Unlocking the therapeutic potential of selective CDK7 and BRD4 inhibition against multiple myeloma cell growth.

Multiple myeloma (MM) is a plasma cell malignancy that is considered incurable despite the recent therapeutic advances. Effective targeted therapies are, therefore, needed. Our previous studies proved that inhibiting CDK7 impairs the cell cycle and metabolic programs by disrupting E2F1 and MYC transcriptional activities, making it an appealing therapeutic target for MM. Given that CDK7 and BRD4 operate in two distinct regulatory axes in MM, we hypothesized that targeting these two complementary pathways simultaneously would lead to a deeper and more durable response. Indeed, combination therapy had superior activity against MM cell growth and viability, and induced apoptosis to a greater extent than did single-agent therapy in both cell lines and patients' cells. This synergistic activity was also observed in Waldenström macroglobulinemia (WM) cells and with other inhibitors of E2F1 activity. Dual inhibition effectively impaired the MYC and E2F transcriptional programs and MM tumor growth and progression in xenograft animal models, providing evidence for the potential of combination therapy as a therapeutic strategy in MM and WM.