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WCK 4086 is new antibacterial drug being developed to treat infections caused by Gram positive bacteria. This study describes development of mass spectrometry (MS) compatible reversed phase liquid chromatographic method for separation, identification and quantification of the related compounds in WCK 4086. Four process related compounds and seven degradation products (DPs) were separated and structurally identified with the use of liquid chromatography tandem mass spectrometry. Three process-related compounds were synthesized and characterized using MS and nuclear magnetic resonance spectrometry. Acid/base hydrolysis produced three DPs and oxidation produced four DPs. Method validation activity was performed to increase the acceptability of the developed method. The method was precise and accurate; accuracy exceeded 97.04% with a precision of less than 5.55%. The impurities could be detected as low as 0.05 µg mL−1. The methodology was used for the batch release and stability studies of the WCK 4086 used in the preclinical studies.

Nafithromycin is a next generation lactone ketolide antibiotic slated to enter phase III clinical development in India for the treatment of CABP as a shorter 800 mg-OD X3 day therapeutic regimen. N...

Alalevonadifloxacin (ALA, formerly described as WCK 2349) is a novel antibacterial drug developed to treat infections caused by Gram-positive bacteria. The current study was aimed to identify and quantify impurities in ALA. Mass spectrometry (MS) compatible reverse phase liquid chromatographic method was developed to identify the impurities in ALA. Three impurities were identified based on the molecular ion peak and their product ions. These impurities were synthesized and characterized using MS and nuclear magnetic resonance spectrometry. However, this method was unable to resolve the diastereomeric impurity, which is likely to be formed during synthesis. Therefore, another method was developed using YMC Chiral NEA-[S] as a chiral stationary phase and validated for quantification of all impurities including diastereomeric impurity. The developed method was employed for quality control and stability studies of the ALA drug substance used in pre-clinical and clinical studies.

A mass spectrometer compatible, reverse-phase high-performance liquid chromatography method capable to resolve twenty-six impurities and degradation products (DPs) in Ertapenem (ERT) has been developed. Eight dimer impurities (m/z 951) and two dehydrated dimers (m/z 933) were baseline resolved. Out of eight dimers, four dimers are reported the first time. The impurities and DPs were identified using LC–MS/MS. The chromatographic separation was achieved on X-Terra RP 18 (150 × 4.6 mm, 3.5 µm) column using gradient elution. The separation was dependent on the pH of the mobile phase, optimum separation was achieved using the mobile phase of pH 8. Mobile phase-A comprised of a mixture of ammonium formate buffer (pH 8.0), water and acetonitrile in a ratio of 40:60:01; v/v/v. Mobile phase-B comprised of a mixture of ammonium formate buffer (pH 8.0), acetonitrile and methanol in a ratio of 40:50:10; v/v/v. The flow rate was 1.0 mL min−1 and column was maintained at 40 °C. Considering the fragility of ERT and demand of faster analysis method, the method was further transformed on rapid resolution column with a run time of 10 min. The later method also produced the same kind of selectivity with enhanced sensitivity.

WCK 771 (INN: levonadifloxacin) is a novel antibacterial agent belonging to benzoquinolizine subclass of fluoroquinolones which is under clinical development as a parenteral formulation and its pro...

Levonadifloxacin is a parenteral anti-MRSA benzoquinolizine antibacterial drug recently launched as, EMROK in India to treat acute bacterial skin and skin structure infections (ABSSSI) in hospitalized patients. As a step down therapy an oral form of levonadifloxacin with comparable PK/PD was needed because the levonadifloxacin exhibits very poor oral absorption. To improve the drugability in terms of oral absorption a pro-drug approach was evaluated. Structurally levonadifloxacin provides two sites amenable for ester or amide formation, a carboxyl function of benzoquinolizine pharmacophore and hydroxyl group on piperidine side chain. Several aliphatic, aromatic and amino acid esters of C-2 carboxylic acid, C-4-hydroxyl piperidine and double esters at both C-2, C-4 positions were synthesized. The cleavage of prodrugs was studied in vitro as well as in animal models to access their suitability as prodrug function. Among C-2 carboxylic ester prodrugs, daloxate (WCK 2320) showed highest cleavage in serum as well as in liver enzyme; however its stability in aqueous solution was unfavorable. In contrast, most of the esters at the hydroxyl group like propionyl ester (WCK 2305) and amino acid esters such as L-alanine (WCK 2349), L-valine (WCK 2630) were cleaved readily releasing active drug. Thus, indicating C-4-hydroxyl piperidine was amenable site for enzymatic cleavage over esters of C-2 carboxylic acid. Additionally, amino acid esters provided an opportunity to make salt, facilitating improved aqueous solubility. Methanesulfonate salt of L-alanine ester of levonadifloxacin (WCK 2349) was successfully developed and launched as oral prodrug alalevonadifloxacin (EMROK-O).

