In vitro characterisation of the duration of action of the histamine-1 receptor antagonist azelastine

Analyzing the clinical efficacy and safety of levocetirizine based on its receptor occupancy, intraclass comparison and role in the treatment of CSU: an AROG consensus statement

INTRODUCTION

Chronic spontaneous urticaria (CSU) is characterized by urticaria persisting for more than 6 weeks. Antihistamines, notably sgAH (second generation antihistamines) are the first line of treatment for CSU.

AREAS COVERED

This consensus aimed to review the existing research on receptor occupancy of antihistamines, including levocetirizine, and translate its implications in the treatment of CSU. The consensus deliberations were under the banner of the Antihistamine Receptor Occupancy Group (AROG) from India, an expert panel of 12 dermatologists with a mix of institutional and practitioner backgrounds. This group analyzed the existing translational research on the receptor occupancy of levocetirizine to establish the clinical efficacy and safety of levocetirizine in the treatment of CSU using the grading of recommendations assessment, development, and evaluation (GRADE) method vis-a-vis the varied SGAH.

EXPERT OPINION

SGAH constitute the first step in the therapeutic ladder for managing CSU. Levocetirizine has high bioavailability, high affinity and occupancy of the H1 receptor, rapid onset of action, limited distribution and minimal hepatic metabolism. It exhibits significant anti-inflammatory effects at clinically relevant concentrations. The marked receptor occupancy translates to enhanced efficacy as compared to similarly dosed SGAH with the lower cost making it an appropriate drug for chronic use. Receptor occupancy should be the basis of intra-class head-to-head trials in CSU.

Insights of different analytical approaches for estimation of budesonide as COVID-19 replication inhibitor in its novel combinations: green assessment with AGREE and GAPI approaches

Simple, direct, rapid, and sensitive HPLC and spectrophotometric methods were established for simultaneous estimation of a novel combination of budesonide and azelastine (BUD/AZL) in their laboratory-prepared mixture and dosage form according to the medicinally recommended ratio 1:4.28. Budesonide is an important inhalation corticosteroid that plays a vital role in the inhibition of COVID-19 replication and cytokine production. The first chromatographic method was created for the simultaneous estimation of BUD epimers in the presence of AZL with excellent efficiency in a relatively short chromatographic run (< 9 min). The separation of BUD epimers with AZL was carried out on a C₁₈ column using acetonitrile: phosphate buffer of pH 3.5 adjusted by 0.2 M orthophosphoric acid (40:60, v/v) as a mobile phase, UV detection at 230 nm and a flow rate of regulated at 2 mL/min. Besides, three spectrophotometric methods were applied for the simultaneous determination of the provided mixture adopting zero order, first order derivative, and ratio first derivative approaches. The Zero-order spectrophotometry was used for the determination of AZL in presence of BUD, where BUD shows no absorbance at 290 nm. The first derivative amplitude at 265 nm (¹D₂₆₅) (zero-crossing of AZL) and the ratio of first derivative amplitudes at 270 nm (¹DD₂₇₀) using 10.0 µg mL^-1 AZL as divisor was chosen for the simultaneous determination of BUD in the presence of AZL in the binary mixture. The proposed methods were found to be rectilinear in the concentration range of (0.4-40.0 µg mL^-1) and (0.05-40.0 µg mL^-1) for BUD and AZL, respectively in the HPLC method. Whereas the concentration range for AZL in the zero-order method was (1.0-35.0 µg mL^-1) and for BUD in the first derivative and ratio derivative method was (6.0-20.0 µg mL^-1). Validation of the suggested approaches according to the ICH criteria was performed. Furthermore, to ensure the proposed approaches' greenness, The AGREE and GAPI metrics were utilized, and the afforded results revealed an excellent greenness of the proposed approaches.

