FDA Approves Engineered Herpes Virus Immunotherapy for Advanced Melanoma After Twice Rejecting It

What This Article Covers

On August 6, 2026, the FDA granted accelerated approval to Tudriqev (vusolimogene oderparepvec-wtpg, formerly known as RP1), a genetically engineered oncolytic herpes simplex virus therapy from Replimune Group, for use in combination with the checkpoint inhibitor nivolumab (Opdivo) in adults with unresectable advanced cutaneous melanoma that has progressed after anti-PD-1-based treatment. It is a genuinely novel mechanism reaching patients who have run out of standard options — but it arrives after two prior FDA rejections, on the strength of a single-arm trial with a modest response rate, and its long-term approval now hinges on a confirmatory Phase 3 study still underway.

What Tudriqev Actually Is

Tudriqev is not a vaccine or a standard drug — it is a live, modified herpes simplex virus type 1 engineered to do two things at once. First, it selectively infects and replicates inside tumor cells, causing them to rupture (a process called oncolysis) while sparing normal tissue. Second, it is engineered to express GM-CSF, an immune-signaling protein, turning the dying tumor into a site that recruits and activates immune cells against the cancer — including, in principle, at tumor sites the drug was never injected into. Physicians administer it by direct injection into an accessible melanoma lesion, alongside intravenous nivolumab. This “in situ vaccine” approach has been a research goal in oncology for over a decade, and Tudriqev becomes only the second oncolytic virus therapy ever approved in the United States (after talimogene laherparepvec, T-VEC, in 2015), and the first approved in combination with a checkpoint inhibitor for PD-1-refractory disease.

The Data Behind the Approval

The approval rests on the IGNYTE trial (NCT03767348), an open-label, single-arm study that enrolled 140 patients with Stage IIIB, IIIC, or IV unresectable cutaneous melanoma who had progressed on at least eight weeks of prior anti-PD-1 therapy. Of the 91 patients evaluable for efficacy, the objective response rate was 24.2% (95% CI: 15.8–34.3%), and among those who responded, the median duration of response was 14.1 months (95% CI: 10.7 months to not yet reached) — meaning that for the roughly one in four patients who did respond, benefit tended to last more than a year. The safety profile, per the FDA label, includes fatigue, fever, infections, chills, musculoskeletal pain, nausea, diarrhea, and injection-site reactions in more than 10% of patients, along with labeled warnings for accidental viral exposure to caregivers/contacts, herpes reactivation, injection-related complications, and immune-mediated adverse events tied to the nivolumab component.

What It Means for Patients

For patients with advanced melanoma who have exhausted anti-PD-1 therapy — a group with historically poor options and grim prognosis — Tudriqev offers a genuinely new mechanism to try, one that doesn't rely on the same immune checkpoint pathway that already failed them. Because it can be given alongside continued nivolumab, it also offers a way to potentially “reawaken” a checkpoint inhibitor that had stopped working, rather than switching to an unrelated drug class entirely. The durability seen in responders (median beyond a year) is clinically meaningful in a population where second-line options often produce only brief disease control. That said, this is a narrow, specific population: adults with cutaneous (skin) melanoma, unresectable, that has already progressed on a PD-1 blocker — it is not approved for first-line use, for other melanoma subtypes (uveal or mucosal), or for other cancer types.

Important Caveats and Limitations

This approval carries more asterisks than a typical FDA sign-off. First, it is an accelerated approval, not full approval — it is contingent on results from a randomized confirmatory Phase 3 trial (IGNYTE-3, comparing the RP1-nivolumab combination against physician's choice of therapy), with results expected in 2027; if that trial fails to verify clinical benefit, the FDA can withdraw the approval. Second, the pivotal IGNYTE trial that supported approval was single-arm and open-label, with no randomized comparator — a weaker design than a controlled trial. Third, the path here was unusually contested: Replimune received two prior Complete Response Letters, most recently in April 2026, with FDA review staff explicitly questioning the trial's design and how responses were measured; the drug ultimately won approval only after an FDA advisory committee sided with the company over its own agency's reviewers. Fourth, the response rate itself is modest: roughly three in four treated patients did not achieve an objective response. Fifth, because the drug requires direct intratumoral injection, its use is inherently limited to patients with an accessible, injectable lesion. Finally, Replimune has set a list price around $450,000 per course before rebates and discounts, and insurance coverage decisions will need to catch up to the new indication.

Bottom Line

Tudriqev's approval is a real and interesting advance — it validates the “engineered virus plus checkpoint inhibitor” strategy in a genuinely hard-to-treat population and gives some PD-1-refractory melanoma patients a durable response they wouldn't otherwise have had. But this is accelerated approval built on a single-arm trial with a 24% response rate, following two rejections and an unusually contentious regulatory process, with confirmatory Phase 3 data still roughly a year away. Patients should discuss candidacy and realistic expected benefit with their oncologist, and should understand this is not a cure for most who receive it — it is a meaningful option for a minority of patients in a population that badly needed more of them.