Leptomycin B

An antifungal antibiotic, found to be a potent antitumor agent. It is suggested that the antitumor effect is related to cytochrome c release, activation of caspases, and selective down-regulation ofMc1-1 and XIAP. Leptomycin B has also been found to inactivate the export receptor CRM1. The effect of LepB on the CRM1 (exportin 1) NES receptor results from selective alkylation by LepB of a single cysteine residue. It inhibits the nucleo-cytoplasmic translocation of the HIV Rev protein. LepB has potent antitumor activity in vitro and in vivo, and potent antimycotic and antibiotic activity.Leptomycin B is suplied in serum bottles with teflon-lined closures at 50 µM concentration in ethanol (27 µg/ml). WARNING:  Small quantities of LepB are reported to be unstable when dried down into a film.  Thus, under no circumstances should the solvent be removed from solutions of LepB, because rapid decomposition may result.