Background: Epigenetic silencing of genes has been documented in AML. This phase I trial evaluates the safety, tolerability, and maximum tolerated dose (MTD) of two schedules of administration of the hypomethylating agent decitabine in combination with the pan-selective histone deacetylase inhibitor vorinostat.

Methods: Patients receive escalating doses of oral vorinostat administered either sequentially [100 mg bid (n=4), 200 mg bid (n=4), or 200 mg tid (n=8) Days 6–21] or concurrently [100 mg (n=3) or 200 mg (n=6) bid Days 1–21 or 200 mg tid (n=2) Days 1–14] with decitabine (20 mg/m²/d IV Days 1–5) every 28 days.

Results: Twenty-seven patients with AML have been treated. Median age was 67 years (range, 32–82 years). Median ECOG status 1 (range, 0 to 2). Eighteen patients (67%) had received prior therapy (median, 1 regimen; range, 0 to 4 regimens); 3 had received a prior allogeneic stem cell transplant. A total of 85 cycles have been administered, with a median of 2 cycles (range, 1 to 13 cycles); 10 patients (37%) have received 3 or more cycles of therapy. One of 7 patients treated at dose level 3 of the sequential schedule developed dose-limiting toxicities (DLT), consisting of grade 3 fatigue, weakness, and mucositis. Therefore, the MTD was not reached in the 3 planned dose levels of the sequential schedule. One DLT (grade 3 fatigue) occurred in 6 patients treated at dose level 2 of the concurrent schedule. Most common drug-related non-hematological toxicities of any grade (all CTCAE grades 1 or 2) were nausea (71%), fatigue (54%), diarrhea (54%), vomiting (42%), anorexia (25%), constipation (13%), abdominal pain (13%), dehydration (13%), and headache (13%). No other non-hematological grade 3 or 4 toxicities were observed. Of the 25 evaluable patients, one patient achieved an incomplete CR (without neutrophil recovery), one a morphologic leukemia-free state (without blood count recovery), and three partial remissions (1 achieved red cell transfusion independency and a second normalization of platelet counts). Seven of these patients remain on study for 2.7 to 13.5+ months. Correlative studies examining histone acetylation and gene promoter methylation in leukemic cells at baseline and after treatment, as well as plasma pharmacokinetic levels for both decitabine and vorinostat are being evaluated.

Conclusions: The combination of decitabine and vorinostat is safe, well-tolerated, and has clinical activity in patients with AML. Enrollment is ongoing.