Quad-Exposed/Refractory Multiple Myeloma: Patients Previously Treated With Anti-CD38, IMiDs, Proteasome Inhibitors, and BCMA-Targeted Therapies.

Current treatment regimens for multiple myeloma, both in patients eligible and ineligible for autologous stem cell transplantation without adverse biological features (standard risk cytogenetics; absence of extramedullary disease, normal renal function) may achieve progression-free survival lasting from several to over 10 years. However, those patients with adverse biological features, often experience earlier disease progression. Ultimately, these patients require multiple lines of therapy in an attempt to overcome emerging drug resistance. This article focuses on quad-class refractory patients-resistant to proteasome inhibitors, immunomodulatory drugs, anti-CD38 monoclonal antibodies, and BCMA-targeted therapies. Therapeutic options for this patient group are limited, particularly due to anti-BCMA exposure/refractoriness, which represents a major constraint on treatment efficacy.