Phase Ib trial of cabozantinib (C) in combination with atezolizumab (A) in patients (pts) with advanced hepatocellular carcinoma (HCC), gastric or gastroesophageal junction cancer (GC/GEJC), or colorectal cancer (CRC).

Abstract

TPS478 Background: C is an inhibitor of tyrosine kinases involved in tumor growth, angiogenesis, and immune regulation, including MET, VEGFR, and TAM family kinases (Tyro3, AXL, MER). Preclinical and clinical studies suggest that C promotes an immune-permissive tumor environment which may enhance response to checkpoint inhibitors such as the anti-PD-L1 mAb A. C significantly improved overall survival vs placebo in previously treated advanced HCC, and the combination of A and bevacizumab has shown synergistic activity in advanced HCC. Checkpoint inhibitors have shown clinical activity in advanced CRC primarily in pts with high microsatellite instability (MSI); combination with immune-modulating agents may enhance activity in pts with stable or low MSI. Likewise, combination therapy may improve response in pts with GC/GEJC resistant to standard chemotherapy. Here, we present the study design of an ongoing phase 1b trial which includes cohorts with advanced HCC, GC/GEJC, or CRC. Methods: This global, phase 1b, open-label trial will assess the safety, tolerability, preliminary efficacy, and pharmacokinetics of C in combination with A (NCT03170960). The study consists of a dose-escalation stage and an expansion stage. In the dose-escalation stage (3+3 design), a recommended C dose for combination with a standard dose of A will be established. In the expansion stage, 18 cohorts will be enrolled at the recommended dose of C + A including 3 cohorts with gastrointestinal cancers: (1) advanced HCC not previously treated with systemic therapy; (2) advanced GC/GEJC after progression on platinum- or fluoropyrimidine-containing therapy; and (3) advanced CRC after progression on fluoropyrimidine combined with oxaliplatin or irinotecan. Pts will continue treatment as long as they experience clinical benefit as judged by the investigator or until unacceptable toxicity. The primary objective of the expansion stage is the objective response rate for each cohort. Exploratory objectives include correlation of tumor and plasma biomarkers, immune cell profiles, and MSI status with clinical outcome. Clinical trial information: NCT03170960.