Zidebactam (ZID) is a novel drug in clinical development; it potentiates the antibacterial activity of β-lactam antibiotics. Two reversed phase liquid chromatographic (RP-LC) methods were developed for ZID; a mass spectrometer (MS) compatible method for identification and another UV detection method for the quantification of impurities. Four impurities and three degradation products (DPs) were identified using LC–MS/MS. Both methods were developed on Hydrosphere C18 stationary phase which was found to be unique for the purpose due to its hydrophilic surface. The chromatographic separation of ZID and impurities was achieved in gradient mode using mobile phase consisting of ammonium formate in LC–MS/MS studies and ammonium dihydrogen phosphate in UV method. Acetonitrile (ACN) was employed as an organic solvent. ZID was subjected to hydrolytic, oxidative, photolytic and thermal stress conditions. The degradation was observed in acidic, basic and oxidative conditions. The UV method was validated. The method was accurate and precise to quantify impurities; accuracy was greater than 99.8% with precision of less than 4%. The method was highly sensitive to detect impurities as low as 1.4 ng on column. The developed method was employed for quality control and stability studies of the new drug substance during pre-clinical and clinical studies. The same method was also adapted for analysis of a parenteral drug product.

Levonadifloxacin and its prodrug alalevonadifloxacin are novel broad-spectrum anti-MRSA agents belonging to the benzoquinolizine subclass of quinolone, formulated for intravenous and oral administration, respectively. Various in vitro and in vivo studies have established their antimicrobial spectrum against clinically significant Gram-positive, Gram-negative, atypical, and anaerobic pathogens. The potent activity of levonadifloxacin against MRSA, quinolone-resistant Staphylococcus aureus, and hetero-vancomycin-intermediate strains is an outcome of its well-differentiated mechanism of action involving preferential targeting to DNA gyrase. Potent anti-staphylococcal activity of levonadifloxacin was also observed in clinically relevant experimental conditions such as acidic pH, the intracellular environment, and biofilms, suggesting that the drug is bestowed with enabling features for the treatment of difficult-to-treat MRSA infections. Levonadifloxacin also retains clinically relevant activity against resistant respiratory pathogens such as macrolide- and penicillin-resistant Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae, and Moraxella catarrhalis and, in conjunction with clinically established best-in-class human epithelial lung fluid concentration, has promising potential in the management of recalcitrant respiratory infections. Attractive features, such as resistance to NorA efflux, divergent mechanism of action in S. aureus, cidality against high-inoculum cultures, and low mutant prevention concentration, are likely to confer favorable resistance-suppression features to both agents. In vivo studies have shown promising efficacy in models of acute bacterial skin and skin structure infection, respiratory infections, pyelonephritis, and peritonitis at human-equivalent mouse doses. Both formulations were well tolerated in multiple phase I studies and overall showed a dose-dependent exposure. In particular, oral alalevonadifloxacin showed excellent bioavailability (~90%), almost mirroring the pharmacokinetic profile of intravenous levonadifloxacin, indicating the prodrug's seamless absorption and efficient cleavage to release the active parent drug. Hepatic impairment studies showed that clinical doses of levonadifloxacin/alalevonadifloxacin are not required to be adjusted for various degrees of hepatic impairment. With the successful completion of phase II and phase III studies for both levonadifloxacin and alalevonadifloxacin, they represent clinically attractive therapeutic options for the treatment of infections caused by multi-drug-resistant Gram-positive organisms. Herein, we review the current evidence on therapeutically appealing attributes of levonadifloxacin and alalevonadifloxacin, which are based on a range of non-clinical in vitro and in vivo investigations and clinical studies.

Zidebactam (ZID), a novel β-lactam enhancer drug being developed to treat infections caused by Gram-negative bacteria, currently is in phase III clinical development. Two ionic impurities observed in liquid chromatography with charged aerosol detector (CAD) analysis were identified through liquid-chromatography mass spectrometry (LC–MS) as sulfate (SO4−2) and monomethyl sulfate (CH3OSO3−1, MMS). There genesis was attributed to the use of pyridine sulfur trioxide as a reagent in ZID synthesis. A new chromatographic method using mixed-mode stationary phase and CAD was developed and validated. The separation of ionic impurities was achieved on Obelisc-N column using buffer gradient. The new method was found to be simple, specific, sensitive, precise, accurate and robust for controlling these impurities in new drug substance. Accuracy of the method was verified by comparing the results with that of ion chromatography (IC) with conductivity detector. The IC method was employed to monitor the impurities in ZID drug substance used for clinical trials and stability analysis.

Ethyl nipecotate enantiomers are widely used as chiral building blocks in the synthesis of drug substances. An efficient and economic chiral high-performance liquid chromatographic method for determination of enantiomeric purity of ethyl nipecotate is developed and validated. Chiral separation was achieved on immobilized amylose-based stationary phase using a mixture of n-hexane: ethanol: diethylamine (80:20:0.1, v/v/v) as mobile phase. Resolution between R-(-)-ethyl nipecotate (REN) and S-(+)-ethyl nipecotate (SEN) peaks was found to be 3.59. The detector response of SEN exhibited an excellent linearity over the concentration range of 4.5–120 μg mL−1. The limit of detection and limit of quantification for SEN were 0.016 and 0.045 μg and REN were 0.015 and 0.043 μg, respectively. The influence of column oven temperatures on chiral retention and separation was studied in the range of 25°C to 50°C; the thermodynamic parameters ΔH°, ΔS° and ΔG° were evaluated from van’t Hoff plots and used to explain the strength of interaction between analyte and stationary phase.

A selective and precise chiral high performance liquid chromatography method for the separation of (R)-5-[1-(4-Nitrobenzylsulfonyloxy)-ethyl]-5-(pyridine-2-yl)-[1, 3, 4]-thiadiazole (RE) has been d...

