Blocking the recruitment of MDSCs to the tumor microenvironment has been attempted using chemokine inhibitors that target pathways such as CCR5 (Maraviroc) and CXCR2 (Reparixin) in phase 1/2 clinical trials for metastatic colorectal cancer (NCT 01736813) and breast cancer (NCT 02370238). The gene discussed is CCR5; the disease is metastatic colorectal cancer.