Quantifying mutant huntingtin protein in human cerebrospinal fluid to support the development of huntingtin-lowering therapies.

Huntington's disease (HD) is caused by a cytosine adenine guanine-repeat expansion in the huntingtin gene. This results in the production of toxic mutant huntingtin protein (mHTT), which has an elongated polyglutamine (polyQ) stretch near the protein's N-terminal end. The pharmacological lowering of mHTT expression in the brain targets the underlying driver of HD and is one of the principal therapeutic strategies being pursued to slow or stop disease progression. This report describes the characterisation and validation of an assay designed to quantify mHTT in the cerebrospinal fluid of individuals with HD, for use in registrational clinical trials. The assay was optimised, and its performance was characterised with recombinant huntingtin protein (HTT) varying in overall and polyQ-repeat length. The assay was successfully validated by two independent laboratories in regulated bioanalytical environments and showed a steep signal increase as the polyQ stretch of recombinant HTTs pivoted from wild-type to mutant protein forms. Linear mixed effects modelling confirmed highly parallel concentration-response curves for HTTs, with only a minor impact of individual slopes of the concentration-response for different HTTs (typically < 5% of the overall slope). This implies an equivalent quantitative signal behaviour for HTTs with differing polyQ-repeat lengths. The reported method may be a reliable biomarker tool with relevance across the spectrum of HD mutations, which can facilitate the clinical development of HTT-lowering therapies in HD.

Randomized, Double-Blind, Placebo-Controlled Trial of the mGlu2/3 Negative Allosteric Modulator Decoglurant in Partially Refractory Major Depressive Disorder.

OBJECTIVE: To assess putative antidepressant and procognitive effects of decoglurant, a selective metabotropic glutamate receptor type 2/3 (mGlu2/3) negative allosteric modulator, as adjunctive treatment to selective serotonin reuptake inhibitors and/or serotonin-norepinephrine reuptake inhibitors (SSRIs/SNRIs) in patients with partially refractory major depressive disorder (MDD), diagnosed using DSM-IV-TR criteria. METHODS: This randomized, placebo-controlled, double-blind, multicenter phase 2 trial consisted of 4 weeks' screening, 6 weeks' treatment, and 8 weeks' follow-up between September 2011 and June 2014. Individuals with Montgomery-Åsberg Depression Rating Scale (MADRS) score ≥ 25 and Clinical Global Impressions-Severity of Illness scale score ≥ 4, despite up to 2 adequate trials of an SSRI/SNRI and compliance confirmed by positive SSRI/SNRI blood levels, were randomized to decoglurant 5 mg (n = 101), 15 mg (n = 102), or 30 mg (n = 55) daily or placebo (n = 99) as adjunct to ongoing treatment with 1 SSRI/SNRI. An adaptive design was used with an interim analysis after 30 patients in each group had received 6 weeks' treatment. The primary outcome variable was change in MADRS total score from baseline to end of treatment. Primary assessments were performed by fully blinded centralized raters. RESULTS: Of 357 participants, 310 completed 6 weeks' treatment. At 6 weeks, no significant differences between any active treatment arm and placebo in reducing MADRS total score or response or remission rates were observed. Decoglurant exerted no significant effects on Cambridge Neuropsychological Test Automated Battery cognitive accuracy and cognitive speed composite scores or on secondary measures of mood and functioning. A relatively high placebo response was observed, which may have constrained the ability to detect treatment effects. No deaths occurred; few patients reported serious adverse events. CONCLUSIONS: Decoglurant was well tolerated overall but did not exert any antidepressant or procognitive effects. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01457677.

Correction to: Exploring Social Biomarkers in High­Functioning Adults with Autism and Asperger's Versus Healthy Controls: A Cross­Sectional Analysis.

The original version of this article unfortunately contained a mistake in CI values in Table 2.

