5-HT2A Receptor Inverse Agonist Research Articles

Metabolism, Disposition, Excretion, and Potential Transporter Inhibition of 7-16, an Improving 5-HT2A Receptor Antagonist and Inverse Agonist for Parkinson's Disease.

Compound 7-16 was designed and synthesized in our previous study and was identified as a more potential selective 5-HT2A receptor antagonist and inverse agonist for treating Parkinson's disease psychosis (PDP). Then, the metabolism, disposition, and excretion properties of 7-16 and its potential inhibition on transporters were investigated in this study to highlight advancements in the understanding of its therapeutic mechanisms. The results indicate that a total of 10 metabolites of 7-16/[14C]7-16 were identified and determined in five species of liver microsomes and in rats using UPLC-Q Exactive high-resolution mass spectrometry combined with radioanalysis. Metabolites formed in human liver microsomes could be covered by animal species. 7-16 is mainly metabolized through mono-oxidation (M470-2) and N-demethylation (M440), and the CYP3A4 isozyme was responsible for both metabolic reactions. Based on the excretion data in bile and urine, the absorption rate of 7-16 was at least 74.7%. 7-16 had weak inhibition on P-glycoprotein and no effect on the transport activity of OATP1B1, OATP1B3, OAT1, OAT3, and OCT2 transporters. The comprehensive pharmacokinetic properties indicate that 7-16 deserves further development as a new treatment drug for PDP.

Nelotanserin, a selective 5-HT2A receptor inverse agonist, attenuates aspects of nicotine withdrawal but not reward in mice

Nicotine smoking contributes to many preventable disabilities, diseases and deaths. Targeting nicotine reward and withdrawal is a basis for the majority of smoking cessation pharmacotherapies. Due to the emergence of interest in 5-HT2A receptor modulators for numerous psychiatric disorders, we investigated the effect of nelotanserin, a 5-HT2A receptor inverse agonist, on nicotine reward and withdrawal in ICR mice. In nicotine-dependent mice, nelotanserin dose-dependently reduced somatic signs of nicotine withdrawal and thermal hyperalgesia as measured in the hot plate test. However, nelotanserin had no effect on anxiety-like behavior and failed to reduce nicotine reward as measured in the conditioned place preference test. Our results suggest that inverse agonism of the 5-HT2A receptor may be a feasible novel mechanism for smoking cessation by reducing both physical withdrawal and thermal hyperalgesia associated with nicotine abstinence but may require complementary pharmacotherapies targeting affective and reward-associated decrements to improve cessation outcomes.

Pimavanserin treatment increases plasma brain-derived neurotrophic factor levels in rats.

Pimavanserin, a serotonin 5HT-2A receptor inverse agonist is the first-line, FDA-approved treatment of hallucinations and delusions associated with Parkinson's Disease psychosis (PDP), which occurs in up to 50% of PD patients. The neurobiological mechanism underlying the therapeutic effectiveness of Pimavanserin in PDP remains unknown. Several earlier studies have shown that treatment with 5HT-2A antagonists and other drugs acting on the serotonergic system such as SSRIs increase Brain derived neurotrophic factor (BDNF) levels in rodents. BDNF is synthesized as the precursor proBDNF, that undergoes cleavage intra or extracellularly to produce a mature BDNF (mBDNF) protein. mBDNF is believed to play a key role in neuroplasticity and neurogenesis. The present study tested the hypothesis that treatment with Pimavanserin is associated with higher and sustained elevations of mBDNF. Adult Sprague-Dawley male rats were treated with Pimavanserin, Fluoxetine or vehicle for 4 weeks (chronic) or 2 h (acute). BDNF levels were determined by enzyme-linked Immunosorbent assay (ELISA). We found significant increases in plasma mBDNF levels in rats following chronic Pimavanserin treatment, but not in Fluoxetine-treated rats. No significant changes in mBDNF levels were found in the prefrontal cortex or hippocampus following Pimavanserin or Fluoxetine treatment. These findings suggest that increase in mBDNF levels could be a contributing mechanism for the neuroprotective potential of Pimavanserin.

