A Phase I Study of the Histone Deacetylase Inhibitor MGCD0103 (MG-0103) Given as a Three-Times Weekly Oral Dose in Patients with Leukemia or Myelodysplastic Syndromes (MDS).

MG-0103 is a novel non-hydroxamic acid inhibitor of human histone deacetylases (HDACs), with selectivity for the cancer-associated isoforms of class I HDACs. Deacetylation of histones by HDACs is postulated to inactivate tumour suppressor genes leading to neoplastic transformation, and therefore inhibition of this enzyme may result in antineoplastic activity. To study the safety and activity of MG-0103, we have developed a phase I open-label dose escalation study of MG-0103 administered orally, three-times weekly in patients with leukemia or MDS, with the primary endpoints being the determination of the maximum tolerated dose (MTD) and the pharmacokinetic (PK) and pharmacodynamic (PD) characteristics of MG-0103. Eligibility criteria included appropriate performance status and renal and hepatic functions. Patients with relapsed/refractory leukemia or MDS and older patients with untreated AML/MDS were eligible. Eight patients have been enrolled at two dose levels (20 &40 mg/m2) so far. Their characteristics are: median age 70 years (range 33–79); all patients so far treated have AML; median number of prior therapies is 1 (range 0–3). All patients had complex cytogenetics including one elderly patient with t(8;21) that had not achieved CR with high dose ara-C-based therapy. MG-0103 has been well tolerated with no dose-limiting toxicities. No drug-related adverse events (AEs) >= Grade (Gr) 3 have been observed. The only Gr 2 drug-related AE has been heartburn (1 patient). All other drug-related AEs were grade 1. No cardiac abnormalities have been observed so far. Two of 3 patients at the first dose level have been treated for 3 or more cycles. PK evaluations are shown in the table below. Analysis of peripheral blood cell HDAC activity indicates that HDAC inhibition occurs in a dose-dependent manner. Enrolment is currently proceeding at a dose of 80 mg/m2. In summary, MG-0103 is a well-tolerated HDAC inhibitor in patients with AML at doses and exposures that result in target inhibition in peripheral blood.