On April 19, 2026 Immunocore Holdings plc (Nasdaq: IMCR) ("Immunocore" or the "Company"), a commercial-stage biotechnology company pioneering and delivering transformative immunomodulating medicines to radically improve outcomes for patients with cancer, infectious diseases and autoimmune diseases, reported that KIMMTRAK (tebentafusp-tebn) five-year overall survival (OS) was presented in an oral session at the American Association for Cancer Research (AACR) (Free AACR Whitepaper) 2026 meeting.

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This is the longest, prospective Phase 3 randomized trial in patients with unresectable or metastatic uveal melanoma (mUM) – a disease with a very poor prognosis and a historical survival rate of <5% at 5 years1. KIMMTRAK doubled the likelihood of being alive at five years, with an OS for KIMMTRAK of 16% versus 8% in the control arm (hazard ratio [HR] of 0.67 [95% CI: 0.54-0.85]). These results also represent the longest follow-up reported for any T cell engager in a solid tumor.

In the trial, 378 patients were randomized to tebentafusp (252) or investigator’s choice (126; 82% pembrolizumab). The median OS was 21.6 months on KIMMTRAK, versus 16.9 months on investigator’s choice (IC). The Kaplan–Meier survival curves separated early and remained separated over time, confirming the durability of the benefit with extended follow-up.

"These important results allow us, for the first time, to speak with real confidence to patients about the possibility of long-term survival," said Professor Paul Nathan, Consultant Medical Oncologist, Mount Vernon Cancer Centre, UK. "Before tebentafusp, such conversations simply weren’t possible for metastatic uveal melanoma patients."

"These long-term overall survival results further solidify KIMMTRAK as the first-line standard of care for HLA-A*02:01 positive patients with metastatic uveal melanoma," said Mohammed Dar, Immunocore Chief Medical Officer. "The survival benefit was evident even in patients with known poor prognostic factors, including those with large tumors and extrahepatic disease."

The data confirmed that the OS benefit was primarily driven by tebentafusp rather than subsequent therapies. Among patients treated with KIMMTRAK who were alive at five years, nearly half (44%) received only KIMMTRAK, while among patients in the control arm alive at the same time point, 86% subsequently received tebentafusp.

Importantly, the OS benefit with KIMMTRAK was observed regardless of known poor prognostic factors at baseline (high tumor burden [≥10cm]; elevated lactate dehydrogenase [LDH]) or tumor location (hepatic only; hepatic and extra-hepatic). OS benefit was also observed in patients with a best response of progressive disease, including those with >20% tumor growth as best change on treatment.

More patients continued treatment beyond progression in the KIMMTRAK arm than in the control arm (57% vs 25%) – with the trial allowing this option in both arms. Patients on KIMMTRAK achieved nearly a 7-fold higher rate of tumor reduction with treatment beyond initial progression compared to IC patients (27% vs 4%). In fact, patients who continued tebentafusp treatment beyond tumor progression experienced longer post-progression survival compared to those who stopped treatment, even after accounting for variations in patient characteristics.

In tebentafusp-treated patients, longer OS was associated with undetectable ctDNA at baseline or ctDNA reductions ≥50% by week 9. Among 21 ctDNA-evaluable patients who survived ≥ 5 years, 71% had undetectable baseline ctDNA and 29% had ctDNA clearance by week 9. Deep reductions in ctDNA were seen across all RECIST categories. Early ctDNA molecular response continues to be a more sensitive marker of tebentafusp activity than radiographic measurements.

The data were presented today in an oral session during the AACR (Free AACR Whitepaper) 2026 meeting:

Title: Five-year survival with tebentafusp in previously untreated metastatic uveal melanoma in a Phase 3 trial (CT029)
Presenting author: Paul Nathan
Session: Advanced Cellular and Immune-Based Therapeutics

(Press release, Immunocore, APR 19, 2026, View Source [SID1234664542])