Ceftobiprole medocaril (BAL5788) treatment of experimental Haemophilus influenzae, Enterobacter cloacae, and Klebsiella pneumoniae murine pneumonia

Animal models of Klebsiella pneumoniae mucosal infections

Klebsiella pneumoniae is among the most relevant pathogens worldwide, causing high morbidity and mortality, which is worsened by the increasing rates of antibiotic resistance. It is a constituent of the host microbiota of different mucosa, that can invade and cause infections in many different sites. The development of new treatments and prophylaxis against this pathogen rely on animal models to identify potential targets and evaluate the efficacy and possible side effects of therapeutic agents or vaccines. However, the validity of data generated is highly dependable on choosing models that can adequately reproduce the hallmarks of human diseases. The present review summarizes the current knowledge on animal models used to investigate K. pneumoniae infections, with a focus on mucosal sites. The advantages and limitations of each model are discussed and compared; the applications, extrapolations to human subjects and future modifications that can improve the current techniques are also presented. While mice are the most widely used species in K. pneumoniae animal studies, they present limitations such as the natural resistance to the pathogen and difficulties in reproducing the main steps of human mucosal infections. Other models, such as Drosophila melanogaster (fruit fly), Caenorhabditis elegans, Galleria mellonella and Danio rerio (zebrafish), contribute to understanding specific aspects of the infection process, such as bacterial lethality and colonization and innate immune system response, however, they but do not present the immunological complexity of mammals. In conclusion, the choice of the animal model of K. pneumoniae infection will depend mainly on the questions being addressed by the study, while a better understanding of the interplay between bacterial virulence factors and animal host responses will provide a deeper comprehension of the disease process and aid in the development of effective preventive/therapeutic strategies.

Aerosolized delivery of ESKAPE pathogens for murine pneumonia models

Murine pneumonia models for ESKAPE pathogens serve to evaluate novel antibacterials or to investigate immunological responses. The majority of published models uses intranasal or to a limited extent the intratracheal instillation to challenge animals. In this study, we propose the aerosol delivery of pathogens using a nebulizer. Aerosol delivery typically results in homogeneous distribution of the inoculum in the lungs because of lower particle size. This is of particular importance when compounds are assessed for their pharmacokinetic and pharmacodynamic (PK/PD) relationships as it allows to conduct several analysis with the same sample material. Moreover, aerosol delivery has the advantage that it mimics the 'natural route' of respiratory infection. In this short and concise study, we show that aerosol delivery of pathogens resulted in a sustained bacterial burden in the neutropenic lung infection model for five pathogens tested, whereas it gave a similar result in immunocompetent mice for three out of five pathogens. Moreover, a substantial bacterial burden in the lungs was already achieved 2 h post inhalation. Hence, this study constitutes a viable alternative for intranasal administration and a refinement of murine pneumonia models for PK/PD assessments of novel antibacterial compounds allowing to study multiple readouts with the same sample material.

Ceftobiprole medocaril in the treatment of hospital-acquired pneumonia

Ceftobiprole medocaril is a fifth-generation cephalosporin approved in Europe as single-agent therapy for hospital-acquired pneumonia (HAP), excluding ventilator-associated pneumonia (VAP). It is rapidly converted to the active metabolite ceftobiprole following intravenous administration. Ceftobiprole has a broad spectrum of activity, notably against methicillin-resistant Staphylococcus aureus, ampicillin-susceptible enterococci, penicillin-resistant pneumococci and Enterobacteriaceae not producing extended-spectrum β-lactamase. Ceftobiprole is primarily excreted renally by glomerular filtration, with minimal propensity for interaction with co-administered drugs. Normal dose is ceftobiprole 500 mg, administered by 2-h intravenous infusion every 8 h, with dose adjustment according to renal function. In a pivotal Phase III trial in patients with HAP, ceftobiprole monotherapy was as efficacious as ceftazidime/linezolid for clinical and microbiological cure and was noninferior to ceftazidime/linezolid in the subgroup of patients with HAP excluding VAP. Ceftobiprole and ceftazidime/linezolid were similarly well tolerated. Ceftobiprole is an efficacious and well-tolerated option for empirical treatment of patients with HAP (excluding VAP).

