Fomidacillin (also known as BRL 36650) is a type of penicillin with antibacterial activity. Studies on volunteers have shown that the drug possessed the bactericidal activity and could be a candidate for the treatment of gram-negative bacillary infections. However, information about the further development of this drug is not available.

Cetocycline (formerly chelocardin or cetotetrine) is tetracycline derivative with potent antibacterial activity against a number of Gram-positive and Gram-negative multi-resistant pathogens. Cetocycline was found to be more active than tetracycline against many clinical isolates of aerobic gram-negative bacilli, but is less active against staphylococci, and has no activity against Pseudomonas. At low concentrations, like classical tetracyclines, chelocardin induces the proteomic signature for peptidyl transferase inhibition demonstrating that protein biosynthesis inhibition is the dominant physiological challenge. At higher concentrations B. subtilis mainly responds to membrane stress indicating that at clinically relevant concentrations the membrane is the main antibiotic target of chelocardin.

Difloxacin is an aryl fluoroquinolone derivative. The primary bacterial target of fluoroquinolones is the enzyme deoxyribonucleic acid gyrase. Difloxacin is very potent against a broad spectrum of bacteria including aerobic ana anaerobic gram-positive and gram-negative oragnisms. DICURAL® (difloxacin hydrochloride) TABLETS are indicated for the management of diseases in dogs associated with bacteria susceptible to difloxacin.

Furbucillin is a synthetic antibacterial agent that has never been marketed. Information about the current use of this drug is not available.

Binfloxacin is a topoisomerase inhibitor that was studied as an antibacterial agent.

Terdecamycin, an antibiotic that was studied on the pigs to treat dysentery. Information about the current use of this drug is not available.

Ecenofloxacin (CFC-222), a fluoroquinolone, is a broad-spectrum antibacterial compound acting as a ype II DNA topoisomerase inhibitor. It exerts antibacterial activities against gram-positive, gram-negative, and anaerobic organisms. Ecenofloxacin development as an antibacterial agent has been discontinued.

Prazocillin is 6-aminopenicillanic acid derivative patented by Chinoin Gyogyszer es Vegyeszeti Termekek Gyara Rt. as a bactericidal compound. The activity of Prazocillin against Staphylococcus aureus strains was the same as that of dikloxacillin, but Prazocillin was more active against Bacillus subtilis ATCC 6633. Prazocillin had a bactericidal effect on a penicillin-resistant S. aureus strain at concentrations of 1 μg/ml. Pyrazocillin inhibits bacterial penicillinase in vitro.

Tomopenem (formerly CS-023) is a 1β-methylcarbapenem with improved activity against diverse hospital pathogens, including Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA), and has a half-life about twice longer than the half-lives of other carbapenems such as imipenem (IPM) and meropenem (MEM). In vitro activity of tomopenem is comparable to that of IPM against most isolates of Gram-positive pathogens and similar to that of MEM against Gram-negative pathogens. Furthermore, tomopenem displayed improved activity against not only P. aeruginosa but also MRSA compared to IPM and MEM. In addition to the improved activity, tomopenem showed a half-life about twice longer than that of IPM or MEM in humans. The affinity of tomopenem for penicillin-binding protein (PBP) 2a might be higher than that of IPM. Tomopenem had been in phase II clinical trial for the treatment of Gram-positive and Gram-negative bacterial infection. However, this development was discontinued.