0001737953-23-000017 | 10-Q | XBRL Viewer

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Summary of significant accounting policies	6 Months Ended
Summary of significant accounting policies	Sep. 30, 2023
Accounting Policies [Abstract]
Summary of significant accounting policies	Summary of significant accounting policies Principles of consolidation The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") and include the accounts of the Company and its direct and indirect wholly owned subsidiaries, Replimune UK, Replimune US, Replimune Securities Corporation and Replimune (Ireland) Limited after elimination of all intercompany accounts and transactions. Use of estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the accrual for research and development expenses and the valuation of stock-based awards. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. Unaudited interim financial information The accompanying consolidated balance sheet as of September 30, 2023, the consolidated statements of operations, of comprehensive loss and of stockholders’ equity for the three and six months ended September 30, 2023 and 2022 and the consolidated statements of cash flows for the six months ended September 30, 2023 and 2022 are unaudited. The unaudited interim consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of September 30, 2023 and the results of its operations for the three and six months ended September 30, 2023 and 2022 and its cash flows for the six months ended September 30, 2023 and 2022. The financial data and other information disclosed in these consolidated notes related to the three and six months ended September 30, 2023 and 2022 are unaudited. The results for the three and six months ended September 30, 2023 are not necessarily indicative of results to be expected for the year ending March 31, 2024, any other interim periods or any future year or period. The financial information included herein should be read in conjunction with the financial statements and notes in the Company's Annual Report on Form 10-K for the year ended March 31, 2023, which was filed with the Securities and Exchange Commission on May 18, 2023 (the "Annual Report"). During the three and six months ended September 30, 2023, there have been no changes to the Company’s significant accounting policies as described in the Annual Report.

Collaboration and other arrangements (Details) - Master Clinical Trial Collaboration and Supply Agreement - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Mar. 31, 2023
Significant agreements
Offset to research and development expense	$ 1,000,000	$ 0	$ 1,700,000	$ 0
Payments received			900,000	$ 0
Receivables	$ 1,700,000		$ 1,700,000		$ 900,000

Stockholders' equity - Equity offerings (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended	6 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Sep. 30, 2022	Sep. 30, 2023	Mar. 31, 2023	Dec. 01, 2022
Class of Warrant or Right [Line Items]
Number of shares issued (in shares)	6,810,658,000
Shares issued during period (in shares)		340,000	340,000
Proceeds from issuance of common stock, net of underwriting fees and discounts	$ 242.6	$ 6.7	$ 6.7
Pre-funded warrants
Class of Warrant or Right [Line Items]
Number of days to purchase additional shares	30 days
Price per share (in USD per share)	$ 23.50
Issuance of pre-funded warrants (in shares)				7,561,583	9,484,238	4,200,000,000
Share price (in dollars per share)	$ 23.4999
Underwriter rights
Class of Warrant or Right [Line Items]
Shares issued during period (in shares)	1,436,172,000
Underwriting discounts, commissions and other offering expenses	$ 16.1

Fair value of financial assets and liabilities (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2023	Mar. 31, 2023
Fair value of financial assets and liabilities
Short-term investments	$ 481,602	$ 558,251
Money market funds
Fair value of financial assets and liabilities
Cash equivalents	60,837	121,455
US Government Agency bonds
Fair value of financial assets and liabilities
Short-term investments	266,256	240,355
US Treasury bonds
Fair value of financial assets and liabilities
Short-term investments	154,509	196,441
Level 1
Fair value of financial assets and liabilities
Short-term investments	0	0
Level 1 \| Money market funds
Fair value of financial assets and liabilities
Cash equivalents	0	0
Level 1 \| US Government Agency bonds
Fair value of financial assets and liabilities
Short-term investments	0	0
Level 1 \| US Treasury bonds
Fair value of financial assets and liabilities
Short-term investments	0	0
Level 2
Fair value of financial assets and liabilities
Short-term investments	481,602	558,251
Level 2 \| Money market funds
Fair value of financial assets and liabilities
Cash equivalents	60,837	121,455
Level 2 \| US Government Agency bonds
Fair value of financial assets and liabilities
Short-term investments	266,256	240,355
Level 2 \| US Treasury bonds
Fair value of financial assets and liabilities
Short-term investments	154,509	196,441
Level 3
Fair value of financial assets and liabilities
Short-term investments	0	0
Level 3 \| Money market funds
Fair value of financial assets and liabilities
Cash equivalents	0	0
Level 3 \| US Government Agency bonds
Fair value of financial assets and liabilities
Short-term investments	0	0
Level 3 \| US Treasury bonds
Fair value of financial assets and liabilities
Short-term investments	$ 0	$ 0

Short-term investments

6 Months Ended

Sep. 30, 2023

Short-Term Investments [Abstract]

Short-term investments

Short-term investmentsAs of September 30, 2023 and March 31, 2023, the Company's available-for-sale investments by type consisted of the following:


	September 30, 2023
	Amortized cost		Gross unrealized gains		Gross unrealized losses		Credit Losses		Fair value
US Government agency bonds	$	266,452	$	68	$	(264)	$	—	$	266,256
US Treasury bonds	154,620		1		(112)		—		154,509
Total	$	421,072	$	69	$	(376)	$	—	$	420,765


	March 31, 2023
	Amortized cost		Gross unrealized gains		Gross unrealized losses		Credit Losses		Fair value
US Government agency bonds	240,371		187		(203)		$	—	240,355
US Treasury bonds	196,488		77		(124)		—		196,441
Total	$	436,859	$	264	$	(327)	$	—	$	436,796

As of September 30, 2023, available-for-sale securities consisted of investments that mature within one year. As of March 31, 2023, available-for-sale securities consisted of investments that mature within one year, with the exception of certain U.S. Government agency bonds and U.S. Treasury bonds which had maturities between one and two years and an aggregate fair value of $15.1 million.

Net loss per share - Computation of diluted net loss per share attributable to common stockholders (Details) - shares	3 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of diluted weighted average shares outstanding (in shares)	11,842,568	9,174,151
Options to purchase common stock
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of diluted weighted average shares outstanding (in shares)	9,155,387	7,413,466
Restricted stock units
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of diluted weighted average shares outstanding (in shares)	2,189,837	1,263,341
Warrants to purchase common stock
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of diluted weighted average shares outstanding (in shares)	497,344	497,344

Nature of the business	6 Months Ended
Nature of the business	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the business	Nature of the business Replimune Group, Inc. (the “Company”) is a clinical-stage biotechnology company with the mission to transform cancer treatment by pioneering the development of a novel portfolio of oncolytic immunotherapies. The Company's proprietary oncolytic immunotherapy product candidates are designed and intended to maximally activate the immune system against cancer. Replimune Group, Inc., whose predecessor was founded in 2015, is the parent company of its wholly owned, direct and indirect subsidiaries: Replimune Limited (“Replimune UK”); Replimune, Inc. (“Replimune US”); Replimune Securities Corporation; and Replimune (Ireland) Limited. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, third-party intellectual property, compliance with government regulations and the ability to secure additional capital to fund operations. Product candidates currently under development will require significant additional research and development efforts, including preclinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance and reporting capabilities. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. Basis of presentation The accompanying consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. The Company has incurred recurring losses since its inception, including net losses of $60.0 million and $43.1 million for the three months ended September 30, 2023 and 2022, respectively, and net losses of $109.6 million and $85.4 million for the six months ended September 30, 2023 and 2022, respectively. In addition, as of September 30, 2023, the Company had an accumulated deficit of $595.1 million. The Company expects to continue to generate operating losses for the foreseeable future. As of the issuance date of these consolidated financial statements, the Company expects that its cash and cash equivalents and short-term investments will be sufficient to fund its operating expenses and capital expenditure requirements through at least 12 months from the issuance of these consolidated financial statements.

Property, plant and equipment, net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Mar. 31, 2023
Property, plant and equipment, net
Property, plant and equipment , gross	$ 16,962		$ 16,962		$ 14,721
Less: Accumulated depreciation	(8,517)		(8,517)		(7,242)
Property, plant and equipment , net	8,445		8,445		7,479
Depreciation and amortization expense	700	$ 600	1,300	$ 1,200
Office equipment
Property, plant and equipment, net
Property, plant and equipment , gross	1,397		1,397		1,240
Computer equipment
Property, plant and equipment, net
Property, plant and equipment , gross	1,846		1,846		1,806
Plant and laboratory equipment
Property, plant and equipment, net
Property, plant and equipment , gross	9,706		9,706		9,186
Leasehold improvements
Property, plant and equipment, net
Property, plant and equipment , gross	1,842		1,842		1,706
Capitalized software
Property, plant and equipment, net
Property, plant and equipment , gross	724		724		0
Construction in progress
Property, plant and equipment, net
Property, plant and equipment , gross	$ 1,447		$ 1,447		$ 783

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Parenthetical) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Tax on short-term investments	$ 0	$ 0	$ 0	$ 0

Geographic information (Details) $ in Thousands	6 Months Ended
Geographic information (Details) $ in Thousands	Sep. 30, 2023 USD ($) region	Mar. 31, 2023 USD ($)
Segments, Geographical Areas [Abstract]
Number of operating geographic regions \| region	2
Geographic information
Long-lived assets	$ 8,445	$ 7,479
United States
Geographic information
Long-lived assets	6,559	5,836
United Kingdom
Geographic information
Long-lived assets	$ 1,886	$ 1,643

Net loss per share - Narrative (Details)	Jul. 09, 2018 shares
Earnings Per Share [Abstract]
Number of stock warrants issued (in shares)	7,561,583

Fair value of financial assets and liabilities

6 Months Ended

Sep. 30, 2023

Fair Value Disclosures [Abstract]

Fair value of financial assets and liabilities

The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis:


	Fair Value Measurements as of September 30, 2023 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents
Money market funds	$	—	$	60,837	$	—	$	60,837

Short-term investments
US Government Agency bonds	—		266,256		—		266,256
US Treasury bonds	—		154,509		—		154,509
	$	—	$	481,602	$	—	$	481,602


	Fair Value Measurements as of March 31, 2023 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents
Money market funds	$	—	$	121,455	$	—	$	121,455
Short-term investments
US Government Agency bonds	—		240,355		—		240,355
US Treasury bonds	—		196,441		—		196,441
	$	—	$	558,251	$	—	$	558,251

The underlying securities in the money market funds held by the Company are all government backed securities.

During the three and six months ended September 30, 2023 and 2022, there were no transfers between levels.

Valuation of cash equivalents and short-term investments

Money market funds, U.S. Government Agency bonds and U.S. Treasury bonds were valued by the Company using quoted prices in active markets for similar securities, which represent a Level 2 measurement within the fair value hierarchy. Cash equivalents consisted of money market funds at September 30, 2023 and money market funds at March 31, 2023.

- Definition

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

+ References + Details

Property, plant and equipment, net

6 Months Ended

Sep. 30, 2023

Property, Plant and Equipment [Abstract]

Property, plant and equipment, net

Property, plant and equipment, net consisted of the following:


	September 30, 2023		March 31, 2023
Office equipment	$	1,397	$	1,240
Computer equipment	1,846		1,806
Plant and laboratory equipment	9,706		9,186
Leasehold improvements	1,842		1,706
Capitalized software	724		—
Construction in progress	1,447		783
Total property, plant and equipment	16,962		14,721
Less: Accumulated depreciation	(8,517)		(7,242)
Property, plant and equipment, net	$	8,445	$	7,479

Depreciation expense was $0.7 million and $1.3 million for the three and six months ended September 30, 2023 and $0.6 million and $1.2 million for the three and six months ended September 30, 2022, respectively. Depreciation expense is recorded within research and development and selling, general and administrative expenses in the consolidated statement of operations.

