tat-nr2b9c and Stroke

Cationic arginine-rich peptides represent a novel class of peptides being developed as neuroprotective agents for stroke and other acute and chronic neurological disorders. As a group, cationic arginine-rich peptides have a diverse range of other biological properties including the ability to traverse cell membranes, modulate immune responses, antagonise ion channel receptor function, as well as possessing cardioprotective, anti-nociceptive, anti-microbial and anti-cancer properties. A sound understanding of their safety profile is essential for the design of future clinical trials and for ensuring translational success with these compounds. At present, while many neuroprotective cationic arginine-rich peptides have been examined in preclinical animal neuroprotection studies, few have been assessed in human safety studies. Despite this, the safety of the prototypical cationic arginine-rich peptide, protamine, which has been in clinical use for over 70 years to reverse the anticoagulant effects of heparin and as an excipient in certain insulin preparations, is well established. In addition, the poly-arginine peptide R9 (ALX40-4C) was developed as an anti-human inmmunodeficiency virus therapeutic in the mid-1990s, and more recently, the neuroprotective cationic arginine-rich peptides TAT-NR2B9c (NA-1), CN-105 and RD2 are being evaluated for the treatment of ischaemic stroke, haemorrhagic stroke and Alzheimer's disease, respectively. Based on the available clinical data, cationic arginine-rich peptides as a group appear to be safe when administered at therapeutic doses by a slow intravenous infusion. While protamine, owing to its isolation from salmon milt and homology with human sperm protamine, can trigger anaphylactic and anaphylactoid reactions in a small proportion of patients previously exposed to the peptide (e.g. diabetic patients), who are allergic to fish or have undergone a vasectomy, such reactions are unlikely to be triggered in individuals exposed to non-protamine cationic arginine-rich peptides.

Topics: Humans; Neuroprotective Agents; Peptides; Stroke

Stroke creates a complex interplay of multiple signaing pathways including excitotoxicity, ionic imbalance, inflammation, oxidative stress and apoptosis. There are very few treatments that have been shown to be beneficial in acute stroke. Recent findings have provided insights into the pathophysiology and mechanisms of ischemic stroke, complementing the traditional glutamate hypothesis: the molecular interaction between PSD95 and GluN2B has been identified as a culprit in stroke-mediated excitotoxicity, leading to the discovery of NA-1, a peptide that disrupts that interaction, as a potent neuroprotective agent for the treatment of acute stroke. In this review we describe its signaling cascade, the target of its therapeutic intervention and its translation from bench to clinical trial.

Topics: Animals; Clinical Trials as Topic; Disks Large Homolog 4 Protein; Drug Discovery; Humans; Neuroprotective Agents; Peptides; Protein Binding; Receptors, N-Methyl-D-Aspartate; Stroke

Excitotoxicity, a pathological process caused by over-stimulation of ionotropic glutamate receptors, is a major cause of neuronal loss in acute and chronic neurological conditions such as ischaemic stroke, Alzheimer's and Huntington's diseases. Effective neuroprotective drugs to reduce excitotoxic neuronal loss in patients suffering from these neurological conditions are urgently needed. One avenue to achieve this goal is to clearly define the intracellular events mediating the neurotoxic signals originating from the over-stimulated glutamate receptors in neurons. In this review, we first focus on the key cellular events directing neuronal death but not involved in normal physiological processes in the neurotoxic signalling pathways. These events, referred to as pathologically activated events, are potential targets for the development of neuroprotectant therapeutics. Inhibitors blocking some of the known pathologically activated cellular events have been proven to be effective in reducing stroke-induced brain damage in animal models. Notable examples are inhibitors suppressing the ion channel activity of neurotoxic glutamate receptors and those disrupting interactions of specific cellular proteins occurring only in neurons undergoing excitotoxic cell death. Among them, Tat-NR2B9c and memantine are clinically effective in reducing brain damage caused by some acute and chronic neurological conditions. Our second focus is evaluation of the suitability of the other inhibitors for use as neuroprotective therapeutics. We also discuss the experimental approaches suitable for bridging our knowledge gap in our current understanding of the excitotoxic signalling mechanism in neurons and discovery of new pathologically activated cellular events as potential targets for neuroprotection.

