Data announced from Phase II IGNYTE-ESO trial of lete-cel in people with synovial sarcoma or myxoid/round cell liposarcoma

The primary analysis data are being presented at the Connective Tissue Oncology Society (CTOS) 2024 Annual Meeting which takes place from November 13-16, 2024 in San Diego.

Based on these positive data, Adaptimmune plans to initiate a rolling Biologics License Application (BLA) submission for lete-cel for the treatment of advanced or metastatic synovial sarcoma and MRCLS by the end of 2025. Lete-cel builds on the potential of Adaptimmune's sarcoma franchise to change the way solid tumors are treated using cell therapies, more than doubling the addressable patient population eligible for Adaptimmune cell therapies to also include NY-ESO-1 positive synovial sarcoma and MRCLS solid tumors.

Elliot Norry, MD, Adaptimmune's Chief Medical Officer: "We are thrilled to see that 42% of patients with synovial sarcoma or MRCLS responded to treatment with lete-cel, following prior treatment with currently available therapies. Responses were durable across both indications, with an overall median duration of response greater than 18 months for people with synovial sarcoma and greater than one year for MRCLS. These data underscore lete-cel's potential to transform the lives of people with these cancers who have a poor prognosis and few treatment options. We look forward to presenting our findings at CTOS and initiating a rolling Biologics License Application for lete-cel in 2025 for the treatment of both synovial sarcoma and MRCLS, building on the potential of our sarcoma franchise."

The primary analysis includes data from 64 people with synovial sarcoma or MRCLS who received lete-cel manufactured with the proposed commercial manufacturing process in the IGNYTE-ESO trial. In the analysis, 27/64 (42%) people with synovial sarcoma or MRCLS had RECISTv1.1 responses by independent review, with six complete responses and 21 partial responses. The response rate was 14/34 (41%) for people with synovial sarcoma and 13/30 (43%) for people with MRCLS. The median duration of response (DoR) was 12.2 months (95% CI 6.8, 19.5). In synovial sarcoma, the median duration of response was 18.3 months (95% CI 3.3, -). In MRCLS, the median duration of response was 12.2 months (95%, CI 5.3, -). The median progression free survival (PFS) was 5.3 months (95% CI 4.0, 8.0).

Safety findings were consistent with the known profile of lete-cel from previous data. All patients experienced treatment-emergent adverse events: cytopenias, cytokine release syndrome (CRS) and rash were the most common adverse events. Overall, toxicities were manageable, and consistent with an acceptable benefit to risk profile.

CTOS presentation details:

• Title: Planned Analysis of the Pivotal IGNYTE-ESO Trial of Lete-Cel in Patients with Synovial Sarcoma or Myxoid/Round Cell Liposarcoma (Paper 84)
• Session 12: Immunology: Podium presentation
• Presenter: Sandra D'Angelo, MD, Sarcoma Medical Oncologist and Cell Therapist, Memorial Sloan Kettering Cancer Center
• Date/Time: Saturday, November 16, 10:30 AM - 12:00 PM PT / 1:30 - 3:00 PM ET

About the IGNYTE-ESO trial; IGNYTE-ESO is a pivotal, Phase II, open-label trial for people with previously treated, advanced synovial sarcoma or MRCLS to evaluate the efficacy, safety, and tolerability of lete-cel. Lete-cel's engineered TCR T-cells target NY-ESO-1+ tumors. NY-ESO-1 is a solid tumor antigen highly expressed in synovial sarcoma and MRCLS.