Therapies targeting the programmed cell death protein 1 (PD-1) pathway have improved outcomes for a variety of malignant neoplasms.
1,2 An inhibitory coreceptor primarily expressed at the activated T-cell surface, PD-1 modulates T-cell effector activities, including proliferation,
3 cytokine production,
4 and survival
5 on PD–ligand 1 (PD-L1) or PD-L2–mediated activation. Accordingly, PD-1 and PD-L1 signaling disruption by monoclonal antibodies regenerates T-cell–mediated antitumor immunity, producing durable anticancer effects in a subset of patients.