Phase Ib Study of Oral Panobinostat In Combination with 5-Azacitidine (5-aza) In Patients with Myelodysplastic Syndromes (MDS), Chronic Myelomonocytic Leukemia (CMML), or Acute Myeloid Leukemia (AML)

Panobinostat is a potent pan-deacetylase inhibitor (pan-DACi) that causes increased acetylation of target proteins such as HSP90, p53, α-tubulin and HIF-1α which are involved in cell cycle regulation, gene transcription, angiogenesis, and tumor cell survival. Preliminary evidence from phase I trials has demonstrated anti-tumor activity in patients with hematologic malignancies including myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). The advent of hypomethylating agents, such as 5-aza, represent a significant advancement in the treatment of MDS, chronic myelomonocytic leukemia (CMML), and AML. Although an improvement in clinical outcomes has been observed, including increased overall survival in patients with MDS, a substantial number of patients do not benefit from the therapies currently available. Preclinical studies suggest that the combination of a demethylating agent and a pan-DACi represents a rational strategy to reverse silencing of tumor suppressor genes, which contributes to the malignant phenotype, and improve outcomes in patients with MDS and AML. In this study, the combination of the pan-DACi, panobinostat, and the hypomethylating agent, 5-aza, was evaluated in patients with MDS, CMML and AML.

This phase Ib, open-label, multicenter, dose-finding study is comprised of 2 stages: a dose-escalation stage to determine the maximum tolerated dose (MTD) of panobinostat in combination with standard dose 5-aza, and a subsequent expansion stage to evaluate safety, tolerability, and preliminary activity at the MTD dose level. The primary endpoint is incidence of dose-limiting toxicity (DLT) and secondary endpoints include type, duration, frequency, and relationship of adverse events (AEs) to the combination. Exploratory endpoints include clinical response and hematologic improvement according to IWG response criteria, and biomarker analysis of methylation status and expression of disease-associated genes in peripheral blood cells prior to and during therapy. Adult patients with IPSS INT-2 or high-risk MDS, CMML, or AML with multi-lineage dysplasia and ≤ 30% marrow blasts who are candidates for therapy with 5-aza and have not received a prior hypomethylating agent or pan-DACi are eligible for enrollment on the trial. Oral panobinostat was administered on Days (D) 3, 5, 8, 10, 12, and 15, starting at 20 mg, in combination with 5-aza (75 mg/m² sc D 1–7) during a 28-D cycle. Patients received treatment for ≤ 6 cycles or until progression of disease, incidence of unacceptable toxicity, or withdrawal of consent.

To date, 11 patients have been enrolled including 9 patients with MDS, 1 patient with AML and 1 patient with CMML. The median age of patients enrolled on the trial was 69.0 (60-80). Patients have been evaluated at 2 panobinostat dose cohorts; 6 (20 mg) and 5 (30 mg). The AE analysis is based on 9 patients (6 from 20 mg cohort and 3 from 30 mg cohort) and the nature and incidence of AEs observed in the two cohorts were similar. Adverse events regardless of study drug relationship included nausea (4 [44%]), vomiting, fatigue (5 [55%] each) and asthenia (3 [33%]). Grade 3/4 AEs suspected to be treatment related included thrombocytopenia (2 [22%], febrile neutropenia and arthritis (1 [11%] each). Serious adverse events observed included febrile neutropenia, asthenia (2 [22%] each), atrial fibrillation and septic shock (1 [11%] each). One DLT has been observed (grade 4 febrile neutropenia) in the 20 mg panobinostat dose cohort.

Panobinostat has been well tolerated up to a dose of 30 mg in combination with 5-aza (75 mg/m²) with dose escalation ongoing. Patients are currently being enrolled at the 40mg dose cohort. The most common AEs observed included febrile neutropenia, thrombocytopenia with one DLT observed (grade 4 febrile neutropenia) in the 20mg panobinostat dose cohort. The current data show that the addition of panobinostat to 5-aza is safe with no unexpected toxicities. Updated data, including safety and preliminary efficacy data will be presented at the meeting.

Fenaux: Celgene: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Janssen Cilag: Honoraria, Research Funding; ROCHE: Honoraria, Research Funding; AMGEN: Honoraria, Research Funding; GSK: Honoraria, Research Funding; Merck: Honoraria, Research Funding; Cephalon: Honoraria, Research Funding. Off Label Use: Panobinostat is an investigational agent currently being evaluated for the treatment of hematologic and solid malignancies. DeAngelo: Novartis: Membership on an entity's Board of Directors or advisory committees. Sekeres: Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Winiger: Novartis Pharma AG: Employment. Squier: Novartis: Employment. Li: Novartis: Employment. Ottmann: Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees.