Experimental study of LY333328 (oritavancin), alone and in combination, in therapy of cephalosporin-resistant pneumococcal meningitis

New Antibiotics for the Treatment of Nosocomial Central Nervous System Infections

Nosocomial central nervous system (CNS) infections with carbapenem- and colistin-resistant Gram-negative and vancomycin-resistant Gram-positive bacteria are an increasing therapeutic challenge. Here, we review pharmacokinetic and pharmacodynamic data and clinical experiences with new antibiotics administered intravenously for the treatment of CNS infections by multi-resistant bacteria. Cefiderocol, a new siderophore extended-spectrum cephalosporin, pharmacokinetically behaves similar to established cephalosporins and at high doses will probably be a valuable addition in our therapeutic armamentarium for CNS infections. The new glycopeptides dalbavancin, telavancin, and oritavancin are highly bound to plasma proteins. Although effective in animal models of meningitis, it is unlikely that they reach effective cerebrospinal fluid (CSF) concentrations after intravenous administration alone. The β-lactam/β-lactamase inhibitor combinations have the principal problem that both compounds must achieve adequate CSF concentrations. In the commercially available combinations, the dose of the β-lactamase inhibitor tends to be too low to achieve adequate CSF concentrations. The oxazolidinone tedizolid has a broader spectrum but a less suitable pharmacokinetic profile than linezolid. The halogenated tetracycline eravacycline does not reach CSF concentrations sufficient to treat colistin-resistant Gram-negative bacteria with usual intravenous dosing. Generally, treatment of CNS infections should be intravenous, whenever possible, to avoid adverse effects of intraventricular therapy (IVT). An additional IVT can overcome the limited penetration of many new antibiotics into CSF. It should be considered for patients in which the CNS infection responds poorly to systemic antimicrobial therapy alone.

Oritavancin: a long-acting antibacterial lipoglycopeptide

Oritavancin is a new lipoglycopeptide antibacterial agent with an exceptionally long terminal half-life and a rapid bactericidal effect. Multiple mechanisms of action lead to a broad activity against Gram-positive bacteria, such as staphylococci, streptococci and enterococci, including methicillin-resistant Staphylococcus aureus. Its long terminal half-life allows for single-dose treatment of acute bacterial skin and skin structure infections. Oritavancin was found to be safe and effective in treating acute bacterial skin and skin structure infections in adults and it is currently approved in the USA and in Europe for this indication. Unfortunately, data for other indications are lacking. Here, we review chemistry, microbiology, pharmacology, efficacy and tolerability of oritavancin.

Oritavancin Pharmacokinetics and Bone Penetration in Rabbits

The pharmacokinetics and bone concentrations of oritavancin were investigated after a single intravenous dose was administered to rabbits. The pharmacokinetic profile of oritavancin in rabbits showed that it is rapidly distributed to bone tissues, with concentrations remaining stable for up to 168 h, the last measured time point. Based on these findings, further evaluation of oritavancin for the treatment of infections in bone tissues is warranted.

Glycopeptide antibiotics: evolving resistance, pharmacology and adverse event profile

The first glycopeptide antibiotic was vancomycin, isolated from the soil in the 1950s; since then, the class has expanded to include teicoplanin and the new semisynthetic glycopeptides dalbavancin, oritavancin and telavancin. They are bactericidal, active against most Gram-positive organisms, and in a concentration-dependent manner, inhibit cell wall synthesis. Resistance to vancomycin has emerged, especially among enterococci and Staphylococcus aureus through a variety of mechanisms. This emerging resistance to vancomycin makes proper dosing and monitoring of the area under the curve/MIC critically important. The chief adverse effect of vancomycin is nephrotoxicity, which is also intricately related to its dose. The efficacy of the semisynthetic glycopeptides has been demonstrated in skin and soft-tissue infections, but remains to be seen in serious methicillin-resistant Staphylococcus aureus infections.