Nafithromycin (NFT, WCK 4873) is a novel antimicrobial drug being developed to treat infections caused by Gram-positive bacteria. It is a second-generation drug of the lactone ketolide class. A mass spectrometry-compatible reversed-phase liquid chromatographic method was developed to separate and identify the impurities in NFT. Forced degradation (FD) study ensured specificity of the method and revealed the probable degradation products. Seven process impurities and five degradation products were chromatographically resolved and identified based on the protonated molecule peak and product ions. Process impurities were synthesized and characterized for identity and purity. Separation was achieved on the XTerra C18 stationary phase using the binary gradient method. Mobile phase ‘A’ constituted of a mixture of an aqueous solution of ammonium acetate (pH 9.0), acetonitrile and methanol in the ratio of (48:27:25, v/v/v). Mobile phase ‘B’ constituted of an aqueous solution of ammonium acetate (pH 9.0) and acetonitrile in the ratio of (05:95, v/v). The method was validated for accurate and precise quantification of the impurities. The developed method was employed for quality control and stability studies of the NFT drug substance used for pre-clinical and clinical studies.

Alalevonadifloxacin (ALA) is a novel antibacterial drug, recently launched in India to treat infections caused by Gram-positive bacteria. In present work, a chiral high-performance liquid chromatographic method was developed and validated for the quantification of a diastereomeric impurity (DI) in ALA. The separation was achieved on Pirkle type (R,R) Whelk-O1 chiral stationary phase, using ammonium formate buffer and acetonitrile in gradient fashion at a flow rate of 1.5 ml/min. The method was extensively validated for the quantification of DI in ALA. The detector response for DI was linear over the concentration range of 0.24-4.78 μg/ml. Limit of quantitation and limit of detection for DI were 0.24 and 0.07 μg/ml respectively. The mean recovery of the DI was 103.47 ± 5.14%. The impact of column temperature on the chiral separation was evaluated. The method was employed for controlling diastereomeric impurity in the batches of ALA used in preclinical studies.

Multidrug-resistant (MDR) pathogens pose a significant public health threat. A major mechanism of resistance expressed by MDR pathogens is β-lactamase-mediated degradation of β-lactam antibiotics. The diazabicyclooctane (DBO) compounds zidebactam and WCK 5153, recognized as β-lactam "enhancers" due to inhibition of Pseudomonas aeruginosa penicillin-binding protein 2 (PBP2), are also class A and C β-lactamase inhibitors. To structurally probe their mode of PBP2 inhibition as well as investigate why P. aeruginosa PBP2 is less susceptible to inhibition by β-lactam antibiotics compared to the Escherichia coli PBP2, we determined the crystal structure of P. aeruginosa PBP2 in complex with WCK 5153. WCK 5153 forms an inhibitory covalent bond with the catalytic S327 of PBP2. The structure suggests a significant role for the diacylhydrazide moiety of WCK 5153 in interacting with the aspartate in the S-X-N/D PBP motif. Modeling of zidebactam in the active site of PBP2 reveals a similar binding mode. Both DBOs increase the melting temperature of PBP2, affirming their stabilizing interactions. To aid in the design of DBOs that can inhibit multiple PBPs, the ability of three DBOs to interact with P. aeruginosa PBP3 was explored crystallographically. Even though the DBOs show covalent binding to PBP3, they destabilized PBP3. Overall, the studies provide insights into zidebactam and WCK 5153 inhibition of PBP2 compared to their inhibition of PBP3 and the evolutionarily related KPC-2 β-lactamase. These molecular insights into the dual-target DBOs advance our knowledge regarding further DBO optimization efforts to develop novel potent β-lactamase-resistant, non-β-lactam PBP inhibitors.IMPORTANCE Antibiotic resistance is a significant clinical problem. Developing novel antibiotics that overcome known resistance mechanisms is highly desired. Diazabicyclooctane inhibitors such as zidebactam possess this potential as they readily inactivate penicillin-binding proteins, yet cannot be degraded by β-lactamases. In this study, we characterized the inhibition by diazabicyclooctanes of penicillin-binding proteins PBP2 and PBP3 from Pseudomonas aeruginosa using protein crystallography and biophysical analyses. These structures and analyses help define the antibiotic properties of these inhibitors, explain the decreased susceptibility of P. aeruginosa PBP2 to be inhibited by β-lactam antibiotics, and provide insights that could be used for further antibiotic development.

Ketolide antibiotics are known to cause hepatic injury. Nafithromycin, a novel lactone ketolide was therefore assessed for hepatic safety through range of preclinical in vitro (metabolic stability, CYP inhibition/induction assays) and in vivo (mass balance and repeat dose toxicity) studies. Repeat-dose toxicity studies in rat and dog revealed that nafithromycin did not cause adverse hematological, biochemical and histopathological changes suggestive of systemic or hepatobiliary safety concern at exposures 3-8 fold higher than targeted therapeutic exposures. The only histological finding noticed was reversible phospholipidosis, mainly in lung and lymphoid organs but not in liver, indicating lower nafithromycin accumulation in liver. This observation was corroborated with lack of biologically relevant elevation of hepatic enzymes linked to hepatic injury. In vitro studies showed that nafithromycin undergoes moderate CYP3A mediated metabolism. Unlike other ketolides, nafithromycin and its metabolites showed weak inhibition of CYP3A isoform and lacked CYP2D6 inhibition. Due to hydrophilic nature, nafithromycin in addition to hepatic clearance is also eliminated unchanged by kidneys in significant amount, thereby minimizing hepatic burden. Based on the scientifically integrated evidences such as moderate metabolism, weak CYP inhibition, lack of CYP induction, minimal accumulation in liver, nafithromycin showed promising hepatic safety profile suitable for its intended community-based usage.

