A phase 2, double-blind, placebo-controlled study of NSI-189 phosphate, a neurogenic compound, among outpatients with major depressive disorder

Precision Medicine in Angelman Syndrome

Angelman syndrome (AS) is a rare neurogenetic disorder caused by a loss of function of UBE3A on the maternal allele. Clinical features include severe neurodevelopmental delay, epilepsy, sleep disturbances, and behavioral disorders. Therapy currently evolves from conventional symptomatic, supportive, and antiseizure treatments toward alteration of mRNA expression, which is subject of several ongoing clinical trials.This article will provide an overview of clinical research and therapeutic approaches on AS.

Comprehensive analysis of genetic risk loci uncovers novel candidate genes and pathways in the comorbidity between depression and Alzheimer's disease

There is growing evidence of a shared pathogenesis between Alzheimer's disease and depression. Therefore, we aimed to further investigate their shared disease mechanisms. We made use of publicly available brain-specific eQTL data and gene co-expression networks of previously reported genetic loci associated with these highly comorbid disorders. No direct genetic overlap was observed between Alzheimer's disease and depression in our dataset, but we did detect six shared brain-specific eQTL genes: SRA1, MICA, PCDHA7, PCDHA8, PCDHA10 and PCDHA13. Several pathways were identified as shared between Alzheimer's disease and depression by conducting clustering pathway analysis on hippocampal co-expressed genes; synaptic signaling and organization, myelination, development, and the immune system. This study highlights trans-synaptic signaling and synaptoimmunology in the hippocampus as main shared pathomechanisms of Alzheimer's disease and depression.

Ketamine: Mechanisms and Relevance to Treatment of Depression

Major depressive disorder (MDD) is a leading cause of suicide in the world. Monoamine-based antidepressant drugs are a primary line of treatment for this mental disorder, although the delayed response and incomplete efficacy in some patients highlight the need for improved therapeutic approaches. Over the past two decades, ketamine has shown rapid onset with sustained (up to several days) antidepressant effects in patients whose MDD has not responded to conventional antidepressant drugs. Recent preclinical studies have started to elucidate the underlying mechanisms of ketamine's antidepressant properties. Herein, we describe and compare recent clinical and preclinical findings to provide a broad perspective of the relevant mechanisms for the antidepressant action of ketamine.

Discovery of Novel Diphenyl Acrylonitrile Derivatives That Promote Adult Rats' Hippocampal Neurogenesis

We previously discovered WS-6 as a new antidepressant in correlation to its function of stimulating neurogenesis. Herein, several different scaffolds (stilbene, 1,3-diphenyl 1-propene, 1,3-diphenyl 2-propene, 1,2-diphenyl acrylo-1-nitrile, 1,2-diphenyl acrylo-2-nitrile, 1,3-diphenyl trimethylamine), further varied through substitutions of twelve amide substituents plus the addition of a methylene unit and an inverted amide, were examined to elucidate the SARs for promoting adult rat neurogenesis. Most of the compounds could stimulate proliferation of progenitors, but just a few chemicals possessing a specific structural profile, exemplified by diphenyl acrylonitrile 29b, 32a, and 32b, showed better activity than the clinical drug NSI-189 in promoting newborn cells differentiation into mature neurons. The most potent diphenyl acrylonitrile 32b had an excellent brain AUC to plasma AUC ratio (B/P = 1.6), suggesting its potential for further development as a new lead.

How should we design future mechanistic and/or efficacy clinical trials?

The emergence of new molecular targets, together with the development of new approaches to neuropsychiatric diseases, involving psychedelics as well as gene and cell therapies, are creating the need to improve the efficiency of mechanistic and/or efficacy clinical trials. This review article will discuss a number of issues that have hampered our ability to detect therapeutic signals, from excessive placebo/sham response rates to the imprecision of diagnostic and outcome assessments. In addition to reviewing the limitations of current efficacy and mechanistic neuropsychiatric clinical trials, this review presents some of the methodological approaches that may improve the overall performance of our neuropsychiatric trials, including the adoption of novel study designs such as the sequential parallel comparison design and independent confirmation of the appropriateness of subjects' enrollment. In addition, this review will discuss several designs that make mechanistic clinical trials more precise.

