Nogo receptor decoy promotes recovery and corticospinal growth in non-human primate spinal cord injury.

After CNS trauma such as spinal cord injury, the ability of surviving neural elements to sprout axons, reorganize neural networks and support recovery of function is severely restricted, contributing to chronic neurological deficits. Among limitations on neural recovery are myelin-associated inhibitors functioning as ligands for neuronal Nogo receptor 1 (NgR1). A soluble decoy (NgR1-Fc, AXER-204) blocks these ligands and provides a means to promote recovery of function in multiple preclinical rodent models of spinal cord injury. However, the safety and efficacy of this reagent in non-human primate spinal cord injury and its toxicological profile have not been described. Here, we provide evidence that chronic intrathecal and intravenous administration of NgR1-Fc to cynomolgus monkey and to rat are without evident toxicity at doses of 20 mg and greater every other day (≥2.0 mg/kg/day), and far greater than the projected human dose. Adult female African green monkeys underwent right C5/6 lateral hemisection with evidence of persistent disuse of the right forelimb during feeding and right hindlimb during locomotion. At 1 month post-injury, the animals were randomized to treatment with vehicle (n = 6) or 0.10-0.17 mg/kg/day of NgR1-Fc (n = 8) delivered via intrathecal lumbar catheter and osmotic minipump for 4 months. One animal was removed from the study because of surgical complications of the catheter, but no treatment-related adverse events were noted in either group. Animal behaviour was evaluated at 6-7 months post-injury, i.e. 1-2 months after treatment cessation. The use of the impaired forelimb during spontaneous feeding and the impaired hindlimb during locomotion were both significantly greater in the treatment group. Tissue collected at 7-12 months post-injury showed no significant differences in lesion size, fibrotic scar, gliosis or neuroinflammation between groups. Serotoninergic raphespinal fibres below the lesion showed no deficit, with equal density on the lesioned and intact side below the level of the injury in both groups. Corticospinal axons traced from biotin-dextran-amine injections in the left motor cortex were equally labelled across groups and reduced caudal to the injury. The NgR1-Fc group tissue exhibited a significant 2-3-fold increased corticospinal axon density in the cervical cord below the level of the injury relative to the vehicle group. The data show that NgR1-Fc does not have preclinical toxicological issues in healthy animals or safety concerns in spinal cord injury animals. Thus, it presents as a potential therapeutic for spinal cord injury with evidence for behavioural improvement and growth of injured pathways in non-human primate spinal cord injury.

Rescue of Transgenic Alzheimer's Pathophysiology by Polymeric Cellular Prion Protein Antagonists.

Cellular prion protein (PrPC) binds the scrapie conformation of PrP (PrPSc) and oligomeric ß-amyloid peptide (Aßo) to mediate transmissible spongiform encephalopathy (TSE) and Alzheimer's disease (AD), respectively. We conducted cellular and biochemical screens for compounds blocking PrPC interaction with Aßo. A polymeric degradant of an antibiotic targets Aßo binding sites on PrPC with low nanomolar affinity and prevents Aßo-induced pathophysiology. We then identified a range of negatively charged polymers with specific PrPC affinity in the low to sub-nanomolar range, from both biological (melanin) and synthetic (poly [4-styrenesulfonic acid-co-maleic acid], PSCMA) origin. Association of PSCMA with PrPC prevents Aßo/PrPC-hydrogel formation, blocks Aßo binding to neurons, and abrogates PrPSc production by ScN2a cells. We show that oral PSCMA yields effective brain concentrations and rescues APPswe/PS1ΔE9 transgenic mice from AD-related synapse loss and memory deficits. Thus, an orally active PrPC-directed polymeric agent provides a potential therapeutic approach to address neurodegeneration in AD and TSE.

The newly developed CRF1-receptor antagonists, NGD 98-2 and NGD 9002, suppress acute stress-induced stimulation of colonic motor function and visceral hypersensitivity in rats.