Microbial Transformation of Pimavanserin by Cunninghamella blakesleeana AS 3.970

Pimavanserin is an approved selective 5-HT2A receptor inverse agonist for treating Parkinson’s disease psychosis. However, few studies on its metabolism in vitro have been investigated. In this research, eight strains of fungi are used to study the pimavanserin metabolism profiles in vitro and six of them demonstrated positive transformation results. Factors influencing the transformation rate, like substrate concentration, culture time, initial media pH value, culture temperature, and shaking speed, were evaluated and optimized. Cunninghamella blakesleeana AS3.970 provided the best transformation rate of 30.31%, and 10 unreported metabolites were screened by LC-MS/MS. Among these metabolites, M1 is the major one and identified as 1-(4-fluorobenzyl)-3-(4-(2-hydroxy-2-methylpropoxy)benzyl)-1-(1-methylpiperidin-4-yl)urea, which is a hydroxylation product of the pimavanserin. A preliminary molecular docking simulation was performed, which indicated that M1 exhibits similar binding properties with pimavanserin and may become a potential candidate for Parkinson’s disease treatment.

Design, Synthesis, Molecular Docking, and Biological Evaluation of Novel Pimavanserin-Based Analogues as Potential Serotonin 5-HT2A Receptor Inverse Agonists.

There is concern for important adverse effects with use of second-generation antipsychotics in Parkinson's disease psychosis (PDP) and dementia-related psychosis. Pimavanserin is the only antipsychotic drug authorized for PDP and represents an inverse agonist of 5-HT2A receptors (5-HT2AR) lacking affinity for dopamine receptors. Therefore, the development of serotonin 5-HT2AR inverse agonists without dopaminergic activity represents a challenge for different neuropsychiatric disorders. Using ligand-based drug design, we discovered a novel structure of pimavanserin analogues (2, 3, and 4). In vitro competition receptor binding and functional G protein coupling assays demonstrated that compounds 2, 3, and 4 showed higher potency than pimavanserin as 5-HT2AR inverse agonists in the human brain cortex and recombinant cells. To assess the effect of molecular substituents for selectivity and inverse agonism at 5-HT2ARs, molecular docking and in silico predicted physicochemical parameters were performed. Docking studies were in agreement with in vitro screenings and the results resembled pimavanserin.

Non-clinical pharmacology and toxicology studies of LPM6690061, a novel 5-hydroxytryptamine (5-HT)2A receptor inverse agonist.

LPM6690061 is a novel compound with 5-HT2A receptor antagonist and inverse agonist activities. To support the clinical trial and marketing application of LPM6690061, a series of pharmacology and toxicology studies have been conducted. In vitro and in vivo pharmacology studies showed that LPM6690061 had high inverse agonism and antagonism activities against human 5-HT2A receptors, and demonstrated significant antipsychotic-like effects in two rat models: the DOI-induced head-twitch model and the MK-801-induced hyperactivity model, which was more effective than the control drug pimavanserin. LPM6690061 did not have detectable side effects on the neurobehavioral activities and respiratory function in rats, or on the ECG or blood pressure in dogs at the doses of 2 and 6mg/kg. The half maximal inhibitory concentration (IC50) of LPM6690061 for inhibiting hERG current was 1.02μM. Three in vivo toxicology studies were conducted. In the single dose toxicity study in rats and dogs, the maximum tolerated dose of LPM6690061 was 100mg/kg. In the 4-week repeat dose toxicity study in rats, the main detectable toxic reactions of LPM6690061 included moderate artery wall hypertrophy, minimal to mild mixed cell inflammation and increased macrophages in the lung, which generally recovered after a 4-week drug withdrawal period. In the 4-week repeat dose toxicity study in dogs, no detectable toxicity was observed. The doses of no-observed-adverse-effect-level (NOAEL) in rats and dogs were 10mg/kg and 20mg/kg, respectively. In conclusion, both in vitro and in vivo pharmacological and toxicological studies showed that LPM6690061 was a safe and efficacious 5-HT2A receptor antagonist/inverse agonist which supports the clinical development as a novel antipsychotic drug.

