Antistaphylococcal activity of dalbavancin, an experimental glycopeptide

Multidose Dalbavancin Population Pharmacokinetic Analysis for Prolonged Target Attainment in Patients Requiring Long-Term Treatment

Introduction: Dalbavancin (DAL) is a long-acting lipoglycopeptide active against Gram-positive bacteria, including multidrug-resistant isolates. A growing body of evidence supports its efficacy in various difficult-to-treat infections. DAL shows time-dependent bactericidal activity in vitro at free drug concentrations equal to 4×MIC values. However, the optimal dosing scheme for achieving the PK/PD target in multidose treatment has not been fully established. Methods: Pharmacokinetic analysis was based on a nonlinear mixed effects modelling approach performed in NONMEM v7.5/Pirana, while R was used for data management and graphical summaries. Final model parameters were used to simulate the plasma disposition of DAL by Monte Carlo simulations to determine the multidose DAL regimen associated with a 90% target attainment of 100% fT > 4×MIC. Results: A two-compartmental model with first-order elimination and allometric-scaled bodyweight best described DAL disposition in patients with CLcr > 30 mL/min. Monte Carlo simulations showed that two 1500 mg DAL doses 7 days apart granted an optimal PTA > 90% of 100% fT > 4×MIC up to 5, 4, and 3 weeks in patients weighting from 40-80 kg, 80-120 kg and 120-200 kg, respectively. An additional third 1500 mg dose at the above time points by weight bands may extend the optimal PTA up to 9, 7, and 6 weeks of total treatment. Conclusions: Two 1500 mg DAL doses administered 7 days apart could be a valuable starting strategy for patients of all weight classes with CLcr > 30 mL/min. In patients requiring long-term DAL treatment, the optimal timing of additional administrations should be guided by routine TDM or empirically through patients' total body weight when TDM is unavailable.

Long-Acting Antibiotics: New Opportunities Beyond Acute Bacterial Skin and Skin Structure Infections (ABSSSIs)!

Currently, two long-acting antibiotics are available: oritavancin (ORI) and dalbavancin (DBV) [...].

Liquid Chromatography-Tandem Mass Spectrometry Method for Therapeutic Drug Monitoring of Dalbavancin in Plasma of Pediatric and Young Adult Patients

BACKGROUND

Dalbavancin, an antimicrobial lipoglycopeptide, is authorized in Europe for treating acute bacterial infections of the skin and skin structures in adults and pediatric patients aged 3 months and older. However, off-label dosing regimens have been proposed for various indications beyond acute bacterial infections of the skin and skin structures. This study presents a novel bioanalytical method using liquid chromatography-tandem mass spectrometry to quantify dalbavancin in low-volume plasma samples (50 μL).

METHODS

The method underwent validation in accordance with international guidelines for bioanalytical method validation and was applied to 9 clinical samples obtained from pediatric and young adult patients undergoing dalbavancin therapy. Liquid chromatography-tandem mass spectrometry analyses were conducted at the G. Gaslini Institute in Genoa, Italy, utilizing an Ultimate 3000 ultra high performance liquid chromatography system coupled to a TSQ Quantiva Triple Quadrupole system (Thermo Fisher Scientific, Milan, Italy). The analytical procedure involved the addition of deuterated dalbavancin as internal standard and a rapid extraction from 50 µL of human plasma, followed by chromatographic separation on a Thermo Scientific Accucore Polar Premium column. Accurate quantification of the analyte was achieved through multiple reaction monitoring detection.

RESULTS

The assay exhibited linearity within the concentration range of 0.66-400 mcg/mL in plasma, demonstrating accuracy and reproducibility in the absence of matrix effects. Stability testing was conducted on both quality controls and real samples to establish a robust protocol under real-life conditions.

CONCLUSIONS

This fast and reliable dalbavancin quantitation method could improve current pediatric clinical practice by enabling data collection for future dose recommendations in special patient populations.

Bayesian prediction-based individualized dosing of anti-methicillin-resistant Staphylococcus aureus treatment: Recent advancements and prospects in therapeutic drug monitoring

As one of the efficient techniques for TDM, the population pharmacokinetic (popPK) model approach for dose individualization has been developed due to the rapidly growing innovative progress in computer technology and has recently been considered as a part of model-informed precision dosing (MIPD). Initial dose individualization and measurement followed by maximum a posteriori (MAP)-Bayesian prediction using a popPK model are the most classical and widely used approach among a class of MIPD strategies. MAP-Bayesian prediction offers the possibility of dose optimization based on measurement even before reaching a pharmacokinetically steady state, such as in an emergency, especially for infectious diseases requiring urgent antimicrobial treatment. As the pharmacokinetic processes in critically ill patients are affected and highly variable due to pathophysiological disturbances, the advantages offered by the popPK model approach make it highly recommended and required for effective and appropriate antimicrobial treatment. In this review, we focus on novel insights and beneficial aspects of the popPK model approach, especially in the treatment of infectious diseases with anti-methicillin-resistant Staphylococcus aureus agents represented by vancomycin, and discuss the recent advancements and prospects in TDM practice.

Validation and Clinical Application of a New Liquid Chromatography Coupled to Mass Spectrometry (HPLC-MS) Method for Dalbavancin Quantification in Human Plasma

Dalbavancin (DBV) is an intravenous long-acting second-generation glycolipopeptide antibiotic with high efficacy and excellent tolerability, approved for use in the treatment of Gram-positive skin and skin structure infections (ABSSSI). Nevertheless, little is known about its pharmacokinetic/pharmacodynamic (PK/PD) properties in real life, which is also due to technical challenges in its quantification in human plasma, preventing an effective application of therapeutic drug monitoring (TDM). In fact, DBV has a high affinity to plasma proteins, possibly resulting in poor recovery after extraction procedure. The aim of this study was to validate a simple, cheap and reliable HPLC-MS method for use in TDM, in accordance with FDA and EMA guidelines. The optimized protein precipitation protocol required 50 μL of plasma, while chromatographic analysis could be performed in 12 min/sample. This method fulfilled the guidelines requirements and then, it was applied for routine DBV TDM in patients receiving off-label high doses (two 1500 + 1500 mg weekly infusions instead of 1000 + 500 mg), with normal renal function or undergoing hemodialysis: continuous hemodiafiltration caused a relevant reduction in DBV exposure, while intermittent dialysis showed comparable DBV concentrations with those of patients with normal renal function. This confirmed the eligibility of the presented method for use in TDM and its usefulness in clinical practice.

