In Vitro and In Vivo Characterization of Tebipenem, an Oral Carbapenem

The interaction of the azetidine thiazole side chain with the active site loop (ASL) 3 drives the evolution of IMP metallo-β-lactamase against tebipenem

Imipenemase (IMP) metallo-β-lactamases (MBLs) hydrolyze almost all available β-lactams including carbapenems and are not inhibited by any commercially available β-lactamase inhibitor. Tebipenem (TP) pivoxil is the first orally available carbapenem and possesses a unique bicyclic azetidine thiazole moiety located at the R2 position. TP has potent in vitro activity against Enterobacterales producing extended-spectrum and/or AmpC β-lactamases. Thus far, the activity of TP against IMP-producing strains is understudied. To address this knowledge gap, we explored the structure activity relationships of IMP MBLs by investigating whether IMP-6, IMP-10, IMP-25, and IMP-78 [MBLs with expanded hydrolytic activity against meropenem (MEM)] would demonstrate enhanced activity against TP. Most of the Escherichia coli DH10B strains expressing IMP-1 variants displayed a ≥twofold MIC difference between TP and MEM, while those expressing VIM or NDM variants demonstrated comparable MICs. Catalytic efficiency (kcat/KM) values for the TP hydrolysis by IMP-1, IMP-6, IMP-10, IMP-25, and IMP-78 were significantly lower than those obtained for MEM. Molecular dynamic simulations reveal that V67F and S262G substitutions (found in IMP-78) reposition active site loop 3, ASL-3, to better accommodate the bicyclic azetidine thiazole side chain, allowing microbiological/catalytic activity to approach that of comparison MBLs used in this study. These findings suggest that modifying the R2 side chain of carbapenems can significantly impact hydrolytic stability. Furthermore, changes in conformational dynamics due to single amino acid substitutions should be used to inform drug design of novel carbapenems.

Effect of tebipenem pivoxil hydrobromide on the normal gut microbiota of a healthy adult population in Sweden: a randomised controlled trial

BACKGROUND

Antimicrobials cause perturbations in the composition and diversity of the host microbiome. We aimed to compare gut microbiome perturbations caused by oral tebipenem pivoxil hydrobromide (a novel carbapenem) and by amoxicillin-clavulanic acid (an orally administered β-lactam-β-lactam inhibitor combination widely used in clinical practice).

METHODS

We did a phase 1, single-centre, randomised, parallel-group, active-control trial to evaluate the effect of tebipenem pivoxil hydrobromide on the human gut microbiota. Healthy participants aged 18 years or older with no documented illnesses during recruitment were enrolled at Karolinska University Hospital (Stockholm, Sweden). Study participants were stratified by sex and block-randomised in a 1:1 ratio to treatment with either tebipenem pivoxil hydrobromide (600 mg orally every 8 h) or amoxicillin-clavulanic acid (500 mg amoxicillin and 125 mg clavulanic acid orally every 8 h). The study included 10 days of treatment (days 1-10) and four follow-up visits (days 14, 21, 90, and 180). The trial was open-label for clinical investigators and patients, but masked for microbiology investigators. Faecal samples were collected at all visits. Sequencing of 16S rDNA was used to measure the diversity metrics, and quantitative culture to quantify selected taxa. The primary outcomes were changes in the α and β diversity and log count of colony-forming units for selected taxa between samples compared with baseline (day 1), and whether any changes reverted during the follow-up period. The analyses were done in the intention-to-treat population. This study was registered with ClinicalTrials.gov (NCT04376554).

FINDINGS

The study was conducted between Jan 23, 2020, and April 6, 2021. 49 volunteers were screened for eligibility, among whom 30 evaluable participants (14 men and 16 women) were assigned: 15 (50%) to the tebipenem pivoxil hydrobromide group and 15 (50%) to the amoxicillin-clavulanic acid group. Baseline characteristics were similar between groups. Complete follow-up was available for all participants, and all participants except one completed treatment as assigned. The diversity metrics showed significant changes from baseline during the treatment period. Significant decreases in richness were observed on days 4-10 (p≤0·0011) in the amoxicillin-clavulanic acid group and on days 4-14 (p≤0·0019) in the tebipenem pivoxil hydrobromide group. Similarly, evenness was significantly decreased during treatment in the amoxicillin-clavulanic acid group (day 4, p=0·030) and the tebipenem pivoxil hydrobromide group (days 4-10, p<0·0001) compared with baseline. Quantitative cultures showed significant decreases in Enterobacterales (days 4-7, p≤0·0030), Enterococcus spp (days 4-14, p=0·025 to p<0·0001), Bifidobacterium spp (days 2-4, p≤0·026), and Bacteroides spp (days 4-10, p≤0·030) in the tebipenem pivoxil hydrobromide group. Similarly, in amoxicillin-clavulanic acid recipients, significant changes were observed in Enterobacterales (days 4-10, p≤0·048), Bifidobacterium spp (days 2-4, p≤0·013), and Lactobacillus spp (days 2-4, p≤0·020). Samples from the follow-up period were not significantly different from those at baseline in β diversity analysis (PERMANOVA, p>0·99). By the end of the study, no significant change was observed compared with baseline in either group. There were no deaths or severe adverse events.

