In Vitro Comparison of Ulotaront (SEP-363856) and Ralmitaront (RO6889450): Two TAAR1 Agonist Candidate Antipsychotics.

BACKGROUND: Trace amine-associated receptor-1 (TAAR1) agonists have been proposed as potential antipsychotics, with ulotaront and ralmitaront having reached clinical trials. While ulotaront demonstrated efficacy in a recent Phase II trial, a corresponding study studies of ralmitaront failed to show efficacy as a monotherapy or as an adjunct to atypical antipsychotics. In addition to TAAR1 agonism, ulotaront is a partial agonist at the serotonin 1A receptor (5-HT1AR). However, little is known about ralmitaront. METHODS: We compared ulotaront and ralmitaront at TAAR1, 5-HT1AR, and dopamine D2 using luciferase complementation-based G protein recruitment, cAMP accumulation, and G protein-coupled inward rectifier potassium channel activation assays. RESULTS: Ralmitaront showed lower efficacy at TAAR1 in G protein recruitment, cAMP accumulation, and GIRK activation assays. Moreover, ralmitaront lacked detectable activity at 5-HT1AR and dopamine D2. CONCLUSIONS: Compared with ulotaront, ralmitaront shows lower efficacy and slower kinetics at TAAR1 and lacks efficacy at 5-HT1AR. These data may be relevant to understanding differences in clinical profiles of these 2 compounds.

Dopamine-induced arrestin recruitment and desensitization of the dopamine D4 receptor is regulated by G protein-coupled receptor kinase-2.

The dopamine D4 receptor (D4R) is expressed in the retina, prefrontal cortex, and autonomic nervous system and has been implicated in attention deficit hyperactivity disorder (ADHD), substance use disorders, and erectile dysfunction. D4R has also been investigated as a target for antipsychotics due to its high affinity for clozapine. As opposed to the closely related dopamine D2 receptor (D2R), dopamine-induced arrestin recruitment and desensitization at the D4R have not been studied in detail. Indeed, some earlier investigations could not detect arrestin recruitment and desensitization of this receptor upon its activation by agonist. Here, we used a novel nanoluciferase complementation assay to study dopamine-induced recruitment of ß-arrestin2 (ßarr2; also known as arrestin3) and G protein-coupled receptor kinase-2 (GRK2) to the D4R in HEK293T cells. We also studied desensitization of D4R-evoked G protein-coupled inward rectifier potassium (GIRK; also known as Kir3) current responses in Xenopus oocytes. Furthermore, the effect of coexpression of GRK2 on ßarr2 recruitment and GIRK response desensitization was examined. The results suggest that coexpression of GRK2 enhanced the potency of dopamine to induce ßarr2 recruitment to the D4R and accelerated the rate of desensitization of D4R-evoked GIRK responses. The present study reveals new details about the regulation of arrestin recruitment to the D4R and thus increases our understanding of the signaling and desensitization of this receptor.

ADHD symptoms in neurometabolic diseases: Underlying mechanisms and clinical implications.

Neurometabolic diseases (NMDs) are typically caused by genetic abnormalities affecting enzyme functions, which in turn interfere with normal development and activity of the nervous system. Although the individual disorders are rare, NMDs are collectively relatively common and often lead to lifelong difficulties and high societal costs. Neuropsychiatric manifestations, including ADHD symptoms, are prominent in many NMDs, also when the primary biochemical defect originates in cells and tissues outside the nervous system. ADHD symptoms have been described in phenylketonuria, tyrosinemias, alkaptonuria, succinic semialdehyde dehydrogenase deficiency, X-linked ichthyosis, maple syrup urine disease, and several mitochondrial disorders, but are probably present in many other NMDs and may pose diagnostic and therapeutic challenges. Here we review current literature linking NMDs with ADHD symptoms. We cite emerging evidence that many NMDs converge on common neurochemical mechanisms that interfere with monoamine neurotransmitter synthesis, transport, metabolism, or receptor functions, mechanisms that are also considered central in ADHD pathophysiology and treatment. Finally, we discuss the therapeutic implications of these findings and propose a path forward to increase our understanding of these relationships.

Synthetic corticosteroids as tryptophan hydroxylase stabilizers.

Background: Clinically, corticosteroids are used mainly for their immune-modulatory properties but are also known to influence mood. Despite evidence of a role in regulating tryptophan hydroxylases (TPH), key enzymes in serotonin biosynthesis, a direct action of corticosteroids on these enzymes has not been systematically investigated. Methodology & results: Corticosteroid effects on TPHs were tested using an in vitro assay. The compound with the strongest modulatory effect, beclomethasone dipropionate, activated TPH1 and TPH2 with low micromolar potency. Thermostability assays suggested a stabilizing mechanism, and computational docking indicated that beclomethasone dipropionate interacts with the TPH active site. Conclusion: Beclomethasone dipropionate is a stabilizer of TPHs, acting as a pharmacological chaperone. Our findings may inspire further development of steroid scaffolds as putative antidepressant drugs.

