RP1 Hits 47.8% 3-Year Survival in PD-1-Failed Melanoma at ASCO

Replimune presented three-year overall survival data from the IGNYTE clinical trial of RP1 (vusolimogene oderparepvec) plus nivolumab in patients with anti-PD-1-failed advanced melanoma during an oral session at the 2026 American Society of Clinical Oncology Annual Meeting on May 30. Median overall survival reached 32.9 months and 47.8% of all treated patients were alive at three years, rising to 83.5% among those who responded to the combination. One day earlier, on May 29, the company announced that the U.S. Food and Drug Administration had aligned on a path for resubmission of the RP1 Biologics License Application and would prioritize the agency's review. **Key Takeaways** - Three-year landmark data from the IGNYTE trial showed 47.8% overall survival across all treated patients with anti-PD-1-failed advanced melanoma, rising to 83.5% among responders, presented at ASCO on May 30, 2026. - Median overall survival reached 32.9 months, with an objective response rate of 33.6% and a median duration of response of 24.8 months in a population that fails standard checkpoint inhibitor therapy approximately half the time. - Replimune announced on May 29, 2026 that the FDA has aligned on a path to resubmit the RP1 Biologics License Application and will treat the resubmission as an urgent matter for prioritized review. - Approximately 112,000 new U.S. melanoma cases are estimated in 2026, with 8,500 annual deaths, reinforcing the importance of daily broad-spectrum SPF and routine dermatologist skin checks as the foundation of melanoma risk reduction. The presentation, delivered by Michael Wong, MD, PhD, at session E451 under Abstract 9518, marks the longest follow-up reported to date for RP1 plus nivolumab in a population with confirmed progression on prior anti-PD-1 therapy. According to Replimune's [May 30 press release](https://www.globenewswire.com/news-release/2026/05/30/3303875/0/en/Replimune-Presents-3-Year-Landmark-Overall-Survival-Analysis-from-IGNYTE-Clinical-Trial-During-Oral-Presentation-at-the-2026-American-Society-of-Clinical-Oncology-Annual-Meeting.html), 44.8% of responders maintained their response at three years, and meaningful survival benefit was observed across key patient subgroups, including those with varying disease stage, PD-L1 expression status, prior anti-CTLA-4 exposure, and primary or secondary anti-PD-1 resistance. ## The Treatment Setting Where Standard Care Routinely Fails Advanced melanoma is the most lethal form of skin cancer. Approximately 112,000 new U.S. cases are projected in 2026 and roughly 8,500 patients die from the disease each year, according to figures Replimune cited in its [May 29 BLA-resubmission release](https://www.globenewswire.com/news-release/2026/05/29/3303541/0/en/Replimune-Announces-Planned-RP1-BLA-Resubmission-Following-Productive-Discussion-with-FDA.html). Standard first-line therapy uses immune checkpoint inhibitors, most often PD-1 blocking antibodies such as nivolumab or pembrolizumab, sometimes combined with the CTLA-4 inhibitor ipilimumab. Approximately half of patients either fail to respond initially or progress after an initial response. For that anti-PD-1-failed population, the historical record has offered limited durable benefit. The IGNYTE follow-up therefore lands in a setting where the bar for clinical meaningfulness is set by years of unmet need rather than by competition. ## How Does an Engineered Herpes Virus Treat Melanoma? RP1 is an oncolytic immunotherapy built on a modified herpes simplex virus type 1 backbone. The virus is engineered with two functional additions: a fusogenic glycoprotein from gibbon ape leukemia virus (GALV-GP R-) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Injected directly into tumor lesions, the virus selectively replicates inside tumor cells, lyses them, and releases tumor-derived antigens. The fusogen amplifies local tumor cell killing, and GM-CSF recruits and matures dendritic cells that then prime a systemic anti-tumor T-cell response. Combined with nivolumab, which removes the PD-1 brake on those primed T cells, the regimen is designed to convert local viral activity into broader systemic immunity that can attack distant, uninjected lesions. The safety profile in the IGNYTE follow-up was consistent with prior reporting. Constitutional side effects were predominantly Grade 1 to 2, no Grade 5 events were recorded, and no new safety signals emerged over the extended follow-up period. ## What Does the FDA Pathway Mean for Approval Timing? The agency issued a Complete Response Letter for RP1 on April 10, 2026, which sent the program back for additional dialogue. According to the May 29 announcement, the FDA and Replimune have since aligned on a resubmission path, the company plans to refile within days, and the agency has indicated it will treat the resubmission as an urgent matter and prioritize the review. Sushil Patel, Replimune's Chief Executive Officer, said in the release that the company looked forward to working with the FDA to bring the therapy to the advanced melanoma community as quickly as possible. A formal decision date will follow once the resubmission is accepted. The agency's commitment to prioritized review does not equate to approval, but it does compress the timeline that looked uncertain seven weeks ago. Combined with the freshly presented three-year survival data, the regulatory posture sets up a clearer line of sight to a near-term decision. ## What This Means for the Prevention-First Reader Treatment advances in advanced melanoma do not change the practical calculus for skincare-conscious readers, but they do underline why prevention matters so much. The IGNYTE results are meaningful precisely because the disease they address is so difficult to treat once it has progressed. Daily broad-spectrum sunscreen, sun-protective clothing, and annual full-body dermatologist skin checks remain the most effective interventions for melanoma risk reduction. SkinCareful has covered the [emerging EWG 2026 sunscreen guide](https://skincareful.care/news/ewg-2026-sunscreen-guide/) and the [global burden of skin cancer projected through 2050](https://skincareful.care/news/jama-derm-global-skin-cancer-burden-2050/) for readers building a long-horizon photoprotection strategy. For patients and families navigating advanced disease, the IGNYTE data and the FDA dialogue together represent the most concrete signal in months that an additional durable treatment option may be approaching availability. Those decisions belong with treating oncologists and dermatology-oncology specialists; the value of the broader news for the skincare reader is the reminder that the prevention work done daily, year after year, is what keeps most people out of this treatment setting in the first place.