Lack of mutagenicity and teratogenicity of 16-methylene-17 alpha-acetoxy-19-norprogesterone

16-Methylene-17 alpha-acetoxy-19-norprogesterone (ST-1435) is a new antifertility agent. ST-1435 silastic capsule was implanted sc in the nuchal region of rats on d 6 of gestation at 75, 300, and 600 mg.kg-1. The rats were killed on d 20. In comparison with the control, the treated groups showed no significant differences in maternal body weights, number of corpora lutea, and the development of embryos and fetuses. The number of dead fetuses decreased and live fetuses increased slightly. ST-1435 did not affect the frequency of micronucleated polychromatic erythrocytes, nor induce chromosomal aberrations in cultured CHL cells, or increase the revertants of Salmonella typhimurium TA97, TA98, TA100, and TA102 in Ames test. The results suggested that ST-1435 had neither teratogenicity nor mutagenicity.