Background: Tebentafusp, a bispecific (gp100×CD3) ImmTAC, significantly improved overall survival (OS) outcomes for HLA-A*02:01+ adult patients with untreated metastatic uveal melanoma (mUM) and showed promising survival in previously treated mUM with 1-year OS of 62% in the primary analysis of study IMCgp100-102. Here we report long-term outcomes from this phase 1/2 study in pretreated mUM., Patients and Methods: Patients with previously treated mUM received tebentafusp weekly intravenous at 20 µg dose 1, 30 µg dose 2 and either 54, 64, 68, or 73 µg (phase 1) or 68 µg (phase 2) dose 3+. The primary objective was overall response rate. Secondary objectives included OS and safety. OS was estimated by Kaplan-Meier methods. Association between OS and baseline covariates, on-treatment Response Evaluation Criteria in Solid Tumors (RECIST) response, baseline tumor biopsy and circulating-tumor DNA (ctDNA) changes were assessed., Results: 146 patients were treated with tebentafusp: 19 in phase 1 and 127 in phase 2. With a median follow-up duration of 48.5 months, the median OS was 17.4 months (95% CI, 13.1 to 22.8), and the 1-year, 2-year, 3-year and 4-year OS rates were 62%, 40%, 23% and 14%, respectively. Improved survival was associated with lower ctDNA baseline levels and greater ctDNA reductions by week 9 on-treatment, with 100% 1-year, 73% 2-year and 45% 3-year OS rates for patients with ctDNA clearance. Baseline gp100 expression was not associated with survival, despite more RECIST responses among patients with higher expression. No new safety signals were reported with long-term dosing., Conclusions: This study represents the longest follow-up of a Tcell receptor bispecific to date and confirms the durable survival benefits achieved with tebentafusp in previously treated mUM with good tolerability long-term. A role for ctDNA reduction as an early indicator of clinical benefit was again suggested for patients treated with tebentafusp., Competing Interests: Competing interests: JJS discloses PI on clinical trial: Amgen, AstraZeneca, Bristol-Myers Squibb, Delcath Systems, Merck, Replimune, Transgene; Research Grant/Contract: AstraZeneca, Bristol-Myers Squibb, Immunocore; Consultant/Advisory Board: Bristol-Myers Squibb, Delcath Systems, Immunocore, Merck; Congress attendance: Bristol-Myers Squibb, Merck. RDC discloses Consultant: Aura Biosciences, Castle Biosciences, Chimeron, Immunocore, InxMed, Iovance, Merck, Oncosec, Pierre Fabre Pharmaceuticals Inc., PureTech Health, Regeneron Pharmaceuticals, Rgenix, Sanofi Genzyme, Sorrento Therapeutics, TriSalus; Stock Option: Aura Biosciences, Chimeron, Rgenix. MOB discloses Consultant/Advisory Board: Adaptimmune, Bristol-Myers Squibb Canada, GlaxoSmithKline, Immunocore, Instil Bio, Iovance Biotherapeutics, Merck, Novartis, Pfizer, Sanofi Pasteur Inc., Sun Pharma, IDEAYA Bio, Medison, Regeneron and Iovance.; Safety Review Committee: GlaxoSmithKline, Adaptimmune; Research Funding: Merck, Takara Bio, Novartis. ANS discloses Grant/Contract: Bristol-Myers Squibb, Immunocore, Novartis, Targovax, Pfizer, Alkermes, Checkmate Pharmaceuticals, Foghorn Therapeutics, Linnaeus Therapeutics, Prelude Therapeutics, Iovance Biotherapeutics, Bristol-Myers Squibb, Immunocore, Novartis, Pfizer, Polaris, Xcovery. JCH discloses Speaker: Amgen, Bristol-Myers Squibb, GSK, Immunocore, Merck Sharp and Dohme, Novartis Pharma, Pierre Fabre, Sanofi-Aventis U.S. LLC; Sunpharma; Research grant/contract: Bristol-Myers Squibb, Sanofi, Sunpharma; Consultant/Advisory Board: Bristol-Myers Squibb, GSK, Immunocore, Merck Sharp and Dohme, Novartis Pharma, Pierre Fabre Pharmaceuticals