In vitro and in vivo pharmacological characterization of ASP8477: A novel highly selective fatty acid amide hydrolase inhibitor

Endocannabinoid Degradation Enzyme Inhibitors as Potential Antipsychotics: A Medicinal Chemistry Perspective

The endocannabinoid system (ECS) plays a very important role in numerous physiological and pharmacological processes, such as those related to the central nervous system (CNS), including learning, memory, emotional processing, as well pain control, inflammatory and immune response, and as a biomarker in certain psychiatric disorders. Unfortunately, the half-life of the natural ligands responsible for these effects is very short. This perspective describes the potential role of the inhibitors of the enzymes fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MGL), which are mainly responsible for the degradation of endogenous ligands in psychic disorders and related pathologies. The examination was carried out considering both the impact that the classical exogenous ligands such as Δ⁹-tetrahydrocannabinol (THC) and (-)-trans-cannabidiol (CBD) have on the ECS and through an analysis focused on the possibility of predicting the potential toxicity of the inhibitors before they are subjected to clinical studies. In particular, cardiotoxicity (hERG liability), probably the worst early adverse reaction studied during clinical studies focused on acute toxicity, was predicted, and some of the most used and robust metrics available were considered to select which of the analyzed compounds could be repositioned as possible oral antipsychotics.

Fatty Acid Amide Hydrolase: An Integrative Clinical Perspective

Introduction: Fatty acid amide hydrolase (FAAH) is one of the main terminating enzymes of the endocannabinoid system (ECS). Since being discovered in 1996, the modulation of FAAH has been viewed as a compelling alternative strategy to obtain the beneficial effect of the ECS. With a considerable amount of FAAH-related publication over time, the next step would be to comprehend the proximity of this evidence for clinical application. Objective: This review intends to highlight the rationale of FAAH modulation and provide the latest evidence from clinical studies. Methods: Publication searches were conducted to gather information focused on FAAH-related clinical evidence with an extension to the experimental research to understand the biological plausibility. The subtopics were selected to be multidisciplinary to offer more perspective on the current state of the arts. Discussion: Experimental and clinical studies have demonstrated that FAAH was highly expressed not only in the central nervous system but also in the peripheral tissues. As the key regulator of endocannabinoid signaling, it would appear that FAAH plays a role in the modulation of mood and emotional response, reward system, pain perception, energy metabolism and appetite regulation, inflammation, and other biological processes. Genetic variants may be associated with some conditions such as substance/alcohol use disorders, obesity, and eating disorder. The advancement of functional neuroimaging has enabled the evaluation of the neurochemistry of FAAH in brain tissues and this can be incorporated into clinical trials. Intriguingly, the application of FAAH inhibitors in clinical trials seems to provide less striking results in comparison with the animal models, although some potential still can be seen. Conclusion: Modulation of FAAH has an immense potential to be a new therapeutic candidate for several disorders. Further exploration, however, is still needed to ensure who is the best candidate for the treatment strategy.

Cannabinoids and the endocannabinoid system in fibromyalgia: A review of preclinical and clinical research

Characterised by chronic widespread musculoskeletal pain, generalised hyperalgesia, and psychological distress, fibromyalgia (FM) is a significant unmet clinical need. The endogenous cannabinoid system plays an important role in modulating both pain and the stress response. Here, we appraise the evidence, from preclinical and clinical studies, for a role of the endocannabinoid system in FM and the therapeutic potential of targeting the endocannabinoid system. While many animal models have been used to study FM, the reserpine-induced myalgia model has emerged as perhaps the most translatable to the clinical phenotype. Inhibition of fatty acid amide hydrolase (FAAH) has shown promise in preclinical studies, ameliorating pain- and anxiety-related behaviour . Clinically, there is evidence for alterations in the endocannabinoid system in patients with FM, including single nucleotide polymorphisms and increased levels of circulating endocannabinoids and related N-acylethanolamines. Single entity cannabinoids, cannabis, and cannabis-based medicines in patients with FM show promise therapeutically but limitations in methodology and lack of longitudinal studies to assess efficacy and tolerability preclude the current recommendation for their use in patients with FM. Gaps in the literature that warrant further investigation are discussed, particularly the need for further development of animal models with high validity for the multifaceted nature of FM, balanced studies to eliminate sex-bias in preclinical research, and ultimately, better translation between preclinical and clinical research.

