FR-900520 and FR-900523, novel immunosuppressants isolated from a Streptomyces. II. Fermentation, isolation and physico-chemical and biological characteristics.

Abstract

FR-900520 and FR-900523, novel neutral macrolide immunosuppressants, were isolated from the cultured broth of Streptomyces hygroscopicus subsp. yakushimaensis No. 7238. Their molecular formulae were determined as C43H69NO12 and C42H67NO12, respectively. The compounds suppressed immune response in vitro. IC50 values of FR-900520 and FR-900523 for mouse mixed lymphocyte reaction were 0.55 nM and 1.6 nM, respectively. FR-900520, the major component, clearly prolonged skin allograft survival in rats.