately $ 14,000 and $ 2,600 that was due to Carnot by the Company for services rendered under the Services Agreement, respectively.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2022
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. Leases In December 2021, the Company entered into a lease for lab and office space in Massachusetts of approximately 31,668 square feet. The lease term is for 110 months with one optional renewal period of five years . The initial monthly lease payment is $ 0.2 million which increases on an annual basis at three percent. The lease is expected to commence for accounting purposes in the fourth quarter of 2022 or early 2023. 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, 2022. 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	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Convertible Preferred Stock and Stockholders' Equity	8. Convertible Preferred Stock and Stockholders’ Equity 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). The Company concluded the terms of the Stock Purchase Agreement, whereby certain pre-existing Class A and Class B common stock was modified and exchanged for Series A-1 convertible preferred stock, represented a modification as these previous Class A and Class B common stockholders received incremental value through the enhanced rights and preferences associated with the Series A-1 convertible preferred stock. Consequently, in connection with this exchange, the Company recorded a deemed dividend of $ 2.2 million to reflect the difference between the fair value of the Series A-1 convertible preferred stock and the Class A and Class B common stock, on the date of the exchange, based upon a valuation performed by an independent valuation specialist. In November 2020, the Company issued 700,278 shares of Series A-2 convertible preferred stock in the initial closing for gross proceeds of $ 8.0 million. The Stock Purchase Agreement contains provisions that potentially obligate the Company to sell, outside of its control, an additional 3,238,791 shares of Series A-2 convertible preferred stock at $ 11.42 per share for expected gross proceeds of $ 37.0 million, upon the occurrence of two subsequent milestone closings, or the Milestone Closings, or earlier, at the option of any holder of the Series A-2 convertible preferred stock. If the defined milestones are not achieved prior to the Company’s IPO, the holders may elect to purchase these shares prior to the completion of the IPO. If the shares are not purchased prior to the completion of the IPO, then this right to purchase these shares automatically expires. If any holder of the Series A-2 convertible preferred stock does not elect to participate in the two subsequent Milestone Closings, the holder’s shares of Series A-2 convertible preferred stock automatically convert into shares of common stock at a ratio of ten shares of Series A-2 convertible preferred stock to one share of common stock. In addition, to the extent any Series A-1 convertible preferred stock stockholder participated in the Series A-2 preferred stock financing and does not elect to participate in the two subsequent Milestone Closings, the holder’s shares of Series A-1 convertible preferred stock automatically convert into shares of common stock on a one-to-one basis . In May 2021, upon the completion of the first of two defined Milestone Closings outlined in the Stock Purchase Agreement, the Company sold 1,400,558 shares of Series A-2 convertible preferred stock at $ 11.42 per share for aggregate gross proceeds of $ 16.0 million. In July 2021, in advance of the Series B convertible preferred stock financing, the then existing Series A-2 convertible preferred stockholders exercised their right to purchase the remaining Milestone Closing shares and the Company sold 1,838,233 shares of Series A-2 convertible preferred stock at $ 11.42 per share for aggregate gross proceeds of $ 21.0 million. 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). The Company’s convertible preferred stock has the following characteristics: Dividends Each holder of convertible preferred stock is entitled to receive dividends when and if declared by the board of directors at the rate of 6 % of the original issue price per annum. The original issuance price, or Original Issuance Price, with respect to the Series A-1 convertible preferred stock is $ 4.64 per share, with respect to the Series A-2 convertible preferred stock is $ 11.42 per share and with respect to the Series B convertible preferred stock is $ 15.55 per share. Dividends are noncumulative, and no cash dividends have been declared to date. The Series B convertible preferred stock was converted to common stock upon the Company’s IPO in May 2022 (see Note 1). Conversion Each share of convertible preferred stock is convertible without payment of additional consideration at the option of the holder any time after the issuance date into shares of common stock determined by dividing the Original Issuance Price by the conversion price. The conversion price of the convertible preferred stock is initially equal to the Original Issuance Price and is subject to adjustment if the Company issues additional shares of common stock after the applicable original issue date of such series of convertible preferred stock without consideration or for consideration per share less than the conversion price for such series of convertible preferred stock, subject to customary exceptions. The convertible preferred stock is subject to a mandatory conversion in the event (i) that there is a closing of the sale of shares of common stock to the public at a price of at least $ 23.32 per share (subject to adjustment), resulting in at least $ 75 million of gross proceeds in an underwritten public offering pursuant to an effective registration statement under the Securities Act of 1933, as amended, and in connection with such offering the common stock is listed for trading on the Nasdaq Stock Market’s National Market, the New York Stock Exchange or another exchange or marketplace approved