Therapeutic effects of melatonin receptor agonists on sleep and comorbid disorders.

Several melatonin receptors agonists (ramelteon, prolonged-release melatonin, agomelatine and tasimelteon) have recently become available for the treatment of insomnia, depression and circadian rhythms sleep-wake disorders. The efficacy and safety profiles of these compounds in the treatment of the indicated disorders are reviewed. Accumulating evidence indicates that sleep-wake disorders and co-existing medical conditions are mutually exacerbating. This understanding has now been incorporated into the new Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5). Therefore, when evaluating the risk/benefit ratio of sleep drugs, it is pertinent to also evaluate their effects on wake and comorbid condition. Beneficial effects of melatonin receptor agonists on comorbid neurological, psychiatric, cardiovascular and metabolic symptomatology beyond sleep regulation are also described. The review underlines the beneficial value of enhancing physiological sleep in comorbid conditions.

Quantitative structure-activity relationship analysis of ß-amyloid aggregation inhibitors.

Inhibiting the aggregation process of the ß-amyloid peptide is a promising strategy in treating Alzheimer's disease. In this work, we have collected a dataset of 80 small molecules with known inhibition levels and utilized them to develop two comprehensive quantitative structure-activity relationship models: a Bayesian model and a decision tree model. These models have exhibited high predictive accuracy: 87% of the training and test sets using the Bayesian model and 89 and 93% of the training and test sets, respectively, by the decision tree model. Subsequently these models were used to predict the activities of several new potential ß-amyloid aggregation inhibitors and these predictions were indeed validated by in vitro experiments. Key chemical features correlated with the inhibition ability were identified. These include the electro-topological state of carbonyl groups, AlogP and the number of hydrogen bond donor groups. The results demonstrate the feasibility of the developed models as tools for rapid screening, which could help in the design of novel potential drug candidates for Alzheimer's disease.

Cognitive-performance recovery of Alzheimer's disease model mice by modulation of early soluble amyloidal assemblies.

A rationally designed oligomerization inhibitor interacts with early intermediate assemblies of amyloid-beta polypeptide (Abeta) through the aromatic elements and inhibits their assembly into the toxic oligomers that cause Alzheimer's disease by a unique C(alpha)-methylation beta-breakage strategy. The electrostatic potential of the low-energy conformation of the dipeptide inhibitor bound to Abeta is shown.

Safety, Tolerability, and Pharmacokinetics of Single Ascending Doses of ELX-02, a Potential Treatment for Genetic Disorders Caused by Nonsense Mutations, in Healthy Volunteers.

ELX-02 is an investigational synthetic eukaryotic ribosome-selective glycoside optimized as a translational read-through molecule that induces read through of nonsense mutations, resulting in normally localized full-length functional proteins. ELX-02 is being developed as a therapy for genetic diseases caused by nonsense mutations. Two phase 1a, randomized, double-blind placebo-controlled, single-ascending-dose studies were conducted in healthy human subjects to evaluate the safety and pharmacokinetics of ELX-02. Single subcutaneously injected doses of ELX-02 between 0.3 mg/kg and 7.5 mg/kg showed an acceptable safety profile without severe or serious drug-related adverse events, including a lack of renal and ototoxicity events. Injection of ELX-02 resulted in a rapid time to peak concentration and elimination phase, with complete elimination from the vascular compartment within 10 hours. ELX-02 area under the concentration-time curve to infinity showed dose-exposure linearity (24-fold increase for a 25-fold dose increase), and the maximum concentration showed dose proportionality (17-fold increase for a 25-fold increase). The mean apparent volume of distribution was dose dependent, suggesting an increased distribution and tissue uptake of ELX-02 at higher doses. The primary route of excretion was in the urine, with the majority of the compound excreted unchanged. These results support the evaluation of the safety, pharmacokinetics, and efficacy of repeat dosing in future studies.

