Faropenem Medoxomil

Anti-Tuberculosis Activity of Three Carbapenems, Clofazimine and Nitazoxanide Using a Novel Ex Vivo Phenotypic Drug Susceptibility Model of Human Tuberculosis

We evaluated a novel physiological 3-D bioelectrospray model of the tuberculosis (TB) granuloma to test the activity of a known anti-TB drug, clofazimine; three carbapenems with potential activity, including one currently used in therapy; and nitazoxanide, an anti-parasitic compound with possible TB activity (all chosen as conventional drug susceptibility was problematical). PBMCs collected from healthy donors were isolated and infected with M. tuberculosis H37Rv lux (i.e., luciferase). Microspheres were generated with the infected cells; the anti-microbial compounds were added and bacterial luminescence was monitored for at least 21 days. Clavulanate was added to each carbapenem to inhibit beta-lactamases. M. tuberculosis (MTB) killing efficacy was dose dependent. Clofazimine was the most effective drug inhibiting MTB growth at 2 mg/L with good killing activity at both concentrations tested. It was the only drug that killed bacteria at the lowest concentration tested. Carbapenems showed modest initial activity that was lost at around day 10 of incubation and clavulanate did not increase killing activity. Of the carbapenems tested, tebipenem was the most efficient in killing MTB, albeit at a high concentration. Nitazoxanide was effective only at concentrations not achievable with current dosing (although this might partly have been an artefact related to extensive protein binding).

Role of Faropenem in Treatment of Pediatric Infections: The Current State of Knowledge

Carbapenems play an important role in the management of bacterial infections. Meropenem, imipenem, ertapenem, and faropenem are carbapenems with the broadest antibacterial spectrum and strong antibacterial activity. Faropenem is a novel oral carbapenem with an advantage over other parenteral carbapenems in the series. Like other β-lactam antibiotics, faropenem inhibits cell wall synthesis by inhibiting penicillin-binding proteins (PBPs). Faropenem is stable against β-lactamase and has a low propensity for bacterial resistance. Faropenem has demonstrated excellent in-vitro and clinical activity in adult infections with a broad spectrum of activity. Faropenem also has a favorable safety profile. These activities of the faropenem created the interest of researchers in exploring its use in the treatment of pediatric infections. After promising outcomes in-vitro and clinical evaluation in children, faropenem is now approved in some parts of the world for the treatment of pediatric infections. Faropenem oral dry syrup is available for the treatment of a wide range of pediatric infections, including upper respiratory tract infections, urinary tract infections, dermatological infections, and bacterial periodontal infections in children. The current recommended clinical dose in pediatric patients is 15 mg/kg/ day, divided into three doses. The availability of faropenem dry syrup has expanded the current therapeutic options for treating pediatric infections.

In this review, we have put light on the in-vitro and clinical studies of faropenem dry syrup in pediatric patients, along with its molecular and pharmacological basics.

Mycobacterium tuberculosis sterilizing activity of faropenem, pyrazinamide and linezolid combination and failure to shorten the therapy duration

Background:

Faropenem (F), an orally bioavailable β-lactam, kills Mycobacterium tuberculosis (Mtb) without the help of a β-lactamase inhibitor. This study explored the sterilizing effect of adding F once or twice daily to a linezolid (L) plus pyrazinamide (Z) backbone regimen.

Methods:

In vitro studies were performed using the hollow fiber model of tuberculosis (HFS-TB) to compare the kill rates of: 1) ZL two-drug combination; 2) F administered once daily plus ZL (F₁ZL); 3) F administered twice-daily plus once daily ZL (F₂ZL); 4) F₂ZL with high-dose Z (F₂Z_hiL); 5) standard therapy of isoniazid, rifampin and Z; and 6) non-treated controls. The study was performed over 56 days with three HFS-TB replicates for each regimen.

Results:

Mtb in the non-treated HFS-TB grew at a rate of 0.018 ± 0.007 log₁₀ CFU/mL/day. The exponential kill rates for standard therapy were 6.6–13.2-fold higher than ZL dual therapy. The F₁ZL and F₂ZL regimens ranked third. The pre-existing isoniazid-resistant sub-population in the inoculum (1.34 ± 0.57 log₁₀ CFU/mL) grew to 4.21 ± 0.58 log₁₀ CFU/mL in 56 days in non-treated HFS-TB. However, no isoniazid-resistant sub-population was recorded in any of the FZL combination regimens.

