Embryotoxic effects of thalidomide derivatives in the non-human primate Callithrix jacchus. 5. Lack of teratogenic effects of phthalimidophthalmide.

The teratogenic potency of the thalidomide (Thd) derivative phthalimidophthalimide (Phtpht) was assessed in the common marmoset (Callithrix jacchus), by oral administration of the relatively high daily dose of 50 mg Phtpht/kg body wt, during the susceptible period (days 48-61 of pregnancy). Since in this species daily doses of only 100 micrograms/kg body wt of the Thd derivative EM12 already induce typical gross structural abnormalities in nearly 100% of the fetuses, investigations with a small number of these New World monkeys allow a rough estimation of the teratogenic potency of Thd-type substances. Macroscopic inspection and skeletal evaluation of ten fetuses gave no indication of dysmorphogenesis following treatment with Phtpht. We conclude that Phtpht has little, if any, Thd-type teratogenic potency in this non-human primate.