The study objective was to evaluate the pharmacokinetics (PK), antidrug antibody (ADA), and safety of motavizumab-YTE (motavizumab with amino acid substitutions M252Y/S254T/T256E [YTE]), an Fc-modified anti-respiratory syncytial virus (RSV) monoclonal antibody. Healthy adults (n ‫؍‬ 31) were randomized to receive a single intravenous (i.v.) dose of motavizumab-YTE or motavizumab (0.3, 3, 15, or 30 mg/kg) and followed for 240 days. Clearance of motavizumab-YTE was significantly lower (71% to 86%) and the half-life (t 1/2 ) was 2-to 4-fold longer than with motavizumab. However, similar peak concentrations and volume-of-distribution values, indicative of similar distribution properties, were seen at all dose levels. The sustained serum concentrations of motavizumab-YTE were fully functional, as shown by RSV neutralizing activity that persisted for 240 days with motavizumab-YTE versus 90 days postdose for motavizumab. Safety and incidence of ADA were comparable between groups. In this first study of an Fc-modified monoclonal antibody in humans, motavizumab-YTE was well tolerated and exhibited an extended half-life of up to 100 days. (This study has been registered at ClinicalTrials.gov under registration no. NCT00578682.) R espiratory syncytial virus (RSV) is a major cause of lower respiratory tract infections in infants and young children (1). No vaccine is currently approved for the prevention of RSV illness; however, palivizumab (MedImmune, Gaithersburg, MD) is available as prophylaxis against serious RSV disease in high-risk children. These high-risk children include infants born prematurely, children with chronic lung disease of prematurity (bronchopulmonary dysplasia), and children with congenital heart disease (2). RSV prophylaxis with palivizumab requires monthly intramuscular administration throughout the RSV season to maintain adequate serum concentrations. This monthly administration is necessary as immunoglobulin G (IgG) monoclonal antibodies (MAbs) are subject to proteolytic degradation and elimination, resulting in a serum half-life of approximately 20 days (3). An antibody with an extended half-life would reduce the required dosing frequency during the RSV season.A growing body of evidence identifies the major histocompatibility complex class I-related neonatal Fc receptor (FcRn) as a critical receptor in maintaining IgG homeostasis and extending the serum half-life of IgG and albumin in humans (4, 5). FcRn was originally identified in the transport of maternal antibodies across the placenta and the fetal small intestines in rats (6). In adult tissues, FcRn localized on vascular endothelium is a key component in the antibody salvage pathway whereby serum IgG undergoes endocytosis and is sequestered in lysosomes (7).A distinguishing characteristic of the IgG-FcRn pathway is obligate pH dependence. IgG-FcRn binding is driven by acidic pH (6.0) in the lysosome, whereas disassociation occurs at the neutral pH (7.4) of the extracellular environment (3). Acidification (pH 6.0 to 6.5) in the lysosomes enable...

Alpha-toxin (AT) is a major virulence factor in the disease pathogenesis of Staphylococcus aureus. We previously identified a monoclonal antibody (MAb) against AT that reduced disease severity in a mouse dermonecrosis model. Here, we evaluate the activity of an affinity-optimized variant, LC10, in a mouse model of S. aureus pneumonia. Passive immunization with LC10 increased survival and reduced bacterial numbers in the lungs and kidneys of infected mice and showed protection against diverse S. aureus clinical isolates. The lungs of S. aureus-infected mice exhibited bacterial pneumonia, including widespread inflammation, whereas the lungs of mice that received LC10 exhibited minimal inflammation and retained healthy architecture. Consistent with reduced immune cell infiltration, LC10-treated animals had significantly lower (P < 0.05) proinflammatory cytokine and chemokine levels in the bronchoalveolar lavage fluid than did those of the control animals. This reduction in inflammation and damage to the LC10-treated animals resulted in reduced vascular protein leakage and CO 2 levels in the blood. LC10 was also assessed for its therapeutic activity in combination with vancomycin or linezolid. Treatment with a combination of LC10 and vancomycin or linezolid resulted in a significant increase (P < 0.05) in survival relative to the monotherapies and was deemed additive to synergistic by isobologram analysis. Consistent with improved survival, the lungs of animals treated with antibiotic plus LC10 exhibited less inflammatory tissue damage than those that received monotherapy. These data provide insight into the mechanisms of protection provided by AT inhibition and support AT as a promising target for immunoprophylaxis or adjunctive therapy against S. aureus pneumonia.

