Introduction: S1400F is a non-match substudy of Lung Cancer Master Protocol (Lung-MAP) evaluating the immunotherapy combination of durvalumab and tremelimumab to overcome resistance to anti-programmed death ligand 1 (PD-(L)1) therapy in patients with advanced squamous lung carcinoma (sq non-small-cell lung cancer (NSCLC))., Methods: Patients with previously treated sqNSCLC with disease progression after anti-PD-(L)1 monotherapy, who did not qualify for any active molecularly targeted Lung-MAP substudies, were eligible. Patients received tremelimumab 75 mg plus durvalumab 1500 mg once every 28 days for four cycles then durvalumab alone every 28 days until disease progression. The primary endpoint was the objective response rate (RECIST V.1.1). Primary and acquired resistance cohorts, defined as disease progression within 24 weeks versus ≥24 weeks of starting prior anti-PD-(L)1 therapy, were analyzed separately and an interim analysis for futility was planned after 20 patients in each cohort were evaluable for response., Results: A total of 58 eligible patients received drug, 28 with primary resistance and 30 with acquired resistance to anti-PD-(L)1 monotherapy. Grade ≥3 adverse events at least possibly related to treatment were seen in 20 (34%) patients. The response rate in the primary resistance cohort was 7% (95% CI 0% to 17%), with one complete and one partial response. No responses were seen in the acquired resistance cohort. In the primary and resistance cohorts the median progression-free survival was 2.0 months (95% CI 1.6 to 3.0) and 2.1 months (95% CI 1.6 to 3.2), respectively, and overall survival was 7.7 months (95% CI 4.0 to 12.0) and 7.6 months (95% CI 5.3 to 10.2), respectively., Conclusion: Durvalumab plus tremelimumab had minimal activity in patients with advanced sqNSCLC progressing on prior anti-PD-1 therapy. Trial registration number NCT03373760., Competing Interests: Competing interests: The authors’ financial disclosures include: NBL received travel support and institutional research funding from Astra Zeneca and personal fees (CME lectures) from MSD and BMS, unrelated to the study. MR salary support from Hope Foundation, participation on DMSB for AstraZeneca, unrelated to study. NR received personal fees from Abbvie, Apricity, AstraZeneca, Boehringer Ingelheim, Calithera, Dracen, Editas, Eli Lilly, EMD Serono, G1 Therapeutics, Genentech, Gilead, GlaxoSmith Kline, Illumina, Merck, Neogenomics, Novartis and Takeda, and personal fees and stock options from Arcus, Belicum, Brooklyn ImmunoTherapeutics, and Gritstone; royalties for patent filed by MSKCC identifying determinants of cancer response to immunotherapy (PCT/US2015/062208 licensed to Personal Genome Diagnostics; PM reports personal fees from Guardant Health. LHS research support from Merck, Bristol-Myers-Squibb, and Boehringer, participating in DSMB for Regeneron, patent with Varian. SCR fees for expert testimony. JC reports consulting fees from Amgen, AstraZeneca, Coherus, Merck, NCCN, Pfizer and travel support from AstraZeneca, GI Therapeutics, participating on DSMB or Ad Board for Beyond Spring, Celegene, G1 Therapeutics, Janssen, Merrimack, Mylan, Roche. JDB is principal investigator of AstraZeneca sponsored trial (PACIFIC 2), research support and consulting fees from Varian. TS institutional grants from Genentech/Roche, Blueprint Medicines, AstraZeneca, Takeda, Advaxis, Regeneron, participation on DSMB or ad board for Takeda, AstraZeneca, Genentech/Roche, Foundation Medicine, Pfizer, EMD Serono, Novartis, Daiichi Sankyo, Lilly, Puma Biotechnology, Janssen Oncology, Regeneron. SR grants from Tesaro, Merck, AstraZeneca, Advaxis, BMS, Amgen, Takeda, Genmab, GSK, consult fees from Amgen, BMS, Genentech/Roche, Merck, AstraZeneca, Takeda, Eisai, Daiichi Sankyo, Sanofi, GSK, Lilly. RSH reports membership in board of directors for Immunocore Holdings Ltd, Junshi Pharmaceuticals, consulting including travel support from AstraZeneca, Genentech/Roche, Merck, Ventana Medical Systems, Inc., consulting with ARMO Biosciences, Bayer Healthcare Pharmaceuticals, Bolt Biotherapeutics, Bristol-Myers Squibb, Candel Therapeutics, Cybrexa Therapeutics, eFFECTOR Therapeutics, Eli Lilly and Company, EMD Serono, Foundation Medicine, Genmab, Gilead, Halozyme Therapeutics, Heat Biologics, I-Mab Biopharma, Immunocore, Infinity Pharmaceuticals, Loxo Oncology, Mirati Therapeutics, Nektar, Neon Therapeutics, NextCure, Novartis, Ocean Biomedical, Oncternal Therapeutics, Pfizer, Ribbon Therapeutics, Sanofi, Seattle Genetics, Shire PLC, Spectrum Pharmaceuticals, STCube Pharmaceuticals, Symphogen, Takeda, Tesaro, Tocagen, Ventana Medical Systems, WindMIL Therapeutics, Xencor. Research support from AstraZeneca, Eli Lilly and Company, Genentech/Roche, Merck. VP research funding from AstraZeneca, BMS, Eli Lilly, Novartis, Merck, F. Hoffman-La Roche, Nektar Therapeutics, Janssen, Bristol-Myers-Squibb, Checkmate, Incyte, consulting fees from AbbVie, Araxes, Arrys Therapeutics, Bolt Therapeutics, Clovis Oncology, Exelixis, G2 Innovation, Gritstone, Ideaya, Leeds Biolabs, Loxo Oncology, Takeda, Tesaro, TRM Oncology, AstraZeneca, BMS, Eli Lilly, Novartis, Merck, F. Hoffman-La Roche, Nektar Therapeutics, Janssen, Bristol-Myers-Squibb, personal fees from F. Hoffman-La Roche, employee of Pfizer. KK travel and consultant fees from AstraZeneca.DRG consultant and participation on advisory boards for AstraZeneca (institutional), Roche-Genentech (institutional), Guardant Health (institutional), IO Biotech (institutional) and Oncocyte (institutional) fees paid to institution, research funding from Amgen, AstraZeneca, Genentech and Merck, personal fees from Inivata, Lilly, Merck and Novartis.The following investigators have no financial disclosures to report: FH, JW, WjI, KM, JM., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)