The advent of therapeutic monoclonal antibodies (elotuzumab, daratumumab) for multiple myeloma (MM) heralded a new era of immunologic therapy for this disease. Laboratory and clinical data suggest that immune checkpoint inhibitors (ICI) targeting the PD-1/PD-L1 axis are a promising novel strategy, as PD-L1 is commonly expressed on MM cells and a phase 2 clinical trial demonstrated encouraging responses to pembrolizumab (anti-PD-1) in combination with pomalidomide and dexamethasone. However, two late stage MM clinical trials of ICI combined with either lenalidomide or pomalidomide were halted due to safety concerns and lack of efficacy, although subgroup analysis suggested that the overall response rate in subjects with immune related adverse events was higher in subjects who received pembrolizumab + pomalidomide and dexamethasone vs the control group. As a result, further investigation of ICI in MM has largely discontinued. This discrepancy with the positive findings in the early phase trial suggests that genetic or immunologic features of the tumors or immune microenvironment of the patients may influence outcome to ICI, but these factors are as yet undefined. In solid tumors, high mutation burden as assessed by microsatellite sequence instability-high (MSI-high) or mismatch repair genes deficiency (dMMR) was correlated to response to anti-PD-1 ICI, and is now an indication for these agents. Newly diagnosed MM is considered an intermediate-low mutation burden disease ( Disclosures Cho: The Multiple Myeloma Research Foundation: Employment; Celgene: Honoraria, Research Funding; Takeda: Research Funding; Agenus: Research Funding; Genentech: Honoraria, Research Funding; BMS: Consultancy; GSK: Consultancy. Jackson:Bristol-Myers Squibb: Employment, Equity Ownership. Robbins:Bristol-Myers Squibb: Employment, Equity Ownership. Parekh:Karyopharm Inc.: Research Funding; Foundation Medicine Inc.: Consultancy; Celgene Corporation: Research Funding.