Population Pharmacokinetics of Naloxegol in Pediatric Subjects Receiving Opioids.

The pharmacokinetics (PK) of naloxegol were characterized in pediatric subjects, aged 6 months or older to less than 18 years who either have or are at risk of developing opioid-induced constipation following single dose administration. Subjects grouped as aged 12 years or older to less than 18 years, 6 months or older to less than 12 years, and 6 months or older to less than 6 years, received a single oral dose of naloxegol at doses that were estimated to achieve plasma exposures comparable to adult 12.5- or 25-mg doses. Intensive and sparse plasma naloxegol samples were collected to assess naloxegol concentrations. Data were combined with previously collected adult PK data and used to estimate PK parameters using population PK analyses. Naloxegol PK was described using a 2-compartment model with Weibull-type absorption. Neither age nor body weight was identified as a significant covariate indicating similar PK properties in adult and pediatric subjects. PK estimates in the youngest age group were approximately 80% less than those in adults (12.5-mg equivalent dose). Exposures in the other pediatric groups were similar to those in adult equivalent doses. The PK of naloxegol were characterized as linear over the dose range, with no clinically significant covariates and comparable PK characteristics in adults and pediatric subjects aged 6 months or older.

Identifying novel phenotypes of vulnerability and resistance to activity-based anorexia in adolescent female rats.

OBJECTIVE: Activity-based anorexia is a translational rodent model that results in severe weight loss, hyperactivity, and voluntary self-starvation. The goal of our investigation was to identify vulnerable and resistant phenotypes of activity-based anorexia in adolescent female rats. METHOD: Sprague-Dawley rats were maintained under conditions of restricted access to food (N = 64; or unlimited access, N = 16) until experimental exit, predefined as a target weight loss of 30-35% or meeting predefined criteria for animal health. Nonlinear mixed effects statistical modeling was used to describe wheel running behavior, time to event analysis was used to assess experimental exit, and a regressive partitioning algorithm was used to classify phenotypes. RESULTS: Objective criteria were identified for distinguishing novel phenotypes of activity-based anorexia, including a vulnerable phenotype that conferred maximal hyperactivity, minimal food intake, and the shortest time to experimental exit, and a resistant phenotype that conferred minimal activity and the longest time to experimental exit. DISCUSSION: The identification of objective criteria for defining vulnerable and resistant phenotypes of activity-based anorexia in adolescent female rats provides an important framework for studying the neural mechanisms that promote vulnerability to or protection against the development of self-starvation and hyperactivity during adolescence. Ultimately, future studies using these novel phenotypes may provide important translational insights into the mechanisms that promote these maladaptive behaviors characteristic of anorexia nervosa.

Effect of fixed-dose subcutaneous reslizumab on asthma exacerbations in patients with severe uncontrolled asthma and corticosteroid sparing in patients with oral corticosteroid-dependent asthma: results from two phase 3, randomised, double-blind, placebo-controlled trials.