WCK 2996 is a new molecular entity comprising of two stereoisomers. It possesses potent antibacterial activity active against gram-positive bacteria. This article describes liquid chromatographic m...

A highly stereo-specific liquid chromatographic method was developed and validated for the quantification of enantiomeric impurity (R-enantiomer) in novel oxazolidinone antibacterial agent (WCK 4086), a drug substance. The separation was achieved on Chiralpak AD-H (amylose-based chiral stationary phase) using a mobile phase consisting of n-hexane:2-propanol:methanol:trifluoroacetic acid (80:10:10:0.4, v/v/v/v) at a flow rate of 1.0 mL min-1. Chromatographic resolution between two enantiomers was found to be more than 2.0. Method was extensively validated for the quantification of R-enantiomer in WCK 4086 and proved to be robust. Method was found to be highly specific as all other related impurities were separated from the enantiomers. The calibration curve for R-enantiomer showed an excellent linearity over the concentration range of 1-5 μg mL-1. Limit of quantitation (LOQ) and limit of detection (LOD) for R-enantiomer were 0.009 μg and 0.003 μg, respectively. Average recovery of the R-enantiomer was in the range of 94.55-109.67%. Analytical solutions were found to be stable up to 70 h at room temperature. Developed method was found to be specific, sensitive, precise and accurate for quantitative determination of R-enantiomer in WCK 4086 and useful for controlling the enantiomeric impurity in drug substance used for preclinical studies.

Additional file 2: Supplementary file S2. Auto-SRM optimization data.

Additional file 1: Supplementary file S1. Mass spectrum of Chlorobenzene (IS), MMS, EMS and IMS with putative fragmentaton pathway.

Additional file 3: Supplementary file S3. Calibration curves of MMS, EMS and IMS.

Nafithromycin (WCK 4873), a novel lactone-ketolide, was administered to healthy adult subjects in 2 randomized, double-blind, placebo-controlled, phase 1 studies. In the first-in-human study, single ascending oral doses of nafithromycin (100 to 1,200 mg) were administered to subjects under fasted or fed conditions, with effects of food on bioavailability of nafithromycin studied at the dose levels of 400 and 800 mg. In the second study, multiple ascending oral doses of 600, 800, or 1,000 mg of nafithromycin were administered once daily for 7 days under fed conditions. Nafithromycin was generally well tolerated at all doses. No serious or severe adverse events were observed. The mean maximum plasma concentration (C(max)) ranged from 0.099 to 1.742 mg/liter, and the area under the concentration-time curve from time zero to time t (AUC(0–)(t)) ranged from 0.54 to 22.53 h·mg/liter. Nafithromycin plasma AUC(0–)(t) increased approximately 1.2-fold under fed compared to fasted conditions. In the multiple-dose study, the day 7 nafithromycin C(max) ranged from 1.340 to 2.987 mg/liter and the AUC over the final dosing interval (AUC(0–24)) ranged from 13.48 to 43.46 h·mg/liter. The steady state was achieved after 3 days for the 600-mg and 800-mg-dose cohorts and after 4 days for the 1,000-mg cohort. Under both single- and multiple-dosing regimens, plasma exposure to nafithromycin appeared to increase more than dose proportionally. Nafithromycin showed moderate accumulation on day 7 of dosing. The human pharmacokinetic profile, safety, and tolerability data support further development of nafithromycin. (This study has been registered at ClinicalTrials.gov under registration no. NCT03926962 and NCT03979859.)

Aim: A sensitive method to quantify nafithromycin and its N-desmethyl metabolite in human plasma was necessary for Phase I pharmacokinetic studies. Methodology: A precise and accurate LC–MS/MS bioanalytical method has been developed and validated for the simultaneous quantification of nafithromycin (NFT, WCK 4873) and N-desmethyl metabolite (M1, WCK 4978) in human plasma. Clarithromycin was used as an internal standard. Protein precipitation technique was used as sample preparation approach. The calibration curve was linear (r ≥ 0.99) over the concentration range of 10–5000 ng/ml for NFT and M1. Method was validated as per US FDA guideline. Conclusion: The proposed method was successfully applied for determination of plasma levels of the NFT and M1 during Phase I clinical studies.

A new selective, accurate and precise chiral high-performance liquid chromatography method for the separation of (R)-N-tert-butoxy carbonyl-piperidine-3-carboxylic acid hydrazide (RE) and its enantiomer was developed. RE is a key starting material of novel β-lactam enhancer drug Zidebactam. Chiral resolution of more than 10 was achieved on Chiralpak IA column using mobile phase consisting of n-hexane, ethanol in the ratio of 70:30, v/v. The flow rate of the mobile phase was 1.0 mL min−1 and the column oven temperature was 30°C. Detection was carried out at 225 nm. The developed method was validated as per the International Conference on Harmonization guideline. Limit of detection and limit of quantification of the enantiomeric impurity (S)-N-tert-butoxy carbonyl-piperidine-3-carboxylic acid hydrazide (SE) was 2.5 and 7.5 μg mL−1, respectively. Mean recovery of the SE was 96.83 ± 1.4%. The effect of thermodynamic parameters on the chiral separation was evaluated.