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2023	Mar. 31, 2023
Stockholders' Equity Attributable to Parent [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	150,000,000	150,000,000
Common stock, issued (in shares)	59,059,343	56,676,313
Common stock, outstanding (in shares)	59,059,343	56,676,313

Debt (Tables)

6 Months Ended

Sep. 30, 2023

Debt Disclosure [Abstract]

Schedule of long-term debt

The summary of obligations under the term loan as of September 30, 2023 and March 31, 2023 consisted of the following (in thousands):


	September 30, 2023		March 31, 2023
Principal loan balance	$	30,453	$	30,222
Facility charge and diligence fee	(293)		(315)
Unamortized issuance costs	(1,308)		(1,410)
Accumulated end of term fee	309		151
Long term debt, net	$	29,161	$	28,648

Schedule of maturities of long-term debt

The annual principal payments due under the Loan Agreement as of September 30, 2023 and March 31, 2023 were as follows:


	September 30, 2023		March 31, 2023
2024	—		—
2025	—		—
2026	—		—
2027	13,438		13,438
Thereafter	18,701		18,701
Total	$	32,139	$	32,139

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

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+ Details

Net loss per share (Tables)

6 Months Ended

Sep. 30, 2023

Earnings Per Share [Abstract]

Schedule of calculation of basic and diluted net loss per share attributable to common stockholders

Basic and diluted net loss per share attributable to common stockholders was calculated as follows:


	Three Months Ended September 30,				Six Months Ended September 30,
	2023		2022		2023		2022
Numerator:
Net loss	$	(60,044)	$	(43,102)	$	(109,599)	$	(85,355)
Denominator:
Weighted average common shares outstanding, basic and diluted	66,582,280		54,770,291		66,475,577		54,492,395
Net loss per share, basic and diluted	$	(0.90)	$	(0.79)	$	(1.65)	$	(1.57)

Schedule of anti-dilutive securities excluded from the computation of diluted net loss per share attributable to common shareholders

The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect:


	Three and Six Months Ended September 30,
	2023	2022
Options to purchase common stock	9,155,387	7,413,466
Unvested restricted stock units	2,189,837	1,263,341
Warrants to purchase common stock	497,344	497,344
	11,842,568	9,174,151

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive loss
Balance (in shares) at Mar. 31, 2022		47,338,660
Balance at Mar. 31, 2022	$ 411,229	$ 47	$ 723,359	$ (311,204)	$ (973)
Increase (decrease) in Stockholders' Equity
Shares issued during period (in shares)		1,686,438
Issuance of common stock through ATM sales, net of offering costs	31,037	$ 2	31,035
Foreign currency translation adjustment	1,737				1,737
Unrealized gain (loss) on short-term investments	(244)				(244)
Exercise of stock options (in shares)		124,028
Exercise of pre-funded warrants	1,562		1,562
Vesting of RSUs (in shares)		149,341
Stock-based compensation expense	7,194		7,194
Net loss	(42,253)			(42,253)
Balance (in shares) at Jun. 30, 2022		49,298,467
Balance at Jun. 30, 2022	410,262	$ 49	763,150	(353,457)	520
Balance (in shares) at Mar. 31, 2022		47,338,660
Balance at Mar. 31, 2022	$ 411,229	$ 47	723,359	(311,204)	(973)
Increase (decrease) in Stockholders' Equity
Shares issued during period (in shares)	340,000
Foreign currency translation adjustment	$ 4,067
Unrealized gain (loss) on short-term investments	(163)
Net loss	(85,355)
Balance (in shares) at Sep. 30, 2022		49,739,407
Balance at Sep. 30, 2022	384,072	$ 50	777,650	(396,559)	2,931
Balance (in shares) at Jun. 30, 2022		49,298,467
Balance at Jun. 30, 2022	$ 410,262	$ 49	763,150	(353,457)	520
Increase (decrease) in Stockholders' Equity
Shares issued during period (in shares)	340,000	340,000
Issuance of common stock through ATM sales, net of offering costs	$ 6,401	$ 1	6,400
Foreign currency translation adjustment	2,330				2,330
Unrealized gain (loss) on short-term investments	81				81
Exercise of stock options (in shares)		88,252
Exercise of pre-funded warrants	1,108		1,108
Vesting of RSUs (in shares)		12,688
Stock-based compensation expense	6,992		6,992
Net loss	(43,102)			(43,102)
Balance (in shares) at Sep. 30, 2022		49,739,407
Balance at Sep. 30, 2022	384,072	$ 50	777,650	(396,559)	2,931
Balance (in shares) at Mar. 31, 2023		56,676,313
Balance at Mar. 31, 2023	555,292	$ 57	1,034,994	(485,488)	5,729
Increase (decrease) in Stockholders' Equity
Foreign currency translation adjustment	(1,305)				(1,305)
Unrealized gain (loss) on short-term investments	(458)				(458)
Exercise of pre-funded warrants (in shares)		1,922,655
Exercise of stock options (in shares)		96,146
Exercise of pre-funded warrants	1,209		1,209
Vesting of RSUs (in shares)		281,211
Stock-based compensation expense	8,846		8,846
Net loss	(49,555)			(49,555)
Balance (in shares) at Jun. 30, 2023		58,976,325
Balance at Jun. 30, 2023	514,029	$ 57	1,045,049	(535,043)	3,966
Balance (in shares) at Mar. 31, 2023		56,676,313
Balance at Mar. 31, 2023	555,292	$ 57	1,034,994	(485,488)	5,729
Increase (decrease) in Stockholders' Equity
Foreign currency translation adjustment	3
Unrealized gain (loss) on short-term investments	$ (244)
Exercise of stock options (in shares)	163,356
Net loss	$ (109,599)
Balance (in shares) at Sep. 30, 2023		59,059,343
Balance at Sep. 30, 2023	465,172	$ 59	1,054,712	(595,087)	5,488
Balance (in shares) at Jun. 30, 2023		58,976,325
Balance at Jun. 30, 2023	514,029	$ 57	1,045,049	(535,043)	3,966
Increase (decrease) in Stockholders' Equity
Foreign currency translation adjustment	1,308				1,308
Unrealized gain (loss) on short-term investments	214				214
Exercise of stock options (in shares)		67,210
Exercise of pre-funded warrants	550	$ 1	549
Vesting of RSUs (in shares)		15,808
Vesting of RSUs	1	$ 1
Stock-based compensation expense	9,114		9,114
Net loss	(60,044)			(60,044)
Balance (in shares) at Sep. 30, 2023		59,059,343
Balance at Sep. 30, 2023	$ 465,172	$ 59	$ 1,054,712	$ (595,087)	$ 5,488

Stockholders' equity

6 Months Ended

Sep. 30, 2023

Equity [Abstract]

Stockholders' equity

Stockholders’ equity

Common stock

As of September 30, 2023 and March 31, 2023, the Company’s certificate of incorporation, as amended and restated, authorized the Company to issue up to 150,000,000 shares of common stock, par value $0.001 per share.

The Company had reserved for common stock for the exercise of outstanding stock options and the vesting of restricted stock units, the number of shares remaining available for grant under the Company’s 2018 Omnibus Incentive Compensation Plan and the Company’s Employee Stock Purchase Plan (see Note 10) and the exercise of the outstanding warrants to purchase shares of common stock as follows:


	September 30, 2023	March 31, 2023
Stock options, issued and outstanding	9,155,387	7,454,828
Restricted stock units	2,189,837	1,351,280
Stock options and restricted stock units, future issuance	2,064,858	2,209,597
Employee stock purchase plan, available for future grants	2,738,208	2,076,603
Pre-IPO warrants to purchase common stock	497,344	497,344
Pre-funded warrants	7,561,583	9,484,238
Total shares of common stock reserved for future issuance	24,207,217	23,073,890

Undesignated preferred stock

As of September 30, 2023, the Company’s certificate of incorporation, as amended and restated, authorized the Company to issue up to 10,000,000 shares of undesignated preferred stock, par value $0.001 per share. There were no undesignated preferred shares issued or outstanding as of September 30, 2023.

ATM program

On August 11, 2020, the Company and the SVB Leerink LLC (the "Agent") entered into a sales agreement, which was subsequently amended on October 21, 2020 (as amended, the “2020 Sales Agreement”), pursuant to which the Company could sell, from time to time, at its option, up to an aggregate of $62.5 million of shares of the Company’s common stock, $0.001 par value per share, through the Agent, as the Company’s sales agent.

During the three months ended June 30, 2022 the Company settled transactions that occurred pursuant to the 2020 Sales Agreement, whereby the Company issued and sold an aggregate of 1,686,438 shares of its common stock, resulting in gross proceeds of $32.0 million, before deducting fees of $1.0 million.

On June 23, 2022, the 2020 Sales Agreement was terminated by the execution by the Company and the Agent of a new sales agreement (the “2022 Sales Agreement”). Under the 2022 Sales Agreement, the Company could sell, from time to time, at its option, up to an aggregate of $100.0 million of shares of the Company’s common stock, $0.001 par value per share, through the Agent, as the Company’s sales agent. During the three and six months ended September 30, 2022, pursuant to the 2022 Sales Agreement, the Company issued and sold an aggregate of 340,000 shares of its common stock, resulting in gross proceeds of $6.7 million, before deducting fees of $0.3 million.

On August 3, 2023, the 2022 Sales Agreement was terminated by the execution by the Company and Leerink Partners LLC (formerly known as SVB Securities LLC) (the "Current Agent") of a new sales agreement (the "2023 Sales Agreement"). Under the 2023 Sales Agreement, the Company may sell, from time to time, at its option, up to an aggregate of $250.0 million of share of the Company's common stock, $0.001 par value shares (the "Shares"), through the Current Agent, as the Company's sales agent.

Any Shares to be offered and sold under the 2023 Sales Agreement will be issued and sold (i) by methods deemed to be an “at the market offering” (“ATM”) as defined in Rule 415(a)(4) promulgated under the Securities Act of 1933, as amended, or if authorized by the Company, in negotiated transactions or block trades, and (ii) pursuant to an automatically effective registration statement on Form S-3 filed by the Company with the Securities and Exchange Commission on August 3, 2023 for an offering of various securities, including shares of the Company’s common stock, preferred stock, debt securities, warrants and/or units for sale to the public in one or more public offerings.

Subject to the terms of the 2023 Sales Agreement, the Current Agent will use reasonable efforts to sell the Shares from time to time, based upon the Company’s instructions (including any price, time or size limits or other customary parameters or conditions the Company may impose). The Company will pay the Current Agent a commission of up to 3.0% of the gross proceeds from the sale of the Shares. The Company has also agreed to provide the Current Agent with customary indemnification rights.

During the three and six months ended September 30, 2023, the Company did not issue or sell any shares under the 2023 Sales Agreement. The Company cannot provide any assurances that it will issue any additional Shares pursuant to the 2023 Sales Agreement.

Equity offerings

In December 2022, the Company completed a public offering of (a) 6,810,658 shares of the Company’s common stock, inclusive of the underwriters 30-day option to purchase up to an additional 1,436,172 shares of the Company’s common stock, at a public offering price of $23.50 per share and (b) pre-funded warrants to purchase 4,200,000 shares of the Company’s common stock at a public offering price of $23.4999 per warrant. The Company received aggregate net proceeds of approximately $242.6 million after deducting underwriting discounts, commissions and other offering expenses payable by the Company of approximately $16.1 million.

Pre-funded Warrants

The pre-funded warrants described above are exercisable at any time after the date of issuance. Unless otherwise modified by a holder of a pre-funded warrant, no holder may exercise a pre-funded warrant if such holder, together with its affiliates, would beneficially own more than 9.99% of the number of shares of the Company’s common stock outstanding immediately after giving effect to such exercise. A holder of a pre-funded warrant may increase or decrease this percentage up to 19.99% by providing at least 61 days’ prior notice to the Company.

The 7,561,583 shares of the Company's common stock underlying the above-described pre-funded warrants are not included in the number of issued and outstanding shares of the Company’s common stock outstanding as reported on the consolidated balance sheet, though they are included in the Company's annual pool increase calculation as well as the weighted average outstanding common stock in the calculation of basic and diluted net loss per share, as described below in Note 11.

During the six months ended September 30, 2023, a holder of the Company's pre-funded warrants exercised 1,922,655 of its pre-funded warrants and the Company issued 1,922,655 shares of common stock in exchange thereof.

- Definition

The entire disclosure for equity.

