Cytembena is a cytostatic and a carcinogenic compound that may increase the incidence of fibroadenomas.Cytembena broadly inhibits DNA biosynthesis.

Cytembena was given i.p. in doses of 5, 10, 20, 40, and 80 mg/kg body wt. to Wistar rats and in doses of 20, 40, and 80 mg/kg body wt. to ICR mice and to Chinese hamsters. Five patients with various types of malignancy, so far medically untreated, received 20 mg Cytembena/kg body wt i.v. A combination of Cytembena and cyclophosphamide was applied i.p. in single equal doses 1: 1 of 5,10, 20, and 40 mg/kg body wt to ICR mice, Chinese hamsters, and Wistar rats. Patients were given i.v. 20 mg Cytembena and 20 mg cyclophosphamide/kg body wt. Bone marrow cells were examined 24 h after the administration. The frequency of abnormal metaphases and chromosomal breaks after Cytembena treatment was low; nonetheless, the indicated dose-effect relationship was found in all the rodents used. The frequency of chromosomal breaks was 2-3 times higher in rodents in comparison with men, after treatment with a dose of 20 mg Cytembena/kg body wt. The highest frequencies of induced aberrations were found in mice. The rodents appeared to be 3--4 times more sensitive to the induction of chromosomal breaks and abnormal metaphases than men, after a dose of 20 mg Cytembena and 20 mg cyclophosphamide/kg body wt.[1]