Phase I study of the ribonucleotide reductase inhibitor 3-aminopyridine-2-carboxaldehyde-thiosemicarbazone (3-AP) in combination with high dose cytarabine in patients with advanced myeloid leukemia

Invest New Drugs. 2008 Jun;26(3):233-9. doi: 10.1007/s10637-008-9115-6. Epub 2008 Jan 24.


Purpose: This Phase I dose escalation study was based on the hypothesis that the addition of 3-aminopyridine-2-carboxaldehyde-thiosemicarbazone (3-AP) to cytarabine would enhance cytarabine cytotoxicity. The primary objective of the study was to establish the maximum tolerated dose of 3-AP when given in combination with a fixed dose of cytarabine.

Experimental design: Twenty-five patients with relapsed or refractory myeloid leukemia were enrolled to three dose levels of 3-AP. Cytarabine was administered as a 2 h infusion at a fixed dose of 1,000 mg/m2/day for 5 consecutive days. Escalating doses of 3-AP as a 2 h infusion were administered on days 2 through 5. The 3-AP infusion preceded the start of the cytarabine infusion by 4 h.

Results: In general, the toxicities observed with the combination were similar to the expected toxicity profile for cytarabine when utilized as a single agent at this dose and schedule. However, two of three patients developed dose-limiting methemoglobinemia at the highest 3-AP dose studied (100 mg/m2). Transient reversible methemoglobinemia was documented in 11 of 15 patients enrolled at the 75 mg/ m2 dose level. Objective evidence of clinical activity was observed in four patients.

Conclusions: The combination of 3-AP and cytarabine given on this schedule is feasible in advanced myeloid leukemia. The recommended Phase II dose is 75 mg/m2/day of 3-AP on days 2-5 given prior to cytarabine administered at a dose of 1,000 mg/m2/day over 5 consecutive days. Methemoglobinemia is a common toxicity of this combination and requires close monitoring.

Publication types

  • Clinical Trial, Phase I
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Combined Chemotherapy Protocols / administration & dosage
  • Antineoplastic Combined Chemotherapy Protocols / adverse effects
  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use*
  • Cytarabine / administration & dosage
  • Drug Monitoring
  • Female
  • Humans
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / drug therapy*
  • Leukemia, Myeloid, Acute / drug therapy*
  • Male
  • Maximum Tolerated Dose
  • Methemoglobinemia / chemically induced
  • Middle Aged
  • Pyridines / administration & dosage
  • Recurrence
  • Thiosemicarbazones / administration & dosage


  • Pyridines
  • Thiosemicarbazones
  • Cytarabine
  • 3-aminopyridine-2-carboxaldehyde thiosemicarbazone