The potential of 1H-MRS in CNS drug development.

RATIONALE: Proton magnetic resonance spectroscopy (1H-MRS) is a cross-species neuroimaging technique that can measure concentrations of several brain metabolites, including glutamate and GABA. This non-invasive method has promise in developing centrally acting drugs, as it can be performed repeatedly within-subjects and be used to translate findings from the preclinical to clinical laboratory using the same imaging biomarker. OBJECTIVES: This review focuses on the utility of single-voxel 1H-MRS in developing novel glutamatergic or GABAergic drugs for the treatment of psychiatric disorders and includes research performed in rodent models, healthy volunteers and patient cohorts. RESULTS: Overall, these studies indicate that 1H-MRS is able to detect the predicted pharmacological effects of glutamatergic or GABAergic drugs on voxel glutamate or GABA concentrations, although there is a shortage of studies examining dose-related effects. Clinical studies have applied 1H-MRS to better understand drug therapeutic mechanisms, including the glutamatergic effects of ketamine in depression and of acamprosate in alcohol dependence. There is an emerging interest in identifying patient subgroups with 'high' or 'low' brain regional 1H-MRS glutamate levels for more targeted drug development, which may require ancillary biomarkers to improve the accuracy of subgroup discrimination. CONCLUSIONS: Considerations for future research include the sensitivity of single-voxel 1H-MRS in detecting drug effects, inter-site measurement reliability and the interpretation of drug-induced changes in 1H-MRS metabolites relative to the known pharmacological molecular mechanisms. On-going technological development, in single-voxel 1H-MRS and in related complementary techniques, will further support applications within CNS drug discovery.

Application of Healthcare 'Big Data' in CNS Drug Research: The Example of the Neurological and mental health Global Epidemiology Network (NeuroGEN).

Neurological and psychiatric (mental health) disorders have a large impact on health burden globally. Cognitive disorders (including dementia) and stroke are leading causes of disability. Mental health disorders, including depression, contribute up to one-third of total years lived with disability. The Neurological and mental health Global Epidemiology Network (NeuroGEN) is an international multi-database network that harnesses administrative and electronic medical records from Australia, Asia, Europe and North America. Using these databases NeuroGEN will investigate medication use and health outcomes in neurological and mental health disorders. A key objective of NeuroGEN is to facilitate high-quality observational studies to address evidence-practice gaps where randomized controlled trials do not provide sufficient information on medication benefits and risks that is specific to vulnerable population groups. International multi-database research facilitates comparisons across geographical areas and jurisdictions, increases statistical power to investigate small subpopulations or rare outcomes, permits early post-approval assessment of safety and effectiveness, and increases generalisability of results. Through bringing together international researchers in pharmacoepidemiology, NeuroGEN has the potential to be paradigm-changing for observational research to inform evidence-based prescribing. The first focus of NeuroGEN will be to address evidence-gaps in the treatment of chronic comorbidities in people with dementia.

Formulation and evaluation of nano lipid formulation containing CNS acting drug: molecular docking, in-vitro assessment and bioactivity detail in rats.

The study performed molecular docking, formulated, characterized thymoquinone (TQ) loaded solid lipid nano particles (TQSLN) and exhibited comparative antidepressant activity. TQ loaded nano lipid formulations were prepared by solvent injection methods and characterize for different in-vitro parameters. The optimized formulation was evaluated for depression using unpredictable chronic mild stress (UCMS) model for a period of six weeks. TQSLN was assessed in modified forced swim test (MFST), tail suspension test (TST), locomotor activity followed by biochemical parameters such as monoaminesand brain derived neurotrophic factor (BDNF). The results of molecular docking study revealed that TQ has shown greater affinity and tighter binding capacity for the active site of neurotransmitter receptors. TQSLN showed nanometric size, optimum zeta potential with high percent encapsulation and lower poly dispersity index (PDI). Transmission electron microscopy (TEM) images showed spherical shape without aggregation and agglomeration of particles. The in-vivo study result revealed that the higher amount of TQ reaches to the target region by showing higher levels of monoamines 5 hydroxytryptamine (5-HT), dopamine (DA) and norepinephrine (NE) as compared to thymoquinone suspension (TQS) in brain. In conclusion, the nano lipid formulation remarkably improved the bio-efficacy of TQ and demonstrated a promising perspective for oral delivery of poorly water-soluble drugs.

Effects on Hedonic Feeding, Energy Expenditure and Balance of the Non-opioid Peptide DYN-A2-17.

