International Agency for Research on Cancer (IARC) - Summaries & Evaluations


VOL.: 26 (1981) (p. 249)

5. Summary of Data Reported and Evaluation

5.1 Experimental data

6-Mercaptopurine was tested by intraperitoneal administration and by skin painting (followed by croton oil) in mice and by intraperitoneal, subcutaneous and intravenous routes of administration in rats. Limitations to the data in all the reports precluded evaluation of the possible carcinogenicity of 6-mercaptopurine.

6-Mercaptopurine and 6-mercaptopurine riboside were proven to cause embryolethality at doses nontoxic to the mother and to induce severe teratogenic effects in several animal species. 6-Mercaptopurine is mutagenic in bacteria and in mice. It also produces chromosomal aberrations in various mammalian cells, including human peripheral lymphocytes tested in culture.

5.2 Human data

6-Mercaptopurine has been used commonly since the 1960s in the treatment of acute leukaemias.

It produces chromosomal aberrations in peripheral lymphocytes. No data were available to evaluate the mutagenic potential of the drug in humans. The available data are not sufficient to establish whether 6-mercaptopurine can induce a teratogenic effect.

A small number of case reports document the occurrence of acute nonlymphocytic leukaemia in patients who received 6-mercaptopurine for both non-neoplastic and neoplastic disorders. No epidemiological study was available to the Working Group.

5.3 Evaluation

There was no evidence for the carcinogenicity of 6-mercaptopurine in the limited studies in experimental animals. The data from case reports in humans were insufficient to arrive at a conclusion.

On the basis of the available data, no evaluation could be made of the carcinogenic risk of 6-mercaptopurine to humans.

Subsequent evaluation: Suppl. 7 (1987)

Last updated: 8 April 1998

    See Also:
       Toxicological Abbreviations
       Mercaptopurine, 6-  (IARC Summary & Evaluation, Supplement7, 1987)