bAlthough it has been on the market for over a decade, confusion remains regarding the pharmacokinetics (PK) and optimal dosing of palivizumab, a humanized IgG1 monoclonal antibody indicated for the prevention of serious lower respiratory tract disease caused by respiratory syncytial virus (RSV) in pediatric patients at high risk of RSV disease. The objectives of this analysis were to characterize the population PK of palivizumab in adults and children using nonlinear mixed-effect modeling, quantify the effects of individual covariates on variability in palivizumab disposition, and compare palivizumab exposures for various dosing scenarios. Palivizumab PK data from 22 clinical studies were used for model development. The model was developed using a two-stage approach: (i) a 2-compartment model with first-order absorption after intramuscular administration was fitted to adult data, and (ii) the same structural model was fitted to the sparse pediatric data using the NONMEM $PRIOR subroutine, with informative priors obtained from the adult analysis. Body weight and an age descriptor that combines gestational age and postnatal age (PAGE) using an asymptotic-exponential model best described palivizumab clearance in pediatric patients. Palivizumab clearance increased slightly from 10.2 ml/day to 11.9 ml/day as a function of PAGE ranging from 7 to 18 months. Covariate analysis indicated a 20% higher clearance in children with chronic lung disease and in children with antidrug antibody titer values of >80. These covariates did not substantially explain interindividual variability. In the label-indicated pediatric population, body weight was the primary demographic factor affecting palivizumab PK. Body weight-based dosing of 15 mg/kg yields similar palivizumab concentrations in children of different gestational and postnatal ages. Simulations demonstrated that there was little difference in palivizumab PK between healthy term and premature infants. Simulations also demonstrated that the 5 monthly palivizumab doses of 15 mg/kg, consistent with the label and studied in two randomized, clinical trials, provided greater and more prolonged palivizumab exposure than did an abbreviated dosing regimen of 3 monthly doses. R espiratory syncytial virus (RSV) is a respiratory pathogen of infants and young children that causes annual epidemics of bronchiolitis and pneumonia worldwide (6, 14). The peak incidence of severe RSV disease occurs between 2 and 3 months of age, and the main risk factors include prematurity, chronic lung disease (CLD; formerly known as bronchopulmonary dysplasia), and congenital heart disease (24,25,27). RSV is estimated to cause as much as 75% of all childhood bronchiolitis and up to 40% of all pediatric pneumonias (15). Lower respiratory tract disease due to RSV accounts for more than 125,000 pediatric hospitalizations and approximately 6.3 deaths per 100,000 person-years among children Ͻ4 years of age in the United States. Despite improvements in treatment, there is a 3% to 4% case fatality rate in infants...

ObjectiveTo evaluate the safety and tolerability of multiple intravenous (IV) doses of sifalimumab in adults with moderate-to-severe systemic lupus erythematosus (SLE).MethodsIn this multicenter, double-blind, placebo-controlled, sequential dose-escalation study, patients were randomized 3:1 to receive IV sifalimumab (0.3, 1.0, 3.0, or 10.0 mg/kg) or placebo every 2 weeks to week 26, then followed up for 24 weeks. Safety assessment included recording of treatment-emergent adverse events (AEs) and serious AEs. Pharmacokinetics, immunogenicity, and pharmacodynamics were evaluated, and disease activity was assessed.ResultsOf 161 patients, 121 received sifalimumab (26 received 0.3 mg/kg; 25, 1.0 mg/kg; 27, 3.0 mg/kg; and 43, 10 mg/kg) and 40 received placebo. Patients were predominantly female (95.7%). At baseline, patients had moderate-to-severe disease activity (mean SLE Disease Activity Index score 11.0), and most (75.2%) had a high type I interferon (IFN) gene signature. In the sifalimumab group versus the placebo group, the incidence of ≥1 treatment-emergent AE was 92.6% versus 95.0%, ≥1 serious AE was 22.3% versus 27.5%, and ≥1 infection was 67.8% versus 62.5%; discontinuations due to AEs occurred in 9.1% versus 7.5%, and death occurred in 3.3% (n = 4) versus 2.5% (n = 1). Serum sifalimumab concentrations increased in a linear and dose-proportional manner. Inhibition of the type I IFN gene signature was sustained during treatment in patients with a high baseline signature. No statistically significant differences in clinical activity (SLEDAI and British Isles Lupus Assessment Group score) between sifalimumab and placebo were observed. However, when adjusted for excess burst steroids, SLEDAI change from baseline showed a positive trend over time. A trend toward normal complement C3 or C4 level at week 26 was seen in the sifalimumab groups compared with baseline.ConclusionThe observed safety/tolerability and clinical activity profile of sifalimumab support its continued clinical development for SLE.

Sifalimumab had a safety profile that supports further clinical development. This trial demonstrated that overexpression of type I IFN signature in SLE is at least partly driven by IFNα, and exploratory analyses suggest that IFNα inhibition may be associated with clinical benefit in SLE. Trial registration number NCT00299819.

