A 56% confirmed overall response rate from a single infusion in patients who had already cycled through a median of two prior systemic lines — including checkpoint inhibitor combinations — is not the number most cell therapy programs produce in heavily pretreated metastatic melanoma. That figure, drawn from 33 patients treated at the recommended Phase 2 dose in Immatics’ Phase 1b expansion cohort, carries particular weight in uveal melanoma, where confirmed ORR hit 67% and median overall survival remains unreached at 14.3 months of follow-up. Uveal melanoma has no approved systemic standard of care beyond tebentafusp, and tebentafusp’s survival benefit came without meaningful tumor shrinkage. Anzu-cel is producing both.
The response dynamics presented at ASCO are as important as the top-line numbers. Median time to best overall response was 1.4 months — rapid for an adoptive cell therapy — and median duration of response reached 14.6 months across all melanoma subtypes, stretching to 38.2+ months at the tail of the curve. Among the 42% of patients who achieved deep responses of 50% or greater tumor reduction, median PFS extended to 15.9 months. The exploratory lesion-level analysis adds a complication worth scrutinizing: several patients classified as progressive disease by RECIST 1.1 had shrinking target lesions, with progression driven by new lesions or selective outgrowths rather than systemic failure. This dissociation between RECIST classification and biological activity is a known challenge for T-cell therapies but also raises a design question — whether the SUPRAME Phase 3 trial’s primary endpoint, structured around conventional RECIST progression, fully captures anzu-cel’s treatment effect in the population it will enroll.
The tolerability data reinforce what the earlier readouts suggested: cytokine release syndrome was predominantly Grade 1 or 2, no patients experienced long-term CRS, and ICANS occurred infrequently. That profile is clinically meaningful because it distinguishes anzu-cel from CAR-T constructs that require intensive monitoring infrastructure, broadening the realistic treatment setting for a potential commercial launch. The one-time infusion model also matters for a disease where patients deteriorate quickly across lines of therapy.
With BLA submission targeted for the first half of 2027, the single number to track is the SUPRAME trial’s PFS event rate in the cutaneous melanoma arm — specifically whether the 37% PFS rate at 12 months observed in Phase 1b translates into a statistically convincing separation from investigator’s choice in a randomized setting. That readout determines whether anzu-cel reaches the market as a transformative option or becomes a footnote about promising early signals that didn’t replicate.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