Acute and long-term effects of adolescence stress exposure on rodent adult hippocampal neurogenesis, cognition, and behaviour

Adolescence represents a critical period for brain and behavioural health and characterised by the onset of mood, psychotic and anxiety disorders. In rodents, neurogenesis is very active during adolescence, when is particularly vulnerable to stress. Whether stress-related neurogenesis changes influence adolescence onset of psychiatric symptoms remains largely unknown. A systematic review was conducted on studies investigating changes in hippocampal neurogenesis and neuroplasticity, hippocampal-dependent cognitive functions, and behaviour, occurring after adolescence stress exposure in mice both acutely (at post-natal days 21-65) and in adulthood. A total of 37 studies were identified in the literature. Seven studies showed reduced hippocampal cell proliferation, and out of those two reported increased depressive-like behaviours, in adolescent rodents exposed to stress. Three studies reported a reduction in the number of new-born neurons, which however were not associated with changes in cognition or behaviour. Sixteen studies showed acutely reduced hippocampal neuroplasticity, including pre- and post-synaptic plasticity markers, dendritic spine length and density, and long-term potentiation after stress exposure. Cognitive impairments and depressive-like behaviours were reported by 11 of the 16 studies. Among studies who looked at adolescence stress exposure effects into adulthood, seven showed that the negative effects of stress observed during adolescence on either cell proliferation or hippocampal neuroplasticity, cognitive deficits and depressive-like behaviour, had variable impact in adulthood. Treating adolescent mice with antidepressants, glutamate receptor inhibitors, glucocorticoid antagonists, or healthy diet enriched in omega-3 fatty acids and vitamin A, prevented or reversed those detrimental changes. Future research should investigate the translational value of these preclinical findings. Developing novel tools for measuring hippocampal neurogenesis in live humans, would allow assessing neurogenic changes following stress exposure, investigating relationships with psychiatric symptom onset, and identifying effects of therapeutic interventions.

Targeting hippocampal neurogenesis to protect astronauts' cognition and mood from decline due to space radiation effects

Neurogenesis is an essential, lifelong process during which neural stem cells generate new neurons within the hippocampus, a center for learning, memory, and mood control. Neural stem cells are vulnerable to environmental insults spanning from chronic stress to radiation. These insults reduce their numbers and diminish neurogenesis, leading to memory decline, anxiety, and depression. Preserving neural stem cells could thus help prevent these neurogenesis-associated pathologies, an outcome particularly important for long-term space missions where environmental exposure to radiation is significantly higher than on Earth. Multiple developments, from mechanistic discoveries of radiation injury on hippocampal neurogenesis to new platforms for the development of selective, specific, effective, and safe small molecules as neurogenesis-protective agents hold great promise to minimize radiation damage on neurogenesis. In this review, we summarize the effects of space-like radiation on hippocampal neurogenesis. We then focus on current advances in drug discovery and development and discuss the nuclear receptor TLX/NR2E1 (oleic acid receptor) as an example of a neurogenic target that might rescue neurogenesis following radiation.

A Potential Strategy for Treatment of Neurodegenerative Disorders by Regulation of Adult Hippocampal Neurogenesis in Human Brain

Abstract:

Adult hippocampal neurogenesis is a multistage mechanism that continues throughout the lifespan of human and non-human mammals. These adult-born neurons in the central nervous system (CNS) play a significant role in various hippocampus-dependent processes, including learning, mood regulation, pattern recognition, etc. Reduction of adult hippocampal neurogenesis, caused by multiple factors such as neurological disorders and aging, would impair neuronal proliferation and differentiation and result in memory loss. Accumulating studies have indicated that functional neuron impairment could be restored by promoting adult hippocampal neurogenesis. In this review, we summarized the small molecules that could efficiently promote the process of adult neurogenesis, particularly the agents that have the capacity of crossing the blood-brain barrier (BBB), and showed in vivo efficacy in mammalian brains. This may pave the way for the rational design of drugs to treat humnan neurodegenerative disorders in the future.

