Herbimycin A is an ansamycin antibiotic isolated from Streptomyces sp. Inhibits HSP90 and associated client proteins including v-Src, Bcr-Abl, Raf-1 and ErbB2. Herbimycin A reverts tyrosine kinase-induced oncogenic transformation without direct inhibition of phosphorylation activity. It also inhibits angiogenesis in a rat retinopathy model.