THE METABOLISM OF 9-ARABINOSYL-6-MERCAPTOPURINE IN NORMAL AND NEOPLASTIC TISSUES

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Abstract
Arabinosyl-6-mercaptopurine (ara-6-MP) was found to increase the survival time of mice bearing 6-mercaptopurine (6-MP)-sensitive or 6-MP-resistant tumors. Studies with the radiosulfur-labeled drug in mice showed that the drug was rapidly cleared from the blood, distributed throughout the tissues, and relatively rapidly excreted in the urine. Arabinosyl-6-mercaptopurine was neither cleaved to 6-mercaptopurine by the Ehrlich ascites tumor nor converted to nucleotide to any appreciable extent under the conditions studied. Arabinosyl-6-mercaptopurine at a dosage level of 300 mg/kg produced a minimal inhibition of orotic acid-6-C14incorporation into the DNA cytosine of the Ehrlich ascites tumor. No effect on the incorporation of glycine-2-C14into acid-soluble or nucleic acid purines of the Ehrlich ascites tumor was noted at this dosage level. No toxicity has been observed with the doses of ara-6-MP studied (300 mg/kg).