Chitosan-centered nanosystems as sustained therapeutics for allergic rhinitis intervention: Inhibition of histamine-induced cascades

Allergic rhinitis (AR), histamine-mediated upper airway inflammatory disorder, is characterized by sneezing, itching, airway hyperreactivity, etc. Though it is clinically well-managed by non-invasive inhaled antihistamines, for example, ketotifen (KT, histamine release inhibitor) and cetirizine (CTZ, histamine receptor antagonist), inherent defects of short mucosal in situ retention, frequent administration resulting in irritation to mucosa, and lack of target-specific sequential release of dual drug systems which have been proven to be more effective are inevitable, urging for alternative therapeutic strategies. Recent advances in nanotechnology may be pivotal to generating muco-adhesive nanosystems, which is desirable to prolong local retention, reduce dosing frequency and relieve mucosal irritation. In this regard, KT incorporated and CTZ decorated hydroxybutyl chitosan nanoparticles (K ⊂ CH NPs) were fabricated as nasal adaptive sequential release dual drug system for long-term AR therapy. Nasal adaptive morphology transformation and two-step payload release up to 72 h were achieved in vitro, with ~ 3-fold higher bio-adhesivity over free drugs appeared. K ⊂ CH NPs accomplished longer histamine release inhibition (~ 24 h) and histamine H₁ receptor antagonism (~ 6 h), compared with free KT&CTZ of ~ 12 h and ~ 2 h, respectively. The nanosystems provided comparable anti-allergic effect to free antihistamines via successive intranasal dropping in AR rat, while encouragingly, significantly (P < 0.05) better therapeutic efficacy at reduced treatment frequency (every 4 days) and dose (half-dose). Therefore, the outcomes establish K ⊂ CH NPs as effective low-dose and long-interval administered nanosystems to ameliorate histamine-mediated AR inflammation, which could in principal find extensive utilizations in respiratory allergy intervention.

Molecular Determinants of the Kinetic Binding Properties of Antihistamines at the Histamine H1 Receptors

The binding affinity of ligands for their receptors is determined by their kinetic and thermodynamic binding properties. Kinetic analyses of the rate constants of association and dissociation (k_on and k_off, respectively) of antihistamines have suggested that second-generation antihistamines have a long duration of action owing to the long residence time (1/k_off) at the H₁ receptors. In this study, we examined the relationship between the kinetic and thermodynamic binding properties of antihistamines, followed by an evaluation of the structural determinants responsible for their kinetic binding properties using quantitative structure-activity relationship (QSAR) analyses. We found that whereas the binding enthalpy and entropy might contribute to the increase and decrease, respectively, in the k_off values, there was no significant relationship with the k_on values. QSAR analyses indicated that k_on and k_off values could be determined by the descriptors FASA_H (water-accessible surface area of all hydrophobic atoms divided by total water-accessible surface area) and vsurf_CW2 (a 3D molecular field descriptor weighted by capacity factor 2, the ratio of the hydrophilic surface to the total molecular surface), respectively. These findings provide further insight into the mechanisms by which the kinetic binding properties of antihistamines are regulated by their thermodynamic binding forces and physicochemical properties.

Maraviroc, celastrol and azelastine alter Chlamydia trachomatis development in HeLa cells