Pimavanserin and trazodone combination in behavioral disorders in severe dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is characterized by neurocognitive disorders associated with core clinical features including hallucinations. There is currently no cure but a combination of symptomatic treatments: clozapine is commonly used in DLB-related psychosis. Pimavanserin is a serotonin5HT-2A receptor inverse agonist that has recently been shown to reduce psychosis related to dementia. Trazodone is a serotonin reuptake inhibitor and a 5-HT2 receptor antagonist: it is effective in the treatment of the frontal syndrome and is commonly used in frontotemporal degeneration. We describe three patients with DLB, hospitalized in the cognitive-behavioral unit of the University Hospitals of Strasbourg, who presented with major visual hallucinations, delusion, and an orbitofrontal syndrome including disinhibition, agitation, and irritability. The 3 patients were intolerant of low-dose Clozapine (neutropenia for one, somnolence for the other and Pisa syndrome and falls for the last one). We evaluated the Neuropsychiatric Inventory (NPI) before and after the introduction of both treatments. Given their psychotic and frontal symptoms, we used Pimavanserin and Trazodone simultaneously. After 4 to 6 weeks of treatment, a marked improvement was observed in all 3 patients, with a decrease of the NPI scores from a mean of 88 to 38. To our knowledge, there is no previously described combination of these two treatments in DLB. A clinical trial combining these two molecules against pervasive behavioral disorders in DLB would be interesting in view of these preliminary results.

Improving the treatment of Parkinson's disease: Structure-based development of novel 5-HT2A receptor antagonists/inverse agonists

Pimavanserin is a selective 5-HT2A receptor antagonist and inverse agonist approved by the FDA in 2016, which is used to treat patients with Parkinson's disease psychosis (PDP). But pimavanserin has potential risk with increasing mortality in elderly patients and also increasing the risk of QT interval prolongation in patients. Therefore, searching for new drugs with high efficacy and low toxicity is urgently needed. Based on the docking study of pimavanserin, a series of novel pimavanserin derivatives (7–1∼7–37) were designed and synthesized. The biological activities were evaluated by cell assays and compound 7–16 exhibited 50-fold higher 5-HT2A receptor antagonist activity (IC50 = 0.54 vs 27.3 nM) and 23-fold higher inverse agonist activity (IC50 = 2.1 vs 50 nM) than pimavanserin. Moreover, 7–16 showed increased potency window between the 5-HT2A and hERG activities than pimavanserin. Furthermore, compound 7–16 demonstrated excellent in vitro and in vivo pharmacokinetics, 4-fold more improvement in functional activity in vivo, and good safety profile. Therefore, compound 7–16 represents a potentially promising candidate as a novel anti-PDP agent that warrants further investigation.

Human Cortical Serotonin 2A Receptor Occupancy by Psilocybin Measured Using [11C]MDL 100,907 Dynamic PET and a Resting-State fMRI-Based Brain Parcellation.

Psilocybin (a serotonin 2A, or 5-HT2A, receptor agonist) has shown preliminary efficacy as a treatment for mood and substance use disorders. The current report utilized positron emission tomography (PET) with the selective 5-HT2A receptor inverse agonist radioligand [11C]MDL 100,907 (a.k.a. M100,907) and cortical regions of interest (ROIs) derived from resting-state functional connectivity-based brain parcellations in 4 healthy volunteers (2 females) to determine regional occupancy/target engagement of 5-HT2A receptors after oral administration of a psychoactive dose of psilocybin (10 mg/70 kg). Average 5-HT2A receptor occupancy across all ROIs was 39.5% (± 10.9% SD). Three of the ROIs with greatest occupancy (between 63.12 and 74.72% occupancy) were within the default mode network (subgenual anterior cingulate and bilateral angular gyri). However, marked individual variability in regional occupancy was observed across individuals. These data support further investigation of the relationship between individual differences in the acute and enduring effects of psilocybin and the degree of regional 5-HT2A receptor occupancy.

