The present invention provides a novel bioactive substance having an antitumor activity and a process for producing it, and a medical use thereof. Namely, it provides a 12-membered ring macrolide compound represented by the following formula obtained from the incubation solution of Streptomyces sp. Mer. 11107 or a variant thereof, a pharmacologically acceptable salt thereof or a hydrate of them, and a process for producing it.