Introduction . Chlamydia trachomatis (Ct) is an obligate intracellular bacterium, causing a range of diseases in humans. Interactions between chlamydiae and antibiotics have been extensively studied in the past.Hypothesis/Gap statement: Chlamydial interactions with non-antibiotic drugs have received less attention and warrant further investigations. We hypothesized that selected cytokine inhibitors would alter Ct growth characteristics in HeLa cells.Aim. To investigate potential interactions between selected cytokine inhibitors and Ct development in vitro.Methodology. The CCR5 receptor antagonist maraviroc (Mara; clinically used as HIV treatment), the triterpenoid celastrol (Cel; used in traditional Chinese medicine) and the histamine H1 receptor antagonist azelastine (Az; clinically used to treat allergic rhinitis and conjunctivitis) were used in a genital in vitro model of Ct serovar E infecting human adenocarcinoma cells (HeLa).Results. Initial analyses revealed no cytotoxicity of Mara up to 20 µM, Cel up to 1 µM and Az up to 20 µM. Mara exposure (1, 5, 10 and 20 µM) elicited a reduction of chlamydial inclusion numbers, while 10 µM reduced chlamydial infectivity. Cel 1 µM, as well as 10 and 20 µM Az, reduced chlamydial inclusion size, number and infectivity. Morphological immunofluorescence and ultrastructural analysis indicated that exposure to 20 µM Az disrupted chlamydial inclusion structure. Immunofluorescence evaluation of Cel-incubated inclusions showed reduced inclusion sizes whilst Mara incubation had no effect on inclusion morphology. Recovery assays demonstrated incomplete recovery of chlamydial infectivity and formation of structures resembling typical chlamydial inclusions upon Az removal.Conclusion. These observations indicate that distinct mechanisms might be involved in potential interactions of the drugs evaluated herein and highlight the need for continued investigation of the interaction of commonly used drugs with Chlamydia and its host.

Probe dependency in the determination of ligand binding kinetics at a prototypical G protein-coupled receptor

Drug-target binding kinetics are suggested to be important parameters for the prediction of in vivo drug-efficacy. For G protein-coupled receptors (GPCRs), the binding kinetics of ligands are typically determined using association binding experiments in competition with radiolabelled probes, followed by analysis with the widely used competitive binding kinetics theory developed by Motulsky and Mahan. Despite this, the influence of the radioligand binding kinetics on the kinetic parameters derived for the ligands tested is often overlooked. To address this, binding rate constants for a series of histamine H₁ receptor (H₁R) antagonists were determined using radioligands with either slow (low k_off) or fast (high k_off) dissociation characteristics. A correlation was observed between the probe-specific datasets for the kinetic binding affinities, association rate constants and dissociation rate constants. However, the magnitude and accuracy of the binding rate constant-values was highly dependent on the used radioligand probe. Further analysis using recently developed fluorescent binding methods corroborates the finding that the Motulsky-Mahan methodology is limited by the employed assay conditions. The presented data suggest that kinetic parameters of GPCR ligands depend largely on the characteristics of the probe used and results should therefore be viewed within the experimental context and limitations of the applied methodology.

The long duration of action of the second generation antihistamine bilastine coincides with its long residence time at the histamine H1 receptor

Drug-target binding kinetics has recently attracted considerable interest in view of the potential predictive power for in vivo drug efficacy. The recently introduced antihistamine bilastine has a long duration of in vivo drug action, which outlasts pharmacological active bilastine concentrations in blood. To provide a molecular basis for the long duration of action, we explored the kinetics of bilastine binding to the human histamine H₁ receptor using [³H]mepyramine binding studies and compared its pharmacodynamics properties to the reference compounds fexofenadine and diphenhydramine, which have a long (60 ± 20 min) and short (0.41 ± 0.1 min) residence time, respectively. Bilastine shows a long drug-target residence time at the H₁ receptor (73 ± 5 min) and this results in a prolonged H₁ receptor antagonism in vitro (Ca²⁺ mobilization in Fluo-4 loaded HeLa cells), following a washout of unbound antagonist. Hence, the long residence time of bilastine can explain the observed long duration of drug action in vivo.

The Target Residence Time of Antihistamines Determines Their Antagonism of the G Protein-Coupled Histamine H1 Receptor