Pharmacodynamics study of a new 5-HT2A receptor inverse agonist PCC03039

The purpose of this paper is to evaluate the pharmacodynamics of a new 5-HT2A receptor inverse agonist PCC03039 and provide data support for its druggability and clinical trial application. In the in vitro efficacy studies, the affinities of PCC03039 for 5-HT2A, 5-HT2B, and 5-HT2C receptors and the inverse agonistic and antagonistic activities of 5-HT2A receptors were detected; in the in vivo efficacy studies, the pharmacodynamic effects of PCC03039 on DOI-induced rat head-twitch model and MK-801-induced rat hyperlocomotion model were observed. The results of the studies showed that the affinities of PCC03039 for the 5-HT2 receptors were comparable to those of the marketed drug pimavanserin, however, the inverse agonistic and antagonistic activities of PCC03039 for the 5-HT2A receptor were significantly improved, with IC50 values of 2.11 nM and 1.33 nM, which were 20-fold and 21-fold higher than that of pimavanserin, respectively. PCC03039 could dose-dependently inhibit DOI-induced head-twitch and MK-801-induced hyperlocomotion in SD rats, and the pharmacodynamic effect was significantly better than pimavanserin at the equimolar dose. The above results show that PCC03039 has better pharmacodynamic activity in vitro and in vivo than pimavanserin, and has good druggability from the perspective of pharmacodynamics.

P.0228 Evaluation of serotonin 5HT2A receptor functional selectivity and inverse agonist properties of different antipsychotic drugs in human post-mortem brain cortex

P.0228 Evaluation of serotonin 5HT2A receptor functional selectivity and inverse agonist properties of different antipsychotic drugs in human post-mortem brain cortex

Pimavanserin, a 5-hydroxytryptamine 2A receptor inverse agonist, reverses prepulse inhibition deficits in the nucleus accumbens and ventral hippocampus

Prepulse inhibition (PPI) is disrupted in many neuropsychiatric diseases. Although the inverse agonist of the 5-hydroxytryptamine 2A (5-HT2A) receptors, pimavanserin, alleviates PPI deficits in rodents, the precise mechanisms and critical brain areas in the reversal effect of 5-HT2A receptor inverse agonists remain unclear. The present study aimed to investigate the critical brain areas responsible for the reversal effect of the 5-HT2A receptor inverse agonist on PPI deficits in male mice. The results showed that intraperitoneal administration of pimavanserin was found to improve normal PPI behavior and reverse PPI deficits elicited by the dopamine D1/D2 receptor nonselective agonist, pergolide. Further, local infusion of pimavanserin into the nucleus accumbens and ventral hippocampus reversed PPI deficits, whereas the same manipulation in the medial prefrontal cortex or ventral tegmental area did not reverse PPI deficits. Overall, the nucleus accumbens and ventral hippocampus are the critical brain areas responsible for the reversal effect of 5-HT2A inverse agonists on PPI deficits. Such findings contribute to the extensive exploration of the accurate molecular and neural mechanisms underlying the antipsychotic effects of 5-HT2A receptor inverse agonists, especially the neural circuits modulated by 5-HT2A receptor activity.

Identification of pimavanserin tartrate as a potent Ca2+-calcineurin-NFAT pathway inhibitor for glioblastoma therapy.

Glioblastoma multiforme (GBM) is the most common and malignant type of primary brain tumor, and 95% of patients die within 2 years after diagnosis. In this study, aiming to overcome chemoresistance to the first-line drug temozolomide (TMZ), we carried out research to discover a novel alternative drug targeting the oncogenic NFAT signaling pathway for GBM therapy. To accelerate the drug's clinical application, we took advantage of a drug repurposing strategy to identify novel NFAT signaling pathway inhibitors. After screening a set of 93 FDA-approved drugs with simple structures, we identified pimavanserin tartrate (PIM), an effective 5-HT2A receptor inverse agonist used for the treatment of Parkinson's disease-associated psychiatric symptoms, as having the most potent inhibitory activity against the NFAT signaling pathway. Further study revealed that PIM suppressed STIM1 puncta formation to inhibit store-operated calcium entry (SOCE) and subsequent NFAT activity. In cellula, PIM significantly suppressed the proliferation, migration, division, and motility of U87 glioblastoma cells, induced G1/S phase arrest and promoted apoptosis. In vivo, the growth of subcutaneous and orthotopic glioblastoma xenografts was markedly suppressed by PIM. Unbiased omics studies revealed the novel molecular mechanism of PIM's antitumor activity, which included suppression of the ATR/CDK2/E2F axis, MYC, and AuroraA/B signaling. Interestingly, the genes upregulated by PIM were largely associated with cholesterol homeostasis, which may contribute to PIM's side effects and should be given more attention. Our study identified store-operated calcium channels as novel targets of PIM and was the first to systematically highlight the therapeutic potential of pimavanserin tartrate for glioblastoma.

