A uniquely efficacious type of CFTR corrector with complementary mode of action.

Three distinct pharmacological corrector types (I, II, III) with different binding sites and additive behavior only partially rescue the F508del-cystic fibrosis transmembrane conductance regulator (CFTR) folding and trafficking defect observed in cystic fibrosis. We describe uniquely effective, macrocyclic CFTR correctors that were additive to the known corrector types, exerting a complementary "type IV" corrector mechanism. Macrocycles achieved wild-type-like folding efficiency of F508del-CFTR at the endoplasmic reticulum and normalized CFTR currents in reconstituted patient-derived bronchial epithelium. Using photo-activatable macrocycles, docking studies and site-directed mutagenesis a highly probable binding site and pose for type IV correctors was identified in a cavity between lasso helix-1 (Lh1) and transmembrane helix-1 of membrane spanning domain (MSD)-1, distinct from the known corrector binding sites. Since only F508del-CFTR fragments spanning from Lh1 until MSD2 responded to type IV correctors, these likely promote cotranslational assembly of Lh1, MSD1, and MSD2. Previously corrector-resistant CFTR folding mutants were also robustly rescued, suggesting substantial therapeutic potential for type IV correctors.

Evaluating the efficacy of the selective orexin 1 receptor antagonist nivasorexant in an animal model of binge-eating disorder.

OBJECTIVE: Test the efficacy of the selective orexin 1 receptor (OX1R) antagonist (SO1RA) nivasorexant in an animal model of binge-eating disorder (BED) and study its dose-response relationship considering free brain concentrations and calculated OX1R occupancy. Compare nivasorexant's profile to that of other, structurally diverse SO1RAs. Gain understanding of potential changes in orexin-A (OXA) neuropeptide and deltaFosB (ΔFosB) protein expression possibly underlying the development of the binge-eating phenotype in the rat model used. METHOD: Binge-like eating of highly palatable food (HPF) in rats was induced through priming by intermittent, repeated periods of dieting and access to HPF, followed by an additional challenge with acute stress. Effects of nivasorexant were compared to the SO1RAs ACT-335827 and IDOR-1104-2408. OXA expression in neurons and neuronal fibers as well as ΔFosB and OXA-ΔFosB co-expression was studied in relevant brain regions using immuno- or immunofluorescent histochemistry. RESULTS: All SO1RAs dose-dependently reduced binge-like eating with effect sizes comparable to the positive control topiramate, at unbound drug concentrations selectively blocking brain OX1Rs. Nivasorexant's efficacy was maintained upon chronic dosing and under conditions involving more frequent stress exposure. Priming for binge-like eating or nivasorexant treatment resulted in only minor changes in OXA or ΔFosB expression in few brain areas. DISCUSSION: Selective OX1R blockade reduced binge-like eating in rats. Neither ΔFosB nor OXA expression proved to be a useful classifier for their binge-eating phenotype. The current results formed the basis for a clinical phase II trial in BED, in which nivasorexant was unfortunately not efficacious compared with placebo. PUBLIC SIGNIFICANCE: Nivasorexant is a new investigational drug for the treatment of binge-eating disorder (BED). It underwent clinical testing in a phase II proof of concept trial in humans but was not efficacious compared with placebo. The current manuscript investigated the drug's efficacy in reducing binge-like eating behavior of a highly palatable sweet and fat diet in a rat model of BED, which initially laid the foundation for the clinical trial.

The metabolism of the orexin-1 selective receptor antagonist nivasorexant.

Nivasorexant was the first orexin-1 selective receptor antagonist entering clinical development. Despite encouraging preclinical evidence in animal models, a proof-of-concept trial in binge-eating patients recently failed to demonstrate its clinical utility in this population.Across species, nivasorexant clearance was driven by metabolism along seven distinct pathways, five of which were hydroxylation reactions in various locations of the molecule. The exact sites of metabolism were identified by means of mass spectrometry, the use of deuterated analogues, and finally confirmed by chemical references.CYP3A4 was the main cytochrome P450 enzyme involved in nivasorexant metabolism in vitro and accounting for about 90% of turnover in liver microsomes. Minor roles were taken by CYP2C9 and CYP2C19 but individually did not exceed 3-7%.In the rat, nivasorexant was mostly excreted via the bile after extensive metabolism, while urinary excretion was negligible. Only traces of the parent drug were detected in urine, bile, or faeces.

Discovery of Nivasorexant (ACT-539313): The First Selective Orexin-1 Receptor Antagonist (SO1RA) Investigated in Clinical Trials.