Efficacy and Safety of Pediatric Prolonged-Release Melatonin for Insomnia in Children With Autism Spectrum Disorder.

OBJECTIVE: To assess the efficacy and safety of novel pediatric-appropriate, prolonged-release melatonin minitablets (PedPRM) versus placebo for insomnia in children and adolescents with autism spectrum disorder (ASD), with or without attention-deficit/hyperactivity disorder (ADHD) comorbidity, and neurogenetic disorders (NGD). METHOD: A total of 125 children and adolescents (2-17.5 years of age; 96.8% ASD, 3.2% Smith-Magenis syndrome [SMS]) whose sleep failed to improve on behavioral intervention alone were randomized (1:1 ratio), double-blind, to receive PedPRM (2 mg escalated to 5 mg) or placebo for 13 weeks. Sleep measures included the validated caregivers' Sleep and Nap Diary (SND) and Composite Sleep Disturbance Index (CSDI). The a priori primary endpoint was SND-reported total sleep time (TST) after 13 weeks of treatment. RESULTS: The study met the primary endpoint: after 13 weeks of double-blind treatment, participants slept on average 57.5 minutes longer at night with PedPRM compared to 9.14 minutes with placebo (adjusted mean treatment difference PedPRM-placebo -32.43 minutes; p = .034). Sleep latency (SL) decreased by 39.6 minutes on average with PedPRM and 12.5 minutes with placebo (adjusted mean treatment difference -25.30 minutes; p = .011) without causing earlier wakeup time. The rate of participants attaining clinically meaningful responses in TST and/or SL was significantly higher with PedPRM than with placebo (68.9% versus 39.3% respectively; p = .001) corresponding to a number needed to treat (NNT) of 3.38. Overall sleep disturbance (CSDI) tended to decrease. PedPRM was generally safe; somnolence was more commonly reported with PedPRM than placebo. CONCLUSION: PedPRM was efficacious and safe for treatment of insomnia in children and adolescents with ASD with/without ADHD and NGD. The acceptability of this pediatric formulation in a population who usually experience significant difficulties in swallowing was remarkably high. Clinical trial registration information-Efficacy and Safety of Circadin in the Treatment of Sleep Disturbances in Children With Neurodevelopment Disabilities; http://clinicaltrials.gov/; NCT01906866.

Diphenylalanine as a Reductionist Model for the Mechanistic Characterization of ß-Amyloid Modulators.

The phenomenon of protein aggregation into amyloid fibrils is associated with a large number of major diseases of unrelated etiology. Unraveling the mechanism of amyloid self-assembly and identifying therapeutic directions to control this process are of utmost importance. Research in this field has been hampered by several challenges, including reproducibility, low protein purification yields, and the inherent aggregation propensity of amyloidogenic proteins, making them extremely difficult to study. Herein, on the basis of the similarity in the assembly mechanism, as well as the physical, chemical, and biological characteristics, of diphenylalanine nanostructures and aromatic amino acid containing amyloid fibrils, we report a simple, yet robust peptide-based platform that could be used for screening of small molecules potentially capable of interfering with the aggregation process and for mechanistic exploration of their mode of action. The system was validated using four small-molecule inhibitors, and the effect was examined via turbidity assay, thioflavin T fluorescence, and electron microscopy. The aggregation profile of diphenylalanine was very similar to that of ß-amyloid polypeptide in the presence of the modulators. Rosmarinic acid emerged as an extremely potent inhibitor and a destabilizer of the aggregates. The effect of stoichiometric variation of rosmarinic acid on the process of destabilization was also probed using a microfluidic technique. Finally, the formation of equimolar complexes of diphenylalanine and inhibitors was detected using mass spectrometry. This approach not only provides a system for high-throughput screening of possible inhibitor molecules from larger libraries of modulators, but is also highly useful for understanding the mechanistic aspects of the interactions leading to the process of inhibition.

Apoptosis induced by islet amyloid polypeptide soluble oligomers is neutralized by diabetes-associated specific antibodies.

