MK-4166 + pembrolizumab

MK-4166 + pembrolizumab is a **combination therapy** under investigation for the treatment of advanced solid tumors, particularly advanced melanoma. MK-4166 is a humanized IgG1 monoclonal antibody agonist targeting the *glucocorticoid-induced TNF receptor* (GITR), designed to stimulate effector T cells and reduce regulatory T cell–mediated immunosuppression. Pembrolizumab is a well-established anti-PD-1 monoclonal antibody checkpoint inhibitor, approved for multiple cancers, that prevents immune suppression in tumors by blocking the interaction between PD-1 and its ligands. The combination aims to enhance antitumor immune responses through both stimulation of T cell activation (via GITR agonism) and inhibition of immune checkpoint signaling (via PD-1 blockade). Initial phase 1 studies showed a high response rate, particularly in immune checkpoint inhibitor–naïve melanoma patients, and manageable safety profile[1][2][5].