Ceftobiprole for the treatment of pneumonia: a European perspective

Ceftobiprole, a new broad spectrum, parenteral cephalosporin, exhibits potent in vitro activity against a number of Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus and penicillin-resistant Streptococcus pneumoniae, and Gram-negative pathogens associated with hospital-acquired pneumonia (HAP) and community-acquired pneumonia (CAP). Ceftobiprole has demonstrated noninferiority in two large-scale pivotal studies comparing it to ceftriaxone with or without linezolid in CAP, with clinical cure rates 86.6% versus 87.4%, or ceftazidime in HAP, with clinical cure rates of 77% versus 76%, respectively. However, ceftobiprole was inferior in the subgroup of patients undergoing mechanical ventilation. Ceftobiprole has so far demonstrated a good safety profile in preliminary studies, with similar tolerability to comparators. The most commonly observed adverse events of ceftobiprole included headache and gastrointestinal upset. It is the first cephalosporin monotherapy approved in the EU for the treatment of both CAP and HAP (excluding ventilator-associated pneumonia).

Ceftobiprole medocaril: a review of its use in patients with hospital- or community-acquired pneumonia

Ceftobiprole, the active metabolite of the prodrug ceftobiprole medocaril (Zevtera(®)), is a new generation broad-spectrum intravenous cephalosporin with activity against methicillin-resistant Staphylococcus aureus. Ceftobiprole exhibits potent in vitro activity against a number of Gram-positive and Gram-negative pathogens associated with hospital-acquired pneumonia (HAP) and community-acquired pneumonia (CAP). It is the first cephalosporin monotherapy approved in the EU for the treatment of both HAP (excluding ventilator associated-pneumonia [VAP]) and CAP. In phase III trials, ceftobiprole medocaril was noninferior, in terms of clinical cure rates at the test-of-cure visit, to ceftazidime plus linezolid in patients with HAP and to ceftriaxone ± linezolid in patients with CAP severe enough to require hospitalization. In patients with HAP, noninferiority of ceftobiprole medocaril to ceftazidime plus linezolid was not demonstrated in a subset of patients with VAP. In patients with CAP, ceftobiprole medocaril was effective in those at risk for poor outcomes (pneumonia severity index ≥91, Pneumonia Patient Outcomes Research Team score IV-V or bacteraemic pneumonia). In the phase III trials, ceftobiprole medocaril was generally well tolerated, with ≈10 % of patients discontinuing the treatment because of adverse events. The most common treatment-related adverse events occurring in ceftobiprole recipients in the trials in patients with HAP or CAP included nausea, diarrhoea, infusion site reactions, vomiting, hepatic enzyme elevations and hyponatraemia. Therefore, ceftobiprole medocaril monotherapy offers a simplified option for the initial empirical treatment of patients with HAP (excluding VAP) and in those with CAP requiring hospitalization.

Evaluation of ceftobiprole activity against a variety of gram-negative pathogens, including Escherichia coli, Haemophilus influenzae (β-lactamase positive and β-lactamase negative), and Klebsiella pneumoniae, in a rabbit meningitis model

Ceftobiprole medocaril, a new cephalosporin, is highly active against a broad spectrum of Gram-positive and Gram-negative clinical pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) and penicillin-resistant pneumococci. In this study, we tested ceftobiprole against various Gram-negative pathogens in a rabbit meningitis model and determined its penetration into the cerebrospinal fluid (CSF). In this animal model, ceftobiprole produced an antibacterial activity similar to that of cefepime against an Escherichia coli strain, a Klebsiella pneumoniae strain, and a β-lactamase-negative Haemophilus influenzae strain. Against a β-lactamase-positive H. influenzae strain, ceftobiprole was significantly superior. The penetration of ceftobiprole through inflamed meninges reached about 16% of serum levels compared to about 2% of serum levels through uninflamed meninges.

Emerging agents to combat complicated and resistant infections: focus on ceftobiprole

Antimicrobial resistance is a global concern. Over the past few years, considerable efforts and resources have been expended to detect, monitor, and understand at the basic level the many different facets of emerging and increasing resistance. Development of new antimicrobial agents has been matched by the development of new mechanisms of resistance by bacteria. Current antibiotics act at a variety of sites within the target bacteria, including the cross-linking enzymes in the cell wall, various ribosomal enzymes, nucleic acid polymerases, and folate synthesis. Ceftobiprole is a novel parenteral cephalosporin with high affinity for most penicillin-binding proteins, including the mecA product penicillin-binding protein 2a, rendering it active against methicillin-resistant staphylococci. Its in vitro activity against staphylococci and multiresistant pneumococci, combined with its Gram-negative spectrum comparable to that of other extended-spectrum cephalosporins, its stability against a wide range of beta-lactamases, and its pharmacokinetic and safety profiles make ceftobiprole an attractive and well tolerated new antimicrobial agent. The US Food and Drug Administration granted ceftobiprole medocaril fast-track status in 2003 for the treatment of complicated skin infections and skin structure infections due to methicillin-resistant staphylococci, and subsequently extended this to treatment of hospital-acquired pneumonia, including ventilator-associated pneumonia due to suspected or proven methicillin-resistant Staphylococcus aureus.