+ References

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

+ Details

Stockholders' equity (Tables)

6 Months Ended

Sep. 30, 2023

Equity [Abstract]

Schedule of stockholders equity


	September 30, 2023	March 31, 2023
Stock options, issued and outstanding	9,155,387	7,454,828
Restricted stock units	2,189,837	1,351,280
Stock options and restricted stock units, future issuance	2,064,858	2,209,597
Employee stock purchase plan, available for future grants	2,738,208	2,076,603
Pre-IPO warrants to purchase common stock	497,344	497,344
Pre-funded warrants	7,561,583	9,484,238
Total shares of common stock reserved for future issuance	24,207,217	23,073,890

Commitments and contingencies (Tables)

6 Months Ended

Sep. 30, 2023

Commitments and Contingencies Disclosure [Abstract]

Schedule of variable lease components

The table below presents the lease-related costs which are included in the consolidated statements of operations for the three and six months ended September 30, 2023 and 2022:


	Three Months Ended September 30,				Six Months Ended September 30,
	2023		2022		2023		2022
Lease cost
Finance lease costs:
Amortization of right-to-use asset	$	607	$	607	$	1,214	$	1,214
Interest on lease liabilities	542		550		1,086		1,102
Operating lease costs	281		252		561		511
Total lease cost	$	1,430	$	1,409	$	2,861	$	2,827

The following table summarizes the classification of lease costs in the consolidated statement of operations for the three and six months ended September 30, 2023 and 2022 as follows:


	Three Months Ended September 30,				Six Months Ended September 30,
	2023		2022		2023		2022
Finance Lease Costs
Research and development	$	607	$	518	$	1,214	$	1,035
Selling, general and administrative	—		89		—		179
Other income (expense)	542		550		1,086		1,102
Operating Lease Costs
Research and development	228		103		457		213
Selling, general and administrative	53		149		104		298
Total lease cost	$	1,430	$	1,409	$	2,861	$	2,827

The following table provides lease disclosure for the three months ended September 30, 2023 and 2022:


	Six Months Ended September 30,
	2023				2022
Other information
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	528			$	466
Operating cash flows from finance leases	$	1,086			$	1,102
Financing cash flows from finance leases	$	217			$	163
Right-to-use asset obtained in exchange for new operating lease liabilities	$	—			$	—
Weighted-average remaining lease term - operating leases	6.1			years	7.1			years
Weighted-average remaining lease term - financing leases	15.8			years	16.8			years
Weighted-average discount rate - operating leases	10.2		%		9.8		%
Weighted-average discount rate - financing leases	8.3		%		8.3		%

Summary of the maturity of company's lease liabilities

The following table summarizes the maturity of the Company's lease liabilities on an undiscounted cash flow basis and a reconciliation to the operating and financing lease liabilities recognized on its balance sheet as of September 30, 2023:


	September 30, 2023
	Operating leases		Financing lease		Total
2024 (remaining six months)	$	568	$	1,335	$	1,903
2025	1,143		2,718		3,861
2026	1,152		2,799		3,951
2027	1,120		2,883		4,003
2028	1,071		2,969		4,040
Thereafter	1,891		35,054		36,945
Total lease payments	6,945		47,758		54,703
Less: interest	1,755		21,371		23,126
Total lease liabilities	$	5,190	$	26,387	$	31,577

Schedule of additional information related to leases

The following table provides lease disclosure as of September 30, 2023 and March 31, 2023:

Cover - shares	6 Months Ended
Cover - shares	Sep. 30, 2023	Nov. 03, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2023
Document Transition Report	false
Entity File Number	001-38596
Entity Registrant Name	REPLIMUNE GROUP, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-2082553
Entity Address, Address Line One	500 Unicorn Park Drive
Entity Address, Address Line Two	Suite 303
Entity Address, City or Town	Woburn
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01801
City Area Code	781
Local Phone Number	222-9600
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	REPL
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		59,059,343
Entity Central Index Key	0001737953
Amendment Flag	false
Current Fiscal Year End Date	--03-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2

Income taxes	6 Months Ended
Income taxes	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Income taxes	Income taxes

- Definition

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

+ References

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

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

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

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

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

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

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

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

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

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

+ Details

Short-term investments (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Short-term investments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Mar. 31, 2023
US Government Agency bonds
Short-term investments
Amortized cost	$ 266,452	$ 240,371
Gross unrealized gains	68	187
Gross unrealized losses	(264)	(203)
Credit Losses	0	0
Fair value	266,256	240,355
US Treasury bonds
Short-term investments
Amortized cost	154,620	196,488
Gross unrealized gains	1	77
Gross unrealized losses	(112)	(124)
Credit Losses	0	0
Fair value	154,509	196,441
Short-term investments
Short-term investments
Amortized cost	421,072	436,859
Gross unrealized gains	69	264
Gross unrealized losses	(376)	(327)
Credit Losses	0	0
Fair value	$ 420,765	436,796
Securities with maturities between one to two years		$ 15,100

Pre-funded Warrants

6 Months Ended

Sep. 30, 2023

Equity [Abstract]

Pre-funded Warrants

Stockholders’ equity

Common stock


	September 30, 2023	March 31, 2023
Stock options, issued and outstanding	9,155,387	7,454,828
Restricted stock units	2,189,837	1,351,280
Stock options and restricted stock units, future issuance	2,064,858	2,209,597
Employee stock purchase plan, available for future grants	2,738,208	2,076,603
Pre-IPO warrants to purchase common stock	497,344	497,344
Pre-funded warrants	7,561,583	9,484,238
Total shares of common stock reserved for future issuance	24,207,217	23,073,890

Undesignated preferred stock

ATM program

Equity offerings

Pre-funded Warrants

- Definition

The entire disclosure for equity.

+ References

+ Details

Commitments and contingencies - Income Statement Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Lessee, Lease, Description [Line Items]
Finance Lease Costs	$ 607	$ 607	$ 1,214	$ 1,214
Interest on lease liabilities	542	550	1,086	1,102
Operating Lease Costs	281	252	561	511
Total lease cost	1,430	1,409	2,861	2,827
Research and development
Lessee, Lease, Description [Line Items]
Finance Lease Costs	607	518	1,214	1,035
Operating Lease Costs	228	103	457	213
Total lease cost	1,430	1,409	2,861	2,827
Selling, general and administrative
Lessee, Lease, Description [Line Items]
Finance Lease Costs	0	89	0	179
Operating Lease Costs	$ 53	$ 149	$ 104	$ 298

Net loss per share

6 Months Ended

Sep. 30, 2023

Earnings Per Share [Abstract]

Net loss per share

Basic and diluted net loss per share attributable to common stockholders was calculated as follows:


	Three Months Ended September 30,				Six Months Ended September 30,
	2023		2022		2023		2022
Numerator:
Net loss	$	(60,044)	$	(43,102)	$	(109,599)	$	(85,355)
Denominator:
Weighted average common shares outstanding, basic and diluted	66,582,280		54,770,291		66,475,577		54,492,395
Net loss per share, basic and diluted	$	(0.90)	$	(0.79)	$	(1.65)	$	(1.57)

The 7,561,583 shares of the Company's common stock issuable upon exercise of Pre-Funded Warrants described in Note 9 to these consolidated financial statements are included as outstanding common stock in the calculation of basic and diluted net loss per share.

The Company’s potentially dilutive securities, which include stock options and warrants to purchase shares of common stock that resulted from the conversion of warrants to purchase shares of series seed preferred stock existing before the Company's IPO, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect:


	Three and Six Months Ended September 30,
	2023	2022
Options to purchase common stock	9,155,387	7,413,466
Unvested restricted stock units	2,189,837	1,263,341
Warrants to purchase common stock	497,344	497,344
	11,842,568	9,174,151

Stock-based compensation (Tables)

6 Months Ended

Sep. 30, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of stock-based compensation expense

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


	Three Months Ended September 30,				Six Months Ended September 30,
	2023		2022		2023		2022
Research and development	$	4,447	$	2,529	$	7,745	$	5,143
Selling, general and administrative	4,667		4,463		10,216		9,043
	$	9,114	$	6,992	$	17,961	$	14,186

The following table summarizes stock-based compensation expense by award type for the three and six months ended September 30, 2023 and 2022:


	Three Months Ended September 30,				Six Months Ended September 30,
	2023		2022		2023		2022
Stock options	$	5,688	$	4,845	$	11,302	$	10,004
Restricted stock units	3,426		2,147		6,659		4,182
	$	9,114	$	6,992	$	17,961	$	14,186

Schedule of assumptions used to determine the grant-date fair value of stock options granted

The following table presents, on a weighted-average basis, the assumptions that the Company used to determine the grant-date fair value of stock options granted to employees and directors:


	Three Months Ended September 30,				Six Months Ended September 30,
	2023		2022		2023		2022
Risk-free interest rate	4.34	%	3.08	%	3.69	%	2.61	%
Expected term (in years)	6.1		6.1		6.0		6.0
Expected volatility	72.7	%	74.5	%	73.9	%	75.5	%
Expected dividend yield	0	%	0	%	0	%	0	%

Summary of stock option activity

The following table summarizes the Company’s stock option activity:


	Number of Shares	Weighted Average Exercise Price		Weighted Average Contractual Term (Years)	Aggregate Intrinsic Value
Outstanding as of March 31, 2023	7,454,828	$	17.24	6.88	$	31,244
Granted	2,064,526	$	18.08
Exercised	(163,356)	$	10.76
Cancelled	(200,611)	$	24.73
Outstanding as of September 30, 2023	9,155,387	$	17.38	6.78	$	27,858
Options exercisable as of September 30, 2023	5,400,346	$	15.28	5.60	$	26,556
Options vested and expected to vest as of September 30, 2023	9,155,387	$	17.38	6.78	$	27,858

Share-based payment arrangement, restricted stock and restricted stock unit, activity

A summary of the changes in the Company's RSUs during the three months ended September 30, 2023 is as follows:


	Number of Restricted Shares	Weighted Average Grant Date Fair Value
Outstanding as of March 31, 2023	1,351,280	24.38
Granted	1,216,516	18.11
Vested	(297,019)	25.36
Cancelled	(80,940)	21.70
Outstanding as of September 30, 2023	2,189,837	20.86

Summary of significant accounting policies (Policies)	6 Months Ended
Summary of significant accounting policies (Policies)	Sep. 30, 2023
Accounting Policies [Abstract]
Principles of consolidation	The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") and include the accounts of the Company and its direct and indirect wholly owned subsidiaries, Replimune UK, Replimune US, Replimune Securities Corporation and Replimune (Ireland) Limited after elimination of all intercompany accounts and transactions.
Use of estimates	The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the accrual for research and development expenses and the valuation of stock-based awards. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances.
Unaudited interim financial information	The accompanying consolidated balance sheet as of September 30, 2023, the consolidated statements of operations, of comprehensive loss and of stockholders’ equity for the three and six months ended September 30, 2023 and 2022 and the consolidated statements of cash flows for the six months ended September 30, 2023 and 2022 are unaudited. The unaudited interim consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of September 30, 2023 and the results of its operations for the three and six months ended September 30, 2023 and 2022 and its cash flows for the six months ended September 30, 2023 and 2022. The financial data and other information disclosed in these consolidated notes related to the three and six months ended September 30, 2023 and 2022 are unaudited. The results for the three and six months ended September 30, 2023 are not necessarily indicative of results to be expected for the year ending March 31, 2024, any other interim periods or any future year or period. The financial information included herein should be read in conjunction with the financial statements and notes in the Company's Annual Report on Form 10-K for the year ended March 31, 2023, which was filed with the Securities and Exchange Commission on May 18, 2023 (the "Annual Report"). During the three and six months ended September 30, 2023, there have been no changes to the Company’s significant accounting policies as described in the Annual Report.

Fair value of financial assets and liabilities (Tables)

6 Months Ended

Sep. 30, 2023

Fair Value Disclosures [Abstract]

Schedule of company's financial assets and liabilities measured at fair value on a recurring basis

The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis:


	Fair Value Measurements as of September 30, 2023 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents
Money market funds	$	—	$	60,837	$	—	$	60,837

Short-term investments
US Government Agency bonds	—		266,256		—		266,256
US Treasury bonds	—		154,509		—		154,509
	$	—	$	481,602	$	—	$	481,602


	Fair Value Measurements as of March 31, 2023 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents
Money market funds	$	—	$	121,455	$	—	$	121,455
Short-term investments
US Government Agency bonds	—		240,355		—		240,355
US Treasury bonds	—		196,441		—		196,441
	$	—	$	558,251	$	—	$	558,251

Debt

6 Months Ended

Sep. 30, 2023

Debt Disclosure [Abstract]

Debt

On October 6, 2022, the Company entered into a Loan and Security Agreement (the “Loan Agreement”), with Hercules Capital, Inc., as administrative agent, collateral agent and as a lender (“Hercules”). Pursuant to the Loan Agreement, the Company can borrow term loans in an aggregate maximum principal amount of up to $200.0 million under multiple tranches (the “Term Loan Facility”). Under the Loan Agreement, the Company borrowed an initial amount of $30.0 million on the closing date, and at the Company's sole option, could have drawn, but did not draw, down an additional $30.0 million on or prior to September 30, 2023. The Company can also draw as additional term loan advances in an aggregate principal amount of up to $115.0 million during the term of the Term Loan Facility subject to achievement of specified performance milestones, and two additional term loan advances up to an aggregate principal amount of $25.0 million subject to certain terms and conditions, on or prior to the end of the interest-only period. The Company intends to use the proceeds of the Term Loan Facility for working capital and general corporate purposes.

The Loan Agreement was subsequently amended (the "Amendment") on June 28, 2023 pursuant to which the Company agreed to draw an initial term loan advance in an aggregate principal amount not less than $30.0 million, provided that the aggregate amount of the term loan advances made under tranche 1 do not exceed $30.0 million, which reflects a decrease of $30 million from the $60.0 million in the original Loan Agreement for tranche 1. The total amount of the Loan Agreement, as well as the outstanding balance of the loan, is unchanged, but the option to borrow an additional $30.0 million moved from tranche 1 to tranche 2. Therefore, the Amendment provides that the Company can draw down an additional $45.0 million on or prior to December 31, 2023, which includes the $30.0 million that was moved from tranche 1 to tranche 2, and the $15.0 million in the original Loan Agreement for tranche 2. The impact of this amendment is not a modification, as it does not relate to outstanding debt, but is rather an amendment that provides for a future potential benefit. There is no material impact to the financial statements as a result of the Amendment.

