Revisit ligand-receptor interaction at the human vasopressin V2 receptor: A kinetic perspective

Seven-membered N-heterocycles as approved drugs and promising leads in medicinal chemistry as well as the metal-free domino access to their scaffolds

Azepanes or azepines are structural motifs of many drugs, drug candidates and evaluated lead compounds. Even though compounds having N-heterocyclic 7-membered rings are often found in nature (e.g. alkaloids), the natural compounds of this group are rather rare as approved therapeutics. Thus, recently studied and approved azepane or azepine-congeners predominantly consist of semi-synthetically or synthetically-obtained scaffolds. In this review a comparison of approved drugs and recently investigated leads was proposed taking into regard their structural aspects (stereochemistry), biological activities, pharmacokinetic properties and confirmed molecular targets. The 7-membered N-heterocycles reveal a wide range of biological activities, not only against CNS diseases, but also as e.g. antibacterial, anticancer, antiviral, antiparasitic and against allergy agents. As most of the approved or investigated potential drugs or lead structures, belonging to 7-membered N-heterocycles, are synthetic scaffolds, this report also reveals different and efficient metal-free cascade approaches useful to synthesize both simple azepane or azepine-containing congeners and those of oligocyclic structures. Stereochemistry of azepane/azepine fused systems, in view of biological data and binding with the targets, is discussed. Apart from the approved drugs, we compare advances in SAR studies of 7-membered N-heterocycles (mainly from 2018 to 2023), whereas the related synthetic part concerning various domino strategies is focused on the last ten years.

Benzothiazole derivatives as histone deacetylase inhibitors for the treatment of autosomal dominant polycystic kidney disease

Recent evidence suggests that histone deacetylases (HDACs) are important regulators of autosomal dominant polycystic kidney disease (ADPKD). In the present study, a series of benzothiazole-bearing compounds were designed and synthesized as potential HDAC inhibitors. Given the multiple participation of HDACs in ADPKD cyst progression, we embarked on a targeted screen using HeLa nuclear extracts to identify potent pan-HDAC inhibitors. Compound 26 emerged as the most efficacious candidate. Subsequent pharmacological characterization showed that compound 26 effectively inhibits several HDACs, notably HDAC1, HDAC2, and HDAC6 (IC50 < 150 nM), displaying a particularly high sensitivity towards HDAC6 (IC50 = 11 nM). The selected compound significantly prevented cyst formation and expansion in an in vitro cyst model and was efficacious in reducing cyst growth in both an embryonic kidney cyst model and an in vivo ADPKD mouse model. Our results provided compelling evidence that compound 26 represents a new HDAC inhibitor for the treatment of ADPKD.

Long-Residence Time Peptide Antagonist for the Vasopressin V2 Receptor to Treat Autosomal Dominant Polycystic Kidney Disease

The dysregulated intracellular cAMP in the kidneys drives cystogenesis and progression in autosomal dominant polycystic kidney disease (ADPKD). Mounting evidence supports that vasopressin V2 receptor (V2R) antagonism effectively reduces cAMP levels, validating this receptor as a therapeutic target. Tolvaptan, an FDA-approved V2R antagonist, shows limitations in its clinical efficacy for ADPKD treatment. Therefore, the pursuit of better-in-class V2R antagonists with an improved efficacy remains pressing. Herein, we synthesized a set of peptide V2R antagonists. Peptide 33 exhibited a high binding affinity for the V2R (Ki = 6.1 ± 1.5 nM) and an extended residence time of 20 ± 1 min, 2-fold that of tolvaptan. This prolonged interaction translated into sustained suppression of cAMP production in washout experiments. Furthermore, peptide 33 exhibited improved efficacies over tolvaptan in both ex vivo and in vivo models of ADPKD, underscoring its potential as a promising lead compound for the treatment of ADPKD.

Target immobilization on glass microfiber membranes as a label-free strategy for hit identification

The discovery of novel chemical entities targeting G protein-coupled receptors (GPCRs) is usually guided by their receptor affinity. However, traditional affinity assay methods and hit identification procedures are usually laborious and expensive. In this work, the type-2 vasopressin receptor (V2R) was chosen as a prototypical GPCR. Membrane fragments from cells highly expressing SNAP-V2R were immobilized on the surface of a glass microfiber (GMF) coated with O6-benzylguanine (BG). This was achieved by transferring the benzyl group of BG to the active site of the SNAP-tag through a nucleophilic substitution reaction. As a result, a biofilm called SNAP-V2R@GMF-BG was produced that showed good specificity and stability. The adsorption ratio for each V2R ligand treated with SNAP-V2R@GMF-BG was determined by HPLC and exhibited a good linear correlation with the Ki value determined by displacement assays. Furthermore, a Ki prediction assay was performed by comparing the data with that generated by a homogeneous time-resolved fluorescence (HTRF) assay. SNAP-V2R@GMF-BG was also used to screen hit compounds from natural products. After SNAP-V2R@GMF-BG was incubated with the total extract, the ligand that binds to V2R could be separated and subjected to LC‒MS analysis for identification. Baicalein was screened from Clerodendranthus spicatus and verified as a potential V2R antagonist. This V2R-immobilized GMF platform can help determine the affinity of V2R-binding hit compounds and screen the compounds efficiently and accurately.