Therapeutic Approaches to Nociplastic Pain Based on Findings in the Reserpine-Induced Fibromyalgia-Like Animal Model

Nociplastic pain, the third category of chronic pain, has emerged as a serious medical issue. Due to its significant negative influences on patients and society, high prevalence, and lack of sufficiently effective treatments, more efficacious therapies are required. This review highlights the potential therapeutic approaches identified in studies that used reserpine-induced myalgia (RIM) animal model that exhibits nociplastic pain-associated phenotypes. These studies have revealed that biological processes including the chronic reduction of monoamines, increase of oxidative/nitrosative stresses and inflammatory mediators, upregulation of pronociceptive neurotransmitters and their receptors, increase of trophic factors, enhancement of the apoptotic pathway, sensory nerve sensitization, and activation of immune cells in central and/or peripheral regions, underly the nociplastic pain-associated phenotypes in RIM animal model. Potential therapeutic approaches to nociplastic pain, i.e., 1) functional modification of specific molecules which expression is distinctly altered following monoamine reduction, 2) targeting the molecules which are responsible for other major categories of chronic pain (i.e., chronic inflammatory pain and neuropathic pain), 3) supplementation of nutrition to correct the disrupted nutritional balance, 4) improvement of physical constitution by natural substances, and 5) nonpharmacological interventions, have been identified. Significance Statement Studies in RIM animal model have revealed the pathologies that occur after the chronic reduction of monoamines and identified potential therapeutic approaches to nociplastic pain. Translation of their analgesic efficacy from RIM animal model to patients remains an issue to be addressed. Successful translation would lead to better therapies for nociplastic pain.

Targeting Endocannabinoid Signaling: FAAH and MAG Lipase Inhibitors

Inspired by the medicinal properties of the plant Cannabis sativa and its principal component (-)-trans-Δ⁹-tetrahydrocannabinol (THC), researchers have developed a variety of compounds to modulate the endocannabinoid system in the human brain. Inhibitors of fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), which are the enzymes responsible for the inactivation of the endogenous cannabinoids anandamide and 2-arachidonoylglycerol, respectively, may exert therapeutic effects without inducing the adverse side effects associated with direct cannabinoid CB₁ receptor stimulation by THC. Here we review the FAAH and MAGL inhibitors that have reached clinical trials, discuss potential caveats, and provide an outlook on where the field is headed.

Discovery of heterocyclic carbohydrazide derivatives as novel selective fatty acid amide hydrolase inhibitors: design, synthesis and anti-neuroinflammatory evaluation

Fatty acid amide hydrolase (FAAH) is a promising target for the development of drugs to treat pain, inflammation, and other central nervous system disorders. Herein, a series of novel heterocyclic carbohydrazide derivatives were firstly designed by the classic scaffold-hopping strategy. Then, multi-steps synthesis and human FAAH enzyme inhibiting activity assays were conducted. Among them, compound 26 showedstrong inhibition against human FAAH with IC₅₀ of 2.8 μM. Corresponding docking studies revealed that the acyl hydrazide group of compound 26 well-occupied the acyl-chain binding pocket. It also exhibited high selectivity towards FAAH when comparing with CES2 and MAGL. Additionally, compound 26 effectively suppressed the LPS-induced neuroinflammation of microglial cells (BV2) via the reduction of interleukin-1β and tumor necrosis factor-α. Our results provided significative lead compounds for the further discovery of novel selective and safe FAAH inhibitors with potent anti-neuroinflammation activity.

Advances in the discovery of fatty acid amide hydrolase inhibitors: what does the future hold?

INTRODUCTION

Fatty acid amide hydrolase (FAAH) is a membrane-bound enzyme, that inactivates endogenous signaling lipids of the fatty acid amide family, including the endocannabinoid anandamide (N-arachidonoylethanolamine, AEA). The latter compound has been shown to regulate a number of important pathophysiological conditions in humans, like feeding, obesity, immune response, reproductive events, motor coordination, and neurological disorders. Hence, direct manipulation of the endocannabinoid tone is thought to have therapeutic potential. A new opportunity to develop effective drugs may arise from multi-target directed ligand (MTDL) strategies, which brings the concept that a single compound can recognize different targets involved in the cascade of pathophysiological events.

AREAS COVERED

This review reports the latest advances in the development of new single targeted and dual-targeted FAAH inhibitors over the past 5 years.

EXPERT OPINION

In recent years, several FAAH inhibitors have been synthesized and investigated, yet to date none of them has reached the market as a systemic drug. Due to the diligence of inherent redundancy and robustness in many biological networks and pathways, multitarget inhibitors present a new prospect in the pharmaceutical industry for treatment of complex diseases.

Pharmacological characterization of a novel, potent, selective, and orally active fatty acid amide hydrolase inhibitor, PKM-833 [(R)-N-(pyridazin-3-yl)-4-(7-(trifluoromethyl)chroman-4-yl)piperazine-1-carboxamide] in rats: Potential for the treatment of inflammatory pain

Recently, we identified a novel fatty acid amide hydrolase (FAAH) inhibitor, PKM-833 [(R)-N-(pyridazin-3-yl)-4-(7-(trifluoromethyl)chroman-4-yl)piperazine-1-carboxamide]. The aim of the present study is to characterize the pharmacological profile of PKM-833 in vitro and in vivo. PKM-833 showed potent inhibitory activities against human and rat FAAH with IC50 values of 8.8 and 10 nmol/L, respectively, 200-fold more selectivity against other 137 molecular targets, and irreversible mode of action. In pharmacokinetic and pharmacodynamic studies, PKM-833 showed excellent brain penetration and good oral bioavailability, and elevated anandamide (AEA) concentrations in the rat brain. These data indicate that PKM-833 is a potent, selective, orally active, and brain-penetrable FAAH inhibitor. In behavioral studies using rat models, PKM-833 significantly attenuated formalin-induced pain responses (3 mg/kg) and improved mechanical allodynia in complete freund's adjuvant (CFA)-induced inflammatory pain (0.3-3 mg/kg). On the other hand, PKM-833 did not show the analgesic effects against mechanical allodynia in chronic constriction injury (CCI)-induced neuropathic pain up to 30 mg/kg. Regarding side effects, PKM-833 had no significant effects on catalepsy and motor coordination up to 30 mg/kg. These results indicate that PKM-833 is a useful pharmacological agent that can be used to investigate the role of FAAH and may have therapeutic potential for the treatment of inflammatory pain without undesirable side effects.