Inhibition of Tryptophan Hydroxylases and Monoamine Oxidase-A by the Proton Pump Inhibitor, Omeprazole-In Vitro and In Vivo Investigations.

Serotonin (5-HT) is a hormone and neurotransmitter that modulates neural activity as well as a wide range of other physiological processes including cardiovascular function, bowel motility, and platelet aggregation. 5-HT synthesis is catalyzed by tryptophan hydroxylase (TPH) which exists as two distinct isoforms; TPH1 and TPH2, which are responsible for peripheral and central 5-HT, respectively. Due to the implication of 5-HT in a number of pathologies, including depression, anxiety, autism, sexual dysfunction, irritable bowel syndrome, inflammatory bowel disease, and carcinoid syndrome, there has been a growing interest in finding modulators of these enzymes in recent years. We thus performed high-throughput screening (HTS) using a fluorescence-based thermal shift assay (DSF) to search the Prestwick Chemical Library containing 1,280 compounds, mostly FDA-approved drugs, for TPH1 binders. We here report the identification of omeprazole, a proton pump inhibitor, as an inhibitor of TPH1 and TPH2 with low micromolar potency and high selectivity over the other aromatic amino acid hydroxylases. The S-enantiomer of omeprazole, esomeprazole, has recently also been described as an inhibitor of monoamine oxidase-A (MAO-A), the main enzyme responsible for 5-HT degradation, albeit with lower potency compared to the effect on TPH1 and TPH2. In order to investigate the net effect of simultaneous inhibition of TPH and MAO-A in vivo, we administered high-dose (100 mg/kg) omeprazole to CD-1 mice for 4 days, after which the animals were subjected to the tail suspension test. Finally, central (whole brain) and peripheral (serum) 5-HT content was measured using liquid chromatography-mass spectrometry (LC-MS). Omeprazole treatment significantly increased 5-HT concentrations, both in brain and in serum, and reduced the time spent immobile in the tail suspension test relative to vehicle control. Thus, the MAO-A inhibition afforded by high-dose omeprazole appears to overcome the opposing effect on 5-HT produced by inhibition of TPH1 and TPH2. Further modification of proton pump inhibitor scaffolds may yield more selective modulators of 5-HT metabolism.

Discovery and biological characterization of a novel scaffold for potent inhibitors of peripheral serotonin synthesis.

Aim: Tryptophan hydroxylase 1 (TPH1) catalyzes serotonin synthesis in peripheral tissues. Selective TPH1 inhibitors may be useful for treating disorders related to serotonin dysregulation. Results & methodology: Screening using a thermal shift assay for TPH1 binders yielded Compound 1 (2-(4-methylphenyl)-1,2-benzisothiazol-3(2H)-one), which showed high potency (50% inhibition at 98 ± 30 nM) and selectivity for inhibiting TPH over related aromatic amino acid hydroxylases in enzyme activity assays. Structure-activity relationships studies revealed several analogs of 1 showing comparable potency. Kinetic studies suggested a noncompetitive mode of action of 1, with regards to tryptophan and tetrahydrobiopterin. Computational docking studies and live cell assays were also performed. Conclusion: This TPH1 inhibitor scaffold may be useful for developing new therapeutics for treating elevated peripheral serotonin.

Targeting topoisomerase II with trypthantrin derivatives: Discovery of 7-((2-(dimethylamino)ethyl)amino)indolo[2,1-b]quinazoline-6,12-dione as an antiproliferative agent and to treat cancer.

Drugs targeting human topoisomerase II (topoII) are used in clinical practice since decades. Nevertheless, there is an urgent need for new and safer topoII inhibitors due to the emergence of secondary malignancies and the appearance of resistance mechanisms upon treatment with topoII-targeted anticancer drugs. In the present investigation, we report the discovery of a new topoII inhibitor, whose design was based on the structure of the natural product trypthantrin, a natural alkaloid containing a basic indoloquinazoline moiety. This new topoII inhibitor, here numbered compound 5, is found to inhibit topoII with an IC50 of 26.6 ± 4.7 µM. Notably, compound 5 is more potent than the template compound trypthantrin, and even than the widely used topoII-targeted clinical drug etoposide. In addition, compound 5 also exhibits high water solubility, and a promising antiproliferative activity on different tumor cell lines such as acute leukemia, colon, and breast cancer. In light of these results, compound 5 represents a promising lead for developing new topoII inhibitors as anti-cancer therapeutic agents.

Correction to "Discovery of the First-in-Class GSK-3ß/HDAC Dual Inhibitor as Disease-Modifying Agent To Combat Alzheimer's Disease".

[This corrects the article DOI: 10.1021/acsmedchemlett.8b00507.].

