The U.S. Food and Drug Administration rejected Replimune Group’s application for accelerated approval of RP1, an oncolytic virus given with Bristol Myers Squibb’s Opdivo to treat advanced melanoma. In a Complete Response Letter dated 22 July, the agency said the single-arm IGNYTE study supporting the filing was neither adequate nor well-controlled and could not be reliably interpreted because of the heterogeneity of the 140-patient population. No safety concerns were cited, but regulators also raised questions about the design of the ongoing confirmatory Phase 3 IGNYTE-3 trial. Replimune said it will request a Type A meeting within 30 days to discuss a path forward and plans to address the FDA’s concerns over study design and component contribution. Chief Executive Officer Sushil Patel called the decision a surprise, noting that the disputed issues had not arisen during earlier interactions with the agency. Investors punished the stock, sending Replimune shares down roughly 75 % in early trading to about $3, their lowest level since the company went public in 2018. Analysts said the setback adds to evidence that the FDA’s new leadership is taking a tougher line on cell and gene therapy approvals, raising the bar for single-arm studies seeking accelerated clearance.