Comparison of Proteasome Inhibitors-Induced Cardiotoxicity (carfilzomib vs. bortezomib): Insights into the Molecular Mechanisms

Abstract Introduction: Proteasome inhibitors are widely used for the treatment of multiple myeloma (MM). Carfilzomib is an irreversible proteasome inhibitor, which has been licensed for the treatment of relapsed/refractory MM. In phase 3 trials, carfilzomib has been associated with higher heart failure and cardiotoxicity rates (grade ≥3: 4-6%) compared with the reversible inhibitor, bortezomib (grade ≥3: Methods: Male C57BL/6 mice, 12 weeks old, were randomized into the following groups: 1. Control group (Ν/S 0.9%, n=7); 2. Bortezomib group (1mg/kg ip, n=9); 3. Carfilzomib group (8 mg/kg ip, n=8). Drugs were administered every 48 hours for 6 days. At baseline and at the end of treatment the mice underwent echocardiographic assessment. Animals were sacrificed and blood and myocardial tissue samples were obtained for the analysis of proteasome peptidases activity, signaling pathways and molecular mechanisms. Protein kinase Akt, along with its downstream NO synthases; endothelial (eNOS) and inducible (iNOS), were identified as targets of possible endothelial dysfunction and inflammation. Moreover, the transcription factor FOXO1, downstream target of Akt and AMPKα, was identified in order to investigate possible changes in the expression of apoptotic factors. Finally, AMPKα was identified since - besides phosphorylating eNOS and FOXO1 - it functions as a regulator of autophagy. Blood samples were used to measure levels of malondialdehyde (MDA), a marker for oxidative stress (lipid peroxidation). Results: Administration of bortezomib or carfilzomib resulted in significant reduction of the assayed chymotrypsin-like (CT-L) and caspase-like (C-L) proteasomal peptidase activities in the hearts of treated mice vs . controls. Echocardiography at day 6 demonstrated a statistically significant reduction in the fractional shortening (FS) in the carfilzomib group compared to the bortezomib and control groups (39.87±0.47% vs. 42.10±0.82% and 42.05±0.64 respectively, p Conclusion: The present study demonstrates that carfilzomib induces cardiac dysfunction via interfering with the Akt/eNOS axis and via simultaneous increase of iNOS, leading to possible endothelial dysfunction and inflammation. Importantly the decrease of phosphorylation of AMPKα observed in the carfilzomib group seems to be an essential mechanism for carfilzomib induced FS reduction. Moreover, AMPKα and Akt inhibition results in decreased FOXO1 phosphorylation with possible induction of apoptosis and autophagy. On the contrary bortezomib seems to cause premature death in the mice through a different mechanism that requires further investigation. Disclosures Kastritis: Takeda: Honoraria; Amgen: Research Funding; Genesis: Honoraria; Janssen: Honoraria, Research Funding. Dimopoulos: Genesis Pharma: Research Funding; Amgen Inc, Celgene Corporation, Janssen Biotech Inc, Onyx Pharmaceuticals, an Amgen subsidiary, Takeda Oncology: Consultancy, Honoraria, Other: Advisory Committee: Amgen Inc, Celgene Corporation, Janssen Biotech Inc, Onyx Pharmaceuticals, an Amgen subsidiary, Takeda Oncology; Novartis: Consultancy, Honoraria. Terpos: Janssen: Honoraria, Research Funding; Takeda: Honoraria, Other: SC member; GSK: Honoraria; Genesis/Celgene: Honoraria, Other: DMC member, Research Funding; Amgen: Honoraria, Other: SC member, Research Funding; BMS: Honoraria; Abbvie: Honoraria.