Nature of the business	12 Months Ended
Mar. 31, 2026
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 committed to applying our leading expertise in the field of oncolytic immunotherapy to transform the lives of cancer patients through our novel oncolytic immunotherapies. 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, 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 $313.9 million and $247.3 million for the years ended March 31, 2026 and 2025, respectively. In addition, as of March 31, 2026, the Company had an accumulated deficit of $1,262.5 million. In accordance with ASC 205-40, Presentation of Financial Statements—Going Concern, management has evaluated whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the Company's ability to continue as a going concern within one year after the date these consolidated financial statements are issued. Based on its current operating plan, the Company expects to continue to generate operating losses for the foreseeable future and that its existing cash, cash equivalents and short-term investments will be sufficient to fund its operating expenses and capital expenditure requirements only into the first calendar quarter of 2027, which is less than one year from the date these consolidated financial statements are issued. The Company does not have any committed source of additional funding and will be required to obtain additional financing to fund its operations beyond that date. These conditions raise substantial doubt about the Company's ability to continue as a going concern. The Company is collaborating with the FDA regarding a path forward for RP1 and, if the BLA is approved, the Company will determine the best source of capital, which may be raising additional capital through public or private equity offerings (including under our at-the-market facilities), although there can be no guarantee that the Company will be able to raise such capital on acceptable terms, or at all. If the BLA is not approved, the Company will likely need to (i) execute a considerable restructuring and workforce reduction to reduce our cash burn, (ii) reconsider our product development efforts and strategies and (iii) pursue collaborations, strategic alliances, licensing arrangements, business combination, merger or acquisition, or other strategic business development activities to continue operations. In either scenario, our plans are subject to risks and uncertainties, including factors outside our control. Accordingly, we have not been able to conclude that these plans are probable of being effectively implemented and, as such, they do not alleviate the substantial doubt about our ability to continue as a going concern.

Nature of the business

12 Months Ended

Mar. 31, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Replimune Group, Inc. (the “Company”) is a clinical-stage biotechnology company committed to applying our leading expertise in the field of oncolytic immunotherapy to transform the lives of cancer patients through our novel oncolytic immunotherapies. 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, 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 $313.9 million and $247.3 million for the years ended March 31, 2026 and 2025, respectively. In addition, as of March 31, 2026, the Company had an accumulated deficit of $1,262.5 million.

In accordance with ASC 205-40, Presentation of Financial Statements—Going Concern, management has evaluated whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the Company's ability to continue as a going concern within one year after the date these consolidated financial statements are issued. Based on its current operating plan, the Company expects to continue to generate operating losses for the foreseeable future and that its existing cash, cash equivalents and short-term investments will be sufficient to fund its operating expenses and capital expenditure requirements only into the first calendar quarter of 2027, which is less than one year from the date these consolidated financial statements are issued. The Company does not have any committed source of additional funding and will be required to obtain additional financing to fund its operations beyond that date. These conditions raise substantial doubt about the Company's ability to continue as a going concern.

The Company is collaborating with the FDA regarding a path forward for RP1 and, if the BLA is approved, the Company will determine the best source of capital, which may be raising additional capital through public or private equity offerings (including under our at-the-market facilities), although there can be no guarantee that the Company will be able to raise such capital on acceptable terms, or at all. If the BLA is not approved, the Company will likely need to (i) execute a considerable restructuring and workforce reduction to reduce our cash burn, (ii) reconsider our product development efforts and strategies and (iii) pursue collaborations, strategic alliances, licensing arrangements, business combination, merger or acquisition, or other strategic business development activities to continue operations. In either scenario, our plans are subject to risks and uncertainties, including factors outside our control. Accordingly, we have not been able to conclude that these plans are probable of being effectively implemented and, as such, they do not alleviate the substantial doubt about our ability to continue as a going concern.