The Delta-Specific Opioid Glycopeptide BBI-11008: CNS Penetration and Behavioral Analysis in a Preclinical Model of Levodopa-Induced Dyskinesia.

In previous work we evaluated an opioid glycopeptide with mixed µ/δ-opioid receptor agonism that was a congener of leu-enkephalin, MMP-2200. The glycopeptide analogue showed penetration of the blood-brain barrier (BBB) after systemic administration to rats, as well as profound central effects in models of Parkinson's disease (PD) and levodopa (L-DOPA)-induced dyskinesia (LID). In the present study, we tested the glycopeptide BBI-11008 with selective δ-opioid receptor agonism, an analogue of deltorphin, a peptide secreted from the skin of frogs (genus Phyllomedusa). We tested BBI-11008 for BBB-penetration after intraperitoneal (i.p.) injection and evaluated effects in LID rats. BBI-11008 (10 mg/kg) demonstrated good CNS-penetrance as shown by microdialysis and mass spectrometric analysis, with peak concentration levels of 150 pM in the striatum. While BBI-11008 at both 10 and 20 mg/kg produced no effect on levodopa-induced limb, axial and oral (LAO) abnormal involuntary movements (AIMs), it reduced the levodopa-induced locomotor AIMs by 50% after systemic injection. The N-methyl-D-aspartate receptor antagonist MK-801 reduced levodopa-induced LAO AIMs, but worsened PD symptoms in this model. Co-administration of MMP-2200 had been shown prior to block the MK-801-induced pro-Parkinsonian activity. Interestingly, BBI-11008 was not able to block the pro-Parkinsonian effect of MK-801 in the LID model, further indicating that a balance of mu- and delta-opioid agonism is required for this modulation. In summary, this study illustrates another example of meaningful BBB-penetration of a glycopeptide analogue of a peptide to achieve a central behavioral effect, providing additional evidence for the glycosylation technique as a method to harness therapeutic potential of peptides.

Elimination of glycopeptide antibiotics by cytokine hemoadsorption in patients with septic shock: A study of three cases.

Sepsis and septic shock are characterized by a release of cytokines into the circulation. These mediators contribute to the detrimental hemodynamic and metabolic effects in the early phase of septic shock. Recently, a new polystyrene-based hemoadsorption device was introduced into clinical practice (CytoSorb®). The adsorber binds a variety of molecules including cytokines and removes them from the circulation. Studies in septic patients have shown an improved clinical course following hemoadsorption but no increased survival. We hypothesize that not only cytokines but also antibiotics may be removed which potentially may negate any beneficial effect of the adsorber. To test this hypothesis, we performed polystyrene-based hemoadsorption in three patients in septic shock and analysed glycopeptide elimination by measuring serum levels pre- and post-adsorber. We administered both teicoplanin and vancomycin via a 60-min infusion and vancomycin via continuous infusion, additionally. When applied as 60 min infusion, vancomycin and teicoplanin were removed immediately by the adsorber. However, the adsorptive capacity of the device was saturable. Serum levels of vancomycin, but not teicoplanin, decreased to subtherapeutic levels. With continuous infusion of vancomycin, removal was less and serum levels remained in the therapeutic range. In conclusion, we show effective glycopeptide adsorption using a polystyrene-based hemoadsorber in septic patients. The dose of these antibiotics should be adjusted appropriately and early therapeutic drug monitoring is highly recommended.

Pharmacokinetic Study of Bioactive Glycopeptide from Strongylocentrotus droebachiensis After Intranasal Administration to Rats Using Biomarker Approach.

A glycopeptide fraction (GPF) from internal organs of green sea urchins (Strongylocentrotus droebachiensis Müller, Strongylocentrotidae) has been reported to be an effective bronchitis treatment. In this study, we evaluated the pharmacokinetic and tissue distribution of GPF, following single and repeated intranasal (i/n) administration over the course of seven days in rats. The method measuring lactate dehydrogenase as biomarker was used to analyse the plasma and tissue concentrations of GPF. GPF appears in the plasma 15 min after single i/n administration (100 µg/kg) and reaches its maximum at 45 min. The area under the curve (AUC)0-24 and Cmax were similar using both i/n and intravenous administration, while mean residence time (MRT) and T1/2 after i/n administration were significantly higher compared with intravenous (i/v) administration. The absolute bioavailability of GPF after i/n administration was 89%. The values of tissue availability (ft) provided evidence about the highest concentration of GPF in the nose mucosa (ft = 34.9), followed by spleen (ft = 4.1), adrenal glands (ft = 3.8), striated muscle (ft = 1.8), kidneys (ft = 0.5), and liver (ft = 0.3). After repeated dose administration, GPF exhibited significantly higher AUC0-24 and MRT, indicating its accumulation in the plasma.