Long-Term Pharmacokinetics of Dalbavancin in ABSSSI and Osteoarticular Settings: A Real-Life Outpatient Context

Dalbavancin is a lipoglycopeptide approved for treatment of Gram-positive infections of skin and skin-associated structures (ABSSSI). Currently, off-label use at high dosages for osteoarticular infections deserves attention. This work aimed to study the long-term plasma pharmacokinetics of dalbavancin in outpatients with ABSSSI or osteoarticular infections, treated either with one or two 1500 mg doses of dalbavancin. A liquid chromatography-tandem mass spectrometry method was used to measure total dalbavancin concentrations in plasma samples. The results were analyzed through a non-compartmental analysis (NCA). Breakpoint minimum inhibitory concentration (MIC) was used to calculate AUC/MIC and T > MIC parameters, adjusted by 93% protein binding. A total of 14 patients were enrolled, 11 with osteoarticular infection and 3 with ABSSSI. Long-term pharmacokinetics showed median T > MIC (0.125 mg/L) of 11.9 and 13.7 weeks for single and dual dose, respectively. Similarly, median AUC_0-2w/MIC ratios of 20,590 and 31,366 were observed for single and dual dose regimens, respectively. No adverse events were observed, and treatment success was achieved in 12/14 patients. Failure was associated with the worst clinical conditions, bone infections, and single dose. The results of this study show that dalbavancin exposure exceeds previously suggested pharmacodynamic targets. Optimization of these targets is needed for the osteoarticular setting.

Review: A Safety Profile of Dalbavancin for On- and Off-Label Utilization

Introduction

Dalbavancin is a bactericidal lipoglycopeptide active against gram-positives. Its use has been approved for the treatment of acute bacterial skin and skin structure infections (ABSSSI).

Methods

We conducted a narrative review of the literature on the safety profile of dalbavancin. The bibliographic research was carried out on the PubMed database on 6 November 2020 by seeking combinations of the following keywords: dalbavancin, adverse effects, safety, drug interactions, and skin infections.

Results

Five double-blind Phase 3 randomized clinical trials, 2 open-label randomized trials, and 4 retrospective studies were identified. No statistically significant differences were found between dalbavancin and comparators in the incidence of adverse events. Retrospective studies confirm the low incidence of adverse events.

Conclusion

Dalbavancin is a therapeutic option that has demonstrated an excellent safety profile, also in relation to the other MRSA therapies available. Its use represents a cost-effective solution for the treatment of those patients with ABSSSI who would need hospitalization. One limitation of this study is that most of the available data are from Phase III clinical trials. Further real-life studies with a larger sample size are therefore needed to better assess the safety profile of the dalbavancin, especially to investigate the true incidence of rare adverse events.

Dalbavancin for the Treatment of Complicated Gram-Positive Skin and Soft Tissue Infections

New antimicrobial agents have been developed to treat infections caused by methicillin-resistant Staphylococcus aureus and other multidrug-resistant pathogens. Dalbavancin is a novel semisynthetic lipoglycopeptide antibiotic, particularly active against methicillin-resistant Staphylococcus aureus. Due to its unique pharmacological characteristics and longer half-life, it can be administered once-weekly or every 15 days and in outpatient setting. Currently, it is indicated for complicated skin and soft tissue infections, but accumulating evidence points to its off-label efficacy in osteomyelitis and endocarditis. Further experience is still needed to increase our knowledge on the role of dalbavancin in a wider range of Gram-positive infections requiring prolonged antimicrobial treatment.

Intravenous and Intraperitoneal Pharmacokinetics of Dalbavancin in Peritoneal Dialysis Patients

Dalbavancin offers a possible treatment option for infectious peritonitis associated with peritoneal dialysis (PD) due to its coverage of Gram-positive bacteria and pharmacokinetic properties. We aimed to evaluate the clinical pharmacokinetics (PK) and pharmacodynamics of dalbavancin in a prospective, randomized, open-label, crossover PK study of adult patients with end-stage renal disease ESRD who were receiving PD. Sampling occurred prior to a single 30-min infusion of dalbavancin at 1,500 mg and at 1, 2, 3, 4, and 6 h and 7 and 14 days postadministration. Concentration-time data were analyzed via noncompartmental analysis. Pharmacodynamic parameters against common infectious peritonitis-causing pathogens were evaluated. Ten patients were enrolled. Patients were a median of 55 years old and had a median weight of 78.2 kg, 50% were female, and 70% were Caucasian. The terminal plasma half-life of dalbavancin was 181.4 ± 35.5 h. The day 0 to day 14 dalbavancin mean area under the curve (AUC) was 40,573.2 ± 9,800.3 mg·h/liter. The terminal-phase half-life of dalbavancin within the peritoneal fluid was 4.309 × 10⁸ ± 1.140 × 10⁹ h. The day 0 to day 14 dalbavancin mean peritoneal fluid AUC was 2,125.0 ± 1,794.3 mg·h/liter. The target plasma AUC/MIC was attained with the intravenous dose in all 10 patients for all Staphylococcus and Streptococcus species at the recommended MIC breakpoints. The intraperitoneal arm of the study was stopped early, because the first 3 patients experienced moderate to severe pain and bloating within 1 h following the administration of dalbavancin. Dalbavancin at 1,500 mg administered intravenously can be utilized without dose adjustment in peritoneal dialysis patients and will likely achieve the necessary peritoneal fluid concentrations to treat peritonitis caused by typical Gram-positive pathogens.