Topics: Animals; Cell Death; Humans; Memantine; Neurons; Neuroprotective Agents; Peptides; Signal Transduction; Stroke

Topics: Animals; Disks Large Homolog 4 Protein; Humans; Intracellular Signaling Peptides and Proteins; Membrane Proteins; Peptides; Stem Cell Transplantation; Stroke; Translational Research, Biomedical

Neuroprotection with NA-1 (Tat-NR2B9c), an inhibitor of postsynaptic density-95 protein, has been shown in a primate model of stroke. We assessed whether NA-1 could reduce ischaemic brain damage in human beings.. For this double-blind, randomised, controlled study, we enrolled patients aged 18 years or older who had a ruptured or unruptured intracranial aneurysm amenable to endovascular repair from 14 hospitals in Canada and the USA. We used a computer-generated randomisation sequence to allocate patients to receive an intravenous infusion of either NA-1 or saline control at the end of their endovascular procedure (1:1; stratified by site, age, and aneurysm status). Both patients and investigators were masked to treatment allocation. The primary outcome was safety and primary clinical outcomes were the number and volume of new ischaemic strokes defined by MRI at 12-95 h after infusion. We used a modified intention-to-treat (mITT) analysis. This trial is registered with ClinicalTrials.gov, number NCT00728182.. Between Sept 16, 2008, and March 30, 2011, we randomly allocated 197 patients to treatment-12 individuals did not receive treatment because they were found to be ineligible after randomisation, so the mITT population consisted of 185 individuals, 92 in the NA-1 group and 93 in the placebo group. Two minor adverse events were adjudged to be associated with NA-1; no serious adverse events were attributable to NA-1. We recorded no difference between groups in the volume of lesions by either diffusion-weighted MRI (adjusted p value=0·120) or fluid-attenuated inversion recovery MRI (adjusted p value=0·236). Patients in the NA-1 group sustained fewer ischaemic infarcts than did patients in the placebo group, as gauged by diffusion-weighted MRI (adjusted incidence rate ratio 0·53, 95% CI 0·38-0·74) and fluid-attenuated inversion recovery MRI (0·59, 0·42-0·83).. Our findings suggest that neuroprotection in human ischaemic stroke is possible and that it should be investigated in larger trials.. NoNO Inc and Arbor Vita Corp.

Topics: Adult; Aged; Brain Ischemia; Double-Blind Method; Endovascular Procedures; Female; Humans; Iatrogenic Disease; Intracranial Aneurysm; Male; Middle Aged; Neuroprotective Agents; Peptides; Placebos; Stroke; Treatment Outcome

We have previously demonstrated that R18 and its d-enantiomer, R18D, are neuroprotective at 24 hours following intraluminal filament occlusion of the middle cerebral artery (MCAO) in the rat. This study examined R18 and R18D effectiveness in improving functional outcomes at up to 56 days poststroke following endothelin-1-induced MCAO. Peptides were administered intravenously at doses of 100, 300, or 1000 nmol/kg, 60 minutes after MCAO. Functional recovery poststroke was assessed using multiple forelimb placing tests and horizontal ladder test, and NA-1 (TAT-NR2B9c), a neuroprotective currently in phase 3 clinical stroke trials, was used as a benchmark. The study demonstrated that R18 (300 and 1000 nmol/kg) was the most effective peptide in improving functional outcomes, followed by R18D (300 and 1000 nmol/kg), and NA-1 (300 and 100 nmol/kg). Furthermore, R18 at doses of 300 and 1000 nmol/kg was the most effective agent in restoring pre-stroke body weight, while R18 and R18D at doses of 300 and 1000 nmol/kg, but not NA-1 also significantly reduced the number of animals requiring hand feeding 48 hours after stroke. This study confirms that R18 and R18D are effective in improving long-term functional outcomes after stroke, and suggests that R18 may be more effective than NA-1.

