Phase 1/1b Study of the Efficacy and Safety of the Combination of Panobinostat + Carfilzomib in Patients with Relapsed and/or Refractory Multiple Myeloma

Carfilzomib, a novel irreversible proteasome inhibitor (PI), has demonstrated single agent activity in, and was recently FDA approved for relapsed and refractory myeloma. Panobinostat, a potent histone deacetylase inhibitor (HDACi), has been studied as a single agent and in combination with bortezomib, demonstrating promising response rates and a favorable safety profile in bortezomib-refractory patients. Our hypothesis proposed that the combination of carfilzomib and panobinostat (Car-Pan) would also be highly active, and we therefore aimed to combine these two agents for the first time. We report the initial findings from the phase I dose-escalation and expansion portions of our phase I/II trial of this novel combination regimen.

The primary objectives were to determine the maximum tolerated dose (MTD) and the safety/tolerability of Car-Pan in patients with relapsed or refractory multiple myeloma. Secondary objectives included determination of the overall response rate, time to progression, progression free survival, and time to next therapy. Panobinostat was administered orally on days 1, 3, 5, 8, 10, 12 of every 28-day cycle, while carfilzomib was given intravenously over 30 minutes on days 1, 2, 8, 9, 15, and 16. Dose level 1 started carfilzomib at 20 mg/m² with 15 mg of panobinostat, and escalated from there using a standard 3+3 schema based on dose-limiting toxicities (DLTs) occurring in cycle 1. An amendment was later introduced to allow carfilzomib to be given at 20 mg/m²for days 1 and 2 of cycle 1, followed by an increase to the full dose level for that cohort. Adverse events (AEs) were graded using the NCI-CTCAE v4, and responses were assessed with the modified International Uniform Response Criteria.

To date, 20 patients have been enrolled, 3 of whom are still in their first cycle, leaving 17 evaluable patients who are described herein, who have received a median of 4 cycles (range 1–8). The median age was 62 years (range 46–73), 11/17 (70%) were male, and the median number of prior regimens was 5 (range 2–15). Patients were very heavily pretreated, with 16/17 (94%) having undergone stem cell transplantation, 16/17 (94%) having prior bortezomib, including 8/17 (47%) who were bortezomib-refractory, and 17/17 (100%) having prior lenalidomide, including 12/17 (70%) who were lenalidomide-refractory. Cytogenetic abnormalities were common, including: 4 with del(17p), 4 with t(4;14), 2 with t(11;14), 9 with del(13), of whom 7 had additional mutations. Grade 1–4 AEs regardless of causality occurring in >20% of patients included anemia (14/17), thrombocytopenia (17/17), neutropenia (8/17), diarrhea (9/17), nausea/emesis (7/17), fatigue (10/17), elevated creatinine (8/17), and pneumonia (5/17). Grade ≥3 AEs regardless of causality included anemia (7/17), thrombocytopenia (10/17), neutropenia (6/17), diarrhea (2/17), nausea/emesis (1/17), fatigue (4/17), elevated creatinine (2/17), and pneumonia (4/17). An MTD has not been established, and dosing is ongoing in cohort 4, with Carfilzomib at 45mg/m²and 20 mg of Panobinostat. Of the 17 evaluable patients, the overall response rate was 35% (6/17) who achieved at least a partial response (PR); including 2 with very good PR (VGPR). In addition, one patient had a minor response, and 65% overall achieved stable disease or better.

The combination of Carfilzomib + Panobinostat is well tolerated with a manageable side effect profile. Importantly, the combination achieves a promising response rate in a very heavily pre-treated, lenalidomide/bortezomib/high dose melphalan-refractory population, with an overall response (≥PR) rate of 35%. Updated safety and efficacy data for all patients will be presented at the meeting.

Shah:Onyx: Honoraria, Research Funding, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Array BioPharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Research Funding, Speakers Bureau. Off Label Use: This presentation will include information about panobinostat, which is not yet approved for use in patients with multiple myeloma. Thomas:Celgene: Research Funding; Millenium: Research Funding; Novartis: Research Funding; Immunomedics: Research Funding; Johnson & Johnson: Research Funding; Onyx: Membership on an entity's Board of Directors or advisory committees. Wang:Onyx Pharmaceuticals: Honoraria, Research Funding. Orlowski:Onyx: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees.