Antibiotic DC 81 (DC 81), an antitumor antibiotic produced by Streptomyces species, is a PBD (pyrrolo[2,1-c][1,4]benzodiazepine). Antibiotic DC 81 is potent inhibitor of nucleic acid synthesis. Antibiotic DC 81 can recognize and bind to specific sequences of DNA and form a labile covalent adduct.