Daratumumab; durvalumab; ibrutinib; irradiation; multiple myeloma; nivolumab; PD-1; PD-L1; pembrolizumab; pidilizumab

The introduction of PD-1/PD-L1 pathway inhibitors has marked a significant milestone in the treatment of various types of solid tumors. The current situation in multiple myeloma ( MM) is rather unclear, as distinct research groups have reported discordant results. This discrepancy dominantly concerns the expression of PD-1/PD-L1 molecules as well as the identification of the responsible immune effector cell population. The results of monotherapy with PD-1/PD-L1 inhibitors have been unsatisfactory in MM, suggesting that a combination approach is needed. The most logical partners are immunomodulatory agents as they possess many synergistic effects. We are also proposing other rational and promising combinations (e.g., daratumumab, ibrutinib, anti-CD137) that warrant further investigation.