Efficacy of Dalbavancin and Telavancin in the Treatment of Acute Bacterial Skin and Skin Structure Infections

Objectives

Two glycopeptide analogues, such as dalbavancin and telavancin, with improved pharmacokinetic/pharmacodynamic parameters have been developed. These two glycopeptide analogues are approved by Food and Drug Administration (FDA) for treatment of various Gram-positive bacterial skin infections.

Materials and methods

We have conducted an open labelled prospective randomized study to compare the efficacy of these two drugs. A total of 200 patients diagnosed with acute bacterial skin and skin structure infections (ABSSSI) were recruited for the study. They were randomized to receive either a single dose of dalbavancin 1500 mg i.v (Group I) or telavancin 10 mg/kg intravenously (i.v.) every 24 hours for six days (Group II). The skin infection rating score (SIRS) was calculated on Day 0 for all patients at the time of diagnosis. Signs and symptoms of the lesions were assessed based on the following factors: blistering, exudate/pus, erythema/inflammation and itching/pain. Each factor was classified as one of the following: absent - 0, minimal - 1, moderate - 2 and severe - 3.

Results

Clinically successful treatment was defined as complete resolution of clinically meaningful signs and symptoms of infection, including SIRS score of 0. The outcome measure was the percentage of patients with SIRS score of 0 on day 7 (clinical success). The third most common diagnosis at baseline was impetigo (13% in both groups). Patients who received dalbavancin had a higher clinical success rate than those receiving telavancin.

Conclusion

Findings of the present study show that single i.v dose of dalbavancin is better than telavancin repeated doses in treatment of ABSSSI.

Newer glycopeptide antibiotics for treatment of complicated skin and soft tissue infections: systematic review, network meta-analysis and cost analysis

OBJECTIVES

Skin and soft tissue infections (SSTIs) carry significant economic burden, as well as morbidity and mortality, especially when caused by methicillin-resistant Staphylococcus aureus (MRSA). Several new MRSA-active antibiotics have been developed, including semisynthetic glycopeptides (telavancin, dalbavancin and oritavancin). Of these, dalbavancin and oritavancin offer extended dosing intervals.

METHODS

We performed a systematic review, network meta-analysis and cost analysis to compare the newer glycopeptides to standard care and to each other for the treatment of complicated SSTIs (cSSTI). A search for randomized controlled trials (RCTs) was conducted in Medline, Embase and the Cochrane Central Register of Controlled Trials. We also developed a model to evaluate the costs associated with dalbavancin and oritavancin from the third-party payer perspective.

RESULTS

Seven RCTs met the inclusion criteria. Network meta-analyses suggested that the clinical response to telavancin, dalbavancin and oritavancin was similar to standard care (odds ratio (OR) 1.09, 95% confidence interval (CI) 0.90-1.33; OR 0.78, 95% CI 0.52-1.18; and OR 1.06, 95% CI 0.85-1.33, respectively). Head-to-head comparisons showed no difference in clinical response between oritavancin and dalbavancin (OR 1.36; 95% CI 0.85-2.18), oritavancin and telavancin (OR 0.98; 95% CI 0.72-1.31) or dalbavancin and telavancin (OR 0.72; 95% CI 0.45-1.13). Telavancin had a higher incidence of overall adverse events compared to standard care (OR 1.33; 95% CI 1.10-1.61). Compared to telavancin, there were fewer overall adverse events with dalbavancin (OR 0.58; 95% CI 0.45-0.76) and oritavancin (OR 0.71; 95% CI 0.55-0.92). Studies were of high quality overall. Our cost analyses demonstrated that dalbavancin and oritavancin were less costly compared to standard care under baseline assumptions and many scenarios evaluated. The use of dalbavancin could save third-party payers $1442 to $4803 per cSSTI, while the use of oritavancin could save $3571 to $6932 per cSSTI.

CONCLUSIONS

Dalbavancin and oritavancin demonstrate efficacy and safety comparable to standard care in well-designed RCTs and result in cost savings when standard care is treatment that covers MRSA.

Single-Dose Dalbavancin: A Review in Acute Bacterial Skin and Skin Structure Infections

Intravenous dalbavancin (Dalvance^®, Xydalba^®), first approved as a two-dose regimen for the treatment of acute bacterial skin and skin structure infections (ABSSSI), has now been additionally approved as a single-dose regimen. This narrative review discusses the pharmacological properties of intravenous dalbavancin and its clinical efficacy and tolerability as a single-dose regimen in the treatment of adult patients with ABSSSI. Single-dose dalbavancin is an effective and generally well tolerated treatment option for adults with ABSSSI, with noninferior efficacy to the two-dose dalbavancin regimen with regard to early clinical response (at 48-72 h) and low rates of adverse events. Clinical success rates at days 14 and 28 also did not significantly differ between the single- and two-dose dalbavancin regimens; neither did clinical success rates at day 14 when analysed by baseline pathogen. It has a broad spectrum of activity against common ABSSSI-related pathogens, and a favourable pharmacokinetic profile allowing for the convenience of single-dose administration. Thus, dalbavancin presents a promising alternative to conventional antibacterials for the treatment of ABSSSI in adult patients.

