Zoliflodacin (also known as AZD0914 or ETX0914) is a spiropyrimidinetrione with activity against bacterial type II topoisomerases that inhibits DNA biosynthesis and results in accumulation of double-strand cleavages in bacteria. This drug is being a DNA gyrase inhibitor, targeting Neisseria gonorrhoeae and is currently in phase II clinical trial in adults to treat uncomplicated urogenital gonorrhea.

Ionomycin is an ionophore produced by the bacterium Streptomyces conglobatus. The molecules act as a motile Ca2+ carrier and enhances Ca2+ influx by direct stimulation of store-regulated cation entry across biological membranes. It is highly specific for divalent cations. Ion selectivity is as follows: Ca2+ > Mg2+ >> Sr2+ = Ba2+ Binding of Sr2+ and Ba2+ is insignificant and binding to monovalent cations or rubidium is negligible. La2+ is also bound to some extent. Complexation with a cation is always in a 1:1 stoichiometry and pH-dependent. Essentially no binding of Ca2+ occurs below pH 7.0 and maximum binding takes place at pH 9.5. At the micromolar level, ionomycin can activate Ca2+/Calmodulin dependent kinase and phosphatase to stimulate gene expression. Ionomycin has been shown to induce central demyelination, inhibit adrenal bovine TREK-1 channels, and to regulate cell division of mature human B cells [1]. It is used to study the effects of calcium flux on endoplasmic reticulum (ER) stress, mitochodrial stress and intrinsic apoptosis mechanisms. It is also used to stimulate the intracellular production of the cytokines, interferon, perforin, IL-2, and IL-4 usually in conjunction with PMA.

Ridinilazole (SMT19969) is a compound that was developed as a treatment for Clostridium difficile infection, which is a spore-forming bacterial infection and the leading cause of infectious healthcare-associated diarrhea. Ridinilazole has a highly targeted spectrum of activity and can spare the normal gut microbiota. A phase I clinical trial demonstrated that oral ridinilazole is well tolerated. A phase II study showed the potential of ridinilazole in treatment of initial Clostridium difficile infection and showed that this drug can reduce recurrence of the disease. In 2019, recruitment for phase III trials was still ongoing.

Zidebactam (also known as WCK 5107), a beta-lactam enhancer that belongs to the bicyclo-acyl hydrazide series. This drug inhibits the penicillin-binding protein and is participating in phase I clinical trial to treat the bacterial infection.

Q203 (6-chloro-2-ethyl-N-(4-(4-(4-(trifluoromethoxy)phenyl)piperidin-1-yl)benzyl)imidazo [1,2-a]pyridine-3-carboxamide) is an an imidazopyridine antitubercular compound. Q203 targets the cytochrome b subunit (QcrB) of the cytochrome bc1 complex. This complex is an essential component of the respiratory electron transport chain of ATP synthesis. Q203 inhibited the growth of multidrug-resistant (MDR) and extensively drug-resistant (XDR) M. tuberculosis clinical isolates in culture broth medium in the low nanomolar range and was efficacious in a mouse model of tuberculosis at a dose less than 1 mg per kg body weight, which highlights the potency of this compound. In addition, Q203 displays pharmacokinetic and safety profiles compatible with once-daily dosing. Q203 is a promising new clinical candidate for the treatment of tuberculosis.

Lobucavir is a new anti-cytomegalovirus infection agent, manufactered by Bristol Myers Squibb, Inc. Lobucavir is a cyclobutyl analog of guanine with broad spectrum antiviral activity against most herpes viruses and Hepatitis B. Lobucavir was shown to inhibit herpes simplex virus (HSV) DNA polymerase after phosphorylation by the HSV thymidine kinase. The drug was well tolerated with few side effects. Lobucavir had been in phase III clinical trial for the treatment of Hepatitis B, Herpes simplex virus infections and in phase II for the treatment of Cytomegalovirus infections. All these studies were discontinued.

Nifuradene (NF-246), a chemotherapeutic nitrofuran, was first synthesized and reported in 1956. Nifuradene, a 5-Nitorofuran derivative, is an antibacterial drug. Early in vitro testing found it an effective chemotherapeutic agent against most of the common urinary pathogens. Subsequent in vivo studies found that this compound is well absorbed after oral administration in both animals and humans. Nifuradene was used for the treatment of urinary tract infections. The over-all cure rate was found to be best at doses exceeding 600 mg a day.

Premafloxacin is an 8-methoxy fluoroquinolone derivative patented by American pharmaceutical company Warner-Lambert Co. as an antibacterial agent. In preclinical studied. Premafloxacin was equivalent to ciprofloxacin, enrofloxacin, and danofloxacin in activity against the gram-negative bacilli but was much more active than the comparison antimicrobial agents (against the staphylococci, streptococci, and anaerobes. Premafloxacin acts as a topoisomerase IV inhibitor with enhanced activity against Staphylococcus aureus.

Lexithromycin is an early semi-synthetic erythromycin, prepared by reaction of the 9-keto moiety to methyl oxime. Lexithromycin has improved absorption in vivo over erythromycin due to increased hydrophopicity and pH stability. Like all erythromycins, lexithromycin shows broad spectrum antibacterial activity and acts by binding to the 30S and 50S ribosomal sub-units, blocking protein synthesis. Formulations containing lexithromycin were tested in clinical trials as treatment for HIV but were discontinued.

Presatovir is a novel inhibitor of respiratory syncytial virus (RSV) fusion F protein patented by Gilead Sciences, Inc. as an antiviral agent. Upon oral administration of GS-5806, this agent specifically binds to F protein on the viral surface, which inhibits RSV F protein-mediated fusion with the host cell membrane and prevents viral entry. This blocks RSV replication, reduces viral load, and decreases the severity of the disease. Presatovir exhibited potent antiviral activity against 75 RSV clinical isolates from both A and B subgroups in vitro. In vivo, presatovir demonstrated efficient penetration into the lung and epithelial lining fluid in Sprague‐Dawley rats and in dogs and cattle. Presatovir demonstrated dose‐dependent antiviral activity in both the upper respiratory tract and the lungs in a nonclinical study of RSV‐infected cotton rats as well as in a clinical study of healthy adults experimentally infected with RSV.