Phase I study of sapacitabine, an oral nucleoside analogue, in patients with advanced leukemias or myelodysplastic syndromes
7063 Background: Sapacitabine, a 2′-deoxycytidine nucleoside analogue with unique ability to induce G2 cell cycle arrest and cause irreparable single-strand DNA breaks, is undergoing clinical evaluation for the treatment of cancer. The recommended Phase II dose (RD) in patients with advanced solid tumors was 75 mg b.i.d.×7 days orally every 21 days. The major DLT was myelosuppression. Here, we present the initial results of a Phase I study of sapacitabine in patients with advanced leukemias or MDS. The primary objective was to define the MTD of the above dosing schedule and the secondary objectives were to characterize the PK/PD effects of sapacitabine and its major metabolite CNDAC. Methods: Eligible patients had relapsed/refractory leukemias or MDS, or untreated disease if not willing to proceed with conventional systemic chemotherapy, adequate organ functions and performance status of 0–2. At least 3 patients were enrolled at each dose level. The MTD was the highest dose level at which =2/6 patients experienced a DLT during the first treatment cycle. Results: Twenty- nine patients received sapacitabine. Median age was 64 (range: 36 - 91). The majority of patients had AML (n=24) or MDS (n=4). Median number of prior chemotherapies was 2 (range: 0 - 6). MTD was reached at the dose level of 375 mg b.i.d. with 2/7 patients experienced the DLT of small bowel obstruction (n=1) or neutropenic colitis (n=1). One patient died from complications of neutropenic colitis. Common non-hematologic adverse events (all grades, regardless of causality) included nausea, vomiting, diarrhea, anorexia, alopecia, and fatigue, most of which were mild to moderate in intensity. PK and PD data are being analyzed. To date, 7 patients (5 AML, 2 MDS) had a reduction in bone marrow blast counts to = 5% including 1 CR in refractory AML with incomplete platelet recovery and 1 CR in relapsed MDS. In addition, 2 AML patients with relapsed leukemia cutis had a significant reduction in leukemia infiltrates in skin. Conclusion: The RD of sapacitabine for the b.i.d.×7 days every 21 days schedule is 325 mg b.i.d. The DLT is gastrointestinal toxicity. Sapacitabine is well tolerated and has promising antileukemic activity in patients with relapsed or refractory AML and MDS. No significant financial relationships to disclose.