A semi-synthetic tetracycline antibiotic; more active than tetracycline against 339 strains of anaerobic bacteria (MIC90s = 1 and 32 μg/ml, respectively); active against tetracycline-resistant E. coli, S. aureus, and E. faecalis strains (MICs = 0.06-1 μg/ml); active against S. aureus in mice (ED50s = 0.46 and 0.6 mg/kg for intravenous and subcutaneous administration, respectively)