INTERPRETATION

The impact of tebipenem pivoxil hydrobromide on the gut microbiome was similar to that of amoxicillin-clavulanic acid. The safety of antibiotic use with regard to the microbiome should be given attention, as dysbiosis is associated with health and disease.

FUNDING

Spero Therapeutics.

Impact of antibiotic pharmacokinetics in urine on recurrent bacteriuria following treatment of complicated urinary tract infections

The clinical relevance of bacteriuria following antibiotic treatment of complicated urinary tract infections in clinical trials remains controversial. We evaluated the impact of urine pharmacokinetics on the timing of recurrent bacteriuria in a recently completed trial that compared oral tebipenem pivoxil hydrobromide to intravenous ertapenem. The urinary clearance and urine dwell time of ertapenem were prolonged relative to tebipenem and were associated with a temporal difference in the repopulation of bladder urine with bacteria following treatment, potentially confounding the assessment of efficacy.

Absorption, Metabolism, and Excretion of [14C]-Tebipenem Pivoxil Hydrobromide (TBP-PI-HBr) in Healthy Male Subjects

Tebipenem pivoxil hydrobromide (TBP-PI-HBr) is an oral prodrug of pharmacologically active moiety tebipenem (TBP), which is a carbapenem with activity against multidrug-resistant Gram-negative pathogens. Conversion from the prodrug to the active moiety, namely, TBP, occurs in the enterocytes of the gastrointestinal tract via intestinal esterases. The absorption, metabolism, and excretion in humans were evaluated, following the administration of a single oral dose of [14C]-TBP-PI-HBr. Healthy male subjects (n = 8) received a single 600 mg oral dose of TBP-PI-HBr containing approximately 150 μCi of [14C]-TBP-PI-HBr. Blood, urine, and fecal samples were collected to determine the total radioactivity, concentrations of TBP (plasma only), and metabolite profiling and identification. The overall mean recovery of the total radioactivity in urine (38.7%) and feces (44.6%) combined was approximately 83.3% of the administered dose, with individual recoveries ranging from 80.1% to 85.0%. Plasma TBP LC-MS/MS and metabolite profiling data suggest that TBP was the main circulating component in plasma and that it accounts for approximately 54% of the total plasma radioactivity, based on the plasma AUC ratio of TBP/total radioactivity. The ring-open metabolite LJC 11562 was another major component in plasma (>10%). TBP (M12), LJC 11562, and four trace to minor metabolites were identified/characterized in the urine. TBP-PI, TBP (M12), and 11 trace to minor metabolites were identified/characterized in the feces. The renal and fecal routes are major clearance pathways in the elimination of [14C]-TBP-PI-HBr, with a mean combined recovery of 83.3%. TBP and its inactive ring-open metabolite LJC 11562 were the major circulating metabolites in the plasma.

Novel Antimicrobial Agents for Gram-Negative Pathogens

Gram-negative bacterial resistance to antimicrobials has had an exponential increase at a global level during the last decades and represent an everyday challenge, especially for the hospital practice of our era. Concerted efforts from the researchers and the industry have recently provided several novel promising antimicrobials, resilient to various bacterial resistance mechanisms. There are new antimicrobials that became commercially available during the last five years, namely, cefiderocol, imipenem-cilastatin-relebactam, eravacycline, omadacycline, and plazomicin. Furthermore, other agents are in advanced development, having reached phase 3 clinical trials, namely, aztreonam-avibactam, cefepime-enmetazobactam, cefepime-taniborbactam, cefepime-zidebactam, sulopenem, tebipenem, and benapenem. In this present review, we critically discuss the characteristics of the above-mentioned antimicrobials, their pharmacokinetic/pharmacodynamic properties and the current clinical data.

Effect of an Antacid (Aluminum Hydroxide/Magnesium Hydroxide/Simethicone) or a Proton Pump Inhibitor (Omeprazole) on the Pharmacokinetics of Tebipenem Pivoxil Hydrobromide (TBP-PI-HBr) in Healthy Adult Subjects