Discovery of the First-in-Class GSK-3ß/HDAC Dual Inhibitor as Disease-Modifying Agent To Combat Alzheimer's Disease.

Several evidence pointed out the role of epigenetics in Alzheimer's disease (AD) revealing strictly relationships between epigenetic and "classical" AD targets. Based on the reported connection among histone deacetylases (HDACs) and glycogen synthase kinase 3ß (GSK-3ß), herein we present the discovery and the biochemical characterization of the first-in-class hit compound able to exert promising anti-AD effects by modulating the targeted proteins in the low micromolar range of concentration. Compound 11 induces an increase in histone acetylation and a reduction of tau phosphorylation. It is nontoxic and protective against H2O2 and 6-OHDA stimuli in SH-SY5Y and in CGN cell lines, respectively. Moreover, it promotes neurogenesis and displays immunomodulatory effects. Compound 11 shows no lethality in a wt-zebrafish model (<100 µM) and high water solubility.

Design, synthesis and multitarget biological profiling of second-generation anti-Alzheimer rhein-huprine hybrids.

AIM: Simultaneous modulation of several key targets of the pathological network of Alzheimer's disease (AD) is being increasingly pursued as a promising option to fill the critical gap of efficacious drugs against this condition. MATERIALS & METHODS: A short series of compounds purported to hit multiple targets of relevance in AD has been designed, on the basis of their distinct basicities estimated from high-level quantum mechanical computations, synthesized, and subjected to assays of inhibition of cholinesterases, BACE-1, and Aß42 and tau aggregation, of antioxidant activity, and of brain permeation. RESULTS: Using, as a template, a lead rhein-huprine hybrid with an interesting multitarget profile, we have developed second-generation compounds, designed by the modification of the huprine aromatic ring. Replacement by [1,8]-naphthyridine or thieno[3,2-e]pyridine systems resulted in decreased, although still potent, acetylcholinesterase or BACE-1 inhibitory activities, which are more balanced relative to their Aß42 and tau antiaggregating and antioxidant activities. CONCLUSION: Second-generation naphthyridine- and thienopyridine-based rhein-huprine hybrids emerge as interesting brain permeable compounds that hit several crucial pathogenic factors of AD.

Tacrine-based Multifunctional Agents in Alzheimer's Disease: An Old Story in Continuous Development§.

BACKGROUND: The design of multifunctional agents represents one of the most active research field in medicinal chemistry. In particular, tacrine, a well known Acetylcholinesterase inhibitor, is one of the most used starting point to develop multifunctional ligands and hundreds of papers report about these new agents. This is the third review of a series concerning tacrinebased multifunctional ligands; in particular, in the present, we will summarize and discuss the most intriguing examples of tacrine-based multifunctional agents published since 2013 until 2016. METHODS: We analyzed the bibliographic databases for peer-reviewed publications concerning tacrine-based multifunctional agents possessing biological actions that go beyond the simple "cholinergic" blockage. These papers have been subdivided according to their biological activities. Since this is the third review of a series, we took into considerations only the papers appeared since 2013 until 2016. RESULTS: In this review, we have analyzed more than 33 papers. All the reported compounds retain good inhibitory activity towards acetyl- and butyryl-cholinesterase. The other biological activities concern mostly inhibition of a) ß-amyloid aggregation, b) ß-secretase, c) monoamino oxidases, modulation of τ and ROS and metal chelation. CONCLUSION: The analysis of the current literature reported in this review confirm the importance of tacrine as scaffold to develop multifunctional agents potentially usefull to contrast Alzheimer's disease. Furthermore, the compounds herein reported showed very intriguing biological activities that could be used as starting point to develop new compounds even more interesting and, hopefully, clinically usefull to contrast Alzheimer's Disease.

Naphthalene diimide-polyamine hybrids as antiproliferative agents: Focus on the architecture of the polyamine chains.

Naphthalene diimides (NDIs) have been widely used as scaffold to design DNA-directed agents able to target peculiar DNA secondary arrangements endowed with relevant biochemical roles. Recently, we have reported disubstituted linear- and macrocyclic-NDIs that bind telomeric and non-telomeric G-quadruplex with high degree of affinity and selectivity. Herein, the synthesis, biological evaluation and molecular modelling studies of a series of asymmetrically substituted NDIs are reported. Among these, compound 9 emerges as the most interesting of the series being able to bind telomeric G-quadruplex (ΔTm = 29 °C at 2.5 µM), to inhibit the activity of DNA processing enzymes, such as topoisomerase II and TAQ-polymerase, and to exert antiproliferative effects in the NCI panel of cancer cell lines with GI50 values in the micro-to nanomolar concentration range (i.e. SR cell line, GI50 = 76 nM). Molecular mechanisms of cell death have been investigated and molecular modelling studies have been performed in order to shed light on the antiproliferative and DNA-recognition processes.