CK1δ and CK1ε Signaling Sustains Mitochondrial Metabolism and Cell Survival in Multiple Myeloma.

Multiple myeloma remains an incurable malignancy due to acquisition of intrinsic programs that drive therapy resistance. Here we report that casein kinase-1δ (CK1δ) and CK1ε are therapeutic targets in multiple myeloma that are necessary to sustain mitochondrial metabolism. Specifically, the dual CK1δ/CK1ε inhibitor SR-3029 had potent in vivo and ex vivo anti-multiple myeloma activity, including against primary multiple myeloma patient specimens. RNA sequencing (RNA-seq) and metabolic analyses revealed inhibiting CK1δ/CK1ε disables multiple myeloma metabolism by suppressing genes involved in oxidative phosphorylation (OxPhos), reducing citric acid cycle intermediates, and suppressing complexes I and IV of the electron transport chain. Finally, sensitivity of multiple myeloma patient specimens to SR-3029 correlated with elevated expression of mitochondrial genes, and RNA-seq from 687 multiple myeloma patient samples revealed that increased CSNK1D, CSNK1E, and OxPhos genes correlate with disease progression and inferior outcomes. Thus, increases in mitochondrial metabolism are a hallmark of multiple myeloma progression that can be disabled by targeting CK1δ/CK1ε. SIGNIFICANCE: CK1δ and CK1ε are attractive therapeutic targets in multiple myeloma whose expression increases with disease progression and connote poor outcomes, and that are necessary to sustain expression of genes directing OxPhos.

Cardiac events after standard of care idecabtagene vicleucel for relapsed and refractory multiple myeloma.

Idecabtagene vicleucel (ide-cel) is a type of B-cell maturation antigen (BCMA)-targeting chimeric antigen receptor T-cell (CAR-T) approved for the treatment of relapsed and refractory multiple myeloma (RRMM). Currently, the incidence of cardiac events associated with ide-cel remains unclear. This was a retrospective single-center observational study of patients treated with ide-cel for RRMM. We included all consecutive patients who received standard-of-care ide-cel treatment at least 1-month follow-up. Baseline clinical risk factors, safety profile, and responses were examined based on the development of a cardiac event. A total of 78 patients were treated with ide-cel, and 11 patients (14.1%) developed cardiac events: heart failure (5.1%), atrial fibrillation (10.3%), nonsustained ventricular tachycardia (3.8%), and cardiovascular death (1.3%). Only 11 of the 78 patients had repeat echocardiogram. Baseline risk factors associated with the development of cardiac events included being female sex and having poor performance status, λ light-chain disease, and advanced Revised International Staging System stage. Baseline cardiac characteristics were not associated with cardiac events. During index hospitalization after CAR-T, higher-grade (≥grade 2) cytokine release syndrome (CRS) and immune cell-associated neurologic syndrome were associated with cardiac events. In multivariable analyses, the hazard ratio for the association of the presence of cardiac events with overall survival (OS) was 2.66 and progression-free survival (PFS) was 1.98. Ide-cel CAR-T for RRMM was associated with similar cardiac events as other types of CAR-T. Worse baseline performance status and higher-grade CRS and neurotoxicity were associated with cardiac events after BCMA-directed CAR-T-cell therapy. Our results suggest that the presence of cardiac events may confer worse PFS or OS; although because of the small sample size, the power to detect an association was limited.