Ceftobiprole: a new beta-lactam antibiotic

The increasing threat of antimicrobial resistance in general, and that of methicillin-resistant Staphylococcus aureus (MRSA) in particular, is raising significant medical, economical and public health challenges worldwide, both within hospitals and throughout the community. These considerations, along with the extensive time and costs associated with the development and approval of new therapeutic agents, represent some of the major reasons why understanding the advantages and limitations of new antibiotics, ensuring their judicious use and maximising their active shelf life should become global priorities. On March 18, 2008, the Food and Drug Administration issued an approvable letter for ceftobiprole, a broad-spectrum beta-lactam antibiotic active against MRSA and other clinically relevant Gram-positive and Gram-negative pathogens. Ceftobiprole is currently available only for parenteral administration, and besides its remarkable antimicrobial spectrum, this antibiotic possesses additional desirable characteristics, such as low propensity to select for resistance, efficacy in animal models of disease and good safety profile. Furthermore, in recently completed clinical trials, ceftobiprole demonstrated non-inferiority to comparator compounds such as vancomycin, and emerged as a promising clinical option of monotherapy for the treatment of complicated skin and skin structure infections and community-acquired pneumonia. Here, we discuss some of the most important clinically relevant findings on ceftobiprole obtained from in vitro studies, animal models of disease and recently completed phase III clinical trials.

In vivo pharmacodynamics of ceftobiprole against multiple bacterial pathogens in murine thigh and lung infection models

Ceftobiprole medocaril is the parenteral prodrug of ceftobiprole, a novel pyrrolidinone broad-spectrum cephalosporin with in vitro and in vivo bactericidal activities against methicillin-resistant Staphylococcus aureus (MRSA) and penicillin-resistant Streptococcus pneumoniae (PRSP). We have used murine thigh and lung infection models in neutropenic and normal mice to characterize the in vivo pharmacokinetic (PK)-pharmacodynamic (PD) activities of ceftobiprole against multiple strains of S. aureus (including MRSA), S. pneumoniae (including PRSP), and gram-negative bacilli. Serum levels of ceftobiprole following the administration of multiple doses were determined by a microbiological assay. In vivo bactericidal activities and postantibiotic effects (PAEs) of ceftobiprole against MRSA and PRSP strains were determined from serial CFU/thigh values following single doses of ceftobiprole (40 and 160 mg/kg of body weight). Dose fractionation studies were used to determine which PK-PD index correlated best with activity. Magnitudes of the PK-PD indices were calculated from MICs and PK parameters. A sigmoid dose-response model was used to estimate the dose (mg/kg/24 h) required to achieve a static and 2-log(10) kill effects over 24 h. PK results showed area under the concentration-time curve/dose values of 1.8 to 2.8 and half-lives of 0.29 to 0.51 h. MICs ranged from 0.015 to 2 microg/ml. Ceftobiprole demonstrated time-dependent killing; its in vivo PAEs varied from 3.8 h to 4.8 h for MRSA and from 0 to 0.8 h for PRSP. The time above MIC (T > MIC) correlated best with efficacy for both MRSA and PRSP. The T > MIC values required for the static doses were significantly longer (P < 0.001) for Enterobacteriaceae (36 to 45%) than for S. aureus (14 to 28%) and S. pneumoniae (15 to 22%). The drug showed activities in the lung model similar to those in the thigh model. The presence of neutrophils significantly enhanced the activity of ceftobiprole against S. pneumoniae but only slightly against Klebsiella pneumoniae. Based on its PD profile, ceftobiprole is a promising new beta-lactam agent with activity against gram-negative and gram-positive organisms including MRSA and PRSP.

