Replimune stock tumbles 20% after FDA raises efficacy concerns

Investing.com -- Replimune Group Inc. (NASDAQ: REPL) shares fell 20% Tuesday after the FDA released briefing documents ahead of a Cellular, Tissue, and Gene Therapies Advisory Committee meeting scheduled for July 30.

The FDA documents outlined significant review issues regarding Replimune's biologics license application for vusolimogene oderparepvec, also known as RP1, in combination with nivolumab for treating adult patients with unresectable advanced cutaneous melanoma who progressed on prior PD-1-blocking antibody therapy.

The FDA identified three key concerns with the IGNYTE study, which forms the basis for the application. First, the agency stated that Replimune's application of RECIST v1.1 criteria for response assessment "confounds interpretation of the reported efficacy results and limits FDA's ability to verify the reported results."

Second, the FDA noted that objective response data from the single-arm IGNYTE study "are not of sufficient magnitude to overcome concerns about the contribution of effect" and that "it cannot be determined whether RP1 contributes to any observed effect when administered in combination with nivolumab," particularly in the absence of a reliable historical control.

Third, the agency stated that the overall survival analysis from the single-arm IGNYTE study "is not interpretable."

The IGNYTE study enrolled 140 patients with unresectable Stage IIIB to IV cutaneous melanoma who had confirmed disease progression after at least 8 weeks of anti-PD-1 therapy. The primary endpoint was objective response rate based on RECIST v1.1 criteria assessed by blinded independent review committee.

The FDA had previously recommended that Replimune conduct a randomized trial to establish the contribution of RP1 when added to nivolumab, but the company proceeded with the application based on the single-arm study.

The advisory committee meeting will publicly discuss these review issues on July 30, 2026.

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