Tebipenem pivoxil hydrobromide (TBP-PI-HBr) is a novel oral carbapenem prodrug being developed for the treatment of serious bacterial infections. This open-label, 3-period, fixed sequence study evaluated the effect of gastric acid-reducing agents, aluminum hydroxide/magnesium hydroxide/simethicone, and omeprazole on the pharmacokinetics (PK) of tebipenem (TBP), the active moiety, following coadministration with immediate release TBP-PI-HBr during fasting. In Period 1, subjects received a single oral dose of TBP-PI-HBr 600 mg (2 × 300 mg tablets). In Period 2, subjects received a single oral dose of aluminum hydroxide 800 mg/magnesium hydroxide 800 mg/simethicone 80 mg suspension co-administered with a single dose of TBP-PI-HBr 600 mg. In Period 3, subjects received a single oral dose of omeprazole 40 mg once daily over 5 days, followed by single dose administration of TBP-PI-HBr 600 mg on day 5. In each period, whole blood samples were obtained prior to, and up to 24 h, following TBP-PI-HBr dose administration in order to characterize TBP PK. A 7-day washout was required between periods. Twenty subjects were enrolled and completed the study. Following co-administration of TBP-PI-HBr with either aluminum hydroxide/magnesium hydroxide/simethicone or omeprazole, total TBP exposure (area under the curve [AUC]) was approximately 11% (geometric mean ratio 89.2, 90% confidence interval: 83,2, 95.7) lower, and Cmax was 22% (geometric mean ratio 78.4, 90% confidence interval: 67.9, 90.6) and 43% (geometric mean ratio 56.9, 90% confidence interval: 49.2, 65.8) lower, respectively, compared to administration of TBP-PI-HBr alone. Mean TBP elimination half-life (t_1/2) was generally comparable across treatments (range: 1.0 to 1.5 h). Concomitant administration of TBP-PI-HBr with omeprazole or aluminum hydroxide/magnesium hydroxide/simethicone is not expected to impact the efficacy of TBP-PI-HBr, as there is minimal impact on TBP plasma AUC, which is the pharmacodynamic driver of efficacy. Co-administration was generally safe and well tolerated.

Antimicrobial Activity of Tebipenem and Comparators against Enterobacterales from diverse Outpatient Centers and Nursing Homes in the United States

INTRODUCTION

Tebipenem is a potential option for the treatment of a range of infections because of its oral dosing coupled with the safety profile of the β-lactam antimicrobial class.

OBJECTIVES

To evaluate tebipenem in vitro activity against a challenge set of clinical Enterobacterales collected from outpatient and community settings.

METHODS

618 Enterobacterales isolates were submitted by 11 geographically dispersed U.S medical centers that processed cultures from affiliated outpatient centers in 2022. Susceptibility tests for tebipenem and comparator agents were performed by broth microdilution. Extended-spectrum-β-lactamase (ESBL)-like isolates were identified phenotypically. Multidrug-resistant isolates were non-susceptible to ≥1 agent in ≥3 antimicrobial classes. Genotypic testing (CarbaR) was conducted on select isolates.

RESULTS

Isolates (59% Escherichia coli) were recovered from patients seen predominantly in urology/nephrology (24%), nursing home/long-term care (21%), and ambulatory/primary care (21%) clinics. Comparator agent susceptibility rates against all isolates were as follows: levofloxacin (67.5%), amoxicillin/clavulanate (73.6%), cefixime (70.4%), cefpodoxime (70%), cephalexin (61.7%), ceftriaxone (74.4%), cefazolin (63.8%), ertapenem (97.6%), meropenem (99.7%), nitrofurantoin (64.9%), and sulfamethoxazole/trimethoprim (70.9%). Overall, 90.3% (558/619) of isolates were inhibited at a tebipenem MIC of ≤0.125 mg/L (MIC_50/90, 0.016/0.125 mg/L), including 85.7% inhibition of ESBL-phenotype isolates (n=161; MIC_50/90, 0.03/0.25 mg/L), 86.3% of levofloxacin and sulfamethoxazole/trimethoprim co-resistant isolates (n=95; MIC_50/90, 0.016/0.25 mg/L) and 84.3% of multidrug-resistant isolates (n = 172; MIC_50/90, 0.03/0.25 mg/L). Carbapenemase genes were observed in 2 ESBL-phenotype isolates with a tebipenem MIC of ≥0.5 mg/L.

CONCLUSION

Relative to common oral comparators, these data demonstrate excellent tebipenem in vitro activity against Enterobacterales isolated from patients receiving care in outpatient settings, including urology clinics and nursing homes.

Contemporary Evaluation of Tebipenem In Vitro Activity against Enterobacterales Clinical Isolates Causing Urinary Tract Infections in US Medical Centers (2019-2020)

