We have investigated the effect of qinghaosu (QHS, artemisinin) and its derivatives on Leishmania major replication in vitro and on the disease development in mice infected with L. major. Artemisinin is effective against promastigotes in vitro, with an ED 50 (50% effective dose) at 7.5 × 10−7 m. Both artemisinin and artemether are leishmanicidal for amastigotes in infected murine macrophages in vitro, with ED50 at 3 × 10−5 m and 3 × 10−6 m respectively. These compounds have no effect on the viability of macrophages or on the phytohaemaglutinin-induced proliferation of normal spleen cells, even at 10−4 m. BALB/c mice infected in the footpad with L. major developed significantly smaller lesions and parasite loads when treated with the compounds. Intra-lesion injection of the compounds was the most effective route. The intramuscular and oral routes were also effective; however, intravenous injection with artesunate was not effective.