by the board of directors or (ii) upon the vote or written consent for such conversion from the Requisite Holders (defined as a majority of the outstanding shares of preferred stock voting as a single class and on an as-converted basis). As of March 31, 2022 and December 31, 2021, all series of convertible preferred stock were convertible into shares of common stock on a one-to-one basis. Upon the effective date of the Reverse Stock Split (see Note 11), the conversion rate was adjusted to 1.018 to 1. Liquidation Holders of the convertible preferred stock were entitled to receive liquidation preferences at the Series A-1, Series A-2 and Series B Original Issue Price, plus all accrued and declared but unpaid dividends. After full payment of the liquidation preference to the holders of the Series A-1, Series A-2 and Series B convertible preferred stock, the remaining assets, if any, were to be distributed ratably to the holders of the common stock provided, however, that each holder of convertible preferred stock was entitled to receive upon such liquidation the greater of (i) the amount distributed pursuant to above and (ii) the amount such holder would have received if all shares of convertible preferred stock had been converted into common stock immediately prior to such liquidation. Redemption rights The holders of Series A-1, Series A-2 and Series B convertible preferred stock did not have any redemption rights, except upon certain liquidation and dissolution events that are outside of the Company’s control. Voting rights The holder of each share of convertible preferred stock was entitled to one vote for each share of common stock into which it would convert and to vote as one class with the common stockholders on all matters. Classification Upon the occurrence of certain change in control events that are outside the Company’s control, including liquidation, sale or transfer of the Company, holders of the convertible preferred stock could effectively cause redemption for cash. As a result, the Company had classified the convertible preferred stock as mezzanine equity on the condensed consolidated balance sheets as the stock was contingently redeemable. The Company elected not to adjust the carrying values of the convertible preferred stock to the liquidation preferences of such shares because it was uncertain whether or when an event would occur that would obligate the Company to pay the liquidation preferences to holders of shares of convertible preferred stock. Subsequent adjustments to the carrying values to the liquidation preferences would have been made only when it had become probable that such a liquidation event would occur. Common stock Under the Amended and Restated Certificate of Incorporation, dated July 30, 2021, the Company has the authority to issue a total of 16,000,000 shares of Class A common stock (par value of $ 0.0001 per share) and 12,582,334 shares of preferred stock (par value of $ 0.0001 per share). In 2018, the Company issued 982,315 shares of Class A common stock to certain founders of the Company with a stated value of $ 0.001 per share, under PepGen Limited. From March 2018 through December 2019, the Company issued 1,348,693 shares of Class A common stock and Class B common stock with a stated value of $ 4.73 per share under, PepGen Limited. In addition, in November of 2020, the Company issued 50,803 shares of Class A common stock in connection with the exercise of stock options, under the PepGen Limited 2020 Share Scheme. In connection with the Reorganization, the Class A and Class B common stock of PepGen Limited were converted into shares of PepGen Inc. on a one-to-one basis into the same Class of common stock originally held. 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 months ended March 31, 2022 and March 31, 2021. The Company has reserved the following shares of common stock for issuance, on an as-converted basis, as follows: March 31, December 31, Convertible preferred stock 12,546,805 12,546,805 Stock options issued and outstanding 2,075,045 1,898,084 Preferred stock warrants issued and outstanding 35,529 35,529 Vesting conditions placed on previously issued common shares 69,529 69,529 Authorized for future stock awards or option grants 232,739 456,416 Total 14,959,647 15,006,363 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. As of March 31, 2022, and December 31 2021, 69,529 shares were subject to repurchase by the Company.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2022
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	9. Stock-Based Compensation As of March 31, 2022, the Company maintains one equity compensation plan, the PepGen Inc. 2020 Stock Plan, or 2020 Plan. As of March 31, 2022, 232,739 shares remained available for issuance under the 2020 Plan. Subsequent to March 31, 2022, and immediately prior to the closing of the Company’s IPO, the Company adopted the 2022 Stock Option and Incentive Plan, or 2022 Plan, and the 2022 Employee Stock Purchase Plan, or the ESPP (see Note 11). Stock Option Activity Stock option activity under the Plan, is as follows: Stock Weighted-Average Outstanding as of December 31, 2021 1,898,084 $ 7.46 Granted 176,961 11.23 Exercised — — Canceled/Forfeited — — Outstanding as of March 31, 2022 2,075,045 $ 7.78 Vested and exercisable as of March 31, 2022 230,078 $ 2.71 Vested and expected to vest as of March 31, 2022 2,075,045 $ 7.78 The weighted-average grant date fair value of options granted during the three months ended March 31, 2022 was $ 7.50 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 2022 2021 Research and development $ 256 $ 23 General and administrative 559 165 Total stock-based compensation expense $ 815 $ 188 As of March 31, 2022, total unrecognized compensation cost related to unvested share options was approximately $ 9.0 million, which is expected to be recognized over a weighted-average period of approximately 3.4 years.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2022
