A Study to Evaluate the Safety and Efficacy of Selinexor With or Without Pembrolizumab Versus Standard of Care in Previously Treated Metastatic Colorectal Cancer With RAS Mutations

The purpose of this study is to evaluate the efficacy and safety of selinexor alone or with pembrolizumab in participants with advanced or metastatic colorectal cancer (CRC). Approximately 78 participants with advanced or metastatic CRC will be enrolled, and randomized (1:1:1) into three arms A (selinexor only), B (selinexor and pembrolizumab), and C (standard of care \[Combination of trifluridine and tipiracil\]). Randomization will be based on stratification factors: Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1 versus 2. The end of treatment (EoT) visit will occur less than or equal to (\<=30) days post-treatment discontinuation. A survival follow-up visit will be performed every 3 months from EoT and will continue for 12 months.