Background: Afamitresgene autoleucel (afami-cel) showed acceptable safety and promising efficacy in a phase 1 trial (NCT03132922). The aim of this study was to further evaluate the efficacy of afami-cel for the treatment of patients with HLA-A*02 and MAGE-A4-expressing advanced synovial sarcoma or myxoid round cell liposarcoma., Methods: SPEARHEAD-1 was an open-label, non-randomised, phase 2 trial done across 23 sites in Canada, the USA, and Europe. The trial included three cohorts, of which the main investigational cohort (cohort 1) is reported here. Cohort 1 included patients with HLA-A*02, aged 16-75 years, with metastatic or unresectable synovial sarcoma or myxoid round cell liposarcoma (confirmed by cytogenetics) expressing MAGE-A4, and who had received at least one previous line of anthracycline-containing or ifosfamide-containing chemotherapy. Patients received a single intravenous dose of afami-cel (transduced dose range 1·0 × 10 9 -10·0 × 10 9 T cells) after lymphodepletion. The primary endpoint was overall response rate in cohort 1, assessed by a masked independent review committee using Response Evaluation Criteria in Solid Tumours (version 1.1) in the modified intention-to-treat population (all patients who received afami-cel). Adverse events, including those of special interest (cytokine release syndrome, prolonged cytopenia, and neurotoxicity), were monitored and are reported for the modified intention-to-treat population. This trial is registered at ClinicalTrials.gov, NCT04044768; recruitment is closed and follow-up is ongoing for cohorts 1 and 2, and recruitment is open for cohort 3., Findings: Between Dec 17, 2019, and July 27, 2021, 52 patients with cytogenetically confirmed synovial sarcoma (n=44) and myxoid round cell liposarcoma (n=8) were enrolled and received afami-cel in cohort 1. Patients were heavily pre-treated (median three [IQR two to four] previous lines of systemic therapy). Median follow-up time was 32·6 months (IQR 29·4-36·1). Overall response rate was 37% (19 of 52; 95% CI 24-51) overall, 39% (17 of 44; 24-55) for patients with synovial sarcoma, and 25% (two of eight; 3-65) for patients with myxoid round cell liposarcoma. Cytokine release syndrome occurred in 37 (71%) of 52 of patients (one grade 3 event). Cytopenias were the most common grade 3 or worse adverse events (lymphopenia in 50 [96%], neutropenia 44 [85%], leukopenia 42 [81%] of 52 patients). No treatment-related deaths occurred., Interpretation: Afami-cel treatment resulted in durable responses in heavily pre-treated patients with HLA-A*02 and MAGE-A4-expressing synovial sarcoma. This study shows that T-cell receptor therapy can be used to effectively target solid tumours and provides rationale to expand this approach to other solid malignancies., Funding: Adaptimmune., Competing Interests: Declaration of interests EC reports participation in an advisory board for Adaptimmune; and research support paid to their institution for clinical trial activities from Adaptimmune, Novartis, Tracon, Boehringer Ingelheim, Merck, Bayer, Amgen, and Mirati. J-YB reports grants paid to institution from Netsarc+ and Euracan; and research support and honoraria from Adaptimmune and GSK. FT reports research support paid to institution for clinical trial activities from Adaptimmune, Achilles Therapeutics, T-knife Therapeutics, GSK, Immunocore, and Instil Bio; consulting fees from T-knife Therapeutics; speaker fees from Kite and Royal Marsden Hospital Cell Therapy Preceptorship; travel or meeting support from Kite; advisory board fees from Immatics, Bristol Myers Squibb (BMS), GSK, Janssen, Leucid, and Scenic Biotech; institutional advisory board fees from Pfizer; and is an unpaid panel member with Sarcoma UK, Cancer Research UK New Agents Committee, and the Medical Research Council Developmental pathway funding scheme. MA reports institutional support from Exelixis; consulting fees from Boehringer Ingelheim and Aadi; and honoraria from Regeneron, Deciphera, and Bayer. EF reports honoraria from Novartis, Alexion, Astellas, GSK, Gilead, and Sanofi; and travel or meeting support from Novartis, Alexion, Gilead, Sanofi, MSD, and Neovii. SJS reports consulting fees from Ceridwen Oncology; honoraria from Boehringer Ingelheim; travel or meeting support from Adaptimmune; and participated on advisory or data safety monitoring boards for GSK and Inhibrx. ARAR reports support from Adaptimmune, AbbVie, Amgen, Blueprint Medicines, BMS, Daiichi Sankyo, Deciphera Pharmaceuticals, GSK, Iterion Therapeutics, Karyopharm Therpaeutics, MedImmune, Merck, Neoleuki Therapeutics, Pfizer, Rain Therapeutics, Roche/Genentech, and Symphogen; honoraria from Medison; and participated on advisory or data safety monitoring boards for Adaptimmune, Bayer, GSK, Inhibrx, and Medison. SMS reports institutional support from Adaptimmune, Boehringer Ingelheim, GSK, Rain Oncology, Shanghai Pharma, and TRACON; royalties or licenses from UpToDate; participated on an advisory or data safety monitoring board for Bioatla; and is an unpaid National Comprehensive Cancer Network Soft Tissue Sarcoma committee member. CMVM reports institutional support from