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes The Company recorded income tax expense of $ 4.4 million and nil for the three months ended March 31, 2022 and 2021, respectively. The income tax expense for the three months ended March 31, 2022 was due to the intellectual property (IP) transfer noted in the paragraph below. On January 1, 2022 (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 March 31, 2022, the Company has recognized a liability for the uncertain tax position relative to the IP transfer of $ 0.7 million. The transfer of the intellectual property assets resulted in an estimated tax charge to Her Majesty’s Revenue & Customs, after considering net operating loss carryforwards, of $ 4.4 million, inclusive of the $ 0.7 million uncertain tax position. The liability is accounted for in accrued expenses on the condensed consolidated balance sheet.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2022
Subsequent Events [Abstract]
Subsequent Events	11. Subsequent Events 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. 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. Reverse Stock Split and Charter Amendment On April 29, 2022, the Company filed a charter amendment to affect 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 condensed 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. Additionally, on April 29, 2022, as part of the charter amendment to effect the reverse stock split, the Company amended its charter to rename its Class A Common Stock to common stock, with all of the same rights and privileges as described in Note 8. As part of the charter amendment, the Company also increased the authorized number of shares of common stock from 16,000,000 shares to 36,000,000 shares. In addition, the Company obtained a waiver from the requisite preferred stockholders to effect the mandatory conversion of its preferred stock into common stock, subject to and effective upon the consummation of its initial public offering. 2022 Stock Plan and ESPP In April 2022, the Company’s board of directors and its stockholders adopted the 2022 Stock Option and Incentive Plan, which became effective on May 4, 2022. The 2022 Plan replaced the 2020 Plan, and the Company’s board of directors has determined not to make additional awards under the 2020 Plan following the closing of the IPO. The 2022 Plan provides for the granting of incentive stock options, non-statutory stock options, restricted stock awards, and other forms of stock awards to its employees, directors, and consultants. The Company has initially reserved 2,260,000 shares of common stock for the issuance of awards under the 2022 Plan. Prior to the completion of the IPO, the Company granted 1,104,191 options to purchase common stock to its employees, including certain named executive officers, with an exercise price equal to the IPO price of $ 12.00 per share. The awards had an aggregate grant date fair value of $ 8.9 million. In April 2022, the Company’s board of directors and stockholders adopted the 2022 ESPP, which became effective on May 4, 2022. The Company has initially reserved 226,000 shares of common stock for the issuance to participating employees. OUI Exit Fee 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 IPO, not to exceed £ 5 million ($ 6.6 million as of March 31, 2022) (See Note 6). The exit fee due to OUI, based on the IPO raise, is £ 1.1 million ($ 1.4 million as of March 31, 2022), which will be charged to research and development expense during the second quarter of 2022.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Deferred Offering Costs	Deferred Offering Costs The Company capitalized incremental legal, professional accounting and other third-party fees that are directly associated with the IPO as other non-current assets until the IPO was consummated. After consummation of the IPO, these costs were recorded in stockholders’ equity as a reduction of additional paid-in-capital generated as a result of the offering. As of March 31, 2022, the Company included $ 2.2 million in other non-current assets. The IPO was completed in May 2022 and all deferred offering costs were subsequently recorded within stockholders’ equity as a reduction of additional paid-in-capital generated from the offering.
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, 2022 and December 31, 2021, the Company had $ 1.5 million of restricted cash classified in other assets on the condensed consolidated balance sheets.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), The amendment relates to leases to increase transparency and comparability among organizations by requiring the recognition of right-of-use, or the ROU, assets obtained in exchange for lease liabilities on the balance sheet. Most prominent among the changes in the standard is the recognition of ROU assets and lease liabilities by lessees for those leases classified as operating leases. Under the standard, disclosures are required to meet the objective of enabling users of condensed consolidated financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. The amendment is effective for the Company as of January 1, 2022. As of January 1, 2022, the Company does not have any leases with initial terms greater than twelve months that have commenced for accounting purposes. For any future leases with initial terms greater than twelve months, the Company will record a lease liability and corresponding ROU asset on is balance sheet and provide required disclosures under Topic 842.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2022
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 March 31, 2022 and December 31, 2021, 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 March 31, 2022 Total Level 1 Level 2 Level 3 US Treasury-backed money market funds $ 116,280 $ 116,280 $ — $ — Total $ 116,280 $ 116,280 $ — $ — As of December 31, 2021 Total Level 1 Level 2 Level 3 US Treasury-backed money market funds $ 30,719 $ 30,719 $ — $ — Total $ 30,719 $ 30,719 $ — $ —
Summary of Reconciliation of Warrant Liabilities	A reconciliation of the Level 3 warrant liability 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

