Semisynthetic derivative of rifamycin SV which is produced from certain strains of Amycolatopsis mediterranei. Belongs to the group of ansamycin antibiotics. Inhibitor of DNA-dependent RNA-polymerase. Specifically inhibits the initiation step of RNA synthesis. Semisynthetic derivative of rifamycin SV which is produced from certain strains of Amycolatopsis mediterranei. Belongs to the group of ansamycin antibiotics. Inhibitor of DNA-dependent RNA-polymerase. Specifically inhibits the initiation step of RNA synthesis.