Discovery and Preclinical Characterization of Usmarapride (SUVN-D4010): A Potent, Selective 5-HT4 Receptor Partial Agonist for the Treatment of Cognitive Deficits Associated with Alzheimer's Disease.

A series of oxadiazole derivatives were synthesized and evaluated as 5-hydroxytryptamine-4 receptor (5-HT4R) partial agonists for the treatment of cognitive deficits associated with Alzheimer's disease. Starting from a reported 5-HT4R antagonist, a systematic structure-activity relationship was conducted, which led to the discovery of potent and selective 5-HT4R partial agonist 1-isopropyl-3-{5-[1-(3-methoxypropyl) piperidin-4-yl]-[1,3,4]oxadiazol-2-yl}-1H-indazole oxalate (Usmarapride, 12l). It showed balanced physicochemical-pharmacokinetic properties with robust nonclinical efficacy in cognition models. It also showed disease-modifying potential, as it increased neuroprotective soluble amyloid precursor protein alpha levels, and dose-dependent target engagement and correlation of efficacy with oral exposures. Phase 1 clinical studies have been completed and projected efficacious concentration was achieved without any major safety concerns. Phase 2 enabling long-term safety studies have been completed with no concerns for further development.

Understanding the Molecular Basis of 5-HT4 Receptor Partial Agonists through 3D-QSAR Studies.

Alzheimer's disease (AD) is a neurodegenerative disorder whose prevalence has an incidence in senior citizens. Unfortunately, current pharmacotherapy only offers symptom relief for patients with side effects such as bradycardia, nausea, and vomiting. Therefore, there is a present need to provide other therapeutic alternatives for treatments for these disorders. The 5-HT4 receptor is an attractive therapeutic target since it has a potential role in central and peripheral nervous system disorders such as AD, irritable bowel syndrome, and gastroparesis. Quantitative structure-activity relationship analysis of a series of 62 active compounds in the 5-HT4 receptor was carried out in the present work. The structure-activity relationship was estimated using three-dimensional quantitative structure-activity relationship (3D-QSAR) techniques based on these structures' field molecular (force and Gaussian field). The best force-field QSAR models achieve a value for the coefficient of determination of the training set of R2training = 0.821, and for the test set R2test = 0.667, while for Gaussian-field QSAR the training and the test were R2training = 0.898 and R2test = 0.695, respectively. The obtained results were validated using a coefficient of correlation of the leave-one-out cross-validation of Q2LOO = 0.804 and Q2LOO = 0.886 for force- and Gaussian-field QSAR, respectively. Based on these results, novel 5-HT4 partial agonists with potential biological activity (pEC50 8.209-9.417 for force-field QSAR and 9.111-9.856 for Gaussian-field QSAR) were designed. In addition, for the new analogues, their absorption, distribution, metabolism, excretion, and toxicity properties were also analyzed. The results show that these new derivatives also have reasonable pharmacokinetics and drug-like properties. Our findings suggest novel routes for the design and development of new 5-HT4 partial agonists.

Novel multi target-directed ligands targeting 5-HT4 receptors with in cellulo antioxidant properties as promising leads in Alzheimer's disease.

Facing the complexity of Alzheimer's disease (AD), it is now currently admitted that a therapeutic pleiotropic intervention is needed to alter its progression. Among the major hallmarks of the disease, the amyloid pathology and the oxidative stress are closely related. We propose in this study to develop original Multi-Target Directed Ligands (MTDL) able to impact at the same time Aß protein accumulation and toxicity of Reactive Oxygen Species (ROS) in neuronal cells. Such MTDL were obtained by linking on a central piperidine two scaffolds of interest: a typical aminochlorobenzophenone present in numerous 5-HT4R agonists, and diverse antioxidant chemotypes. Interestingly, the most active compound 9g possesses a Ki of 12.7 nM towards 5-HT4R and an antioxidant activity in vitro and in cellulo.