A Complex Impact of Systemically Administered 5-HT2A Receptor Ligands on Conditioned Fear.

BackgroundThough drugs binding to serotonergic 5-HT2A receptors have long been claimed to influence human anxiety, it remains unclear if this receptor subtype is best described as anxiety promoting or anxiety dampening. Whereas conditioned fear expressed as freezing in rats is modified by application of 5-HT2A–acting drugs locally into different brain regions, reports on the effect of systemic administration of 5-HT2A receptor agonists and 5-HT2A antagonists or inverse agonists on this behavior remain sparse.MethodsWe assessed the possible impact of systemic administration of 5-HT2A receptor agonists, 5-HT2A receptor inverse agonists, and a selective serotonin reuptake inhibitor (SSRI)—per se or in combination—on the freezing displayed by male rats when re-exposed to a conditioning chamber in which they received foot shocks 7 days earlier.ResultsThe 5-HT2A receptor agonists psilocybin and 25CN-NBOH induced a reduction in conditioned fear that was countered by pretreatment with 5-HT2A receptor inverse agonist MDL 100907. While both MDL 100907 and another 5-HT2A receptor inverse agonist, pimavanserin, failed to impact freezing per se, both compounds unmasked a robust fear-reducing effect of an SSRI, escitalopram, which by itself exerted no such effect.ConclusionsThe results indicate that 5-HT2A receptor activation is not a prerequisite for normal conditioned freezing in rats but that this receptor subtype, when selectively over-activated prior to expression, exerts a marked fear-reducing influence. However, in the presence of an SSRI, the 5-HT2A receptor, on the contrary, appears to counter an anti-freezing effect of the enhanced extracellular serotonin levels following reuptake inhibition.

Relevance of 5-HT2A Receptor Modulation of Pyramidal Cell Excitability for Dementia-Related Psychosis: Implications for Pharmacotherapy.

Psychosis occurs across a wide variety of dementias with differing etiologies, including Alzheimer’s dementia, Parkinson’s dementia, Lewy body dementia, frontotemporal dementia, and vascular dementia. Pimavanserin, a selective serotonin 5-HT2A receptor (5-HT2AR) inverse agonist, has shown promising results in clinical trials by reducing the frequency and/or severity of hallucinations and delusions and the risk of relapse of these symptoms in patients with dementia-related psychosis. A literature review was conducted to identify mechanisms that explain the role of 5-HT2ARs in both the etiology and treatment of dementia-related psychosis. This review revealed that most pathological changes commonly associated with neurodegenerative diseases cause one or more of the following events to occur: reduced synaptic contact of gamma aminobutyric acid (GABA)-ergic interneurons with glutamatergic pyramidal cells, reduced cortical innervation from subcortical structures, and altered 5-HT2AR expression levels. Each of these events promotes increased pyramidal cell hyperexcitability and disruption of excitatory/inhibitory balance, facilitating emergence of psychotic behaviors. The brain regions affected by these pathological changes largely coincide with areas expressing high levels of 5-HT2ARs. At the cellular level, 5-HT2ARs are most highly expressed on cortical glutamatergic pyramidal cells, where they regulate pyramidal cell excitability. The common effects of different neurodegenerative diseases on pyramidal cell excitability together with the close anatomical and functional connection of 5-HT2ARs to pyramidal cell excitability may explain why suppressing 5-HT2AR activity could be an effective strategy to treat dementia-related psychosis.

Pimavanserin, a 5HT2A receptor inverse agonist, rapidly suppresses Aβ production and related pathology in a mouse model of Alzheimer's disease.

