First-line durvalumab and tremelimumab with chemotherapy in RAS-mutated metastatic colorectal cancer: a phase 1b/2 trial [RNA-Seq]
While patients with microsatellite instable, metastatic colorectal cancer (CRC) 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 evaluates safety and efficacy of durvalumab plus tremelimumab in combination with mFOLFOX6 chemotherapy in first line, in 57 patients with RAS-mutant unresectable mCRC. Safety was primary objective of phase IB and no safety issue was observed. The primary objective of phase II was efficacy in terms of 3-month PFS in MSS patients, which was met with a 3 month PFS of 90.7% [95% CI: 79.2-96%]. For secondary objective, 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.  Higher tumor mutational burden and a lower degree of genomic instability in responder patients. 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. Overall design: We performed gene expression profiling analysis using RNA-seq data from 34 patients splited into responders and non-responders