Full Breakdown
Food and Drug Administration’s (FDA) Advisory Panel Backs Replimune’s RP1 for Advanced Melanoma
8/1/2026, 5:26:16 AM
Core Event
On July 30 the FDA’s Cellular, Tissue, and Gene Therapies Advisory Committee (CTGTAC) voted 10-3 to deem the efficacy results from Replimune’s IGNYTE trial of RP1 (vusolimogene oderparevec) plus nivolumab “evaluable and clinically meaningful.” The recommendation applies to patients with advanced melanoma whose disease has progressed after anti-PD-1 therapy. The FDA will issue a final decision on the resubmitted Biologics License Application by August 2, 2026.
Background & Context
RP1 is an oncolytic herpes-simplex-virus platform engineered to express a fusogenic protein and GM-CSF, intended to kill injected tumors and stimulate systemic immunity. Replimune first sought accelerated approval in late 2024 and received breakthrough designation, but the agency rejected the application in April 2026, citing the single-arm IGNYTE study’s lack of a control group. After a June 2026 resubmission that incorporated FDA feedback, the advisory panel evaluated the same data set.
Data & Statistics
- Objective response rate (ORR): 33.6 % (47/140) when including directly injected lesions; FDA analysts calculated 15.7 % (22/140) using a stricter definition.
- Complete remission: ~15 % of patients achieved complete tumor disappearance.
- Duration of response: Company-reported median 24.8 months versus FDA-calculated 14.1 months.
- Overall survival: Median 32.9 months, with 47 % alive at three years.
- Safety: No major safety signals beyond those expected from nivolumab.
Official Statements & Responses
Acting deputy director Megha Kaushal said the agency will weigh the committee’s recommendations, the public hearing, and the “totality of the scientific discussion” before a decision. Replimune’s CEO Sushil Patel expressed gratitude for the panel’s support and pledged continued collaboration with the regulator.
Criticism & Opposition
Experts highlighted methodological concerns. Paul Chapman, chief medical research officer at Weill-Cornell, said he “doesn’t even understand the data” and questioned the reliability of the response rate. Sundeep Agrawal noted that the contribution of RP1 versus nivolumab had not been demonstrated, underscoring doubts about isolating RP1’s effect.
On-the-Ground Reports
Patient advocates and clinicians presented mixed perspectives. Diane Aronson, a patient representative, described the study’s RECIST criteria as “confounding.” Roughly 30 speakers shared personal experiences of tumor shrinkage and extended survival.
Conflicting Reports & Gaps
The primary discrepancy centers on the calculated ORR—33.6 % versus 15.7 %—and the median duration of response, reflecting divergent analytic approaches to a single-arm design. FDA reviewers labeled the survival analysis “uninterpretable” because the study lacked a concurrent control group, leaving uncertainty about whether observed benefits can be attributed to RP1 alone.
Verbatim Quotes
- “Overall there is some signal there, and we should follow that signal,” — Jorge Garcia, chairman, UH Seidman Cancer Center
- “I just don't even understand the data. I don't know what the response rate is. I don't know what to compare it to. We know that the chance of this being wrong, I think, is high,” — Paul Chapman, Weill-Cornell
What’s Next
The FDA will render a decision on RP1’s biologics license application by August 2, 2026. The ruling will determine whether the panel’s endorsement leads to accelerated approval for a therapy targeting a high-unmet-need population.