Tebipenem pivoxil is an oral broad-spectrum carbapenem. This study evaluated the activity of tebipenem and comparators against UTI Enterobacterales from US hospitals (2019-2020). 3,576 Enterobacterales causing UTI in 52 centers in 9 US Census Divisions were included. Susceptibility testing followed the CLSI broth microdilution method. Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis with an MIC of ≥2 μg/mL for ceftazidime, ceftriaxone, and/or aztreonam were designated ESBL. Isolates were also grouped based on MDR phenotype. Tebipenem, meropenem, and ertapenem had MIC₉₀ against Enterobacterales of 0.06 μg/mL, 0.06 μg/mL and 0.03 μg/mL, respectively. Low susceptibility results for aztreonam (87.1% susceptible), cefazidime (88.1%), ceftriaxone (84.8%), and other agents were observed. Tebipenem and ertapenem were equally potent (MIC₉₀, 0.015 to 0.03 μg/mL) against E. coli and K. pneumoniae, whereas ertapenem showed an MIC 8-fold lower than tebipenem against P. mirabilis. Oral agents, such as amoxicillin-clavulanate, levofloxacin, and trimethoprim-sulfamethoxazole, showed elevated nonsusceptibility rates in the Middle Atlantic region (26, 45, 47, and 41%, respectively). ESBL prevalence varied from 7% to 16%, except in the Middle Atlantic region (42%). The carbapenems were active against ESBL and MDR isolates (93.7 to 96.8% susceptible). Elevated rates of ESBL in UTI pathogens in US hospitals were noted as well as a uniform in vitro potency (MIC₉₀) of tebipenem and the intravenous carbapenems, regardless of phenotype. IMPORTANCE The occurrence of urinary-tract Enterobacterales pathogens producing ESBL enzymes in community and nosocomial settings continues to increase, as does the coresistance to fluoroquinolones, trimethoprim-sulfamethoxazole and nitrofurantoin often exhibited by these pathogens. This scenario complicates the clinical empirical and guided management of UTI by precluding the use of oral and many intravenous options. Oral options appear compromised even among some ESBL-negative isolates, against which the use of parenteral agents may be required. In addition, the interregional variability of susceptibility results of US UTI pathogens provides a less predictable susceptibility pattern to inform empirical treatment decisions. This study evaluated the in vitro activity of tebipenem against contemporary uropathogens, including those resistant to currently available oral options.

A Comprehensive Overview of the Antibiotics Approved in the Last Two Decades: Retrospects and Prospects

Due to the overuse of antibiotics, bacterial resistance has markedly increased to become a global problem and a major threat to human health. Fortunately, in recent years, various new antibiotics have been developed through both improvements to traditional antibiotics and the discovery of antibiotics with novel mechanisms with the aim of addressing the decrease in the efficacy of traditional antibiotics. This manuscript reviews the antibiotics that have been approved for marketing in the last 20 years with an emphasis on the antibacterial properties, mechanisms, structure-activity relationships (SARs), and clinical safety of these antibiotics. Furthermore, the current deficiencies, opportunities for improvement, and prospects of antibiotics are thoroughly discussed to provide new insights for the design and development of safer and more potent antibiotics.

Relative bioavailability of crushed tebipenem administered through a nasogastric tube with and without enteral feeding

OBJECTIVE

Tebipenem pivoxil hydrobromide is an orally bioavailable carbapenem prodrug of the active agent tebipenem with broad-spectrum activity against drug-resistant Enterobacterales. This study aimed to evaluate the relative bioavailability of crushed tebipenem tablets administered via nasogastric tube (NGT) with or without concomitant enteral feeds.

METHODS

This Phase 1, open label study randomized 12 healthy subjects to receive a crushed tebipenem tablet via NGT (n = 6) or via NGT with concomitant Osmolite® enteral feeds (n = 6) on Study Day 1, followed by oral administration of tebipenem whole tablet (reference formulation) on Study Day 2. Tebipenem plasma concentrations were measured by LC with mass spectrometry. Bioequivalence was determined using pharmacokinetic parameters derived through non-compartmental analyses.

RESULTS

Mean ± SD tebipenem pharmacokinetic parameters in plasma for subjects who received a crushed tablet via NGT (relative to whole tablet) and a crushed tablet with enteral feeds (relative to whole tablet) were as follows: maximum total plasma concentration (Cmax), 11.1 ± 3.9 (12 ± 3.4) and 10.2 ± 1.9 (10 ± 4) mg/L; area under the curve (AUC0-8), 17.5 ± 3.5 (17.9 ± 2.3) and 15 ± 4.3 (13.4 ± 5.3) mg•h/L. Using the 90% CI criteria, Cmaxand AUC0-8 values for tebipenem were found to be bioequivalent following alternative methods of administration compared with oral dosing of the whole tablet. The three methods of administration were well tolerated.

CONCLUSION

Results demonstrate that tebipenem maintained bioequivalence when crushed and administered via NGT with and without accompanying enteral feeds in healthy subjects, relative to whole tablet oral administration. Data therefore support alternative methods of tebipenem administration depending on patient condition.

A systematic scoping review of faropenem and other oral penems: treatment of Enterobacterales infections, development of resistance and cross-resistance to carbapenems

Background

Antimicrobial resistance is an urgent global healthcare concern. Beyond carbapenems as broad-spectrum, often 'last resort' antibiotics, oral penem antibiotics currently are approved only in Japan and India, used for the treatment of indications including urinary tract infections (UTIs). Exploring oral penem use to better understand the impact of antibiotic resistance on public health would help inform the management of infectious diseases, including UTIs.