The Term Loan Facility will mature on October 1, 2027 (the “Maturity Date”). The outstanding principal balance of the Term Loan Facility bears interest payable in cash at a floating rate per annum equal to the greater of (i) 7.25% and (ii) the sum of the Prime Rate (which is capped at 7.25%) and 1.75%. Accrued interest is payable monthly following the funding of each term loan advance. In addition, the principal balance of the Term Loan Facility will bear “payment-in-kind” interest at the rate of 1.50% (“PIK Interest”), which PIK Interest will be added to the outstanding principal balance of the Term Loan Facility on each interest payment date.

Borrowings under the Loan Agreement are repayable in monthly interest-only payments through September 2026. After the interest-only payment period, borrowings under the Loan Agreement are repayable in equal monthly payments of principal and accrued interest until October 2027. At the Company's option, the Company may prepay all or a portion of the outstanding borrowings, subject to a prepayment fee of 3.0% of the principal amount if prepayment had occurred during the 12 months following the closing date, 2.0% after 12 months following the closing date but prior to 36 months following the closing date, and 1.0% thereafter.

The Loan Agreement contains customary facility fees, events of default and representations, warranties and affirmative and negative covenants, including a financial covenant requiring the Company to maintain unrestricted cash in an amount not less than 35% of the aggregate outstanding secured obligations under the Loan Agreement in accounts subject to a control agreement in favor of the Agent (the “Unrestricted Cash”) at all times commencing on January 1, 2024. In addition, the Loan Agreement also contains a financial covenant that beginning on the later of (i) July 1, 2024 and (ii) the date on which the aggregate outstanding principal amount of the Term Loan Facility is equal to or greater than $100.0 million, the Company is required to satisfy one of the following requirements: (1) achieve a minimum amount of trailing three-month net product revenue tested on a monthly basis, (2) maintain a market capitalization in excess of $1.2 billion and Unrestricted Cash in an amount no less than 50% of the outstanding amount under the Term Loan Facility, or (3) maintain Unrestricted Cash in an amount no less than 85% of the outstanding amount under the Term Loan Facility.

The Company paid a $0.5 million facility charge and incurred debt issuance costs of $1.5 million upon closing of the Loan Agreement. The Loan Agreement also provides for a final payment, payable upon maturity or the repayment of the obligations in full or in part (on a pro rata basis), equal to 4.95% of the aggregate principal amount of Term Loans advanced to the Company and repaid on such date, which is being accrued on the Company's consolidated balance sheet. The amount accrued for the final payment is $0.3 million as of September 30, 2023 and $0.2 million as of March 31, 2023.

Unamortized debt issuance costs are recorded as a reduction of the carrying amount on the term loan and amortized as interest expense using the effective-interest method. In addition, unamortized deferred financing costs related to the Company's right to borrow additional amounts from Hercules in the future were recorded in other assets and amortized to interest expense over the relevant draw period on a straight-line basis. As a result of the Amendment, the Company recorded $0.1 million of the remaining unamortized deferred financing costs related to the Tranche 1 delayed draw to interest expense as of September 30, 2023. Interest expense for the three months and six months ended September 30, 2023 was $1.0 million and $2.1 million.

The summary of obligations under the term loan as of September 30, 2023 and March 31, 2023 consisted of the following (in thousands):


	September 30, 2023		March 31, 2023
Principal loan balance	$	30,453	$	30,222
Facility charge and diligence fee	(293)		(315)
Unamortized issuance costs	(1,308)		(1,410)
Accumulated end of term fee	309		151
Long term debt, net	$	29,161	$	28,648

The annual principal payments due under the Loan Agreement as of September 30, 2023 and March 31, 2023 were as follows:


	September 30, 2023		March 31, 2023
2024	—		—
2025	—		—
2026	—		—
2027	13,438		13,438
Thereafter	18,701		18,701
Total	$	32,139	$	32,139

The table of future payments of long-term debt excludes the end of term charge of $1.5 million, which is due upon the maturity of the loan

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

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

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-URI https://asc.fasb.org//470/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Cash flows from operating activities:
Net loss	$ (109,599)	$ (85,355)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	17,961	14,186
Depreciation	1,275	1,237
Net amortization of premiums and discounts on short-term investments	(6,459)	(161)
Noncash interest expense	513	0
Unrealized foreign currency transaction losses	37	0
Changes in operating assets and liabilities:
Research and development incentives receivable	(835)	(1,417)
Prepaid expenses and other current assets	(2,243)	159
Operating lease, right-of-use-asset	300	252
Finance lease, right-of-use-asset	1,214	1,214
Accounts payable	(1,029)	698
Accrued expenses and other current liabilities	6,977	2,779
Operating lease liabilities	(290)	(257)
Net cash used in operating activities	(92,178)	(66,665)
Cash flows from investing activities:
Purchases of property, plant and equipment and software capitalization	(2,203)	(1,464)
Purchase of short-term investments	(281,246)	(193,685)
Proceeds from sales and maturities of short-term investments	303,493	200,500
Net cash provided by investing activities	20,044	5,351
Cash flows from financing activities:
Proceeds from issuance of common stock through ATM sales, net of offering costs	0	37,438
Principal payment of finance lease obligation	(217)	(163)
Proceeds from exercise of stock options	1,760	2,670
Net cash provided by financing activities	1,543	39,945
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(3)	4,351
Net (decrease) increase in cash, cash equivalents and restricted cash	(70,594)	(17,018)
Cash, cash equivalents and restricted cash at beginning of period	148,226	107,584
Cash, cash equivalents and restricted cash at end of period	77,632	90,566
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	1,343	0
Cash paid for income taxes	300	0
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable	$ 138	$ 96

Stock-based compensation - Assumptions to determine grant-date fair value of stock options (Details) - Stock options	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Stock-Based Compensation
Risk-free interest rate	4.34%	3.08%	3.69%	2.61%
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days	6 years	6 years
Expected volatility	72.70%	74.50%	73.90%	75.50%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Debt - Maturity of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
End of term charge			$ 1,500
Line of Credit \| Term Loan Facility \| Secured Debt
Debt Instrument [Line Items]
2024	$ 0	$ 0
2025	0	0
2026	0	0
2027	13,438	13,438
Thereafter	18,701	18,701
Total	$ 32,139	$ 32,139

Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Mar. 31, 2023
Accrued Liabilities and Other Liabilities [Abstract]
Accrued research and development costs	$ 19,945	$ 11,261
Accrued compensation and benefits costs	7,128	9,909
Accrued professional fees	687	540
Other	3,891	2,994
Total accrued expenses and other current liabilities	$ 31,651	$ 24,704

Pre-funded Warrants - Narrative (Details) - shares	1 Months Ended	6 Months Ended
Pre-funded Warrants - Narrative (Details) - shares	Oct. 31, 2020	Sep. 30, 2023	Mar. 31, 2023	Dec. 01, 2022	Jul. 09, 2018
Class of Warrant or Right [Line Items]
Number of stock warrants issued (in shares)					7,561,583
Pre-funded warrants
Class of Warrant or Right [Line Items]
Number of stock warrants issued (in shares)		1,922,655
Common stock
Class of Warrant or Right [Line Items]
Shares issued during period (in shares)		1,922,655
Pre-funded warrants
Class of Warrant or Right [Line Items]
Maximum percentage of holding for exercise warrants (as a percent)	9.99%
Maximum percentage of increase (decrease) of holding for exercise warrants (as a percent)	19.99%
Prior notice period to change percentage of holding (in days)	61 days
Issuance of pre-funded warrants (in shares)		7,561,583	9,484,238	4,200,000,000

Stock-based compensation - Classification of expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Share-Based Compensation
Stock-based compensation expense	$ 9,114	$ 6,992	$ 17,961	$ 14,186
Stock options
Share-Based Compensation
Stock-based compensation expense	5,688	4,845	11,302	10,004
Restricted stock units
Share-Based Compensation
Stock-based compensation expense	3,426	2,147	6,659	4,182
Research and development
Share-Based Compensation
Stock-based compensation expense	4,447	2,529	7,745	5,143
Selling, general and administrative
Share-Based Compensation
Stock-based compensation expense	$ 4,667	$ 4,463	$ 10,216	$ 9,043

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2023	Mar. 31, 2023
Current assets:
Cash and cash equivalents	$ 75,996	$ 146,590
Short-term investments	420,765	436,796
Research and development incentives receivable	2,900	2,939
Prepaid expenses and other current assets	8,514	6,278
Total current assets	508,175	592,603
Property, plant and equipment, net	8,445	7,479
Research and development incentives receivable, non-current	809	0
Restricted cash	1,636	1,636
Right-to-use asset - operating leases	4,882	5,208
Right-to-use asset - financing leases	38,451	39,665
Total assets	562,398	646,591
Current liabilities:
Accounts payable	4,365	5,364
Accrued expenses and other current liabilities	31,651	24,704
Operating lease liabilities, current	1,138	1,118
Financing lease liabilities, current	2,678	2,639
Total current liabilities	39,832	33,825
Operating lease liabilities, non-current	4,052	4,389
Financing lease liabilities, non-current	23,709	23,965
Long term debt, net of discount	29,161	28,648
Other liabilities, non-current	472	472
Total liabilities	97,226	91,299
Commitments and contingencies (Note 14)
Stockholders' equity
Common stock, $0.001 par value; 150,000,000 shares authorized as of September 30, 2023 and March 31, 2023; 59,059,343 and 56,676,313 shares issued and outstanding as of September 30, 2023 and March 31, 2023, respectively	59	57
Additional paid-in capital	1,054,712	1,034,994
Accumulated deficit	(595,087)	(485,488)
Accumulated other comprehensive income	5,488	5,729
Total stockholders' equity	465,172	555,292
Total liabilities and stockholders' equity	$ 562,398	$ 646,591

Debt - Summary of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Mar. 31, 2023
Debt Instrument [Line Items]
Long term debt, net	$ 29,161	$ 28,648
Secured Debt \| Line of Credit \| Term Loan Facility
Debt Instrument [Line Items]
Principal loan balance	30,453	30,222
Facility charge and diligence fee	(293)	(315)
Unamortized issuance costs	(1,308)	(1,410)
Accumulated end of term fee	309	151
Long term debt, net	$ 29,161	$ 28,648

