FDA Approves Tudriqev, an Engineered Cancer-Killing Virus for Advanced Melanoma

The FDA has granted accelerated approval to Tudriqev (vusolimogene oderparepvec) — an engineered virus that attacks tumours — for advanced melanoma that has stopped responding to standard immunotherapy.

Announced August 6, 2026, Tudriqev (developed by Replimune, formerly known as RP1) is approved in combination with nivolumab for adults with unresectable advanced cutaneous melanoma whose disease progressed on a PD-1-blocking drug.

How an oncolytic virus works

It is a genetically modified oncolytic virus: injected directly into tumours, it infects and destroys cancer cells while also alerting the immune system to attack the cancer.

The second mechanism is the more important one. Direct killing is limited to tumours the needle reaches, and a patient with widespread disease has lesions that cannot all be injected.

The immune effect is not so constrained. Viral infection makes a tumour look like an infection rather than like self — releasing viral proteins the immune system recognises as foreign, alongside tumour antigens released as cells rupture. Immune cells recruited to that inflammatory site encounter both together, and can then recognise the same tumour antigens elsewhere in the body.

Engineering typically removes genes the virus needs to replicate in healthy cells while leaving it able to replicate in cancer cells, whose defective antiviral responses make them permissive.

Why the nivolumab combination

Pairing the virus with a checkpoint inhibitor addresses complementary failures, which is why the combination is more logical than either alone in this population.

Checkpoint inhibitors release brakes on T cells that are already recognising the tumour. They fail when too few T cells recognise it — a “cold” tumour, immunologically quiet, with nothing for the drug to unleash.

The virus generates that recognition by creating inflammation and exposing antigens. The checkpoint inhibitor then permits the resulting T cells to act.

These are patients who already progressed on anti-PD-1, so the checkpoint inhibitor alone had failed. The claim is that the virus supplies what was missing and restores its effect.

The evidence

Approval rested on a trial of 140 patients with Stage IIIB, IIIC or IV melanoma who had progressed on prior anti-PD-1 therapy. Among the 91 patients evaluated for response, 24% had an objective response, with a median duration of 14.1 months.

Duration is what makes the response rate meaningful. A 24% response is modest in isolation; responses lasting a median of over a year in patients who had exhausted standard immunotherapy are a different proposition, because this population otherwise faces rapid progression.

Common side effects included fatigue, fever, infections, chills, muscle and joint pain, nausea and injection-site reactions — a profile consistent with a deliberately induced immune and viral response.

The two rejections

The approval is notable for its history: it came after the FDA had twice rejected the therapy.

Rejections in this class usually turn on trial design rather than on the drug failing. Single-arm trials in heavily pretreated populations raise the question of what the response rate should be compared against, and regulators have pressed for randomised evidence where they judged it obtainable.

Two rejections followed by approval suggests the eventual agreement concerned how the existing evidence should be interpreted for a population with no remaining options — the same data, weighed against a different alternative.

What accelerated approval means here

As an accelerated approval, continued approval may depend on confirmatory trials verifying the benefit.

The pathway permits approval on a measure reasonably likely to predict benefit — here tumour response — rather than on demonstrated survival gain. Response rate is a plausible surrogate and is not the same thing: tumours can shrink without patients living longer.

The class this joins

Oncolytic virus therapy has a longer history than its small number of approvals suggests, and that history explains the caution surrounding it.

The idea dates to observations that some cancer patients experienced tumour regression after viral infections. Deliberate attempts to exploit it began decades ago and produced little, because unmodified viruses either failed to replicate adequately in tumours or caused genuine infection.

Genetic engineering changed the calculation by allowing viruses to be disabled in normal cells while remaining active in cancer cells, and by allowing them to carry immune-stimulating genes. The first such therapy for melanoma was approved roughly a decade ago, delivering an immune-signalling protein alongside its direct killing.

Uptake has been limited since. Intratumoral injection restricts use to accessible lesions and requires procedural capacity that not every oncology practice has, handling a live modified virus carries logistical requirements, and results have been respectable rather than transformative.

An approval in the post-checkpoint-failure setting is therefore a meaningful expansion of where the class fits — addressing patients for whom the alternative is not a better therapy but no established therapy at all.

Withdrawal is a real possibility if confirmation fails, and it has happened to other oncology drugs. Still, it adds a rare new option for patients who have run out of standard choices. Regulatory news, not medical advice.