Soluble oligomeric assemblies of amyloidal proteins appear to act as major pathological agents in several degenerative disorders. Isolation and characterization of these oligomers is a pivotal step towards determination of their pathological relevance. Here we describe the isolation of Type 2 diabetes-associated islet amyloid polypeptide soluble cytotoxic oligomers; these oligomers induced apoptosis in cultured pancreatic cells, permeated model lipid vesicles and interacted with cell membranes following complete internalization. Moreover, antibodies which specifically recognized these assemblies, but not monomers or amyloid fibrils, were exclusively identified in diabetic patients and were shown to neutralize the apoptotic effect induced by these oligomers. Our findings support the notion that human IAPP peptide can form highly toxic oligomers. The presence of antibodies identified in the serum of diabetic patients confirms the pathological relevance of the oligomers. In addition, the newly identified structural epitopes may also provide new mechanistic insights and a molecular target for future therapy.

Add-on prolonged-release melatonin for cognitive function and sleep in mild to moderate Alzheimer's disease: a 6-month, randomized, placebo-controlled, multicenter trial.

PURPOSE: A link between poor sleep quality and Alzheimer's disease (AD) has recently been suggested. Since endogenous melatonin levels are already reduced at preclinical AD stages, it is important to ask whether replenishing the missing hormone would be beneficial in AD and whether any such effects would be related to the presence of sleep disorder in patients. PATIENTS AND METHODS: The effects of add-on prolonged-release melatonin (PRM) (2 mg) to standard therapy on cognitive functioning and sleep were investigated in 80 patients (men [50.7%], women [49.3%], average age 75.3 years [range, 52-85 years]) diagnosed with mild to moderate AD, with and without insomnia comorbidity, and receiving standard therapy (acetylcholinesterase inhibitors with or without memantine). In this randomized, double-blind, parallel-group study, patients were treated for 2 weeks with placebo and then randomized (1:1) to receive 2 mg of PRM or placebo nightly for 24 weeks, followed by 2 weeks placebo. The AD Assessment Scale-Cognition (ADAS-Cog), Instrumental Activities of Daily Living (IADL), Mini-Mental State Examination (MMSE), sleep, as assessed by the Pittsburgh Sleep Quality Index (PSQI) and a daily sleep diary, and safety parameters were measured. RESULTS: Patients treated with PRM (24 weeks) had significantly better cognitive performance than those treated with placebo, as measured by the IADL (P=0.004) and MMSE (P=0.044). Mean ADAS-Cog did not differ between the groups. Sleep efficiency, as measured by the PSQI, component 4, was also better with PRM (P=0.017). In the comorbid insomnia (PSQI ≥6) subgroup, PRM treatment resulted in significant and clinically meaningful effects versus the placebo, in mean IADL (P=0.032), MMSE score (+1.5 versus -3 points) (P=0.0177), and sleep efficiency (P=0.04). Median ADAS-Cog values (-3.5 versus +3 points) (P=0.045) were significantly better with PRM. Differences were more significant at longer treatment duration. PRM was well tolerated, with an adverse event profile similar to that of placebo. CONCLUSION: Add-on PRM has positive effects on cognitive functioning and sleep maintenance in AD patients compared with placebo, particularly in those with insomnia comorbidity. The results suggest a possible causal link between poor sleep and cognitive decline.

The generic amyloid formation inhibition effect of a designed small aromatic ß-breaking peptide.

