FR901483, a Novel Immunosuppressant Isolated from Cladobotryum sp. No. 11231

Taxonomy of the Producing Organism, Fermentation, Isolation, Physico-chemical Properties and Biological Activities

Abstract

FR901483, a novel immunosuppressant, has been isolated from the fermentation broth of Cladobotryum sp. No. 11231. The molecular formula of FR901483 has been determined as C₂₀H₃₁N₂O₆P. FR901483 exerts a potent immunosuppressive activity in vitro and significantly prolongs graft survival time in the rat skin allograft model. This compound has an intriguing tricyclic structure possessing a phosphate ester in its molecule. The ester residue may play an important role in exerting immunosuppressive activity because the desphosphoryl compound is devoid of activity. It is thought that the primary target of immunosuppression by this compound is inhibition of purine nucleotide biosynthesis.