Recent Advances in Small Molecule Stimulation of Regeneration and Repair

Therapeutic approaches to stimulate regeneration and repair have the potential to transform healthcare and improve outcomes for patients suffering from numerous chronic degenerative diseases. To date most approaches have involved the transplantation of therapeutic cells, and while there have been a small number of clinical approvals, major hurdles exist to the routine adoption of such therapies. In recent years humans and other mammals have been shown to possess a regenerative capacity across multiple tissues and organs, and an innate regenerative and repair response has been shown to be activated in these organs in response to injury. These realisations have inspired a transformative approach in regenerative medicine: the development of new agents to directly target these innate regeneration and repair pathways. In this article we will review the current state of the art in the discovery of small molecule modulators of regeneration and their translation towards therapeutic agents, focussing specifically on the areas of neuroregeneration and cardiac regeneration.

Enhancement of Mitochondrial Function by the Neurogenic Molecule NSI-189 Accompanies Reversal of Peripheral Neuropathy and Memory Impairment in a Rat Model of Type 2 Diabetes

AIMS

Mitochondrial dysfunction contributes to many forms of peripheral and central nervous system degeneration. Therapies that protect mitochondrial number and function have the potential to impact the progression of conditions such as diabetic neuropathy. We therefore assessed indices of mitochondrial function in dorsal root ganglia (DRG) and brain cortex of the Zucker diabetic fatty (ZDF) rat model of type 2 diabetes and tested the therapeutic impact of a neurogenic compound, NSI-189, on both mitochondrial function and indices of peripheral and central neurological dysfunction.

MATERIALS AND METHODS

ZDF rats were maintained for 16 weeks of untreated diabetes before the start of oral treatment with NSI-189 for an additional 16 weeks. Nerve conduction velocity, sensitivity to tactile and thermal stimuli, and behavioral assays of cognitive function were assessed monthly. AMP-activated protein kinase (AMPK) phosphorylation, mitochondrial protein levels, and respiratory complex activities were assessed in the DRG and brain cortex after 16 weeks of treatment with NSI-189.

RESULTS

Treatment with NSI-189 selectively elevated the expression of protein subunits of complexes III and V and activities of respiratory complexes I and IV in the brain cortex, and this was accompanied by amelioration of impaired memory function and plasticity. In the sensory ganglia of ZDF rats, loss of AMPK activity was ameliorated by NSI-189, and this was accompanied by reversal of multiple indices of peripheral neuropathy.

CONCLUSIONS

Efficacy of NSI-189 against dysfunction of the CNS and PNS function in type 2 diabetic rats was accompanied by improvement of mitochondrial function. NSI-189 exhibited actions at different levels of mitochondrial regulation in central and peripheral tissues.

Therapies in preclinical and clinical development for Angelman syndrome

Introduction: Angelman syndrome is a rare genetic neurodevelopmental disorder, caused by deficiency or abnormal function of the maternal ubiquitin protein-ligase E3A, known as UBE3A, in the central nervous system. There is no disease-modifying treatment available, but the therapeutic pipeline of Angelman syndrome includes at least 15 different approaches at preclinical or clinical development. In the coming years, several clinical trials will be enrolling patients, which prompted this comprehensive review.Areas covered: We summarize and critically review the different therapeutic approaches. Some approaches attempt to restore the missing or nonfunctional UBE3A protein in the neurons via gene replacement or enzyme replacement therapies. Other therapies aim to induce expression of the normal paternal copy of the UBE3A gene by targeting a long non-coding RNA, the UBE3A-ATS, which interferes with its own expression. Another therapeutic category includes compounds that target molecular pathways and effector proteins known to be involved in Angelman syndrome pathophysiology.Expert opinion: We believe that by 2022-2023, more than five disease-modifying treatments will be simultaneously at clinical testing. However, the are several challenges with regards to safety and efficacy, which need to be addressed. Additionally, there is still a significant unmet need for clinical trial readiness.

Cognition in the Chronic Pain Experience: Preclinical Insights

Acutely, pain is protective. It promotes escape from, and future avoidance of, noxious stimuli through strong and often lifetime associative memories. However, with persistent acute pain or when pain becomes chronic, these memories can promote negative emotions and poor decisions often associated with deleterious behaviors. In this review, we discuss how preclinical studies can provide insights into the relationship between cognition and chronic pain. We also discuss the concept of pain as a cognitive disorder and new strategies for treating chronic pain that emphasize inhibiting the formation of pain memories or promoting 'forgetting' of established pain memories.