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	3 Months Ended
	Mar. 31, 2022
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, December 31, Lab equipment $ 2,063 $ 975 Computer and office equipment $ 42 $ 91 Construction in process 935 — Total property and equipment 3,040 1,066 Less: accumulated depreciation ( 471 ) ( 430 ) Total property and equipment, net $ 2,569 $ 636

Convertible Preferred Stock a_2

Convertible Preferred Stock and Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2022
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: March 31, December 31, Convertible preferred stock 12,546,805 12,546,805 Stock options issued and outstanding 2,075,045 1,898,084 Preferred stock warrants issued and outstanding 35,529 35,529 Vesting conditions placed on previously issued common shares 69,529 69,529 Authorized for future stock awards or option grants 232,739 456,416 Total 14,959,647 15,006,363

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2022
Share-based Payment Arrangement [Abstract]
Summary of Stock Options Activity	Stock option activity under the Plan, is as follows: Stock Weighted-Average Outstanding as of December 31, 2021 1,898,084 $ 7.46 Granted 176,961 11.23 Exercised — — Canceled/Forfeited — — Outstanding as of March 31, 2022 2,075,045 $ 7.78 Vested and exercisable as of March 31, 2022 230,078 $ 2.71 Vested and expected to vest as of March 31, 2022 2,075,045 $ 7.78
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 2022 2021 Research and development $ 256 $ 23 General and administrative 559 165 Total stock-based compensation expense $ 815 $ 188

