Route to Prolonged Residence Time at the Histamine H1 Receptor: Growing from Desloratadine to Rupatadine.
ABSTRACT: Drug-target binding kinetics are an important predictor of in vivo drug efficacy, yet the relationship between ligand structures and their binding kinetics is often poorly understood. We show that both rupatadine (1) and desloratadine (2) have a long residence time at the histamine H1 receptor (H1R). Through development of a [3H]levocetirizine radiolabel, we find that the residence time of 1 exceeds that of 2 more than 10-fold. This was further explored with 22 synthesized rupatadine and desloratadine analogues. Methylene-linked cycloaliphatic or ?-branched substitutions of desloratadine increase the residence time at the H1R, conveying a longer duration of receptor antagonism. However, cycloaliphatic substituents directly attached to the piperidine amine (i.e., lacking the spacer) have decreased binding affinity and residence time compared to their methylene-linked structural analogues. Guided by docking studies, steric constraints within the binding pocket are hypothesized to explain the observed differences in affinity and binding kinetics between analogues.
Project description:Histamine-1 receptor (H1R) belongs to the family of rhodopsin-like G-protein-coupled receptors expressed in cells that mediates allergies and other pathophysiological diseases. For alleviation of allergic symptoms, H1R antagonists are therapeutic drugs; of which the most frequently prescribed are second generation drugs, such as; Cetirizine, Loratadine, Hydroxyzine, Desloratadine, Bepotastine, Acrivastine and Rupatadine. To understand their potency, binding affinity and interaction; we have employed molecular docking and quantum chemical study such as; Induced-fit docking and calculation of quantum chemical descriptors. This study also introduces the binding site characterization of H1R, with its known antagonists and Curcumin (our proposed alternative H1R antagonist); useful for future drug target site. The interactive binding site residues of H1R are found to be; Lys-191, Tyr-108, Asp-107, Tyr-100, Lys-179, Lys-191, Thr-194, Trp-428, Phe-432, Tyr-458, Hie-450, with most of these shown to be inhibited by naturally-occurring compound curcumin. Amongst the FDA approved drugs, Hydroxyzine showed best ligand binding affinity, calculated as -?141.491 kcal/mol and naturally occurring compound, Curcumin showed binding affinity of -?87.046 kcal/mol. The known antagonists of H1R has been used for hypothesizing curcumin as naturally occurring lead compound for the target using accurate molecular docking simulation study. Though the pharmacological action of known inhibitor is already established, they could differ from their reactivity, which we have also focused in our study for predicting drug reactivity.
Project description:The histamine H1-receptor (H1R) is an important mediator of allergy and inflammation. H1R antagonists have particular clinical utility in allergic rhinitis and urticaria. Here we have developed six novel fluorescent probes for this receptor that are very effective for high resolution confocal imaging, alongside bioluminescence resonance energy transfer approaches to monitor H1R ligand binding kinetics in living cells. The latter technology exploits the opportunities provided by the recently described bright bioluminescent protein NanoLuc when it is fused to the N-terminus of a receptor. Two different pharmacophores (mepyramine or the fragment VUF13816) were used to generate fluorescent H1R antagonists conjugated via peptide linkers to the fluorophore BODIPY630/650. Kinetic properties of the probes showed wide variation, with the VUF13816 analogues having much longer H1R residence times relative to their mepyramine-based counterparts. The kinetics of these fluorescent ligands could also be monitored in membrane preparations providing new opportunities for future drug discovery applications.
