- have not received previous systemic therapy (including investigational agents) targeting programmed cell death protein 1 (PD-1)/ PD-1 ligand (PDL 1) or PD-1/PDL-2 signaling pathways. Prior therapy with other immune checkpoint inhibitors, including but not limited to, anti-CD137 antibody or anticytotoxic T-lymphocyte-associated antigen-4 antibody, is not permitted