A macrolide antibiotic isolated from Streptomyces sp. An antiangiogenic (IC₅₀ = 0.8 nM) agent. Bacterial and eukaryal threonyl-tRNA synthetase (THrRS) inhibitor. Induces the collapse of formed capillary tubes in a dose-dependent fashion. In HUVECs, the capillary tube collapsing activity is mediated by the activation of caspases-3 and -8 and induction of apoptosis. Also acts as a CDK inhibitor.