Immunocore Holdings plc has presented four posters with KIMMTRAK (tebentafusp-tebn) data in HLA-A*02:01 patients with metastatic uveal melanoma (mUM), at the 2023 American Association for Cancer Research Annual Meeting 2023. Circulating tumor DNA (ctDNA) reduction by week 9 was observed in 88% of metastatic uveal melanoma (mUM) patients treated as first-line (Phase 3 clinical trial) and 71% in previously treated patients (Phase 2 clinical trial); in both trials, this reduction was associated with longer overall survival (OS). ctDNA clearance was also higher in first-line patients (37%) compared to second-line patients (13%).

ctDNA clearance in the Company's Phase 3 clinical trial was associated with 84% 1-year OS. In both trials, the association between ctDNA reduction and longer OS was also observed in patients with best RECIST response of progressive disease (PD), indicating that RECIST responses underestimate tebentafusp's clinical benefits, and that ctDNA may be a better predictor of long OS than radiographic response. The final analysis from the Phase 2 trial in previously treated mUM, after 46 months of follow-up, showed a median OS of 16.8 months – consistent with previous data updates.

The landmark OS rates from the trial were approximately double historical rates in this patient population, as reported in two meta-analyses1,2. Later in 2023, the Company intends to provide an OS update from the Phase 3 trial. At the time of primary analysis in 2020, the median OS was 21.7 months for patients treated with KIMMTRAK, versus 16.0 months for those treated with investigator's choice. The third poster provides a pooled analysis from 3 clinical trials in 12 mUM patients with orbital disease.

Tebentafusp demonstrated preliminary signals of activity in intra-ocular lesions, supporting KIMMTRAK's use in patients with unresectable uveal melanoma. The fourth poster shares in vitro data potentially explaining how tebentafusp may lead to OS benefit even in tumors with heterogenous gp100 expression.