The orexin system consists of two neuropeptides (orexins A and B) and two receptors (OX1 and OX2). Selective OX1 receptor antagonists (SO1RA) are gaining interest for their potential use in the treatment of CNS disorders, including substance abuse, eating, obsessive compulsive, or anxiety disorders. While blocking OX2 reduces wakefulness, the expected advantage of selectively antagonizing OX1 is the ability to achieve clinical efficacy without the promotion of sleep. Herein we report our discovery efforts starting from a dual orexin receptor antagonist and describe a serendipitous finding that triggered a medicinal chemistry program that culminated in the identification of the potent SO1RA ACT-539313. Efficacy in a rat model of schedule-induced polydipsia supported the decision to select the compound as a preclinical candidate. Nivasorexant (20) represents the first SO1RA to enter clinical development and completed a first proof of concept phase II clinical trial in binge eating disorder in 2022.

Discovery of a Novel Orally Active, Selective LPA Receptor Type 1 Antagonist, 4-(4-(2-Isopropylphenyl)-4-((2-methoxy-4-methylphenyl)carbamoyl)piperidin-1-yl)-4-oxobutanoic Acid, with a Distinct Molecular Scaffold.

Lysophosphatidic acid receptor 1 (LPAR1) antagonists show promise as potentially novel antifibrotic treatments. In a human LPAR1 ß-arrestin recruitment-based high-throughput screening campaign, we identified urea 19 as a hit with a LPAR1 IC50 value of 5.0 µM. Hit-to-lead activities revealed that one of the urea nitrogen atoms can be replaced by carbon and establish the corresponding phenylacetic amide as a lead structure for further optimization. Medicinal chemistry efforts led to the discovery of piperidine 18 as a potent and selective LPAR1 antagonist with oral activity in a mouse model of LPA-induced skin vascular leakage. The molecular scaffold of 18 shares no obvious structural similarity with any other LPAR1 antagonist disclosed so far.

Pyrazole derivatives as selective orexin-2 receptor antagonists (2-SORA): synthesis, structure-activity-relationship, and sleep-promoting properties in rats.

Selective orexin 2 receptor antagonists (2-SORA) such as seltorexant (15) are in clinical development for the treatment of insomnia and other conditions such as depression. Herein, we report our structure-activity-relationship (SAR) optimization efforts starting from an HTS hit (1) (N-(1-((5-acetylfuran-2-yl)methyl)-1H-pyrazol-4-yl)-5-(m-tolyl)oxazole-4-carboxamide) that was derived from an unrelated in-house GPCR-agonist program. Medicinal chemistry efforts focused on the optimization of orexin 2 receptor (OX2R) antagonistic activity, stability in liver microsomes, time dependent CYP3A4 inhibition, and aqueous solubility. Compounds were assessed for their brain-penetrating potential in in vivo experiments to select the most promising compounds for our in vivo sleep model. Our lead optimization efforts led to the discovery of the potent, brain penetrating and orally active, 2-SORA (N-(1-(2-(5-methoxy-1H-pyrrolo[3,2-b]pyridin-3-yl)ethyl)-1H-pyrazol-4-yl)-5-(m-tolyl)oxazole-4-carboxamide) 43 with efficacy in a sleep model in rats comparable to 15.

The Quest for the Best Dual Orexin Receptor Antagonist (Daridorexant) for the Treatment of Insomnia Disorders.

Since its discovery in 1998, the orexin system has been of interest to the research community as a potential therapeutic target for the treatment of sleep/wake disorders, stress and anxiety disorders, addiction or eating disorders. It consists of two G protein-coupled receptors, the orexin 1 and orexin 2 receptors, and two neuropeptides with agonistic effects, the orexin A and orexin B peptides. Herein we describe our efforts leading to the identification of a promising set of dual orexin receptor antagonists (DORAs) which subsequently went through physiology-based pharmacokinetic and pharmacodynamic modelling>[1] and finally led to the selection of daridorexant, currently in phase 3 clinical trials for the treatment of insomnia disorders.

From Oxadiazole to Triazole Analogues: Optimization toward a Dual Orexin Receptor Antagonist with Improved in†vivo Efficacy in Dogs.