Exploring Social Biomarkers in High-Functioning Adults with Autism and Asperger's Versus Healthy Controls: A Cross-Sectional Analysis.

Biomarkers for autism spectrum disorder (ASD) are lacking but would facilitate drug development for the core deficits of the disorder. We evaluated markers proposed for characterization of differences in social communication and interaction in adults with ASD versus healthy controls (HC) for utility as biomarkers. Data pooled from an observational study and baseline data from a placebo-controlled study were analyzed. Between-group differences were observed in eye-tracking tasks for activity monitoring, biomotion, human activity preference, composite score (p = 0.0001-0.037) and pupillometry (various tasks, p = 0.017-0.05). Impaired olfaction was more common in the ASD sample versus HC (p = 0.018). Our preliminary results suggest the potential use for stratification and response sub-analyses outcome-prediction of specific eye-tracking tasks, pupillometry and olfaction tests in ASD trials.

In Search of Biomarkers for Autism Spectrum Disorder.

Autism Spectrum Disorder (ASD) lacks validated measures of core social functions across development stages suitable for clinical trials. We assessed the concurrent validity between ASD clinical measures and putative biomarkers of core deficits, and their feasibility of implementation in human studies. Datasets from two adult ASD studies were combined (observational study [n = 19] and interventional study baseline data [n = 19]). Potential biomarkers included eye-tracking, olfaction, and auditory and visual emotion recognition assessed via the Affective Speech Recognition test (ASR) and Reading-the-Mind-in-the-Eyes Test (RMET). Current functioning was assessed with intelligence quotient (IQ), adaptive skill testing, and behavioral ratings. Autism severity was determined by the Autism Diagnostic Observation Scale-2 and Social Communication Interaction Test (SCIT). Exploratory measures showed varying significant associations across ASD severity, adaptive skills, and behavior. Eye tracking endpoints showed little relationship to adaptive ability but correlated with severity and behavior. ASR scores significantly correlated with most adaptive behavior domains, as well as severity. Olfaction predicted visual and auditory emotion recognition. SCIT scores related moderately to multiple severity domains, and was the only measure not related with IQ. RMET accuracy was less related to ASD features. Eye tracking, SCIT, and ASR showed high test-retest reliability. We documented associations of proximal biomarkers of social functioning with multiple ASD dimensions. With the exception of SCIT, most correlations were modest, limiting utility as proxy measures of social communication. Feasibility and reliability were high for eye-tracking, ASR, and SCIT. Overall, several novel experimental paradigms showed potential as social biomarkers or surrogate markers in ASD. Autism Research 2018, 11: 1567-1579. © 2018 The Authors. Autism Research published by International Society for Autism Research and Wiley Periodicals, Inc. LAY SUMMARY: More accurate measurements of treatment effects are needed to help the development of new drug treatments for autism spectrum disorders (ASD). This study evaluates the relationship between assessments designed to measure behaviors associated with social communication and cognition in ASD with clinical and diagnostic assessments of symptom severity as well as their implementation. The assessments including eye-tracking, auditory and visual social stimuli recognition, and olfaction identification showed potential for use in the evaluation of treatments for social difficulties in ASD.

Cerebral blood flow predicts differential neurotransmitter activity.

Application of metabolic magnetic resonance imaging measures such as cerebral blood flow in translational medicine is limited by the unknown link of observed alterations to specific neurophysiological processes. In particular, the sensitivity of cerebral blood flow to activity changes in specific neurotransmitter systems remains unclear. We address this question by probing cerebral blood flow in healthy volunteers using seven established drugs with known dopaminergic, serotonergic, glutamatergic and GABAergic mechanisms of action. We use a novel framework aimed at disentangling the observed effects to contribution from underlying neurotransmitter systems. We find for all evaluated compounds a reliable spatial link of respective cerebral blood flow changes with underlying neurotransmitter receptor densities corresponding to their primary mechanisms of action. The strength of these associations with receptor density is mediated by respective drug affinities. These findings suggest that cerebral blood flow is a sensitive brain-wide in-vivo assay of metabolic demands across a variety of neurotransmitter systems in humans.

