3500 Background: Our preclinical model established the rationale for using azacitidine to reverse platinum resistance. Sequential azacitidine and carboplatin treatment conferred an effect against platinum resistant ovarian cancer cells that was greater than from each agent alone (synergistic interaction). Based on a well tolerated phase I regimen of azacitidine 75 mg/m2/day for 5 days plus carboplatin AUC 5 on day 2 once every 28 days, we initiated a phase IIa trial to evaluate efficacy. Methods: Patients with pathologically confirmed epithelial ovarian cancer who progressed within 6 months after a platinum-based regimen (resistant, Plat-RS, n=18) or on a platinum- based regimen (refractory, Plat-RF, n=12), were eligible to receive sequential azacitidine and carboplatin. All patients had measurable disease. Results: Thirty patients received a total of 159 cycles of treatment and 2 patients are still being actively treated at the cycle 14 and 19, respectively. Side effects include neutropenia, anemia, fati...