Topics: Animals; Endothelin-1; Infusions, Intravenous; Intracellular Signaling Peptides and Proteins; Male; Peptides; Rats; Rats, Sprague-Dawley; Recovery of Function; Stroke; Treatment Outcome

Following positive results with the poly-arginine peptide R18 when administered intravenously 30 or 60min after permanent and/or transient middle cerebral artery occlusion (MCAO; 90min) in the rat, we examined the effectiveness of the peptide when administered 2h after MCAO. R18 was administered intravenously (1000nmol/kg via jugular vein) after permanent MCAO or a transient 3-h MCAO or when administered intra-arterially (100nmol/kg via internal carotid artery) immediately after reperfusion following a transient 2-h MCAO. In the transient MCAO studies, the neuroprotective NA-1 peptide was used as a positive control. Infarct volume, cerebral edema and functional outcomes were measured 24h after MCAO. Following permanent or transient MCAO, neither R18 nor NA-1 significantly reduced infarct volume. However, following permanent MCAO, R18 appeared to reduce cerebral edema (p=0.006), whereas following a transient 3-h MCAO, R18 improved the time to remove adhesive tape (p=0.04) without significantly affecting cerebral edema. There was also a trend (p=0.07) towards improved rota-rod performance with R18 in both permanent and transient 3-h MCAO. Following a transient 2-h MCAO, R18 had no significant effects on cerebral edema or neurological score but did lessen the extent of weight loss. Overall, while R18 had no effect on infarct volume, the peptide reduced cerebral edema after permanent MCAO, and improved some functional outcomes after transient MCAO.

Topics: Animals; Brain Edema; Brain Ischemia; Carotid Artery Injuries; Carotid Artery, Internal; Cerebral Arteries; Cerebrovascular Disorders; Disease Models, Animal; Infarction, Middle Cerebral Artery; Intracellular Signaling Peptides and Proteins; Ischemic Attack, Transient; Male; Neuroprotective Agents; Peptides; Rats; Reperfusion; Stroke

Previous studies reported that Tat-NR2B9c, a peptide disrupting the N-methyl-d-aspartate receptor-postsynaptic density protein-95 interaction, reduced ischemic damage in the acute phase after stroke. However, its effect in the subacute phase is unknown. The aim of this study is to determine whether disrupting the N-methyl-d-aspartate receptor-postsynaptic density protein-95 interaction in the subacute phase promotes recovery after stroke.. Studies were performed on Sprague-Dawley rats or nNOS(-/-) mice, and experimental ischemic stroke was induced by middle cerebral artery occlusion. Animals were treated with drugs starting at day 4 after ischemia. Sensorimotor functions and spatial learning and memory ability were assessed after drug treatment. Then, rats were euthanized for morphological observation and biochemical tests.. Disrupting the N-methyl-d-aspartate receptor-postsynaptic density protein-95 interaction with Tat-HA-NR2B9c significantly ameliorated the ischemia-induced impairments of spatial memory and sensorimotor functions in rats during subacute stage but did not improve stroke outcome in nNOS(-/-) mice. Consistent with the functional recovery, Tat-HA-NR2B9c substantially increased neurogenesis in the dentate gyrus and dendritic spine density of mature neurons in the motor cortex of rats, meanwhile, reversed the ischemia-induced formation of S-nitrosylation-cyclin-dependent kinase 5 and increased cyclin-dependent kinase 5 activity in ipsilateral hippocampus. However, directly blocking N-methyl-d-aspartate receptors with MK-801 or Ro 25-6981 did not show the beneficial effects above.. Dissociating N-methyl-d-aspartate receptor-postsynaptic density protein-95 coupling by Tat-HA-NR2B9c in the subacute phase after stroke promotes functional recovery, probably because of that it increases neurogenesis and dendritic spine density of mature neurons via regulating cyclin-dependent kinase 5 in the ischemic brain.