A chiral liquid chromatographic method was developed and validated for the quantification of R-enantiomer impurity (RE) in WCK 3023 (S-enantiomer), a new drug substance. The separation was achieved on Chiralpak IA (amylose-based immobilized chiral stationary phase), using a mobile phase consisting of n-hexane-ethanol-trifluoroacetic acid (70:30:0.2, v/v/v) at a flow rate of 1.0 mL/min. The method was extensively validated for the quantification of RE in WCK 3023 and proved to be robust. For RE the detector response was linear over the concentration range of 0.11-5 μg/mL. The limit of quantitation and limit of detection for RE were 0.11 and 0.04 μg/mL respectively. Average recovery of the RE was in the range of 98.11-99.55%. The developed method was specific, sensitive, precise and accurate for quantitative determination of RE in WCK 3023. The impact of thermodynamic parameters on the chiral separation was evaluated. The method was employed for controlling the enantiomeric impurity in the lots of WCK 3023 used for pre-clinical studies. The method was successfully applied to evaluate the possible conversion of WCK 3023 to RE in rat serum samples during pre-clinical pharmacokinetic studies.

WCK 4282 is a combination product of cefepime (FEP) and tazobactam (TAZ) in a 1:1 ratio currently under development for the treatment of multidrug-resistant Gram-negative bacterial infections. We investigated the effect of renal impairment on the pharmacokinetics (PK) and safety of WCK 4282 in 48 subjects with various degrees of renal function. Subjects were categorized on the basis of their Cockcroft-Gault equation-estimated creatinine clearance (CL(CR)). We enrolled 6 subjects each into those with mild (CL(CR), 60 to

WCK 5222 is a novel β-lactam–β-lactam-enhancer combination of cefepime (FEP) and zidebactam (ZID). ZID is a novel β-lactam enhancer with a dual action of binding to Gram-negative penicillin-binding protein 2 (PBP2) and β-lactamase inhibition. WCK 5222 is being developed as a new therapeutic option for the treatment of complicated multidrug-resistant Gram-negative pathogen infections. We investigated the effect of renal impairment on the pharmacokinetics (PK) and safety of WCK 5222 in 48 subjects based on Cockcroft-Gault-estimated creatinine clearance (CL(CR)). We enrolled mild (n = 6; CL(CR), 60 to

WCK 5222 is a combination of cefepime and the novel β-lactam enhancer zidebactam being developed for the treatment of serious Gram-negative bacterial infections. The objective of this study was to compare plasma (total), epithelial lining fluid (ELF), and alveolar macrophage (AM) concentrations of cefepime and zidebactam in healthy adult subjects. The WCK 5222 dosing regimen was 2 g cefepime/1 g zidebactam administered as a 1-h intravenous infusion every 8 h for a total of 7 doses. Subjects were assigned to one bronchoalveolar lavage (BAL) sampling time at 0.5, 1.25, 3, 6, 8, or 10 h after the seventh dose. Noncompartmental pharmacokinetic parameters were determined from serial plasma concentrations collected over 8-hour and 10-hour intervals following the first and seventh doses, respectively. Penetration ratios were calculated from the area under the plasma concentration-time curve from 0 to 8 h (AUC0-8) for plasma, ELF, and AM using mean and median concentrations at each BAL sampling time. The plasma maximum concentration of drug (Cmax) and AUC values of cefepime and zidebactam increased by 8% to 9% after the seventh versus the first dose of WCK 5222. The respective AUC0-8 values based on mean concentrations of cefepime and zidebactam in ELF were 127.9 and 52.0 mg · h/liter, and 87.9 and 13.2 mg · h/liter in AM. The ELF to total plasma penetration ratios of cefepime and zidebactam based on mean AUC0-8 values were 0.39 and 0.38, respectively. The AM to total plasma ratios were 0.27 and 0.10, respectively. The observed plasma, ELF, and AM concentrations of cefepime and zidebactam support studies of WCK 5222 for treatment of pneumonia caused by susceptible pathogens.

Limited treatment options exist to combat infections caused by multidrug-resistant (MDR) Gram-negative bacteria possessing broad-spectrum β-lactamases. The design of novel β-lactamase inhibitors is of paramount importance. Here, three novel diazabicyclooctanes (DBOs), WCK 5153, zidebactam (WCK 5107), and WCK 4234 (compounds 1–3, respectively), were synthesized and biochemically characterized against clinically important bacteria. Compound 3 inhibited class A, C, and D β-lactamases with unprecedented k(2)/K values against OXA carbapenemases. Compounds 1 and 2 acylated class A and C β-lactamses rapidly but not the tested OXAs. Compounds 1–3 formed highly stable acyl-complexes as demonstrated by mass spectrometry. Crystallography revealed that 1–3 complexed with KPC-2 adopted a “chair conformation” with the sulfate occupying the carboxylate binding region. The cefepime-2 and meropenem-3 combinations were effective in murine peritonitis and neutropenic lung infection models caused by MDR Acinetobacter baumannii. Compounds 1–3 are novel β-lactamase inhibitors that demonstate potent cross-class inhibition, and clinical studies targeting MDR infections are warranted.