Comparing Gly11/dAla11-Replacement vs. the in-Situ Neprilysin-Inhibition Approach on the Tumor-targeting Efficacy of the 111In-SB3/111In-SB4 Radiotracer Pair.

Background: The GRPR-antagonist 68Ga-SB3 visualized prostate cancer lesions in animal models and in patients. Switching radiometal from 68Ga to 111In impaired tumor targeting in mice, but coinjection of the neprilysin (NEP)-inhibitor phosphoramidon (PA) stabilized 111In-SB3 in circulation and remarkably increased tumor uptake. We herein report on the biological profile of 111In-SB4: 111In-[dAla11]SB3. Methods: The biological responses of 111In-SB3/SB4 were compared in PC-3 cells and animal models. Results: Gly11/dAla11-replacement deteriorated GRPR-affinity (SB4 IC50: 10.7 ± 0.9 nM vs. SB3 IC50: 4.6 ± 0.3 nM) and uptake in PC-3 cells (111In-SB4: 1.3 ± 0.4% vs. 111In-SB3 16.2 ± 0.8% at 1 h). 111In-SB4 was more stable than 111In-SB3, but PA-coinjection stabilized both radiotracers in peripheral mice blood. Unmodified 111In-SB3 showed higher uptake in PC-3 xenografts (8.8 ± 3.0%ID/g) vs. 111In-SB4 (3.1 ± 1.1%ID/g) at 4 h pi. PA-coinjection improved tumor uptake, with 111In-SB3 still showing superior tumor targeting (38.3 ± 7.9%ID/g vs. 7.4 ± 0.3%ID/g for 111In-SB4). Conclusions: Replacement of Gly11 by dAla11 improved in vivo stability, however, at the cost of GRPR-affinity and cell uptake, eventually translating into inferior tumor uptake of 111In-SB4 vs. unmodified 111In-SB3. On the other hand, in-situ NEP-inhibition turned out to be a more efficient and direct strategy to optimize the in vivo profile of 111In-SB3, and potentially other peptide radiotracers.

Characterization, bioactivity and pharmacokinetic study of a novel carbohydrate-peptide polymer: Glycol-split heparin-endostatin2 (GSHP-ES2).

Endostatin (ES) has attracted considerable attention for the treatment of anti-angiogenesis-related disorders. An 11-amino-acid peptide (ES2, IVRRADRAAVP) from the amino terminal of ES is of interest because it is the main active fragment of ES. However, both ES and ES2 have a poor stability and a short half-life, and other disadvantages need to be further resolved. Thus, we conjugated ES2 to glycol-split heparin derivatives (GSHPs) to yield the polymer-peptide conjugate, GSHP-ES2. This study showed that GSHP-ES2 exhibited increased stability, a wider pH activity range, better inhibition of endothelial cell proliferation, migration and tube formation in vitro, better anti-angiogenic activity and a longer half-life in vivo compared with ES2. These results also indicate that GSHP-ES2 has good potential for the treatment of angiogenesis-related diseases, either alone or in combination with other chemicals.

Combatting resistant enterococcal infections: a pharmacotherapy review.

INTRODUCTION: The role of enterococci in infectious diseases has evolved from a gut and urinary commensal to a major pathogen of concern. Few options exist for resistant enterococci, and appropriate use of the available agents is crucial. AREAS COVERED: Herein, the authors discuss antibiotics with clinically useful activity against Enterococcus faecalis and E. faecium. The article specifically discusses: antibiotics active against enterococci and their mechanism of resistance, pharmacokinetic and pharmacodynamic principles, in vitro combinations, and clinical studies which focus on urinary tract, intra-abdominal, central nervous system, and bloodstream infections due to enterococci. EXPERT OPINION: Aminopenicillins are preferred over all other agents when enterococci are susceptible and patients can tolerate them. Daptomycin and linezolid have demonstrated clinical efficacy against vancomycin-resistant enterococci (VRE). Synergistic combinations are often warranted in complex infections of high inoculum and biofilms while monotherapies are generally appropriate for uncomplicated infections. Although active against resistant enterococci, the pharmacokinetics, efficacy and safety of tigecycline and quinupristin/dalfopristin can problematical for severe infections. For cystitis, amoxicillin, nitrofurantoin, or fosfomycin are ideal. Recently, approved agents such as tedizolid and oritavancin have good in vitro activity against VRE but clinical studies against other resistant enterococci are lacking.

