Regorafenib Plus Raltitrexed as Third-line Treatment in Advanced Colorectal Cancer Patients：An Open-label, Single-arm, Multicenter Phase I/II Study

This is a multicenter, open, single-arm, phase I/II study to evaluate the efficacy and safety of regorafenib plus raltitrexed as third-line treatment in patients with advanced colorectal cancer.This Phase Ib/II study consists of two parts, Phase Ib, an open-ended, single-arm, multi-centre, dose-escalation study evaluating regorafenib, and Phase II, an open-label, multi-centre study evaluating the efficacy and safety of regorafenib in combination with raltitrexed.The primary study endpoint: progression-free survival (PFS).The secondary end endpoints include ORR (overall effectiveness of tumour treatment)，DCR (disease control rate)，3 month/6 month/9 month/12 month survival OS%，OS (overall survival)，incidence and severity of adverse events (AEs), serious adverse events (SAEs).