Alalevonadifloxacin (WCK 2349) is a novel l -alanine ester prodrug of levonadifloxacin that is being developed as an oral fluoroquinolone antibiotic. The primary objective of this study was to determine and compare plasma, epithelial lining fluid (ELF), and alveolar macrophage (AM) concentrations of levonadifloxacin following oral administration of alalevonadifloxacin to healthy adult subjects. Levonadifloxacin concentrations in plasma, ELF, and AM samples from 30 healthy subjects were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) following oral dosing of alalevonadifloxacin (1,000 mg twice daily for 5 days). Six subjects were assigned to each bronchoalveolar lavage (BAL) fluid sampling time, i.e., 2, 4, 6, 8, or 12 h after the ninth oral dose. Noncompartmental pharmacokinetic (PK) parameters were determined from serial total plasma concentrations collected over a 12-h interval following the first and ninth oral doses. Penetration ratios were calculated from the areas under the concentration-time curves from 0 to 12 h (AUC 0–12 ) for plasma, ELF, and AM by using mean (and median) concentrations at each BAL sampling time. Unbound plasma concentrations (∼85% plasma protein binding) were used to determine site-to-plasma penetration ratios. Plasma PK parameter values for levonadifloxacin were similar after the first and ninth doses. The respective AUC 0–12 values based on mean ELF and AM concentrations were 172.6 and 35.3 mg · h/liter, respectively. The penetration ratios for ELF and AM levonadifloxacin concentrations to unbound plasma levonadifloxacin concentrations were 7.66 and 1.58, respectively. Similar penetration ratios were observed with median concentrations. The observed plasma, ELF, and AM concentrations of levonadifloxacin support further studies of alalevonadifloxacin for treatment of lower respiratory tract bacterial infections caused by susceptible pathogens. (This study has been registered at ClinicalTrials.gov under identifier NCT02253342.)

A precise and accurate liquid chromatography-tandem mass spectrometric (LC-MS/MS) bioanalytical method has been developed and validated for the simultaneous quantification of zidebactam (ZID) and cefepime (FEP) in dog plasma. Ceftazidime was used as an internal standard. Protein precipitation method was used as sample preparation approach. The calibration curve obtained was linear (r ≥ 0.99) over the concentration range 0.156-80 μg/mL for ZID and 0.312-160 μg/mL for FEP. The method was validated as per US Food and Drug Administration guidelines and the results met the acceptance criteria. A run time of 3.5 min for each sample made it possible to analyze the maximum number of samples per day. The proposed method was successfully applied for pharmacokinetic study in beagle dogs.

WCK 771 is an l-arginine salt of levonadifloxacin (LND) being developed in intravenous dosage form and has recently completed a phase III trial in India. The pharmacokinetics of WCK 771, a novel anti-MRSA fluoroquinolone, were examined in mice, rats, rabbits, dogs, monkeys and humans after systemic administration during pre-clinical and clinical investigations. Urine and serum were evaluated for identification of metabolites. It was observed that LND mainly follows phase II biotransformation pathways. All of the species showed a different array of metabolites. In mice, rabbit and dog, the drug was mainly excreted in the form of O-glucuronide (M7) and acyl glucuronide (M8) conjugates, whereas in rat and human major metabolite was sulfate conjugate (M6). Monkeys exhibited equal distribution of sulfate (M6) and glucuronide conjugates (M7, M8). In addition to these three major phase II metabolites; five phase I oxidative metabolites (M1, M2, M3, M4 and M5) were identified using liquid chromatography tandem mass spectrometry. Out of these eight metabolites M2, M3, M5, M7 and M8 are reported for the first time.

A simple, rapid, isocratic, normal phase chiral HPLC method was developed and validated for the enantiomeric separation of repaglinide, (S)-(+)-2-ethoxy-4-N [1-(2-piperidinophenyl)-3-methyl-1-butyl] aminocarbonylmethyl] benzoic acid, an antidiabetic drug substance. The enantiomers of repaglinide were resolved on a Chiralpak IA (immobilized amylose based stationary phase) column using a mobile phase consisting of n-hexane:ethanol:trifluoroacetic acid (80:20:0.2, v/v/v) at a flow rate of 1.0 mL min-1. The resolution between both enantiomers was greater than 2 in the optimized method. The developed method was extensively validated and proved to be robust, enantioselective, accurate, precise, and suitable for quantitative determination of (R)-enantiomer in bulk drug substance and product.