BACKGROUND: Reslizumab 3 mg/kg administered intravenously is approved for the treatment of severe eosinophilic asthma. We assessed the safety and efficacy of subcutaneous reslizumab 110 mg in two trials in patients with uncontrolled severe asthma and increased blood eosinophils. The aim was to establish whether subcutaneous reslizumab 110 mg can reduce exacerbation rates in these patients (study 1) or reduce maintenance oral corticosteroid dose in patients with corticosteroid-dependent asthma (study 2). METHODS: Both studies were randomised, double-blind, placebo-controlled, phase 3 studies. Entry criteria for study 1 were uncontrolled severe asthma, two or more asthma exacerbations in the previous year, a blood eosinophil count of 300 cells per µL or more (including no more than 30% patients with an eosinophil count <400 cells/µL), and at least a medium dose of inhaled corticosteroids with one or more additional asthma controllers. Patients in study 2 had severe asthma, a blood eosinophil count of 300 cells per µL or more, daily maintenance oral corticosteroid (prednisone 5-40 mg, or equivalent), and high-dose inhaled corticosteroids plus another controller. Patients were randomly assigned (1:1) to subcutaneous reslizumab (110 mg) or placebo once every 4 weeks for 52 weeks in study 1 and 24 weeks in study 2. Patients and investigators were masked to treatment assignment. Primary efficacy outcomes were frequency of exacerbations during 52 weeks in study 1 and categorised percentage reduction in daily oral corticosteroid dose from baseline to weeks 20-24 in study 2. Primary efficacy analyses were by intention to treat, and safety analyses included all patients who received at least one dose of study treatment. These studies are registered with ClinicalTrials.gov, NCT02452190 (study 1) and NCT02501629 (study 2). FINDINGS: Between Aug 12, 2015, and Jan 31, 2018, 468 patients in study 1 were randomly assigned to placebo (n=232) or subcutaneous reslizumab (n=236), and 177 in study 2 to placebo (n=89) or subcutaneous reslizumab (n=88). In study 1, we found no significant difference in the exacerbation rate between reslizumab and placebo in the intention-to-treat population (rate ratio 0·79, 95% CI 0·56-1·12; p=0·19). Subcutaneous reslizumab reduced exacerbation frequency compared with placebo in the subgroup of patients with blood eosinophil counts of 400 cells per µL or more (0·64, 95% CI 0·43-0·95). Greater reductions in annual exacerbation risk (p=0·0035) and longer time to first exacerbation were observed for patients with higher trough serum reslizumab concentrations. In study 2, we found no difference between placebo and fixed-dose subcutaneous reslizumab in categorised percentage reduction in daily oral corticosteroid dose (odds ratio for a lower category of oral corticosteroid use in the reslizumab group vs the placebo group, 1·23, 95% CI 0·70-2·16; p=0·47). The frequency of adverse events and serious adverse events with reslizumab were similar to those with placebo in both studies. INTERPRETATION: Fixed-dose (110 mg) subcutaneous reslizumab was not effective in reducing exacerbation frequency in patients with uncontrolled asthma and increased blood eosinophils (≥300 cells/µL), or in reducing the daily maintenance oral corticosteroid dose in patients with oral corticosteroid-dependent severe eosinophilic asthma. Higher exposures than those observed with 110 mg subcutaneous reslizumab are required to achieve maximal efficacy. FUNDING: Teva Branded Pharmaceutical Products R&D.

The novel neuropeptide Y Y5 receptor antagonist Lu AA33810 [N-[[trans-4-[(4,5-dihydro[1]benzothiepino[5,4-d]thiazol-2-yl)amino]cyclohexyl]methyl]-methanesulfonamide] exerts anxiolytic- and antidepressant-like effects in rat models of stress sensitivity.

Neuropeptide Y (NPY) regulates physiological processes via receptor subtypes (Y(1), Y(2), Y(4), Y(5), and y(6)). The Y(5) receptor is well known for its role in appetite. Based on expression in the limbic system, we hypothesized that the Y(5) receptor might also modulate stress sensitivity. We identified a novel Y(5) receptor-selective antagonist, Lu AA33810 [N-[[trans-4-[(4,5-dihydro[1]-benzothiepino[5,4-d]thiazol-2-yl)amino]cyclohexyl]methyl]-methanesulfonamide], that bound to cloned rat Y(5) receptors (K(i) = 1.5 nM) and antagonized NPY-evoked cAMP and calcium mobilization in vitro. Lu AA33810 (3-30 mg/kg p.o.) blocked feeding elicited by intracerebroventricular injection of the Y(5) receptor-selective agonist [cPP(1-7),NPY(19-23),Ala(31),Aib(32),Gln(34)]-hPancreatic Polypeptide in Sprague-Dawley rats. In vivo effects of Lu AA33810 were correlated with brain exposure > or = 50 ng/g and ex vivo Y(5) receptor occupancy of 22 to 95%. Lu AA33810 was subsequently evaluated in models of stress sensitivity. In Fischer 344 rats, Lu AA33810 (30 mg/kg p.o.) attenuated increases in plasma ACTH and corticosterone elicited by intracerebroventricular injection of [cPP(1-7),NPY(19-23),Ala(31),Aib(32),Gln(34)]-hPancreatic Polypeptide. In Sprague-Dawley rats subjected to the social interaction test, Lu AA33810 (3-30 mg/kg p.o.) produced anxiolytic-like effects after acute or chronic treatment. In Flinders sensitive line rats, chronic dosing of Lu AA33810 (10 mg/kg/day i.p.) produced anxiolytic-like effects in the social interaction test, plus antidepressant-like effects in the forced swim test. In Wistar rats exposed to chronic mild stress, chronic dosing of Lu AA33810 (3 and 10 mg/kg/day i.p.) produced antidepressant-like activity, i.e., normalization of stress-induced decrease in sucrose consumption. We propose that Y(5) receptors may function as part of an endogenous stress-sensing system to mediate social anxiety and reward or motivational deficits in selected rodent models.

Mild exercise in female subjects impairs complex learning independent of hydration status and emotion.