Scoping Review Methodology

This scoping review investigated the impact of faropenem and other oral penems on Enterobacterales infection treatment and evaluated evidence for faropenem resistance and cross-resistance to carbapenems. PubMed, Embase, J-STAGE and CiNii were searched for relevant English- or Japanese-language articles published between 1 January 1996 and 6 August 2021.

Key Findings

From 705 unique publications, 29 eligible articles were included (16 in vitro studies; 10 clinical trials; 2 in vitro and in vivo studies; and 1 retrospective medical chart review). Limited evidence described faropenem to treat infectious disease; only four randomized clinical trials were identified. Faropenem dosing regimens varied broadly within and between indications. One study indicated potential dependence of penem efficacy on underlying antibiotic resistance mechanisms, while several studies reported UTI persistence or recurrence after faropenem treatment. In vitro MIC data suggested some potential bacterial resistance to faropenem, while limited clinical data showed resistance emergence after faropenem treatment. Preliminary in vitro evidence suggested faropenem resistance might foster cross-resistance to carbapenems. Overall, very limited clinical evidence describes faropenem for treating infectious diseases. Preclinical and clinical research investment and dedicated community surveillance monitoring is crucial for understanding faropenem treatment patterns, resistance and potential cross-resistance to carbapenems.

Determining the in vitro susceptibility of tebipenem, an oral carbapenem, against third-generation cephalosporin-resistant Escherichia coli and Klebsiella pneumoniae isolated from bloodstream infections

Background

Antimicrobials for bloodstream infections due to ESBL- and AmpC-producing Escherichia coli and Klebsiella pneumoniae are significantly limited due to widespread antimicrobial resistance. Tebipenem, an oral carbapenem, exhibits stability against these resistance mechanisms and may prove an attractive alternative.

Methods

The in vitro susceptibility of tebipenem was assessed against previously whole-genome sequenced ESBL- and AmpC-producing E. coli (274 isolates) and K. pneumoniae (42 isolates) derived from bloodstream infections using broth microdilution testing. Resulting tebipenem MICs were compared with those of other carbapenems previously tested against the isolate collection. Tebipenem activity was also compared against those isolates expressing co-resistance to the common oral antibiotics ciprofloxacin and trimethoprim/sulfamethoxazole.

Results

The tebipenem MIC₉₀ value was found to be 0.03 mg/L for E. coli and 0.125 mg/L for K. pneumoniae. For E. coli, the tebipenem MIC₉₀ value was equivalent to that of meropenem, 2-fold lower than that of doripenem, and 8-fold and 4-fold lower than that of imipenem and ertapenem, respectively. For K. pneumoniae, the tebipenem MIC₉₀ value was 2-fold higher than that of meropenem, equivalent to that of doripenem, and 4-fold and 2-fold lower than that of imipenem and ertapenem, respectively. Tebipenem MICs were also unaffected by the expression of co-resistance to ciprofloxacin and trimethoprim/sulfamethoxazole.

Conclusions

The in vitro activity of tebipenem was unaffected by the production of ESBL and AmpC enzymes. Tebipenem also retained its activity against those isolates expressing co-resistance to ciprofloxacin and trimethoprim/sulfamethoxazole. These findings therefore highlight tebipenem as a potential option for the treatment of invasive MDR infections.

Plasma and Intrapulmonary Concentrations of Tebipenem following Oral Administration of Tebipenem Pivoxil Hydrobromide to Healthy Adult Subjects

Tebipenem pivoxil hydrobromide (TBP-PI-HBr) is an oral carbapenem prodrug being developed for the treatment of serious bacterial infections. The active moiety, tebipenem, has broad-spectrum activity against common Enterobacterales pathogens, including extended-spectrum-β-lactamase (ESBL)-producing multidrug-resistant strains. This study evaluated the intrapulmonary pharmacokinetics (PK) and epithelial lining fluid (ELF) and alveolar macrophage (AM) concentrations of tebipenem relative to plasma levels in nonsmoking, healthy adult subjects. Thirty subjects received oral TBP-PI-HBr at 600 mg every 8 h for five doses. Serial blood samples were collected following the last dose. Each subject underwent one standardized bronchoscopy with bronchoalveolar lavage (BAL) 1, 2, 4, 6, or 8 h after the fifth dose of TBP-PI-HBr. The tebipenem area under the concentration-time curve for the 8-h dosing interval (AUC_0-8) values in plasma, ELF, and AMs were calculated using the mean concentration at each BAL sampling time. Ratios of AUC_0-8 values for total ELF and AMs to those for unbound plasma were determined, using a plasma protein binding value of 42%. Mean values ± standard deviations (SD) of tebipenem maximum (C_max) and minimum (C_min) total plasma concentrations were 11.37 ± 3.87 mg/L and 0.043 ± 0.039 mg/L, respectively. Peak tebipenem concentrations in plasma, ELF, and AMs occurred at 1 h and then decreased over 8 h. Ratios of tebipenem AUC_0-8 values for ELF and AMs to those for unbound plasma were 0.191 and 0.047, respectively. Four (13.3%) subjects experienced adverse events (diarrhea, fatigue, papule, and coronavirus disease 2019 [COVID-19]); all resolved, and none were severe or serious. Tebipenem is distributed into the lungs of healthy adults, which supports the further evaluation of TBP-PI-HBr for the treatment of lower respiratory tract bacterial infections caused by susceptible pathogens. (This study has been registered at ClinicalTrials.gov under identifier NCT04710407.).