A simple and precise stability-indicating liquid chromatography method is developed and validated for the quantitative simultaneous estimation of irbesartan (IRB) and hydrochlorothiazide (HCTZ) in combined pharmaceutical dosage form. A chromatographic separation of the two drugs was achieved with an Ace5 C(18) 25-cm analytical column using buffer-acetonitrile (70:30 v/v). The buffer used in mobile phase contains 50 mM ammonium acetate pH adjusted 5.5 with acetic acid. The instrumental settings are flow rate of 1.5 mL/min, column temperature at 30 degrees C, and detector wavelength of 235 nm using a photodiode array detector. IRB, HCTZ, and their combination drug products were exposed to thermal, photolytic, hydrolytic, and oxidative stress conditions, and the stressed samples were analyzed by the proposed method. Peak homogeneity data of IRB and HCTZ is obtained using photodiode array detector. In the stressed sample chromatograms, it demonstrated the specificity of the assay method for their estimation in presence of degradation products. The described method shows excellent linearity over a range of 10-200 microg/mL for IRB and 5-100 microg/mL for HCTZ. Methylparaben was used as internal standard. The correlation coefficient for IRB and HCTZ are 0.998 and 0.999. The mean recovery values for IRB and HCTZ ranged from 100.45% to 101.25%. The limit of detection for IRB and HCTZ were 0.019 and 0.023 microg/mL, respectively, and the limit of quantification were 0.053 and 0.070 microg/mL, respectively. The proposed method was suitable for quantitative determination and stability study of IRB and HCTZ in pharmaceutical preparations and also can be used in the quality control of bulk manufacturing and pharmaceutical dosage forms.

Summary A novel stability-indicating reversed-phase (RP) HPLC method has been developed and validated for quantitative analysis of eplerenone in the bulk drug and in a pharmaceutical dosage form. Use of a 250 mm × 4.6 mm, 5-μm particle, C18 column with 55:45 (v/v) 50 mM ammonium acetate buffer (pH 7)-acetonitrile as isocratic mobile phase enabled separation of the drug from its degradation products. UV detection was performed at 240 nm. The method was validated for linearity, accuracy (recovery), precision, specificity, and robustness. The linearity of the method was excellent over the range 10–100 μg mL−1 (correlation coefficient 0.999). The limits of detection and quantification were 0.019 and 0.053 μg mL−1, respectively. Recovery of eplerenone from the pharmaceutical dosage form ranged from 100.97 to 101.25%. Eplerenone was subjected to stress conditions (hydrolysis (acid, base), oxidation, photolysis, and thermal degradation) and the stressed samples were analysed by use of the method. Degradation was...

A novel stability-indicating LC assay method was developed and validated for quantitative determination of olmesartan in bulk drugs and in pharmaceutical dosage form in the presence of degradation products generated from forced degradation studies. An isocratic, reversed phase LC method was developed to separate the drug from the degradation products, using an Ace5-C18 (250 mm × 4.6 mm, 5 μm) column, and 50 mM ammonium acetate (pH-5.5 by acetic acid) and acetonitrile (70:30 v/v) as a mobile phase. The detection was carried out at the wavelength of 235 nm. The olmesartan was subjected to stress conditions of hydrolysis (acid, base), oxidation, photolysis and thermal degradation. Degradation was observed for olmesartan in acid, base and in 30% H2O2 conditions. The drug was found to be stable in the other stress conditions attempted. The degradation products were well resolved from the main peak. The percentage recovery of olmesartan ranged from (99.89 to 100.95%) in pharmaceutical dosage form. The developed method was validated with respect to linearity, accuracy (recovery), precision, specificity and robustness. The forced degradation studies prove the stability-indicating power of the method.

A novel stability-indicating high-performance liquid chromatographic assay method was developed and validated for quantitative determination of nitazoxanide in bulk drugs and in pharmaceutical dosage form in the presence of degradation products generated from forced decomposition studies. An isocratic, reversed phase LC method was developed to separate the drug from the degradation products, using an Ace5- C18 (250 mm × 4.6 mm, 5 μm) column, and 50 mM ammonium acetate (pH 5.5 by acetic acid) and acetonitrile (55:45 v/v) as a mobile phase. The detection was carried out at a wavelength of 240 nm. The nitazoxanide was subjected to stress conditions of hydrolysis (acid, base), oxidation, photolysis and thermal degradation. Degradation was observed for nitazoxanide in base, acid and in 30% H2O2 conditions. The drug was found to be stable in the other stress conditions attempted. The degradation products were well resolved from the main peak. The percentage recovery of nitazoxanide was from (100.55 to 101.25%) in the pharmaceutical dosage form. The developed method was validated with respect to linearity, accuracy (recovery), precision, system suitability, specificity and robustness. The forced degradation studies prove the stability indicating power of the method.

A simple, rapid, specific, precise, accurate and sensitive method for determination of WCK 771 in human serum has been developed. The method uses high performance liquid chromatography with tandem mass spectrometric detection. Sample preparation involves protein precipitation method by addition of acetonitrile. Gatifloxacin was used as internal standard. The response was found to be linear from 0.312 to 40 microg/ml of serum with correlation coefficient greater than 0.99. Limit of detection and lower limit of quantification for WCK 771 was found to be 0.078 microg/ml and 0.312 microg/ml, respectively. The intra-day precision and accuracy from analysis of quality control (QC) samples at four concentrations was in the range of 2.36-2.58% and from 96.71 to 103.2%, respectively. The inter-day precision and accuracy from analysis of quality control samples at four concentrations was in the range of 3.14-6.82% and from 96.84 to 105.76%, respectively. WCK 771 was found to be stable for 24 h at auto-injector environment. WCK 771 was also found to be stable for 2h in serum at 25+/-3 degrees C and for 3 months at -20 degrees C. Mean absolute recovery at four different concentrations was 86.92% with standard deviation of 1.79. Throughput of the method is approximately one sample every 4 min. The method was also reproduced with monkey serum. The method was employed for estimation of drug serum levels during pre-clinical and clinical trials.