Synthesis, Structure-Activity Relationships, and Preclinical Evaluation of Heteroaromatic Amides and 1,3,4-Oxadiazole Derivatives as 5-HT4 Receptor Partial Agonists.

Alzheimer's disease (AD) is a neurodegenerative disorder that has a higher prevalence and incidence in people older than 60 years. The need for improved AD therapies is unmet as the current therapies are symptomatic with modest efficacy. Partial agonists of the 5-HT4 receptor (5-HT4R) offer both symptomatic and disease-modifying treatments as they shift amyloid-precursor-protein (APP) processing from the amyloidogenic pathway to the nonamyloidogenic pathway by activating the α-secretase enzyme. In addition, they also offer symptomatic treatment by increasing levels of the neurotransmitter acetylcholine in the brain. Because of this fascinating dual mechanism of action, several chemical scaffolds having 5-HT4R pharmacophores were designed and evaluated. Most of the synthesized compounds showed potent in vitro affinities and in vivo efficacies. Upon analysis of focused structure-activity relationships, compound 4o was identified as a potent 5-HT4R partial agonist with favorable ADME properties and good in vivo efficacy. GR-125487, a selective 5-HT4R antagonist, attenuated the activity of compound 4o in the novel-object-recognition-test cognition model.

Development and validation of a chiral liquid chromatography method for the determination of MP 3950 enantiomers, a high selective 5-HT4 receptor agonist, in rat plasma and its application to stereoselective pharmacokinetic study.

MP 3950 is an active metabolite of mosapride which exhibits high 5-HT4 receptor agonistic effect. The present paper describes an enantioselective chiral HPLC method for separation and quantification of MP 3950 enantiomers in rat plasma. The plasma samples were prepared by liquid-liquid extraction with ethyl acetate and the baseline chromatographic separation was achieved on a Chiralcel OJ-H column with a mobile phase consisting n-hexane/ethanol/methanol/diethylamine (85:5:10:0.4, v/v/v/v) at the flow rate of 1.0mL/min. The ultraviolet detection was performed at 276nm. The calibration curve was linear in the range from 0.100 to 5.00µg/mL with the lower limit of quantification of 0.100µg/mL for each enantiomer. The intra- and inter-day precisions were not more than 14.7%. The accuracy was from -6.4% to 14.0%. The validated method was successfully applied to chiral inversion and stereoselective pharmacokinetic study in rats after oral administration of MP 3950 racemate. The results indicated that no stereochemical inversion was occurred in rats. And the plasma concentrations and area under plasma concentration-time curve of (S)-MP 3950 were all significantly higher than those of (R)-MP 3950 in both male and female rats, which indicated that the disposition of MP 3950 in rats might be stereoselective.

Design, synthesis, and pharmacological evaluation of multitarget-directed ligands with both serotonergic subtype 4 receptor (5-HT4R) partial agonist and 5-HT6R antagonist activities, as potential treatment of Alzheimer's disease.

5-HT4 receptor (5-HT4R) activation and blockade of the 5-HT6 receptor (5-HT6R) are known to enhance the release of numerous neurotransmitters whose depletion is implicated in Alzheimer's disease (AD). Furthermore, 5-HT4R agonists seem to favor production of the neurotrophic soluble amyloid protein precursor alpha (sAPPα). Consequently, combining 5-HT4R agonist/5-HT6R antagonist activities in a single chemical compound would constitute a novel approach able to display both a symptomatic and disease-modifying effect in AD. Seventeen novel derivatives of RS67333 (1) were synthesized and evaluated as potential dual-target compounds. Among them, four agents showed nanomolar and submicromolar affinities toward 5-HT4R and 5-HT6R, respectively; one of them, 7m, was selected on the basis of its in vitro affinity (Ki5-HT4R = 5.3 nM, Ki5-HT6R = 219 nM) for further in vivo experiments, where 7m showed an antiamnesic effect in the mouse at 1 mg/kg ip.