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details

Collaboration and other arrangements	6 Months Ended
Collaboration and other arrangements	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration and other arrangements	Significant agreements Agreement with Bristol-Myers Squibb Company In February 2018, the Company entered into an agreement with Bristol-Myers Squibb Company (“BMS”). Pursuant to the agreement, BMS will provide to the Company, at no cost, a compound for use in the Company’s ongoing clinical trial of RP1. Under the agreement, the Company will sponsor, fund and conduct the clinical trial in accordance with an agreed-upon protocol. BMS granted the Company a non-exclusive, non-transferrable, royalty-free license (with a right to sublicense) under its intellectual property to its compound in the clinical trial and agreed to supply its compound, at no cost to the Company, for use in the clinical trial. In January 2020, this agreement was expanded to cover an additional cohort of 125 patients with anti-PD-1 failed melanoma. Unless earlier terminated, the agreement will remain in effect until (i) the completion of the clinical trial, (ii) all related clinical trial data have been delivered to both parties and (iii) the completion of any statistical analyses and bioanalyses contemplated by the clinical trial protocol or any analysis otherwise agreed upon by the parties. The agreement may be terminated by either party (x) in the event of an uncured material breach by the other party, (y) in the event the other party is insolvent or in bankruptcy proceedings or (z) for safety reasons. Upon termination, the licenses granted to the Company to use BMS’s compound in the clinical trial will terminate. In April 2019, the Company entered into a separate agreement with BMS on terms similar to the terms set forth in the agreement described above, pursuant to which BMS will provide to the Company, at no cost, nivolumab for use in the Company’s Phase 1 clinical trial of RP2 in combination with nivolumab. Agreement with Regeneron Pharmaceuticals, Inc. In May 2018, the Company entered into an agreement with Regeneron Pharmaceuticals, Inc. (“Regeneron”). The Company and Regeneron are each independently developing compounds for the treatment of certain tumor types. Pursuant to the agreement, the Company agreed to undertake one or more clinical trials with Regeneron for the administration of our product candidates in combination with cemiplimab, an anti-PD-1 therapy developed by Regeneron, across multiple solid tumor types. The first of which, agreed in June 2018, is our ongoing Phase 2 clinical trial testing RP1 in combination with cemiplimab versus cemiplimab alone in patients with CSCC. Each clinical trial will be conducted pursuant to an agreed study plan which, among other things, will identify the name of the sponsor and which party will manage the particular study, and include the protocol, the budget and a schedule of clinical obligations. The first study plan related to Phase 2 clinical trial in CSCC has been agreed. Pursuant to the terms of the agreement, each party granted the other party a non-exclusive license under its respective intellectual property and agreed to contribute the necessary resources needed to fulfill its respective obligations, in each case, under the terms of the agreed-upon or to-be agreed upon study plans. Development costs of a particular clinical trial will be split equally. The agreement contains representations, warranties, undertakings and indemnities customary for a transaction of this nature. The agreement also contains certain time-based covenants that restrict us from entering into a third-party arrangement with respect to the use of our product candidates in combination with an anti-PD-1 therapy and that restrict Regeneron from entering into a third-party arrangement with respect to the use of cemiplimab in combination with an HSV-1 virus, in each case, for the treatment of a tumor type that is the subject of a clinical trial to which the covenants apply. Unless otherwise mutually agreed in a future study plan, these covenants are only applicable to our ongoing Phase 2 clinical trial in CSCC. The agreement may be terminated by either party if (i) there is no active study plan for which a final study report has not been completed and the parties have not entered into a study plan for an additional clinical trial within a period of time after the delivery of the most recent final study report or (ii) in the event of a material breach. The agreement with Regeneron is accounted for under ASC 808, Collaborative Arrangements (“ASC 808”), as both parties are active participants and each party pays its own compound costs and shares equally in development costs in accordance with and up to the amount in the agreed upon first study plan. The Company will account for costs incurred as part of the study, including costs to supply compounds for use in the study, as research and development expenses within the consolidated statement of operations. The Company will recognize any amounts received from Regeneron in connection with this agreement as an offset to research and development expense within the consolidated statement of operations. In July 2022, Regeneron informed the Company that the costs of the study have reached the initial budget for the initial study plan of June 2018 and that Regeneron's reimbursement of CERPASS study costs to the Company have completed in the period ending June 30, 2022 in relation to the initial study budget. As a result of this notice from, and the ongoing communications with, Regeneron, we have not recorded any cost-sharing reimbursements from Regeneron in prepaid expenses and other current assets in the consolidated balance sheet or as an offset to research and development expense within the consolidated statement of operations since Regeneron informed us that Regeneron’s reimbursement of CERPASS study costs have completed. The Company does not expect any further reimbursements from Regeneron related to the initial study plan of June 2018. The Company did not record any costs as an offset to research and development expenses during the six months ended September 30, 2023, and recorded $1.1 million during the six months ended September 30, 2022. During the six months ended September 30, 2023 and 2022, the Company received payments under the terms of the agreement from Regeneron of $0.0 million and $2.0 million, respectively. No receivables from Regeneron were booked in connection with this agreement as of September 30, 2023 or March 31, 2023. Collaboration and other arrangements Roche In December 2022, the Company announced that it had entered into a Master Clinical Trial Collaboration and Supply Agreement with Roche in relation to its RP2 and RP3 programs in colorectal cancer, or CRC, and hepatocellular carcinoma, or HCC. Under the agreement, the companies will collaborate in two 30 patient cohort signal finding studies in third-line, or 3L, CRC and two 15 patient cohort signal finding studies in second-line, or 2L, HCC. Under the terms of the agreement, the companies will share costs and Roche will supply its currently approved drugs, atezolizumab and bevacizumab for 2L HCC and 3L CRC combined with RP3. Roche will also supply atezolizumab and bevacizumab for 2L HCC and 3L CRC combined with RP2. The Company has retained the responsibility of operating the clinical trials as well as retaining all the rights to the development and commercialization of the Company's product candidates. The agreement may be terminated by either party upon sixty (60) days prior written notice to the other party. The agreement with Roche is accounted for under ASC 808, Collaborative Arrangements (“ASC 808”), as both parties are active participants and each party pays its own compound costs and shares equally in development costs in accordance with and up to the amount in the agreed upon first study plan. The Company will account for costs incurred as part of the study, including costs to supply compounds for use in the study, as research and development expenses within the consolidated statement of operations. The Company will recognize any amounts received from Roche in connection with this agreement as an offset to research and development expense within the consolidated statement of operations. During the three and six months ended September 30, 2023 and 2022, the Company did not make any payments to Roche under the terms of the agreement. The Company recorded $1.0 million and $1.7 million as an offset to research and development expenses during the three and six months ended September 30, 2023, respectively. The Company did not record any costs as an offset to research and development expenses during the three and six months ended September 30, 2022. During the six months ended September 30, 2023 and 2022, the Company received payments under the terms of the agreement from Roche of $0.9 million and $0.0 million, respectively. As of September 30, 2023 and March 31, 2023, the Company recorded $1.7 million and $0.9 million as receivables from Roche in connection with this agreement, respectively. Incyte In July 2023, the Company entered into a Clinical Trial Collaboration and Supply Agreement with Incyte Corporation, or Incyte. Under the agreement, the companies will collaborate in a signal finding study in which Incyte will initiate and sponsor a clinical trial of INCB99280 (oral PD-L1 inhibitor) and RP1 in approximately 40 patients with unresectable, high risk CSCC in the neoadjuvant setting. Under the terms of the agreement, the Company will supply Incyte with RP1 for the study and share costs of the study equally with Incyte. The agreement may be terminated by either party upon (i) a material breach not reasonably cured within thirty (30) days; (ii) the discontinuation of development of its clinical drug candidate; (iii) the unethical or illegal business practices of the other party; or (iv) if the parties have not agreed on the protocol or budget within ninety (90) days of the effective date of the agreement. In addition, the Company may terminate the agreement upon the inappropriate or unsafe use of the RP1 product candidate. During the three and six months ended September 30, 2023, the Company did not make any payments to, or receive any payments from, Inctye under the terms of the agreement. Additionally, no costs were recorded to research and development expenses during the three and six months ended September 30, 2023 related to this agreement. Amgen In August 2023 the Company entered into a Settlement Agreement with Amgen and mutually agreed to terminate the Company's challenges to Amgen's patents. In connection with the Settlement Agreement, the Company entered into a License and Covenant Agreement with Amgen in which the Company agreed to pay Amgen low single-digit royalty payments on net sales of its products that, but for the license, could be found to infringe a valid Amgen patent on a country-by-country and product-by-product basis.

Commitments and contingencies - Other information (Details) - USD ($) $ in Thousands	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Mar. 31, 2023
Leases
Right-to-use operating lease asset	$ 4,882		$ 5,208
Right-to-use finance lease asset	38,451		39,665
Total lease assets	43,333		44,873
Operating lease liabilities, current	1,138		1,118
Finance lease liabilities, current	2,678		2,639
Operating lease liabilities, non-current	4,052		4,389
Financing lease liabilities, non-current	23,709		23,965
Total lease liabilities	31,577		$ 32,111
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	528	$ 466
Operating cash flows from finance leases	1,086	1,102
Financing cash flows from finance leases	217	163
Right-to-use asset obtained in exchange for new operating lease liabilities	$ 0	$ 0
Weighted-average remaining lease term - operating leases	6 years 1 month 6 days	7 years 1 month 6 days
Weighted-average remaining lease term - financing leases	15 years 9 months 18 days	16 years 9 months 18 days
Weighted-average discount rate - operating leases	10.20%	9.80%
Weighted-average discount rate - financing leases	8.30%	8.30%

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Net loss	$ (60,044)	$ (43,102)	$ (109,599)	$ (85,355)
Other comprehensive loss:
Foreign currency translation gain	1,308	2,330	3	4,067
Net unrealized loss on short-term investments, net of tax of $0	214	81	(244)	(163)
Comprehensive loss	$ (58,522)	$ (40,691)	$ (109,840)	$ (81,451)

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Significant agreements	6 Months Ended
Significant agreements	Sep. 30, 2023
Significant agreements
Significant agreements	Significant agreements Agreement with Bristol-Myers Squibb Company In February 2018, the Company entered into an agreement with Bristol-Myers Squibb Company (“BMS”). Pursuant to the agreement, BMS will provide to the Company, at no cost, a compound for use in the Company’s ongoing clinical trial of RP1. Under the agreement, the Company will sponsor, fund and conduct the clinical trial in accordance with an agreed-upon protocol. BMS granted the Company a non-exclusive, non-transferrable, royalty-free license (with a right to sublicense) under its intellectual property to its compound in the clinical trial and agreed to supply its compound, at no cost to the Company, for use in the clinical trial. In January 2020, this agreement was expanded to cover an additional cohort of 125 patients with anti-PD-1 failed melanoma. Unless earlier terminated, the agreement will remain in effect until (i) the completion of the clinical trial, (ii) all related clinical trial data have been delivered to both parties and (iii) the completion of any statistical analyses and bioanalyses contemplated by the clinical trial protocol or any analysis otherwise agreed upon by the parties. The agreement may be terminated by either party (x) in the event of an uncured material breach by the other party, (y) in the event the other party is insolvent or in bankruptcy proceedings or (z) for safety reasons. Upon termination, the licenses granted to the Company to use BMS’s compound in the clinical trial will terminate. In April 2019, the Company entered into a separate agreement with BMS on terms similar to the terms set forth in the agreement described above, pursuant to which BMS will provide to the Company, at no cost, nivolumab for use in the Company’s Phase 1 clinical trial of RP2 in combination with nivolumab. Agreement with Regeneron Pharmaceuticals, Inc. In May 2018, the Company entered into an agreement with Regeneron Pharmaceuticals, Inc. (“Regeneron”). The Company and Regeneron are each independently developing compounds for the treatment of certain tumor types. Pursuant to the agreement, the Company agreed to undertake one or more clinical trials with Regeneron for the administration of our product candidates in combination with cemiplimab, an anti-PD-1 therapy developed by Regeneron, across multiple solid tumor types. The first of which, agreed in June 2018, is our ongoing Phase 2 clinical trial testing RP1 in combination with cemiplimab versus cemiplimab alone in patients with CSCC. Each clinical trial will be conducted pursuant to an agreed study plan which, among other things, will identify the name of the sponsor and which party will manage the particular study, and include the protocol, the budget and a schedule of clinical obligations. The first study plan related to Phase 2 clinical trial in CSCC has been agreed. Pursuant to the terms of the agreement, each party granted the other party a non-exclusive license under its respective intellectual property and agreed to contribute the necessary resources needed to fulfill its respective obligations, in each case, under the terms of the agreed-upon or to-be agreed upon study plans. Development costs of a particular clinical trial will be split equally. The agreement contains representations, warranties, undertakings and indemnities customary for a transaction of this nature. The agreement also contains certain time-based covenants that restrict us from entering into a third-party arrangement with respect to the use of our product candidates in combination with an anti-PD-1 therapy and that restrict Regeneron from entering into a third-party arrangement with respect to the use of cemiplimab in combination with an HSV-1 virus, in each case, for the treatment of a tumor type that is the subject of a clinical trial to which the covenants apply. Unless otherwise mutually agreed in a future study plan, these covenants are only applicable to our ongoing Phase 2 clinical trial in CSCC. The agreement may be terminated by either party if (i) there is no active study plan for which a final study report has not been completed and the parties have not entered into a study plan for an additional clinical trial within a period of time after the delivery of the most recent final study report or (ii) in the event of a material breach. The agreement with Regeneron is accounted for under ASC 808, Collaborative Arrangements (“ASC 808”), as both parties are active participants and each party pays its own compound costs and shares equally in development costs in accordance with and up to the amount in the agreed upon first study plan. The Company will account for costs incurred as part of the study, including costs to supply compounds for use in the study, as research and development expenses within the consolidated statement of operations. The Company will recognize any amounts received from Regeneron in connection with this agreement as an offset to research and development expense within the consolidated statement of operations. In July 2022, Regeneron informed the Company that the costs of the study have reached the initial budget for the initial study plan of June 2018 and that Regeneron's reimbursement of CERPASS study costs to the Company have completed in the period ending June 30, 2022 in relation to the initial study budget. As a result of this notice from, and the ongoing communications with, Regeneron, we have not recorded any cost-sharing reimbursements from Regeneron in prepaid expenses and other current assets in the consolidated balance sheet or as an offset to research and development expense within the consolidated statement of operations since Regeneron informed us that Regeneron’s reimbursement of CERPASS study costs have completed. The Company does not expect any further reimbursements from Regeneron related to the initial study plan of June 2018. The Company did not record any costs as an offset to research and development expenses during the six months ended September 30, 2023, and recorded $1.1 million during the six months ended September 30, 2022. During the six months ended September 30, 2023 and 2022, the Company received payments under the terms of the agreement from Regeneron of $0.0 million and $2.0 million, respectively. No receivables from Regeneron were booked in connection with this agreement as of September 30, 2023 or March 31, 2023. Collaboration and other arrangements Roche In December 2022, the Company announced that it had entered into a Master Clinical Trial Collaboration and Supply Agreement with Roche in relation to its RP2 and RP3 programs in colorectal cancer, or CRC, and hepatocellular carcinoma, or HCC. Under the agreement, the companies will collaborate in two 30 patient cohort signal finding studies in third-line, or 3L, CRC and two 15 patient cohort signal finding studies in second-line, or 2L, HCC. Under the terms of the agreement, the companies will share costs and Roche will supply its currently approved drugs, atezolizumab and bevacizumab for 2L HCC and 3L CRC combined with RP3. Roche will also supply atezolizumab and bevacizumab for 2L HCC and 3L CRC combined with RP2. The Company has retained the responsibility of operating the clinical trials as well as retaining all the rights to the development and commercialization of the Company's product candidates. The agreement may be terminated by either party upon sixty (60) days prior written notice to the other party. The agreement with Roche is accounted for under ASC 808, Collaborative Arrangements (“ASC 808”), as both parties are active participants and each party pays its own compound costs and shares equally in development costs in accordance with and up to the amount in the agreed upon first study plan. The Company will account for costs incurred as part of the study, including costs to supply compounds for use in the study, as research and development expenses within the consolidated statement of operations. The Company will recognize any amounts received from Roche in connection with this agreement as an offset to research and development expense within the consolidated statement of operations. During the three and six months ended September 30, 2023 and 2022, the Company did not make any payments to Roche under the terms of the agreement. The Company recorded $1.0 million and $1.7 million as an offset to research and development expenses during the three and six months ended September 30, 2023, respectively. The Company did not record any costs as an offset to research and development expenses during the three and six months ended September 30, 2022. During the six months ended September 30, 2023 and 2022, the Company received payments under the terms of the agreement from Roche of $0.9 million and $0.0 million, respectively. As of September 30, 2023 and March 31, 2023, the Company recorded $1.7 million and $0.9 million as receivables from Roche in connection with this agreement, respectively. Incyte In July 2023, the Company entered into a Clinical Trial Collaboration and Supply Agreement with Incyte Corporation, or Incyte. Under the agreement, the companies will collaborate in a signal finding study in which Incyte will initiate and sponsor a clinical trial of INCB99280 (oral PD-L1 inhibitor) and RP1 in approximately 40 patients with unresectable, high risk CSCC in the neoadjuvant setting. Under the terms of the agreement, the Company will supply Incyte with RP1 for the study and share costs of the study equally with Incyte. The agreement may be terminated by either party upon (i) a material breach not reasonably cured within thirty (30) days; (ii) the discontinuation of development of its clinical drug candidate; (iii) the unethical or illegal business practices of the other party; or (iv) if the parties have not agreed on the protocol or budget within ninety (90) days of the effective date of the agreement. In addition, the Company may terminate the agreement upon the inappropriate or unsafe use of the RP1 product candidate. During the three and six months ended September 30, 2023, the Company did not make any payments to, or receive any payments from, Inctye under the terms of the agreement. Additionally, no costs were recorded to research and development expenses during the three and six months ended September 30, 2023 related to this agreement. Amgen In August 2023 the Company entered into a Settlement Agreement with Amgen and mutually agreed to terminate the Company's challenges to Amgen's patents. In connection with the Settlement Agreement, the Company entered into a License and Covenant Agreement with Amgen in which the Company agreed to pay Amgen low single-digit royalty payments on net sales of its products that, but for the license, could be found to infringe a valid Amgen patent on a country-by-country and product-by-product basis.

