Replimune's RP1 Advances 131% in Three Months on FDA Clearance and Clinical Wins

Replimune Group’s stock has emerged as a standout performer, rallying approximately 131% over the past three months following a significant turning point in the company’s regulatory journey. The catalyst: the FDA’s acceptance in October of a resubmitted Biologics License Application (BLA) for RP1 in combination with Bristol Myers’ Opdivo—a move that has fundamentally shifted market sentiment around the company’s lead asset.

From Rejection to Resubmission: How Replimune Reversed Course

The path to this October win was far from straightforward. In July 2025, Replimune faced a setback when the FDA issued a Complete Response Letter (CRL) for the initial RP1/Opdivo BLA. The agency raised several technical concerns: heterogeneity in the IGNYTE study population, questions about whether the trial met the standard for “adequate and well-controlled” clinical investigations, and requests for clarification on how individual components contributed to outcomes. Notably, safety concerns were absent from the letter.

Rather than signaling a dead end, the CRL provided a roadmap. Replimune engaged in extensive dialogue with the FDA, ultimately addressing the agency’s feedback to the satisfaction of regulators. The resubmitted BLA was accepted under Priority Review, with the FDA setting an April 10, 2026 target action date—providing investors with concrete visibility into a potential approval decision within 16 months.

Clinical Data Supporting the 131% Rally

The confidence behind Replimune’s 131% three-month surge is rooted in compelling clinical performance. In October, the company reported positive results from the IGNYTE phase II trial presented at ESMO Congress, particularly in the acral melanoma cohort. The RP1/Opdivo combination demonstrated a 44% objective response rate with a median response duration of 11.9 months—outcomes that reinforced the combination’s therapeutic potential in a challenging melanoma subset.

Beyond melanoma, Replimune’s pipeline is expanding. The company has generated encouraging safety and efficacy data for RP1/Opdivo in non-melanoma skin cancers, with a separate program evaluating RP1 as monotherapy in immunocompromised transplant recipients. Additionally, RP2, Replimune’s second oncolytic immunotherapy candidate, is progressing through mid-to-late stage trials for metastatic uveal melanoma and hepatocellular carcinoma.

Market Context and Stock Performance

Despite the 131% three-month surge, Replimune shares remain down 19.6% on a year-to-date basis, underperforming the broader biotech industry’s 20.2% gain. This reflects the sector’s typical volatility around regulatory outcomes. The October rally represents an inflection point where previously uncertainty has transformed into concrete timelines and regulatory validation.

The BLA’s acceptance effectively de-risks the RP1/Opdivo program by confirming that Replimune’s remediation efforts satisfied FDA concerns. Investors now have clarity: assuming the April 2026 decision proceeds on schedule and yields an approval, RP1/Opdivo could enter the commercial phase within approximately one year, positioning Replimune to compete in the post-PD1 resistant melanoma treatment landscape alongside established players like Bristol Myers’ Opdivo portfolio.

What’s Priced In

The 131% rally reflects restoration of investor confidence and improved visibility into near-term catalysts. However, the April 2026 decision date remains the critical inflection point. An approval would validate Replimune’s approach to oncolytic immunotherapy and potentially unlock the company’s broader pipeline applications. A surprise rejection or conditional approval could reverse recent gains, making this a momentum-driven play tied to a specific regulatory milestone rather than a fundamentally re-rated company.