Multiple myeloma and the potential of new checkpoint inhibitors for immunotherapy

Multiple myeloma (MM), a cancer of the bone marrow, is categorized as the second most common hematological malignancy of adults in the Western world. Despite dramatic improvements in immunotherapies in the field of cancers, MM immunotherapy has not been promising until now. Recent clinical studies of immune checkpoint inhibitor therapy, either alone or in combination with anticancer drugs, showed excessive side effects or low efficacy, particularly in advanced MM patients. In this context, lymphocyte levels of exhaustion markers play a pivotal role in the MM tumor microenvironment (TME). Hence in the present review, the mechanisms relevant to MM of five inhibitory molecules including T-cell immunoreceptor with Ig and ITIM domains (TIGIT), T-cell immunoglobulin, and mucin domain 3 (Tim-3), lymphocyte activation gene-3 (LAG-3), V-domain Ig Suppressor of T-cell activation and killer immunoglobulin-like receptors along with bispecific T-cell antibodies (BsAbs) will be discussed. Further, we summarized the underlying biology of these checkpoints in cancer and their rapidly emerging role in pathways in MM along with presenting recent clinical trials in context.