A Single Dose, Randomized, Controlled Proof-Of-Mechanism Study of a Novel Vasopressin 1a Receptor Antagonist (RG7713) in High-Functioning Adults with Autism Spectrum Disorder.

This corrects the article DOI: 10.1038/npp.2016.232.

A Single Dose, Randomized, Controlled Proof-Of-Mechanism Study of a Novel Vasopressin 1a Receptor Antagonist (RG7713) in High-Functioning Adults with Autism Spectrum Disorder.

The core symptoms of autism spectrum disorder (ASD) include impaired social communication, repetitive behaviors, and restricted interests. No effective pharmacotherapy for these core deficits exists. Within the domain of social communication, the vasopressin system is implicated in social cognition and social signaling deficits of ASD, and represents a potential therapeutic target. We assessed the effects of a single 20 mg intravenous dose of the arginine vasopressin receptor 1A (V1a) antagonist, RG7713, on exploratory biomarkers (eye tracking), behavioral and clinical measures of social cognition and communication (affective speech recognition (ASR), reading the mind in the eyes, olfactory identification, scripted interaction), and safety and tolerability in a multicenter, randomized, double-blind, placebo-controlled, cross-over study of 19 high-functioning adult male subjects with DSM-IV Autistic Disorder (age 18-45 years; full scale IQ >70; ABC-Irritability subscale ⩽13). Eye-tracking showed an increase in biological motion orienting preference with RG7713 (ES=0.8, p=0.047) and a non-significant improvement in the composite score (ES=0.2, p=0.29). RG7713 reduced ability to detect lust (ES=-0.8, p=0.03) and fear (ES=-0.7, p=0.07) in ASR. However, when all eight individual emotion subscales were combined into an overall ASR performance score, the reduction was non-significant (ES=-0.1, p=0.59). Thirteen adverse events were reported in 10 subjects; all were of mild (11/13) or moderate (2/13) severity. Although interpretation should be cautious due to multiple comparisons and small sample size, these results provide preliminary evidence from experimental and behavioral biomarkers, that blockade of the V1a receptor may improve social communication in adults with high-functioning ASD. ClinicalTrials.gov identifier: NCT01474278 A Study of RO5028442 in Adult Male High-Functioning Autistic Patients. Available at: https://clinicaltrials.gov/ct2/show/NCT01474278.

Clinical population pharmacokinetics and toxicodynamics of linezolid.

Thrombocytopenia is a common side effect of linezolid, an oxazolidinone antibiotic often used to treat multidrug-resistant Gram-positive bacterial infections. Various risk factors have been suggested, including linezolid dose and duration of therapy, baseline platelet counts, and renal dysfunction; still, the mechanisms behind this potentially treatment-limiting toxicity are largely unknown. A clinical study was conducted to investigate the relationship between linezolid pharmacokinetics and toxicodynamics and inform strategies to prevent and manage linezolid-associated toxicity. Forty-one patients received 42 separate treatment courses of linezolid (600 mg every 12 h). A new mechanism-based, population pharmacokinetic/toxicodynamic model was developed to describe the time course of plasma linezolid concentrations and platelets. A linezolid concentration of 8.06 mg/liter (101% between-patient variability) inhibited the synthesis of platelet precursor cells by 50%. Simulations predicted treatment durations of 5 and 7 days to carry a substantially lower risk than 10- to 28-day therapy for platelet nadirs of <100 ×10(9)/liter. The risk for toxicity did not differ noticeably between 14 and 28 days of therapy and was significantly higher for patients with lower baseline platelet counts. Due to the increased risk of toxicity after longer durations of linezolid therapy and large between-patient variability, close monitoring of patients for development of toxicity is important. Dose individualization based on plasma linezolid concentration profiles and platelet counts should be considered to minimize linezolid-associated thrombocytopenia. Overall, oxazolidinone therapy over 5 to 7 days even at relatively high doses was predicted to be as safe as 10-day therapy of 600 mg linezolid every 12 h.

