Replimune Group’s application for approval of RP1, a viral-based treatment for advanced melanoma, was rejected by the FDA for inadequate and uncontrolled clinical investigation and trial design issues. The agency cited the heterogeneity of the patient population as a confounding factor. The decision coincided with a significant stock price drop, plummeting over 75%, reflecting investor concerns over FDA’s increasingly stringent review standards. The rejection underscores heightened regulatory scrutiny for cell and gene therapies under FDA leadership.