2-Amino-6-mercapto-9β-d-ribofuranosylpurine (thioguanosine) has been used orally and intravenously in the treatment of 82 patients with leukemias and disseminated tumors.

The oral dose of thioguanosine required to produce toxic or therapeutic responses was less than half the oral dose of thioguanine necessary to produce comparable results calculated on a molar basis. However, the two compounds were equally active when given by the intravenous route, indicating that the difference in oral dosage of the two compounds was due to a difference in absorption.

Remissions have occurred in diseases which might have been expected to respond to the purine antagonists (acute leukemia in children and adults and chronic granulocytic leukemia) and only in cases which had not already become resistant to 6-mercaptopurine. Thioguanosine therefore appeared to have no qualitative or quantitative advantages over the previously available purine analogs.

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These studies were supported by research grants C1889 and CY3215 from the National Cancer Institute of the National Institutes of Health, Public Health Service; institutional grants from the American Cancer Society, the Damon Runyon Memorial Fund for Cancer Research, the Lasker Foundation, the Grant Foundation, and the Black-Stevenson Fund.

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