A phase 1b/2 study of ARRY-382, an oral inhibitor of colony stimulating factor 1 receptor (CSF1R), in combination with pembrolizumab (Pembro) for the treatment of patients (Pts) with advanced solid tumors.

Abstract

TPS3110 Background: CSF1, which signals via CSF1R, regulates tumor-associated macrophages and myeloid-derived suppressor cells, both critical drivers of immune escape in the tumor microenvironment. ARRY-382 is a highly selective, oral inhibitor of the CSF1R intracellular tyrosine kinase. The first-in-human study of ARRY-382 monotherapy identified the maximum tolerated dose (MTD) of 400 mg QD, with biologic activity at doses ≥200 mg QD (Bendell JC et al. Mol Cancer Ther. 2013;12:A252). Preclinical data supports combining a PD-1 inhibitor with a CSF1R inhibitor (Zhu Y et al. Cancer Res. 2014;74:5057-69). This study is designed to evaluate ARRY-382 in combination with pembro, a potent and highly selective humanized monoclonal antibody that targets PD-1. Methods: This is an open-label, multicenter, phase 1b/2 study (NCT02880371) to determine the MTD and/or recommended phase 2 dose (RP2D) of ARRY-382 + pembro and to evaluate the activity of the combination in select indications. In phase 1b (Part A), the primary objective is to identify the MTD/RP2D. Up to 18 pts with select advanced solid tumors (Part A) will be enrolled in 2 successive cohorts evaluating ARRY-382 at doses of 200 mg QD and 400 mg QD, respectively, in combination with pembro 2 mg/kg Q3W. Once the MTD/RP2D has been determined in phase 1b, phase 2 will concurrently evaluate the combination in up to 20 pts with advanced unresectable/metastatic melanoma (Part B) and in up to 33 pts with PD-L1-positive (tumor proportion score ≥50) non-small cell lung cancer (NSCLC) (Part C). The primary objective of Part B is to assess the pharmacodynamics and antitumor activity of ARRY-382 + pembro in pts with advanced unresectable/metastatic melanoma, and the endpoints include effects of treatment on circulating growth factors and cytokines, markers of bone resorption, and objective response rate (ORR). The primary objective of Part C is to assess the efficacy of ARRY-382 + pembro in pts with PD-L1–positive NSCLC (Part C). The primary endpoint is ORR. Immune-related response rate and safety will be evaluated in all pts in the study. Clinical trial information: NCT02880371.