Nature of Business and Basis _2

Nature of Business and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands	May 16, 2022USD ($)shares	May 10, 2022USD ($)$ / sharesshares	Apr. 29, 2022	Mar. 31, 2022USD ($)shares	May 04, 2022shares	Dec. 31, 2021USD ($)	Mar. 31, 2021USD ($)
Subsidiary, Sale of Stock [Line Items]
Option to purchase				176,961
Received from IPO and option exercise by underwriters | $				$ 122,900
Net Received from IPO and option exercise by underwriters | $				$ 110,200
Reverse stock split, conversion ratio				1.018
Accumulated deficit | $				$ 51,998		$ 33,752
Cash and cash equivalents | $				$ 118,854		$ 132,895	$ 6,667
Subsequent Event
Subsidiary, Sale of Stock [Line Items]
Reverse stock split, conversion ratio			0.982
Reverse stock split, description			1.018 for 1 reverse stock split
Subsequent Event | 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 | Subsequent Event
Subsidiary, Sale of Stock [Line Items]
Number of shares sold		9,000,000
Public offering price per share | $ / shares		$ 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 | Subsequent Event | Redeemable Convertible Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Outstanding shares					12,546,805
IPO | Subsequent Event | Common stock
Subsidiary, Sale of Stock [Line Items]
Option to purchase		1,350,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Additional Information) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Summary of Significant Accounting Policies [Line Items]
Deferred offering costs	$ 2,200,000
Cash	1,500,000
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]
Restricted cash	$ 1,500,000	$ 1,500,000

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	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	$ 116,280	$ 30,719
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	116,280	30,719
US Treasury-Backed Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets	116,280	30,719
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	$ 116,280	$ 30,719

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details)	Mar. 31, 2022$ / shares	Nov. 24, 2020$ / sharesshares
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Preferred stock par value	$ 0.0001
Warrants term		10 years
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 | shares		35,529
Preferred stock par value		$ 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 ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 226	$ 30
Change in fair value	58	196
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	Mar. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,040	$ 1,066
Less: accumulated depreciation	(471)	(430)
Total property and equipment, net	2,569	636
Lab Equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	2,063	975
Computer and Office Equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	42	$ 91
Construction in Process
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 935

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation expenses	$ 100	$ 50

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accrued Liabilities, Current [Abstract]
Research and development expenses	$ 7,718	$ 5,343
Employee-related expenses	635	1,205
Taxes payable	4,326
Other	1,555	533
Total accrued expenses	$ 14,234	$ 7,081

Related Party Transactions - Ad

Related Party Transactions - Additional Information) (Details)	1 Months Ended		3 Months Ended
	Nov. 30, 2020	Mar. 31, 2018USD ($)	Mar. 31, 2022USD ($)	Mar. 31, 2022GBP (£)	Mar. 31, 2021USD ($)	Dec. 31, 2021USD ($)
Related Party Transaction [Line Items]
Due to related party for service rendered			$ 14,000			$ 33,000
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			$ 26,300,000	£ 20,000,000
Technology License Agreement | Maximum
Related Party Transaction [Line Items]
Sublicensees threshold amount			$ 39,500,000	£ 30,000,000
Technology License Agreement | Oxford University Innovation Limited
Related Party Transaction [Line Items]
Rent payable to related parties						30,000
Technology License Agreement | Oxford University Innovation Limited | Minimum
Related Party Transaction [Line Items]
Percentage of exit fee			0.50%	0.50%
Technology License Agreement | Oxford University Innovation Limited | Maximum
Related Party Transaction [Line Items]
Percentage of exit fee			2.00%	2.00%
Required to pay exit fee amount			$ 6,600,000	£ 5,000,000
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			43,000		$ 143,000
Due to related party for service rendered			$ 14,000			$ 2,600

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - Massachusetts $ in Millions	3 Months Ended
	Mar. 31, 2022USD ($)	Dec. 31, 2021ft²
Commitments and contingencies [Line Items]
Leased space | ft²		31,668
Lease term	110 months
Option to extend lease term description	The lease term is for 110 months with one optional renewal period of five years
Option to extend lease term	true
Renewal period	5 years
Initial monthly lease payments | $	$ 0.2
Percentage of lease payments increase on annual basis	3.00%

