[Tomizine--a new inhibitor of folate metabolism enzymes possessing an antitumor activity].

In the experiments on enzymic systems functioning in the metabolism of folic acid and on transplantable tumors in animals the preparation thomizine (chlorohydrate 4-methoxy-6-aminopyrimido (4,5-b) (1,4) thiazine) was worked out. Thomizine, as well as the known antimetabolite of folic acid-methotrexate, suppresses the activity of dihydrofolate reductase, but contrary to it suppresses FAP enzymic system, inhibiting aminopterin in the organism. Thomizine differes from methotrexate by another spectrum of antitumor effect, selective suppression of the tumor tissue growth, compared with the normal in vitro, it does not inhibit leucopoiesis, shows less toxicity and insignificant cumulative properties.