The Class A β-Lactamase Produced by Burkholderia Species Compromises the Potency of Tebipenem against a Panel of Isolates from the United States

Tebipenem-pivoxil hydrobromide, an orally bioavailable carbapenem, is currently in clinical development for the treatment of extended-spectrum β-lactamase- and AmpC-producing Enterobacterales. Previously, tebipenem was found to possess antimicrobial activity against the biothreat pathogens, Burkholderia pseudomallei and Burkholderia mallei. Thus, herein, tebipenem was evaluated against a panel of 150 curated strains of Burkholderia cepacia complex (Bcc) and Burkholderia gladioli, pathogens that infect people who are immunocompromised or have cystic fibrosis. Using the provisional susceptibility breakpoint of 0.12 mg/L for tebipenem, 100% of the Bcc and B. gladioli tested as being provisionally resistant to tebipenem. Bcc and B. gladioli possess two inducible chromosomal β-lactamases, PenA and AmpC. Using purified PenA1 and AmpC1, model β-lactamases expressed in Burkholderia multivorans ATCC 17616, PenA1 was found to slowly hydrolyze tebipenem, while AmpC1 was inhibited by tebipenem with a k₂/K value of 1.9 ± 0.1 × 10³ M⁻¹s⁻¹. In addition, tebipenem was found to be a weak inducer of bla_PenA1 expression. The combination of the slow hydrolysis by PenA1 and weak induction of bla_PenA1 likely compromises the potency of tebipenem against Bcc and B. gladioli.

Pharmacokinetics of Oral Tebipenem Pivoxil Hydrobromide in Subjects with Various Degrees of Renal Impairment

Tebipenem pivoxil hydrobromide (TBP-PI-HBr) is an oral carbapenem prodrug antimicrobial agent with broad-spectrum activity that includes multidrug-resistant (MDR) Enterobacterales. This study evaluated the safety, tolerability, and pharmacokinetics of TBP-PI-HBr in healthy subjects with normal renal function (cohort 1) and subjects with various degrees of renal impairment (RI [cohorts 2 to 4]) or end-stage renal disease (ESRD) receiving hemodialysis (HD) (cohort 5). Subjects in cohorts 1 to 4 received a single oral dose of TBP-PI-HBr (600 mg). Subjects in cohort 5 received single-dose administration (600 mg) in 2 separate periods: pre-HD (period 2) and post-HD (period 1). Pharmacokinetic (PK) parameters for TBP, the active moiety, were determined using noncompartmental analysis. Compared with cohort 1, the TBP plasma area under the curve (AUC) increased 1.4- to 4.5-fold among cohorts 2 to 4, the maximum concentration of drug in plasma (C_max) increased up to 1.3-fold and renal clearance (CL_R) decreased from 13.4 L/h to 2.4 L/h as the severity of RI increased. Plasma TBP concentrations decreased over 8 to 12 h in cohorts 1 to 4, and apparent total body clearance (CL/F) correlated (R² = 0.585) with creatinine clearance (CL_CR). TBP urinary excretion ranged from 38% to 64% of the administered dose for cohorts 1 to 4. Subjects in cohort 5 had an approximately 7-fold increase in TBP AUC and elimination half-life (t_1/2) versus cohort 1. After 4 h of HD, mean TBP plasma exposure decreased by approximately 40%. Overall, TBP plasma exposure increased with increasing RI, highlighting the renal route importance in TBP elimination. A dose reduction of TBP-PI-HBr may be needed in patients with RI (CL_CR of ≤50 mL/min) and those with ESRD on HD. TBP-PI-HBr was well tolerated across all cohorts. (This study has been registered at ClinicalTrials.gov under registration no. NCT04178577.).

Oral Tebipenem Pivoxil Hydrobromide in Complicated Urinary Tract Infection

BACKGROUND

There is a need for oral antibiotic agents that are effective against multidrug-resistant gram-negative uropathogens. Tebipenem pivoxil hydrobromide is an orally bioavailable carbapenem with activity against uropathogenic Enterobacterales, including extended-spectrum beta-lactamase-producing and fluoroquinolone-resistant strains.

METHODS

In this phase 3, international, double-blind, double-dummy trial, we evaluated the efficacy and safety of orally administered tebipenem pivoxil hydrobromide as compared with intravenous ertapenem in patients with complicated urinary tract infection or acute pyelonephritis. Patients were randomly assigned, in a 1:1 ratio, to receive oral tebipenem pivoxil hydrobromide (at a dose of 600 mg every 8 hours) or intravenous ertapenem (at a dose of 1 g every 24 hours) for 7 to 10 days (or up to 14 days in patients with bacteremia). The primary efficacy end point was overall response (a composite of clinical cure and favorable microbiologic response) at a test-of-cure visit (on day 19, within a ±2-day window) in the microbiologic intention-to-treat population. The noninferiority margin was 12.5%.