Telavancin: a novel semisynthetic lipoglycopeptide agent to counter the challenge of resistant Gram-positive pathogens

Telavancin (TD-6424), a semisynthetic lipoglycopeptide vancomycin-derivative, is a novel antimicrobial agent developed by Theravance for overcoming resistant Gram-positive bacterial infections, specifically methicillin-resistant Staphylococcus aureus (MRSA). The US Food and Drug Administration (USFDA) had approved telavancin in 2009 for the treatment of complicated skin and skin structure infections (cSSSIs) caused by Gram-positive bacteria, including MRSA (S. aureus, Streptococcus agalactiae, Streptococcus pyogenes, Streptococcus anginosus group, or Enterococcus faecalis). Telavancin has two proposed mechanisms of action. In vitro, telavancin has a rapid, concentration-dependent bactericidal effect, due to disruption of cell membrane integrity. Telavancin has demonstrable in vitro activity against aerobic and anaerobic Gram-positive bacteria. Telavancin and vancomycin have similar spectra of activity. Gram-negative bacteria are usually non-susceptible to telavancin. Telavancin has been successfully tested in various animal models of bacteremia, endocarditis, meningitis, and pneumonia. Phase II Telavancin versus Standard Therapy for Treatment of Complicated Skin and Soft-Tissue Infections due to Gram-Positive Bacteria (FAST 1 and FAST 2) and phase III [Assessment of Telavancin in Complicated Skin and Skin Structure Infections 1 (ATLAS 1 and ATLAS 2)] clinical trials have been conducted for evaluating telavancin's efficacy and safety in cSSSIs. Phase III clinical trials have been carried out for evaluating telavancin's safety and efficacy in nosocomial pneumonia [Assessment of Telavancin for Treatment of Hospital acquired Pneumonia 1 and 2 (ATTAIN 1 and ATTAIN 2)]. A phase II randomized, double-blind, clinical trial has been carried out for evaluating telavancin's safety and efficacy in uncomplicated S. aureus bacteremia [Telavancin for Treatment of Uncomplicated S. aureus Bacteremia (ASSURE)]. Pacemaker lead-related infective endocarditis due to a vancomycin intermediate S. aureus (VISA) strain (non-daptomycin susceptible) was successfully treated with parenteral telavancin for 8 weeks. Telavancin extensively binds to serum albumin (~93%) and has a relatively small volume of distribution. Telavancin is not biotransformed by any cytochrome P450 microsomal enzymes and excreted mainly in the urine. Though well-tolerated, worrisome adverse effects, including renal dysfunction and QTc prolongation are of potential concern. Given its extensive binding to plasma proteins, long half-life, and a long post-antibiotic effect, it represents a promising addition to the therapeutic armamentarium in combating infections caused by resistant Gram-positive pathogens, namely, MRSA.

Dalbavancin: A New Option for the Treatment of Gram-Positive Infections

Objective:

To review the pharmacology, microbiology, chemistry, in vitro susceptibility, pharmacokinetics, clinical efficacy, safety, tolerability, dosage, and administration of dalbavancin, a new semisynthetic lipoglycopeptide.

Data Sources:

A MEDLINE search, restricted to the English language, was conducted from 1966 through January 2006. Supplementary sources included program abstracts from the Interscience Conference on Antimicrobial Agents and Chemotherapy, American Society of Microbiology, and the Infectious Diseases Society of America from 2000 to 2005 and information available from the manufacturer's Web site.

Study Selection and Data Extraction:

In vitro and preclinical studies, as well as Phase I, II, and III clinical trials, were evaluated to summarize the microbiology, pharmacology, clinical efficacy, and safety of dalbavancin. All published trials and abstracts citing dalbavancin were selected.

Data Synthesis:

Dalbavancin, a novel lipoglycopeptide, has a mechanism of action similar to that of other glycopeptides. It has in vitro activity against a variety of gram-positive organisms, but no activity against gram-negative or vancomycin-resistant enterococci that possess VanA gene. Due to its prolonged half-life (6–10 days), dalbavancin can be administered intravenously once weekly. In Phase II and III clinical trials, dalbavancin was effective and well tolerated for the treatment of skin and soft-tissue infections, catheter-related bloodstream infections, and skin and skin-structure infections. To date, adverse events are mild and limited; the most common include pyrexia, headache, nausea, oral candidiasis, diarrhea, and constipation.

Conclusions:

Dalbavancin appears to be a promising antimicrobial agent for the treatment of gram-positive infections. A new drug application was filed with the Food and Drug Administration (FDA) in December 2004. The FDA issued an approvable letter in 2005 for dalbavancin. If approved, dalbavancin is expected to be launched in the first quarter of 2006.

Dalbavancin and Oritavancin: An Innovative Approach to the Treatment of Gram-Positive Infections

Health care-associated infections, especially those caused by multidrug-resistant gram-positive organisms, such as methicillin-resistant Staphylococcus aureus (MRSA), are a growing public health threat. In 2014, the U.S. Food and Drug Administration approved two new lipoglycopeptides, oritavancin and dalbavancin, for the treatment of acute bacterial skin and skin structure infections. The rationale for the development of these antimicrobials was partly to aid in the battle against vancomycin resistance in both Staphylococcus and Enterococcus. Considered a subclass of the glycopeptide antibiotics, the new lipoglycopeptides have similar mechanisms of action of binding to the carboxyl terminal d-alanyl-d-alanine residue of the growing peptide chains but differ from their parent glycopeptides by the addition of lipophilic tails. This addition allows for these agents to have prolonged half-lives, giving them unique dosing profiles. In addition, by concentrating at the site of action, they have increased potency against MRSA compared with vancomycin, the current mainstay of therapy. In this review, we focus on comparing and contrasting these two new agents with regard to their pharmacology, mechanisms of action, spectrum of activity, safety profiles, dosage and administration, and drug and laboratory interactions, and we review the clinical trials evaluating their use.

Transitions of care in the management of acute bacterial skin and skin structure infections: a paradigm shift

Acute bacterial skin and skin structure infections (ABSSSI) have evolved over a relatively short period of time to become one of the most challenging medical problems encountered in clinical practice. Notably the high incidence of methicillin-resistant S. aureus (MRSA) across the continuum of care has coincided with increased outpatient failures and higher rates of hospital admissions for parental antibiotic therapy. Consequently the management of ABSSSI constitutes a tremendous burden to the healthcare system in terms of cost of care and consumption of institutional and clinical resources. This perspective piece discusses current and new approaches to the management of ABSSSI in a hospital setting and the need for a multifaceted approach. Treatment strategies for the management through the utilization of observation units (OU), Outpatient Parental Antibiotic Therapy (OPAT), and newly developed antibiotics for the use against skin infections caused by Gram-positive bacteria will be discussed in the context of ABSSSI.

