Carfilzomib Induces Acute Endothelial Dysfunction Which Correlates with the Occurrence of Cardiovascular Events

Carfilzomib (CFZ) is a proteasome inhibitor associated with cardiovascular (CV) adverse events (AEs) mainly hypertension (HTN) and cardiac dysfunction. Endothelial dysfunction is a major mediating mechanism in cardiovascular diseases and endothelial function may be adversely affected by proteasome inhibition. However, CFZ effects on endothelial and vascular function and associations with inhibition of proteasome activity have not been explored in humans. We prospectively evaluated CFZ effects on endothelial function and underlying mechanisms as well as baseline vascular function and its response to treatment as potential predictors of CFZ-associated CV toxicity.

In this prospective study (NCT03543579), 48 relapsed/refractory myeloma patients (median 1 (1-3) lines of therapy, median age: 67.5, 67% men) received Kd [CFZ 20/56 mg/m² and dexamethasone] in routine practice. A detailed medical history and evaluation of risk factors for cardiotoxicity [age≥65 years, obesity, smoking, HTN, hypercholesterolemia, diabetes mellitus, previous anthracyclin use, chest or mediastinum radiotherapy and current myocardial disease] were recorded. Before CFZ start and at prespecified timepoints cardiac echo, hemodynamic parameters and vascular function that reflect pivotal mechanisms involved in development of HTN and CV events were non-invasively assessed [aortic blood pressure and arterial wave reflections, aortic stiffness and endothelial function using flow-mediated dilatation of the brachial artery (FMD)] along with 24h ambulatory blood pressure monitoring. Proteasome activity (PrA) was measured in peripheral blood mononuclear cells (PBMC) before and 2 hours post CFZ infusion on days 1 (FMD_baseD1 and FMD_postCFZD1) and 2 (FMD_baseD2 and FMD_postCFZD2) of cycle 1 and at prespecified time points concurrently with vascular function assessment. CV AEs were recorded and rated according to CTCAE v4.03.

The prevalence of risk factors for cardiotoxicity was high (median 3 factors, IQR 2-4). After first CFZ dose, FMD decreased acutely at 2 hours (FMD_baseD1: 5.2%, IQR: 3.2-7.4 vs FMD_postCFZD1: 3.6%, IQR: 1.5-4.7, p=0.008), which partially recovered before and after second CFZ infusion (FMD_baseD2: 4.1% and FMD_postCFZD2: 4%, as compared to FMD_baseD1) (Figure1A). However, FMD decrease was more pronounced among patients who subsequently had lower recovery rate of PBMC PrA 24 hours after first CFZ administration (FMD_baseD1: 5.1%, vs FMD_postCFZD1: 3%, p=0.002) while FMD was not decreased significantly in those who had higher recovery rates of PrA (FMD_baseD1: 5.3%, vs FMD_{post CFZD1}: 4.5%, p=0.197, Figure 1B), suggesting that the ability to recover PrA is implicated in CFZ induced endothelial dysfunction.

At the time of analysis, enrolment has completed; 35 patients are still receiving therapy, 13 have discontinued Kd and median follow up is 4.73 months. CV AEs were recorded in 17 (35.4%) patients [HTN(Gr3): 20.8%, Gr3 Left Ventricular dysfunction : 8.3%, Gr3 acute coronary syndrome: 4.2%, Gr3 pulmonary embolism: 2.1%] and generally occurred early (median time to CV event 2.9 months). Kd was discontinued in 2 patients (4.2%) due to cardiotoxicity and in 2 patients (4.2%) CFZ dose was reduced due to cardiotoxicity; no CFZ dose reduction or discontinuation was needed for HTN.

Among clinical and hemodynamic parameters assessed at baseline, patients with higher aortic SBP (i.e at higher quartile) had a higher risk of HTN even after adjustment for age, gender and baseline HTN (HR=8, 95%CI 2.4-26, p=0.001 and HR=4.9, 95%CI 1.5-15, p=0.007 respectively). Lower PrA recovery rate was associated with increased risk of developing Gr3 HTN (log-rank test p=0.01). Higher post-CFZ reduction of FMD was associated with HTN in patients not receiving statins but not in those receiving statins (a drug class strongly affecting FMD), indicating that statin treatment may exert protective effects against CFZ-related CV toxicity.

In conclusion, CFZ causes acute endothelial dysfunction; however, higher recovery of proteasome activity is associated with ameliorated depression of endothelial function. Given that poor proteasome recovery rate and acute deterioration of endothelial function are both associated with development of HTN, these findings may improve our understanding of CFZ-related CV toxicity and its prevention. The study is ongoing and more data will be presented at the meeting.