Traditional medicinal uses were known for many years--e.g. used in Africa to treat diabetes.
Dr. Noble in Toronto was testing it against diabetes and found it arrested blood cancers. Developed by Eli Lilly company.
Has since become an important treatment against childhood leukemias, Hodgkin's disease, testicular cancer, breast cancer, etc.. Has "vincristine" which binds to tubulin, thus preventing cells from making spindles, so stops cell division. Also seems to interfere with cell's ability to synthesize DNA and RNA. Sale of drugs in 1980 topped $50 million prior to a 100% mark-up. None of which went to Madagascar.