A Study of ASP1951 in Subjects With Advanced Solid Tumors

The primary purpose of this study is to evaluate the tolerability and safety profile of ASP1951 when administered as a single agent and in combination with pembrolizumab in participants with locally advanced (unresectable) or metastatic solid tumors; characterize the pharmacokinetic profile of ASP1951 when administered as a single agent and in combination with pembrolizumab; and determine the recommended phase 2 dose (RP2D) of ASP1951 and/or maximum tolerated dose (MTD) when administered as a single agent and in combination with pembrolizumab. This study will also evaluate the anti-tumor effect of ASP1951 when administered as a single agent and in combination with pembrolizumab.