The carcinogenic potential of
oxisuran, a synthetic
immunosuppressive agent, was studied for 80 weeks and 104 weeks in mice and rats, respectively. Groups of 50 mice and 70 rats of each sex received
oxisuran at doses of 600, 240, and 40 mg/kg/day as dietary admixtures over the entire experimental period. Adequate survival rates allowed accurate statistical analysis of diagnosed
neoplasia. Increased susceptibility to
tumor development was not clearly demonstrated. In mice the only statistically significant increase in the incidence of
malignancy was lung
carcinomas in high dose females (P less than 0.05). However, lung
carcinoma incidence was significantly decreased in mid- and low-dose male mice when compared to spontaneous control rates (P less than 0.01). Although not confirmed statistically, there was an increased incidence of lung
carcinomas and
liver cell adenomas in high dose male mice, and increased lymphoid
tumors in all female treated groups. In rats, the incidence of
liver cell adenomas in high dose animals of both sexes was increased, although confirmed statistically in males only (P less than 0.01). In high dose females, significantly decreased incidences of mammary
fibroadenomas, pituitary
chromophobe adenomas, and thyroid parafollicular cell
tumors (P less than 0.01) contributed to an overall decrease in both benign
tumors and in the combined benign and malignant
tumor rates.