Commitments and contingencies - Balance sheet disclosures (Details) $ in Thousands	Sep. 30, 2023 USD ($)
Operating leases
2022 (remaining three months)	$ 568
2025	1,143
2026	1,152
2027	1,120
2028	1,071
Thereafter	1,891
Total lease payments	6,945
Less: interest	1,755
Total lease liabilities	5,190
Financing lease
2022 (remaining three months)	1,335
2025	2,718
2026	2,799
2027	2,883
2028	2,969
Thereafter	35,054
Total lease payments	47,758
Less: interest	21,371
Total lease liabilities	26,387
Total
2022 (remaining three months)	1,903
2025	3,861
2026	3,951
2027	4,003
2028	4,040
Thereafter	36,945
Total lease payments	54,703
Less: interest	23,126
Total lease liabilities	$ 31,577

Stock-based compensation - Additional Information (Details) $ in Millions				1 Months Ended		6 Months Ended
	Apr. 01, 2023 shares	May 31, 2021 shares	Jul. 09, 2018 shares	Sep. 30, 2023 shares	Dec. 31, 2022 shares	Sep. 30, 2023 USD ($) shares	Apr. 01, 2022 shares	Jul. 31, 2017
Stock-Based Compensation
Conversion ratio								1
Granted (in shares)		125,000		125,000	82,500	2,064,526
Value of stock options exercised \| $						$ 1.3
2017 Plan
Stock-Based Compensation
Shares authorized (in shares)				2,659,885		2,659,885
Number of shares available for grant			2,520,247	0		0
2018 Plan
Stock-Based Compensation
Shares authorized (in shares)			3,617,968
Number of shares available for grant				2,064,858		2,064,858
Additional shares authorized (in shares)	2,646,422
Share based payment award percentage of outstanding shares			4.00%
2018 Plan \| Pre-funded warrants
Stock-Based Compensation
Common stock reserved for issuance (in shares)			9,484,238
ESPP
Stock-Based Compensation
Additional shares authorized (in shares)	661,605		697,224
Share based payment award percentage of outstanding shares			1.00%
Common stock reserved for issuance (in shares)	2,738,208		348,612				2,738,208
Stock options
Stock-Based Compensation
Exercise price for persons holding ten percent of voting power (as a percent)				100.00%		100.00%
Exercise price for persons holding more than ten percent of voting power (as a percent)				110.00%		110.00%
Share based payment award expiration period						10 years
Share based payment award vesting period						4 years
Stock options \| Maximum
Stock-Based Compensation
Expiration period for persons holding ten percent of voting power						5 years
Stock options \| Minimum
Stock-Based Compensation
Expiration period for persons holding more than ten percent of voting power						10 years
Restricted stock units
Stock-Based Compensation
Share based payment award vesting period						4 years
Restricted stock unit grant (in shares)						1,216,516
Restricted stock units \| Newly-Hired Executive
Stock-Based Compensation
Restricted stock unit grant (in shares)		88,333		83,330	55,000

Commitments and contingencies

6 Months Ended

Sep. 30, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments and contingencies

Leases

The table below presents the lease-related costs which are included in the consolidated statements of operations for the three and six months ended September 30, 2023 and 2022:


	Three Months Ended September 30,				Six Months Ended September 30,
	2023		2022		2023		2022
Lease cost
Finance lease costs:
Amortization of right-to-use asset	$	607	$	607	$	1,214	$	1,214
Interest on lease liabilities	542		550		1,086		1,102
Operating lease costs	281		252		561		511
Total lease cost	$	1,430	$	1,409	$	2,861	$	2,827

The following table summarizes the classification of lease costs in the consolidated statement of operations for the three and six months ended September 30, 2023 and 2022 as follows:


	Three Months Ended September 30,				Six Months Ended September 30,
	2023		2022		2023		2022
Finance Lease Costs
Research and development	$	607	$	518	$	1,214	$	1,035
Selling, general and administrative	—		89		—		179
Other income (expense)	542		550		1,086		1,102
Operating Lease Costs
Research and development	228		103		457		213
Selling, general and administrative	53		149		104		298
Total lease cost	$	1,430	$	1,409	$	2,861	$	2,827


	September 30, 2023
	Operating leases		Financing lease		Total
2024 (remaining six months)	$	568	$	1,335	$	1,903
2025	1,143		2,718		3,861
2026	1,152		2,799		3,951
2027	1,120		2,883		4,003
2028	1,071		2,969		4,040
Thereafter	1,891		35,054		36,945
Total lease payments	6,945		47,758		54,703
Less: interest	1,755		21,371		23,126
Total lease liabilities	$	5,190	$	26,387	$	31,577

The following table provides lease disclosure as of September 30, 2023 and March 31, 2023:


	September 30, 2023		March 31, 2023
Leases
Right-to-use operating lease asset	$	4,882	$	5,208
Right-to-use finance lease asset	38,451		39,665
Total lease assets	$	43,333	$	44,873

Operating lease liabilities, current	$	1,138	$	1,118
Finance lease liabilities, current	2,678		2,639
Operating lease liabilities, non-current	4,052		4,389
Finance lease liabilities, non-current	23,709		23,965
Total lease liabilities	$	31,577	$	32,111

The following table provides lease disclosure for the three months ended September 30, 2023 and 2022:


	Six Months Ended September 30,
	2023				2022
Other information
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	528			$	466
Operating cash flows from finance leases	$	1,086			$	1,102
Financing cash flows from finance leases	$	217			$	163
Right-to-use asset obtained in exchange for new operating lease liabilities	$	—			$	—
Weighted-average remaining lease term - operating leases	6.1			years	7.1			years
Weighted-average remaining lease term - financing leases	15.8			years	16.8			years
Weighted-average discount rate - operating leases	10.2		%		9.8		%
Weighted-average discount rate - financing leases	8.3		%		8.3		%

The variable lease costs and short-term lease costs were insignificant for the three and six months ended September 30, 2023 and 2022.

Manufacturing commitments

The Company has entered into an agreement with a contract manufacturing organization to provide clinical trial products. As of September 30, 2023 and March 31, 2023, the Company had committed to minimum payments under these arrangements totaling $1.0 million and $1.0 million, respectively.

Indemnification agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its executive management team and its board of directors that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company is not aware of any claims under indemnification arrangements, and therefore it has not accrued any liabilities related to such obligations in its consolidated financial statements as of September 30, 2023 or March 31, 2023.

Legal proceedings

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

Accrued expenses and other current liabilities (Tables)

6 Months Ended

Sep. 30, 2023

Accrued Liabilities and Other Liabilities [Abstract]

Schedule of accrued expenses and other current liabilities

Accrued expenses and other current liabilities consisted of the following:


	September 30, 2023		March 31, 2023
Accrued research and development costs	$	19,945	$	11,261
Accrued compensation and benefits costs	7,128		9,909
Accrued professional fees	687		540
Other	3,891		2,994
Total accrued expenses and other current liabilities	$	31,651	$	24,704

Commitments and contingencies - Additional information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Mar. 31, 2023
Lessee, Lease, Description [Line Items]
Finance Lease Costs	$ 607	$ 607	$ 1,214	$ 1,214
Operating lease costs	281	252	561	511
Minimum payments committed to manufacturing organization	1,000		1,000		$ 1,000
Research and development
Lessee, Lease, Description [Line Items]
Finance Lease Costs	607	518	1,214	1,035
Operating lease costs	228	103	457	213
Selling, general and administrative
Lessee, Lease, Description [Line Items]
Finance Lease Costs	0	89	0	179
Operating lease costs	$ 53	$ 149	$ 104	$ 298

Significant agreements (Details)	1 Months Ended	3 Months Ended		6 Months Ended
Significant agreements (Details)	Jan. 31, 2020 patient	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)
Significant agreements
Research and development		$ 49,101,000	$ 28,834,000	$ 89,538,000	$ 58,312,000
Bristol-Myers Squibb Company
Significant agreements
Number of patients \| patient	125
Regeneron Pharmaceuticals, Inc \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement
Significant agreements
Research and development				0	1,100,000
Proceeds from collaborators				$ 0	$ 2,000,000

Stock-based compensation

6 Months Ended

Sep. 30, 2023

Share-Based Payment Arrangement [Abstract]

Stock-based compensation

Stock-based compensation expense

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


	Three Months Ended September 30,				Six Months Ended September 30,
	2023		2022		2023		2022
Research and development	$	4,447	$	2,529	$	7,745	$	5,143
Selling, general and administrative	4,667		4,463		10,216		9,043
	$	9,114	$	6,992	$	17,961	$	14,186

The following table summarizes stock-based compensation expense by award type for the three and six months ended September 30, 2023 and 2022:


	Three Months Ended September 30,				Six Months Ended September 30,
	2023		2022		2023		2022
Stock options	$	5,688	$	4,845	$	11,302	$	10,004
Restricted stock units	3,426		2,147		6,659		4,182
	$	9,114	$	6,992	$	17,961	$	14,186

2015 Enterprise Management Incentive Share Option Plan

The 2015 Enterprise Management Incentive Share Option Plan of Replimune UK (the “2015 Plan”) provided for Replimune UK to grant incentive stock options, non-statutory stock options, stock awards, stock units, stock appreciation rights and other stock-based awards. Incentive stock options were granted under the 2015 Plan only to the Company’s employees, including officers and directors who were also employees. Non-statutory stock options were granted under the 2015 Plan to employees, members of the board of directors, outside advisors and consultants of the Company.