Do side effects of antidepressants impact efficacy estimates based on the Hamilton Depression Rating Scale? A pooled patient-level analysis

The Hamilton Depression Rating Scale (HDRS-17) measures symptoms that may overlap with common antidepressant side effects (e.g., sexual dysfunction), thus making it possible that side effects of antidepressant treatment are erroneously rated as symptoms of depression, and vice versa. This study uses patient-level data from previously conducted antidepressant treatment trials to assess whether side effect ratings co-vary with HDRS-17 ratings. Data from all HDRS-17-rated, industry-sponsored pre- and post-marketing trials (n = 4647) comparing the serotonin and noradrenaline reuptake inhibitor, duloxetine, to placebo and/or to a selective serotonin reuptake inhibitor were pooled; three studies, which utilised sub-therapeutic doses, did not have symptom-level ratings available and could not be included. Severity was assessed for side effects related to sleep, somatic anxiety, gastrointestinal function, and sexual dysfunction. Analysis of covariance was used to assess the relation between these side effects and ratings of relevant HDRS-17-derived outcome parameters. Side effects related to sleep, somatic anxiety and sexual dysfunction significantly and exclusively associated with higher scores on HDRS-17 items measuring the corresponding domains. Side effects related to gastrointestinal function associated with higher HDRS-17 item scores on all assessed domains. Treatment outcome was significantly related to side effect severity when assessed using HDRS-17-sum (beta 0.32 (0.074), p < 0.001), but not when the HDRS-6-sum-score (beta 0.035 (0.043), p = 0.415) or the depressed mood item (beta 0.007 (0.012), p = .527) were used as effect parameters. That some HDRS-17 items co-vary with common antidepressant side effects suggests some of these adverse events are counted twice, potentially leading to an underestimation of antidepressant efficacy.

Piperazine, a Key Substructure for Antidepressants: Its Role in Developments and Structure-Activity Relationships

Depression is the single largest contributor to global disability with a huge economic and social burden on the world. There are a number of antidepressant drugs on the market, but treatment-resistant depression and relapse of depression in a large number of patients have increased problems for clinicians. One peculiarity observed in most of the marketed antidepressants is the presence of a piperazine substructure. Although piperazine is also used in the optimization of other pharmacological agents, it is almost extensively used for the development of novel antidepressants. One common understanding is that this is due to its favorable CNS pharmacokinetic profile; however, in the case of antidepressants, piperazine plays a much bigger role and is involved in specific binding conformations of these agents. Therefore, in this review, a critical analysis of the significance of the piperazine moiety in the development of antidepressants has been performed. An overview of current developments in the designing and synthesis of piperazine-based antidepressants (2015 onwards) along with SAR studies is also provided. The various piperazine-based therapeutic agents in early- or late-phase human testing for depression are also discussed. The preclinical compounds discussed in this review will help researchers understand how piperazine actually influences the design and development of novel antidepressant compounds. The SAR studies discussed will provide crucial clues about the structural features and optimizations required to enhance the efficacy and potency of piperazine-based antidepressants.

Amelioration of Both Central and Peripheral Neuropathy in Mouse Models of Type 1 and Type 2 Diabetes by the Neurogenic Molecule NSI-189

While peripheral neuropathy is the most common complication of long-term diabetes, cognitive deficits associated with encephalopathy and myelopathy also occur. Diabetes is a risk factor for Alzheimer disease (AD) and increases the risk of progression from mild cognitive impairment to AD. The only current recommendation for preventing or slowing the progression of peripheral neuropathy is to maintain close glycemic control, while there is no recommendation for central nervous system disorders. NSI-189 is a new chemical entity that when orally administered promotes neurogenesis in the adult hippocampus, increases hippocampal volume, enhances synaptic plasticity, and reduces cognitive dysfunction. To establish the potential for impact on peripheral neuropathy, we first showed that NSI-189 enhances neurite outgrowth and mitochondrial functions in cultured adult rat primary sensory neurons. Oral delivery of NSI-189 to murine models of type 1 (female) and type 2 (male) diabetes prevented multiple functional and structural indices of small and large fiber peripheral neuropathy, increased hippocampal neurogenesis, synaptic markers and volume, and protected long-term memory. NSI-189 also halted progression of established peripheral and central neuropathy. NSI-189, which is currently in clinical trials for treatment of major depressive disorder, offers the opportunity for the development of a single therapeutic agent against multiple indices of central and peripheral neuropathy.