KIMMTRAK doubles the likelihood of being alive at five years for first line HLA-A*02:01+ patients with metastatic uveal melanoma

OS benefit observed across key subgroups, including patients with high tumor burden, elevated LDH, and extrahepatic disease as well as those with best response of progressive disease

This is the longest OS follow-up in a randomized trial in metastatic uveal melanoma and for any T cell engager in a solid tumor

(OXFORDSHIRE, England & GAITHERSBURG, Md., & RADNOR, Penn., US, 19 April 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, today announced that KIMMTRAK^® (tebentafusp-tebn) five-year overall survival (OS) was presented in an oral session at the American Association for Cancer Research (AACR) 2026 meeting.

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 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

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About ImmTAC^® molecules for cancer

Immunocore’s proprietary T cell receptor (TCR) technology generates a novel class of bispecific biologics called ImmTAC (Immune mobilizing monoclonal TCRs Against Cancer) molecules that are designed to redirect the immune system to recognize and kill cancerous cells. ImmTAC molecules are soluble TCRs engineered to recognize intracellular cancer antigens with ultra-high affinity and selectively kill these cancer cells via an anti-CD3 immune-activating effector function. Based on the demonstrated mechanism of T cell infiltration into human tumors, the ImmTAC mechanism of action holds the potential to treat hematologic and solid tumors, regardless of mutational burden or immune infiltration, including immune “cold” low mutation rate tumors.

About Uveal Melanoma

Uveal melanoma is a rare and aggressive form of melanoma, which affects the eye. This is the most common primary intraocular malignancy in adults and up to 50% of people with uveal melanoma will eventually develop metastatic disease. Unresectable or metastatic uveal melanoma typically has a poor prognosis and had no approved treatment until KIMMTRAK.

About KIMMTRAK^®

KIMMTRAK is a novel bispecific protein comprised of a soluble T cell receptor fused to an anti-CD3 immune-effector function. KIMMTRAK specifically targets gp100, a lineage antigen expressed in melanocytes and melanoma. This is the first molecule developed using Immunocore’s ImmTAC technology platform, designed to redirect and activate T cells to recognize and kill tumor cells. KIMMTRAK has been approved for the treatment of HLA-A*02:01-positive adult patients with unresectable or metastatic uveal melanoma in the United States, European Union, Canada, Australia, and the United Kingdom.

IMPORTANT SAFETY INFORMATION

Cytokine Release Syndrome (CRS), which may be serious or life-threatening, occurred in patients receiving KIMMTRAK. Monitor for at least 16 hours following first three infusions and then as clinically indicated. Manifestations of CRS may include fever, hypotension, hypoxia, chills, nausea, vomiting, rash, elevated transaminases, fatigue, and headache. CRS occurred in 89% of patients who received KIMMTRAK, with 0.8% being grade 3 or 4. Ensure immediate access to medications and resuscitative equipment to manage CRS. Ensure patients are euvolemic prior to initiating the infusions. Closely monitor patients for signs or symptoms of CRS following infusions of KIMMTRAK. Monitor fluid status, vital signs, and oxygenation level and provide appropriate therapy. Withhold or discontinue KIMMTRAK depending on persistence and severity of CRS.

Skin Reactions

Skin reactions, including rash, pruritus, and cutaneous edema occurred in 91% of patients treated with KIMMTRAK. Monitor patients for skin reactions. If skin reactions occur, treat with antihistamine and topical or systemic steroids based on persistence and severity of symptoms. Withhold or permanently discontinue KIMMTRAK depending on the severity of skin reactions.

Elevated Liver Enzymes

Elevations in liver enzymes occurred in 65% of patients treated with KIMMTRAK. Monitor alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total blood bilirubin prior to the start of and during treatment with KIMMTRAK. Withhold KIMMTRAK according to severity.

Embryo-Fetal Toxicity

KIMMTRAK may cause fetal harm. Advise pregnant patients of potential risk to the fetus and patients of reproductive potential to use effective contraception during treatment with KIMMTRAK and 1 week after the last dose.

The most common adverse reactions (=30%) in patients who received KIMMTRAK were cytokine release syndrome, rash, pyrexia, pruritus, fatigue, nausea, chills, abdominal pain, edema, hypotension, dry skin, headache, and vomiting. The most common (=50%) laboratory abnormalities were decreased lymphocyte count, increased creatinine, increased glucose, increased AST, increased ALT, decreased hemoglobin, and decreased phosphate.

For more information, please see full Summary of Product Characteristics (SmPC) or full U.S. Prescribing Information (including BOXED WARNING for CRS).

About KIMMTRAKConnect

Immunocore is committed to helping patients who need KIMMTRAK obtain access via its KIMMTRAKConnect program. The US program provides services with dedicated nurse case managers who provide personalized support, including educational resources, financial assistance, and site of care coordination. To learn more, visit KIMMTRAKConnect.com or call 844-775-2273.