Profile of oritavancin and its potential in the treatment of acute bacterial skin structure infections

Oritavancin, a semisynthetic derivative of the glycopeptide antibiotic chloroeremomycin, received the US Food and Drug Administration approval for the treatment of acute bacterial skin and skin structure infections caused by susceptible Gram-positive bacteria in adults in August 2014. This novel second-generation semisynthetic lipoglycopeptide antibiotic has activity against a broad spectrum of Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-intermediate S. aureus (VISA), and vancomycin-resistant Enterococcus. Oritavancin inhibits bacterial cell wall synthesis and is rapidly bactericidal against many Gram-positive pathogens. The long half-life of this drug enables a single-dose administration. Oritavancin is not metabolized in the body, and the unchanged drug is slowly excreted by the kidneys. In two large Phase III randomized, double-blind, clinical trials, oritavancin was found to be non-inferior to vancomycin in achieving the primary composite end point in the treatment of acute Gram-positive skin and skin structure infections. Adverse effects noted were mostly mild with nausea, headache, and vomiting being the most common reported side effects. Oritavancin has emerged as another useful antimicrobial agent for treatment of acute Gram-positive skin and skin structure infections, including those caused by MRSA and VISA.

Oritavancin: A Long-Half-Life Lipoglycopeptide

Oritavancin is a lipoglycopeptide antibiotic that has been shown to be effective for the treatment of acute bacterial skin and skin structure infections (ABSSSIs). This antibiotic has multiple mechanisms of action including inhibiting peptidoglycan cell wall synthesis and disrupting bacterial cell membrane, leading to cell death. Oritavancin is highly active against common gram-positive pathogens including methicillin-resistant Staphylococcus aureus, vancomycin-intermediate S. aureus, vancomycin-resistant S. aureus, and vancomycin-resistant enterococci. The drug is administered as a single intravenous dose of 1200 mg over 3 hours in adult patients, and because of its terminal half-life of 393 hours, repeat dosing is not required in the treatment of ABSSIs. There is a very slow elimination from tissue sites, and no dosing adjustments are required for renal or hepatic insufficiency. Two clinical trials have demonstrated noninferiority compared with vancomycin in the treatment of ABSSSIs. Other than liver enzyme elevation and the occurrence of osteomyelitis, oritavancin has been associated with adverse events similar to those of vancomycin in follow-up for up to 60 days. Patients should be monitored for osteomyelitis and alternate therapy given in the case of confirmed or suspected osteomyelitis. Although oritavancin is an attractive antibiotic to consider in the outpatient area, its efficacy and safety in the treatment of other sites of infection are yet to be established.

Oritavancin: a new avenue for resistant Gram-positive bacteria

Oritavancin, a new semisynthetic glycopeptide has a spectrum of activity similar to vancomycin, although it exhibits potent antimicrobial activity against vancomycin-resistant staphylococci and enterococci species. It has a long-terminal half-life of 360 h, is highly protein bound and has been dosed once-daily in clinical trials. Oritavancin has been studied in complicated skin and skin structure infections where it was noninferior to the comparator group of vancomycin/cephalexin. Thus far, oritavancin has a favorable side-effect profile and appears promising in the treatment of multidrug resistant Gram-positive bacteria.

Treatment and prevention strategies to combat pediatric pneumococcal meningitis

Pneumococcal meningitis is a severe, life-threatening infection of the nervous system affecting infants, children and adults alike. The incidence of pneumococcal meningitis in infants and children less than 2 years of age in Europe is approximately 10 out of 100,000 per year, rising to approximately 148 out of 100,000 per year in Gambian infants. The use of highly sensitive tests such as PCR may increase the likelihood of detecting the infection by 20% or more. Epidemics of serotype 1 pneumococcal meningitis in northern Ghana, have had many of the characteristics of meningococcal meningitis epidemics. Neurologic sequelae may occur in 28-63% of cases, and serotype 3 is associated with a 2.54 relative risk of death. The pathogenic process can be divided into invasion, inflammatory pathways, bacterial toxicity and damage; pneumolysin being particularly associated with apoptosis. In the future, neuroprotection may be achieved, targeting this process at all these levels. Therapeutic guidelines have been published by the Infectious Diseases Society of America. Standard empiric therapy, in those aged greater than or equal to 1 month, is a third-generation cephalosporin plus vancomycin. There is insufficient evidence relating to the use or otherwise of corticosteroids in pneumococcal meningitis to make a firm recommendation. The advent of a pneumococcal conjugate vaccine is the most powerful tool available for the prevention of pneumococcal meningitis in all parts of the world.

