Therapeutics that target the T cell inhibitory checkpoint proteins CTLA-4 and PD(L)1 are efficacious across a broad range of cancers, resulting in reductions in tumor burden and increased long-term survival in subsets of patients. The significant and wide-ranging effects of these immunotherapies have prompted the clinical investigation of additional therapies that modulate anti-tumor immunity through effects on T cells, myeloid cells, and other cell types within the tumor microenvironment. The clinical activity of these newer investigational therapies has been mixed, with some therapeutics showing promise but others not exhibiting appreciable efficacy. In this review, we summarize the results of select recent clinical studies of cancer immunotherapies beyond anti-CTLA-4 and anti-PD(L)1 and discuss how these results are providing new insights into the regulation of human anti-tumor immunity.
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