Antibody DS-8273a Administered in Combination With Nivolumab in Subjects With Advanced Colorectal Cancer

This trial is being performed in two parts: Dose Escalation and Dose Expansion. The primary objective for the Dose Escalation part is to determine the safety and tolerability at different doses of DS-8273a administered in combination with nivolumab and to identify the dose combination for the Dose Expansion cohort in subjects with mismatch repair (MMR)-proficient advanced colorectal cancer. The primary objectives for the Dose Expansion part are: * To further evaluate the safety and tolerability of DS-8273a administered at the selected dose in combination with nivolumab in subjects with MMR-proficient advanced colorectal cancer * To evaluate preliminary anti-tumor activity of DS-8273a plus nivolumab administered at the selected dose in subjects with MMR-proficient advanced colorectal cancer