PD-1 blockade therapy in lymphoid malignancies.

The programmed cell death-1 (PD-1) pathway serves as a checkpoint for suppressing T cell-mediated immune responses. It regulates both the physiological and pathological functions of T cells and is often involved as a mechanism of tumor immune evasion. Many clinical trials have demonstrated that blockade of PD-1 and its ligands is a promising therapeutic strategy for various kinds of malignancies. The most prominent results of PD-1 blockade therapy have been shown in clinical studies of classical Hodgkin lymphoma (cHL), and the PD-1 inhibitor nivolumab was approved for treatment of relapsed/refractory cHL in Japan at the end of 2016. There is increasing evidence that PD-1 blockade therapy is also effective in several other subtypes of lymphoid malignancies. PD-1 inhibitors demonstrate a favorable safety profile, but they can cause immune-related adverse events that affect a variety of organs, such as skin, lung, thyroid, and intestine. Although infrequent, they can develop into life-threatening conditions, and specific monitoring is recommended for the early detection and treatment of these uncommon side effects during PD-1 blockade therapy.