Epigenetic changes have been shown to play a role and to cooperate with genetic alterations in the pathogenesis of myelodysplastic syndromes (MDS). The potential reversibility of DNA and chromatin modifications makes chromatin remodeling enzymes attractive targets for therapeutic intervention in this disease. We conducted a phase II study on the combination of the DNMT inhibitor 5-azacitidine (5-AZA), the histone deacetylase inhibitor valproic acid (VPA), and all-trans retinoic acid (ATRA) in patients with intermediate-2/high-risk myelodysplastic syndromes. Bone marrow morphology was centrally reviewed before enrolment. VPA was given at 600–1500 mg daily to reach a final plasma concentration above 50 microg/ml, then 5-AZA was added at a standard dose of 75 mg/sqm daily, subcutaneously, 7 days for 8 cycles. In case of minor response, stable disease or failure after 4 cycles, ATRA was added at 30 mg/sqm orally daily, on days 8–27 for 4 cycles. Treatment was continued in responding patients until response persisted. The protocol included 62 patients (43 males, 19 females, median age 67 years, range 53–83 yrs). Diagnosis was RAEB for 37 patients (60.7%), RAEB-t for 21 (32.8%), and CMML for 4 patients (6.5%). The IPSS was int-2 (1.5) for 46 patients and High (≥2) for 16 patients. A valproic acid concentration between 45 and 55 microg/ml was reached in a median of 7 days (range 4–28 days). Three patients died before start of treatment, while 58.7% of patients (95% C.I.: 51.3–67.1) were alive at 12 months. Out of 27 patients who completed 8 treatment cycles, 8 patients (29.6%) obtained complete and partial remission, 3 patients (11.1%) major hematological improvement while 10 patients (37.4%) showed a stable disease. Transformation into AML or progression occurred in 20 patients. RBC transfusion needs decreased significantly from a median of 3 units (range 0–16) before start of treatment to 0 (range 0–7) after 8 cycles. Neurological toxicity occurred in 6 patients. Our data show that the 5-AZA/VPA/ATRA combination is safe and feasible in poor prognosis MDS patients.

Disclosures: Off Label Use: Valproic acid: HDAC inhibitor ATRA: differentiating agent.

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