Key Takeaways
- FDA issued a second complete response letter denying approval for Replimune’s RP1 melanoma immunotherapy
- The treatment was under evaluation as a combination therapy with Bristol Myers Squibb’s (BMY) Opdivo
- Regulatory concerns centered on trial design being deemed insufficient and lacking proper controls
- REPL shares plummeted approximately 19% to $4.76, with trading halted twice due to excessive volatility
- Share price now sits significantly below the 52-week peak of $13.24
Replimune (REPL) has encountered a significant regulatory roadblock after the FDA delivered a second rejection for its RP1 therapeutic candidate, maintaining its position that the supporting clinical trial framework was fundamentally flawed.
The regulatory agency delivered a complete response letter refusing authorization for RP1, scientifically designated as vusolimogene oderparepvec, which was intended for use in combination with Bristol Myers Squibb’s (BMY) Opdivo for treating advanced melanoma in patients who had already undergone anti-PD-1 therapy.
In correspondence directed to Kari Jeschke, Replimune’s senior vice president of regulatory affairs, the FDA stated that supplementary exploratory data analysis failed to change its previous determination. The agency concluded that the RPL-001-16 clinical study did not constitute an adequate and well-controlled investigation.
Notably, the FDA expressed no safety reservations about the drug — the central obstacle continues to be the quality of efficacy data.
This marks the second regulatory denial. The initial rejection occurred in July 2025, coming two months following Vinay Prasad’s appointment as head of the FDA’s Center for Biologics Evaluation and Research. Following this, Replimune resubmitted its Biologics License Application, receiving acceptance for review in October 2025.
REPL stock declined roughly 19% to reach $4.76 following the announcement. Market volatility triggered two trading suspensions during the session. This price level positions the stock toward its weakest closing point since October, based on Dow Jones Market Data.
Trading at $4.76, REPL remains substantially beneath its 52-week maximum of $13.24.
Understanding RP1
RP1 represents a bioengineered variant of Herpes Simplex Virus type 1 — the identical pathogen responsible for cold sores. Replimune engineered it to reproduce exclusively within cancerous cells, destroying them while simultaneously activating a heightened immune system response through white blood cell engagement.
The therapy serves as the flagship product within Replimune’s RPx platform, which specializes in oncolytic immunotherapy development targeting solid malignancies.
The biotechnology firm currently maintains a market capitalization of approximately $393 million. Without positive earnings, no P/E ratio exists — a typical characteristic for clinical-stage biotech companies still advancing their therapeutic pipelines.
Insider Transactions and Company Financials
Replimune’s GF Score registers at 40 out of 100, with profitability metrics earning merely 1 out of 10. The company’s financial strength assessment scores 6 out of 10.
During the previous three-month period, company insiders divested $0.1 million in shares, while no insider buying activity was documented.
Shares currently trade at $4.76, substantially under the yearly high of $13.24 achieved earlier this year.