Dalbavancin for the treatment of acute bacterial skin and skin structure infections

INTRODUCTION

Acute bacterial skin and skin structure infections (ABSSSI) have increased in incidence and severity. The involvement of resistant organisms, particularly methicillin-resistant Staphylococcus aureus, presents additional challenges. The lipoglycopeptide dalbavancin has a prolonged half-life, high protein binding, and excellent tissue levels which led to its development as a once-weekly treatment for ABSSSI. In the pivotal DISCOVER 1 and DISCOVER 2 trials, dalbavancin proved non-inferior to vancomycin followed by linezolid when used sequentially for ABSSSI, forming the basis for its recent approval in the US and Europe for ABSSSI.

AREAS COVERED

A literature search of published pharmacologic and clinical data was conducted to review the chemistry, pharmacodynamics, and pharmacokinetics of dalbavancin. We also discuss its development process, highlighting efficacy and safety data from pertinent clinical trials and the role it could play in the current clinical landscape.

EXPERT OPINION

DISCOVER 1 and DISCOVER 2 demonstrated dalbavancin's non-inferiority to vancomycin followed by linezolid for ABSSSI and confirmed its safety and tolerability. They were among the first trials to use new, early primary efficacy endpoints, and dalbavancin was among the first agents designated a Qualified Infectious Disease Product for expedited review. Dalbavancin may prove to be a valuable option for ABSSSI patients in whom conventional therapy is limited.

Treatment of methicillin-sensitive Staphylococcus aureus bacteremia secondary to septic phlebitis using dalbavancin

WHAT IS KNOWN AND OBJECTIVE

Treatment of bacteremia due to Staphylococcus aureus often requires prolonged therapy leading to increased hospital lengths of stay and associated costs. For certain patients, referral to an outpatient parenteral antimicrobial therapy (OPAT) programme serves as an alternative to increased inpatient length of stay. We report an alternative to OPAT using dalbavancin for the treatment of methicillin-sensitive Staphylococcus aureus (MSSA).

CASE SUMMARY

A 54-year-old Caucasian man was brought to the emergency department from a rehabilitation centre with altered mental status and possible seizure. A peripheral intravenous catheter was placed in the left forearm, and the patient was transferred to the intensive care unit (ICU) for management of his acute psychosis, possible seizure and hyponatremia. Seven days into admission, the patient became febrile thought to be secondary to septic phlebitis of the forearm. Blood cultures were taken and organism identification using Nanosphere Verigene^® BC-GP rapid diagnostic testing resulted in MSSA. The patient received treatment with cefazolin with a planned treatment duration of 14 days but because of the patient's history of alcohol abuse, psychosis requiring hospitalization via the Baker Act, and history of non-compliance to follow-up appointments, the patient was deemed ineligible for OPAT. Due to the limited treatment options, therapy for MSSA bacteremia was changed on day 6 of cefazolin therapy to dalbavancin to complete the 14-day treatment duration. Blood cultures were negative at the end of treatment and no relapse of infection occurred.

WHAT IS NEW AND CONCLUSION

To our knowledge, this is the first case report using dalbavancin in clinical practice for the treatment of MSSA bacteremia secondary to septic phlebitis. This report highlights the potential role of the newer lipoglycopeptides, such as dalbavancin, in treating patients who require long-term parenteral antimicrobial therapy and are ineligible for treatment via OPAT.

Antibiotics and bacterial resistance in the 21st century

Dangerous, antibiotic resistant bacteria have been observed with increasing frequency over the past several decades. In this review the factors that have been linked to this phenomenon are addressed. Profiles of bacterial species that are deemed to be particularly concerning at the present time are illustrated. Factors including economic impact, intrinsic and acquired drug resistance, morbidity and mortality rates, and means of infection are taken into account. Synchronously with the waxing of bacterial resistance there has been waning antibiotic development. The approaches that scientists are employing in the pursuit of new antibacterial agents are briefly described. The standings of established antibiotic classes as well as potentially emerging classes are assessed with an emphasis on molecules that have been clinically approved or are in advanced stages of development. Historical perspectives, mechanisms of action and resistance, spectrum of activity, and preeminent members of each class are discussed.

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.

Dalbavancin, a long-acting lipoglycopeptide for the treatment of multidrug-resistant Gram-positive bacteria

Dalbavancin is a new lipoglycopeptide antibiotic in late-stage clinical development as a once-weekly treatment for serious infections including skin and skin structure infections. Its in vitro potency is greater than that of vancomycin, with a MIC(90) of 0.06 mg/l for Staphylococcus aureus and coagulase-negative staphylococci (irrespective of oxacillin susceptibility), 0.06-0.12 mg/l for vancomycin-susceptible Enterococcus spp. and 0.003 mg/l or less for Streptococcus pneumoniae or beta-hemolytic streptococci. Dalbavancin has dual routes of elimination. The results of Phase II/III studies show clinical efficiency in complicated skin and skin structure infection. During clinical trials, dalbavancin was as effective as linezolid or vancomycin in the treatment of patients with complicated skin and skin structure infection, including those with methicillin-resistant S. aureus. An additional Phase II study demonstrated efficacy in catheter-related bacteremia. Other preliminary in vitro and in vivo data have identified putative interest of dalbavancin in endocarditis, osteitis, diabetic foot, respiratory tract or joint infection.

