Assessment of the in vitro and in vivo genotoxicity of Thalomid (R) (Thalidomide)

Thalomid(R) is the FDA-approved commercial formulation of thalidomide curre ntly used in the US to treat erythema nodosum leprosum, a complication of l eprosy. The genotoxicity of Thalomid(R) thalidomide was assessed in the Ame s reverse mutation, sen AS52/XPRT mammalian cell forward gene mutation, and mouse bone marrow micronucleus assays. The Ames and AS52 assays were perfo rmed with and without S9. In the Ames, Salmonella typhimurium strains TA153 5, 1537, 98, 100, and 102 and Escherichia coli strain WP2 uvrA were used. A ssays were performed by using plate incorporation and liquid pre-incubation systems at thalidomide doses of 50-10,000 mu g/plate. In the AS52 assay, C hinese hamster ovary cells were plated with fortified Ham's F12 medium and incubated overnight. The medium was then incubated with 1-1000 mu g/ml thal idomide. After a series of aspirations, washings, reconstitutions, and incu bations, mutant AS52 cells were fixed and stained. Colonies were then count ed and the relative survival frequencies compared to negative controls. In the mouse micronucleus assay, Cr1:CD-1 albino mice were dosed with 500, 2,5 00, and 5,000 mg/kg thalidomide and sacrificed over 72 h. Femurs were flush ed with fetal bovine serum and the suspensions centrifuged. The supernatant was aspirated and the cell pellet resuspended and stained. Polychromatic e rythrocytes were scored for micronucleated polychromatic and normochromatic erythrocytes. Thalidomide did not increase revertant frequencies in all ba cterial strains. It also did not produce any significant increase in the av erage mutant frequencies of AS52 cells and mouse micronucleated polychromat ic erythrocytes. We conclude that Celgene's Thalomid(R) thalidomide is non- genotoxic. Teratogenesis Carcinog. Mutagen. 20:301-311, 2000. (C) 2000 Wile y-Liss, Inc.