There will be 2 cohorts with enrollment in 2 parts. Participants will be treated on Day 1 of each 21-day cycle (every 3 weeks) with U3-1402 5.6 mg/kg intravenous (IV). The estimated treatment period is approximately 8 months and the follow-up period is approximately 4 months.
This study is designed to primarily evaluate the safety and efficacy of U3-1402 in participants with advanced or metastatic colorectal cancer (CRC) who have received at least 2 prior lines of therapy and will explore clinical benefit according to human epidermal growth factor receptor 3 (HER3) tumor expression level in otherwise refractory tumors.