Amyloid-β (Aβ) peptide aggregation into soluble oligomers and insoluble plaques is a precipitating event in the pathogenesis of Alzheimer's disease (AD). Given that synaptic activity can regulate Aβ generation, we postulated that 5HT2A -Rs may regulate Aβ as well. We treated APP/PS1 transgenic mice with the selective 5HT2A inverse agonists M100907 or Pimavanserin systemically and measured brain interstitial fluid (ISF) Aβ levels in real-time using in vivo microdialysis. Both compounds reduced ISF Aβ levels by almost 50% within hours, but had no effect on Aβ levels in 5HT2A -R knock-out mice. The Aβ-lowering effects of Pimavanserin were blocked by extracellular-regulated kinase (ERK) and NMDA receptor inhibitors. Chronic administration of Pimavanserin by subcutaneous osmotic pump to aged APP/PS1 mice significantly reduced CSF Aβ levels and Aβ pathology and improved cognitive function in these mice. Pimavanserin is FDA-approved to treat Parkinson's disease psychosis, and also has been shown to reduce psychosis in a variety of other dementia subtypes including Alzheimer's disease. These data demonstrate that Pimavanserin may have disease-modifying benefits in addition to its efficacy against neuropsychiatric symptoms of Alzheimer's disease. Read the Editorial Highlight for this article on page 560.

A patient with nocturnal visual hallucinations.

Citation:Dholakia S. A patient with nocturnal visual hallucinations. J Clin Sleep Med. 2020;16(5):821–822.

P.089 Pimavanserin behaves as serotonin 5-HT2A receptor inverse agonist selective for gαi/o but not gαq/11 proteins in human prefrontal cortex

P.089 Pimavanserin behaves as serotonin 5-HT2A receptor inverse agonist selective for gαi/o but not gαq/11 proteins in human prefrontal cortex

Big Data Challenges Targeting Proteins in GPCR Signaling Pathways; Combining PTML-ChEMBL Models and [35S]GTPγS Binding Assays.

G-protein-coupled receptors (GPCRs), also known as 7-transmembrane receptors, are the single largest class of drug targets. Consequently, a large amount of preclinical assays having GPCRs as molecular targets has been released to public sources like the Chemical European Molecular Biology Laboratory (ChEMBL) database. These data are also very complex covering changes in drug chemical structure and assay conditions like c0 = activity parameter (Ki, IC50, etc.), c1 = target protein, c2 = cell line, c3 = assay organism, etc., making difficult the analysis of these databases that are placed in the borders of a Big Data challenge. One of the aims of this work is to develop a computational model able to predict new GPCRs targeting drugs taking into consideration multiple conditions of assay. Another objective is to perform new predictive and experimental studies of selective 5-HTA2 receptor agonist, antagonist, or inverse agonist in human comparing the results with those from the literature. In this work, we combined Perturbation Theory (PT) and Machine Learning (ML) to seek a general PTML model for this data set. We analyzed 343 738 unique compounds with 812 072 end points (assay outcomes), with 185 different experimental parameters, 592 protein targets, 51 cell lines, and/or 55 organisms (species). The best PTML linear model found has three input variables only and predicted 56 202/58 653 positive outcomes (sensitivity = 95.8%) and 470 230/550 401 control cases (specificity = 85.4%) in training series. The model also predicted correctly 18 732/19 549 (95.8%) of positive outcomes and 156 739/183 469 (85.4%) of cases in external validation series. To illustrate its practical use, we used the model to predict the outcomes of six different 5-HT2A receptor drugs, namely, TCB-2, DOI, DOB, altanserin, pimavanserin, and nelotanserin, in a very large number of different pharmacological assays. 5-HT2A receptors are altered in schizophrenia and represent drug target for antipsychotic therapeutic activity. The model correctly predicted 93.83% (76 of 86) experimental results for these compounds reported in ChEMBL. Moreover, [35S]GTPγS binding assays were performed experimentally with the same six drugs with the aim of determining their potency and efficacy in the modulation of G-proteins in human brain tissue. The antagonist ketanserin was included as inactive drug with demonstrated affinity for 5-HT2A/C receptors. Our results demonstrate that some of these drugs, previously described as serotonin 5-HT2A receptor agonists, antagonists, or inverse agonists, are not so specific and show different intrinsic activity to that previously reported. Overall, this work opens a new gate for the prediction of GPCRs targeting compounds.

Year in Review: Applying Top Research to the Practice of PALTC Medicine

Year in Review: Applying Top Research to the Practice of PALTC Medicine