Conclusion:

Due to the slow kill rate compared to standard therapy, FZL regimens are unlikely to shorten therapy duration. Efficacy of these regimens against drug-resistant tuberculosis needs to be determined.

Tedizolid, Faropenem, and Moxifloxacin Combination With Potential Activity Against Nonreplicating Mycobacterium tuberculosis

Background:Mycobacteriumtuberculosis [Mtb] could be present in different metabolic population in the lung lesions, and nonreplicating persisters [NRP], associated with latent tuberculosis [TB], are the most difficult to kill.

Objective: Test the combination of tedizolid, moxifloxacin, and faropenem for activity against NRP using Mtb SS18b in the hollow fiber model [HFS-TB].

Methods: Tedizolid and moxifloxacin were tested as, first, two-drug combination against log-phase growth [LPG] and, second, slowly replicating bacilli [SRB] under acidic condition and with faropenem to create a three-drug combination regimen. Finally, standard regimen [isoniazid-rifampin-pyrazinamide] was used as comparator in the HFS-TB experiment with NRP Mtb. HFS-TB units were sampled for drug-concentration measurement as well as for estimation of bacterial burden using solid agar and mycobacterial growth indicator tube [MGIT] method. Linear regression was used to calculate the kill slopes with each treatment regimen and analysis of variance (ANOVA) to compare the regimen.

Results: Tedizolid at standard dose in combination with high-dose moxifloxacin killed 3.05 log₁₀ CFU/ml LPG Mtb and 7.37 log₁₀ CFU/ml SRB in the bactericidal and sterilizing activity HFS-TB experiments, respectively. There was no statistical difference between tedizolid-moxifloxacin-faropenem combination and the standard regimen as both killed 7.35 log₁₀ CFU/ml NRP Mtb in 21 days. There was no emergence of resistance to any of the drugs studied in the three HFS-TB experiments.

Conclusion: The experimental regimen of tedizolid, moxifloxacin, and faropenem could effectively kill NRP population of Mtb, and given the efficacy against different metabolic population of Mtb could serve as a pan-TB regimen. Clinical studies are warranted to validate the in vitro findings.

Faropenem resistance causes in vitro cross-resistance to carbapenems in ESBL-producing Escherichia coli

OBJECTIVE

Faropenem is an oral penem drug with activity against Gram-positive and Gram-negative bacteria, including CTX-M-15-type extended spectrum beta-lactamase (ESBL)-producing Enterobacteriales and anaerobic bacteria. As there are structural similarities, there is concern for the development of carbapenem cross-resistance; however, there are no studies confirming this. This study examined whether in vitro development of faropenem resistance in Escherichia coli isolates would result in cross-resistance to carbapenems.

METHODS

Four well-characterized E. coli isolates from the US Centers for Disease Control and Prevention antibiotic resistance isolate bank were utilized. Three isolates (NSF1, NSF2 and NSF3) are ESBL producers (CTX-M-15) and one (NSF4) is pan-susceptible. Faropenem minimum inhibitory concentrations (MICs) were determined and resistance was induced by serial passaging in increasing concentrations of faropenem. Susceptibility to carbapenems was determined and whole-genome sequencing (WGS) was performed to identify the underlying genetic mechanism leading to carbapenem resistance.

RESULTS

Faropenem MIC increased from 1 mg/L to 64 mg/L within 10 days for NSF2 and NSF4 isolates, and from 2 mg/L to 64 mg/L within 7 days for NSF1 and NSF3 isolates. Reduced carbapenem susceptibility (ertapenem MIC ≥8 mg/L, doripenem/meropenem ≥2 mg/L and imipenem ≥1 mg/L) developed among three CTX-M-15-producing isolates that were faropenem-resistant, but not in NSF4 isolate that lacked ESBL enzyme. WGS analysis revealed non-synonymous changes in the ompC gene among three CTX-M-15-producing isolates, and a single nucleotide polymorphism (SNP) in the envZ gene in NSF4 isolate.

