ARC-9: A randomized study to evaluate etrumadenant based treatment combinations in previously treated metastatic colorectal cancer (mCRC).

3508 Background: Adenosine mediated signaling via A 2a and A 2b receptors impairs activation, proliferation, and cytotoxic activity of effector T cells resulting in inhibition of antitumor activity. Adenosine receptor blockade may therefore enhance therapeutic efficacy of chemo/immunotherapy regimens. Etrumadenant (E) is an orally bioavailable, selective, A 2a and A 2b receptor antagonist that has demonstrated safety and clinical activity in solid tumors when combined with chemo/immunotherapy. ARC-9 (NCT04660812), a Phase Ib/II trial evaluating the safety and efficacy of E combined with zimberelimab (Z) (anti-PD-1 antibody), and FOLFOX/bevacizumab (bev) regimens or novel therapies in 3 cohorts of patients (pts) with mCRC. While FOLFOX rechallenge is frequently used in the management of mCRC, no prospective trials have been performed to date. Methods: Cohort B enrolled pts who previously progressed on both oxaliplatin and irinotecan containing regimens.Pts were randomized 2:1 to EZFB: E (150 mg orally PO once daily QD) + Z (240 mg intravenous IV once every 2 weeks Q2W) + mFOLFOX-6 + bev (5 mg/kg IV Q2W), or regorafenib (rego) (160 mg PO QD days 1-21 every 4 weeks). Pts who progressed on rego were allowed to crossover to EZFB. The primary endpoint is progression-free survival (PFS) per RECIST 1.1 and overall survival (OS) is a key secondary endpoint. Results: In Cohort B, 112 pts were randomized. Baseline characteristics are comparable between arms. As of 13 Nov 2023, with median follow-up of 20.4 months (mo), EZFB demonstrated statistically significant improvement in PFS (HR 0.27, 95% CI 0.17-0.43, p < 0.0001) and OS (HR 0.37, 95% CI 0.22-0.63, p = 0.0003) vs rego (Table). EZFB had an acceptable safety profile, consistent with the known FOLFOX/bev toxicity profile with no deaths related to study treatment in either arm. Conclusions: In this randomized phase II clinical trial, EZFBsignificantlyimproved efficacy outcomes compared to rego in refractory mCRC pts previously treated with 5-FU, oxaliplatin and irinotecan regimens with no unexpected toxicities. Further investigation of this promising regimen is warranted given the clinically meaningful PFS and OS improvement. Table Clinical trial information: NCT04660812 . Table: see text