Convertible Preferred Stock a_3

Convertible Preferred Stock and Stockholders' Equity - Additional Information (Details)	Nov. 24, 2020USD ($)$ / sharesshares	Jul. 31, 2021USD ($)$ / sharesshares	May 31, 2021USD ($)$ / sharesshares	Nov. 30, 2020USD ($)MilestoneStockholder$ / sharesshares	Mar. 31, 2022USD ($)Vote$ / sharesshares	Mar. 31, 2021USD ($)	Dec. 31, 2019$ / sharesshares	Dec. 31, 2021$ / sharesshares	Dec. 31, 2018$ / sharesshares
Class of Stock [Line Items]
Preferred stock conversion basis					As of March 31, 2022 and December 31, 2021, all series of convertible preferred stock were convertible into shares of common stock on a one-to-one basis.
Dividends declared rate					6.00%
Cash dividends declared to date | $					$ 0
Reverse stock split, conversion ratio					1.018
Preferred stock voting rights					one vote for each share
Preferred stock authorized					12,582,334
Preferred stock par value | $ / shares					$ 0.0001
Cash dividend | $					$ 0	$ 0
Number of common stock vote | Vote					1
Minimum
Class of Stock [Line Items]
Sale of shares of common stock public price | $ / shares					$ 23.32
Gross proceeds in underwritten public offering | $					$ 75,000,000
Series A-2 Convertible Preferred Stock
Class of Stock [Line Items]
Gross proceeds from issuance of convertible preferred stock | $		$ 21,000,000
Preferred stock dividends per share | $ / shares					$ 11.42
Preferred stock par value | $ / shares	$ 11.42
Class A and Class B Common Stock
Class of Stock [Line Items]
Common stock, conversion basis					one-to-one basis
Common stock, par value | $ / shares							$ 4.73
Issued shares of common stock							1,348,693
Series A-1 Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends per share | $ / shares					$ 4.64
Class A Common Stock
Class of Stock [Line Items]
Common stock, shares outstanding					963,588			963,588
Common stock, shares authorized					16,000,000			16,000,000
Common stock, par value | $ / shares					$ 0.0001			$ 0.0001
Common stock, shares issued					963,588			963,588	982,315
Stated value per share | $ / shares									$ 0.001
Common stock issued in connection with exercise of stock options				50,803
Series B Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends per share | $ / shares					$ 15.55
Conversion month and year					2022-05
Stock Purchase Agreement
Class of Stock [Line Items]
Number of milestone closings | Milestone				2
Deemed dividend | $	$ 2,200,000
Stock Purchase Agreement | Series A-2 Convertible Preferred Stock
Class of Stock [Line Items]
Number of shares agreed to issue	3,939,069	1,838,233	1,400,558	700,278
Price per share | $ / shares	$ 11.42	$ 11.42	$ 11.42	$ 11.42
Gross proceeds from issuance of convertible preferred stock | $			$ 16,000,000	$ 8,000,000
Additional shares issued				3,238,791
Expected gross proceeds from issuance of convertible preferred stock | $				$ 37,000,000
Preferred stock convertible conversion ratio				10
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
Preferred stock conversion basis				one-to-one basis
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.				50.00%
Percentage of repurchase rights lapse on second anniversary				50.00%
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					69,529			69,529

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	Mar. 31, 2022	Dec. 31, 2021
Class of Stock [Line Items]
Reserved shares of common stock for issuance	14,959,647	15,006,363
Convertible Preferred Stock
Class of Stock [Line Items]
Reserved shares of common stock for issuance	12,546,805	12,546,805
Stock Options Issued and Outstanding
Class of Stock [Line Items]
Reserved shares of common stock for issuance	2,075,045	1,898,084
Preferred Stock Warrants Issued and Outstanding
Class of Stock [Line Items]
Reserved shares of common stock for issuance	35,529	35,529
Vesting Conditions Placed on Previously Issued Common Shares
Class of Stock [Line Items]
Reserved shares of common stock for issuance	69,529	69,529
Authorized for Future Stock Awards or Option Grants
Class of Stock [Line Items]
Reserved shares of common stock for issuance	232,739	456,416

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2022USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value of options granted | $ / shares	$ 7.50
Unrecognized compensation cost related to unvested share options | $	$ 9
Expected recognition period of unrecognized compensation cost related to unvested share options	3 years 4 months 24 days
2020 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized and reserved for issuance | shares	232,739

