Abstract CT217: First-line durvalumab and tremelimumab with chemotherapy in RAS-mutated metastatic colorectal cancer: a phase 1b-2 trial

Abstract Metastatic colorectal cancer (mCRC) remains a difficult-to-treat disease. While patients with microsatellite instable metastatic colorectal cancer (mCRC) benefit from immune checkpoint blockade, chemotherapy with targeted therapies remains the only therapeutic option for microsatellite stable (MSS) tumors. The single arm, phase IB/II MEDITREME trial evaluated the safety and efficacy of durvalumab plus tremelimumab combined with mFOLFOX6 chemotherapy in first line, in 57 patients with RAS-mutant unresectable mCRC. Safety was the primary objective of phase IB; no safety issue was observed. The phase II primary objective of efficacy in terms of 3-month PFS in MSS patients was met, with 3-month PFS of 90. 7% 95% CI: 79. 2-96%. For secondary objectives, response rate was 64. 5%, median PFS was 8. 2 months 95% CI: 5. 9-8. 6 and overall survival was not reached in MSS patients. We observed higher tumor mutational burden and lower genomic instability in responders. Integrated transcriptomic analysis underlined that high immune signature, and low epithelio-mesenchymal transition were associated with better outcome. Immunomonitoring showed induction of neoantigen and NY-ESO1 and TERT blood tumor specific T cell response, associated with better PFS. The combination of durvalumab-tremelimumab with mFOLFOX6 was tolerable with promising clinical activity in MSS mCRC. Clinicaltrials. gov identifier: NCT03202758. Citation Format: Marion Thibaudin, Jean-David Fumet, Emeric Limagne, Léa Hampe, Susy Daumoine, Valentin Derangère, Caroline Laheurte, Olivier Adotevi, Caroline Truntzer, François Ghiringhelli. First-line durvalumab and tremelimumab with chemotherapy in RAS-mutated metastatic colorectal cancer: a phase 1b-2 trial abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (7Suppl): Abstract nr CT217.