Melphalan, Thalidomide and Prednisone (MPT) Combined with Oral Panobinostat In Patients with Relapsed/Refractory MM: a Phase I-II Study

Panobinostat (LBH-589) is a pan-deacetilase inhibitor that targets histone proteins increasing tumor suppressor gene activities leading to cell-cycle and differentiation arrest besides to target non-histone proteins such as HSP90, aggressomes, p53, HIF-1a, and a-tubulin somehow promoting cell death. Panobinostat, combined with steroids and/or immunomodulatory drugs, demonstrated additive/synergistic activity in Multiple Myeloma (MM) and ability to overcome previous chemoresistance. Several combination studies with Panobinostat plus novel drugs are now ongoing in MM.

This is a multicenter, open-label, phase I-II study exploring the combination of a standard therapy such as MPT (Melphalan 0.18 mg/kg per os for 4 days, Prednisone 1.5 mg/kg per os for 4 days, Thalidomide 50 mg/day continuously) with Panobinostat 15 mg p.o. thrice weekly for 3 weeks in a 28-day cycle to assess safety profile and activity of this combination in patients with relapsed/refractory MM having adequate performance status and haematological, cardiac, liver and neurological functions. The study was designed according to the Briant and Day method that plans a “dose-escalation phase” to determine both the MTD and the activity of the study drug and an “expansion-phase” in which the MTD of the study drug is used to further assess its safety and efficacy. Despite in the first phase of this study 19 patients were planned according to the study design, protocol was amended after 13 patients had been enrolled since more than 50% grade 3–4 toxicity occurred although response criteria were met. Therefore, Panobinostat was reduced to 10 mg p.o. thrice weekly for 3 weeks in a 28-day cycle whereas the dose of drugs of the MPT combination was not modified. Toxicity and response were assessed according to CTC version 4 and IMWG criteria, respectively.

As of February 2010, 24 patients were enrolled in this study. Median age was 71.5 years (range 40–81 years) and 12 patients (50%) had ISS 2–3 score. Patients had received a median of 2 prior therapies (range 1–6) and 5 (21%) three or more prior lines of therapy. Sixteen (73%), 13 (54%), 18 (75%), 11 (46%) and 9 (37.5%) patients had been previously treated with ASCT, thalidomide, bortezomib, lenalidomide and all 3 new-drugs, respectively. Seven patients (29%) were refractory to the last therapy. Twelve patients (50%) had a disease history longer than 5 years. In the first 13 patients treated with Panobinostat 15 mg, grade 3–4 thrombocytopenia and neutropenia occurred in 6 (46%) and 9 patients (69%), respectively. Moreover, 4 patients (31%) developed non-hematological adverse events such as fatigue, constipation, infection and arrythmia. In the group of 11 patients treated with Panobinostat 10 mg, grade 3–4 thrombocytopenia decreased to 18% (2 patients) but neutropenia was still high (8 patients: 72.5%). Three patients (27%) had grade 3–4 non-hematological toxicity (one fatigue and two constipation). No patients had QTcF prolongation or severe neuropathy. Dose adjustment was necessary in 9 patients (37.5%, all due to hematological toxicity) while 6 patients (25%) interrupted the protocol because of side effects (5 due to no resolution of grade 3–4 hematological toxicity within 4 weeks and one due to atrial fibrillation). One patient (4%) died on study due to sepsis during prolonged neutropenia. Response ≥ PR were observed in 12 patients (50%) including 4 VGPR and 8 PR. Additionally, 2 patients had MR and 8 SD. Only 2 patients progressed during treatment. There was no difference between the two cohorts of patients (Panobinostat 15 mg and Panobinostat 10 mg) in terms of response ≥ PR (54% vs 45.5%) or disease progression (7.5% vs 9%). Notably, response was obtained also in 2/7 patients (28%) who progressed during bortezomib or IMIDs.

This study suggests that MPT-Panobinostat combination has an encouraging anti-myeloma activity since responses were still seen in patients with advanced stage or resistant to new drugs diseases. Different schedules of Panobinostat/melphalan should be explored to reduce haematological toxicity.

Offidani:Celgene: Honoraria. Off Label Use: Panobinostat in relapsed/refractory multiple myeloma. Cavallo:Celgene: Honoraria. Polloni:Celgene: Honoraria. Ballanti:Celgene: Honoraria. Catarini:Celgene: Honoraria. Alesiani:Celgene: Honoraria. Corvatta:Celgene: Honoraria. Gentili:Celgene: Honoraria. Boccadoro:Celgene: Honoraria, Research Funding. Leoni:Celgene: Honoraria. Palumbo:Celgene: Honoraria, Research Funding.