Dietary Polyphenols: A Multifactorial Strategy to Target Alzheimer's Disease

Ageing is an inevitable fundamental process for people and is their greatest risk factor for neurodegenerative disease. The ageing processes bring changes in cells that can drive the organisms to experience loss of nutrient sensing, disrupted cellular functions, increased oxidative stress, loss of cellular homeostasis, genomic instability, accumulation of misfolded protein, impaired cellular defenses and telomere shortening. Perturbation of these vital cellular processes in neuronal cells can lead to life threatening neurological disorders like Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, Lewy body dementia, etc. Alzheimer's Disease is the most frequent cause of deaths in the elderly population. Various therapeutic molecules have been designed to overcome the social, economic and health care burden caused by Alzheimer's Disease. Almost all the chemical compounds in clinical practice have been found to treat symptoms only limiting them to palliative care. The reason behind such imperfect drugs may result from the inefficiencies of the current drugs to target the cause of the disease. Here, we review the potential role of antioxidant polyphenolic compounds that could possibly be the most effective preventative strategy against Alzheimer's Disease.

A Cocktail Interaction Study Evaluating the Drug-Drug Interaction Potential of the Perpetrator Drug ASP8477 at Multiple Ascending Dose Levels

ASP8477 (molecular weight 325.36 g/mol) is a fatty acid amide hydrolase inhibitor intended for the treatment of neuropathic pain. Results from in vitro studies indicated that ASP8477 is a direct inhibitor of cytochrome P450 (CYP) 2C8, 2C9, 2C19, 2D6, and 3A4 enzymes at expected efficacious concentrations, with the strongest effect on CYP2C19; a phase 1 study confirmed ASP8477 to be a CYP2C19 inhibitor. To further evaluate the interaction potential of ASP8477, a cocktail interaction study was performed using the probe substrates of the validated Inje cocktail containing losartan (CYP2C9), omeprazole (CYP2C19), dextromethorphan (CYP2D6), and midazolam (CYP3A4). Because ASP8477 shows nonlinear pharmacokinetics, 3 doses (20, 60, and 100 mg) were evaluated. This study revealed changes in exposure (area under the concentration‐time curve) of the probe substrates after treatment with 20, 60, and 100 mg ASP8477, respectively, compared with substrates alone with geometric mean ratios of: midazolam, 119%, 151%, and 158%; losartan, 107%, 144%, and 190%; omeprazole, 213%, 456%, and 610%; and dextromethorphan, 138%, 340%, and 555% (with increasing doses, respectively). Overall, ASP8477 was a weak inhibitor for CYP3A4 and CYP2C9, a moderate to strong inhibitor for CYP2C19, and a weak to strong inhibitor for CYP2D6, with doses from 20 to 100 mg. This study confirmed that the Inje cocktail approach was able to detect relevant drug‐drug interactions impacting further development of ASP8477 and future therapeutic use. With the approach used here, the inhibiting effect of a perpetrator drug on different CYP enzymes can be evaluated, and at different doses, thereby supporting dose recommendations for potential interactions.

Comprehensive review of mechanisms of pathogenesis involved in Alzheimer's disease and potential therapeutic strategies

AD is a progressive neurodegenerative disorder and a leading cause of dementia in an aging population worldwide. The enormous challenge which AD possesses to global healthcare makes it as urgent as ever for the researchers to develop innovative treatment strategies to fight this disease. An in-depth analysis of the extensive available data associated with the AD is needed for a more comprehensive understanding of underlying molecular mechanisms and pathophysiological pathways associated with the onset and progression of the AD. The currently understood pathological and biochemical manifestations include cholinergic, Aβ, tau, excitotoxicity, oxidative stress, ApoE, CREB signaling pathways, insulin resistance, etc. However, these hypotheses have been criticized with several conflicting reports for their involvement in the disease progression. Several issues need to be addressed such as benefits to cost ratio with cholinesterase therapy, the dilemma of AChE selectivity over BChE, BBB permeability of peptidic BACE-1 inhibitors, hurdles related to the implementation of vaccination and immunization therapy, and clinical failure of candidates related to newly available targets. The present review provides an insight to the different molecular mechanisms involved in the development and progression of the AD and potential therapeutic strategies, enlightening perceptions into structural information of conventional and novel targets along with the successful applications of computational approaches for the design of target-specific inhibitors.