Discovery and SAR of N-(1-((substituted piperidin-4-yl)methyl)-3-methoxypiperidin-4-yl)-2-methoxybenzamide derivatives: 5-Hydroxytryptamine receptor 4 agonist as a potent prokinetic agent.

A series of novel benzamide derivatives, altering the 4-fluorophenylalkyl moiety in cisapride, were synthesized as 5-HT4 receptor agonists, and SAR of these analogs was examined on in vitro and in vivo prokinetic activities. These compounds were synthesized for high 5-HT4 receptor binding affinities and low hERG affinities. Several types of analogs were obtained and screened for 5-HT4 binding, hERG blocking, agonism, and gastric emptying assessment. Among the analogues, compound 23g showed promising results compared with the other analogs with respect to gastric emptying rates in rats. Therefore, we suggest that it may be a clinical candidate for the development of a potent prokinetic agent to treat GI disorders.

A phase 1 randomized study evaluating the effect of omeprazole on the pharmacokinetics of a novel 5-hydroxytryptamine receptor 4 agonist, revexepride (SSP-002358), in healthy adults.

BACKGROUND: About 30% of patients with gastroesophageal reflux disease continue to experience symptoms despite treatment with proton pump inhibitors. The 5-hydroxytryptamine 4 receptor agonist revexepride (SSP-002358) is a novel prokinetic that stimulates gastrointestinal motility, which has been suggested as a continued cause of symptoms in these patients. The aim of this study was to assess whether revexepride pharmacokinetics were affected by co-administration of omeprazole, in preparation for a proof-of-concept evaluation of revexepride added to proton pump inhibitor treatment. METHODS: In this phase 1, open-label, randomized, two-period crossover study, healthy adults aged 18-55 years were given a single dose of revexepride 1 mg or revexepride 1 mg + omeprazole 40 mg. Pharmacokinetic parameters were assessed for up to 48 hours after administration of the investigational product. Adverse events, clinical chemistry and hematology parameters, electrocardiograms, and vital signs were monitored. RESULTS: In total, 42 participants were enrolled and 40 completed the study. The median age was 24 years (18-54 years), 55% were women and 93% were white. The pharmacokinetic parameters of revexepride were similar without or with omeprazole co-administration. The mean area under the plasma concentration-time curve from time 0 to infinity (AUC0-∞) was 23.3 ng · h/mL (standard deviation [SD]: 6.33 ng · h/mL) versus 24.6 ng · h/mL (SD: 6.31 ng · h/mL), and maximum plasma concentrations (Cmax) were 3.89 ng/mL (SD: 1.30 ng/mL) and 4.12 ng/mL (SD: 1.29 ng/mL) in participants without and with omeprazole, respectively. For AUC0-∞ and Cmax, the 90% confidence intervals for the ratios of geometric least-squares means (with:without omeprazole) were fully contained within the pre-defined equivalence limits of 0.80-1.25. Mean apparent terminal phase half-life was 9.95 hours (SD: 2.06 hours) without omeprazole, and 11.0 hours (SD: 3.25 hours) with omeprazole. CONCLUSION: Co-administration of the 5-hydroxytryptamine receptor 4 agonist revexepride with omeprazole did not affect the pharmacokinetics of revexepride in healthy adults.

Novel multitarget-directed ligands (MTDLs) with acetylcholinesterase (AChE) inhibitory and serotonergic subtype 4 receptor (5-HT4R) agonist activities as potential agents against Alzheimer's disease: the design of donecopride.

In this work, we describe the synthesis and in vitro evaluation of a novel series of multitarget-directed ligands (MTDL) displaying both nanomolar dual-binding site (DBS) acetylcholinesterase inhibitory effects and partial 5-HT4R agonist activity, among which donecopride was selected for further in vivo evaluations in mice. The latter displayed procognitive and antiamnesic effects and enhanced sAPPα release, accounting for a potential symptomatic and disease-modifying therapeutic benefit in the treatment of Alzheimer's disease.

