Purity >99%. Reveromycin A is the major component of a complex of spiroketal antibiotics isolated from Streptomyces sp. It inhibits the mitogenic activity of epidermal growth factor in Balb/MK cells (IC50 = 0.7 μg/ml), displays antiproliferative activity against human KB and K562 tumor cell lines (IC50 s = 1.9 and 1.6 μg/ml, respectively), and demonstrates antifungal activity against C. albicans (MIC = 2 μg/ml at pH 3). Reveromycin A also has been shown to inhibit bone resorption by inducing apoptosis in osteoclasts with an IC50 value of 0.7 μM.