Clinical Pharmacokinetics and Pharmacodynamics of Telavancin Compared with the Other Glycopeptides.

Telavancin was discovered by modifying the chemical structure of vancomycin and belongs to the group of lipoglycopeptides. It employs its antimicrobial potential through two distinct mechanisms of action: inhibition of bacterial cell wall synthesis and induction of bacterial membrane depolarization and permeabilization. In this article we review the clinically relevant pharmacokinetic and pharmacodynamic data of telavancin. For comparison, the pharmacokinetic and pharmacodynamic data of the other glycopeptides are presented. Although, in contrast to the newer lipoglycopeptides, telavancin demonstrates a relatively short half-life and rapid total clearance, its apparent volume of distribution (Vd) is almost identical to that of dalbavancin. The accumulation of telavancin after repeated dosing is only marginal, whereas the pharmacokinetic values of the other glycopeptides show much greater differences after administration of multiple doses. Despite its high plasma-protein binding of 90% and relatively low Vd of approximately 11 L, telavancin shows near complete equilibration of the free fraction in plasma with soft tissue. The ratio of the area under the plasma concentration-time curve from time zero to 24 h (AUC24) of unbound plasma concentrations to the minimal inhibitory concentration (MIC) required to inhibit growth of 90% of organisms (MIC90) of Staphylococcus aureus and S. epidermidis of telavancin are sufficiently high to achieve pharmacokinetic/pharmacodynamic targets indicative for optimal bacterial killing. Considering both the AUC24/MIC ratios of telavancin and the near complete equilibration of the free fraction in plasma with soft tissue, telavancin is an appropriate antimicrobial agent to treat soft tissue infections caused by Gram-positive pathogens. Although the penetration of telavancin into epithelial lining fluid (ELF) requires further investigations, the AUC24/MIC ratio for S. aureus indicates that bactericidal activity in the ELF could be expected.

Evaluation of Oritavancin Dosing Strategies against Vancomycin-Resistant Enterococcus faecium Isolates with or without Reduced Susceptibility to Daptomycin in an In Vitro Pharmacokinetic/Pharmacodynamic Model.

The clinical development of nonsusceptibility to the lipopeptide antibiotic daptomycin remains a serious concern during therapy for infections caused by vancomycin-resistant Enterococcus faecium (VREfm). The long-acting lipoglycopeptide oritavancin exhibits potent in vitro activity against VREfm, although its safety and efficacy for treating clinical VREfm infections have not been established. In this study, novel dosing regimens of daptomycin and oritavancin were assessed against both VREfm and daptomycin-nonsusceptible VREfm isolates in an in vitro pharmacokinetic/pharmacodynamic model.

Comparative Pharmacodynamics of Single-Dose Oritavancin and Daily High-Dose Daptomycin Regimens against Vancomycin-Resistant Enterococcus faecium Isolates in an In Vitro Pharmacokinetic/Pharmacodynamic Model of Infection.

There are limited therapeutic options to treat infections caused by vancomycin-resistant Enterococcus faecium (VREfm). The lipoglycopeptide oritavancin exhibits in vitro activity against this pathogen, although its utility against infections caused by VREfm has not been clinically established. In this study, the pharmacodynamic activity of free-drug levels associated with 12 mg/kg/day of daptomycin and a single 1,200-mg dose of oritavancin were determined against three VanA VREfm isolates in an in vitro pharmacokinetic/pharmacodynamic model.

Dosing antibiotics in neonates: review of the pharmacokinetic data.

Antibiotics are often used in neonates despite the absence of relevant dosing information in drug labels. For neonatal dosing, clinicians must extrapolate data from studies for adults and older children, who have strikingly different physiologies. As a result, dosing extrapolation can lead to increased toxicity or efficacy failures in neonates. Driven by these differences and recent legislation mandating the study of drugs in children and neonates, an increasing number of pharmacokinetic studies of antibiotics are being performed in neonates. These studies have led to new dosing recommendations with particular consideration for neonate body size and maturation. Herein, we highlight the available pharmacokinetic data for commonly used systemic antibiotics in neonates.

