Replimune’s oncolytic HSV therapy RP1 (vusolimogene oderparepvec) plus Opdivo (nivolumab) was again denied FDA accelerated approval for advanced melanoma via a second complete response letter, despite IGNYTE Phase I/II data in 140 patients showing a 34% response rate and median duration of response of 24.8 months.

Why It Matters To Oncology

• The FDA’s core objection is methodological: IGNYTE was not designed to isolate RP1’s contribution when combined with nivolumab, and patient heterogeneity limited interpretability—signaling a high bar for single-arm combo BLAs under accelerated approval.

• For oncolytic virus drug discovery, the decision underscores that mechanistic plausibility and durable responses may not substitute for trial designs that cleanly attribute effect in combination regimens.

• Operationally, the setback threatens program continuity: CEO Sushil Patel said “without timely accelerated approval, the development of RP1 will not be viable,” raising the risk that potentially active platforms stall before confirmatory readouts.

The Financials

• Replimune shares fell ~20% on the news and dropped an additional ~60% after hours.

• The company signaled imminent cost cuts, including scaling back U.S. manufacturing and job reductions.

• The CRL adds to a 2025 pattern of notable FDA pushbacks (alongside other high-profile rejections cited by the company).

What They're Saying

• Replimune: the medicine didn’t fail—“the system did,” Patel said, criticizing a “fragmented and slow-moving” review and “inconsistent communication.”

• Replimune also alleges reviewer turnover between the initial and resubmitted BLA and cites a prior reviewer’s public comment that the clinical team felt evidence supported contribution of effect, but leadership disagreed.

• FDA: concerns with IGNYTE’s design were “clearly communicated” throughout development; added analyses and early Phase III (IGNYTE-3) data were “insufficient to support an efficacy claim,” and adequate, well-controlled trial(s) are needed.

What's Next

• Regulatory path likely shifts from accelerated approval to waiting for randomized/controlled evidence—most plausibly the ongoing confirmatory Phase III IGNYTE-3 trial.

• Key scientific/regulatory question: whether IGNYTE-3 (and any additional controlled datasets) can resolve attribution of benefit beyond anti–PD-1 alone in advanced melanoma.

• Near-term watch items: Replimune’s cash-preservation actions, manufacturing footprint changes, and whether the company can sustain RP1 development to a definitive trial endpoint.