Replimune Group Inc. (NASDAQ: REPL) received a complete response letter from the U.S. Food and Drug Administration rejecting its biologics license application for RP1 in combination with nivolumab for treating advanced melanoma.

The FDA's decision contradicts positions expressed at a September 2025 meeting, according to the company. Replimune stated a different review team was appointed for the resubmission, replacing the prior team that had interacted with the company throughout the process.

The company's IGNYTE trial showed patients with confirmed progression on anti-PD-1 therapy who received RP1 plus nivolumab had a 34% response rate with a median duration of 24.8 months. The FDA had previously granted the application breakthrough therapy designation and priority review.

"Without timely accelerated approval, the development of RP1 will not be viable," said CEO Sushil Patel. The company plans to eliminate jobs and scale back U.S. manufacturing operations.

RP1, also known as vusolimogene oderparepvec, is based on a genetically engineered herpes simplex virus designed to kill tumor cells and activate immune responses. The FDA had previously suggested in 2021 that a single-arm trial could be acceptable for accelerated approval consideration if data was compelling enough.

Melanoma affects approximately 112,000 new cases annually in the U.S. and causes about 8,500 deaths per year. Standard immune checkpoint therapy fails to help roughly half of patients who either don't respond or experience disease progression.

Replimune had initiated a Phase 3 confirmatory trial called IGNYTE-3 based on FDA feedback regarding accelerated approval requirements.