Replimune Group’s oncolytic virus therapy RP1, intended for advanced melanoma treatment, received a complete response letter from the FDA citing inadequate trial design and heterogeneity of patient populations, leading to rejection of the Biologics License Application. The FDA questioned the confirmatory trial design and evidentiary basis. Replimune expressed surprise at the decision, which caused the company’s shares to decrease by 75%. This reflects a stricter regulatory environment for cell and gene therapies under new FDA leadership.