FDA Clears “Cancer-Killing” Herpes Virus for Melanoma That Stopped Responding to Immunotherapy — What the Data Actually Show

What This Article Covers

On August 6, 2026, the FDA granted accelerated approval to Tudriqev (vusolimogene oderparepvec-wtpg), a genetically engineered oncolytic herpes virus, in combination with the checkpoint inhibitor nivolumab (Opdivo), for adults with advanced melanoma that has stopped responding to PD-1-blocking immunotherapy. It is only the second oncolytic virus therapy ever approved in the United States, following Imlygic in 2015, and it arrives for a patient population — those who have already failed frontline immunotherapy — with genuinely limited options. The approval is real and meaningful, but it is also conditional: it rests on a single-arm trial with a 24% response rate, and the FDA's own reviewers flagged unresolved questions about the study's design that a divided advisory committee narrowly voted past.

What the FDA Actually Approved

Tudriqev is manufactured by Replimune, a Massachusetts-based biotech, and is injected directly into accessible tumors rather than given systemically. It's built from a modified herpes simplex virus type 1 (HSV-1) with two viral genes deleted — ICP34.5 and ICP47 — which normally allow the virus to attack healthy nerve cells and hide from the immune system. In their place, the virus is engineered to carry human GM-CSF, an immune-signaling protein, plus a fusogenic protein derived from the gibbon ape leukemia virus that helps infected cancer cells fuse together and die. The idea, consistent with how oncolytic viruses work generally, is a two-step attack: the virus replicates inside tumor cells until they rupture, and that rupture spills out cancer proteins and inflammatory signals that can help the immune system recognize the tumor as a threat — potentially priming a broader anti-tumor immune response beyond the injected lesion itself.

The approved indication is specific and narrow: adults with unresectable, advanced cutaneous melanoma (stage IIIB, IIIC, or IV) whose disease progressed after at least eight weeks of a PD-1-blocking antibody regimen, used together with nivolumab. It is not approved as a first-line treatment, and it is not approved as a monotherapy.

The Trial Behind the Approval

The approval is based on IGNYTE (NCT03767348), an open-label, single-arm, multiregional Phase 1/2 trial — not the randomized, placebo-controlled design regulators normally prefer for confirming a drug's own contribution to an outcome. In the cohort of patients who had already failed anti-PD-1 therapy, 140 patients were enrolled, and 91 were evaluable for the efficacy analysis (patients who had at least one tumor lesion not directly injected with the virus, allowing assessment of effects beyond the injection site).

The results: an objective response rate of 24% (24.2%), meaning roughly one in four evaluable patients saw meaningful tumor shrinkage, with a median duration of response of 14.1 months among responders. That duration is genuinely encouraging for a population with few remaining options — but it's worth being precise about what a 24% response rate means: three in four patients evaluated did not have an objective response to this regimen.

Safety data showed most adverse events were mild to moderate (Grade 1-2) and transient, with no common Grade 4 or 5 events reported and serious adverse reactions occurring in 35% of patients. The most frequent side effects (each affecting more than 10% of patients) included fatigue, fever, chills, nausea, diarrhea, injection-site reactions, headache, cough, flu-like illness, rash, and musculoskeletal pain. Because Tudriqev is a live, modified herpes virus, its label carries a specific warning about the risk of herpes transmission and viral reactivation, a consideration for immunocompromised patients, caregivers, and household contacts.

A Bumpy Regulatory Path

This approval followed two prior FDA rejections (complete response letters), the most recent in April 2026, after which Replimune publicly criticized the agency's review process as inconsistent and slow-moving. The FDA's own reviewers raised a specific technical concern that carried through to the final decision: because IGNYTE was a single-arm trial combining Tudriqev with nivolumab, reviewers argued it was difficult to cleanly separate how much of the observed benefit came from the virus itself versus from nivolumab alone. The agency's Cellular, Tissue and Gene Therapies Advisory Committee took up the question in July 2026 and voted 10 to 3 that the data showed a sufficient efficacy signal to support approval — a favorable but not unanimous verdict that reflects real, unresolved scientific uncertainty rather than a clear-cut case.

Because this is an accelerated approval — a pathway reserved for serious conditions with unmet need, based on a response-rate-type surrogate endpoint rather than a “hard” outcome like overall survival — it is explicitly conditional. Full approval depends on the ongoing Phase 3 confirmatory trial, IGNYTE-3 (NCT06264180), which is comparing the Tudriqev-nivolumab combination against standard second-line options; results are expected in 2027. If that trial fails to confirm a real clinical benefit, the FDA can withdraw the approval.

What It Means for Patients

For the specific population this drug targets — people with advanced melanoma who have already progressed on PD-1 immunotherapy — treatment options are genuinely scarce, and a one-in-four chance of a durable response, with a median response lasting over a year, is a meaningful addition to the toolkit rather than a marginal one. FDA officials described the prognosis for this group as often severe and framed the approval as giving oncologists a meaningful new tool — an accurate characterization of unmet need, not an overstatement of the drug's proven benefit.

Patients and clinicians should treat this as a promising but unconfirmed option, administered under specialist oversight (the virus must be injected into tumors, and household/herpes-exposure precautions apply), not as an established standard of care. Cost will also be a real-world factor: reporting on the launch put the price in the range of $450,000 per course before rebates and discounts, and analysts' peak-sales estimates for the drug vary widely, an indirect signal of how much post-launch uncertainty remains.

Bottom Line

Tudriqev's approval is a legitimate, well-documented regulatory event — the second oncolytic virus therapy ever cleared by the FDA, arriving for melanoma patients who have run out of standard immunotherapy options and showing a durable response in roughly a quarter of patients tested. But it is accelerated, not full, approval; it rests on a single-arm trial that FDA's own scientists said made it hard to isolate the virus's specific contribution; and its ultimate value will not be settled until the Phase 3 IGNYTE-3 trial reports out in 2027. Patients considering it should understand it as a genuinely new option with real promise and real open questions, not a cure.