6500 Background: MGCD0103 is a novel 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.
METHODS
To study the safety and activity of MGCD0103, we have developed a phase I open-label dose escalation study of MGCD0103 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 MGCD0103. 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.
RESULTS
Twenty patients have been enrolled at four dose levels (20, 40, 80 and 60 mg/m2) so far. Their characteristics are: median age 60 years (range 33-76); the majority of patients so far treated have AML; median number of prior therapies is 1 (range 0-3). Most patients had complex cytogenetics. MGCD0103 has been well tolerated at doses below 80 mg/m2. The MTD has been reached, with 3 out of 4 patients at a dose of 80 mg/m2 developing grade 3 toxicity, mainly fatigue, nausea, vomiting or diarrhea. Grade 2 toxicities include anorexia, constipation, dehydration. The median number of courses is 1 (range 1 to 6). As of January 2006, 7 patients are on study. PK evaluations show dose-dependent exposure. Analysis of peripheral blood cell HDAC activity indicates that HDAC inhibition occurs in all patients in a dose-dependent manner. Two patients with multiple relapsed/refractory acute myelogenous leukemia, and one with MDS have achieved a complete marrow response (blasts less than 6%). Of importance, maximal HDAC inhibition was observed in those patients at the time of best response.
CONCLUSIONS
Single-agent MGCD0103 has clinical activity and is well tolerated at doses below 80 mg/m2 orally three times a week in patients with advanced leukemia. No significant financial relationships to disclose.