Kazusamycin B is a minor component of the leptomycin complex produced by some Streptomyces sp.. It is an hydroxylated analogue of leptomycin A, a nuclear export inhibitor. Kazusamycin B displays potent antitumour activity against L1210 and human colon adenocarcinoma, and in vivo activity against P388 lymphocytic leukemia in mice. Kazusamycin B also possesses strong antibacterial and antifungal activity.