A sensitive, simple, specific, precise, accurate and rugged method for the assay and determination of enantiomeric purity of S -(−)-9-fluoro-6,7-dihydro-8-(4-hydroxypiperidin-1-yl)-5-methyl-1-oxo-1H,5H-benzo[i,j]quinolizine-2-carboxylic acid l -arginine salt tetrahydrate (WCK 771) in bulk drug has been developed. The method is RP-HPLC using endcapped C-18 stationary phase and chiral mobile phase. Chirality to the mobile phase was imparted with addition of β-cyclodextrin. The UV–vis detector was operated at 290 nm. The flow rate of mobile phase was 2 ml/min. The method offers excellent separation of two enantiomers with resolution more than 2 and tailing factor less than 1.5. The method was validated for the assay of WCK 771 and quantification of R -(+)-enantiomer impurity in bulk drug. The calibration curves showed excellent linearity over the concentration range of 0.05–0.15 mg/ml for WCK 771 and 0.5–7.5 μg/ml for R -(+)-enantiomer. The precision (RSD) of the assay was 0.23%. The limit of detection and limit of quantitation of the method for WCK 771 were 0.015 and 0.06 μg/ml, respectively. The limit of detection and limit of quantitation for R -(+)-enantiomer were 0.025 and 0.09 μg/ml, respectively. The average recovery of the R -(+)-enantiomer was 100.5%. Same method was applied for the assay and determination of enantiomeric purity of WCK 771 in the intravenous formulation.

A simple, rapid and robust LC method was developed and validated for the enantiomeric separation of metolazone. The enantiomers of metolazone were resolved on a Chiralpak AD-H (amylose based stationary phase) column using a mobile phase consisting of Hexane: 2-propanol: Methanol: Acetic acid (80:10:10:0.2, v/v) at a flow rate of 1.0 mLmin-1. The resolution between the enantiomers was found to be not less than 3.0 in optimized method. The presence of acetic acid in the mobile phase played an important role, in enhancing chromatographic efficiency and resolution between the enantiomers. The developed method was extensively validated and proved to be robust. The calibration curve for enantiomers showed excellent linearity over the concentration range of 5 μgmL-1 to 50 μgmL-1. The limit of detection and limit of quantification for enantiomers were 0.05 and 0.16 μgmL-1, respectively. The proposed method was found to be suitable and accurate for quantitative determination of enantiomers in bulk drug substance.

A simple, rapid and robust LC method was developed and validated for the enantiomeric separation of dexrabeprazole in bulk drug and formulation. The enantiomers of dexrabeprazole were resolved on a Chiralpak AD-RH (amylose based stationary phase) column using a mobile phase consisting of water: acetonitrile (50:50, v/v) at a flow rate of 0.5 ml min -1. The resolution between the enantiomers was found to be more than 1.5 in optimized method. The developed method was extensively validated and proved to be robust. The calibration curve for (S)-enantiomer showed excellent linearity over the concentration range of 0.05 µg ml-1 (LOQ) to 1 µg ml-1. The limit of detection and limit of quantification for (S)-enantiomer were 0.015 µg ml -1 and 0.05 µg ml-1, respectively. The percentage recovery of the (S)-enantiomer ranged between 97 to 101 % in bulk drug samples of dexrabeprazole. The proposed method was found to be suitable and accurate for quantitative determination of (S)-enantiomer in bulk drug substance.

A simple, rapid, and precise method is developed for the quantitative simultaneous estimation of amlodipine (AM) and olmesartan (OL) in combined pharmaceutical dosage form. A chromatographic separation of the two drugs was achieved with an ACE 5 C(18) 25-cm analytical column using buffer-acetonitrile (60:40, v/v). The resolution between OL and AM was found to be more than 12. Theoretical plates for OL and AM were 6970 and 11,841, respectively. Tailing factor for OL and AM was 0.90 and 0.98, respectively. OL, AM, and combination drug product were exposed to thermal, photolytic, hydrolytic, and oxidative stress conditions, and the stressed samples were analyzed by the proposed method. Peak homogeneity data of OL and AM is obtained by photodiode array detector in the stressed sample chromatograms, demonstrating the specificity of the method for their estimation in presence of degradation product. The described method shows excellent linearity over a range of 20-400 microg/mL for OL and 5-100 microg/mL for AM. The correlation coefficient for OL and AM are 0.9995 and 0.9998, respectively. The relative standard deviation for six measurements in two sets of each drug in tablets is always less than 2%. The proposed method was found to be suitable and accurate for quantitative determination and stability study of OL and AM in pharmaceutical preparations.

There is an urgent medical need for novel antibacterial agents to treat hospital infections, specially those caused by multidrug-resistant Gram-positive pathogens. The need may also be fulfilled by either exploring antibacterial agents having new mechanism of action or expanding known classes of antibacterial drugs. The paper describes a new chemical entity, compound 21, derived from hitherto little known "floxacin". The choice of the entity was made from a series of synthesized prodrugs and salts of the active chiral benzoquinolizine carboxylic acid, S-(-)-nadifloxacin. The chemistry, physicochemical characteristics, and essential bioprofile of 21 qualifies it for serious consideration as a novel drug entity against hospital infections of multi-drug-resistant Staphylococcus aureus, and its progress up to clinical phase I trials in humans is described.