Immunocore presents promising initial Phase 1 data for first off-the-shelf TCR therapy targeting PRAME at the ESMO 2022 Congress

• Data from Phase 1 dose escalation trial shows IMC-F106C, a PRAME×CD3 ImmTAC, activates T cells and is well tolerated
• Durable RECIST responses and reduction in circulating tumor DNA (ctDNA) observed across multiple solid tumors
• Four expansion arms enrolling in cutaneous melanoma, ovarian, lung, and endometrial cancers
• Company to host a live webcast and conference call today at 12:30 PM EDT / 6:30 PM CEST

(OXFORDSHIRE, England & CONSHOHOCKEN, Penn. & ROCKVILLE, Md., US, 9 September 2022) Immunocore Holdings plc (Nasdaq: IMCR), a commercial-stage biotechnology company pioneering the development of a novel class of T cell receptor (TCR) bispecific immunotherapies designed to treat a broad range of diseases, including cancer, autoimmune and infectious diseases, has released today initial Phase 1 data for the first off-the-shelf ImmTAC^® targeting PRAME, demonstrating that IMC-F106C is well tolerated and resulted in durable responses across multiple solid tumor types.

The initial data from the ongoing Phase 1 dose escalation trial of IMC-F106C is the subject of a presentation today at 4:40 PM CEST/10:40 AM EDT, in the Investigational Immunotherapy Proffered Paper session at the European Society for Medical Oncology (ESMO) Congress. The presentation can be accessed in the ‘News & Events’ section of the Investor Relations section of the Company’s website.

“The durable responses in heavily pre-treated patients show that our PRAME-targeted bispecific therapy, IMC-F106C, can deliver meaningful benefits to patients across a range of cancer types,” said Bahija Jallal, Chief Executive Officer of Immunocore. “Based on this promising data, we have initiated expansion arms in multiple tumor types to further assess the efficacy.”

Initial Phase 1 Clinical Data
As of 18 July 2022, 55 patients have been treated across 10 dose cohorts. IMC-F106C was well-tolerated, with treatment-related adverse events (AEs) that were manageable and consistent with the mechanism of action. The most frequent treatment-related AE reported was cytokine release syndrome (CRS), which was mostly Grade 1 (none were Grade ≥3) and occurred predominantly during the initial three doses. None of the related AEs led to treatment discontinuation or patient death.

Dr. Omid Hamid, Chief, Translational Research and Immunotherapy, Co-Director, Melanoma Therapeutics at Cedars-Sinai Cancer at the Angeles Clinic and Research Institute, said: “ImmTAC therapies are designed to provide potent and target-specific T-cell response, overcoming resistance in immune excluded tumors. Through redirection and activation of non-tumor-specific T cells, as shown in this trial with IMC-F106C, we can influence a diverse range of tumors leading to durable response. This trial shows tolerability and activity in a wide range of tumors, including checkpoint inhibitor pre-treated patients. I look forward to upcoming cohorts in combination with checkpoint inhibitors and chemotherapy.”

Doses of ≥ 20 mcg were clinically active and had consistent and robust interferon gamma induction, a specific marker of T cell activation. Most of the patients in these active dose cohorts were enrolled without prospective PRAME testing. In these patients, PRAME expression was analyzed retrospectively; the vast majority were positive, and the average expression was high (median H score 188).

In the clinically active dose cohorts, durable partial responses (PR) were observed in 2/6 patients with cutaneous melanoma, 2/4 with ovarian cancer and 3/6 with tebentafusp-naïve uveal melanoma (UM) (0/5 response in patients with UM who had progressed on prior tebentafusp). All ovarian patients were platinum-resistant, and all cutaneous melanoma patients had progressed on prior anti-PD1 and anti-CTLA4. Six of the seven PRs are still ongoing, including two for over seven months. Ten additional efficacy evaluable patients across four other tumor types had a best RECIST response of stable disease or progressive disease. A majority of patients evaluable for circulating tumor DNA (ctDNA) had at least a 50% reduction.

Ongoing Expansion Arms in Four Cancer Types
The Company has initiated patient enrollment into four expansion arms in cutaneous melanoma, ovarian, non-small cell lung cancer (NSCLC), and endometrial cancers. The IMC-F106C-101 trial is adaptive and includes the option for Phase 2 expansion, allowing for approximately 100 patients treated per tumor type in the Phase 1 and 2 expansion arms. Dose escalation continues in additional solid tumors as well as plans for combination arms with standards-of-care.

About the Trial (IMC-F106C-101)
The Phase 1 dose escalation trial was designed to determine the maximum tolerated dose (MTD), as well as to evaluate the safety, preliminary anti-tumor activity and pharmacokinetics of IMC-F106C, a bispecific protein built on Immunocore’s ImmTAC^® technology, and the Company’s first molecule to target the PRAME antigen.

Following pre-screening for the HLA-A*02:01 allele and, where required, for PRAME expression, patients were infused on a weekly dosing regimen, with intra-patient escalation during the initial three weeks. Tumor types with high PRAME prevalence were enrolled regardless of PRAME expression testing, which was evaluated retrospectively. Tumor types with lower PRAME prevalence required testing for PRAME expression prior to study entry. Patients were first scanned at nine weeks, and every nine weeks thereafter.

Conference Call Information
Immunocore will host a live webcast and conference call today beginning at 12:30 PM EDT to discuss the results with Dr. Omid Hamid, Chief, Translational Research and Immunotherapy, Co-Director, Melanoma Therapeutics at Cedars-Sinai Cancer at the Angeles Clinic and Research Institute. A live webcast of the conference call will be available under ‘News & Events’ in the Investor Relations section of Immunocore Holdings’ website at www.immunocore.com. The presentation from today’s call and the archived webcast will be available on Immunocore’s website after the conference call concludes and will be available for 30 days following the call.