Radiation absorbed dose estimates for 18F-BPA PET.

Background Boron neutron capture therapy (BNCT) is a molecular radiation therapy approach based on the 10B (n, α) 7Li nuclear reaction in cancer cells. In BNCT, delivery of 10B in the form of 4-borono-phenylalanine conjugated with fructose (BPA-fr) to the cancer cells is important. The PET tracer 4-borono-2-18F-fluoro-phenylalanine (FBPA) has been used to predict the accumulation of BPA-fr before BNCT. Purpose To determine the biodistribution and dosimetric parameters in 18F-BPA PET/CT studies. Material and Methods Human biokinetic data were obtained during clinical 18F-BPA PET studies between February and June 2015 at one institution. Nine consecutive patients were studied prospectively. The internal radiation dose was calculated on the basis of radioactivity data from blood, urine, and normal tissue of the heart, liver, spleen, kidney, and other parts of the body at each time point using OLINDA/EXM1.1 program. We compared our calculations with published 18F-FDG data. Results Adult patients (3 men, 3 women; age range, 28-68 years) had significantly smaller absorbed doses than pediatric patients (3 patients; age range, 5-12 years) ( P = 0.003). The mean effective dose was 57% lower in adult patients compared with pediatric patients. Mean effective doses for 18F-BPA were 25% lower than those for 18F-FDG presented in International Commission of Radiation Protection (ICRP) publication 106. Conclusion We found significant differences in organ absorbed doses for 18F-BPA against those for 18F-FDG presented in ICRP publication 106. Mean effective doses for 18F-BPA were smaller than those for 18F-FDG in the publication by 0.5-38% (mean difference, 25%).

Electrocardiographic Effects of a Supratherapeutic Dose of Oritavancin.

The purpose of this study was to measure oritavancin's electrocardiographic effects at a supratherapeutic dose of 1600 mg given intravenously (IV) over 3 hours. A cohort of 150 healthy volunteers were randomized to receive placebo, oritavancin, or oral moxifloxacin 400 mg in a parallel designed thorough QT study. A supratherapeutic mean maximum oritavancin concentration (Cmax ) of 232 µg/mL was achieved. There was no significant effect on baseline and placebo corrected (dd) QTcF, QRS, or heart rate; ddPR was slightly increased at most time points, with a maximum mean change of 7.7 milliseconds 1 hour after infusion. Linear PK-PD modeling predicted a 3.2-millisecond change in the PR interval for the Cmax (138 µg/mL) observed in pivotal phase 3 studies after 1200 mg of oritavancin. Moxifloxacin produced the expected increase in ddQTcF, validating assay sensitivity. At plasma concentrations above the clinical exposures of oritavancin, no clinically or statistically significant effect on QTcF, QRS, or heart rate was observed. The increase in PR is considered clinically insignificant, given the rapid decline in initial plasma concentration of oritavancin after infusion and the expected lower Cmax in patients. A therapeutic 1200-mg single dose of oritavancin is not anticipated to cause any clinically significant effect on cardiac electrophysiology.

Improving the In Vivo Profile of Minigastrin Radiotracers: A Comparative Study Involving the Neutral Endopeptidase Inhibitor Phosphoramidon.

Minigastrin radiotracers, such as [(111)In-DOTA]MG0 ([(111)In-DOTA-DGlu(1)]minigastrin), have been considered for diagnostic imaging and radionuclide therapy of CCK2R-positive human tumors, such as medullary thyroid carcinoma. However, the high kidney retention assigned to the pentaGlu(2-6) repeat in the peptide sequence has compromised their clinical applicability. On the other hand, truncated des(Glu)(2-6)-analogs, such as [(111)In-DOTA]MG11 ([(111)In-DOTA-DGlu(10),desGlu(2-6)]minigastrin), despite their low renal uptake, show poor bioavailability and tumor targeting. [(111)In]CP04 ([(111)In-DOTA-DGlu(1-6)]minigastrin) acquired by Glu(2-6)/DGlu(2-6) substitution showed promising tumor-to-kidney ratios in rodents. In the present study, we compare the biological profiles of [(111)In]CP04, [(111)In-DOTA]MG11, and [(111)In-DOTA]MG0 during in situ neutral endopeptidase (NEP) inhibition, recently shown to improve the bioavailability of several peptide radiotracers. After coinjection of the NEP inhibitor, phosphoramidon (PA), the stability of [(111)In]CP04 and [(111)In-DOTA]MG0 in peripheral mouse blood increased, with an exceptional >14-fold improvement monitored for [(111)In-DOTA]MG11. In line with these findings, PA treatment increased the uptake of [(111)In]CP04 (8.5 ± 0.4%ID/g to 16.0 ± 2.3%ID/g) and [(111)In-DOTA]MG0 (11.9 ± 2.2%ID/g to 17.2 ± 0.9%ID/g) in A431-CCK2R(+) tumors at 4 hours postinjection, whereas the respective increase for [(111)In-DOTA]MG11 was >6-fold (2.5 ± 0.9%ID/g to 15.1 ± 1.7%ID/g). Interestingly, kidney uptake remained lowest for [(111)In-DOTA]MG11, but unfavorably increased by PA treatment for [(111)In-DOTA]MG0. Thus, overall, the most favorable in vivo profile was displayed by [(111)In-DOTA]MG11 during NEP inhibition, highlighting the need to validate this promising concept in the clinic.