2017 Equity Compensation Plan

In July 2017, in conjunction with reorganization by Replimune Limited, pursuant to which each shareholder thereof exchanged their outstanding shares in Replimune Limited for shares in Replimune Group, Inc., on a one-for-one basis (the "Reorganization"), the 2015 Plan was terminated, and all awards were cancelled with replacement awards issued under the 2017 Equity Compensation Plan (the “2017 Plan”). Subsequent to the Reorganization, no additional grants have been or will be made under the 2015 Plan and any outstanding awards under the 2015 Plan have continued, and will continue with their original terms. The Company concluded that the cancellation of the 2015 Plan and issuance of replacement awards under the 2017 Plan was a modification with no change in the material rights and preferences and therefore no recorded change in the fair value of each respective award.

The Company’s 2017 Plan provides for the Company to grant incentive stock options or non-statutory stock options, stock awards, stock units, stock appreciation rights and other stock-based awards. Incentive stock options were granted under the 2017 Plan only to the Company’s employees, including officers and directors who were also employees. Restricted stock awards and non-statutory stock options were granted under the 2017 Plan to employees, officers, members of the board of directors, advisors and consultants of the Company. The maximum number of common shares that may be issued under the 2017 Plan was 2,659,885, of which none remained available for future grants as of September 30, 2023. Shares with respect to which awards have expired, terminated, surrendered or cancelled under the 2017 Plan without having been fully exercised will be available for future awards under the 2018 Plan referenced below. In addition, shares of common stock that are tendered to the Company by a participant to exercise an award are added to the number of shares of common stock available for the grant of awards.

2018 Omnibus Incentive Compensation Plan

On July 9, 2018, the Company’s board of directors adopted, and the Company’s stockholders approved the 2018 Omnibus Incentive Compensation Plan (the “2018 Plan”), which became effective immediately prior to the effectiveness of the registration statement filed in connection with the Company’s initial public offering. The 2018 Plan provides for the issuance of incentive stock options, non-qualified stock options, stock awards, stock units, stock appreciation rights and other stock-based awards. The number of shares of common stock initially reserved for issuance under the 2018 Plan is 3,617,968 shares. If any options or stock appreciation rights, including outstanding options and stock appreciation rights granted under the 2017 Plan (up to 2,520,247 shares), terminate, expire, or are canceled, forfeited, exchanged, or surrendered without having been exercised, or if any stock awards, stock units or other stock-based awards, including outstanding awards granted under the 2017 Plan, are forfeited, terminated, or otherwise not paid in full in shares of common stock, the shares of the Company’s common stock subject to such grants will be available for purposes of the 2018 Plan. The number of shares reserved for issuance under the 2018 Plan will increase automatically on the first day of each April equal to 4.0% of the total number of shares of common stock outstanding on the last trading day in the immediately preceding fiscal year, which includes for these purposes, the 9,484,238 shares issuable upon exercise of those pre-funded warrants as of March 31, 2023, as described in Note 9 to these consolidated financial statements, or such lesser amount as determined by the Board. On April 1, 2023, the number of shares reserved for issuance under the 2018 Plan automatically increased by 2,646,422 shares pursuant to the terms of the 2018 Plan and based on total number of shares of common stock outstanding on March 31, 2023. As of September 30, 2023, 2,064,858 shares remained available for future grants under the 2018 Plan.

The 2015 Plan, the 2017 Plan and the 2018 Plan are administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of directors. However, the board of directors shall administer and approve all grants made to non-employee directors. The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, except that the exercise price per share of incentive stock options may not be less than 100% of the fair market value of the common stock on the date of grant (or 110% of fair value in the case of an award granted to employees who hold more than 10% of the total combined voting power of all classes of stock at the time of grant) and the term of stock options may not be greater than five years for an incentive stock option granted to a 10% stockholder and greater than ten years for all other options granted. Stock options awarded under both plans expire ten years after the grant date, unless the board of directors sets a shorter term. Vesting periods for the plans are determined at the discretion of the board of directors. Incentive stock options granted to employees and non-statutory options granted to employees, officers, members of the board of directors, advisors, and consultants of the Company typically vest over four years. In 2021 the board of directors initiated the award of restricted stock units ("RSUs"), under the 2018 Plan in addition to stock option awards available as part of the Company's equity incentive for employees, officers, advisors and consultants of the Company. The RSUs typically vest over four approximately equal annual installments with the first such installment occurring on a designated vesting date that is approximately on the one-year anniversary of the date of grant and the subsequent installments occurring on the subsequent three annual anniversaries of the designated vesting date.

Employee Stock Purchase Plan

On July 9, 2018, the Company’s board of directors adopted and the Company’s stockholders approved the Employee Stock Purchase Plan (the “ESPP”), which became effective immediately prior to the effectiveness of the registration statement that was filed in connection with the Company’s IPO. The total shares of common stock initially reserved for issuance under the ESPP is 348,612 shares. In addition, as of the first trading day of each fiscal year during the term of the ESPP (excluding any extensions), an additional number of shares of the Company’s common stock equal to 1% of the total number of shares outstanding on the last trading day in the immediately preceding fiscal year, which includes for these purposes, the 9,484,238 shares issuable upon exercise of those pre-funded warrants described in Note 9 to these consolidated financial statements, or 697,224 shares, whichever is less (or such lesser amount as determined by the Company’s board of directors) will be added to the number of shares authorized under the ESPP. In accordance with the terms of the ESPP, on April 1, 2023, the number of shares reserved for issuance under the ESPP automatically increased by 661,605, for a total of 2,738,208 shares reserved for the ESPP. If the total number of shares of common stock to be purchased pursuant to outstanding purchase rights on any particular date exceed the number of shares then available for issuance under the ESPP, then the plan administrator will allocate the available shares pro-rata and refund any excess payroll deductions or other contributions to participants. The Company’s ESPP is not currently active.

Out-of-Plan Inducement Grants

In May 2021, the Company granted an equity award to a newly hired executive as a material inducement to enter into employment with the Company. The grant constitutes an "employment inducement grant" in accordance with Rule 5635(c)(4) of the Nasdaq Listing Rules and was issued outside of the 2018 Plan and each of the other stock incentive plans described above. The inducement grant included a nonqualified stock option to purchase up to 125,000 shares of the Company's common stock, as well as a restricted stock unit grant representing 88,333 shares of the Company's common stock. These stock option

and restricted stock unit inducement grants have terms and conditions consistent with those set forth under the 2018 Plan and vest under the same respective vesting schedules as stock option and restricted stock unit awards granted under the 2018 Plan. The inducement grant is included in the stock option and RSU award tables below.

In December 2022, the Company granted an equity award to a newly hired executive as a material inducement to enter into employment with the Company. The grant constitutes an "employment inducement grant" in accordance with Rule 5635(c)(4) of the Nasdaq Listing Rules and was issued outside of the 2018 Plan and each of the other stock incentive plans described above. The inducement grant included a nonqualified stock option to purchase up to 82,500 shares of the Company's common stock, as well as a restricted stock unit grant representing 55,000 shares of the Company's common stock. These stock option and restricted stock unit inducement grants have terms and conditions consistent with those set forth under the 2018 Plan and vest under the same respective vesting schedules as stock option and restricted stock unit awards granted under the 2018 Plan. The inducement grant is included in the stock option and RSU award tables below.

In September 2023, the Company granted an equity award to a newly hired executive as a material inducement to enter into employment with the Company. The grant constitutes an "employment inducement grant" in accordance with Rule 5635(c)(4) of the Nasdaq Listing Rules and was issued outside of the 2018 Plan and each of the other stock incentive plans described above. The inducement grant included a nonqualified stock option to purchase up to 125,000 shares of the Company's common stock, as well as a restricted stock unit grant representing 83,330 shares of the Company's common stock. These stock option and restricted stock unit inducement grants have terms and conditions consistent with those set forth under the 2018 Plan and vest under the same respective vesting schedules as stock option and restricted stock unit awards granted under the 2018 Plan. The inducement grant is included in the stock option and RSU award tables below.

Stock option valuation

The fair value of stock option grants is estimated using the Black-Scholes option-pricing model. As the Company has limited company-specific historical and implied volatility information, the expected stock volatility is based on a combination of Replimune volatility and the historical volatility of a publicly traded set of peer companies. For options with service-based vesting conditions, the expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The expected term of stock options granted to non-employees is equal to the contractual term of the option award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

The following table presents, on a weighted-average basis, the assumptions that the Company used to determine the grant-date fair value of stock options granted to employees and directors:


	Three Months Ended September 30,				Six Months Ended September 30,
	2023		2022		2023		2022
Risk-free interest rate	4.34	%	3.08	%	3.69	%	2.61	%
Expected term (in years)	6.1		6.1		6.0		6.0
Expected volatility	72.7	%	74.5	%	73.9	%	75.5	%
Expected dividend yield	0	%	0	%	0	%	0	%

Stock options

The following table summarizes the Company’s stock option activity:


	Number of Shares	Weighted Average Exercise Price		Weighted Average Contractual Term (Years)	Aggregate Intrinsic Value
Outstanding as of March 31, 2023	7,454,828	$	17.24	6.88	$	31,244
Granted	2,064,526	$	18.08
Exercised	(163,356)	$	10.76
Cancelled	(200,611)	$	24.73
Outstanding as of September 30, 2023	9,155,387	$	17.38	6.78	$	27,858
Options exercisable as of September 30, 2023	5,400,346	$	15.28	5.60	$	26,556
Options vested and expected to vest as of September 30, 2023	9,155,387	$	17.38	6.78	$	27,858

As of September 30, 2023, there was $46.4 million of unrecognized compensation cost related to unvested common stock options, which is expected to be recognized over a weighted average period of 2.7 years.

The weighted average grant-date fair value of stock options granted during the six months ended September 30, 2023 and 2022 was $12.19 and $12.20, respectively. The aggregate intrinsic value of stock options exercised during the six months ended September 30, 2023 was $1.3 million.

Restricted stock units

A summary of the changes in the Company's RSUs during the three months ended September 30, 2023 is as follows:


	Number of Restricted Shares	Weighted Average Grant Date Fair Value
Outstanding as of March 31, 2023	1,351,280	24.38
Granted	1,216,516	18.11
Vested	(297,019)	25.36
Cancelled	(80,940)	21.70
Outstanding as of September 30, 2023	2,189,837	20.86

As of September 30, 2023, there was $39.4 million of unrecognized compensation cost related to unvested restricted stock units, which is expected to be recognized over a weighted average period of 3.0 years.

Short-term investments (Tables)

6 Months Ended

Sep. 30, 2023

Short-Term Investments [Abstract]

Schedule of short-term investments

As of September 30, 2023 and March 31, 2023, the Company's available-for-sale investments by type consisted of the following:


	September 30, 2023
	Amortized cost		Gross unrealized gains		Gross unrealized losses		Credit Losses		Fair value
US Government agency bonds	$	266,452	$	68	$	(264)	$	—	$	266,256
US Treasury bonds	154,620		1		(112)		—		154,509
Total	$	421,072	$	69	$	(376)	$	—	$	420,765


	March 31, 2023
	Amortized cost		Gross unrealized gains		Gross unrealized losses		Credit Losses		Fair value
US Government agency bonds	240,371		187		(203)		$	—	240,355
US Treasury bonds	196,488		77		(124)		—		196,441
Total	$	436,859	$	264	$	(327)	$	—	$	436,796

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
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-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

+ Details

Stockholders' equity - Schedule of Pre-funded Warrants (Details) - shares	Sep. 30, 2023	Mar. 31, 2023	Dec. 01, 2022
Stock options, issued and outstanding
Class of Warrant or Right [Line Items]
Issuance of pre-funded warrants (in shares)	9,155,387	7,454,828
Restricted stock units
Class of Warrant or Right [Line Items]
Issuance of pre-funded warrants (in shares)	2,189,837	1,351,280
Stock options and restricted stock units, future issuance
Class of Warrant or Right [Line Items]
Issuance of pre-funded warrants (in shares)	2,064,858	2,209,597
Employee stock purchase plan, available for future grants
Class of Warrant or Right [Line Items]
Issuance of pre-funded warrants (in shares)	2,738,208	2,076,603
Pre-IPO warrants to purchase common stock
Class of Warrant or Right [Line Items]
Issuance of pre-funded warrants (in shares)	497,344	497,344
Pre-funded warrants
Class of Warrant or Right [Line Items]
Issuance of pre-funded warrants (in shares)	7,561,583	9,484,238	4,200,000,000
Total shares of common stock reserved for future issuance
Class of Warrant or Right [Line Items]
Issuance of pre-funded warrants (in shares)	24,207,217	23,073,890

