Combined PD-1 and CCR5 Inhibition for the Treatment of Refractory Microsatellite Stable mCRC

Inclusion criteria

• . Histologically confirmed metastatic colorectal cancer. Microsatellite stability (MSS) is confirmed by PCR or immunohistochemistry.
• . Patient failed standard therapy or is intolerable towards standard therapy which must include a fluoropyrimidine, oxaliplatin, irinotecan, an antiangiogenic monoclonal antibody (e.g. bevacizumab, aflibercept, ramucirumab), an EGFR inhibitor in case of RAS/BRAF wildtype tumors and optional regorafenib or TAS 102
• . Measurable disease as per RECIST 1.1
• . Metastatic lesion accessible for repetitive biopsies and patient willing to provide tissue from newly obtained biopsies. Patients without accessible lesions might be enrolled after discussion with the principle investigator.
• . ECOG performance status 0 or 1
• . Adequate hematological, hepatic and renal function parameters:
• . Adequate coagulation functions as defined by International Normalized Ratio (INR) ≤1.5, and a partial thromboplastin time (PTT) ≤ 5 seconds above the ULN (unless receiving anticoagulation therapy). Patients receiving warfarin/ phenprocoumon must be switched to low molecular weight heparin and have achieved stable coagulation profile.
• . Female and male patients' ≥ 18 years. Patients in reproductive age must be willing to use adequate contraception during the study and 4 months after the end of the study (appropriate contraception is defined as surgical sterilization (e.g., bilateral tubal ligation, vasectomy), hormonal contraception (implantable, patch, oral), and doublebarrier methods (any double combination of: IUD, male or female condom with spermicidal gel, diaphragm, sponge, cervical cap)). Abstinence (relative to heterosexual activity) can be used as the sole method of contraception if it is consistently employed as the subject's preferred and usual lifestyle and if considered acceptable by local regulatory agencies and ERCs/IRBs. Periodic abstinence (e.g., calendar, ovulation, sympto-thermal, post-ovulation methods, etc.) and withdrawal are not acceptable methods of contraception. Female patients with childbearing potential need to have a negative pregnancy test within 7 days before study start.