FR901459, a novel immunosuppressant isolated from Stachybotrys chartarum No. 19392. Taxonomy of the producing organism, fermentation, isolation, physico-chemical properties and biological activities.

FR901459, a novel immunosuppressant, has been isolated from the fermentation broth of Stachybotrys chartarum No. 19392. The molecular formula of FR901459 was determined as C62H111N11O13. FR901459 was found to be a member of the cyclosporin family. However, it is structurally distinct from any other cyclosporins discovered so far, in that Leu is present at position 5 instead of Val. FR901459 was capable of prolonging the survival time of skin allografts in rats with one third the potency of cyclosporin A.