08:53 AM EDT, 07/22/2025 (MT Newswires) -- Replimune Group ( REPL ) said Tuesday the US Food and Drug Administration has declined to approve its biologics license application for its experimental drug, RP1 combined with nivolumab, to treat advanced melanoma, citing concerns with the study.

Replimune ( REPL ) shares were more than 77% lower in premarket trading.

The company said the FDA raised concerns that the trial supporting the application was not an adequate and well-controlled clinical investigation, and heterogeneity of the patient population made results hard to interpret.

Replimune ( REPL ) said that while no safety issues were noted, the FDA raised concerns about the confirmatory trial's design, including how each treatment component contributes to its effectiveness.

Replimune ( REPL ) said it plans to request a type A meeting with the FDA, which it expects to be granted within 30 days, and that it intends to work with the agency on a path forward, warning that without accelerated approval, RP1's development for this patient group may no longer be feasible.