Corticotropin releasing factor receptor 1 (CRF1) is the key receptor that mediates stress-related body responses. However to date there are no CRF1 antagonists that have shown clinical efficacy in stress-related diseases. We investigated the inhibitory effects of a new generation, topology 2 selective CRF1 antagonists, NGD 98-2 and NGD 9002 on exogenous and endogenous CRF-induced stimulation of colonic function and visceral hypersensitivity to colorectal distension (CRD) in conscious rats. CRF1 antagonists or vehicle were administered orogastrically (og) or subcutaneously (sc) before either intracerebroventricular (icv) or intraperitoneal (ip) injection of CRF (10 µg/kg), exposure to water avoidance stress (WAS, 60 min) or repeated CRD (60 mmHg twice, 10 min on/off at a 30 min interval). Fecal pellet output (FPO), diarrhea and visceromotor responses were monitored. In vehicle (og)-pretreated rats, icv CRF stimulated FPO and induced diarrhea in >50% of rats. NGD 98-2 or NGD 9002 (3, 10 and 30 mg/kg, og) reduced the CRF-induced FPO response with an inhibitory IC50 of 15.7 and 4.3 mg/kg respectively. At the highest dose, og NGD 98-2 or NGD 9002 blocked icv CRF-induced FPO by 67-87% and decreased WAS-induced-FPO by 23-53%. When administered sc, NGD 98-2 or NGD 9002 (30 mg/kg) inhibited icv and ip CRF-induced-FPO. The antagonists also prevented the development of nociceptive hyper-responsivity to repeated CRD. These data demonstrate that topology 2 CRF1 antagonists, NGD 98-2 and NGD 9002, administered orally, prevented icv CRF-induced colonic secretomotor stimulation, reduced acute WAS-induced defecation and blocked the induction of visceral sensitization to repeated CRD.

Targeting memory processes with drugs to prevent or cure PTSD.

INTRODUCTION: Post-traumatic stress disorder (PTSD) is a chronic debilitating psychiatric disorder resulting from exposure to a severe traumatic stressor and an area of great unmet medical need. Advances in pharmacological treatments beyond the currently approved SSRIs are needed. AREAS COVERED: Background on PTSD, as well as the neurobiology of stress responding and fear conditioning, is provided. Clinical and preclinical data for investigational agents with diverse pharmacological mechanisms are summarized. EXPERT OPINION: Advances in the understanding of stress biology and mechanisms of fear conditioning plasticity provide a rationale for treatment approaches that may reduce hyperarousal and dysfunctional aversive memories in PTSD. One challenge is to determine if these components are independent or reflect a common underlying neurobiological alteration. Numerous agents reviewed have potential for reducing PTSD core symptoms or targeted symptoms in chronic PTSD. Promising early data support drug approaches that seek to disrupt dysfunctional aversive memories by interfering with consolidation soon after trauma exposure, or in chronic PTSD, by blocking reconsolidation and/or enhancing extinction. Challenges remain for achieving selectivity when attempting to alter aversive memories. Targeting the underlying traumatic memory with a combination of pharmacological therapies applied with appropriate chronicity, and in combination with psychotherapy, is expected to substantially improve PTSD treatment.

Discovery of N-(1-ethylpropyl)-[3-methoxy-5-(2-methoxy-4-trifluoromethoxyphenyl)-6-methyl-pyrazin-2-yl]amine 59 (NGD 98-2): an orally active corticotropin releasing factor-1 (CRF-1) receptor antagonist.

The design, synthesis, and structure-activity relationships of a novel series of pyrazines, acting as corticotropin releasing factor-1 (CRF-1) receptor antagonists, are described. Synthetic methodologies were developed to prepare a number of substituted pyrazine cores utilizing regioselective halogenation and chemoselective derivatization. Noteworthy, an efficient 5-step synthesis was developed for the lead compound 59 (NGD 98-2), which required no chromatography. Compound 59 was characterized as an orally bioavailable, brain penetrant, and highly selective CRF-1 receptor antagonist. Occupancy of rat brain CRF-1 receptors was quantified using ex vivo receptor occupancy assays, using both brain tissue homogenates as well as brain slices receptor autoradiography. Behaviorally, oral administration of 59 significantly antagonized CRF-induced locomotor activity at doses as low as 10 mg/kg and dose-dependently reduced the restraint stress-induced ACTH increases.

