Rosamaricin is a macrolide antibiotic similar to erythromycin. This compound is more effective against Gram-negative bacteria than erythromycin, especially in the prostate where rosamaricin was shown to be more concentrated than erythromycin in dogs. Rosamaricin has antibiotic activity against Neisseria gonorrhoeae, Chlamydia trachomatis, Ureaplasma urealyticum and Mycoplasma hominis. When the drug was compared with penicillin G in the treatment of pneumococcal meningitis in rabbits it was found to be less effective than penicillin G, as measured by bacterial clearance from cerebrospinal fluid and by treatment outcome. No information on the current use of this compound is available.

Cefuracetime is an impurity of Cefuroxime, which is an antibacterial agent.

Propikacin (also known as UK31214) is kanamycin B derivative patented by Pfizer Inc. as antibacterial compound. In preclinical studies Propikacin shows antibacterial activity against the Enterobacteriaceae, P. stuartii strains and the gentamicin-resistant strains of P. aeruginosa.

Phenyracillin is the 2,5-diphenylpiperazine salt of benzylpenicillin. It is antibiotic from Pencillium spp. and also other fungal spp. Shows activity against gram-positive bacteria. Phenyracillin was well tolerated.

Amifloxacin [WIN 49375] is a fluoroquinolone antibacterial with a broad range of activity against aerobic Gram-negative and some aerobic Gram-positive organisms. Amifloxacin is a DNA gyrase inhibitor. The 50% inhibiory concentration for supercoiling activity of E.coli KL16 DNA gyrase of amifloxacin (MIC, 0.10 ug/ml) was 2.47 ug/ml. Amifloxacin was in trials for the treatment of gram-negative infections, septic shock and urinary tract infections. However, development of amifloxacin has been discontinued.

Fandofloxacin is a difluoroquinolone derivative. This compound possesses an antibacterial spectrum comparable to those of rufloxacin and ciprofloxacin in vivo. Fandofloxacin showed a rapid and nearly complete absorption, and a long residence time in the body. Because it has been reported that the in vivo antibacterial activity of Fandofloxacin is comparable or superior to other quinolones, despite the fact that its in vitro activity is significantly lower than that of the other compounds, the pharmacokinetics of this antibiotic may be responsible, at least in part, for the enhanced in vivo antibacterial activity of Fandofloxacin. Fandofloxacin is an inhibitor of bacterial DNA gyrase. The toxicities and adverse effects of Fandofloxacin observed in various toxicology studies and clinical trials were less than those of commercially available drugs. It has been in phase II clinical trial for the treatment of Urinary tract infections. However, this research has been discontinued in 2008.

FIBRACILLIN is a semisynthetic antibacterial agent.

Faropenem medoxomil is an ester prodrug derivative of the beta-lactam antibiotic faropenem. The prodrug form of faropenem offers dramatically improved oral bioavailability and leads to higher systemic concentrations of the drug. Faropenem medoxomil is a broad-spectrum antibiotic that is highly resistant to beta-lactamase degradation. It was under development for the treatment of acute bacterial sinusitis, community-acquired pneumonia, acute exacerbation of chronic bronchitis, and uncomplicated skin and skin structure infections.

Cethromycin is a ketolide antibiotic derived from erythromycin A being investigated for use in community-acquired pneumonia and other respiratory tract infections. Cethromycin possesses reliable activity against the bacteria most commonly associated with community-acquired pneumonia including S. pneumoniae, H. influenzae, M. catarrhalis, M. pneumoniae, C. pneumoniae, and L. pneumophila. Unlike fluoroquinolones, cethromycin has a narrower spectrum of activity against gram-negative bacteria, which may reduce the risk of collateral damage and the incidence of Clostridium difficile infection. It offers an advantage over telithromycin in that hepatotoxicity does not seem to be a concern. The FDA denied approval of cethromycin for the treatment of CAP in 2009, requesting more efficacy data.