RESULTS

A total of 1372 hospitalized adult patients were enrolled; 868 patients (63.3%) were included in the microbiologic intention-to-treat population (50.8% of whom had complicated urinary tract infections and 49.2% of whom had pyelonephritis). An overall response was seen in 264 of 449 patients (58.8%) who received tebipenem pivoxil hydrobromide, as compared with 258 of 419 patients (61.6%) who received ertapenem (weighted difference, -3.3 percentage points; 95% confidence interval [CI], -9.7 to 3.2). Clinical cure at the test-of-cure visit was observed in 93.1% of the patients in the microbiologic intention-to-treat population who received tebipenem pivoxil hydrobromide and 93.6% of patients who received ertapenem (weighted difference, -0.6 percentage point; 95% CI, -4.0 to 2.8); the majority of patients with microbiologic response failures at the test-of-cure visit were asymptomatic patients with recurrent bacteriuria. Secondary and subgroup analyses were supportive of the primary analysis. Adverse events were observed in 25.7% of patients who received tebipenem pivoxil hydrobromide and in 25.6% of patients who received ertapenem; the most common adverse events were mild diarrhea and headache.

CONCLUSIONS

Oral tebipenem pivoxil hydrobromide was noninferior to intravenous ertapenem in the treatment of complicated urinary tract infection and acute pyelonephritis and had a similar safety profile. (Funded by Spero Therapeutics and the Department of Health and Human Services; ADAPT-PO ClinicalTrials.gov number, NCT03788967.).

The Chemical Relationship Among Beta-Lactam Antibiotics and Potential Impacts on Reactivity and Decomposition

Beta-lactam antibiotics remain one of the most commonly prescribed drug classes, but they are limited by their propensity to cause hypersensitivity reactions (e.g., from allergy to anaphylaxis) as well as by the emergence of bacteria with a myriad of resistance mechanisms such as β-lactamases. While development efforts continue to focus on overcoming resistance, there are ongoing concerns regarding cross-contamination of β-lactams during manufacturing and compounding of these drugs. Additionally, there is a need to reduce levels of drugs such as β-lactam antibiotics in waste-water to mitigate the risk of environmental exposure. To help address future development of effective remediation chemistries and processes, it is desired to better understand the structural relationship among the most common β-lactams. This study includes the creation of a class-wide structural ordering of the entire β-lactam series, including both United States Food and Drug Association (US-FDA)-approved drugs and experimental therapies. The result is a structural relational map: the "Lactamome," which positions each substance according to architecture and chemical end-group. We utilized a novel method to compare the structural relationships of β-lactam antibiotics among the radial cladogram and describe the positioning with respect to efficacy, resistance to hydrolysis, reported hypersensitivity, and Woodward height. The resulting classification scheme may help with the development of broad-spectrum treatments that reduce the risk of occupational exposure and negative environmental impacts, assist practitioners with avoiding adverse patient reactions, and help direct future drug research.

Analysis of the Clinical Pipeline of Treatments for Drug-Resistant Bacterial Infections: Despite Progress, More Action Is Needed

There is an urgent global need for new strategies and drugs to control and treat multidrug-resistant bacterial infections. In 2017, the World Health Organization (WHO) released a list of 12 antibiotic-resistant priority pathogens and began to critically analyze the antibacterial clinical pipeline. This review analyzes "traditional" and "nontraditional" antibacterial agents and modulators in clinical development current on 30 June 2021 with activity against the WHO priority pathogens mycobacteria and Clostridioides difficile. Since 2017, 12 new antibacterial drugs have been approved globally, but only vaborbactam belongs to a new antibacterial class. Also innovative is the cephalosporin derivative cefiderocol, which incorporates an iron-chelating siderophore that facilitates Gram-negative bacteria cell entry. Overall, there were 76 antibacterial agents in clinical development (45 traditional and 31 nontraditional), with 28 in phase 1, 32 in phase 2, 12 in phase 3, and 4 under regulatory evaluation. Forty-one out of 76 (54%) targeted WHO priority pathogens, 16 (21%) were against mycobacteria, 15 (20%) were against C. difficile, and 4 (5%) were nontraditional agents with broad-spectrum effects. Nineteen of the 76 antibacterial agents have new pharmacophores, and 4 of these have new modes of actions not previously exploited by marketed antibacterial drugs. Despite there being 76 antibacterial clinical candidates, this analysis indicated that there were still relatively few clinically differentiated antibacterial agents in late-stage clinical development, especially against critical-priority pathogens. We believe that future antibacterial research and development (R&D) should focus on the development of innovative and clinically differentiated candidates that have clear and feasible progression pathways to the market.