The dynorphin (DYN) peptide family includes opioid and non-opioid peptides, yet the physiological role of the non-opioid DYN peptides remains poorly understood. Recent evidence shows that administering the non-opioid peptide DYN-A2-17 into the paraventricular hypothalamic nucleus (PVN) simultaneously increased short-term intake of standard rodent chow and spontaneous physical activity (SPA). The present studies aimed to expand upon the mechanisms and role of DYN-A2-17 on food intake and energy expenditure. Injection of DYN-A2-17 in PVN increased SPA, energy expenditure and wheel running in the absence of food. Repeated DYN-A2-17 injection in PVN increased short-term chow intake, but this effect habituated over time and failed to alter cumulative food intake, body weight or adiposity. Pre-treatment with a CRF receptor antagonist into PVN blocked the effects of DYN-A2-17 on food intake while injection of DYN-A2-17 in PVN increased plasma ACTH. Finally, as DYN peptides are co-released with orexin peptides, we compared the effects of DYN-A2-17 to orexin-A and the opioid peptide DYN-A1-13 on food choice and intake in PVN when palatable snacks and chow were available. DYN-A1-13 selectively increased intake of palatable snacks. DYN-A2-17 and orexin-A decreased palatable snack intake while orexin-A also increased chow intake. These findings demonstrate that the non-opioid peptide DYN-A2-17 acutely regulates physical activity, energy expenditure and food intake without long-term effects on energy balance. These data also propose different roles of opioid, non-opioid DYN and orexin peptides on food choice and intake when palatable and non-palatable food options are available.

1-cyclohexyl-x-methoxybenzene derivatives, novel psychoactive substances seized on the internet market. Synthesis and in vivo pharmacological studies in mice.

INTRODUCTION: Among novel psychoactive substances notified to EMCDDA and Europol were 1-cyclohexyl-x-methoxybenzene stereoisomers (ortho, meta, and para). These substances share some structural characteristics with phencyclidine and tramadol. Nowadays, no information on the pharmacological and toxicological effects evoked by 1-cyclohexyl-x-methoxybenzene are reported. The aim of this study was to investigate the effect evoked by each one stereoisomer on visual stimulation, body temperature, acute thermal pain, and motor activity in mice. METHODS: Mice were evaluated in behavioral tests carried out in a consecutive manner according to the following time scheme: observation of visual placing response, measures of core body temperature, determination of acute thermal pain, and stimulated motor activity. RESULTS: All three stereoisomers dose-dependent inhibit visual placing response (rank order: meta > ortho > para), induce hyperthermia at lower and hypothermia at higher doses (meta > ortho > para) and cause analgesia to thermal stimuli (para > meta = ortho), while they do not alter motor activity. CONCLUSIONS: For the first time, this study demonstrates that systemic administration of 1-cyclohexyl-x-methoxybenzene compounds markedly inhibit visual response, promote analgesia, and induce core temperature alterations in mice. This data, although obtained in animal model, suggest their possible hazard for human health (i.e., hyperthermia and sensorimotor alterations). In particular, these novel psychoactive substances may have a negative impact in many daily activities, greatly increasing the risk factors for workplace accidents and traffic injuries.

Assessment of Ex Vivo Transport Function in Isolated Rodent Brain Capillaries.

The blood-brain barrier plays an important role in neuroprotection; however, it can be a major obstacle for drug delivery to the brain. This barrier primarily resides in the brain capillaries and functions as an interface between the brain and peripheral blood circulation. Several anatomical and biochemical elements of the blood-brain barrier are essential to regulate the permeability of nutrients, ions, hormones, toxic metabolites, and xenobiotics into and out of the brain. In particular, high expression of ATP-driven efflux transporters at the blood-brain barrier is a major obstacle in the delivery of CNS pharmacotherapeutics to the brain. The complete understanding of these elements can offer insights on how to modulate barrier functions for neuroprotection against CNS drug toxicity and to enhance drug delivery to the brain. In the literature, preclinical models of the blood-brain barrier are widely utilized to predict drug pharmacokinetics and pharmacodynamics properties in the brain. In addition, these models are essential tools to investigate cellular mechanisms and novel interventions that alter barrier function and permeability. This unit presents procedures to isolate fresh and viable rodent brain capillaries for the assessment of ex vivo transport activity at the blood-brain barrier. © 2017 by John Wiley & Sons, Inc.

Role of Academic Drug Discovery in the Quest for New CNS Therapeutics.

There was a greater than 50% decline in central nervous system (CNS) drug discovery and development programs by major pharmaceutical companies from 2009 to 2014. This decline was paralleled by a rise in the number of university led drug discovery centers, many in the CNS area, and a growth in the number of public-private drug discovery partnerships. Diverse operating models have emerged as the academic drug discovery centers adapt to this changing ecosystem.

True alignment of preclinical and clinical research to enhance success in CNS drug development: a review of the current evidence.