Treatment of Drug-resistant Pneumococcal Meningitis

The approach to therapy in patients with pneumococcal meningitis has changed considerably over the past 20 years. Given the emergence of pneumococcal strains that are intermediately susceptible or highly resistant to penicillin, penicillin is not recommended as empiric therapy for presumed pneumococcal meningitis; the combination of vancomycin and a third-generation cephalosporin (either cefotaxime or ceftriaxone) should be used, pending isolation of the organism and in vitro susceptibility testing. For patients with pneumococcal meningitis caused by highly penicillin- or cephalosporin-resistant strains, the addition of rifampin can be considered if the organism is susceptible in vitro, the expected clinical or bacteriologic response is delayed, or the pneumococcal isolate has a cefotaxime or ceftriaxone minimal inhibitory concentration greater than 4 μg/mL. Meropenem is not a good option for monotherapy of highly penicillin- or cephalosporin-resistant strains, but use of a fluoroquinolone with in vitro activity against Streptococcus pneumoniae (specifically moxifloxacin) is an option in patients failing standard therapy; if used, however, it should be combined with a third-generation cephalosporin or vancomycin. Newer glycopeptides, daptomycin, and linezolid require further study to determine their efficacy in patients with pneumococcal meningitis.

Oritavancin: a novel lipoglycopeptide active against Gram-positive pathogens including multiresistant strains

Oritavancin is a lipoglycopeptide antibiotic under investigation for the treatment of serious infections caused by Gram-positive bacteria. Oritavancin has demonstrated rapid dose-dependent bactericidal activity towards vancomycin-susceptible and -resistant enterococci, meticillin-susceptible and -resistant Staphylococcus aureus, vancomycin-intermediate S. aureus (VISA), heteroresistant VISA (hVISA), vancomycin-resistant S. aureus (VRSA) and small-colony variants of S. aureus. It is also active against Clostridium difficile. Upon intravenous administration, oritavancin displays a three-compartment pharmacokinetic model, dose proportionality, a distribution volume of ca. 110 L, a terminal elimination half-life in excess of 2 weeks and it is not metabolised. Its pharmacodynamic properties make it an ideal antibiotic for a once-daily or even single-dose regimen. Oritavancin is currently under review by the US Food and Drug Administration. So far, oritavancin has demonstrated efficacy in two pivotal Phase III trials conducted in patients with complicated skin and skin-structure infections in which oritavancin was compared with vancomycin plus cefalexin. In both trials, the primary endpoint (clinical cure in clinically evaluable patients at first follow-up with a 10% non-inferiority margin) was met, with the advantages of shorter duration of therapy and fewer adverse events. Further results indicating its activity against bacteria growing in biofilms as well as stationary-phase bacteria open the way for its use to treat prosthetic device infections, which is to be investigated in upcoming trials.

Strategies and new developments in the management of bacterial meningitis

The principles of antimicrobial therapy for acute bacterial meningitis include use of agents that penetrate well into cerebrospinal fluid and attain appropriate cerebrospinal fluid concentrations, are active in purulent cerebrospinal fluid, and are bactericidal against the infecting pathogen. Recommendations for treatment of bacterial meningitis have undergone significant evolution in recent years, given the emergence of pneumococcal strains that are resistant to penicillin. Clinical experience with use of newer agents is limited to case reports, but these agents may be necessary to consider in patients who are failing standard therapy.

New antimicrobial agents for use in the intensive care unit

Timely provision of adequate antimicrobial coverage in an initial anti-infective treatment regimen results in optimal outcomes for bacterial and fungal infections. However, selection of appropriate antimicrobial regimens for treatment of infections in the intensive care unit (ICU) can be challenging due to expansion of resistance, which typically requires use of multidrug anti-infective regimens to provide adequate coverage of important pathogens commonly seen in the ICU setting. Indeed, a recent additional call to action by the Infectious Diseases Society of America (IDSA) has enforced the impact that antimicrobial-resistant pathogens can have on patient care. The term ESKAPE has been coined by this IDSA group to refer to Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa, and Enterobacter species, the etiologic causes of the majority of hospital-acquired infections in the United States that are able to effectively "escape" our antibiotic arsenal and that also mandate discovery of new antimicrobial agents. This article reviews select antibacterial agents and an antifungal agent in late stages of clinical development that appear to have potential for treatment of infections in the ICU.

[Presumptive bacterial meningitis in adults: initial antimicrobial therapy]

CSF sterilization should be obtained very rapidly to reduce both mortality and morbidity due to bacterial meningitis. Thus, antibiotic treatment should be adapted to the suspected bacterium and administered as early as possible at high dosage with - if necessary - a loading dose and continuous perfusion. The rates of abnormal susceptibility to penicillin of Streptococcus pneumoniae, Neisseria meningitis and Haemophilus influenzae are 37%, 30% and 12% respectively. Thus, ceftriaxone or cefotaxim must be used as empirical treatment. Listeria monocytogenes remains fully susceptible to aminopenicillin, so, the combination aminopenicillin and aminoglycoside is the first-line treatment. Antibiotic resistance, allergy or contra-indications, are in fact rare but in these cases, antibiotic combinations are often needed. The latter are more or less complex and clinically validated; they include molecules such as vancomycine, fosfomycin, fluoroquinolone or linezolid.

