Rokitamycin is a macrolide antibiotic against Gram-positive bacteria. Synthesized from strains of Streptomyces kitasatoensis. Rokitamycin is an inhibitor of protein synthesis by specifically binding to the 50 S subunit of the ribosome. Specificity towards prokaryotes relies upon the absence of 50S ribosomes in eukaryotes.

Iclaprim is an investigational broad-spectrum diaminopyrimidine antibiotic in development for the treatment of acute bacterial skin and skin structure infections (ABSSSIs). Iclaprim acts on bacterial cells by competitively inhibiting dihydrofolate reductase (DHFR), a key enzyme in the folate cycle; the same mode of inhibition is exerted by trimethoprim. Iclaprim resistance is mainly determined by point mutations in the dfr gene as studied in S. aureus and S. pneumoniae. Surveillance studies demonstrate that the spectrum of activity of iclaprim includes many organisms indicated in cSSSI including S. aureus and S. pyogenes. Iclaprim is bactericidal in vitro, generally at concentrations equal to the MIC that are maintained in human plasma for several hours after a therapeutic dose. Bactericidal activity is primarily time-dependent and concentration independent. Due to its structural similarity with trimethoprim, iclaprim is synergistic with sulfonamides against a broad spectrum of bacterial species. The antimicrobial mechanism of action of iclaprim is mediated by competitive inhibition of bacterial DHFR, the same mode of inhibition exerted by TMP. The activity of iclaprim against TMP-R mutants of S. aureus and S. pneumoniae is attributable to additional hydrophobic interaction between iclaprim and the enzyme. The same mechanism of action of iclaprim, competitive inhibition with the natural substrate DHF, is seen against both TMP-S and -R enzymes. Iclaprim is well suited for use as a first-line empiric monotherapy in patients with ABSSSI who are comorbid with renal impairment for the following reasons. n July 2015, the U.S. Food and Drug Administration, or FDA, designated the IV formulation of iclaprim as a Qualified Infectious Disease Product (QIDP) for ABSSSI and HABP. QIDP status grants iclaprim regulatory Fast Track designation, Priority Review and, if approved, a five-year extension to the statutory market exclusivity period in the United States, resulting in 10 years of market exclusivity from the date of approval.

Thiocarlide (or tiocarlide or isoxyl) is a drug which was used in the treatment of tuberculosis. In addition was preclinical experiments, which showed, that it purely bacteriostatic against M. leprae. The precise mechanism is still unknown but was shown, that Delta9-desaturase could be a target for it. The more recent experiments have revealed, that Thiocarlide inhibits the dehydration step by the (3R)-hydroxyacyl dehydratases HadAB and HadBC.

Morinamide is a second line anti-tuberculous agent. In vitro morinamide demonstrated clear dose-dependent bacteriostatic and bactericidal activities. The anti-mycobacterial effect of morinamide was the same as pyrazinamide and was dependent on the acidity of medium (pH 5.6). Liver function test abnormalities following morinamide therapy are usually mild, and onset of jaundice is extremely uncommon. It has been given orally as the hydrochloride in the treatment of tuberculosis.

Thiamphenicol is a broad-spectrum antibiotic, which is active against gram-positive and gram-negative organisms. The drug is marketed in Asia and Latin America for the treatment of various infections, including sexually transmitted diseases. As many phenicols, thiamphenicol inhibits the protein synthesis in bacterias by binding to 23S ribosomal subunit. In Europe and USA the drug is used in a veterinary practice.

Cefozopran hydrochloride is a third-generation cephalosporin that was launched for the treatment of severe infections in immunocompromised patients caused by staphylococci and enterococci. While it shows a very broad antibacterial spectrum against Gram-positive and Gram-negative organisms, it is particularly potent against S. aureus, Enterococcus faecalis, P. aeruginosa, and Citrobacter freundii. It is resistant to hydrolysis by most chromosomal and plasmid mediated β-lactamases and is reported to be active against respiratory, urinary tract, obstetrical, gynecological, soft tissue, and surgical infections. Similar to β-lactams, cephalosporins interfere with PBP (penicillin binding protein) activity involved in the final phase of peptidoglycan synthesis. PBP’s are enzymes which catalyze a pentaglycine crosslink between alanine and lysine residues providing additional strength to the cell wall. Without a pentaglycine crosslink, the integrity of the cell wall is severely compromised and ultimately leads to cell lysis and death. Resistance to cephalosporins is commonly due to cells containing plasmid encoded β-lactamases.

Moroxydine is an antiviral drug discovered in the 1950’s which was shown to be active against DNA and RNA viruses. Moroxydine analogues are potent anti-hepatitis C virus (HCV) agents.

TERIZIDONE, a structural analog of cycloserine, is a broad spectrum antibiotic used in the treatment of multidrug-resistant tuberculosis. However, its effectiveness is widely debated. Terizidone acts by inhibiting cell wall synthesis by competitively inhibiting two enzymes, L-alanine racemase and D-alanine ligase, thereby impairing peptidoglycan formation necessary for bacterial cell wall synthesis.

Temocillin was marketed by Beecham Pharmaceuticals in the UK in the 1980s but achieved little commercial success and was withdrawn, though it remained available via the manufacturer’s medical department. Presently licensed to Eumedica, temocillin is being re-launched in the UK and Belgium for treating UTI, sepsis, and respiratory infections by ESBL (Extended-spectrum beta-lactamases) and AmpC-producing Enterobacteriaceae. It acts by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls. It irreversibly binds to the active site of specific transpeptidases and carboxypeptidases known as Penicillin Binding Proteins (PBP), preventing peptidoglycan production.

Metampicillin is the approved name for the penicillin resulting from the reaction of ampicillin with formaldehyde. Metampicillin is hydrolysed in aqueous solution with the formation of ampicillin. Metampicillin has broad spectrum of activity coupled with a marked degree of stability to bacterial penicillinase. Furthermore, metampicillin is reported to be absorbed to a greater extent than ampicillin, resulting in superior blood levels in human subjects, and also giving high levels of antibiotic in bile following parenteral administration. Metampicillin showed a spectrum and level of activity similar to that of ampicillin in vitro, and both compounds were inactive against penicillinase-producing strains of bacteria. The activity of metampicillin was markedly reduced by human serum, and the compound was less active than ampicillin in the presence of human serum. Following the oral administration of metampicillin to man, metampicillin was not detected in the blood stream nor in urine, and ampicillin alone was demonstrated in these subjects. The serum concentrations of ampicillin that were produced following the oral administration of metampicillin were somewhat lower than those obtained with equivalent doses of ampicillin. Adminstration of metampicillin by the intramuscular (i.m.) route to volunteers resulted in the appearance of both ampicillin and metampicillin in the blood, and of ampicillin alone in the urine of these subjects. When parenteraly administered, metampicillin appeared to be a particularly suitable penicillin for the treatment of biliary tract infections. Metampicillin is a cell wall biosynthesis inhibitor.