Treatment options for multidrug-resistant bacteria

As a consequence of antibiotic overuse and misuse, nosocomial infections caused by multidrug-resistant bacteria represent a physician's nightmare throughout the world. No newer antimicrobials active against Pseudomonas aeruginosa, the main multidrug-resistant nosocomial pathogen, are available or under investigation. The only exceptions are linezolid, some newer glycopeptides (dalbavancin, oritavancin and telavancin) and daptomycin (a lipopeptide), which are active against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) strains, as well as tigecycline, a potent in vitro glycylcycline against MRSA, VRE, Acinetobacter baumannii and entended-spectrum beta-lactamase (ESBL)+ Enterobacteriaceae. Colistin, an antibiotic of the 1950s has been rediscovered by intensive care unit physicians for use against ESBL+ Enterobacteriaceae, as well as against multidrug-resistant P. aeruginosa and A. baumannii isolates. Although success rates with colistin range between 50 and 73%, almost all studies are retrospective. Immunostimulation efforts against S. aureus are still under development. As antibiotic research and development stagnate, rational policies for prescribing existing antibiotics plus strict infection control are the current mainstay efforts for preventing and combating multidrug-resistant bacterial infections.

Role of linezolid in the treatment of complicated skin and soft tissue infections

Staphylococcus aureus is the most common cause of complicated skin and soft tissue infections (cSSTIs). Antibiotic choices for these infections continue to evolve. History has seen penicillin progress to antistaphylococcal penicillins and cephalosporins, but these drugs are now giving way to drugs that are effective against methicillin-resistant S. aureus (MRSA). While vancomycin has been the gold standard to treat MRSA infections, newer therapeutic options have been developed over the last 5 years. These include quinupristin-dalfopristin, daptomycin, tigecycline and linezolid, which is the focus for this review. Linezolid is efficacious in the treatment of cSSTIs (including diabetic foot infections) caused by Gram-positive organisms (including MRSA), with a well-defined safety profile and straightforward dosing. It is also approved for nosocomial pneumonia, community-acquired pneumonia and uncomplicated skin and skin structure infections. Linezolid has an oral and parenteral formulation, which are equivalent. The oral formulation has the potential to offer economic benefits as compared with other therapies. Currently, there are only a few new antibiotics in development with MRSA activity. The proper use of all antibiotics, including these newer agents, is increasingly important if we are to slow the evolution of microbial resistance.

Antimicrobial Spectrum and Potency of Dalbavancin Tested Against Clinical Isolates from Europe and North America (2003): Initial Results from an International Surveillance Protocol

Dalbavancin is a bactericidal dimethylaminopropyl amide glycopeptide derivative possessing an extended serum elimination half-life in humans that allows once-weekly dosing for the therapy of Gram-positive infections. Strains from this baseline surveillance protocol in North America (NA; USA and Canada) and Europe (EU, 14 countries) were sampled in 2003. A total of 7,765 Gram-positive isolates (3,695 from NA and 4,070 from EU) were tested by reference broth microdilution methods against dalbavancin and 10 comparator agents. Species were analyzed separately by resistance phenotypes such as methicillin- (oxacillin-) resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE) and penicillin-resistant Streptococcus pneumoniae. Dalbavancin and other glycopeptides were very active against staphylococci (n=4648) with dalbavancin being 16- to 32-fold more potent than vancomycin (MIC90, 0.06 versus 2 mg/L). MRSA rates were greater (31.6%) in NA than in EU (26.1%). Quinupristin/dalfopristin resistance (MIC, > or = 2 mg/L; 0.1-0.5%) was documented more often in EU compared to NA. Dalbavancin (MIC50, 0.03-0.06 mg/L) was active against enterococci, except VanA resistance phenotypes. VRE rates were lower in EU (8.3%) then in NA (35.9%) from this resistance-enhanced enterococcal collection. Streptococci (dalbavancin MIC90, 0.016-0.03 mg/L) were generally most susceptible to glycopeptides (100.0%), quinupristin/dalfopristin (98.6-100.0%) and linezolid (100.0%); but dalbavancin was 16-fold more active than comparators. All vancomycin-susceptible enterococci and > 90% of vanB VRE had dalbavancin MIC values at < or = 1 mg/L,but vanA VRE strains had dalbavancin MIC results ranging from 0.06 to > 8 mg/L (median MIC, > or = 8 mg/L). Dalbavancin MIC values were not adversely influenced by geographic region or resistance phenotype (except vanA VRE). Infrequently isolated Gram-positive organisms such as Bacillus spp. (MIC90, 0.12 mg/L), Corynebacterium spp. (MIC90, 0.12 mg/L), Listeria monocytogenes (MIC90, 0.25 mg/L) and Micrococcus spp. (MIC90, 0.03 mg/L) were very susceptible to dalbavancin. In conclusion, these 2003 baseline resistance surveillance findings confirm the potent dalbavancin activity compared to several comparator agents against important Gram-positive pathogens. This high volume international survey indicates potential therapeutic roles for dalbavancin against many troublesome resistant Gram-positive phenotypes.

Dalbavancin in the treatment of complicated skin and soft-tissue infections: a review

Increasing rates of antimicrobial resistance among strains of Streptococcus, Staphylococcus, and Enterococcus spp. have been widely documented. At least 50% of nosocomial Staphylococcus aureus infections in intensive care units in the US and UK are due methicillin-resistant S. aureus (MRSA). Drug resistance is not confined to hospitals, and community-acquired MRSA (CA-MRSA) strains are now common causes of complicated skin and soft-tissue infections (cSSTIs) in many regions. Dalbavancin is a novel parenterally administered semisynthetic lipoglycopeptide similar to the naturally produced glycopeptides vancomycin and teicoplanin. Dalbavancin features a multifaceted mechanism of action that inhibits bacterial cell wall formation by two different mechanisms that enhances its activity against a wide range of gram-positive bacteria including staphylococci, streptococci, enterococci, and some anaerobes. Additionally, dalbavancin possesses unique pharmacokinetic properties, the most significant of which is a long terminal half-life that allows for once weekly dosing. This attribute may prove to yield clinical and cost benefit. Overall, clinical trials indicate that dalbavancin is a safe, well-tolerated, and effective antimicrobial agent. In the largest investigation evaluating dalbavancin for the treatment of cSSTIs, it appeared to be as effective as linezolid. Dalbavancin, which is expected to receive FDA approval in 2008, appears to be a promising new antimicrobial agent for the treatment of cSSTIs.

