Protective Effects of Daratumumab on Carfilzomib-Related Cardiac Dysfunction in Patients with Relapsed Multiple Myeloma: Results from an Observational Study

Introduction: Carfilzomib is a second-generation irreversible proteasome inhibitor that has been shown to improve overall survival in patients with relapsed and/or refractory multiple myeloma (RRMM). Carfilzomib may exert cardiovascular adverse events (CVAEs), although related mechanisms, prognostic markers and precipitating factors have not been fully characterized. In the prospective randomized phase 3 CANDOR study, comparing daratumumab in combination with carfilzomib and dexamethasone (DaraKd) versus Kd alone, a lower rate of cardiac failure events was observed in the DaraKd arm. The aim of this study was to assess whether treatment with daratumumab may ameliorate carfilzomib-related cardiovascular toxicity.

Patients and Methods: This is an ongoing, prospective, observational study on the effects of Kd with or without daratumumab on cardiac function of patients with RRMM. All patients attended an initial visit, which included recording of medical history and cardiotoxicity risk factors (age ≥65 years, obesity, smoking, hypertension, hypercholesterolemia, diabetes mellitus, previous anthracycline use, previous chest or mediastinum radiotherapy and current myocardial disease). At baseline, cardiac ultrasound was performed and images were acquired for standard echocardiographic analysis and for speckle tracking offline analysis. As in ENDEAVOR study, carfilzomib was administered at 20 mg/m² on days 1 (C1D1) and 2 (C1D2) of cycle 1 and at 56 mg/m² thereafter, with dexamethasone 40 mg on days 1, 8 & 15 of 28-day cycles (Kd regimen). In the DaraKd regimen, daratumumab was administered at a weekly dose of 16 mg/kg, iv, for cycles 1–2, every 2 weeks for cycles 3–6 and every 4 weeks thereafter, while Kd was given at the dose described previously. A follow-up cardiac ultrasound study, as described above, was performed on the last day of cycle 6 (C6D16) or earlier if carfilzomib interruption was indicated. Patients were followed for a median of 10 months for carfilzomib-related CVAEs [hypertension (HTN), heart failure (HF) and acute coronary syndrome (ACS)].

Results: In this preliminary report, we evaluated 25 patients with relapsed or refractory MM who received either DaraKd or Kd in the everyday clinical practice; 11 patients received DaraKd and 14 received Kd. Patients’ mean (±SD) age was 67.8±7.6 years and 60% were men. The two treatment groups did not significantly differ in baseline characteristics including age, gender and prevalence of hypertension, hyperlipidemia, smoking, diabetes mellitus and cardiovascular disease (p>0.1 for all). In the DaraKd group, we did not observe any significant change of markers of left and right ventricular systolic function; however, these markers deteriorated in the Kd group. Specifically, in the Kd group, among left ventricular (LV) systolic function markers, average LV ejection fraction (LVEF) decreased from 59.6±4.8 to 56.6±5.4% (p=0.026) and LV global longitudinal strain (GLS) from -22.5±2.9 to -19.4±3.1 (p=0.007). Similarly, among right ventricular (RV) function markers, tricuspid annular plane systolic excursion (TAPSE) decreased from 23.8±3.6 to 20.4±2.8 mm (p=0.020) and RV free wall longitudinal strain from -31.9±3.4 to -28.2±4.3 (p=0.012). A significant group interaction (p<0.05 for all) was observed for changes in all these 4 markers. No difference between groups was observed in changes of markers of LV diastolic or left atrial function. In regard to CVAEs, more events occurred in the Kd group (in 5 out of 11 patients, 45%, including 2 HF and 3 HTN grade 3 events) as compared to the DaraKd group (4 out of 14 patients, 28.6%, including 2 ACS, 1 HF and 2 HTN grade 3 events; one patient had two events, ACS and HTN, both of grade 3).

Conclusion: The combination of daratumumab with Kd is associated with preserved post-treatment cardiac systolic function as compared to the Kd regimen in patients with RRMM, who had received 1-3 prior lines of therapy. This was associated with a lower CVAE rate, even in this small group of patients. The clinical significance and the mechanisms mediating this possible protective cardiovascular action of daratumumab merits further investigation, given the high activity of DaraKd in patients with relapsed or refractory MM.