The pharmacodynamics of drug-candidates is often optimized by metrics that describe target binding (K_d or K_i value) or target modulation (IC₅₀). However, these metrics are determined at equilibrium conditions, and consequently information regarding the onset and offset of target engagement and modulation is lost. Drug-target residence time is a measure for the lifetime of the drug-target complex, which has recently been receiving considerable interest, as target residence time is shown to have prognostic value for the in vivo efficacy of several drugs. In this study, we have investigated the relation between the increased residence time of antihistamines at the histamine H₁ receptor (H₁R) and the duration of effective target-inhibition by these antagonists. Hela cells, endogenously expressing low levels of the H₁R, were incubated with a series of antihistamines and dissociation was initiated by washing away the unbound antihistamines. Using a calcium-sensitive fluorescent dye and a label free, dynamic mass redistribution based assay, functional recovery of the H₁R responsiveness was measured by stimulating the cells with histamine over time, and the recovery was quantified as the receptor recovery time. Using these assays, we determined that the receptor recovery time for a set of antihistamines differed more than 40-fold and was highly correlated to their H₁R residence times, as determined with competitive radioligand binding experiments to the H₁R in a cell homogenate. Thus, the receptor recovery time is proposed as a cell-based and physiologically relevant metric for the lead optimization of G protein-coupled receptor antagonists, like the H₁R antagonists. Both, label-free or real-time, classical signaling assays allow an efficient and physiologically relevant determination of kinetic properties of drug molecules.

Interactions between histamine H1 receptor and its antagonists by using cell membrane chromatography method

Objectives

A high histamine H1 receptor (H1R) expression cell membrane chromatography (CMC) method was developed to investigate the affinity of ligands for H1R.

Methods

The affinity of ligands for H1R was evaluated by frontal analysis. Competition studies and molecular docking study were utilized to study the interactions that occurred at specific binding sites on H1R.

Key findings

The KD values measured by frontal analysis were (8.72 ± 0.21) × 10−7 M for azelastine, (9.12 ± 0.26) × 10−7 M for cyproheptadine, (9.90 ± 0.18) × 10−7 M for doxepin, (1.42 ± 0.13) × 10−6 M for astemizole, (2.25 ± 0.36) × 10−6 M for chlorpheniramine and (3.10 ± 0.27) × 10−6 M for diphenhydramine. The results had a positive correlation with those from radioligand binding assay. The ability of displacement order measured on the binding sites occupied by doxepin was doxepin (KD, (2.95 ± 0.21) × 10−8 M) &gt; astemizole (KD, (5.03 ± 0.18) × 10−7 M) &gt; chlorpheniramine (KD, (1.27 ± 0.16) × 10−6 M) &gt; cyproheptadine (KD, (1.61 ± 0.27) × 10−6 M), whose order met with the scores by molecular docking study.

Conclusions

The studies showed CMC could be applied to investigate drug–receptor interactions.

A four-way, double-blind, randomized, placebo controlled study to determine the efficacy and speed of azelastine nasal spray, versus loratadine, and cetirizine in adult subjects with allergen-induced seasonal allergic rhinitis

Background

Azelastine has been shown to be effective against seasonal allergic rhinitis (SAR). The Environmental Exposure Unit (EEU) is a validated model of experimental SAR. The objective of this double-blind, four-way crossover study was to evaluate the onset of action of azelastine nasal spray, versus the oral antihistamines loratadine 10 mg and cetirizine 10 mg in the relief of the symptoms of SAR.

Methods

70 participants, aged 18-65, were randomized to receive azelastine nasal spray, cetirizine, loratadine, or placebo after controlled ragweed pollen exposure in the EEU. Symptoms were evaluated using the total nasal symptom score (TNSS). The primary efficacy parameter was the onset of action as measured by the change from baseline in TNSS.

Results

Azelastine displayed a statistically significant improvement in TNSS compared with placebo at all time points from 15 minutes through 6 hours post dose. Azelastine, cetirizine, and loratadine reduced TNSS compared to placebo with an onset of action of 15 (p < 0.001), 60 (p = 0.015), and 75 (p = 0.034) minutes, respectively. The overall assessment of efficacy was rated as good or very good by 46% of the participants for azelastine, 51% of the participants for cetirizine, and 30% of the participants for loratadine compared to 18% of the participants for placebo.

Conclusions

Azelastine’s onset of action for symptom relief was faster than that of cetirizine and loratadine. The overall participant satisfaction in treatment with azelastine is comparable to cetirizine and statistically superior to loratadine. These results suggest that azelastine may be preferential to oral antihistamines for the rapid relief of SAR symptoms.