Key Highlights

  • Replimune to resubmit BLA for RP1 in combination with Opdivo within days.
  • FDA pledges to treat resubmission as an urgent matter and prioritize review.
  • Replimune shares jumped 70% to $7.865, gaining $3.185 per share at market open on May 29, 2026.
  • RP1 was twice rejected under former FDA Commissioner Marty Makary, who resigned earlier this month.
  • Around 8,500 Americans die from advanced melanoma annually, with nearly half failing standard checkpoint therapy.

A Disputed Drug Finds a New Window

After two consecutive regulatory rejections, Replimune Group (Nasdaq: REPL) has secured an agreement with the U.S. Food and Drug Administration to resubmit its Marketing application for RP1, an oncolytic immunotherapy targeting patients with advanced melanoma who have stopped responding to standard checkpoint inhibitor treatment.

The company announced Friday it will resubmit the Biologics License Application for RP1, also known as vusolimogene oderparepvec, within days. The FDA has agreed to treat the application as an urgent matter upon receipt and will prioritize its review, citing significant unmet need in the advanced melanoma patient population.

Two Rejections, One Contentious Dispute

The drug's regulatory history has been turbulent. The FDA declined to approve RP1 for a second time in April 2026, issuing a complete response letter citing the company's reliance on a single-arm study without a control group. The agency instructed Replimune to provide data from a well-controlled trial demonstrating adequate evidence of effectiveness.

Replimune pushed back, arguing the FDA had wrongfully blocked a treatment that some oncologists regard as a meaningful option for a patient group with severely limited alternatives. The dispute became a wider flashpoint for industry frustration over perceived inconsistency in FDA guidance under former Commissioner Marty Makary's tenure. Makary stepped down earlier this month.

RP1: Mechanism and Clinical Basis

RP1 is Replimune's lead asset, built on a proprietary herpes simplex virus backbone engineered to carry a fusogenic protein and GM-CSF. The construct is designed to trigger direct tumor cell destruction, stimulate immunogenic cell death, and activate a broader systemic anti-tumor immune response. The BLA is supported by data from the IGNYTE clinical trial, evaluating RP1 in combination with Bristol Myers Squibb's (NYSE: BMY) Opdivo in patients with confirmed disease progression on a prior anti-PD-1 regimen.

Unmet Need: The Patient Case

Melanoma is the fifth most common cancer in the United States. Approximately 112,000 new cases are estimated in 2026, with around 8,500 deaths projected annually. Once the disease advances beyond the primary tumor site, standard checkpoint blockade remains the central treatment option. Roughly half of all patients treated with these therapies do not respond or develop progressive disease, leaving a substantial population without effective alternatives.

Market Reaction

Replimune shares jumped 70% to $7.865, gaining $3.185 per share at market open on May 29, 2026. The move reflects both the company's concentrated pipeline risk and the scale of the commercial opportunity should RP1 secure approval. As of Thursday's close, the company carried a Market Capitalisation of approximately $386 million, making the drug's regulatory fate the central determinant of its valuation.

Conclusion

Replimune's resubmission represents a reset in its regulatory relationship with the FDA rather than a guaranteed path to approval. The agency's willingness to engage constructively following a change in Leadership narrows the immediate uncertainty, but the underlying evidentiary question around trial design remains unresolved. For investors, the 68% single-day move prices in renewed optimism. The clinical and Regulatory Risk, however, remains material until a formal decision is issued.