[Antibiotic management of presumptive bacterial meningitis in adults (rational, methods, course, and follow-up)]

The annual incidence of community acquired meningitis ranges between 0.6 and four per 100,000 adults in industrialized countries. The most common causative bacteria are Streptococcus pneumoniae, Neisseria meningitidis, Listeria monocytogenes. The emergence of resistance to antibiotics, especially for S. pneumoniae, could explain the clinical failure of third generation cephalosporins used to treat adults with S. pneumoniae meningitis. The present therapeutic suggestions are more based on the extrapolation of an experimental model than on relevant clinical trials.

Oritavancin: a potential weapon in the battle against serious Gram-positive pathogens

Oritavancin is a lipoglycopeptide antibiotic with activity against aerobic and anaerobic Gram-positive bacteria. Oritavancin separates itself from other glycopeptides through its potent in vitro activity against resistant isolates of Staphylococcus aureus, Enterococcus spp. and Streptococcus spp. Oritavancin possesses a long half-life that should allow, at maximum, once-daily dosing. Currently, oritavancin has completed two Phase III trials and one Phase II trial for the treatment of complicated skin and skin structure infections, and two Phase II trials for the treatment of Gram-positive bacteremia. In all instances, oritavancin displayed favorable outcomes and was noninferior to comparator agents (vancomycin followed by oral cephalexin) when a comparison was made. Further studies are necessary to fully characterize dose and clinical role.

Pharmacologic options for CNS infections caused by resistant Gram-positive organisms

Infectious disease continues to evolve, presenting new and challenging clinical situations for practitioners. Specific to device-related and neurosurgical-related CNS infections, Gram-positive organisms are of growing concern. Current Infection Disease Society of America guidelines for the treatment of CNS infections offer little direction after conventional therapy, consisting of vancomycin, has failed or the patient has demonstrated intolerance. A review of literature evaluating alternative therapies, specifically linezolid, quinupristin/dalfopristin, daptomycin and tigecycline, will be presented. Interpretations of these data are offered followed by a brief presentation of future therapies, including ortavancin, telavancin, dalbavancin, ceftobiprole and iclaprim, all of which possess potent Gram-positive activity.

Investigational new drugs for the treatment of resistant pneumococcal infections

Antibiotic resistance in Streptococcus pneumoniae is not only increasing with penicillin but also with other antimicrobial classes including the macrolides, tetracyclines and sulfonamides. This trend with antibiotic resistance has highlighted the need for the further development of new anti-infectives for the treatment of pneumococcal infections, particularly against multi-drug resistant pneumococci. Several new drugs with anti-pneumococcal activity are at various stages of development and will be discussed in this review. Two new cephalosporins with activity against S. pneumoniae include ceftobiprole and RWJ-54428. Faropenem is in a new class of beta-lactam antibiotics called the penems. Structurally, the penems are a hybrid between the penicillins and cephalosporins. Sitafloxacin and garenoxacin are two new quinolones that are likely to have a role in treating pneumococcal infections. Oritavancin and dalbavancin are glycopeptides with activity against methicillin-resistant S. aureus and vancomycin-resistant Enterococcus spp. as well as multi-drug resistant pneumococci. Tigecycline is the first drug in a new class of anti-infectives called the glycycyclines that has activity against penicillin-resistant pneumococci.

Oritavancin – an investigational glycopeptide antibiotic

Antibiotics save countless lives each year; however, increasing rates of drug-resistant bacteria have limited antibiotic selection. Currently, there are few available options for treating resistant Gram-positive organisms. Oritavancin, a novel glycopeptide antibiotic with bactericidal activity, has been developed and recently completed the first round of Phase III clinical trials for the treatment of complicated skin and skin structure infections. Investigations into oritavancin's efficacy will be explored in catheter-related bacteraemia and nosocomial pneumonia. Oritavancin demonstrates similar activity to vancomycin but possesses extended activity against vancomycin-resistant Staphylococcus and Enterococcus. The pharmacokinetics and pharmacodynamics of oritavancin appear to be favourable and once-daily dosing is likely. The incidence of multi-drug resistant bacteria is increasing and explorations into additional treatment options are essential. Further development of oritavancin is necessary to determine clinical efficacy.

