A Multicenter, Phase Ib/II Clinical Trial to Evaluate the Efficacy and Safety of Concurrent Combination Therapy of S-531011 Plus Fruquintinib or S-531011 Plus Fruquintinib Plus Pembrolizumab in Patients With MSS/pMMR Colorectal Cancer

This study aims to evaluate the efficacy and safety of the concurrent combination therapy of S-531011 plus fruquintinib, or S-531011 plus fruquintinib plus pembrolizumab, in patients with MSS/pMMR colorectal cancer. Eligible participants include patients with metastatic colon or rectal cancer who are 18 years of age or older, have an ECOG Performance Status of 0-1, and have MSS or pMMR tumor status. After written explanation and the provision of written informed consent, participants will be enrolled.

The study consists of a Phase Ib part and a Phase II part. In the Phase Ib part (N = 6-12/Arm), participants will be assigned to Arm A or Arm B. Enrollment into Arm B will begin only after enrollment into Arm A has been completed in both phases.

Arm A consists of S-531011 (intravenous, once every 3 weeks) plus fruquintinib (5 mg orally once daily on Days 1-21 of a 28-day cycle).

Arm B consists of S-531011 (intravenous, once every 3 weeks), fruquintinib (5 mg orally once daily on Days 1-21 of a 28-day cycle), and pembrolizumab (200 mg, intravenous, once every 3 weeks).

In the Phase II part (N = 22/Arm), the recommended dose determined in the Phase Ib part will be used.