Topics: Animals; Brain Ischemia; Cognition; Cyclin-Dependent Kinase 5; Dendritic Spines; Dentate Gyrus; Disks Large Homolog 4 Protein; Intracellular Signaling Peptides and Proteins; Male; Maze Learning; Membrane Proteins; Motor Cortex; Neurogenesis; Neuroprotective Agents; Nitric Oxide Synthase Type I; Peptides; Psychomotor Performance; Rats; Rats, Sprague-Dawley; Recovery of Function; Sensation; Stroke

Topics: Animals; Brain; Humans; Neuroprotective Agents; Peptides; Stroke

All attempts at treating strokes by pharmacologically reducing the human brain's vulnerability to ischaemia have failed, leaving stroke as a leading cause of death, disability and massive socioeconomic loss worldwide. Over decades, research has failed to translate over 1,000 experimental treatments from discovery in cells and rodents to use in humans, a scientific crisis that gave rise to the prevailing belief that pharmacological neuroprotection is not feasible or practicable in higher-order brains. To provide a strategy for advancing stroke therapy, we used higher-order gyrencephalic non-human primates, which bear genetic, anatomical and behavioural similarities to humans and tested neuroprotection by PSD-95 inhibitors--promising compounds that uncouple postsynaptic density protein PSD-95 from neurotoxic signalling pathways. Here we show that stroke damage can be prevented in non-human primates in which a PSD-95 inhibitor is administered after stroke onset in clinically relevant situations. This treatment reduced infarct volumes as gauged by magnetic resonance imaging and histology, preserved the capacity of ischaemic cells to maintain gene transcription in genome-wide screens of ischaemic brain tissue, and significantly preserved neurological function in neurobehavioural assays. The degree of tissue neuroprotection by magnetic resonance imaging corresponded strongly to the preservation of neurological function, supporting the intuitive but unproven dictum that integrity of brain tissue can reflect functional outcome. Our findings establish that tissue neuroprotection and improved functional outcome after stroke is unequivocally achievable in gyrencephalic non-human primates treated with PSD-95 inhibitors. Efforts must ensue to translate these findings to humans.

Topics: Animals; Brain; Disks Large Homolog 4 Protein; Humans; Infarction, Middle Cerebral Artery; Intracellular Signaling Peptides and Proteins; Macaca fascicularis; Magnetic Resonance Imaging; Male; Membrane Proteins; Peptides; Stroke; Time Factors; Treatment Outcome

Over decades, all attempts to translate acute stroke neuroprotectants from discovery in lower-order species to human clinical use have failed. This raised concerns about the predictive validity of preclinical studies in animals for outcomes in human stroke trials. To bridge this translational gap, we used high-order gyrencephalic nonhuman primates subjected to an experimental protocol that mimicked that of a corresponding, separately reported, clinical trial in which the human subjects underwent endovascular cerebral aneurysm repair. Both placebo-controlled studies tested neuroprotection by Tat-NR2B9c, a prospective therapeutic compound, in anesthetized subjects. Embolic strokes were produced by small intra-arterial emboli caused by the endovascular procedure. We show that primates treated with Tat-NR2B9c after the onset of embolic strokes exhibited significantly reduced numbers and volumes of strokes, as visualized by diffusion- and T2-weighted magnetic resonance imaging. These results correctly anticipated the outcome of the corresponding human trial, thus validating this study design as a predictor of neuroprotective efficacy in humans. This strategy may facilitate the evaluation of promising neuroprotectants before undertaking similar studies in human subjects.

Topics: Animals; Disease Models, Animal; Magnetic Resonance Imaging; Neuroprotective Agents; Peptides; Primates; Stroke

Topics: Endovascular Procedures; Female; Humans; Intracranial Aneurysm; Male; Peptides; Stroke