Assessment of neuropsychiatric adverse events in influenza patients treated with oseltamivir: a comprehensive review.

After reports from Japan of neuropsychiatric adverse events (NPAEs) in children taking oseltamivir phosphate (hereafter referred to as oseltamivir [Tamiflu; F. Hoffmann-La Roche Ltd, Basel, Switzerland]) during and after the 2004--5 influenza season, Roche explored possible reasons for the increase in reporting rate and presented regular updates to the US FDA and other regulatory authorities. This review summarizes the results of a comprehensive assessment of the company's own preclinical and clinical studies, post-marketing spontaneous adverse event reporting, epidemiological investigations utilizing health claims and medical records databases and an extensive review of the literature, with the aim of answering the following questions: (i) what the types and rates of neuropsychiatric abnormalities reported in patients with influenza are, and whether these differ in patients who have received oseltamivir compared with those who have not; (ii) what levels of oseltamivir and its active metabolite, oseltamivir carboxylate are achieved in the CNS; (iii) whether oseltamivir and oseltamivir carboxylate have pharmacological activity in the CNS; and (iv) whether there are genetic differences between Japanese and Caucasian patients that result in different levels of oseltamivir and/or oseltamivir carboxylate in the CNS, differences in their metabolism or differences in their pharmacological activity in the CNS. In total, 3051 spontaneous reports of NPAEs were received by Roche, involving 2466 patients who received oseltamivir between 1999 and 15 September 2007; 2772 (90.9%) events originated from Japan, 190 (6.2%) from the US and 89 (2.9%) from other countries. During this period, oseltamivir was prescribed to around 48 million people worldwide. Crude NPAE reporting rates (per 1,000,000 prescriptions) in children (aged < or =16 years) and adults, respectively, were 99 and 28 events in Japan and 19 and 8 in the US. NPAEs were more commonly reported in children (2218 events in 1808 children aged < or =16 years vs 833 in 658 adults) and generally occurred within 48 hours of the onset of influenza illness and initiation of treatment. After categorizing the reported events according to International Classification of Diseases (9th edition) codes, abnormal behaviour (1160 events, 38.0%) and delusions/perceptual disturbances (661 events, 21.7%) were the largest categories of events, and delirium or delirium-like events (as defined by the American Psychiatric Association) were very common in most categories. No difference in NPAE reporting rates between oseltamivir and placebo was found in phase III treatment studies (0.5% vs 0.6%). Analyses of US healthcare claims databases showed the risk of NPAEs in oseltamivir-treated patients (n = 159,386) was no higher than those not receiving antivirals (n = 159,386). Analysis of medical records in the UK General Practice Research Database showed that the adjusted relative risk of NPAEs in influenza patients was significantly higher (1.75-fold) than in the general population. Based on literature reports, NPAEs in Japanese and Taiwanese children with influenza have occurred before the initiation of oseltamivir treatment; events were also similar to those occurring after the initiation of oseltamivir therapy. No clinically relevant differences in plasma pharmacokinetics of oseltamivir and its active metabolite oseltamivir carboxylate were noted between Japanese and Caucasian adults or children. Penetration into the CNS of both oseltamivir and oseltamivir carboxylate was low in Japanese and Caucasian adults (cerebrospinal fluid/plasma maximum concentration and area under the plasma concentration-time curve ratios of approximately 0.03), and the capacity for converting oseltamivir to oseltamivir carboxylate in rat and human brains was low. In animal autoradiography and pharmacokinetic studies, brain : plasma radioactivity ratios were generally 20% or lower. Animal studies showed no specific CNS/behavioural effects after administration of doses corresponding to > or =100 times the clinical dose. Oseltamivir or oseltamivir carboxylate did not interact with human neuraminidases or with 155 known molecular targets in radioligand binding and functional assays. A review of the information published to date on functional variations of genes relevant to oseltamivir pharmacokinetics and pharmacodynamics and simulated gene knock-out scenarios did not identify any plausible genetic explanations for the observed NPAEs. The available data do not suggest that the incidence of NPAEs in influenza patients receiving oseltamivir is higher than in those who do not, and no mechanism by which oseltamivir or oseltamivir carboxylate could cause or worsen such events could be identified.

