FDA Approves Tudriqev: What the New Melanoma Immunotherapy Combination Actually Does

On August 6, 2026, the FDA granted accelerated approval to Tudriqev (vusolimogene oderparepvec-wtpg, formerly RP1), an engineered oncolytic herpes virus from Replimune, for use with nivolumab (Opdivo) in adults with unresectable Stage IIIB, IIIC, or IV cutaneous melanoma that has progressed on prior anti-PD-1 therapy. This piece explains how the therapy works, what the approval is (and isn't) based on, the unusually bumpy three-submission road it took to get here, and the real safety tradeoffs — including a genuine herpes-transmission risk — that patients and caregivers need to understand before considering it.

A Genuine Win for a Group With Few Options

For patients whose melanoma keeps growing after PD-1 checkpoint inhibitors — the backbone of modern melanoma treatment — options have historically been thin, and outcomes poor. The FDA's own approval materials note that more than half of patients progress within six months of anti-PD-1 therapy, with median overall survival after progression typically under a year. Tudriqev, given directly into tumors alongside continued nivolumab, is a genuinely new mechanism for this group, and it earned two of the FDA's more meaningful designations along the way — Breakthrough Therapy and Priority Review. It's a real, evidence-backed development worth taking seriously. It is not, however, a cure, a first-line treatment, or a guarantee of response — details below matter as much as the headline.

How Tudriqev Works

Tudriqev is built from herpes simplex virus type 1 (HSV-1), engineered to preferentially replicate inside tumor cells rather than healthy tissue. Two viral genes tied to neurovirulence (ICP34.5 and ICP47) have been deleted, and the virus has been modified to carry a fusogenic protein and human GM-CSF, an immune-signaling gene. The intent is twofold: the virus directly lyses (bursts) injected tumor cells, and the resulting release of tumor antigens and GM-CSF is meant to recruit and prime T cells — potentially amplifying nivolumab's effect on tumors the virus was never injected into. This "oncolytic-plus-checkpoint-inhibitor" pairing is the whole rationale for combining it with nivolumab rather than using it alone.

The Evidence Behind the Approval

The approval rests on IGNYTE (NCT03767348), an open-label, single-arm, multiregional trial that enrolled 140 patients with advanced, previously anti-PD-1-treated melanoma. Of those, 91 patients with at least one non-injected lesion made up the efficacy-evaluable population. The objective response rate was 24.2% (95% CI: 15.8–34.3), and the median duration of response was 14.1 months (95% CI: 10.7 to not yet reached). In plain terms: roughly one in four evaluable patients saw their tumors shrink substantially, and for those who did respond, the response tended to last over a year — encouraging, but nowhere near a majority response, and the single-arm design means there's no direct, randomized comparison to standard care within this trial.

Three Tries at the FDA: The Regulatory Backstory

This is not a case of the FDA simply nodding an application through. Replimune's Biologics License Application for RP1 was rejected twice before this approval. The FDA issued a first Complete Response Letter in July 2025, stating that it did not view IGNYTE's single-arm design as an "adequate and well-controlled" investigation on its own. A second Complete Response Letter followed in April 2026, with the agency reiterating concerns about relying on a single-arm trial without a randomized control and about how response was assessed. Replimune resubmitted a third time, and the FDA's Cellular, Tissue, and Gene Therapies Advisory Committee took up the question of whether IGNYTE's results were interpretable and clinically meaningful at a July 30, 2026 meeting, voting 10–3 in favor — with committee members reportedly still describing aspects of the data as "messy" even in voting yes. The August 6 approval followed shortly after. This history matters: it's a signal that regulators themselves had real, sustained reservations about the strength of the evidence, even as they ultimately judged the unmet need and response data sufficient to proceed.

Side Effects and the Herpes Warning

Because Tudriqev is a live, engineered herpes virus, its safety profile differs from typical immunotherapies. Adverse reactions reported in more than 10% of trial patients included fatigue, fever, infections, chills, musculoskeletal pain, nausea, diarrhea, injection-site reactions, headache, cough, flu-like illness, rash, vomiting, itching, joint pain, constipation, decreased appetite, dizziness, shortness of breath, bleeding, swelling, and abdominal pain; serious adverse reactions occurred in about 35% of patients, per FDA-sourced approval summaries. The label also carries a specific warning about accidental herpes transmission and reactivation: healthcare providers, caregivers, close contacts, pregnant people, and newborns are advised to avoid direct contact with injected tumors, dressings, or bodily fluids, and patients need monitoring for herpetic symptoms. Effective contraception is recommended during treatment and for 90 days afterward.

What "Accelerated Approval" Means Here

Tudriqev was approved under the FDA's accelerated approval pathway, based on response rate and duration of response — surrogate measures, not proof of longer survival. Continued marketing approval is contingent on a confirmatory trial, IGNYTE-3 (NCT06264180), verifying real clinical benefit. If that trial doesn't confirm benefit, approval could eventually be withdrawn — a real, if uncommon, outcome for accelerated approvals across oncology.

Who This Is — and Isn't — For

Tudriqev's approved use is narrow: adults with unresectable Stage IIIB/IIIC/IV cutaneous melanoma who have already progressed on anti-PD-1 therapy, given by direct intratumoral injection alongside continued nivolumab. It is not approved as a first-line therapy, not approved for melanoma that hasn't spread beyond what's surgically resectable, and it is not a substitute for standard checkpoint-inhibitor therapy for patients who haven't tried it yet or are still responding to it.

Bottom Line

Tudriqev is a legitimate, hard-won addition to the toolkit for advanced melanoma that has stopped responding to standard immunotherapy — and the fact that it took three FDA submissions and an advisory committee vote to get here is worth knowing, not hiding. If you or someone you're caring for is considering it, ask your oncologist directly about the 24% response rate in context (what happens to the other three-quarters of patients), what the accelerated-approval status and the ongoing IGNYTE-3 confirmatory trial mean for how confident to be in long-term benefit, and — because this is a live, engineered herpes virus — what specific precautions household members, caregivers, and anyone who is pregnant or immunocompromised need to take around injection sites and bodily fluids. This is a meaningful option for a specific, difficult situation, not a general breakthrough for melanoma at large.