Shares of Replimune Group (REPL) surged approximately 85% on Friday, reaching $8.64, after the company announced a breakthrough with the U.S. Food and Drug Administration (FDA) regarding its experimental advanced melanoma therapy, RP1. The FDA has agreed to a priority review for the drug, which had been previously rejected in April due to a lack of a control group in clinical trials.
The Woburn, Massachusetts-based biotechnology firm stated that it will resubmit its Biologics License Application (BLA) for RP1 within the coming days. The FDA's decision to grant priority review underscores the significant unmet medical need in treating advanced melanoma, a severe form of skin cancer.
This development marks a dramatic turnaround for Replimune, which had faced a setback just weeks earlier when regulators declined to approve the therapy. The stock's rally reflects renewed investor optimism, shifting the focus from previous approval concerns to the timeline and evidence required for the FDA's new assessment.
Replimune CEO Sushil Patel expressed gratitude toward FDA leadership for their collaborative approach in advancing RP1. The therapy, known as vusolimogene oderparepvec, is an oncolytic immunotherapy that employs a modified virus to target cancer cells and stimulate the immune system's response.
The initial rejection in April stemmed from the FDA's demand for more robust data from a well-controlled trial, as Replimune had only provided results from a single-arm study. The company is currently evaluating RP1 in combination with nivolumab, the generic version of Bristol Myers Squibb's (BMY) Opdivo, in patients with advanced melanoma who have not responded to anti-PD-1 therapies.
Market analysts remain cautiously optimistic. BMO Capital analyst Evan Seigerman noted the positive shift but expressed uncertainty about what specifically changed beyond FDA leadership. The company's IGNYTE trial had previously demonstrated a 34% response rate and a median response duration of 24.8 months for patients receiving RP1 with nivolumab after anti-PD-1 treatment failure.
Replimune is set to present additional data at the American Society of Clinical Oncology (ASCO) meeting on May 30, including three-year overall survival results from the IGNYTE study. A poster for its Phase 3 IGNYTE-3 study will follow on May 31.
The competitive landscape in advanced melanoma includes Bristol Myers, which saw its shares decline 0.6%, and Iovance Biotherapeutics (IOVA), whose stock dropped 6.5% on Friday. Iovance's approved therapy, Amtagvi, faces potential competition from RP1 if approved.
Despite the positive momentum, the path to approval remains uncertain. The FDA's priority review does not guarantee eventual clearance. If regulators again question the trial design or demand randomized evidence, Replimune's stock could quickly reverse its gains. The current rally is driven by procedural progress rather than new clinical data.
Investors are now watching closely as Replimune works to convert the FDA's urgency into a successful filing and a favorable review outcome. The company must navigate the review process and address any lingering concerns about the strength of its clinical evidence.