Population pharmacokinetics of oseltamivir when coadministered with probenecid.

Oseltamivir is a potent, selective, oral neuraminidase inhibitor for the treatment and prophylaxis of influenza. Plasma concentrations of the active metabolite, oseltamivir carboxylate, are increased in the presence of probenecid, suggesting that the combination could allow for the use of reduced doses of oseltamivir. To investigate this proposal, we developed a population pharmacokinetic model and simulated the pharmacokinetics of candidate combination regimens of oral oseltamivir (45 mg and 30 mg twice a day) plus oral probenecid (500 mg/6 hourly). Probenecid plus oseltamivir 45 mg achieved all the pharmacokinetic parameters expected of oseltamivir alone, but combination with oseltamivir 30 mg and dose interval extension approaches did not. An oseltamivir-probenecid combination may compromise tolerability and enhance the potential for drug interactions. In addition, increased dosing requirements may affect compliance and attainment of optimal oseltamivir exposure, potentially facilitating the emergence of viral strains with reduced susceptibility to oseltamivir. These factors, set alongside increased capacity for oseltamivir production, should be carefully considered before an oseltamivir-probenecid combination is used.

Pharmacokinetic/pharmacodynamic factors influencing emergence of resistance to linezolid in an in vitro model.

Emerging resistance threatens the usefulness of linezolid for the treatment of severe infections caused by multidrug-resistant gram-positive bacteria. Optimal pharmacokinetic (PK)/pharmacodynamic (PD) indices have been described for the antimicrobial efficacy of linezolid (area under the concentration-time curve over 24 h at steady state divided by the MIC, >100; the cumulative percentage of a 24-h period that the drug concentration exceeds the MIC under steady-state PK conditions, >85). The aim of this study was to investigate the influence of these PK/PD indices on the development of resistance to linezolid by using an in vitro PK/PD model. Four dosage regimens were simulated over 72 h (two intermittent bolus regimens of 600 mg every 12 h [q12h] and 120 mg q12h and two continuous-infusion regimens of 120 mg/24 h and 30 mg/24 h) against four reference strains: methicillin-resistant Staphylococcus aureus (MRSA), heteroresistant vancomycin-intermediate S. aureus (hVISA), vancomycin-intermediate S. aureus (VISA), and vancomycin-resistant Enterococcus faecium (VRE). Linezolid concentrations were measured by high-performance liquid chromatography. Changes in susceptibility were characterized by pre- and posttreatment MIC measurements and population analysis profiles (PAPs). The linezolid concentrations that were achieved closely matched those that were targeted. The simulation with 600 mg q12h provided a >3-log10 reduction in the number of CFU/ml for all four strains, as did the 120-mg-q12h regimen for hVISA and VISA and the 30-mg/24-h continuous infusion for VRE and VISA. After 72 h of exposure to the 120-mg/24-h continuous-infusion simulation, the area under the PAP curve for all strains increased substantially (40 to 178%); increases in the MICs for the MRSA and hVISA strains were observed. The results demonstrate that PK/PD considerations are important in optimizing both antibacterial activity and the development of resistance to linezolid. The potential for resistance development appears to be higher when a constant concentration is maintained in the vicinity of the MIC of the bacteria.

Successful treatment and cerebrospinal fluid penetration of oral linezolid in a patient with coagulase-negative Staphylococcus ventriculitis.