The orexin system is responsible for regulating the sleep-wake cycle. Suvorexant, a dual orexin receptor antagonist (DORA) is approved by the FDA for the treatment of insomnia disorders. Herein, we report the optimization efforts toward a DORA, where our starting point was (5-methoxy-4-methyl-2-[1,2,3]triazol-2-yl-phenyl)-{(S)-2-[5-(2-trifluoromethoxy-phenyl)-[1,2,4]oxadiazol-3-yl]-pyrrolidin-1-yl}methanone (6), a compound which emerged from our in-house research program. Compound 6 was shown to be a potent, brain-penetrating DORA with in vivo efficacy similar to suvorexant in rats. However, shortcomings from low metabolic stability, high plasma protein binding (PPB), low brain free fraction (fu brain), and low aqueous solubility, were identified and hence, compound 6 was not an ideal candidate for further development. Our optimization efforts addressing the above-mentioned shortcomings resulted in the identification of (4-chloro-2-[1,2,3]triazol-2-yl-phenyl)-{(S)-2-methyl-2-[5-(2-trifluoromethoxy-phenyl)-4H-[1,2,4]triazol-3-yl]-pyrrolidin-1-yl}l-methanone (42), a DORA with improved in vivo efficacy compared to 6.

Oxadiazole Derivatives as Dual Orexin Receptor Antagonists: Synthesis, Structure-Activity Relationships, and Sleep-Promoting Properties in Rats.

The orexin system plays an important role in the regulation of wakefulness. Suvorexant, a dual orexin receptor antagonist (DORA) is approved for the treatment of primary insomnia. Herein, we outline our optimization efforts toward a novel DORA. We started our investigation with rac-[3-(5-chloro-benzooxazol-2-ylamino)piperidin-1-yl]-(5-methyl-2-[1,2,3]triazol-2-ylphenyl)methanone (3), a structural hybrid of suvorexant and a piperidine-containing DORA. During the optimization, we resolved liabilities such as chemical instability, CYP3A4 inhibition, and low brain penetration potential. Furthermore, structural modification of the piperidine scaffold was essential to improve potency at the orexin 2 receptor. This work led to the identification of (5-methoxy-4-methyl-2-[1,2,3]triazol-2-ylphenyl)-{(S)-2-[5-(2-trifluoromethoxyphenyl)-[1,2,4]oxadiazol-3-yl]pyrrolidin-1-yl}methanone (51), a potent, brain-penetrating DORA with in vivo efficacy similar to that of suvorexant in rats.

Discovery of Highly Potent Dual Orexin Receptor Antagonists via a Scaffold-Hopping Approach.

Starting from suvorexant (trade name Belsomra), we successfully identified interesting templates leading to potent dual orexin receptor antagonists (DORAs) via a scaffold-hopping approach. Structure-activity relationship optimization allowed us not only to improve the antagonistic potency on both orexin 1 and orexin 2 receptors (Ox1 and Ox2, respectively), but also to increase metabolic stability in human liver microsomes (HLM), decrease time-dependent inhibition of cytochrome P450 (CYP) 3A4, and decrease P-glycoprotein (Pgp)-mediated efflux. Compound 80 c [{(1S,6R)-3-(6,7-difluoroquinoxalin-2-yl)-3,8-diazabicyclo[4.2.0]octan-8-yl}(4-methyl-[1,1'-biphenyl]-2-yl)methanone] is a potent and selective DORA that inhibits the stimulating effects of orexin peptides OXA and OXB at both Ox1 and Ox2. In calcium-release assays, 80 c was found to exhibit an insurmountable antagonistic profile at both Ox1 and Ox2, while displaying a sleep-promoting effect in rat and dog models, similar to that of the benchmark compound suvorexant.

Substituted pyrrolidin-2-ones: Centrally acting orexin receptor antagonists promoting sleep. Part 2.

Starting from advanced pyrrolidin-2-one lead compounds, this novel series of small-molecule orexin receptor antagonists was further optimized by fine-tuning of the C-3 substitution at the γ-lactam ring. We discuss our design to align in vitro potency with metabolic stability and improved physicochemical/pharmacokinetic properties while avoiding P-glycoprotein-mediated efflux. These investigations led to the identification of the orally active 3-hydroxypyrrolidin-2-one 46, a potent and selective orexin-2 receptor antagonist, that achieved good brain exposure and promoted physiological sleep in rats.

Structure-activity relationship, biological, and pharmacological characterization of the proline sulfonamide ACT-462206: a potent, brain-penetrant dual orexin 1/orexin 2 receptor antagonist.