Pharmacodynamic characterization of ceftobiprole in experimental pneumonia caused by phenotypically diverse Staphylococcus aureus strains

Ceftobiprole (BPR) is an investigational cephalosporin with activity against Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA) strains. The pharmacodynamic (PD) profile of BPR against S. aureus strains with a variety of susceptibility phenotypes in an immunocompromised murine pneumonia model was characterized. The BPR MICs of the test isolates ranged from 0.25 to 2 mug/ml. Pharmacokinetic (PK) studies were conducted with infected neutropenic BALB/c mice; and the BPR concentrations were measured in plasma, epithelial lining fluid (ELF), and lung tissue. PD studies with these mice were undertaken with eight S. aureus isolates (two methicillin-susceptible S. aureus strains, three hospital-acquired MRSA strains, and three community-acquired MRSA strains). Subcutaneous BPR doses of 2 to 125 mg/kg of body weight/day were administered, and the change in the number of log(10) CFU/ml in lungs was evaluated after 24 h of therapy. The PD profile was characterized by using the free drug exposures (f) determined from the following parameters: the percentage of time that the concentration was greater than the MIC (T > MIC), the maximum concentration in serum/MIC, and the area under the concentration-time curve/MIC. The BPR PK parameters were linear over the dose range studied in plasma, and the ELF concentrations ranged from 60 to 94% of the free plasma concentration. fT > MIC was the parameter that best correlated with efficacy against a diverse array of S. aureus isolates in this murine pneumonia model. The 80% effective dose (ED(80)), ED(50), and stasis exposures appeared to be similar among the isolates studied. BPR exerted maximal antibacterial effects when fT > MIC ranged from 6 to 22%, regardless of the phenotypic profile of resistance to beta-lactam, fluoroquinolone, erythromycin, clindamycin, or tetracycline antibiotics.

Evaluation of ceftobiprole medocaril against Enterococcus faecalis in a mouse peritonitis model

OBJECTIVES

Ceftobiprole is a novel broad-spectrum cephalosporin with good in vitro activity against methicillin-resistant Staphylococcus aureus and Enterococcus faecalis. The objective of this study was to assess the in vivo activity of ceftobiprole against four strains of E. faecalis, including beta-lactamase- producing (Bla+) and vancomycin-resistant strains.

METHODS

Mice were infected intraperitoneally with strains of E. faecalis: (i) the Bla+ strain HH22; (ii) two vancomycin-resistant strains (TX2484 and V583); and (iii) OG1RF (a laboratory strain), using 10 x the LD50 for each strain. Ceftobiprole doses of 25, 12.5 and 6.25 mg/kg (single doses) and ampicillin 50, 25, 12.5 and 6.25 mg/kg (single and double doses) were administered subcutaneously immediately after bacterial challenge and mice were monitored for 96 h.

RESULTS

All four E. faecalis had ceftobiprole MICs <or=0.5 mg/L. Despite being susceptible in vitro at the standard inoculum, ampicillin (single and double doses) did not protect mice against intraperitoneal challenge with Bla+ E. faecalis HH22, with a 50% protective dose (PD50) of >100 mg/kg, whereas ceftobiprole was protective (PD50 of 2 mg/kg). Ceftobiprole PD50s for vancomycin-resistant isolates TX2484 and V583 were 7.7 and 5.2 mg/kg, respectively, similar to those of single dose ampicillin (12.5 and 16.4 mg/kg, respectively). For OG1RF, both ampicillin and ceftobiprole protected all mice at doses of 25 and 12.5 mg/kg, respectively, with a PD50 of 4.2 and 8 mg/kg for ceftobiprole and ampicillin, respectively.

CONCLUSIONS

Ceftobiprole had comparable in vivo activity to that of ampicillin against vancomycin-resistant and ampicillin-susceptible strains of E. faecalis in the mouse peritonitis model. Ceftobiprole was superior in vivo to ampicillin against the Bla+ strain HH22. Our data support the further study of ceftobiprole as a therapeutic agent in humans infected with E. faecalis.

Interactions of ceftobiprole with beta-lactamases from molecular classes A to D

The interactions of ceftobiprole with purified beta-lactamases from molecular classes A, B, C, and D were determined and compared with those of benzylpenicillin, cephaloridine, cefepime, and ceftazidime. Enzymes were selected from functional groups 1, 2a, 2b, 2be, 2d, 2e, and 3 to represent beta-lactamases from organisms within the antibacterial spectrum of ceftobiprole. Ceftobiprole was refractory to hydrolysis by the common staphylococcal PC1 beta-lactamase, the class A TEM-1 beta-lactamase, and the class C AmpC beta-lactamase but was labile to hydrolysis by class B, class D, and class A extended-spectrum beta-lactamases. Cefepime and ceftazidime followed similar patterns. In most cases, the hydrolytic stability of a substrate correlated with the MIC for the producing organism. Ceftobiprole and cefepime generally had lower MICs than ceftazidime for AmpC-producing organisms, particularly AmpC-overexpressing Enterobacter cloacae organisms. However, all three cephalosporins were hydrolyzed very slowly by AmpC cephalosporinases, suggesting that factors other than beta-lactamase stability contribute to lower ceftobiprole and cefepime MICs against many members of the family Enterobacteriaceae.