OBJECTIVE: To describe a case of coagulase-negative Staphylococcus ventriculitis successfully treated with oral linezolid, for which good cerebrospinal fluid (CSF) penetration was observed. CASE SUMMARY: A 69-year-old man had an extraventricular drain inserted following a right cerebellar infarct. On day 6, the CSF culture was positive for coagulase-negative staphylococci; intravenous vancomycin 1 g daily was initiated to treat ventriculitis. A ventriculoperitoneal shunt, inserted on day 35 to manage communicating hydrocephalus, was subsequently removed as symptoms suggesting infection presented. Coagulase-negative Staphylococcus was isolated from shunt reservoir aspirate, and intrathecal vancomycin 10 mg daily was added to the treatment regimen. On day 61, vancomycin was stopped and oral linezolid 600 mg twice daily was started. Linezolid was discontinued 22 days later, with no evidence of ongoing infection. Four blood samples were collected around the seventh dose of linezolid and 5 CSF samples were collected on separate days during treatment. Linezolid concentrations were measured in plasma and CSF by HPLC. Using an ADAPT II maximum a priori Bayesian estimator module, a 2 compartment pharmacokinetic model was fitted to the plasma linezolid concentration data and CSF:predicted plasma concentration ratios (ranging from 0.27 to 1.02) were derived. All CSF concentrations exceeded the reported 90% minimum inhibitory concentration of 2 mg/L for linezolid against coagulase-negative staphylococci. DISCUSSION: Evidence of the effectiveness of linezolid against central nervous system infections is growing; however, limited data exist describing its CSF penetration. Oral linezolid exhibited good CSF penetration in this patient, which corresponded to positive clinical response. CONCLUSIONS: Oral linezolid may play a valuable role in the treatment of multiresistant gram-positive central nervous system infections.

High-performance liquid chromatographic method for simple and rapid determination of linezolid in human plasma.

A simple high-performance liquid chromatographic (HPLC) method was developed and validated for rapid quantification of linezolid in human plasma. Protein precipitation using a mixture of 5% trichloroacetic acid and methanol (3:1, v/v) provided a straightforward method of sample preparation and the internal standard eperezolid was employed. A concentration range from 0.20 to 40.0 mg/L was utilized to construct calibration curves, and analysis of low- (0.40 mg/L), medium- (7.50 mg/L) and high-quality (25.0 mg/L) control samples revealed excellent reproducibility (

Responses to neither exogenous nor endogenous endothelin-1 are altered in patients with hypercholesterolemia.

There is some controversy regarding whether vascular responses to endothelin are altered in hypercholesterolemia. Studies performed to date have been compromised by the use of endothelin antagonists at inappropriate concentrations. In the current study, we examine the role of endothelin-1 in hypercholesterolemic patients using lower, more selective doses of specific endothelin antagonists. Twenty-two patients with hypercholesterolemia (total plasma cholesterol > 6.0 mmol/l) and 17 healthy controls were recruited. Forearm vascular responses to endothelin-1 (5 pmol/min), the endothelin A antagonist BQ-123 (10 nmol/min), and the endothelin B antagonist BQ-788 (1 nmol/min) were obtained. Endothelin-1 caused a significant vasoconstriction in both hypercholesterolemic and control subjects, an effect that was not significantly different between the two groups (P = 0.784). BQ-123 caused a significant vasodilatation that was not significantly different between the two groups (P = 0.899). Similarly, responses to BQ-788 (P = 0.774) and mean plasma endothelin-1 levels were not different (control vs. hypercholesterolemia, 1.16 +/- 0.18 vs. 1.06 +/- 0.15 fmol/ml; P = 0.64). Responses to neither exogenous nor endogenous endothelin are influenced by plasma cholesterol levels in humans. It is thus unlikely that the endothelin system contributes to early vascular disease pathology in patients with hypercholesterolemia.