The development of generic inhibitors in order to control the formation of amyloid fibrils and early oligomers is still an unmet medical need. As it is hypothesized that amyloid assemblies represent a generic protein supramolecular structure of low free energy, targeting the key molecular recognition and self-assembly events may provide the route for the development of such potential therapeutic agents. We have previously demonstrated the ability of hybrid molecules composed of an aromatic moiety and the α-aminoisobutyric acid ß-sheet breaker elements to act as excellent inhibitors of amyloid fibril formation. Specifically, the D-Trp-Aib was shown to be a superb inhibitor of the formation of Alzheimer's disease ß-amyloid fibrils and oligomers both in vitro and in vivo. Here, we demonstrate that the rationally designed molecule has the generic ability to inhibit amyloid fibril formation by calcitonin, α-synuclein, and the islet amyloid polypeptide. Moreover, we demonstrate the inability of two modified peptides, D-Ala-Aib and D-Trp-Ala, to inhibit and disassemble amyloid fibril formation, a fact that provides an additional evidence for the suggested structural basis of the inhibitor activity. Taken together, we believe that the use of ß-breaker elements combined with aromatic moiety may present a promising approach for the development of fibrillization inhibition drug candidate.

Structural basis for inhibiting ß-amyloid oligomerization by a non-coded ß-breaker-substituted endomorphin analogue.

The distribution of endomorphins (EM) 1 and 2 in the human brain inversely correlates with cerebral neurodegeneration in Alzheimer's disease (AD), implying a protective role. These endogenous opioid peptides incorporate aromatic residues and a ß-breaker motif, as seen in several optimized inhibitors of Aß aggregation. The activity of native endomorphins was studied, as well as the rationally designed analogue Aib-1, which includes a remarkably efficient ß-breaker, α-aminoisobutyric acid (Aib). In vitro and GFP fusion protein assays showed that Aib-1 interacted with Aß and markedly inhibited the formation of toxic oligomer and fibril growth. Moreover, Aib-1 prevented the toxicity of Aß toward neuronal PC12 cells and markedly rectified reduced longevity of an AD fly model. Atomistic simulations and NMR-derived solution structures revealed that Aib-1 significantly reduced the propensity of Aß to aggregate due to multimode interactions including aromatic, hydrophobic, and polar contacts. We suggest that hindering the self-assembly process by interfering with the aromatic core of amyloidogenic peptides may pave the way toward developing therapeutic agents to treat amyloid-associated diseases.

Orally administrated cinnamon extract reduces ß-amyloid oligomerization and corrects cognitive impairment in Alzheimer's disease animal models.

An increasing body of evidence indicates that accumulation of soluble oligomeric assemblies of ß-amyloid polypeptide (Aß) play a key role in Alzheimer's disease (AD) pathology. Specifically, 56 kDa oligomeric species were shown to be correlated with impaired cognitive function in AD model mice. Several reports have documented the inhibition of Aß plaque formation by compounds from natural sources. Yet, evidence for the ability of common edible elements to modulate Aß oligomerization remains an unmet challenge. Here we identify a natural substance, based on cinnamon extract (CEppt), which markedly inhibits the formation of toxic Aß oligomers and prevents the toxicity of Aß on neuronal PC12 cells. When administered to an AD fly model, CEppt rectified their reduced longevity, fully recovered their locomotion defects and totally abolished tetrameric species of Aß in their brain. Furthermore, oral administration of CEppt to an aggressive AD transgenic mice model led to marked decrease in 56 kDa Aß oligomers, reduction of plaques and improvement in cognitive behavior. Our results present a novel prophylactic approach for inhibition of toxic oligomeric Aß species formation in AD through the utilization of a compound that is currently in use in human diet.

Inhibiting α-synuclein oligomerization by stable cell-penetrating ß-synuclein fragments recovers phenotype of Parkinson's disease model flies.

