Ascomycin (FK 520, FR900520) is a novel neutral macrolide immunosuppressant, isolated from the cultured broth of Streptomyces hygroscopicus subsp. yakushimaensis No. 7238.
In vitro: Ascomycin (FK 520, FR900520) suppressed lymphocyte reaction in a dose dependent fashion. Ascomycin was non-toxic at concentrations less than 3,200 nM, at which the percent inhibition was 18.9%. Ascomycin showed antifungal activity against Aspergillus fumigatus IFO 5840. Ascomycin had no inhibitory effect on bacteria or yeast at 100 μg/ml [1].
In vivo: Ascomycin was dose-dependently effective and clearly prolonged skin allograft survival at 3.2 mg/kg or more, though all skin allografts were rejected within 7 days in rats treated intramuscularly with olive oil. Ascomycin, dissolved in olive oil, showed no adverse effect when administered intraperitoneally to ddY mice (male, 8 weeks old) at 100 mg/kg [1].
Clinical trial: Ascomycin macrolactam derivative, Pimecrolimus, had been tested in both adults and pediatric patients with Atopic Dermatitis in two seperate clinical trials.
Reference:
[1] Hatanaka H, Kino T, Miyata S, Inamura N, Kuroda A, Goto T, Tanaka H, Okuhara M. FR-900520 and FR-900523, novel immunosuppressants isolated from a Streptomyces. II. Fermentation, isolation and physico-chemical and biological characteristics. J Antibiot (Tokyo). 1988;41(11):1592-601.