Side-effects of checkpoint inhibitor-based combination therapy.

PURPOSE OF REVIEW: After the dramatic and often long-standing response rates of checkpoint inhibitors as single agents, the new era for checkpoint inhibitors is combined therapy (either with other checkpoint inhibitors, chemotherapies, targeted therapies or immunotherapies) that is aiming to do even better. Although one can speculate that these combinations will result in improved results, high cost and potential toxicity are limiting factors for their use. In this review, we plan to report on the different side-effects of the checkpoint inhibitor-based combination therapies and to discuss the future perspectives of these new modalities.

RECENT FINDINGS: Many checkpoint inhibitor-based combinations are associated with high response rates (>50%) in melanomas and nonsmall cell lung cancers (NSCLCs). As a result, the combination of nivolumab and ipilimumab for metastatic melanoma was recently approved by the Food and Drug Administration; however, 30% of the patients had to discontinue this combination because of high toxicity. In NSCLC, the combination of chemotherapy and anti-programmed cell death protein 1 or anti-programmed cell death protein ligand 1 agents is leading to high response rate (exceeding 65%) but with more than 40% of the patients presenting grade 3/4 toxicities. Despite the discouraging results with the combination of ipilimumab (anti-cytotoxic T-lymphocyte-associated protein 4) with vemurafenib (anti-proto-oncogene protein B-raf-targeted therapy) due to hepatotoxicity, more recent trials are showing less frequent and severe toxicities with other combinations of checkpoint inhibitors and targeted therapies.

SUMMARY: Despite the high toxicity rates observed with some checkpoint inhibitor-based combination therapies, these combinations will likely become the new paradigm for the management of various malignancies, namely, melanomas, renal cell carcinomas and NSCLC, provided that their side-effects can be effectively managed.