About the equivalence between different batches of a glycopeptide drug.

CONTEXT: Teicoplanin is a glycopeptide antibiotic consisting of a combination of different active components. Clinical equivalence between different batches of this drug is not guaranteed by the present pharmacopeial specification of chemical composition based on an HPLC chromatogram. OBJECTIVE: To test a modification of this specification and to evaluate independent compositions recently published in the literature. MATERIALS AND METHODS: The expectable area under the plasma curve of each batch has been estimated based on its chemical composition as described in a former paper. Batch-comparisons are based on ratios between the area of the test batch and the area of a reference. RESULTS AND DISCUSSION: The modification of this specification recently proposed by the European Medicines Agency (EMA) has been tested confirming its goodness. A new acceptance range of AUC variation, rounding -10% to +15%, has been obtained. It is narrower than the current interval of the pharmacopeial specification. Concerning the generic batches that have been studied, the majority of differences with the reference is lower than ±10%. Variations in the compositions of the reference product have been observed to influence the results and a control criteria are proposed. CONCLUSION: The variability of the pharmacokinetic performance of teicoplanin can be better controlled with this new proposal of composition specification given by EMA.

Oritavancin: a review in acute bacterial skin and skin structure infections.

Oritavancin (Orbactiv(®)) is a new generation lipoglycopeptide approved for use in adult patients with acute bacterial skin and skin structure infections (ABSSSI). It is administered as a single 1200 mg intravenous infusion over 3 h. In phase 3 trials in adult patients with ABSSSI, oritavancin was noninferior to vancomycin in terms of a composite outcome (cessation of spreading or reduction in the size of the baseline lesion, absence of fever and no rescue antibacterials required; primary endpoint) assessed at an US FDA-recommended early timepoint of 48-72 h after initiation of treatment. Oritavancin was also noninferior to vancomycin in terms of a ≥20 % reduction in the baseline lesion size at the early timepoint and clinical cure rate 7-14 days after the end of treatment. Oritavancin was generally well tolerated in the phase 3 trials, with most treatment-emergent adverse reactions being mild in severity. The most common adverse events occurring in oritavancin recipients were nausea, headache, vomiting, limb and subcutaneous abscesses, and diarrhoea. Oritavancin offers a number of potential advantages, including a convenient single dose treatment that may shorten or eliminate hospital stays, a reduction in healthcare resource utilization and cost, no need for dosage adjustment in patients with mild to moderate hepatic or renal impairment, no need for therapeutic drug monitoring, and elimination of compliance concerns. Therefore, oritavancin is a useful treatment option for adults with ABSSSI.

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.

In vivo efficacy and pharmacological properties of a novel glycopeptide (YV4465) against vancomycin-intermediate Staphylococcus aureus.

Infections caused by vancomycin-intermediate Staphylococcus aureus (VISA) are associated with high rates of vancomycin treatment failure. The lipophilic vancomycin-carbohydrate conjugate YV4465 is a new glycopeptide antibiotic that is active against a variety of clinically relevant multidrug-resistant Gram-positive pathogens in vitro. YV4465 was 50- and 1000-fold more effective than vancomycin against VISA and vancomycin-resistant enterococci, respectively. This study evaluated the in vivo efficacy against VISA as well as the pharmacokinetics and toxicology of YV4465. A neutropenic mouse thigh infection model was used for the determination of efficacy and pharmacodynamic properties against VISA. YV4465 produced a dose-dependent reduction in VISA titres in thigh muscle; bacterial titres were reduced by up to ca. 2log(10)CFU/g from the pre-treatment titre at a dosage of 8 mg/kg. Single-dose pharmacokinetic studies demonstrated an increase in drug exposure to the animal following linear kinetics with a prolonged half-life (t(1/2)) compared with vancomycin. The peak plasma concentration (C(max)) following an intravenous dose of 12 mg/kg was 703 µg/mL. Acute toxicology studies revealed that YV4465 did not cause any significant alterations in biochemical parameters related to major organs such as the liver and kidneys at its pharmacodynamic endpoint (>ED(2-log kill)). These studies demonstrate that YV4465 has the potential to be developed as a next-generation glycopeptide antibiotic for the treatment of infections caused by VISA.

