While two phase I trials for malignant melanoma and advanced cancer malignancies using the SHP-1 inhibitor sodium stibogluconate (SSG) have failed due to the lack of efficacy on tumor burden while inducing strong toxic side-effects (100), retroviral SHP-1 knockdown together with immune checkpoint blockade has been effective in recruiting low affinity T cells for antitumor function (101). This evidence concerns the gene PTPN6 and melanoma.