ASP-1948

The purpose of this study is to evaluate the tolerability and safety profile of ASP1948 when administered as a single agent and in combination with nivolumab or pembrolizumab in participants with locally advanced (unresectable) or metastatic solid tumors; characterize the pharmacokinetic profile of ASP1948 when administered as a single agent and in combination with nivolumab or pembrolizumab and determine the recommended Phase 2 dose (RP2D) of ASP1948 when administered as a single agent and in combination with nivolumab or pembrolizumab. This study will also evaluate the antitumor effect of ASP1948 when administered as a single agent and in combination with nivolumab or pembrolizumab.