A Multicenter, Open Label Phase I/II Study of Carfilzomib, Pomalidomide and Dexamethasone in Relapsed and/or Refractory Multiple Myeloma (MM) Patients

Background: Survival rates of multiple myeloma (MM) patients (pts) has improved over the past few years, but patients inevitably relapse and become more resistant to subsequent treatments. Carfilzomib and Pomalidomide were both approved for the treatment of relapsed/refractory MM (RRMM). Combinations including a proteasome inhibitor (PI) plus an immunomodulator (IMiD), such as Bortezomib-Lenalidomide-Dexamethasone (VRD) or Carfilzomib-Lenalidomide-Dexamethasone (CRD), showed a very high response rate with an acceptable toxicity. Moreover, in the CHAMPION1 study (Berenson et al Blood 2016), the weekly infusion of Carfilzomib showed to be as effective as the twice schedule. In this phase I/II study we assessed for the first time weekly Carfilzomib plus Pomalidomide and low dose Dexamethasone (wKPd) for the treatment of RRMM. Here we report preliminary results.

Methods: the primary objective of the phase I part of the trial was to determine the maximum tolerated dose (MTD) of wKPd combination. The primary objective of the phase II was to determine the rate of partial response (PR). Patients with RRMM, who received 1-3 prior lines of treatments and were refractory to Lenalidomide were eligible. Treatment consisted of 28-day cycles of oral Pomalidomide at fixed dose of 4 mg on days 1-21 (1 week off), oral or intravenous (iv) Dexamethasone 40 mg on days 1,8,15,22 and iv Carfilzomib at escalating doses on days 1,8,15. Escalation started at the dose of 36 mg/m2 (0 level) and used a standard 3+3 schema based on dose-limiting toxicities (DLTs) occurring in cycle 1. Treatment was continued until relapse or intolerance.

Results: A total of 57 patients were enrolled in 6 Italian centers. Fifty-two patients could be evaluated for this analysis (5 patients did not complete the first cycle yet). The median age was 62 years with a median time from diagnosis of 4 years. 17/39 (44%) of patients were considered high risk according to cytogenetic abnormalities [at least one among t (4;14) t (14;16) and deletion chromosome 17 (del17) detected by FISH]. In the phase I of the trial 15 patients were enrolled. The first 3 patients at the dose level 0 of Carfilzomib did not experience any DLT. In the next cohort with Carfilzomib 20/45 mg/m2 a G3 hypertension and a sudden death occurred. According to the protocol, 3 more patients were enrolled at dose level 0: 1 patient experienced G3 atrial fibrillation, 2 patients ≥ G3 hypertension. Considering the serious adverse events (SAEs) occurred, the trial was temporary stopped to evaluate the benefit of continuing the study. All the DLTs were cardiologic and occurred in patients with a prior history of cardiac disease. As per protocol, they were evaluated with ECG and echocardiogram before the enrolment and were considered eligible for the study. The safety committee established new procedures for the evaluation of cardiac function of potentially eligible patients, including 24 h continuing pressure monitoring before the enrolment and serial measurement of blood pressure during and after Carfilzomib infusions. Six more patients were enrolled at dose level -1 (Carfilzomib 20/27 mg/m²) and none experienced a DLT. The MTD was established at dose level -1 with Carfilzomib 20/27 mg/m2, Pomalidomide 4 mg and Dexamethasone 40 mg. In the phase II portion of the trial, 42 patients were enrolled. Considering both phase I and II portions of the study, the most frequent drug related, grade ≥ 3 AEs were hematologic (65% of neutropenia and 13% of thrombocytopenia) and cardiologic (17%, mainly hypertension). We recorded only 4% of infection and ≥ G3 peripheral neuropathy. The overall response rate (ORR) of phase I/II portions was 58% (30/52) including 25% (13/52) of ≥ very good partial remission (VGPR). The ORR of high risk patients was 44% (7/16) including 19% (3/16) of ≥ VGPR. With a median follow-up of 10 months, median progression free survival (PFS) was 9.5 months and the median overall survival was not reached.

Conclusions: This is the first phase I/II trial that combined weekly Carfilzomib with Pomalidomide and Dexamethasone. This combination was highly effective in RRMM. After a median follow-up of 10 months, wKRd showed a double median PFS in comparison with Pomalidomide-low dose dexamethasone (Sanmiguel et al Lancet Oncology 2013): 9.5 vs 4 months respectively, confirming the efficacy of combining a PI with an IMiD. An updated analysis will be presented at the meeting.