CONCLUSION

Induced resistance to faropenem causes cross-resistance to carbapenems among E. coli isolates containing CTX-M-15-type ESBL enzymes.

Activity of faropenem with and without rifampicin against Mycobacterium tuberculosis: evaluation in a whole-blood bactericidal activity trial

Background

Faropenem has in vitro activity against Mycobacterium tuberculosis (Mtb) and shows synergy with rifampicin. We tested this in a whole-blood bactericidal activity (WBA) trial.

Methods

We randomized healthy volunteers to receive a single oral dose of faropenem (600 mg) with amoxicillin/clavulanic acid (500/125 mg) ( n  =   8), rifampicin (10 mg/kg) ( n  =   14) or the combination rifampicin + faropenem + amoxicillin/clavulanic acid ( n  =   14). Blood was drawn at intervals to 8 h post-dose. Drug levels were measured using LC-tandem MS. WBA was measured by inoculating blood samples with Mtb and estimating the change in bacterial cfu after 72 h. Trial registration: ClinicalTrials.gov (NCT02393586).

Results

There was no activity in the faropenem + amoxicillin/clavulanic acid group (cumulative WBA 0.02 Δlog cfu; P  =   0.99 versus zero change). There was a suggestion of a trend favouring the rifampicin + faropenem + amoxicillin/clavulanic acid group at 8 h (cumulative WBA -0.19 ± 0.03 and -0.26 ± 0.03 Δlog cfu in the rifampicin and rifampicin + faropenem + amoxicillin/clavulanic acid groups, respectively; P  =   0.180), which was significant in the first hour post-dose ( P  =   0.032). Faropenem C max and AUC were 5.4 mg/L and 16.2 mg·h/L, respectively, and MIC for Mtb H37Rv was 5-10 mg/L.

Conclusions

Faropenem is not active when used alone, possibly due to inadequate plasma levels relative to MIC. However, there was a suggestion of modest synergy with rifampicin that may merit further testing in clinical trials.

A Faropenem, Linezolid, and Moxifloxacin Regimen for Both Drug-Susceptible and Multidrug-Resistant Tuberculosis in Children: FLAME Path on the Milky Way

BACKGROUND

 The regimen of linezolid and moxifloxacin was found to be efficacious in the hollow fiber system model of pediatric intracellular tuberculosis. However, its kill rate was slower than the standard 3-drug regimen of isoniazid, rifampin, and pyrazinamide. We wanted to examine the effect of adding a third oral agent, faropenem, to this dual combination.

METHODS

 We performed a series of studies in the hollow fiber system model of intracellular Mycobacterium tuberculosis, by mimicking pediatric pharmacokinetics of each antibiotic. First, we varied the percentage of time that faropenem persisted above minimum inhibitory concentration (TMIC) on the moxifloxacin-linezolid regimen. After choosing the best faropenem exposure, we performed experiments in which we varied the moxifloxacin and linezolid doses in the triple regimen. Finally, we performed longer-duration therapy validation experiments. Bacterial burden was quantified using both colony-forming units per milliliter (CFU/mL) and time to positivity (TTP). Kill slopes were modeled using exponential regression.

RESULTS

 TTP was a more sensitive measure of bacterial burden than CFU/mL. A faropenem TMIC > 62% was associated with steepest microbial kill slope. Regimens of standard linezolid and moxifloxacin plus faropenem TMIC > 60%, as well as higher-dose moxifloxacin, achieved slopes equivalent to those of the standard regimen based by both TTP and CFU/mL over 28 days of treatment.

CONCLUSIONS

 We have developed an oral faropenem-linezolid-moxifloxacin (FLAME) regimen that is free of first-line drugs. The regimen could be effective against both multidrug-resistant and drug-susceptible tuberculosis in children.

