Vorinostat in Combination with Decitabine for the Treatment of Relapsed or Newly Diagnosed Acute Myelogenous Leukemia (AML) or Myelodysplastic Syndrome (MDS): A Phase I, Dose-Escalation Study.

Although the introduction of epigenetic therapies, such as the DNA methyltransferase inhibitor (DNMT) decitabine, has improved options for the treatment of myeloid malignancies, use is limited by sub-optimal response rates. Therefore, there remains a need for more effective treatment strategies to improve outcomes in AML/MDS. Preclinical and clinical data suggest that broadening epigenetic targeting by adding histone deacetylase (HDAC) inhibitors to DNMTs may improve responses. In addition, it has been reported that outcomes may differ according to the sequence in which HDAC and DNMT inhibitors are combined.

Here we present preliminary data from a Phase I, open-label, multicenter, dose-escalating study, designed to determine the maximum-tolerated dose (MTD) and recommended Phase II dose of the HDAC inhibitor vorinostat combined either concurrently or sequentially with decitabine in patients (pts) with AML/MDS. Other endpoints include tolerability and exploratory assessments of activity.

Pts (≥18 years) with intermediate-high risk MDS, relapsed/refractory AML, or untreated AML (≥60 years; unsuitable for standard chemotherapy), with an ECOG performance status of ≤2, were enrolled into one of six dosing levels (Table) and received treatment for up to 24 months or until disease progression (PD).

As of August 3, 2009, 72 pts have entered the study: median age was 68 years (range 18-85) and 58% were male. To date, 69 pts have discontinued due to PD/lack of efficacy (n=37), withdrawal of consent (n=12), adverse events (AEs) (n=16), physician decision (n=3), and protocol deviation (n=1). Of 70 pts evaluable for safety, 69 experienced AEs, the majority of which were Grade 1/2 in severity and included nausea (n=48), diarrhea (n=41), fatigue (n=36), constipation (n=32), and vomiting (n=28). 62 (89%) pts experienced treatment-related AEs and 17 (24%) pts experienced treatment-related serious AEs. 14 deaths occurred during the study, although none were related to study treatment. One dose-limiting toxicity, prolonged QT interval, was documented in dose level 3a. Combinations of vorinostat and decitabine in the schedules in this protocol did not reach MTD. As per protocol, dose levels 3 and 3a were the maximum administered doses and have been expanded. Of the 61 pts evaluable for response, 11 had MDS, 25 had relapsed/refractory AML, and 25 had untreated AML. In pts with MDS receiving concurrent therapy (n=5), complete remission (CR) was achieved in 2 pts, stable disease (SD) in 1 pt, partial remission (PR) in 1 pt, hematologic improvement (HI) in 1 pt; all 6 of the pts who received sequential treatment experienced SD. In pts with relapsed/refractory AML receiving concurrent therapy (n=12), CR was achieved in 1 pt, CR without recovery of counts (CRi) in 1 pt, HI in 1 pt, SD in 6 pts, while 3 pts had PD; in those receiving sequential therapy (n=13), SD was achieved in 9 pts while 4 had PD. In pts with untreated AML receiving concurrent therapy (n=12), CR was achieved in 4 pts, CRi in 1 pt, PR in 1 pt, and SD in 6 pts, and in those receiving sequential therapy (n=13), CR was achieved in 2 pts, CRi in 2 pts, PR in 1 pt, HI in 2 pts, and SD in 5 pts. Overall, CR or CRi was achieved by 18% pts with MDS, 8% with relapsed/refractory AML, and 36% with untreated AML; and HI was reported in 9% pts with MDS, 4% with relapsed/refractory AML, and 8% with untreated AML.

These preliminary data indicate that the combination of vorinostat with decitabine, either concurrently or sequentially, is possible without significant toxicity. In addition, the combination shows promising activity in MDS and untreated AML.

Kirschbaum:Merck: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celegene: Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Off Label Use: Vorinostat is a histone deacetylase (HDAC) inhibitor that was approved in the FDA in October 2006 for the treatment of cutaneous manifestations in patients with cutaneous T-cell lymphoma (CTCL) who have progressive, persistent, or recurrent disease on or following two systemic therapies. Goldberg:Merck: Research Funding. Marks:Merck: Research Funding. Di Gravio:Merck: Employment, Equity Ownership. Pyle:Merck: Employment, Equity Ownership. Rizvi:Merck: Employment, Equity Ownership. Issa:Eisai: Consultancy, Research Funding; Celegene: Research Funding; MGI Pharma: Research Funding.