Emergence of anti-conflict effects of zolpidem in rhesus monkeys following extended post-injection intervals.

RATIONALE: Zolpidem is a hypnotic drug that binds to γ-aminobutyric acid type A receptors but lacks consistently demonstrable anxiolytic efficacy. METHODS: Rhesus monkeys (N = 4) were trained under a multiple schedule in which food-maintained responding was programmed (18-response fixed ratio) for a 5-min period, followed by a 5-min period in which the food-maintained responding was suppressed by response-contingent electric shock (20-response fixed ratio). Doses of zolpidem (range = 0.03 to 1.0 mg/kg, i.v.) were administered 5 min before the session, and responding was re-assessed at three additional 20-min intervals. A similar experiment also was carried out with the non-selective benzodiazepine, triazolam, over a dose range of 0.001 to 0.1 mg/kg, i.v. RESULTS: Zolpidem did not engender a significant increase in average rates of suppressed responding at earlier time points; however, rates of non-suppressed responding were robustly decreased. At 45- and 65-min post-injection, zolpidem treatment resulted in a dose-dependent increase in rates of suppressed responding. In contrast, the non-selective benzodiazepine triazolam increased rates of suppressed responding in a dose-dependent manner at all four time points, although decreases in non-suppressed responding were less at the later time points. CONCLUSIONS: These findings suggest that zolpidem has anxiolytic-like effects, but only >25 min after i.v. injection in this rhesus monkey conflict model. It was hypothesized that time-dependent effects on the response rate-suppressing properties of zolpidem become tolerant (i.e., acute tolerance). Because anxiolytic-like effects remain stable throughout the session, the absence of rate-decreasing effects may "unmask" anti-conflict effects.

Identification and characterization of NDT 9513727 [N,N-bis(1,3-benzodioxol-5-ylmethyl)-1-butyl-2,4-diphenyl-1H-imidazole-5-methanamine], a novel, orally bioavailable C5a receptor inverse agonist.

The complement system represents an innate immune mechanism of host defense that has three effector arms, the C3a receptor, the C5a receptor (C5aR), and the membrane attack complex. Because of its inflammatory and immune-enhancing properties, the biological activity of C5a and its classical receptor have been widely studied. Because specific antagonism of the C5aR could have therapeutic benefit without affecting the protective immune response, the C5aR continues to be a promising target for pharmaceutical research. The lack of specific, potent and orally bioavailable small-molecule antagonists has limited the clinical investigation of the C5aR. We report the discovery of NDT 9513727 [N,N-bis(1,3-benzodioxol-5-ylmethyl)-1-butyl-2,4-diphenyl-1H-imidazole-5-methanamine], a small-molecule, orally bioavailable, selective, and potent inverse agonist of the human C5aR. NDT 9513727 was discovered based on the integrated use of in vitro affinity and functional assays in conjunction with medicinal chemistry. NDT 9513727 inhibited C5a-stimulated responses, including guanosine 5'-3-O-(thio)triphosphate binding, Ca(2+) mobilization, oxidative burst, degranulation, cell surface CD11b expression and chemotaxis in various cell types with IC(50)s from 1.1 to 9.2 nM, respectively. In C5a competition radioligand binding experiments, NDT 9513727 exhibited an IC(50) of 11.6 nM. NDT 9513727 effectively inhibited C5a-induced neutropenia in gerbil and cynomolgus macaque in vivo. The findings suggest that NDT 9513727 may be a promising new entity for the treatment of human inflammatory diseases.

Aminopyrazine CB1 receptor inverse agonists.

A series of 5,6-diaryl-2-amino-pyrazines were prepared and found to have antagonist-like properties at the CB1 receptor. Subsequent SAR studies optimized both receptor potency and drug-like properties including solubility and Cytochrome-P450 inhibition potential. Optimized compounds were demonstrated to be inverse agonists and compared in vivo with rimonabant for their ability to inhibit food intake, to occupy central CB1 receptors and to influence hormonal markers associated with obesity.