Anti-MRSA beta-lactams in development, with a focus on ceftobiprole: the first anti-MRSA beta-lactam to demonstrate clinical efficacy

Ceftobiprole is the first of the investigational beta-lactam antibiotics with in vitro activity against methicillin-resistant staphylococci to reach and complete Phase III therapeutic trials. Its antibacterial spectrum includes methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, penicillin-resistant streptococci and many Gram-negative pathogens. It has demonstrated in vivo activity against many experimental infections caused by these pathogens. Ceftobiprole has completed Phase III clinical trials for complicated skin and skin structure infections, is being studied in Phase III pneumonia trials and has demonstrated non-inferiority compared with vancomycin in a Phase III complicated skin and skin structure infections trial, resulting in > 90% clinical cures of infections caused by MRSA. Other anti-MRSA beta-lactams in therapeutic clinical trials include the carbapenem CS-023/RO-4908463 and the cephalosporin ceftaroline (PPI-0903). The future of all of these agents will depend on their clinical efficacy, safety and their ability to be accepted as beta-lactams for the reliable treatment of a broad spectrum of infections, including those caused by MRSA.

Time-kill and synergism studies of ceftobiprole against Enterococcus faecalis, including beta-lactamase-producing and vancomycin-resistant isolates

Ceftobiprole (BAL9141) is an investigational cephalosporin with broad in vitro activity against gram-positive cocci, including enterococci. Ceftobiprole MICs were determined for 93 isolates of Enterococcus faecalis (including 16 beta-lactamase [Bla] producers and 17 vancomycin-resistant isolates) by an agar dilution method following the Clinical and Laboratory Standards Institute recommendations. Ceftobiprole MICs were also determined with a high inoculum concentration (10(7) CFU/ml) for a subset of five Bla producers belonging to different previously characterized clones by a broth dilution method. Time-kill and synergism studies (with either streptomycin or gentamicin) were performed with two beta-lactamase-producing isolates (TX0630 and TX5070) and two vancomycin-resistant isolates (TX2484 [VanB] and TX2784 [VanA]). The MICs of ceftobiprole for 50 and 90% of the isolates tested were 0.25 and 1 microg/ml, respectively. All Bla producers and vancomycin-resistant isolates were inhibited by concentrations of </=1 and </=4 microg/ml, respectively, at the standard inoculum concentration. Ceftobiprole MICs at a high inoculum concentration for a subset of five Bla(+) E. faecalis isolates were </=1 microg/ml. Bactericidal activity was observed against four isolates tested at concentrations as low as 1 microg/ml regardless of the production of beta-lactamase or vancomycin resistance. A combination of ceftobiprole (0.5 microg/ml) and streptomycin (25 microg/ml) was synergistic against Bla(+) TX0630 and TX5070. Ceftobiprole (0.5 microg/ml) plus gentamicin (10 microg/ml) was synergistic against VanB isolate TX2484 and showed enhanced killing, but not synergism, against TX2784 (VanA), despite the absence of high-level resistance to gentamicin. In conclusion, ceftobiprole exhibited good in vitro activity against E. faecalis, including Bla(+) and vancomycin-resistant strains, and exhibited synergism with aminoglycosides against selected isolates.

Investigational treatments for postoperative surgical site infections

Surgical site infections rank third among nosocomial infections, representing a global threat, associated with the emergence of multi-drug-resistant bacteria. The pharmaceutical industry has recently curtailed developmental programmes; however, the need for new compounds is extremely important. This article reviews new antimicrobials and immunointerventional targets for their potential to treat surgical site infections in comparison with recently licensed compounds. Daptomycin, dalbavancin, oritavancin, telavancin, iclaprim and ranbezolid seem to be promising agents against infections caused by Gram-positive pathogens and effectively address the present problems of multi-resistance in Gram-positive infections. Peptide deformylase inhibitors and immunostimulating agents open new perspectives in this field; however, very few compounds targeting Gram-negative problematic pathogens are in the pipeline of the future. Tigecycline (recently marketed) ceftobiprole, ceftaroline and doripenem seem to possess an extended anti-Gram-positive and -negative spectrum. Among these compounds, only doripenem demonstrates activity against Pseudomonas aeruginosa, for which there is a clear unmet need for new compounds, focusing on new targets.