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Options Activity (Details)	3 Months Ended
	Mar. 31, 2022$ / sharesshares
Share-based Payment Arrangement [Abstract]
Stock Options Outstanding as of December 31, 2021 | shares	1,898,084
Stock Options, Granted | shares	176,961
Stock Options, Outstanding as of March 31, 2022 | shares	2,075,045
Stock Options, Vested and exercisable as of March 31, 2022 | shares	230,078
Stock Options, Vested and expected to vest as of March 31, 2022 | shares	2,075,045
Weighted Average Exercise Price, Outstanding as of December 31, 2021 | $ / shares	$ 7.46
Weighted Average Exercise Price, Granted | $ / shares	11.23
Weighted Average Exercise Price, Outstanding as of March 31, 2022 | $ / shares	7.78
Weighted Average Exercise Price, Vested and exercisable as of March 31, 2022 | $ / shares	2.71
Weighted Average Exercise Price, Vested and expected to vest as of March 31, 2022 | $ / shares	$ 7.78

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 815	$ 188
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	256	23
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 559	$ 165

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	Jan. 01, 2022	Mar. 31, 2022	Mar. 31, 2021
Income Taxes [Line Items]
Income tax expense		$ 4,420
Uncertain tax position		700
Expected market return	40.00%
Her Majesty's Revenue and Customs | Accrued Expenses
Income Taxes [Line Items]
Income tax liabilities		4,400
Uncertain tax position		$ 700

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) $ / shares in Units, € in Millions, $ in Millions	May 31, 2022	May 04, 2022USD ($)shares	Apr. 29, 2022USD ($)$ / sharesshares	Mar. 31, 2022USD ($)$ / sharesshares	Mar. 31, 2022EUR (€)shares	Apr. 30, 2022shares	Dec. 31, 2021shares	Nov. 24, 2020$ / sharesshares
Subsequent Event [Line Items]
Preferred stock par value | $ / shares				$ 0.0001
Warrants term								10 years
Reverse stock split, conversion ratio				1.018	1.018
Initially common stock reserved for future issuance				14,959,647			15,006,363
Option to purchase				176,961	176,961
IPO | Oxford University Innovation Limited
Subsequent Event [Line Items]
Required to pay exit fee amount				$ 1.4	€ 1.1
Maximum | IPO | Oxford University Innovation Limited
Subsequent Event [Line Items]
Required to pay exit fee amount				$ 6.6	€ 5
Subsequent Event
Subsequent Event [Line Items]
Class of warrants or rights proceeds from issuance of initial public offering | $		$ 0.4
Class of warrants or rights number of shares converted into common stock		34,901
Reverse stock split, description			1.018 for 1 reverse stock split
Reverse stock split, conversion ratio			0.982
Subsequent Event | IPO
Subsequent Event [Line Items]
Number of warrants purchase granted		35,529
Subsequent Event | 2022 Stock Option and Incentive Plan
Subsequent Event [Line Items]
Initially common stock reserved for future issuance						2,260,000
Aggregate grant date fair value | $			$ 8.9
Subsequent Event | 2022 Stock Option and Incentive Plan | IPO
Subsequent Event [Line Items]
Option to purchase			1,104,191
Exercise price per share | $ / shares			$ 12
Subsequent Event | 2022 ESPP
Subsequent Event [Line Items]
Initially common stock reserved for future issuance						226,000
Subsequent Event | Minimum
Subsequent Event [Line Items]
Number of increased common stock shares authorized			16,000,000
Subsequent Event | Minimum | IPO | Oxford University Innovation Limited
Subsequent Event [Line Items]
Percentage of required to pay exit fee	0.50%
Subsequent Event | Maximum
Subsequent Event [Line Items]
Number of increased common stock shares authorized			36,000,000
Subsequent Event | Maximum | IPO | Oxford University Innovation Limited
Subsequent Event [Line Items]
Percentage of required to pay exit fee	2.00%
Series A-2 Convertible Preferred Stock
Subsequent Event [Line Items]
Number of warrants purchase granted								35,529
Preferred stock par value | $ / shares								$ 11.42