Triapine and cytarabine is an active combination in patients with acute leukemia or myelodysplastic syndrome

Triapine^®, an iron chelator and a potent inhibitor of ribonucleotide reductase, has significant anti-leukemia activity. A phase I study of Triapine in combination with ara-C was conducted in 32 patients with refractory acute leukemia and high-risk MDS. Triapine (105 mg/m²/day 6-h infusion) was followed immediately by ara-C [100 (n = 4), 200 (n = 6), 400 (n = 7), or 800 (n = 8) mg/m²/day] as an 18-h infusion for 5 consecutive days. Dose-limiting toxicities (DLTs) were observed at the 800 mg/m² ara-C dose level (one patient each with grade 4 mucositis; grade 4 neutropenic colitis, sepsis; grade 4 neuropathy; and grade 4 hyperbilirubinemia). Therefore, the study was amended to include an ara-C dose level of 600 mg/m²/day, no DLTs occurred in seven patients treated at this dose level. Mean Triapine C_max and AUC were 1.13 μg/mL and 251.5 min μg/mL. Of 31 evaluable patients, 4 (13%) (3 AML, 1 Ph + ALL) achieved a CR (1 at a dose of 800 mg/m²; 2 at 600 mg/m²; 1 at 200 mg/m²). The recommended phase II regimen is Triapine 105 mg/m²/day followed by ara-C 600 mg/m²/day for 5 consecutive days every 3-6 weeks.