Inc., Philogen, Onkowissen, Sanofi-Aventis U.S. LLC, Sun Pharmaeutical Industries Inc. AI discloses Research Funding to Institution: Dynavax, GSK/Sarah Cannon, Immunocore, Merck, Neon Therapeutics/Sarah Cannon, Checkmate Pharmaceuticals. LH-A discloses Advisory/Consulting: BMS, Castle Bioscience; Research Funding to Institution: BMS, AstraZeneca, Merck, Amgen, Roche, Regeneron, Novartis, Immunocore, Merck-EMD, Corvus, Polynoma, Genentech, Foghorn. PN discloses Data and Safety Monitoring: 4SC, Achilles; Consultant/Advisory Board: 4SC, Bristol-Myers Squibb, Immunocore, Merck, Merck Sharp and Dohme, Novartis, Pfizer; Research Grant/Contract: Immunocore. OH discloses Contract: Aduro biotech, Akeso biotech, Amgen Inc., Beigene Ltd, Bioatla, Bristol-Myers Squibb, Genentech USA, Inc., GlaxoSmithKline, Idera Pharmaceuticals, Immunocore, Incyte Corporation, Janssen Global Services, LLC, Merck, Next Cure Inc., Novartis, Pfizer, Regeneron Pharmaceuticals Inc., Sanofi, Seattle Genetics, Tempus, Zelluna Immunotherapy; Contracted Research for Institution: Aduro biotech, Akeso biotech, Amgen Inc., Arcus Biosciences, Bioatla, Bristol-Myers Squibb, CytomX Therapeutics, Exelixis Inc., Genentech, GlaxoSmithKline, Idera Pharmaceuticals, Immunocore, Incyte Corporation, Iovance Biotherapeutics, Merck, Merck Serono, Moderna, NextCure Inc., Novartis, Pfizer, Regeneron Pharmaceuticals, Sanofi Genzyme, Seattle Genetics, Torque Pharma, Zelluna Immunotherapy; Speakers Bureau: Bristol-Myers Squibb, Novartis, Pfizer. MR discloses employment and stock ownership in Syapse Inc. DBJ discloses Advisory Boards/Consultant: Bristol-Myers Squibb, Catalyst Biopharma, Iovance, Jansen, Mallinckrodt, Merck, Mosaic ImmunoEngineering, Novartis, Oncosec, Pfizer, Targovax, and Teiko; Research Funding: Bristol-Myers Squibb, Incyte. JJL discloses DSMB: AbbVie, Agenus, Amgen, Immutep, Evaxion; Scientific Advisory Board: (no stock) 7 Hills, Affivant, Bright Peak, Exo, Fstar, Inzen, RefleXion, Xilio (stock) Actym, Alphamab Oncology, Arch Oncology, Duke Street Bio, Kanaph, Mavu, NeoTx, Onc.AI, OncoNano, physIQ, Pyxis, Saros, STipe, Tempest; Consultancy with compensation: AbbVie, Agenus, Alnylam, Atomwise, Bayer, Bristol-Myers Squibb, Castle, Checkmate, Codiak, Crown, Cugene, Curadev, Day One, Eisai, EMD Serono, Endeavor, Flame, G1 Therapeutics, Genentech, Gilead, Glenmark, HotSpot, Kadmon, KSQ, Janssen, Ikena, Inzen, Immatics, Immunocore, Incyte, Instil, IO Biotech, Macrogenics, Merck, Mersana, Nektar, Novartis, Partner, Pfizer, Pioneering Medicines, PsiOxus, Regeneron, Replimmune, Ribon, Roivant, Servier, STINGthera, Synlogic, Synthekine; Research Support: (all to institution for clinical trials unless noted) AbbVie, Astellas, AstraZeneca, Bristol-Myers Squibb, Corvus, Day One, EMD Serono, Fstar, Genmab, Ikena, Immatics, Incyte, Kadmon, KAHR, Macrogenics, Merck, Moderna, Nektar, Next Cure, Numab, Palleon, Pfizer, Replimmune, Rubius, Servier, Scholar Rock, Synlogic, Takeda, Trishula, Tizona, Xencor; Patents: (both provisional) Serial #15/612,657 (Cancer Immunotherapy), PCT/US18/36052 (Microbiome Biomarkers for Anti-PD-1/PD-L1 Responsiveness: Diagnostic, Prognostic and Therapeutic Uses Thereof). EE discloses Advisory Boards/Consultant: Immunocore. SL discloses Consulting: Bayer, Immunocore; Expenses: Bayer. LC discloses Employment and Stock: Immunocore. CH discloses Stock: Amgen Inc., Macrogenics; Employment: Immunocore. TS discloses advisory/consulting: Immunocore, Castle Biosciences; research funding to institution (clinical trials): Immunocore, Verastem, IDEAYA, TriSalus, and BMS., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)