The intracellular oligomerization of α-synuclein is associated with Parkinson's disease and appears to be an important target for disease-modifying treatment. Yet, to date, there is no specific inhibitor for this aggregation process. Using unbiased systematic peptide array analysis, we identified molecular interaction domains within the ß-synuclein polypeptide that specifically binds α-synuclein. Adding such peptide fragments to α-synuclein significantly reduced both amyloid fibrils and soluble oligomer formation in vitro. A retro-inverso analogue of the best peptide inhibitor was designed to develop the identified molecular recognition module into a drug candidate. While this peptide shows indistinguishable activity as compared to the native peptide, it is stable in mouse serum and penetrates α-synuclein over-expressing cells. The interaction interface between the D-amino acid peptide and α-synuclein was mapped by Nuclear Magnetic Resonance spectroscopy. Finally, administering the retro-inverso peptide to a Drosophila model expressing mutant A53T α-synuclein in the nervous system, resulted in a significant recovery of the behavioral abnormalities of the treated flies and in a significant reduction in α-synuclein accumulation in the brains of the flies. The engineered retro-inverso peptide can serve as a lead for developing a novel class of therapeutic agents to treat Parkinson's disease.

Complete phenotypic recovery of an Alzheimer's disease model by a quinone-tryptophan hybrid aggregation inhibitor.

The rational design of amyloid oligomer inhibitors is yet an unmet drug development need. Previous studies have identified the role of tryptophan in amyloid recognition, association and inhibition. Furthermore, tryptophan was ranked as the residue with highest amyloidogenic propensity. Other studies have demonstrated that quinones, specifically anthraquinones, can serve as aggregation inhibitors probably due to the dipole interaction of the quinonic ring with aromatic recognition sites within the amyloidogenic proteins. Here, using in vitro, in vivo and in silico tools we describe the synthesis and functional characterization of a rationally designed inhibitor of the Alzheimer's disease-associated beta-amyloid. This compound, 1,4-naphthoquinon-2-yl-L-tryptophan (NQTrp), combines the recognition capacities of both quinone and tryptophan moieties and completely inhibited Abeta oligomerization and fibrillization, as well as the cytotoxic effect of Abeta oligomers towards cultured neuronal cell line. Furthermore, when fed to transgenic Alzheimer's disease Drosophila model it prolonged their life span and completely abolished their defective locomotion. Analysis of the brains of these flies showed a significant reduction in oligomeric species of Abeta while immuno-staining of the 3(rd) instar larval brains showed a significant reduction in Abeta accumulation. Computational studies, as well as NMR and CD spectroscopy provide mechanistic insight into the activity of the compound which is most likely mediated by clamping of the aromatic recognition interface in the central segment of Abeta. Our results demonstrate that interfering with the aromatic core of amyloidogenic peptides is a promising approach for inhibiting various pathogenic species associated with amyloidogenic diseases. The compound NQTrp can serve as a lead for developing a new class of disease modifying drugs for Alzheimer's disease.

Inhibition of amyloid fibril formation and cytotoxicity by hydroxyindole derivatives.

Gaining insight into the mechanism of amyloid fibril formation, the hallmark of multiple degenerative syndromes of unrelated origin, and exploring novel directions of inhibition are crucial for preventing disease development. Specific interactions between aromatic moieties were suggested to have a key role in the recognition and self-assembly processes leading to the formation of amyloid fibrils by several amyloidogenic polypeptides, including the beta-amyloid polypeptide associated with Alzheimer's disease. Our finding of the high-affinity molecular recognition and intense amyloidogenic potential of tryptophan-containing peptide fragments led to the hypothesis that screening for indole derivatives might lead to the identification of potential inhibitors of amyloid formation. Such inhibitors could mediate specific recognition processes without allowing further growth of the well-ordered amyloid chain. Using fluorescence spectroscopy, atomic force microscopy, and electron microscopy to screen 29 indole derivatives, we identified three potent inhibitors: indole-3-carbinol (I3C), 3-hydroxyindole (3HI), and 4-hydroxyindole (4HI). The latter, a simple low-molecular weight aromatic compound, was the most effective, completely abrogating not only the formation of aggregated structures by Abeta but also the cytotoxic activity of aggregated Abeta toward cultured cells. The results of this study provide further experimental support for the paradigm of amyloid inhibition by heteroaromatic interaction and point to indole derivatives as a simple molecular platform for the development of novel fibrillization inhibitors.