Property, plant and equipment, net (Tables)

6 Months Ended

Sep. 30, 2023

Property, Plant and Equipment [Abstract]

Schedule of property, plant and equipment, net

Property, plant and equipment, net consisted of the following:


	September 30, 2023		March 31, 2023
Office equipment	$	1,397	$	1,240
Computer equipment	1,846		1,806
Plant and laboratory equipment	9,706		9,186
Leasehold improvements	1,842		1,706
Capitalized software	724		—
Construction in progress	1,447		783
Total property, plant and equipment	16,962		14,721
Less: Accumulated depreciation	(8,517)		(7,242)
Property, plant and equipment, net	$	8,445	$	7,479

Stock-based compensation - Summary of RSU Activity (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Sep. 30, 2023
Restricted stock units
Number of Restricted Shares
Outstanding as of March 31, 2021 (in shares)	1,351,280
Granted (in shares)	1,216,516
Vested (in shares)	(297,019)
Cancelled (in shares)	(80,940)
Outstanding as of June 30, 2021 (in shares)	2,189,837
Weighted Average Grant Date Fair Value
Outstanding as of March 31, 2021 (in dollars per share)	$ 24.38
Granted (in dollars per share)	18.11
Vested (in dollars per share)	25.36
Cancelled (in dollars per share)	21.70
Outstanding as of June 30, 2021 (in dollars per share)	$ 20.86
Total unrecognized compensation cost	$ 39.4
Expenses expected to be recognized over a weighted average remaining period	3 years
Stock options
Weighted Average Grant Date Fair Value
Total unrecognized compensation cost	$ 46.4
Expenses expected to be recognized over a weighted average remaining period	2 years 8 months 12 days

Nature of the business (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
Nature of the business (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Jun. 30, 2023	Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Mar. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net loss	$ (60,044)	$ (49,555)	$ (43,102)	$ (42,253)	$ (109,599)	$ (85,355)
Accumulated deficit	$ (595,087)				$ (595,087)		$ (485,488)

- Definition

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

+ References

+ Details

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Commitments and contingencies - Components of lease expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Finance lease costs:
Amortization of right-to-use asset	$ 607	$ 607	$ 1,214	$ 1,214
Interest on lease liabilities	542	550	1,086	1,102
Operating lease costs	281	252	561	511
Total lease cost	$ 1,430	$ 1,409	$ 2,861	$ 2,827

Net loss per share - Computation of Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Numerator:
Net loss	$ (60,044)	$ (43,102)	$ (109,599)	$ (85,355)
Denominator:
Weighted average common shares outstanding, basic (in shares)	66,582,280	54,770,291	66,475,577	54,492,395
Weighted average common shares outstanding, diluted (in shares)	66,582,280	54,770,291	66,475,577	54,492,395
Net loss per share attributable to common stockholders, diluted (in dollars per share)	$ (0.90)	$ (0.79)	$ (1.65)	$ (1.57)
Net loss per share attributable to common stockholders, basic (in dollars per share)	$ (0.90)	$ (0.79)	$ (1.65)	$ (1.57)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

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

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

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+ Details

- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

+ References

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

Stockholders' equity - Common Stock and Undesignated Preferred Stock (Details) - $ / shares	Sep. 30, 2023	Mar. 31, 2023
Stockholders' Equity Note [Abstract]
Common stock, authorized (in shares)	150,000,000	150,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Undesignated preferred stock, authorized (in shares)	10,000,000
Preferred stock, Par Value (in dollars per share)	$ 0.001
Undesignated preferred shares issued (in shares)	0

Geographic information

6 Months Ended

Sep. 30, 2023

Segments, Geographical Areas [Abstract]

Geographic information

Geographic informationThe Company operates in two geographic regions: the United States (Massachusetts) and the United Kingdom (Oxfordshire). Information about the Company’s long-lived assets held in different geographic regions is presented in the tables below:


	September 30, 2023		March 31, 2023
United States	$	6,559	$	5,836
United Kingdom	1,886		1,643
	$	8,445	$	7,479

Stockholders' equity - ATM Program (Details) - USD ($) $ / shares in Units, $ in Millions				1 Months Ended	3 Months Ended		6 Months Ended
	Aug. 03, 2023	Jun. 23, 2022	Aug. 11, 2020	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2022	Sep. 30, 2023	Mar. 31, 2023
Class of Warrant or Right [Line Items]
Common stock, par value (in dollars per share)								$ 0.001	$ 0.001
Number of shares issued (in shares)				6,810,658,000
Shares issued during period (in shares)					340,000		340,000
Proceeds from issuance of common stock through ATM sales, net of offering costs				$ 242.6	$ 6.7		$ 6.7
Issuance costs and underwriter fees					$ 0.3		$ 0.3
Common stock
Class of Warrant or Right [Line Items]
Shares issued during period (in shares)					340,000	1,686,438
ATM Program
Class of Warrant or Right [Line Items]
Percentage of commission			3.00%
ATM Program \| Common stock
Class of Warrant or Right [Line Items]
Aggregate offering amount					$ 32.0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001
Number of shares issued (in shares)					1,686,438
Underwriting discounts, commissions and other offering expenses					$ 1.0
Maximum received on transaction	$ 250.0	$ 100.0
ATM Program \| Maximum \| Common stock
Class of Warrant or Right [Line Items]
Aggregate offering amount			$ 62.5

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Operating expenses:
Research and development	$ 49,101	$ 28,834	$ 89,538	$ 58,312
Selling, general and administrative	14,730	12,745	29,941	24,143
Total operating expenses	63,831	41,579	119,479	82,455
Loss from operations	(63,831)	(41,579)	(119,479)	(82,455)
Other income (expense):
Research and development incentives	443	574	836	1,425
Investment income	6,049	1,112	12,235	1,455
Interest expense on finance lease liability	(542)	(550)	(1,086)	(1,102)
Interest expense on debt obligations	(955)	0	(2,070)	0
Other (expense) income	(1,409)	(2,659)	(35)	(4,678)
Total other income (expense), net	3,586	(1,523)	9,880	(2,900)
Loss before income taxes	(60,245)	(43,102)	(109,599)	(85,355)
Income tax (benefit)	(201)	0	0	0
Net loss	$ (60,044)	$ (43,102)	$ (109,599)	$ (85,355)
Net loss per share attributable to common stockholders, basic (in dollars per share)	$ (0.90)	$ (0.79)	$ (1.65)	$ (1.57)
Net loss per share attributable to common stockholders, diluted (in dollars per share)	$ (0.90)	$ (0.79)	$ (1.65)	$ (1.57)
Weighted average common shares outstanding, basic (in shares)	66,582,280	54,770,291	66,475,577	54,492,395
Weighted average common shares outstanding, diluted (in shares)	66,582,280	54,770,291	66,475,577	54,492,395

Debt - Narrative (Details)			3 Months Ended		6 Months Ended
Debt - Narrative (Details)	Jun. 28, 2023 USD ($)	Oct. 06, 2022 USD ($) advance	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Jun. 27, 2023 USD ($)	Mar. 31, 2023 USD ($)
Debt Instrument [Line Items]
Unrestricted cash percentage			35.00%		35.00%
Interest expense on debt obligations			$ (955,000)	$ 0	$ (2,070,000)	$ 0
Secured Debt \| Line of Credit \| Term Loan Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 200,000,000
Additional rate (as a percent)		1.75%
Stated interest rate (as a percent)		1.50%
Prepayment fee, first 12 months (as a percent)		3.00%
Prepayment fee, After first 12 months before 36 months (as a percent)		2.00%
Prepayment fee, after 36 months (as a percent)		1.00%
Maximum amount outstanding for covenant		$ 100,000,000
Minimum market capitalization		$ 1,200,000,000
Minimum restricted cash (as a percent)		50.00%
Minimum unrestricted cash (as a percent)		85.00%
Facility charge		$ 500,000
Payment of issuance costs		$ 1,500,000
Repayment Fee (as a percent)		4.95%
Accrued for final payment on debt			300,000		300,000			$ 200,000
Unamortized deferred financing costs			100,000		100,000
Interest expense on debt obligations			$ (1,000,000)		$ (2,100,000)
Secured Debt \| Line of Credit \| Term Loan Facility \| Prime Rate
Debt Instrument [Line Items]
Variable rate (as a percent)		7.25%
Secured Debt \| Line of Credit \| Term Loan Facility \| Maximum \| Prime Rate
Debt Instrument [Line Items]
Variable rate (as a percent)		7.25%
Secured Debt \| Line of Credit \| Term Loan Facility, Tranche One
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 30,000,000
Secured Debt \| Line of Credit \| Term Loan Facility, Tranche Two
Debt Instrument [Line Items]
Maximum borrowing capacity		30,000,000					$ 15,000,000
Secured Debt \| Line of Credit \| Term Loan Facility, Tranche Three
Debt Instrument [Line Items]
Maximum borrowing capacity		115,000,000
Secured Debt \| Line of Credit \| Term Loan Facility, Tranche Four
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 25,000,000
Number of term loan advances \| advance		2
Secured Debt \| Line of Credit \| Term Loan Facility, Tranche Five
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 25,000,000
Number of term loan advances \| advance		2
Secured Debt \| Line of Credit \| Term Loan Facility, Tranche One and Two
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 60,000,000
Decrease in borrowing capacity	$ 30,000,000
Secured Debt \| Line of Credit \| Term Loan Facility, Tranche Two, Amendment
Debt Instrument [Line Items]
Maximum borrowing capacity	45,000,000
Decrease in borrowing capacity	$ 30,000,000

Accrued expenses and other current liabilities

6 Months Ended

Sep. 30, 2023

Accrued Liabilities and Other Liabilities [Abstract]

Accrued expenses and other current liabilities

Accrued expenses and other current liabilities consisted of the following:


	September 30, 2023		March 31, 2023
Accrued research and development costs	$	19,945	$	11,261
Accrued compensation and benefits costs	7,128		9,909
Accrued professional fees	687		540
Other	3,891		2,994
Total accrued expenses and other current liabilities	$	31,651	$	24,704

Geographic information (Tables)

6 Months Ended

Sep. 30, 2023

Segments, Geographical Areas [Abstract]

Summary of company's long-lived assets held in different geographic regions

The Company operates in two geographic regions: the United States (Massachusetts) and the United Kingdom (Oxfordshire). Information about the Company’s long-lived assets held in different geographic regions is presented in the tables below:


	September 30, 2023		March 31, 2023
United States	$	6,559	$	5,836
United Kingdom	1,886		1,643
	$	8,445	$	7,479

Income taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Income taxes (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Income tax benefit	$ (201)	$ 0	$ 0	$ 0

- Definition

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

+ References + Details

Stock-based compensation - Stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended		6 Months Ended	12 Months Ended
	May 31, 2021	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Mar. 31, 2023
Number of Shares
Outstanding at beginning of the period (in shares)						7,454,828
Granted (in shares)	125,000	125,000	82,500			2,064,526
Exercised (in shares)						(163,356)
Cancelled (in shares)						(200,611)
Outstanding at end of the period (in shares)		9,155,387		9,155,387		9,155,387	7,454,828
Options exercisable (in shares)		5,400,346		5,400,346		5,400,346
Options vested and expected to vest (in shares)						9,155,387
Weighted Average Exercise Price
Outstanding at beginning of the period (in dollars per share)						$ 17.24
Granted (in dollars per share)						18.08
Exercised (in dollars per share)						10.76
Cancelled (in dollars per share)						24.73
Outstanding at end of the period (in dollars per share)		$ 17.38		$ 17.38		17.38	$ 17.24
Options exercisable (in dollars per share)		15.28		15.28		15.28
Options vested and expected to vest (in dollars per share)		$ 17.38		$ 17.38		$ 17.38
Weighted Average Contractual Term (Years)
Outstanding (years)						6 years 9 months 10 days	6 years 10 months 17 days
Options exercisable (years)						5 years 7 months 6 days
Options vested and expected to vest (years)						6 years 9 months 10 days
Aggregate Intrinsic Value
Outstanding		$ 27,858		$ 27,858		$ 27,858	$ 31,244
Options exercisable		26,556		26,556		26,556
Options vested and expected to vest		27,858		$ 27,858		27,858
Stock-Based Compensation
Weighted average grant-date fair value per share of stock options granted				$ 12.19	$ 12.20
Stock options
Stock-Based Compensation
Total unrecognized compensation cost		$ 46,400		$ 46,400		$ 46,400
Expenses expected to be recognized over a weighted average remaining period						2 years 8 months 12 days