Adaptimmune Announces 70% of People with Advanced Synovial Sarcoma Who Respond to Afami-cel are Alive Two Years Post-Treatment; Data from Cohort 1 of SPEARHEAD-1 to be Presented at ASCO

Approximately 39% of patients had clinical responses after a single dose of afami-cel in Cohort 1 of the pivotal SPEARHEAD-1 trial and the median duration of response was ~12 months (CTOS 2022)

Median overall survival (mOS) was ~17 months

Patients with a RECIST response have a 12-month OS probability of 90% and 24-month OS probability of 70%, and the mOS for responders has not yet been reached

Historical outcomes are poor for advanced synovial sarcoma with a mOS of <12 months in the second line and beyond treatment setting

Philadelphia, Pennsylvania--(Newsfile Corp. - May 25, 2023) - Adaptimmune Therapeutics plc (NASDAQ: ADAP), a leader in cell therapy to treat cancer, will present data from Cohort 1 of its pivotal trial SPEARHEAD-1 (NCT04044768) for people with advanced synovial sarcoma at the American Society of Clinical Oncology's (ASCO) annual meeting. The poster, titled "The SPEARHEAD-1 trial of afamitresgene autoleucel: Analysis of overall survival in advanced synovial sarcoma," will be presented by Dr. Brian Van Tine of the Washington University School of Medicine at 1:15 p.m. CDT, Saturday, June 3^rd, in Hall A, Sarcoma track.

Dr. John Charlson of the Medical College of Wisconsin and Adaptimmune clinical trial investigator: "Engineered T-cell therapies, like afami-cel, have the potential to change the way we manage difficult to treat late-stage cancers like synovial sarcoma. The current standard-of-care treatments for synovial sarcoma were approved more than two decades ago, have limited efficacy and their dosing schedules, and resulting side effects often negatively impact patients' lives so there is a tremendous unmet need for novel, effective treatments."

Dennis Williams, Pharm.D., Adaptimmune's SVP of Late-Stage Development: "There is a high unmet need in late-stage solid tumor cancers and synovial sarcoma is no exception. We have reported an impressive response rate of ~39% among heavily pre-treated patients with advanced synovial sarcoma. We are seeing very meaningful survival data, especially in people who have a response after a single dose of afami-cel. Afami-cel is intended to be our first commercial product and we are developing additional products for other late-stage solid tumors including ovarian, bladder, and head & neck cancers."

Patients with advanced synovial sarcoma who received a single dose of afami-cel had meaningful survival, especially those patients with a RECIST response
There were 44 people with advanced synovial sarcoma who received afami-cel in Cohort 1 of the SPEARHEAD-1 trial. The overall response rate (ORR) by independent review per RECIST v1.1 among people with synovial sarcoma was ~39% (as reported at CTOS 2022) with 17 patients responding. The median duration of response was approximately 12 months (95% CI: 4.44 - not estimable).

An interim analysis was performed on March 29, 2023, when the median (range) follow-up time was 27.8 (16-38) months. The median overall survival was approximately 17 months and overall survival (OS) was significantly longer in patients who had a RECIST response, compared to non-responders, with a 12-month OS probability of 90% and 24-month OS probability of 70%. Median OS among responders has not been reached.

Afami-cel is on path to be Adaptimmune's first potential commercial product
Adaptimmune has completed submission of the preclinical (Part 1) and clinical modules (Part 2) of the Biologics License Application (BLA) for afami-cel for the treatment of synovial sarcoma, which is targeted for completion in mid-2023. This BLA is supported by data from Cohort 1 of the pivotal SPEARHEAD-1 trial, which has met its primary endpoint for efficacy. For afami-cel, the FDA has provided Orphan Drug Designation (ODD) for the treatment of soft tissues and Regenerative Medicine Advanced Therapy (RMAT) designation for the treatment of synovial sarcoma.

Overview of SPEARHEAD-1 trial design
SPEARHEAD-1 is a Phase 2, open-label trial for people with advanced synovial sarcoma or myxoid/round cell liposarcoma (MRCLS) to evaluate the efficacy, safety, and tolerability of afami-cel. Afami-cel SPEAR T-cells target MAGE-A4⁺ tumors. MAGE-A4 is highly expressed in synovial sarcoma and MRCLS in the context of HLA-A*02.

Approximately 90 patients were planned to be treated: 45 in Cohort 1 and 45 in Cohort 2. Enrollment in both cohorts is complete. The primary efficacy analysis is for Cohort 1 only. Cohort 2 will strengthen the efficacy and safety database and will aid in descriptive sub-group analyses.

Key eligibility criteria: ECOG performance status of 0 or 1; HLA*02 positive with MAGE-A4 expression in ≥ 30% of tumor cells ≥ 2+ by immunohistochemistry; aged ≥ 16 and ≤ 75 years; and patients must have received either an anthracycline- or ifosfamide-containing regimen. Eligible patients received afami-cel doses between 1-10 × 10^9 transduced T-cells after receiving lymphodepleting chemotherapy.

About Adaptimmune
Adaptimmune is a clinical-stage biopharmaceutical company focused on the development of novel cancer immunotherapy products for people with cancer. The Company's unique SPEAR (Specific Peptide Enhanced Affinity Receptor) T-cell platform enables the engineering of T-cells to target and destroy cancer across multiple solid tumors.

Forward-Looking Statements
This release contains "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995 (PSLRA). These forward-looking statements involve certain risks and uncertainties. Such risks and uncertainties could cause our actual results to differ materially from those indicated by such forward-looking statements, and include, without limitation: the success, cost and timing of our product development activities and clinical trials and our ability to successfully advance our TCR therapeutic candidates through the regulatory and commercialization processes. For a further description of the risks and uncertainties that could cause our actual results to differ materially from those expressed in these forward-looking statements, as well as risks relating to our business in general, we refer you to our Annual Report on Form 10-K filed with the Securities and Exchange Commission for the year ended December 31, 2022, our Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, and other filings with the Securities and Exchange Commission. The forward-looking statements contained in this press release speak only as of the date the statements were made and we do not undertake any obligation to update such forward-looking statements to reflect subsequent events or circumstances.

Adaptimmune Contact

Investor Relations
Juli P. Miller, Ph.D. - VP, Corporate Affairs and Investor Relations
T : +1 215 825 9310
M : +1 215 460 8920
Juli.Miller@adaptimmune.com

Media Relations
Dana Lynch, Senior Director of Corporate Communications
M: +1 267 990 1217
Dana.Lynch@adaptimmune.com

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