INTRODUCTION: Depending on type, intensity and duration, exercise can have both beneficial and detrimental effects on cognitive function. The impact of exercise on learning and memory is also sensitive to hydration status, so we hypothesized that mild hypohydration induced with exercise, will adversely impact executive and complex memory function tasks and that these changes in cognitive function are independent of changes in emotion. METHODS: Using a cross over design, on separate days 11 women exercised on a recumbent bicycle. On day 1, women exercised to 1.5% hypohydration at 34°C, and <10% rh, on day 2, water loss from sweating was replaced by drinking water (euhydration). Pre- and post-euhydration and hypohydration, subjects underwent computer based cognitive tasks (simple, learning, memory, executive function) and visual analog testing to determine emotion. RESULTS: Exercise increased Groton Maze Learning Test errors within both conditions: [Pre: 41.5±11.8, Post: 46.8±12.4, and Pre: 41.9±9.2, Post: 46.5±12.9, hypohydrated and euhydrated, respectively, Pre vs Post, ANOVA, time effect, P=0.007], a test of acquisition, storage, and use of new knowledge. None of the measures of emotion were affected by exercise under either hydration condition. CONCLUSIONS: A bout of mild aerobic exercise compromised performance on a complex learning and memory task, but this change was unaffected by hydration status or emotion.

Reproducibility of intraperitoneal 2-deoxy-2-[18F]-fluoro-D-glucose cerebral uptake in rodents through time.

INTRODUCTION: One strength of small animal imaging is the ability to obtain longitudinal measurements within the same animal, effectively reducing the number of animals needed and increasing statistical power. However, the variability of within-rodent brain glucose uptake after an intraperitoneal injection across an extended time has not been measured. METHODS: Small animal imaging with 2-deoxy-2-[(18)F]-fluoro-D-glucose ((18)FDG) was used to determine the variability of a 50-min brain (18)FDG uptake following an intraperitoneal injection over time in awake male and female Sprague-Dawley rodents. RESULTS: After determining the variability of an intraperitoneal injection in the awake rat, we found that normalization of brain (18)FDG uptake for (1) injected dose and body weight or (2) body weight, plasma glucose concentration and injected dose resulted in a coefficient of variation (CV) of 15%. However, if we normalized regional uptake to whole brain to compare relative regional changes, the CV was less than 5%. Normalized cerebral (18)FDG uptake values were reproducible for a 2-week period in young adult animals. After 1 year, both male and female animals had reduced whole-brain uptake, as well as reduced regional hippocampal and striatal (18)FDG uptake. CONCLUSION: Overall, our results were similar to findings in previous rodent and human clinical populations; thus, using a high throughput study with intraperitoneal (18)FDG is a promising preclinical model for clinical populations. This is particularly relevant for measuring changes in brain function after experimental manipulation, such as long-term pharmacological administration.

Acute handling stress modulates methylphenidate-induced catecholamine overflow in the medial prefrontal cortex.

Although stress is an extensively investigated phenomenon, the effects of specific stressors on the pharmacologic activity of routinely administered drugs are less well characterized. We designed the present study to investigate the effect of handling stress on catecholaminergic responsivity following an acute methylphenidate (MP, Ritalin) challenge in the medial prefrontal cortex (mPFC). Norepinephrine (NE) and dopamine (DA) levels were simultaneously measured in 15-min samples of PFC dialysate using HPLC coupled with electrochemical detection. Sprague-Dawley rats were handled for 15 min, which produced an increase from basal extracellular DA and NE levels. Handling stress attenuates the DA response when administered 2 h prior to IP MP, whereas handling stress enhances the DA response when administered simultaneously with IG MP. These findings suggest that persistent alterations in mesocorticolimbic DA-ergic activity are induced by a short exposure to restraint stress as evidenced by the altered response to MP challenge.

Decreased serotonin levels associated with behavioral disinhibition in tissue plasminogen activator deficient (tPA-/-) mice.

Tissue Plasminogen Activator (tPA) is a serine protease expressed in different areas of the mammalian brain. It has been used clinically to dissolve clots and shown to have a role in neurodegeneration. Early studies suggested that tPA plays an important role in the processes of learning and memory, demonstrated at the level of behavior and synaptic plasticity. Herein, we extend the behavioral characterization of these mice to the related dimension of exploratory-related behavior using an extensive battery of behavioral tests as well as the neurotransmitter metabolism associated with the behavioral measures. Our results indicate a behavior tendency in these mice consistent with "impulsivity" or reduced exploratory inhibition. These patterns are accompanied by decreased levels of serotonin in several brain regions important in behavioral regulation in the tPA(-/-) mice compared to control animals. Systemic administration of fluoxetine reversed the behavioral disinhibition of tPA(-/-) mice, further supporting an important alteration in behavior regulation mediated by serotonin systems as underappreciated but important element of the behavioral phenotype of these animals.

