pMMR/MSS Advanced Colorectal Cancer

The goal of this clinical trial is to evaluate the safety and tolerability of an MSH2-/- tumor cell vaccine and to explore its preliminary antitumor activity and immunogenicity in adults with advanced proficient mismatch repair (pMMR) colorectal cancer who have failed, are intolerant of, or decline standard systemic therapies at West China Hospital, Sichuan University. The main objectives are to determine the incidence of dose-limiting toxicities (DLTs) and other treatment-emergent adverse events (TEAEs) related to the vaccine (n/N, %, graded per NCI CTCAE v5.0), to assess preliminary antitumor activity (objective response per RECIST v1.1, progression-free survival, and overall survival), and to characterize the vaccine's immunogenicity profile. This study using a 3+3 dose-escalation design with three dose levels of the MSH2-/- tumor cell vaccine (1×10\^7, 2.5×10\^7, and 5×10\^7 cells per dose), manufactured under GMP conditions and administered by intradermal injection. Each participant will receive four induction vaccinations (three doses every 2 weeks and a fourth dose 1 month after the third), followed by up to eight booster doses every 4 weeks based on tumor response. Participants will undergo protocol-specified safety monitoring with clinical assessments, laboratory tests, and documentation of all AEs/SAEs, and tumor response will be evaluated regularly by imaging per RECIST v1.1. After treatment completion or discontinuation, participants will enter safety and long-term follow-up for disease status and survival.

Patients with advanced colorectal cancer, particularly those of the pMMR/MSS type, exhibit suboptimal therapeutic responses in the third-line and subsequent treatments. The efficacy of the existing standard treatment regimens is highly restricted. In the CORRECT study, the median overall survival (OS) of regorafenib was 6.4 months, the median progression-free survival (PFS) was 1.9 months, and the objective response rate (ORR) was 1%. In the CONCUR study targeting the Asian population, the median OS of the regorafenib group was 8.8 months, the median PFS was 3.2 months, and the ORR was 4%. In the FRESCO study, the median OS of fruquintinib was 9.3 months, the median PFS was 3.7 months, and the ORR was 4.7%. In the TERRA study, the median OS of trifluridine/tipiracil (TAS-102) was 7.8 months, the median PFS was 2.0 months, and the ORR was 1.1%. The SUNLIGHT study explored the combined treatment modality of TAS-102 plus bevacizumab, where the median OS of the combined regimen was 10.8 months, the median PFS was 5.6 months, and the ORR was 6.1%. Evidently, the therapeutic efficacy of advanced colorectal cancer in the third-line and beyond has plateaued. In recent years, fundamental research has discovered that epigenetic regulation significantly synergizes with anti-angiogenesis and immune checkpoint inhibition therapy. Small-scale clinical explorations have also indicated favorable efficacy and clinical prospects, warranting further investigation. Hence, we contemplate employing the combination of chidamide, regorafenib, and iparomlimab/tuvonralimab to investigate its efficacy and safety in the treatment of advanced colorectal cancer in the third-line and beyond, and to explore novel breakthroughs for refractory colorectal cancer after multiple lines of treatment. The aim of this study is to assess the efficacy and safety of the combination regimen of chidamide, regorafenib, and iparomlimab/tuvonralimab in patients with advanced colorectal cancer in the third-line and beyond. The study will be conducted at Shanghai Changzheng Hospital. The study drugs, including chidamide, regorafenib, and iparomlimab/tuvonralimab, are all commercially available in China.