In vivo antibacterial activity and pharmacological properties of the membrane-active glycopeptide antibiotic YV11455.

The membrane-active glycopeptide antibiotic YV11455 is a lipophilic cationic vancomycin analogue that demonstrates rapid and concentration-dependent killing of clinically relevant multidrug-resistant (MDR) Gram-positive bacteria in vitro. YV11455 was 2-fold and 54-270-fold more effective than vancomycin against clinical isolates of vancomycin-sensitive and vancomycin-resistant bacteria, respectively. In this study, the in vivo efficacy, pharmacodynamics, pharmacokinetics and acute toxicology of YV11455 were investigated. In vivo activity and pharmacodynamics were determined in the neutropenic mouse thigh infection model against meticillin-resistant Staphylococcus aureus (MRSA). YV11455 produced dose-dependent reductions in MRSA titres in thigh muscle. When administered intravenously, the 50% effective dose (ED(50)) for YV11455 against MRSA was found to be 3.3 mg/kg body weight, and titres were reduced by up to ca. 3log(10)CFU/g from pre-treatment values at a dosage of 12 mg/kg with single treatment. Single-dose pharmacokinetic studies demonstrated linear kinetics and a prolonged half-life, with an increase in drug exposure (area under the concentration-time curve) compared with vancomycin. The peak plasma concentration following an intravenous dose of 12 mg/kg was 543.5 µg/mL. Acute toxicology studies revealed that YV11455 did not cause any significant alterations in biochemical parameters or histological pictures related to major organs such as the liver and kidney at its pharmacodynamic endpoint (ED(3-log kill)). These findings collectively suggest that YV11455 could be used clinically for the treatment of infections caused by MDR Gram-positive bacteria.

Population pharmacokinetic analysis for a single 1,200-milligram dose of oritavancin using data from two pivotal phase 3 clinical trials.

Oritavancin is a lipoglycopeptide antibiotic with activity against Gram-positive bacteria. Here we describe oritavancin population pharmacokinetics and the impact of patient-specific covariates on drug exposure variability. Concentration-time data were analyzed from two phase 3 clinical trials, SOLO I and SOLO II, in which oritavancin was administered as a single 1,200-mg dose to patients with acute bacterial skin and skin structure infections. A total of 1,337 drug concentrations from 297 patients (90% of whom had 4 or 5 pharmacokinetic samples) were available for analysis. A previously derived population model based on data from 12 phase 1, 2, and 3 oritavancin studies was applied to the SOLO data set. Alterations to the structural model were made, as necessary, based on model fit. Analyses utilized Monte Carlo parametric expectation maximization (S-ADAPT 1.5.6). The previous population pharmacokinetic model fit the data well (r(2) = 0.972), and population pharmacokinetic parameters were estimated with acceptable precision and lack of bias. Covariate evaluations revealed statistically significant relationships between central compartment volume and age and between clearance and height; however, these relationships did not indicate a clinically relevant impact on oritavancin exposure over the range of age and height observed in the SOLO studies. The mean (coefficient of variation [CV]) area under the plasma concentration-time curve from time zero to 72 h (AUC0-72) and maximum plasma concentration (Cmax) were 1,530 (36.9%) µg · h/ml and 138 (23%) µg/ml, respectively. The mean (CV) half-life at alpha phase (t1/2α), t1/2ß, and t1/2γ were 2.29 (49.8%), 13.4 (10.5%), and 245 (14.9%) hours, respectively. These analyses are the first to describe oritavancin pharmacokinetics following a single 1,200-mg dose. Covariate analyses suggested that no dose adjustments are required for renal impairment (creatinine clearance, >29 ml/min), mild or moderate hepatic impairment, age, weight, gender, or diabetes status.

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.