Rapid cytolysis of Mycobacterium tuberculosis by faropenem, an orally bioavailable β-lactam antibiotic

Recent clinical studies indicate that meropenem, a β-lactam antibiotic, is a promising candidate for therapy of drug-resistant tuberculosis. However, meropenem is chemically unstable, requires frequent intravenous injection, and must be combined with a β-lactamase inhibitor (clavulanate) for optimal activity. Here, we report that faropenem, a stable and orally bioavailable β-lactam, efficiently kills Mycobacterium tuberculosis even in the absence of clavulanate. The target enzymes, L,D-transpeptidases, were inactivated 6- to 22-fold more efficiently by faropenem than by meropenem. Using a real-time assay based on quantitative time-lapse microscopy and microfluidics, we demonstrate the superiority of faropenem to the frontline antituberculosis drug isoniazid in its ability to induce the rapid cytolysis of single cells. Faropenem also showed superior activity against a cryptic subpopulation of nongrowing but metabolically active cells, which may correspond to the viable but nonculturable forms believed to be responsible for relapses following prolonged chemotherapy. These results identify faropenem to be a potential candidate for alternative therapy of drug-resistant tuberculosis.

Epileptogenic potential of carbapenem agents: mechanism of action, seizure rates, and clinical considerations

Antimicrobials are the most frequently implicated class of drugs in drug-induced seizure, with β-lactams being the class of antimicrobials most often implicated. The seizure-inducing potential of the carbapenem subclass may be directly related to their β-lactam ring structure. Data on individual carbapenems and seizure activity are scarce. To evaluate the available evidence on the association between carbapenem agents and seizure activity, we conducted a literature search of the MEDLINE (1966-May 2010), EMBASE (1974-May 2010), and International Pharmaceutical Abstracts (1970-May 2010) databases. Reference citations from the retrieved articles were also reviewed. Mechanistically, seizure propensity of the β-lactams is related to their binding to γ-aminobutyric acid (GABA) receptors. There are numerous reports of seizure activity associated with imipenem-cilastatin, with seizure rates ranging from 3-33%. For meropenem, doripenem, and ertapenem, the seizure rate for each agent is reported as less than 1%. However, as their use increases and expands into new patient populations, the rate of seizures with these agents may increase. High-dose therapy, especially in patients with renal dysfunction, preexisting central nervous system abnormalities, or a seizure history increases the likelihood of seizure activity. Although specific studies have not been conducted, data indicate that carbapenem-associated seizure is best managed with benzodiazepines, followed by other agents that enhance GABA transmission. Due to the drug interaction between carbapenems and valproic acid, resulting in clinically significant declines in valproic acid serum concentrations, the combination should be avoided whenever possible. Clinicians should be vigilant regarding the possibility of carbapenem-induced seizures when selecting and dosing antimicrobial therapy.

Treatment of acute bacterial exacerbations of chronic bronchitis

BACKGROUND

Controversies persist regarding the optimal management of patients with acute exacerbations of chronic bronchitis (AECB).

OBJECTIVE

To evaluate the available evidence on relevant issues, namely the need for administering antimicrobials in patients with AECB, the identification of the subgroup of patients with AECB needing antibiotics, the antimicrobial regimen of choice and its optimal duration, the existence of new agents, and the value of non-antimicrobial regimens for AECB.

METHODS

Data from various sources of evidence, including recent relevant meta-analyses, were appraised.

CONCLUSION

Administration of antimicrobial agents, combined with bronchodilators and systemic corticosteroids, is warranted in approximately half of AECBs (i.e., in bacterial exacerbations) to achieve a survival benefit. Simple clinical parameters, mainly sputum purulence, and biomarkers, such as procalcitonin, are useful in identifying patients requiring antibiotics. Advanced antibiotics (quinolones, macrolides, or amoxicillin/clavulanic acid) are more effective than 'old' antibiotics in AECB; regimens of short duration (for 5 days) are preferred. There is no difference between several classes of advanced antibiotics regarding their short-term effectiveness; however, quinolones are associated with better long-term outcomes than macrolides. Newer quinolones and new formulations of macrolides enrich clinicians' armamentarium against AECB.

Natural products to drugs: natural product-derived compounds in clinical trials

Natural product and natural product-derived compounds that are being evaluated in clinical trials or are in registration (as at 31st December 2007) have been reviewed, as well as natural product-derived compounds for which clinical trials have been halted or discontinued since 2005. Also discussed are natural product-derived drugs launched since 2005, new natural product templates and late-stage development candidates.