Structure-Affinity and Structure-Kinetic Relationship Studies of Benzodiazepine Derivatives for the Development of Efficacious Vasopressin V2 Receptor Antagonists

Vasopressin V₂ receptors (V₂R) are a promising drug target for autosomal dominant polycystic kidney disease (ADPKD). As previous research demonstrated that the residence time of V₂R antagonists is critical to their efficacy in both ex vivo and in vivo models of ADPKD, we performed extensive structure-kinetic relationship (SKR) analyses on a series of benzodiazepine derivatives. We found that subtle structural modifications of the benzodiazepine derivatives dramatically changed their binding kinetics but not their affinity. Compound 18 exhibited a residence time of 77 min, which was 7.7-fold longer than that of the reference compound tolvaptan (TVP). Accordingly, compound 18 exhibited higher efficacy compared to TVP in an in vivo model of ADPKD. Overall, our study exemplifies a kinetics-directed medicinal chemistry effort for the development of efficacious V₂R antagonists. We envision that this strategy may also have general applicability in other therapeutic areas.

Optical-Controlled Kinetic Switch: Fine-Tuning of the Residence Time of an Antagonist Binding to the Vasopressin V2 Receptor in In Vitro, Ex Vivo, and In Vivo Models of ADPKD

The pharmacological activity of a small-molecule ligand is linked to its receptor residence time. Therefore, precise control of the duration for which a ligand binds to its receptor is highly desirable. Herein, we designed photoswitchable ligands targeting the vasopressin V₂ receptor (V₂R), a validated target for autosomal dominant polycystic kidney disease (ADPKD). We adapted the photoswitching trait of azobenzene to the parent V₂R antagonist lixivaptan (LP) to generate azobenzene lixivaptan derivatives (aLPs). Among them, aLPs-5g was a potential optical-controlled kinetic switch. Upon irradiation, cis-aLPs-5g displayed a 4.3-fold prolonged V₂R residence time compared to its thermally stable trans configuration. The optical-controlled kinetic variations led to distinct inhibitory effects on cellular functional readout. Furthermore, conversion of the cis/trans isomer of aLPs-5g resulted in different efficacies of inhibiting renal cystogenesis ex vivo and in vivo. Overall, aLPs-5g represents a photoswitch for precise control of ligand-receptor residence time and, consequently, the pharmacological activity.

Benzodiazepine Derivatives as Potent Vasopressin V2 Receptor Antagonists for the Treatment of Autosomal Dominant Kidney Disease

Cyst formation and enlargement in autosomal dominant kidney disease (ADPKD) is mainly driven by aberrantly increased cytosolic cAMP in renal tubule epithelial cells. Because the vasopressin V₂ receptor (V₂R) regulates intracellular cAMP levels in kidneys, a series of benzodiazepine derivatives were developed targeting the V₂R. Among these derivatives, compound 25 exhibited potent binding affinity to the V₂R (K_i = 9.0 ± 1.5 nM) and efficacious cAMP inhibition (IC₅₀ = 9.2 ± 3.0 nM). This led to the suppression of cyst formation and growth in both an MDCK cell model and an embryonic kidney cyst model. Further advancing compound 25 in a murine model of ADPKD demonstrated a significantly improved in vivo efficacy compared with the reference compound tolvaptan. Overall, compound 25 holds therapeutic potential for the treatment of ADPKD.

Long Residence Time at the Vasopressin V2 Receptor Translates into Superior Inhibitory Effects in Ex Vivo and In Vivo Models of Autosomal Dominant Polycystic Kidney Disease

Prevailing strategies directing early-phase drug discovery heavily rely on equilibrium-based metrics such as affinity, which overlooks the kinetic process of a drug molecule interacting with its target. Herein, we developed a number of vasopressin V₂ receptor (V₂R) antagonists with divergent binding affinities and kinetics for autosomal dominant polycystic kidney disease (ADPKD). Surprisingly, the residence time of the V₂R antagonists, but not their affinity, was correlated with the efficacy in both ex vivo and in vivo models of ADPKD. We envision that the kinetics-directed drug candidate selection and development may have general applicability for ADPKD and other therapeutic areas as well.

In Vitro and In Silico Analysis of the Residence Time of Serotonin 5-HT7 Receptor Ligands with Arylpiperazine Structure: A Structure-Kinetics Relationship Study

During the last decade, the kinetics of drug-target interaction has received increasing attention as an important pharmacological parameter in the drug development process. Several studies have suggested that the lipophilicity of a molecule can play an important role. To date, this aspect has been studied for several G protein-coupled receptors (GPCRs) ligands but not for the 5-HT₇ receptor (5-HT₇R), a GPCR proposed as a valid therapeutic target in neurodevelopmental and neuropsychiatric disorders associated with abnormal neuronal connectivity. In this study, we report on structure-kinetics relationships of a set of arylpiperazine-based 5-HT₇R ligands. We found that it is not the overall lipophilicity of the molecule that influences drug-target interaction kinetics but rather the position of polar groups within the molecule. Next, we performed a combination of molecular docking studies and molecular dynamics simulations to gain insights into structure-kinetics relationships. These studies did not suggest specific contact patterns between the ligands and the receptor-binding site as determinants for compounds kinetics. Finally, we compared the abilities of two 5-HT₇R agonists with similar receptor-binding affinities and different residence times to stimulate the 5-HT₇R-mediated neurite outgrowth in mouse neuronal primary cultures and found that the compounds induced the effect with different timing. This study provides the first insights into the binding kinetics of arylpiperazine-based 5-HT₇R ligands that can be helpful to design new 5-HT₇R ligands with fine-tuning of the kinetic profile.