Design of donecopride, a dual serotonin subtype 4 receptor agonist/acetylcholinesterase inhibitor with potential interest for Alzheimer's disease treatment.

RS67333 is a partial serotonin subtype 4 receptor (5-HT4R) agonist that has been widely studied for its procognitive effect. More recently, it has been shown that its ability to promote the nonamyloidogenic cleavage of the precursor of the neurotoxic amyloid-ß peptide leads to the secretion of the neurotrophic protein sAPPα. This effect has generated great interest in RS67333 as a potential treatment for Alzheimer's disease (AD). We show herein that RS67333 is also a submicromolar acetylcholinesterase (AChE) inhibitor and therefore, could contribute, through this effect, to the restoration of the cholinergic neurotransmission that becomes altered in AD. We planned to pharmacomodulate RS67333 to enhance its AChE inhibitory activity to take advantage of this pleiotropic pharmacological profile in the design of a novel multitarget-directed ligand that is able to exert not only a symptomatic but also, a disease-modifying effect against AD. These efforts allowed us to select donecopride as a valuable dual (h)5-HT4R partial agonist (Ki = 10.4 nM; 48.3% of control agonist response)/(h)AChEI (IC50 = 16 nM) that further promotes sAPPα release (EC50 = 11.3 nM). Donecopride, as a druggable lead, was assessed for its in vivo procognitive effects (0.1, 0.3, 1, and 3 mg/kg) with an improvement of memory performances observed at 0.3 and 1 mg/kg on the object recognition test. On the basis of these in vitro and in vivo activities, donecopride seems to be a promising drug candidate for AD treatment.

Synthesis and structure-activity relationship studies in serotonin 5-HT4 receptor ligands based on a benzo[de][2,6]naphthridine scaffold.

A small series of serotonin 5-HT4 receptor ligands has been designed from flexible 2-methoxyquinoline compounds 7a,b by applying the conformational constraint approach. Ligands 7a,b and the corresponding conformationally constrained analogues 8a-g were synthesized and their interactions with the 5-HT4 receptor were examined by measuring both binding affinity and the ability to promote or inhibit receptor-G protein coupling. Ester derivative 7a and conformationally constrained compound 8b were demonstrated to be the most interesting compounds showing a nanomolar 5-HT4R affinity similar to that shown by reference ligands cisapride (1) and RS-23,597-190 (4). The result was rationalized by docking studies in term of high similarity in the binding modalities of flexible 7a and conformationally constrained 8b. The intrinsic efficacy of some selected ligands was determined by evaluating the receptor-G protein coupling and the results obtained demonstrated that the nature and the position of substituents play a critical role in the interaction of these ligands with their receptor.

Dual histamine H3R/serotonin 5-HT4R ligands with antiamnesic properties: pharmacophore-based virtual screening and polypharmacology.

In recent years, preclinical and clinical studies have generated considerable interest in the development of histamine H3 receptor (H3R) antagonists as novel treatment for degenerative disorders associated with impaired cholinergic function. To identify novel scaffolds for H3R antagonism, a common feature-based pharmacophore model was developed and used to screen the 17,194 compounds of the CERMN (Centre d'Etudes et de Recherche sur le Médicament de Normandie) chemical library. Out of 268 virtual hits which have been gathered in 34 clusters, we were particularly interested in tricyclic derivatives also exhibiting a potent 5HT4R affinity. Benzo[h][1,6]naphthyridine derivatives showed the highest H3R affinity, and compound 17 (H3R Ki = 41.6 nM; 5-HT4R Ki = 208 nM) completely reversed the amnesiant effect of scopolamine at 3 mg/kg in a spatial working memory experiment. For the first time we demonstrated the feasibility to combine H3R and 5-HT4R activities in a single molecule, raising the exciting possibility that dual H3R antagonist/5HT4R agonist have potential for the treatment of neurodegenerative diseases such as Alzheimer's disease.