Adaptimmune; consulting fees from Deciphera; honoraria from Bayer; travel or meeting support from PharmaMar; and participation on advisory or data safety monitoring boards for PharmaMar, Bayer, and Boehringer Ingelheim. MJW reports consulting fees from Adaptimmune, Deciphera, Aadi, Epizyme, and PharmaEssentia. JG reports support from Adaptimmune for this study. VM reports consulting fees from Roche, Bayer, Pieris, BMS, Janssen, Basilea, Regeneron/Sanofi, and Nanobiotix; and institutional support from AbbVie, AceaBio, Adaptimmune, ADC Therapeutics, Aduro, Agenus, Amcure, Amgen, Astellas, AstraZeneca, Bayer, Beigene, BioInvent International, BMS, Boehringer Ingelheim, Boston, Celgene, Daiichi Sankyo, Debiopharm, Eisai, e-Therapeutics, Exelisis, Forma Therapeutics, Genmab, GSK, Harpoon, Hutchison, Immutep, Incyte, Inovio, Iovance, Janssen, Kyowa Kirin, Lilly, Loxo, MedSir, Menarini, Merck, Merus, Millenium, MSD, Nanobiotix, Nektar, Novartis, Odonate Therapeutics, Pfizer, PharmaMar, Pricipia, PsiOxus, Puma, Regeneron, Rigontec, Roche, Sanofi, Sierra Oncology, Synthon, Taiho, Takeda, Tesaro, Transgene, Turning Point Therapeutics, and Upsher-Smith. LH, TW, JB, AS, LF, EVW, EN, DW, RW, J-MN, SR, and EE are employees of, and have stock options in, Adaptimmune. SB, CM, and CL were employees of Adaptimmune at the time of the study. VLK reports institutional support from Adaptimmune, Deciphera, Plexxikon, Advenchen, Boehringer Ingelheim, and TRACON; consulting fees from Epizyme; and honoraria from Deciphera. WDT reports institutional support from Adaptimmune; consulting and travel fees from Eli Lilly; consulting fees from C4 Therapeutics, Daiichi Sankyo, Deciphera, Adcendo, Ayala Pharmaceuticals, Kowa, Servier, Bayer Pharmaceuticals, Epizyme, Cogent, Medpacto, Foghorn Therapeutics, Amgen, AmMax Bio, Boehringer Ingelheim, BioAtla, Inhibrx, PharmaEssentia, Avacta, Ipsen, Sonata, Curadev, Nuvation Bio, and Abbisko; has patents pending for companion diagnostics with Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center (New York, NY, USA); is on advisory boards of Innova Therapeutics and the Osteosarcoma Institute; is on the advisory board and holds stock in Certis Oncology Solutions; and is a co-founder and has stock in Atropos Therapeutics. JAC reports consulting fees from Adaptimmune and Deciphera; and honoraria from Adaptimmune. BAVT reports a research grant from Polaris; royalties or licenses from Accuronix Therapeutics; consulting fees from Bayer, Deciphera, GIST Expert Interview Project, Daiichi Sankyo, EcoR1, Advenchen, Putnam, Salarius Pharmaceuticals, Boxer Capital, Acuta Capital Partners, Aadi, Race Oncology, Hinge Bio, Kronos Bio, and Sonata Therapeutics; honoraria from Total Health Conference and Iterion Therapeutics; travel or meeting support from Adaptimmune, Kronos Bio, Advenchen Laboratories, and Polaris; has a patent with Accuronix Therapeutics; participated in advisory boards for Apexigen, Daiichi Sankyo, Epizyme, Bayer, PTC Therapeutics, Aadi Biosciences, Boehringer Ingelheim, Agenus, Regeneron Pharmaceuticals, Exp, Advenchen, EcoR1 Capital, Curis, and Inhibrx; and is a board member for Polaris. GDD reports institutional support from Adaptimmune, Bayer, Novartis, PharmaMar, and Daiichi-Sankyo; is a co-founder and scientific advisory board member with minor equity holding in IDRx; is a consultant or scientific advisory board member with minor equity holding in G1 Therapeutics, Caris Life Sciences, Erasca Pharmaceuticals, RELAY Therapeutics, Bessor Pharmaceuticals, CellCarta, Ikena Oncology, Kojin Therapeutics, Aadi Biosciences, Acrivon Therapeutics, Blueprint Medicines, Tessellate Bio, and Boundless Bio; and is a scientific consultant for EMD-Serono/Merck KGaA, WCG/Arsenal Capital, Rain Therapeutics, and Minghui Pharmaceuticals. SPD'A reports institutional support from Adaptimmune for this study; grants, contracts, consulting fees, and honoraria from EMD Serono, Amgen, Nektar, Immune Design, GlaxoSmithKline, Incyte, Merck, Adaptimmune, Immunocore, Pfizer, Servier, Rain Therapeutics, GI Innovations, and Aadi Biosciences; travel support from Adaptimmune, EMD Serono, and Nektar; participation on advisory boards for GlaxoSmithKline, Nektar, Adaptimmune, and Merck; and a leadership or fiduciary role at the Connective Tissue Oncology Society in 2023–24. SA reports institutional support from Adaptimmune for this study; and institutional support from TRACON Pharma, Ayala Pharmaceuticals, Cogent Biosciences, InhibRx, Rain Therapeutics, Trillium Therapeutics, Boehringer Ingelheim, Salarius Pharmaceuticals, Theseus Pharmaceuticals, Monopar Therapeutics, C4 Therapeutics, Noxopharm, Jazz Pharmaceuticals, Shanghai Pharma, and PharmaMar. KNG reports participation in advisory boards for Adaptimmune, Daiichi Sankyo, Boehringer Ingelheim, and Deciphera. MD reports consultancy fees and advisory board fees from Deciphera, Aadi Bioscience, and Daiichi Sankyo. BAW reports consultancy fees from Springworks, Deciphera, Epizyme, Adcendo, Polaris, Boehringer Ingelheim, and AADi, research funding from Exelixis, and travel support from Agenus. All other authors declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)