Nature of the business	3 Months Ended
Nature of the business	Jun. 30, 2025
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 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 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 revenue from product sales. The Company's proprietary oncolytic immunotherapy product candidates, the RPx product candidates, are based on a novel, engineered strain of herpes simplex virus 1, or HSV-1, backbone with added payloads intended to maximize immunogenic cell death and the induction of a systemic anti-tumor immune response. The Company currently has three RPx product candidates, RP1, RP2 and RP3. RP1 is currently under development in multiple clinical trials, the most advanced being the anti-PD1 failed melanoma cohort of the IGNYTE clinical trial. 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 $86.7 million and $53.8 million for the three months ended June 30, 2025 and 2024, respectively. In addition, as of June 30, 2025, the Company had an accumulated deficit of $1,035.3 million. The Company expects to continue to generate operating losses for the foreseeable future and to finance its future cash needs through a combination of equity offerings, debt financings, collaborations, strategic partnerships and alliances or licensing arrangements. If the Company is unable to obtain funding, the Company would be forced to delay, reduce or eliminate some or all of its research and development programs, preclinical and clinical testing or commercialization efforts, which could adversely affect its business prospects. The Company expects that its cash and cash equivalents and short-term investments will be sufficient to fund its operations through at least 12 months from the issuance of these consolidated financial statements, which includes the potential commercialization of RP1 in skin cancers and for working capital and general corporate purposes and excludes any potential revenue. These estimates are based on assumptions that may prove to be wrong, including the assumption that the development of RP1 will remain viable, and the Company could utilize its available capital resources sooner than expected.