Drugs That Changed Society: History and Current Status of the Early Antibiotics: Salvarsan, Sulfonamides, and β-Lactams

The appearance of antibiotic drugs revolutionized the possibilities for treatment of diseases with high mortality such as pneumonia, sepsis, plaque, diphtheria, tetanus, typhoid fever, and tuberculosis. Today fewer than 1% of mortalities in high income countries are caused by diseases caused by bacteria. However, it should be recalled that the antibiotics were introduced in parallel with sanitation including sewerage, piped drinking water, high standard of living and improved understanding of the connection between food and health. Development of salvarsan, sulfonamides, and β-lactams into efficient drugs is described. The effects on life expectancy and life quality of these new drugs are indicated.

Identification of related impurities in an oral pharmaceutical formulation of tebipenem pivoxil using ultra-high-performance liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry

RATIONALE

Tebipenem pivoxil (TBPM-PI) has been developed as the first oral carbapenem drug in the world to treat otolaryngological and respiratory infections in pediatric patients. Due to its structural properties and external factors, some related impurities, which may cause side effects in patients, might be formed during the synthesis and storage of TBPM-PI. It was vital to rapidly separate and identify the related impurities to guarantee the safe use of TBPM-PI.

METHODS

A method using ultra-high-performance liquid chromatography (UHPLC) coupled with quadrupole time-of-flight tandem mass spectrometry (QTOF-MS/MS) was developed to separate and detect TBPM-PI and related impurities in an oral pharmaceutical formulation. LC/MS and MS/MS spectra of these compounds in the formulation were acquired to confirm their elemental compositions and propose their structures based on LC/MS data and fragmentation pathways of available reference substances.

RESULTS

LC/MS parameters and MS/MS fragmentation pathways of reference substances of TBPM-PI and related impurities were summarized in detail. Based on this, a total of 23 related impurities were found and characterized in the oral pharmaceutical formulation. Eight of these were verified by comparison with reference substances and the structures of the other 15 were proposed for the first time. In addition, four of these compounds were produced by the reaction of excipients and pre-existing related impurities.

CONCLUSIONS

A UHPLC/QTOF-MS method was established and used for the separation and identification of 23 related impurities in a TBPM-PI oral pharmaceutical formulation. Moreover, it was proved that new related impurities could be produced by the reaction of excipients in the pharmaceutical formulation and related impurities in the corresponding active pharmaceutical ingredient (API).

Microbiological Characterization of VNRX-5236, a Broad-Spectrum β-Lactamase Inhibitor for Rescue of the Orally Bioavailable Cephalosporin Ceftibuten as a Carbapenem-Sparing Agent against Strains of Enterobacterales Expressing Extended-Spectrum β-Lactamases and Serine Carbapenemases

There is an urgent need for oral agents to combat resistant Gram-negative pathogens. Here, we describe the characterization of VNRX-5236, a broad-spectrum boronic acid β-lactamase inhibitor (BLI), and its orally bioavailable etzadroxil prodrug, VNRX-7145. VNRX-7145 is being developed in combination with ceftibuten, an oral cephalosporin, to combat strains of Enterobacterales expressing extended-spectrum β-lactamases (ESBLs) and serine carbapenemases. VNRX-5236 is a reversible covalent inhibitor of serine β-lactamases, with inactivation efficiencies on the order of 10⁴ M⁻¹ · sec⁻¹, and prolonged active site residence times (t_1/2, 5 to 46 min). The spectrum of inhibition includes Ambler class A ESBLs, class C cephalosporinases, and class A and D carbapenemases (KPC and OXA-48, respectively). Rescue of ceftibuten by VNRX-5236 (fixed at 4 μg/ml) in isogenic strains of Escherichia coli expressing class A, C, or D β-lactamases demonstrated an expanded spectrum of activity relative to oral comparators, including investigational penems, sulopenem, and tebipenem. VNRX-5236 rescued ceftibuten activity in clinical isolates of Enterobacterales expressing ESBLs (MIC₉₀, 0.25 μg/ml), KPCs (MIC₉₀, 1 μg/ml), class C cephalosporinases (MIC₉₀, 1 μg/ml), and OXA-48-type carbapenemases (MIC₉₀, 1 μg/ml). Frequency of resistance studies demonstrated a low propensity for recovery of resistant variants at 4× the MIC of the ceftibuten/VNRX-5236 combination. In vivo, whereas ceftibuten alone was ineffective (50% effective dose [ED₅₀], >128 mg/kg), ceftibuten/VNRX-7145 administered orally protected mice from lethal septicemia caused by Klebsiella pneumoniae producing KPC carbapenemase (ED₅₀, 12.9 mg/kg). The data demonstrate potent, broad-spectrum rescue of ceftibuten activity by VNRX-5236 in clinical isolates of cephalosporin-resistant and carbapenem-resistant Enterobacterales.