Central nervous system pharmacological research and development has reached a critical turning point. Patients suffering from disorders afflicting the central nervous system are numerous and command significant attention from the pharmaceutical industry. However, given the numerous failures of promising drugs, many companies are no longer investing in or, indeed, are divesting from this therapeutic area. Central nervous system drug development must change in order to develop effective therapies to treat these patients. Preclinical research is a cornerstone of drug development; however, it is frequently criticised for its lack of predictive validity. Animal models and assays can be shown to be more predictive than reported and, on many occasions, the lack of thorough preclinical testing is potentially to blame for some of the clinical failures. Important factors such as translational aspects, nature of animal models, variances in acute versus chronic dosing, development of add-on therapies and understanding of the full dose-response relationship are too often neglected. Reducing the attrition rate in central nervous system drug development could be achieved by addressing these important questions before novel compounds enter the clinical phase. This review illustrates the relevance of employing these criteria to translational central nervous system research, better to ensure success in developing new drugs in this therapeutic area.

From blood-brain barrier to blood-brain interface: new opportunities for CNS drug delivery.

One of the biggest challenges in the development of therapeutics for central nervous system (CNS) disorders is achieving sufficient blood-brain barrier (BBB) penetration. Research in the past few decades has revealed that the BBB is not only a substantial barrier for drug delivery to the CNS but also a complex, dynamic interface that adapts to the needs of the CNS, responds to physiological changes, and is affected by and can even promote disease. This complexity confounds simple strategies for drug delivery to the CNS, but provides a wealth of opportunities and approaches for drug development. Here, I review some of the most important areas that have recently redefined the BBB and discuss how they can be applied to the development of CNS therapeutics.

Species differences in behavior and cell proliferation/survival in the adult brains of female meadow and prairie voles.

Microtine rodents display diverse patterns of social organization and behaviors, and thus provide a useful model for studying the effects of the social environment on physiology and behavior. The current study compared the species differences and the effects of oxytocin (OT) on anxiety-like, social affiliation, and social recognition behaviors in female meadow voles (Microtus pennsylvanicus) and prairie voles (Microtus ochrogaster). Furthermore, cell proliferation and survival in the brains of adult female meadow and prairie voles were compared. We found that female meadow voles displayed a higher level of anxiety-like behavior but lower levels of social affiliation and social recognition compared to female prairie voles. In addition, meadow voles showed lower levels of cell proliferation (measured by Ki67 staining) and cell survival (measured by BrdU staining) in the ventromedial hypothalamus (VMH) and amygdala (AMY), but not the dentate gyrus of the hippocampus (DG), than prairie voles. Interestingly, the numbers of new cells in the VMH and AMY, but not DG, also correlated with anxiety-like, social affiliation, and social recognition behaviors in a brain region-specific manner. Finally, central OT treatment (200 ng/kg, icv) did not lead to changes in behavior or cell proliferation/survival in the brain. Together, these data indicate a potential role of cell proliferation/survival in selected brain areas on different behaviors between vole species with distinct life strategies.

A simple assessment model to quantifying the dynamic hippocampal neurogenic process in the adult mammalian brain.

Adult hippocampal neurogenesis is a highly dynamic process in which new cells are born, but only some of which survive. Of late it has become clear that these surviving newborn neurons have functional roles, most notably in certain forms of memory. Conventional methods to look at adult neurogenesis are based on the quantification of the number of newly born neurons using a simple cell counting methodology. However, this type of approach fails to capture the dynamic aspects of the neurogenic process, where neural proliferation, death and differentiation take place continuously and simultaneously. In this paper, we propose a simple mathematical approach to better understand the adult neurogenic process in the hippocampus which in turn will allow for a better analysis of this process in disease states and following drug therapies.

Evaluation of multiple comparison correction procedures in drug assessment studies using LORETA maps.

The identification of the brain regions involved in the neuropharmacological action is a potential procedure for drug development. These regions are commonly determined by the voxels showing significant statistical differences after comparing placebo-induced effects with drug-elicited effects. LORETA is an electroencephalography (EEG) source imaging technique frequently used to identify brain structures affected by the drug. The aim of the present study was to evaluate different methods for the correction of multiple comparisons in the LORETA maps. These methods which have been commonly used in neuroimaging and also simulated studies have been applied on a real case of pharmaco-EEG study where the effects of increasing benzodiazepine doses on the central nervous system measured by LORETA were investigated. Data consisted of EEG recordings obtained from nine volunteers who received single oral doses of alprazolam 0.25, 0.5, and 1 mg, and placebo in a randomized crossover double-blind design. The identification of active regions was highly dependent on the selected multiple test correction procedure. The combined criteria approach known as cluster mass was useful to reveal that increasing drug doses led to higher intensity and spread of the pharmacologically induced changes in intracerebral current density.

Optimizing early Go/No Go decisions in CNS drug development.