Discovery of TD-8954, a clinical stage 5-HT(4) receptor agonist with gastrointestinal prokinetic properties.

The discovery of a series of 5-HT4 receptor agonists based on a novel 2-alkylbenzimidazole aromatic core is described. Optimization of the 2-substituent of the benzimidazole ring led to a series of agonists with subnanomolar binding affinity and moderate-to-high intrinsic activity relative to that of 5-HT. Consistent with our previously described multivalent design approach to this target, subsequent optimization of the linker and secondary binding group regions of the series afforded compound 18 (TD-8954), a potent and selective 5-HT4 receptor agonist in vitro with demonstrated prokinetic activity in multiple species.

Metabolism of a serotonin-4 receptor partial agonist 4-{4-[4-tetrahydrofuran-3-yloxy)-benzo[d]isoxazol-3-yloxymethyl]-piperidin-1-ylmethyl}-tetrahydropyran-4-ol (TBPT): identification of an unusual pharmacologically active cyclized oxazolidine metabolite in human.

4-{4-[4-Tetrahydrofuran-3-yloxy)-benzo[d]isoxazol-3-yloxymethyl]-piperidin-1-ylmethyl}-tetrahydropyran-4-ol (PF-4995274, TBPT) is a new agent that is a partial agonist of the human serotonin-4 (5-HT4) receptor and is under investigation for neurological disorders. Metabolism of TBPT was examined in vitro in human liver microsomes and human hepatocytes. Metabolites were also identified in the plasma of healthy human subjects in a phase 1 clinical study. Human-derived metabolite profiles were compared with corresponding profiles obtained in laboratory animal species. There were two major routes of metabolism in vitro: N-dealkylation of the methyltetrahydropyran moiety (M1) and hydroxylation at the seven position of the benzisoxazole moiety (M4). These were also observed in human plasma; however, in that matrix, the major metabolite was an unusual cyclized oxazolidine entity (M2). M2 was proposed to be formed via generation of an intermediate 4° iminium ion on the piperidine ring followed by spontaneous cyclization by attack of the ß-hydroxyl substituent of the tetrahydropyran ring to form a cyclized oxazolidine product. An authentic standard of the metabolite was generated using a methylene-blue-sensitized photochemical oxidation reaction as well as microbial transformation. Further investigation of this metabolite showed that it also possessed 5-HT4 agonism activity similar to the parent. The metabolite was 150-fold more highly protein bound in human plasma than TBPT, which is consistent with its presence as a major circulating metabolite while being only a minor metabolite in in vitro systems. Overall, this illustrates the importance of understanding the complex dispositional properties of a pharmacologically active metabolite.

Discovery, oral pharmacokinetics and in vivo efficacy of velusetrag, a highly selective 5-HT(4) receptor agonist that has achieved proof-of-concept in patients with chronic idiopathic constipation.

Utilization of Theravance's multivalent approach to drug discovery towards 5-HT(4) receptor agonists with a focus on identification of neutral (non-charged at physiological pH) secondary binding groups is described. Optimization of a quinolone-tropane primary binding group with a chiral 2-propanol linker to a range of neutral secondary binding group motifs, for binding affinity and functional potency at the 5-HT(4) receptor, selectivity over the 5-HT(3) receptor, oral pharmacokinetics, and in vivo efficacy in models of GI motility, afforded velusetrag (TD-5108). Velusetrag has achieved proof-of-concept in patients with chronic idiopathic constipation.

Discovery, oral pharmacokinetics and in vivo efficacy of a highly selective 5-HT4 receptor agonist: clinical compound TD-2749.

Further application of our multivalent approach to drug discovery directed to 5-HT(4) receptor agonists is described. Optimization of the linker and secondary binding amine in the indazole-tropane primary binding group series, for binding affinity and functional potency at the 5-HT(4) receptor, selectivity over the 5-HT(3) receptor, oral pharmacokinetics, and in vivo efficacy in models of GI motility, resulted in the identification of clinical compound TD-2749.