About Immunocore

Immunocore is a commercial-stage biotechnology company pioneering the development of a novel class of TCR bispecific immunotherapies called ImmTAX – Immune mobilizing monoclonal TCRs Against X disease – designed to treat a broad range of diseases, including cancer, autoimmune diseases and infectious diseases. Leveraging its proprietary, flexible, off-the-shelf ImmTAX platform, Immunocore is developing a deep pipeline in multiple therapeutic areas, including clinical and pre-clinical programs? in oncology, infectious diseases, and autoimmune diseases. The Company’s most advanced oncology TCR therapeutic, KIMMTRAK, has been approved for the treatment of HLA-A*02:01-positive adult patients with unresectable or metastatic uveal melanoma in the United States, European Union, Canada, Australia, and the United Kingdom.

Forward Looking Statements

This press release contains “forward-looking statements” within the meaning of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Words such as “may”, “will”, “believe”, “expect”, “plan”, “anticipate”, “aim”, “continue”, “target” and similar expressions (as well as other words or expressions referencing future events or circumstances) are intended to identify forward-looking statements. All statements, other than statements of historical facts, included in this press release are forward-looking statements. These statements include, but are not limited to, statements regarding the Company’s strategic priorities for 2026, including the Company’s ability to grow its commercial franchise with new melanoma indications, to reach more patients and to deliver on KIMMTRAK’s lifecycle management program; the Company’s ability to expand beyond melanoma into other tumor types and to realize growth opportunities beyond oncology; the potential of the Company’s melanoma franchise; the Company’s ability to advance its clinical pipeline; expectations regarding sales growth; expectations regarding the design, progress, timing, enrollment, randomization, scope, expansion, and results of the Company’s and its collaborators’ existing and planned clinical trials; the timing and sufficiency of clinical trial outcomes to support potential approval of any of the Company’s product candidates or those of, or combined with, its collaboration partners; the Company’s ability to leverage its expertise and dataset to inform clinical development; the expected submission of clinical trial applications or investigational new drug applications; the potential regulatory approval, expected clinical benefits and availability of the Company’s product candidates; and the Company’s preliminary unaudited cash, cash equivalents and marketable securities as of December 31, 2025. Any forward-looking statements are based on management’s current expectations and beliefs of future events and are subject to a number of risks and uncertainties that could cause actual events or results to differ materially and adversely from those set forth in or implied by such forward-looking statements, many of which are beyond the Company’s control. These risks and uncertainties include, but are not limited to, the impact of worsening macroeconomic conditions, including as a result of health epidemics or pandemics, war in Ukraine, the conflict in the Middle East, or global geopolitical tension, on the Company’s business, financial position, strategy and anticipated milestones, including Immunocore’s ability to conduct ongoing and planned clinical trials; the Company’s ability to obtain a clinical supply of current or future product candidates or commercial supply of KIMMTRAK or any future approved products; the Company’s ability to obtain and maintain regulatory approval of KIMMTRAK and its other product candidates; the Company’s ability and plans in continuing to establish and expand a commercial infrastructure and to successfully launch, market and sell KIMMTRAK and any future approved products; the Company’s ability to successfully expand the approved indications for KIMMTRAK or obtain marketing approval for KIMMTRAK in additional geographies in the future; the delay of any current or planned clinical trials, whether due to patient enrollment delays or otherwise; the Company’s ability to successfully demonstrate the safety and efficacy of its product candidates and gain approval of its product candidates on a timely basis, if at all; competition with respect to market opportunities; unexpected safety or efficacy data observed during preclinical studies or clinical trials; actions of regulatory agencies, which may affect the initiation, timing and progress of clinical trials or future regulatory approval; Immunocore’s need for and ability to obtain additional funding, on favorable terms or at all, including as a result of worsening macroeconomic conditions, including changes in inflation and interest rates and unfavorable general market conditions, and the impacts thereon of the war in Ukraine, the conflict between Hamas and Israel, and global geopolitical tension; Immunocore’s ability to obtain, maintain and enforce intellectual property protection for KIMMTRAK or any of its product candidates it or its collaborators are developing; and the success of Immunocore’s current and future collaborations, partnerships or licensing arrangements. These and other risks and uncertainties are described in greater detail in the section titled "Risk Factors" in Immunocore’s filings with the Securities and Exchange Commission, including Immunocore’s most recent Annual Report on Form 10-K for the year ended December 31, 2024 filed with the Securities and Exchange Commission on February 26, 2025, as well as discussions of potential risks, uncertainties, and other important factors in the Company’s subsequent filings with the SEC. All information in this press release is as of the date of the release, and the Company undertakes no duty to update this information, except as required by law. In addition, as the reported cash and cash equivalents in this press release are preliminary, have not been audited and are subject to change pending completion of the Company’s audited financial statements for the year ended December 31, 2025, it is possible that the Company or its independent registered public accounting firm may identify items that require the Company to make adjustments to the amount included in this release, and such changes could be material. Additional information and disclosures would also be required for a more complete understanding of the Company’s financial position and results of operations as of December 31, 2025.

Contact Information

Immunocore
Sébastien Desprez, Head of Communications
T: +44 (0) 7458030732
E: sebastien.desprez@immunocore.com
Follow on LinkedIn: @Immunocore

Investor Relations
Morgan Morse
T: +1 (215) 384-4781
E: ir@immunocore.com

¹ Rantala ES et al. Overall survival after treatment for metastatic uveal melanoma: a systematic review and meta-analysis. Melanoma Res. 2019 Dec;29(6):561-568. doi: 10.1097/CMR.0000000000000575.