Go/No Go decisions concerning development of any single compound determine investment in increasingly costly studies from Phases I-III. Such decisions are problematic for CNS drug development where the variety of molecular targets in the brain have stimulated decades of studies without major therapeutic advances. Many costly studies do not even yield interpretable results as to whether the mechanism being pursued has therapeutic potential. Therefore, both industry and the public sector have implemented a decision making strategy based on whether a compound can test a molecular hypothesis of drug action. One requires, at a minimum, compelling evidence in humans that a compound both interacts with its presumed molecular targets in brain and ideally documents a CNS functional consequence of the interaction prior to efficacy studies. This strategy will much more quickly rule out ineffective mechanisms although it does not address the problem of poorly predictive models of novel CNS drug efficacy.

Use of functional imaging across clinical phases in CNS drug development.

The use of novel brain biomarkers using nuclear magnetic resonance imaging holds potential of making central nervous system (CNS) drug development more efficient. By evaluating changes in brain function in the disease state or drug effects on brain function, the technology opens up the possibility of obtaining objective data on drug effects in the living awake brain. By providing objective data, imaging may improve the probability of success of identifying useful drugs to treat CNS diseases across all clinical phases (I-IV) of drug development. The evolution of functional imaging and the promise it holds to contribute to drug development will require the development of standards (including good imaging practice), but, if well integrated into drug development, functional imaging can define markers of CNS penetration, drug dosing and target engagement (even for drugs that are not amenable to positron emission tomography imaging) in phase I; differentiate objective measures of efficacy and side effects and responders vs non-responders in phase II, evaluate differences between placebo and drug in phase III trials and provide insights into disease modification in phase IV trials.

PK/PD assessment in CNS drug discovery: Prediction of CSF concentration in rodents for P-glycoprotein substrates and application to in vivo potency estimation.

The unbound drug concentration in brain parenchyma is considered to be the relevant driver for interaction with central nervous system (CNS) biological targets. Drug levels in cerebrospinal fluid (C_CSF) are frequently used surrogates for the unbound concentrations in brain. For drugs actively transported across the blood-brain barrier (BBB), C_CSF differs from unbound plasma concentration (Cu_p) to an extent that is commonly unknown. In this study, the relationship between CSF-to-unbound plasma drug partitioning in rats and the mouse Pgp (Mdr1a) efflux ratio (ER) obtained from in vitro transcellular studies has been investigated for a set of 61 CNS compounds exhibiting substantial diversity in chemical structure and physico-chemical properties. In order to understand the in vitro-in vivo extrapolation of Pgp efflux, a mechanistic model was derived relating in vivo CNS distribution kinetics to in vitro active transport. The model was applied to predict C_CSF from Cu_p and ER data for 19 proprietary Roche CNS drug candidates. The calculated CSF concentrations were correlated with CNS pharmacodynamic responses observed in rodent models. The correlation between in vitro and in vivo potency for different pharmacological endpoints indicated that the predicted C_CSF is a valuable surrogate of the concentration at the target site. Overall, C_CSF proved superior description of PK/PD data than unbound plasma or total brain concentration for Mdr1a substrates. Predicted C_CSF can be used as a default approach to understand the PK/PD relationships in CNS efficacy models and can support the extrapolation of efficacious brain exposure for new drug candidates from rodent to man.

Neuromapping techniques in drug discovery: pharmacological MRI for the assessment of novel antipsychotics.

INTRODUCTION: Treatment of psychiatric and neurological diseases represents a substantial unmet medical need, but the development of novel, effective and safe drugs is proving difficult. While substantial improvement over existing pharmacological agents is expected from new molecular targets emerging in the genomic era, the validation and exploitation of novel mechanisms of action is a lengthy and costly process. The use of neuroimaging techniques, and more specifically of functional and pharmacological magnetic resonance imaging (MRI), has been advocated as a powerful approach to this problem, providing translational biomarkers for the objective assessment of drug activity on brain function, and possibly surrogate markers of clinical response. AREAS COVERED: The authors review the recent application of functional and pharmacological MRI (phMRI) in the study of novel treatments of psychosis based on glutamatergic mechanisms. Furthermore, they review contribution of functional imaging in the target validation and early assessment of drugs exploiting glutamatergic mechanisms as an example of potentially impactful exploitation of neuroimaging methods in drug discovery. EXPERT OPINION: While functional neuroimaging methods may provide useful markers of drug activity and response to treatment, their translational potential, that is, their use to bridge animal and human investigations is seldom exploited. The application of phMRI in the study of novel antipsychotics based on glutamatergic mechanisms represents an example of functional neuroimaging as a powerful means to link preclinical and clinical research, thus providing a paradigm that may help expedite progression into the clinical phase of novel mechanisms for the treatment of psychiatric and neurological diseases.