The MCH1 receptor antagonist SNAP 94847 induces sensitivity to dopamine D2/D3 receptor agonists in rats and mice.

Antidepressant treatment of two or more weeks in rats has been shown to enhance the locomotor-stimulating effects of dopamine D(2)/D(3) receptor agonists. This action has been attributed to an increased sensitivity of postsynaptic dopamine receptors in the nucleus accumbens, thought to represent an essential mechanism by which antidepressants act therapeutically to enhance reward and motivation. We tested whether the melanin-concentrating hormone receptor(1) (MCH(1)) antagonist SNAP 94847, reported to have antidepressant-like activity in several preclinical behavioral models, mimics this key feature of established antidepressants. Locomotor responses to the dopamine D(2)/D(3) agonist quinpirole following acute or chronic administration of fluoxetine (18 mg/kg/day) or SNAP 94847 (20 mg/kg/day) were assessed in habituated Sprague-Dawley rats, as well as BALB/c and CD-1 mice. Rats showed a significant increase in quinpirole-induced locomotor activity following chronic (2 weeks), but not acute (1 h) fluoxetine or SNAP 94847 administration. BALB/c mice treated for 21 days with fluoxetine or SNAP 94847 showed marked increases in quinpirole-induced locomotor activity, with the onset of hyper-locomotion appearing earlier in the time course after SNAP 94847 compared to fluoxetine. Administration of either compound for 7 days was also sufficient to augment the quinpirole response in BALB/c mice. Fluoxetine and SNAP 94847 (21 days) failed to modify quinpirole responses in CD-1 mice, and the compounds were ineffective after acute administration in both mouse strains. This report demonstrates in two rodent species that chronic treatment with an MCH(1) receptor antagonist, as with clinically proven antidepressants, produces sensitization to the locomotor effects of dopamine D(2)/D(3) agonists.

Brain metabolic changes following 4-week citalopram infusion: increased 18FDG uptake and gamma-amino butyric acid levels.

We used 2-week and 4-week citalopram infusion (10 mg/kg/day) to determine how this selective serotonin reuptake inhibitor (SSRI) would alter 2-deoxy-2-[18F]-fluoro-D-glucose (18FDG) uptake and neurotransmitter tissue levels in male Sprague-Dawley rodents. A weekly time course of 18FDG uptake altered by chronic citalopram treatment was determined in vivo with small animal positron emission tomography (microPET). Additionally, end of study monoamine levels were measured ex vivo using high pressure liquid chromatography (HPLC) and amino acid levels were determined ex vivo with proton nuclear magnetic resonance spectroscopy (1H-NMRS). We found increased striatal 18FDG uptake, reduced tissue levels of noradrenaline and serotonin in the striatum and prefrontal cortex, and increased striatal gamma-amino-butyric acid following 4-week citalopram infusion.

MicroPET imaging in an animal model of anorexia nervosa.

Anorexia nervosa is a life-threatening psychiatric disorder characterized by severe weight loss and high rates of comorbidity and mortality. The current study assessed the feasibility of using microPET imaging to study the effects of chronic food restriction in an animal model of anorexia nervosa. To establish preliminary support for this model, we hypothesized that chronic food restriction would decrease relative 2-deoxy-2-[18F]fluoro-D-glucose (18FDG) uptake in the rat, in effect modeling cerebral glucose hypometabolism reported in the clinical population of anorexia nervosa. Nine adolescent Wistar female rats received a baseline 18FDG scan. The control group received free access to food for a period of 25 days. The food restricted (FR) group received 40% of their baseline daily food intake until a 30% weight loss occurred; body weight was then maintained at 70% of baseline by adjusting daily food intake. The FR group also had free access to a running wheel for a mean period of 10.8+/-6.1 days. Both groups received a follow-up 18FDG scan. Relative 18FDG uptake was significantly increased in the cerebellum and significantly decreased in the hippocampus and striatum in the FR group compared to controls. Moreover, there was a trend towards a decrease in relative 18FDG uptake in the thalamus in the FR compared to control group. This is the first study to establish support for the use of microPET imaging in an animal model of anorexia nervosa as a means for studying the neurobiological changes that occur due to chronic food restriction.