Newer antibacterial drugs for a new century

IMPORTANCE OF THE FIELD

Antibacterial drug discovery and development has slowed considerably in recent years, with novel classes discovered decades ago and regulatory approvals tougher to get. Traditional approaches and the newer genomic mining approaches have not yielded novel classes of antibacterial compounds. Instead, improved analogues of existing classes of antibacterial drugs have been developed by improving potency, minimizing resistance and alleviating toxicity.

AREAS COVERED IN THIS REVIEW

This article is a comprehensive review of newer classes of antibacterial drugs introduced or approved after year 2000.

WHAT THE READER WILL GAIN

It describes their mechanisms of action/resistance, improved analogues, spectrum of activity and clinical trials. It also discusses new compounds in development with novel mechanisms of action, as well as novel unexploited bacterial targets and strategies that may pave the way for combating drug resistance and emerging pathogens in the twenty-first century.

TAKE HOME MESSAGE

The outlook of antibacterial drug discovery, though challenging, may not be insurmountable in the years ahead, with legislation on incentives and funding introduced for developing an antimicrobial discovery program and efforts to conserve antibacterial drug use.

Surmounting antimicrobial resistance in the Millennium Superbug: Staphylococcus aureus

Staphylococcus aureus is the third most dreaded pathogen posing a severe threat due to its refractory behavior against the current armamentarium of antimicrobial drugs. This is attributed to the evolution of an array of resistance mechanisms responsible for morbidity and mortality globally. Local and international travel has resulted in the movement of drug resistant S. aureus clones from hospitals into communities and further into different geographical areas where they have been responsible for epidemic outbreaks. Thus, there is a dire necessity to refrain further cross movement of these multidrug resistant clones across the globe. The plausible alternative to prevent this situation is by thorough implementation of regulatory aspects of sanitation, formulary usage and development of new therapeutic interventions. Various strategies like exploring novel antibacterial targets, high throughput screening of microbes, combinatorial and synthetic chemistry, combinatorial biosynthesis and vaccine development are being extensively sought to overcome multidrug resistant chronic Staphylococcal infections. The majority of the antibacterial drugs are of microbial origin and are prone to being resisted. Anti-staphylococcal plant natural products that may provide a new alternative to overcome the refractory S.aureus under clinical settings have grossly been unnoticed. The present communication highlights the new chemical entities and therapeutic modalities that are entering the pharmaceutical market or are in the late stages of clinical evaluation to overcome multidrug resistant Staphylococcal infections. The review also explores the possibility of immunity and enzyme-based interventions as new therapeutic modalities and highlights the regulatory concerns on the prescription, usage and formulary development in the developed and developing world to keep the new chemical entities and therapeutic modalities viable to overcome antimicrobial resistance in S. aureus.

Activity of dalbavancin against Bacillus anthracis in vitro and in a mouse inhalation anthrax model

Bacillus anthracis, the causative agent of anthrax, can produce fatal disease when it is inhaled or ingested by humans. Dalbavancin, a novel, semisynthetic lipoglycopeptide, has potent activity, greater than that of vancomycin, against Gram-positive bacteria and a half-life in humans that supports once-weekly dosing. Dalbavancin demonstrated potent in vitro activity against B. anthracis (MIC range, < or =0.03 to 0.5 mg/liter; MIC(50) and MIC(90), 0.06 and 0.25 mg/liter, respectively), which led us to test its efficacy in a murine inhalation anthrax model. The peak concentrations of dalbavancin in mouse plasma after the administration of single intraperitoneal doses of 5 and 20 mg/kg of body weight were 15 and 71 mg/kg, respectively. At 20 mg/kg, the dalbavancin activity was detectable for 6 days after administration (terminal half-life, 53 h), indicating that long intervals between doses were feasible. The mice were challenged with 50 to 100 times the median lethal dose of the Ames strain of B. anthracis, an inoculum that kills untreated animals within 4 days. The efficacy of dalbavancin was 80 to 100%, as determined by the rate of survival at 42 days, when treatment was initiated 24 h postchallenge with regimens of 15 to 120 mg/kg every 36 h (q36h) or 30 to 240 mg/kg every 72 h (q72h). A regimen of ciprofloxacin known to protect 100% of animals was tested in parallel. Delayed dalbavancin treatment (beginning 36 or 48 h postchallenge) with 60 mg/kg q36h or 120 mg/kg q72h still provided 70 to 100% survival. The low MICs and long duration of efficacy in vivo suggest that dalbavancin may have potential as an alternative treatment or for the prophylaxis of B. anthracis infections.

Community-associated meticillin-resistant Staphylococcus aureus infections: epidemiology, recognition and management

Meticillin-resistant Staphylococcus aureus (MRSA) is an important cause of infection, particularly in hospitalized patients and those with significant healthcare exposure. In recent years, epidemic community-associated MRSA (CA-MRSA) infections occurring in patients without healthcare risk factors have become more frequent. The most common manifestation of CA-MRSA infection is skin and soft tissue infection, although necrotizing pneumonia, sepsis and osteoarticular infections can occur. CA-MRSA strains have become endemic in many communities and are genetically distinct from previously identified MRSA strains. CA-MRSA may be more capable colonizers of humans and more virulent than other S. aureus strains. Specific mechanisms of pathogenicity have not been elucidated, but several factors have been proposed as responsible for the virulence of CA-MRSA, including the Panton-Valentine leukocidin, phenol-soluble modulins and type I arginine catabolic mobile element. The movement of CA-MRSA strains into the nosocomial setting limits the utility of using clinical risk factors alone to designate community- or healthcare-associated status. Identification of unique genetic characteristics and genotyping are valuable tools for MRSA epidemiological studies. Although the optimum pharmacological therapy for CA-MRSA infections has not been determined, many CA-MRSA strains remain broadly susceptible to several non-beta-lactam antibacterial agents. Empirical antibacterial therapy should include an MRSA-active agent, particularly in areas where CA-MRSA is endemic.

