On May 31, 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 updated results from its Phase 1/2 trial evaluating brenetafusp in patients with heavily pretreated advanced melanoma. The data is presented in a poster at the 2026 American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) Annual Meeting.

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"I am pleased to present these updated brenetafusp data at ASCO (Free ASCO Whitepaper). Patients with advanced melanoma who progress on anti-PD-1 therapy have limited options, and seeing meaningful disease control in heavily pretreated patients is genuinely promising. These results support continued evaluation of brenetafusp in advanced melanoma," said Professor Georgina Long, Medical Director, Melanoma Institute Australia, The University of Sydney.

"These data with brenetafusp in heavily pretreated advanced melanoma show consistent responses and survival even in those with poor prognosis, including patients with primary PD-1 resistance," said Mohammed Dar, Chief Medical Officer of Immunocore. "These data also reinforce our confidence in the potential of brenetafusp at the dose of 160 mcg in combination with nivolumab in first-line advanced melanoma, in the ongoing Phase 3 PRISM-MEL-301 trial."

Phase 1/2 efficacy data

In the 66 patients treated with brenetafusp monotherapy (target doses 20-320 mcg), the median overall survival (OS) was 14.3 months (95% CI: 11.3-20.4; median follow up of 22.4 months) with a landmark OS rate of 87% at 6 months and 57% at 12 months. The disease control rate (DCR = partial responses and stable diseases) was 52%, while the overall response rate (ORR) was 12%.

Multiple measures of clinical benefit (6-month OS, DCR, ORR, tumor reduction) were numerically higher for patients treated with the 160 mcg dose – despite worse baseline prognostic factors compared to those treated with 40 mcg. These data support selection of 160 mcg for the ongoing Phase 3 trial evaluating brenetafusp + nivolumab vs. standard nivolumab regimens (NCT06112314) in first-line advanced melanoma. The safety profile was similar at both doses.

Median OS was 14.7 months for patients with primary PD-1 resistance, defined as progression within 6 months of starting the first regimen containing anti-PD1. Despite these patients having primary PD-1 resistance, the median OS was similar to all monotherapy patients (14.3 months).

In exploratory analyses, circulating tumor DNA (ctDNA) response in patients with PD-1 primary resistance was numerically higher (53%; 8/15) compared to the overall group (38%; 19/50). Treatment outcome was not impacted by PD-L1 status and was shown, in this exploratory analysis, to be associated with tumor expression of beta 2 microglobulin – a protein involved in antigen presentation – and baseline peripheral blood T cell fitness, which has been shown to be better in earlier lines of therapy.

In the 10 patients treated with brenetafusp in combination with pembrolizumab, the data showed numerically higher ORR and DCR compared to monotherapy, with efficacy also reported in patients with PD-1 primary resistance.

Phase 1/2 safety data

Brenetafusp was generally well tolerated, showing a predictable, mechanism-driven safety profile as monotherapy and in combination. The most common treatment-related adverse events (TRAEs) (≥20%) – which were reversible and attenuated over time – included CRS (56%; predominantly low grade, reversible, and attenuated over time), rash (44%), pyrexia (44%), chills (38%), fatigue (31%), decreased lymphocyte count (38%), nausea (25%), and pruritus (44%). The most frequent Grade 3-4 TRAE was transient decreased lymphocyte count (25%). There were three TRAEs that led to treatment discontinuation (two monotherapy patients and one combination patient).

Phase 1/2 trial overview

The Phase 1/2 trial (NCT04262466; EudraCT 2019-004046-16) enrolled patients with unresectable or metastatic melanoma who were HLA-A*02:01-positive (central testing) and previously treated with anti-PD-(L)1 therapy. Brenetafusp was administered as a weekly IV infusion with step dosing to a target dose. Tumor response was assessed by RECIST every 9 weeks; ctDNA was assessed every three weeks.

Second poster: Effect of IL7 on T cell fitness and ImmTAC anti-tumor activity

In a second poster presented during ASCO (Free ASCO Whitepaper) 2026, the Company built on previously disclosed data regarding the importance of T cell fitness for the efficacy of ImmTAC molecules. The new data demonstrated the anti-tumor activity of these therapies may increase when combined with IL7 in vitro. This study showed that IL7 treatment expanded naïve/stem-like memory T cells, enhanced ImmTAC-mediated T cell induction of IFNγ secretion and tumor killing, as well as reduced immune checkpoint receptor expression and T cell exhaustion. Additionally, a single dose of IL7 resulted in a sustained increase in T cell fitness of cancer patients. Taken together, the in vitro and in vivo data are consistent with the hypothesis that a combination with IL7 may increase the anti-tumor activity of ImmTAC therapies.

Presentations details (ASCO 2026)

Title: Phase 1 evaluation of the PRAME-targeted ImmTAC brenetafusp in advanced melanoma (Mel). (Abstract number: 9527)
Session: Melanoma/Skin Cancers (Poster Board: 243)
Date and Time: May 31, 2026, 9:00 AM-12:00 PM CDT

Title: Effect of IL7 on ImmTAC-mediated killing by T cells in vitro and T cell fitness in patients (Abstract number: 2662)
Session: Developmental Therapeutics – Immunotherapy (Poster Board: 452)
Date and Time: May 30, 2026, 1:30 PM-4:30 PM CDT

(Press release, Immunocore, MAY 31, 2026, View Source [SID1234666248])