Advanced skin cancer that grows after immunotherapy has left doctors with few effective options. On August 6, 2026, the FDA granted accelerated approval for Tudriqev (Vusolimogene Oderparepvec-wtpg) by Replimune, a genetically modified herpesvirus that destroys melanoma cells from within and simultaneously activates the immune system against the tumor. The approval came via an unusual path: two rejections in less than one year, an Advisory Committee vote of 10 to 3, and a third submission in fewer than 14 months.
PD-1 resistance: When the best immunotherapy stops working
Nivolumab (Opdivo) and Pembrolizumab (Keytruda) rank among the most effective cancer medications of the past decade. As PD-1 inhibitors, they release an immune blockade that tumor cells use to escape detection. In advanced melanoma, they have substantially improved prognoses. Yet some patients do not respond or the tumor develops resistance.
For these patients, options were previously limited: chemotherapy with moderate effectiveness in metastatic melanoma, other checkpoint inhibitors, or targeted therapies against specific mutations that are not applicable to all patients. Tudriqev closes one of these gaps: it is approved for adults with unresectable advanced cutaneous melanoma whose disease has progressed on a PD-1-based therapy regimen.
How a herpesvirus becomes a cancer drug
Tudriqev is based on herpes simplex virus type 1 (HSV-1), genetically modified so it selectively infects tumor cells and replicates within them. The mechanism is two-stage: the virus destroys cancer cells through replication and thereby releases tumor antigens. Simultaneously, this release activates the immune system against the tumor so it can recognize even indirectly non-injected metastases. Tudriqev is used in combination with nivolumab.
According to the FDA, the IGNYTE study underlying the approval showed an objective response rate of 24 percent in 91 evaluable patients. The median duration of these responses was 14.1 months. For patients who have no effective options left after all previous therapies, a response rate of one in four with multi-month activity duration is clinically meaningful.
Three submissions, two rejections: An unusual approval history
Replimune initially submitted Tudriqev and received the FDA's first rejection in July 2025. The agency objected to the single-arm structure of the IGNYTE study: without a control group, it could not reliably determine how much of the measured effect was attributable to the virus and how much to nivolumab alone. After resubmission in October 2025, a second rejection followed on April 10, 2026 with similar reasoning.
Replimune then negotiated a new pathway with the FDA, submitted a third version of the application, and presented itself to an Advisory Committee meeting on July 30, 2026. The external expert panel voted 10 to 3 in favor of the data being clinically meaningful. One week later came accelerated approval.
Comparison: T-VEC and the history of oncolytic viruses in melanoma
Tudriqev is not the first oncolytic herpesvirus for melanoma. T-VEC (Talimogene Laherparepvec, marketed as Imlygic) by Amgen received FDA approval in October 2015 as the world's first oncolytic virus therapy, also based on HSV-1. T-VEC is injected directly into accessible tumor lesions and was approved for a different patient group: melanoma patients with locally advanced, not completely resectable tumors, not specifically after PD-1 therapy failure. In the phase 3 OPTiM study, T-VEC showed a sustained response rate of 16.3 percent for all injected and non-injected lesions.
Tudriqev serves a different niche: patients after failure of the best available immunotherapy. The combination with nivolumab is intended to reactivate the immune system that PD-1 therapy previously could not durably stimulate. A procedure that directly destroys cancer cells and simultaneously redirects the immune system follows different logic than T-VEC alone and represents a conceptual advancement of oncolytic virus therapy.
Three conditions for long-term success
The accelerated approval is based on a surrogate endpoint, objective response rate, not overall survival. Replimune must submit a confirmatory study. Whether the effect holds in a randomized study with control group, which is precisely what both FDA rejections said was missing, is the first open question.
The second condition concerns patient selection. One of four patients responds, three of four do not. Biomarkers that predict before treatment who benefits remain unknown. Without such markers, even non-responding patients receive the therapy with its costs and side effects.
The third question is access. Replimune made no statements on therapy costs. Oncolytic virus therapies require specialized manufacturing. Whether Tudriqev becomes accessible to cancer centers outside the US and when European patients gain access depends on pricing and EMA approval. The accelerated US approval is a first step, but no guarantee of broad availability.