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

Eligible subjects will receive pembrolizumab beginning on Day 1 of each 3-week dosing cycle (d1, qd22) together with maraviroc administered perorally on day 1 to 21 of each cycle (d1-21; qd22). Treatment with pembrolizumab / maraviroc combination will continue until progressive disease (PD), unacceptable adverse events (AEs), intercurrent illness that prevents further administration of treatment, investigator's decision to withdraw the subject, subject withdraws consent, pregnancy of the subject, noncompliance with trial treatment or procedure requirements, administrative reasons requiring cessation of treatment, or completion of treatment per protocol. Subjects with a treatment response or stable disease after completion of the first treatment phase of eight cycles (core treatment period) will be offered, at the discretion of the investigator, participation in a maintenance phase consisting of up to 24 additional treatment cycles of pembrolizumab monotherapy (total treatment duration up to 24 months). Subjects who discontinue for reasons other than PD will have post-treatment follow-up for disease status until PD, initiating a non-study cancer treatment, withdrawing consent, or becoming lost to follow-up. All subjects will be followed for overall survival (OS) until death, withdrawal of consent, loss to follow-up, or the end of the study. After the end of treatment, each subject will be followed for 30 days for AE monitoring. Serious adverse events (SAEs) and AEs of special interest (AESIs) will be collected for 90 days after the end of treatment or for 30 days after the end of treatment if the subject initiates new anticancer therapy, whichever is earlier.