Encorafenib, Cetuximab, and Nivolumab in Treating Patients With Microsatellite Stable, BRAFV600E Mutated Unresectable or Metastatic Colorectal Cancer

PRIMARY OBJECTIVES: I. To describe overall response rate (ORR) upon treatment with encorafenib, cetuximab, and nivolumab. II. To determine the safety and tolerability of nivolumab, encorafenib, and cetuximab. SECONDARY OBJECTIVES: I. To estimate median progression-free survival (PFS) upon treatment with encorafenib, cetuximab, and nivolumab. II. To estimate median overall survival (OS) upon treatment with encorafenib, cetuximab, and nivolumab. III. To estimate median time to response (TTR) upon treatment with encorafenib, cetuximab, and nivolumab. IV. To estimate median duration of response (DOR) upon treatment with encorafenib, cetuximab, and nivolumab. V. To estimate disease control rate (DCR) upon treatment with encorafenib, cetuximab, and nivolumab. EXPLORATORY OBJECTIVES: I. To assess genomic and immune changes upon treatment with encorafenib, cetuximab, and nivolumab. II. To demonstrate feasibility of establishing humanized patient-derived xenograft models in matched patients with BRAFV600E metastatic colorectal cancer (mCRC). OUTLINE: This is a phase I, dose-escalation study followed by a phase II study. Patients receive encorafenib orally (PO) once daily (QD) on days 1-28, cetuximab intravenously (IV) over 1 hour on days 1 and 15, and nivolumab IV over 30 minutes on day 1. Cycles repeat every 28 days in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up at 30 and 100 days, at 3 months, and then every 3 months thereafter.