The orexin system consists of two G-protein-coupled receptors, the orexin 1 and orexin 2 receptors, widely expressed in diverse regions of the brain, and two peptide agonists, orexin A and orexin B, which are produced in a small assembly of neurons in the lateral hypothalamus. The orexin system plays an important role in the maintenance of wakefulness. Several compounds (almorexant, SB-649868, suvorexant) have been in advanced clinical trials for treating primary insomnia. ACT-462206 is a new, potent, and selective dual orexin receptor antagonist (DORA) that inhibits the stimulating effects of the orexin peptides at both the orexin 1 and 2 receptors. It decreases wakefulness and increases non-rapid eye movement (non-REM) and REM sleep while maintaining natural sleep architectures in rat and dog electroencephalography/electromyography (EEG/EMG) experiments. ACT-462206 shows anxiolytic-like properties in rats without affecting cognition and motor function. It is therefore a potential candidate for the treatment of insomnia.

Discovery of substituted lactams as novel dual orexin receptor antagonists. Synthesis, preliminary structure-activity relationship studies and efforts towards improved metabolic stability and pharmacokinetic properties. Part 1.

Starting from a thiazolidin-4-one HTS hit, a novel series of substituted lactams was identified and developed as dual orexin receptor antagonists. In this Letter, we describe our initial efforts towards the improvement of potency and metabolic stability. These investigations delivered optimized lead compounds with CNS drug-like properties suitable for further optimization.

Stereoselective synthesis of 3,4-disubstituted and 3,4,5-trisubstituted piperidines by Lewis acid-catalysed ene cyclisation of 4-aza-1,7-dienes.

The thermal or Lewis acid-catalysed ene cyclisation of a variety of 4-aza-1,7-dienes afforded 3,4-disubstituted or 3,4,5-trisubstituted piperidines. Activation of the enophile with a single ester facilitated a thermal ene cyclisation, although the reaction was not amenable to Lewis acid catalysis. With other activating groups on the enophile it was found that Lewis acid catalysis was facile, although there was a fine balance between the desired ene cyclisation and the competing hetero-Diels-Alder reaction, with the product distribution being influenced by the activating group on the enophile, the nature of the ene component, and the Lewis acid used. Activation of the enophile with an oxazolidinone function facilitated Lewis acid-catalysed cyclisation to afford mixtures of ene and hetero-Diels-Alder products. Activating the enophile with two ester groups gave a substrate that underwent a very facile ene cyclisation catalysed by MeAlCl(2) to give the corresponding trans 3,4-disubstituted piperidines with diastereomeric ratios of >200 : 1.

Synthesis of 3,4-disubstituted piperidines by carbonyl ene and prins cyclizations: switching between kinetic and thermodynamic control with Brønsted and Lewis acid catalysts.

A novel approach to cis and trans 3,4-disubstituted piperidines is described. Carbonyl ene cyclization of aldehydes 4a-e catalyzed by MeAlCl(2) in refluxing chloroform afforded the trans piperidines 7a-e with diastereomeric ratios of up to 93:7, while aldehyde 4f afforded solely the cis product 6f, which was resistant to isomerization to the trans isomer. It was demonstrated for 4a that the cyclization catalyzed by a variety of Lewis acids at low temperature proceeded under kinetic control to afford predominantly the cis piperidine 6a, and this isomerized to the thermodynamically more stable trans piperidine 7a on warming. In contrast, Prins cyclization of 4a-e catalyzed by concentrated hydrochloric acid in CH2Cl2 at low temperature afforded cis piperidines 6a-e with diastereomeric ratios of up to >98:2. The yield and diastereoselectivity of these cyclizations could be improved by using HCl-saturated CH2Cl2 to form the corresponding chloride, followed by elimination of HCl effected by ammonia. Aldehydes 4f and 4galso cyclized in good yield under the latter conditions. Mechanistic studies supported by DFT calculations (B3LYP/6-31G(d)) suggest that the cyclizations proceed via a mechanism with significant carbocationic character, with the cis carbocation being more stable than the trans carbocation. DFT calculations (B3LYP/6-31G(d)) of the transition state energies for concerted cyclization show that the cis piperidine is also the favored product from cyclization through a more concerted mechanism.

Synthesis of 3,4-disubstituted piperidines by carbonyl ene and Prins cyclizations: a switch in diastereoselectivity between Lewis and Brønsted acid catalysts.

[reaction: see text] A novel diastereoselective approach to cis and trans 3,4-disubstituted piperidines is described. Carbonyl ene cyclization of aldehydes 6a-e catalyzed by the Lewis acid methyl aluminum dichloride in refluxing chloroform affords trans piperidines 8a-e with diastereomeric ratios of up to 93:7. By contrast, Prins cyclization of 6a-e catalyzed by hydrochloric acid at low temperatures affords cis products 7a-e with diastereomeric ratios of up to 98:2.