 6. Prior therapy with experimental antitumor vaccines; any T-cell co-stimulation agents or inhibitors of checkpoint pathways, such as anti- programmed cell death protein 1 PD-1, anti- programmed cell death 1 ligand 1 PD-L1, anti- programmed cell death 1 ligand 2 PD-L2, anti-CD137, or anti-CTLA-4 antibody; or other agents specifically targeting T cells are prohibited. However, for dose escalation, prior treatment with the marketed inhibitors of the immune checkpoint pathway, such as nivolumab and pembrolizumab, is allowed. In addition, in each of the expansion cohorts, 6 response-evaluable participants with prior exposure to anti-PD-1 or anti-PD-L1 agents will be allowed to enroll. 