Gilead Sciences, Inc. and Arcus Biosciences, Inc. announced new data from Cohort B of ARC-9, a Phase 1b/2 study evaluating the safety and efficacy of etrumadenant, a dual A2a/b adenosine receptor antagonist, plus anti-PD-1 monoclonal antibody zimberelimab, FOLFOX chemotherapy and bevacizumab (EZFB) in third-line metastatic colorectal cancer (mCRC). These results will be presented on June 2, 2024 during an oral session at the 2024 American Society of Clinical Oncology (ASCO) Annual Meeting by Zev A. Wainberg, M.D., MSc, Co-Director of the GI Oncology Program at University of California Los Angeles and a principal investigator of the ARC-9 trial (Abstract 3508). Cohort B of ARC-9 randomized 112 patients with comparable baseline characteristics between two arms: EZFB or regorafenib.

At the time of data cut-off (November 13, 2023) median follow-up was 20.4 months. Patient baseline characteristics were similar to those of third-line patients who have progressed on oxaliplatin- and irinotecan-based regimens in mCRC. OS and PFS were consistently longer in the EZFB arm versus regorafenib, in all sub-groups analyzed, including in patients with liver metastases.

The EZFB regimen had a safety profile consistent with the known safety profiles of each individual molecule to date, without unexpected toxicities. A higher percentage of patients treated with regorafenib (17%) had a treatment emergent adverse event (TEAE) leading to discontinuation of all study drugs than those treated with EZFB (5%). A lower percentage of patients experienced Grade =3 TEAEs attributed to etrumadenant or zimberelimab versus regorafenib (23.0% vs 25.7%).

Etrumadenant and zimberelimab are investigational molecules. Neither Gilead nor Arcus has received approval from any regulatory authority for any use of these molecules, and their safety and efficacy for the treatment of colorectal cancer have not been established. About the ARC-9 Study: ARC-9 (NCT04660812) is a Phase 1b/2 trial evaluating the safety and efficacy of etrumadenant (E), a dual A2a/A2b adenosine receptor antagonist, plus anti-PD-1 antibody zimberelimab (Z), FOLFOX and bevacizumab (if not contraindicated) in three cohorts of patients with mCRC.

The primary endpoint is PFS per RECIST 1.1, and OS is a key secondary endpoint. Cohort B enrolled patients who previously progressed on both oxaliplatin- and irinotecan-containing chemotherapy in combination with anti-VEGF (R) therapy or anti-EGFR. Patients were randomized 2:1 to the etrumadenant plus zimberelimab regimen: E (150 mg orally [PO] once daily [QD]) + Z (240 mg intravenous [IV] once every 2 weeks [Q2W]) + mFOLFOX-6 + bevacizumab (5 mg/kg IV Q2W), or regorafenib (administered at a starting dose of 80 mg/day for the first week, followed by a dose escalation of 40 mg every week to 120 mg/day for the second week and 160 mg/day for the third week during Cycle 1 followed by 160 mg/day on Days 1-21 of each subsequent 28-day cycle).

Patients who progressed on regorafenib were allowed to crossover to the etrumadenant plus zimberelimab regimen. ARC-9 is a multi-cohort study in mCRC including Cohort A, which enrolled patients who previously progressed on FOLFOX/FOLFIRI in combination with anti-VEGF(R) or anti-EGFR. Patients were randomized 2:1 to the etrumadenant plus zimberelimab regimen, or FOLFOX-6 + bevacizumab.

Data from Cohort A will be presented when they are mature. About Etrumadenant: Etrumadenant is an investigational small molecule, selective dual antagonist of the A2a and A2b receptors designed to prevent adenosine-mediated immunosuppression. Adenosine elicits its immunosuppressive effects within the tumor microenvironment by binding and activating adenosine-specific receptors expressed on the surface of tumor-infiltrating immune cells, which can help cancer cells evade host antitumor immunity.

Once etrumadenant binds to the A2a and A2b receptors and blocks the immunosuppressive effects of adenosine, activation of antitumor immune cells may be restored, which could result in tumor cell death. Etrumadenant is being evaluated in combination with other cancer immunotherapies, including the investigational Fc-silent anti-TIGIT monoclonal antibody domvanalimab and anti-PD-1 monoclonal antibody zimberelimab, in certain types of non-small cell lung and colorectal cancers. About Zimberelimab: Zimberelimab is an anti-programmed cell death protein-1 (PD-1) monoclonal antibody that binds PD-1, with the goal of restoring the antitumor activity of T cells.

Zimberelimab has demonstrated high affinity, selectivity and potency in various tumor types. Zimberelimab is being evaluated in the U.S. and globally as a foundational anti-PD-1 treatment option in multiple ongoing and planned early and late-stage clinical studies in combination with other immunotherapies, including investigational Fc-silent anti-TIGIT monoclonal antibody domvanalimab and A2a/A2b adenosine receptor antagonist etrumadenant. Guangzhou Gloria Biosciences Co.

Ltd., which holds commercialization rights for zimberelimab in greater China, has obtained approval for zimberelimab for the treatment of recurrent or metastatic cervical cancer and for relapsed or refractory classical Hodgkin's lymphoma. Zimberelimab is not approved for any use in the U.S. or other regions outside of China. Gloria conducts its development and commercialization activities independent of Arcus and Gilead.