Thalidomide: 40 years on.

Thalidomide was marketed in the late-1950s as a sedative and tranquilliser of exceptionally low general toxicity, but in 1961 it was implicated separately by Lenz and MacBride as the cause of the epidemic of congenital malformations that had been puzzling the world for some years. It is a very potent teratogen in humans, but in few other mammalian species; damage to the embryo is produced at specific stages of gestation, but the mechanism of embryopathic action is still not understood. Following the withdrawal of the drug worldwide, it was consigned to the history of medical tragedies. In 1965, however, Sheskin discovered that it was effective in treating erythema nodosum leprosum, a distressing complication of leprosy. As the drug is neither an antibiotic nor an analgesic, its action was assumed to be immunosuppressive. In Brazil the drug was used widely with few regulatory controls, since when more than 100 cases of congenital malformation have appeared. Sheskin's discovery led to the experimental use of thalidomide in many other indications thought to possess some immunological component. In some cases, e.g. Behçet's syndrome, graft-versus-host disease and aphthous ulceration in HIV-positive patients, the drug has been shown to possess some efficacy. And there is some evidence that it inhibits the replication of one of the immunodeficiency viruses. The AIDS community in the US has exerted much pressure on the FDA to allow the drug on to the market, although the use of a potent immunosuppressive drug of unknown mechanism in an immunodeficiency condition raises further questions. Thalidomide is not always beneficial; its use is associated with an increased mortality in epidermal necrolysis. In 1991, D'Amato confirmed it possessed antiangiogenic properties and this led to further trials in malignant conditions. Results were mixed, but those in multiple myeloma gave some grounds for optimism. In 1998, the FDA announced its extraordinary decision to grant marketing approval for thalidomide.