Hereditary transthyretin-mediated (hATTR) amyloidosis is a rare, inherited, progressively debilitating, and often fatal disease caused by deposition of mutated transthyretin (TTR) protein. Patisiran is an RNA interference therapeutic comprising a novel small interfering ribonucleic acid (ALN-18328) formulated with 2 novel lipid excipients, DLin-MC3-DMA and PEG 2000 -C-DMG, in a lipid nanoparticle targeted to inhibit hepatic TTR synthesis. Here we report the pharmacokinetics (PK) of ALN-18328, DLin-MC3-DMA, and PEG 2000 -C-DMG from a phase 2 multiple-ascending-dose study and its open-label extension (OLE) in patients with hATTR amyloidosis. Twenty-nine patients received 2 intravenous infusions of patisiran of 0.01, 0.05, 0.15, or 0.3 mg/kg at 3-or 4-week intervals; of these, 27 patients received 0.3 mg/kg once every 3 weeks over 24 months in the OLE study. Plasma PK profiles of ALN-18328 and DLin-MC3-DMA exhibited 2 phases, the first characterized by a short distribution half-life and the second by a minor peak and relatively long terminal elimination half-life. PK exposures to 3 analytes increased proportionally across the dose range of 0.01 to 0.3 mg/kg. For ALN-18328, mean terminal elimination half-life was 3.2 days, mean total clearance was 3.0 mL/h/kg, and urinary excretion was negligible. All 3 analytes exhibited stable PK profiles with chronic dosing over 2 years. The 2-to 3-fold plasma accumulation (AUC τ ) of ALN-18328 at steady state is attributable to the association of ALN-18328 with the cationic lipid DLin-MC3-DMA. There was no appreciable accumulation of PEG 2000 -C-DMG.

MEDI4893 is an investigational immunoglobulin G1(κ) monoclonal antibody that specifically binds to and neutralizes alpha-toxin, a key Staphylococcus aureus virulence factor. A triple-amino-acid substitution, M252Y/S254T/T256E, was engineered into the MEDI4893 Fc region to extend its serum half-life. A phase 1, double-blind, dose escalation study was designed to evaluate the safety, tolerability, pharmacokinetics, anti-alpha-toxin-neutralizing activity, and antidrug antibody (ADA) response of MEDI4893 following a single intravenous infusion in healthy adults 18 to 65 years of age. Thirty-three subjects were randomly assigned to receive MEDI4893 at 225 mg (n = 3), 750 mg (n = 3), 2,250 mg (n = 8), or 5,000 mg (n = 12) or placebo (n = 7) and were followed for 360 days. Adverse events were mild or moderate in severity; none were serious. The MEDI4893 peak serum concentration increased dose proportionally from 77.2 μg/ml (225-mg dose) to 1,784 μg/ml (5,000-mg dose). The area under the concentration-time curve from 0 to 360 days also increased dose proportionally, from 4,840 μg · day/ml (225-mg dose) to 91,493 μg · day/ml (5,000-mg dose), indicating linear pharmacokinetics. MEDI4893's terminal half-life was estimated to be 80 to 112 days, which is approximately 4-fold longer than the half-lives of other human immunoglobulin G antibodies. The alpha-toxin-neutralizing activity in serum correlated highly with the MEDI4893 concentrations in serum. Three adults transiently tested positive for ADA on day 151, but this did not have an impact on MEDI4893 serum concentrations or the MEDI4893 safety profile; no subjects exhibited serum ADA at the study end. These data support the continued development of MEDI4893 for the prevention of S. aureus-mediated pneumonia. (This study has been registered at ClinicalTrials.gov under identifier NCT02296320.)

Givosiran is a small interfering ribonucleic acid agent that was recently approved in the United States for the treatment of acute hepatic porphyria (AHP). This phase I study evaluated the safety, pharmacokinetic, and pharmacodynamic profile of subcutaneously (SC) administered givosiran in patients with acute intermittent porphyria, the most common AHP type. Givosiran was rapidly absorbed from the SC injection site with peak plasma concentrations achieved within 0.5–5 hours followed by elimination with a short half‐life of 4–10 hours. Plasma exposures of AS(N‐1)3′ givosiran, an active metabolite with equal potency as givosiran, was 35%–75%. Givosiran treatment resulted in a rapid and dose‐dependent reduction in urinary aminolevulinic acid (ALA) and porphobilinogen (PBG) towards the upper limit of normal (ULN) in AHP patients. Greater and more sustained reductions in ALA and PBG were achieved with once monthly dosing compared with once quarterly dosing. After monthly dosing, trough ALA levels were reduced to below the ULN, approximately 95% reduction from baseline, at both the 2.5 and 5.0 mg/kg doses.