Updates on Therapeutic Strategies in the Treatment of Relapsed/Refractory Multiple Myeloma

Simple Summary Multiple myeloma is a heterogenous hematological condition with a worldwide incidence of between 0.5-5 per 100,000. The standard front-line treatment algorithm suggests induction chemotherapy, early stem cell transplant in those eligible, followed by maintenance chemotherapy. Unfortunately, most people subsequently relapse and require salvage treatment. A wide array of options are available in the management of relapse/refractory multiple myeloma. Our review aims to describe the new, approved treatment modalities in this setting while describing data on the efficacy, tolerability, and nuances of each available option.Abstract Multiple myeloma is a heterogeneous condition characterized by the proliferation of monoclonal B-cells, for which there is currently no curative treatment available. Relapses are, unfortunately, common after first-line treatment. While the prognosis for relapsed refractory multiple myeloma is generally poor, advances in the treatment of relapsed or refractory multiple myeloma offer hope. However, the expansion of effective options in targeted treatment offers renewed optimism and hope that patients who fail on older therapies may respond to newer modalities, which are often used in combination. We review currently approved and novel investigational agents classified by mechanisms of action, efficacy, approved setting, and adverse events. We delve into future directions of treatment for relapsed/refractory multiple myeloma, reviewing novel agents and therapeutic targets for the future.