Experimental study of teicoplanin, alone and in combination, in the therapy of cephalosporin-resistant pneumococcal meningitis

OBJECTIVES

The aim of the study was to determine the efficacy of teicoplanin, alone and in combination with ceftriaxone, in a rabbit model of cephalosporin-resistant pneumococcal meningitis, and to assess the effect of concomitant therapy with dexamethasone.

METHODS

In vitro killing curves of teicoplanin, with and without ceftriaxone, were performed. Groups of eight animals per treatment were inoculated with a cephalosporin-resistant pneumococcal strain (penicillin MIC, 4 mg/L; ceftriaxone MIC, 2 mg/L; teicoplanin MIC, 0.03 mg/L) and treated over a 26 h period. Teicoplanin was administered at a dose of 15 mg/kg, alone and in combination with ceftriaxone at 100 mg/kg with or without dexamethasone at 0.25 mg/kg. CSF samples were collected at different time-points, and bacterial titres, white blood cell counts, lactate and protein concentrations and bacteriostatic/bactericidal titres were determined. Blood and CSF teicoplanin pharmacokinetic and pharmacodynamic parameters were determined.

RESULTS

Teicoplanin alone promoted a decrease in bacterial counts at 6 h of -2.66 log cfu/mL and was bactericidal at 24 h, without therapeutic failures. Similar good results were obtained when dexamethasone was used simultaneously, in spite of the penetration of teicoplanin into the CSF being significantly reduced, from 2.31% to 0.71%. Teicoplanin and ceftriaxone combinations were synergic in vitro, but not in the meningitis model.

CONCLUSIONS

Teicoplanin alone was very effective in this model of cephalosporin-resistant pneumococcal meningitis. The use of concomitant dexamethasone resulted in lower CSF teicoplanin levels, but not in therapeutic failures. The combination of teicoplanin plus ceftriaxone and dexamethasone might be a good alternative for the empirical therapy of pneumococcal meningitis. Additional data should confirm our experiments, in advance of clinical trials to assess efficacy in humans.

New therapies for pneumococcal meningitis

The treatment of pneumococcal meningitis remains a major challenge, as reflected by the continued high morbidity and case fatality of the disease. The worldwide increase of penicillin-resistant pneumococci and more recently cephalosporin- and vancomycin-tolerant pneumococci has jeopardised the efficacy of standard treatments based on extended spectrum cephalosporins alone or in combination with vancomycin. This review provides a summary of newly developed antibiotics tested in the rabbit meningitis model. In particular, newer beta-lactam monotherapies (cefepime, meropenem, ertapenem), recently developed quinolones (garenoxacin, gemifloxacin, gatifloxacin, moxifloxacin) and a lipopeptide antibiotic (daptomycin) are discussed. A special emphasis is placed on the potential role of combination treatments with some of the new compounds, which are of interest based on the background of increasing resistance problems due to their often synergistic activity in the rabbit model of pneumococcal meningitis.

Glycopeptide Antibiotics

Vancomycin and teicoplanin are still the only glycopeptide antibiotics available for use in humans. Emergence of resistance in enterococci and staphylococci has led to restriction of their use to severe infections caused by Gram-positive bacteria for which no other alternative is acceptable (because of resistance or allergy). In parallel, considerable efforts have been made to produce semisynthetic glycopeptides with improved pharmacokinetic and pharmacodynamic properties, and with activity towards resistant strains. Several molecules have now been obtained, helping to better delineate structure-activity relationships. Two are being currently evaluated for skin and soft tissue infections and are in phases II/III. The first, oritavancin (LY333328), is the 4'-chlorobiphenylmethyl derivative of chloroeremomycin, an analogue to vancomycin. It is characterised by: i) a spectrum covering vancomycin-resistant enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA) and to some extent glycopeptide-intermediate S. aureus (GISA); ii) rapid bactericidal activity including against the intracellular forms of enterococci and staphylococci; and iii) a prolonged half-life, allowing for daily administration. The second molecule is dalbavancin (BI397), a derivative of the teicoplanin analogue A40926. Dalbavancin has a spectrum of activity similar to that of oritavancin against vancomycin-sensitive strains, but is not active against VRE. It can be administered once a week, based on its prolonged retention in the organism. Despite these remarkable properties, the use of these potent agents should be restricted to severe infections, as should the older glycopeptides, with an extension towards resistant or poorly sensitive bacteria, to limit the risk of potential selection of resistance.