Vancomycin resistance: are there better glycopeptides coming?

The appearance and dissemination of vancomycin resistance among clinically important Gram-positive bacteria was an important watershed in antimicrobial resistance trends that drastically narrows therapeutic options, particularly among the enterococci. Clinical resistance despite apparent susceptibility has also become an increasingly recognized issue with vancomycin treatment of methicillin-resistant Staphylococcus aureus pneumonia and endocarditis, which may be, in part, due to vancomycin-heteroresistant strains. The newly developed glycopeptides telavancin, dalbavancin and oritavancin have superior in vitro activity, enhanced bactericidality and unique pharmacokinetic properties compared with vancomycin and teicoplanin. Current clinical trial data show noninferiority to vancomycin or standard-of-care antistaphylococcal therapy for complicated skin-skin structure infections, and acceptable safety profiles. Although promising, whether or not these new compounds are clinically efficacious for the true therapeutic deficits created by in vitro and clinical vancomycin resistance is yet to be determined.

Current and novel antibiotics against resistant Gram-positive bacteria

The challenge posed by resistance among Gram-positive bacteria, epitomized by methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE) and vancomycin-intermediate and -resistant S. aureus (VISA and VRSA) is being met by a new generation of antimicrobials. This review focuses on the new β-lactams with activity against MRSA (ceftobiprole and ceftaroline) and on the new glycopeptides (oritavancin, dalbavancin, and telavancin). It will also consider the role of vancomycin in an era of existing alternatives such as linezolid, daptomycin and tigecycline. Finally, compounds in early development are described, such as iclaprim, friulimicin, and retapamulin, among others.

Skin and soft-tissue infections caused by community-acquired methicillin-resistant Staphylococcus aureus

Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infection has become epidemic. Skin and soft-tissue infections (SSTIs) are the most frequent forms of the disease. Obtainment of culture specimens is important for documentation of the presence of MRSA and for susceptibility testing to guide therapy. Purulent lesions should be drained whenever possible. In areas where community-acquired MRSA isolates are prevalent, uncomplicated SSTI in healthy individuals may be treated empirically with clindamycin, trimethoprim-sulfamethoxazole, or long-acting tetracyclines, although specific data supporting the efficacy of these treatments are lacking. In healthy patients with small purulent lesions, drainage alone may be sufficient. In patients with complicated SSTI requiring hospitalization or intravenous therapy, vancomycin is the drug of choice because of the low cost, efficacy, and safety. Linezolid, daptomycin, and tigecycline are also effective, although published studies on the last 2 agents for the treatment of SSTI due to MRSA are more limited. Dalbavancin, telavancin, and ceftobiprole are investigational agents that may expand our therapeutic options for the treatment of SSTI caused by MRSA.

Dalbavancin

Dalbavancin is a semisynthetic glycopeptide antibacterial agent that is active against Gram-positive bacteria associated with complicated skin and skin structure infections (cSSSIs). It is administered as a two-dose regimen intravenously infused over 30 minutes once weekly. The efficacy of dalbavancin (1000 mg on day 1 and 500 mg on day 8) has been examined in two randomized controlled trials in adults with cSSSIs. In each study, the primary efficacy measure was clinical success at the test-of-cure or follow-up visit in clinically evaluable patients. In a randomized, controlled, double-blind, multinational, phase III trial, dalbavancin was noninferior to linezolid, with clinical success rates of 88.9% and 91.2%. In a randomized, open-label, multicentre, phase II trial, clinical success rates were 94% with dalbavancin and 76% with comparator antibacterials. Dalbavancin was generally well tolerated by adult patients with cSSSIs, with most adverse events being of mild or moderate severity.

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.

Telavancin: a novel lipoglycopeptide antimicrobial agent

PURPOSE

The pharmacology, activity, pharmacokinetics, pharmacodynamics, clinical efficacy, safety, dosage, and place in therapy of telavancin are reviewed.

SUMMARY

Telavancin is a lipoglycopeptide antimicrobial agent under development for use in the treatment of multidrug-resistant gram-positive infections. Telavancin, like vancomycin, inhibits cell-wall biosynthesis by binding to late-stage cell-wall precursors. However, unlike vancomycin, telavancin also depolarizes the bacterial cell membrane and disrupts its functional integrity. Telavancin has concentration-dependent bactericidal activity and is active against gram-positive aerobic and anaerobic organisms. It is highly protein bound (93%) and has a volume of distribution of 115 mL/kg and a half-life of approximately eight hours. Telavancin is eliminated renally, and a dosage reduction is required in renally impaired patients. Animal models suggest that telavancin may be effective in the treatment of soft-tissue infections, bacteremia, endocarditis, meningitis, and pneumonia caused by gram-positive pathogens. Telavancin was not inferior to standard treatment for complicated skin and soft-tissue infections in two Phase II clinical trials and two Phase III clinical trials. A new drug application has been submitted for this indication, and Phase III trials to evaluate use in hospital-acquired-pneumonia, including infections caused by methicillin-resistant Staphylococcus aureus (MRSA), are planned. Adverse effects include metallic taste, nausea, vomiting, headache, foamy urine, Q-Tc-interval prolongation, hypokalemia, and serum creatinine increases. In trials evaluating telavancin for skin and soft-tissue infections, the dosage was 10 mg/kg i.v. once daily.

CONCLUSION

Telavancin is a promising new agent for gram-positive infections and may offer an alternative to vancomycin for MRSA-associated infections.