A Multi-Center Phase I/II Trial of Carfilzomib and Pomalidomide with Dexamethasone (Car-Pom-d) in Patients with Relapsed/Refractory Multiple Myeloma

Carfilzomib, a novel proteasome inhibitor (PI), and pomalidomide, an immunomodulatory agent (IMiD), have both demonstrated promising activity as single agents or in combination with dexamethasone in relapsed/refractory multiple myeloma. IMiD+PI combinations including lenalidomide, bortezomib, dexamethasone and lenalidomide, carfilzomib, dexamethasone have had high response rates and good tolerability. We aimed to combine carfilzomib and pomalidomide with dexamethasone (Car-Pom-d) for the first time and hypothesized that this regimen would be highly active in patients with relapsed/refractory multiple myeloma. Here, we report the first findings from the Phase I dose-escalation and expansion portions of the first phase I/II trial of Car-Pom-d in patients with relapsed/refractory multiple myeloma (NCT01464034).

The primary objectives were to determine the maximum tolerated dose (MTD) and the safety/tolerability of Car-Pom-d. Secondary objectives included determination of overall response rate, time to progression, progression free survival, and time to next therapy. All patients had to be refractory to prior lenalidomide, and must have been relapsed/refractory to their most recent therapy. Treatment consisted of 28-day cycles of oral pomalidomide once daily on days 1–21, intravenous (IV) carfilzomib over 30 minutes on days 1, 2, 8, 9, 15, and 16, and oral or IV dexamethasone 40 mg on days 1, 8, 15, and 22. Dose-escalation of carfilzomib started with 27mg/m² carfilzomib/4mg pomalidomide/40 mg dexamethasone using a standard 3+3 schema based on dose-limiting toxicities (DLTs) occurring in cycle 1. Carfilzomib was initiated at 20 mg/m²for Cycle 1, days 1–2 at all dose levels. Investigators were permitted to adjust the dose of dexamethasone at any point based on their discretion. Adverse events (AEs) were graded by NCI-CTCAE v4. Response was assessed by the modified International Uniform Response Criteria.

In the Phase I dose-escalation portion of the trial, a total of 12 patients were enrolled from 6 centers. The median age was 61 years (range 44–78), 67% were male. The median number of prior regimens was 6 (range 2–15), and median time from diagnosis was 5.1 years. Four (33%) patients had prior stem cell transplant, 11 (92%) had prior bortezomib, and all were lenalidomide-refractory. Cytogenetic abnormalities included 5 patients with del(17p), 2 patients with t(4;14), and 1 patient each with del(13), t(11;14), and t(14;16). In these first 12 patients, drug-related AEs occurring in >20% of patients included fatigue (42%), anemia (33%), pneumonia (33%), dyspnea (25%), and thrombocytopenia (25%). Six (50%) patients experienced grade ≥3 AEs including 2 incidence each of neutropenia and febrile neutropenia.

The MTD was established as the starting dose level (carfilzomib 20/27 mg/m², pomalidomide 4mg, dexamethasone 40 mg). At this dose, 1 of 6 patients experienced a protocol-defined DLT of febrile neutropenia. At dose level 2 (carfilzomib 20/36 mg/m², pomalidomide 4 mg, dexamethasone 40 mg), 2 of 6 patients experienced DLTs, consisting of grade 4 thrombocytopenia and grade 3 rash.

All 12 patients were response evaluable with 2 very good partial response (VGPR), 4 partial response (PR), 2 minor response (MR), 2 stable disease (SD), and 2 progressive disease (PD) for a ≥ MR rate of 67%. The 6 month progression free survival was 70% (95% CI: 37 to 90%). Of the 5 patients with del(17p), 1 achieved VGPR, 2 achieved PR, 1 achieved SD.

We then enrolled an expansion cohort of 20 patients from 8 centers resulting in a total study population of 32 patients, with 25 still receiving treatment. Three patients have died, all from progressive multiple myeloma. Early response assessments in 27 out of 32 patients show 2 VGPR, 7 PR, 6 MR, 8 SD, and 4 PD for a ≥MR rate of 56%.

The Car-Pom-d regimen is well tolerated and achieves a high response rate in a heavily pre-treated, lenalidomide-refractory population with prior bortezomib exposure. Importantly, we have seen responses in patients with poor risk cytogenetics, specifically del (17p). We are beginning enrollment in a larger phase 2 cohort, and updated safety and efficacy data for all patients will be presented at the meeting.

Shah:Celgene: Consultancy; Onyx: Consultancy; Novartis: Consultancy; Array: Consultancy. Stadtmauer:Celgene: Consultancy, Speakers Bureau; Millennium: Consultancy, Speakers Bureau. Abonour:Celgene: Honoraria, Speakers Bureau; Millenium: Honoraria, Speakers Bureau. Cohen:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Onyx: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees. Bensinger:Onyx: Research Funding; Celgene: Consultancy, Research Funding, Speakers Bureau. Gasparetto:Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millennium: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Kaufman:Millenium: Consultancy; Celgene: Consultancy; Novartis: Consultancy; Onyx: Consultancy. Lentzsch:Celgene: Consultancy, Research Funding. Vogl:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Millennium/Takeda: Consultancy, Research Funding; Otsuka: Consultancy; Acetylon: Research Funding. Orlowski:Onyx: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Research Funding. Durie:Onyx: Consultancy; Celgene: Consultancy; Millenium: Consultancy; Amgen: Consultancy.