Project description:A similar immune response is implicated in the pathogenesis of pulmonary fibrosis and allergic disorders. We investigated the potential therapeutic efficacy and mechanism of rupatadine, a dual antagonist of histamine and platelet-activation factor (PAF), in bleomycin- (BLM-) and silica-induced pulmonary fibrosis. The indicated dosages of rupatadine were administered in rodents with bleomycin or silica-induced pulmonary fibrosis. The tissue injury, fibrosis, inflammatory cells and cytokines, and lung function were examined to evaluate the therapeutic efficacy of rupatadine. The anti-fibrosis effect of rupatadine was compared with an H1 or PAF receptor antagonist, and efforts were made to reveal rupatadine's anti-fibrotic mechanism. Rupatadine promoted the resolution of pulmonary inflammation and fibrosis in a dose-dependent manner, as indicated by the reductions in inflammation score, collagen deposition and epithelial-mesenchymal transformation, and infiltration or expression of inflammatory cells or cytokines in the fibrotic lung tissue. Thus, rupatadine treatment improved the declined lung function and significantly decreased animal death. Moreover, rupatadine was able not only to attenuate silica-induced silicosis but also to produce a superior therapeutic efficacy compared to pirfenidone, histamine H1 antagonist loratadine, or PAF antagonist CV-3988. The anti-fibrotic action of rupatadine might relate to its attenuation of BLM- or PAF-induced premature senescence because rupatadine treatment protected against the in vivo and in vitro activation of the p53/p21-dependent senescence pathway. Our studies indicate that rupatadine promotes the resolution of pulmonary inflammation and fibrosis by attenuating the PAF-mediated senescence response. Rupatadine holds promise as a novel drug to treat the devastating disease of pulmonary fibrosis.
Project description:Currently there are no specific treatments available for acute dengue infection. We considered that rupatadine, a platelet-activating factor receptor inhibitor, might modulate dengue-associated vascular leak. The effects of rupatadine were assessed in vitro, and in a dengue model, which showed that rupatadine significantly reduced endothelial permeability by dengue sera in vitro, and significantly inhibited the increased haematocrit in dengue-infected mice with dose-dependency. We conducted a randomised, placebo-controlled trial in 183 adult patients in Sri Lanka with acute dengue, which showed that rupatadine up to 40?mg daily appeared safe and well-tolerated with similar proportions of adverse events with rupatadine and placebo. Although the primary end-point of a significant reduction in fluid leakage (development of pleural effusions or ascites) was not met, post-hoc analyses revealed small but significant differences in several parameters on individual illness days - higher platelet counts and lower aspartate-aminotransferase levels on day 7 in the rupatadine group compared to the placebo group, and smaller effusions on day 8 in the subgroup of patients with pleural effusions. However, due to the small sample size and range of recruitment time, the potential beneficial effects of rupatadine require further evaluation in large studies focused on recruitment during the early febrile phase.
Project description:Background:Different clinical trials showed the superior efficacy of rupatadine compared to placebo at improving seasonal allergic rhinitis (SAR) symptoms, but no study has assessed if the response promoted is clinically meaningful. Methods:This study is a pooled analysis of data of seven randomized, double-blind, placebo-controlled SAR studies comparing responder proportions upon treatment with rupatadine (10 or 20 mg) or placebo. We evaluated the following symptom scores at baseline (Visit 1) and over 14 days of treatment: Total 4 Nasal Symptom Score (T4NSS), Total 2 Ocular Symptom Score (T2OSS) and Total 6 Symptom Score (T6SS). The proportion of responders (50% and 75% response) and the time to response were compared between groups on days 7 (Visit 2) and 14 (Visit 3). Responder rates were compared between groups on days 7 and 14 for the complete/near-to-complete response for T4NSS (TN4SS score???2 and each symptom score???1) and T6SS (T6SS score???3 and each symptom score???1). Results:Data from 1470 patients were analyzed: 332 treated with placebo, 662 with rupatadine 10 mg and 476 with rupatadine 20 mg. The reduction in T4NSS, T2OSS and T6SS over 14 days of treatment relative to baseline was statistically higher in rupatadine groups vs the placebo group, with greater improvements in the 20 mg group. A statistically higher proportion of patients reached the 50% and 75% response for T4NSS, T2OSS and T6SS in rupatadine groups compared to the placebo group across the visits. Among rupatadine-treated patients, those receiving 20 mg compared favourably for both cut-off responses. The time to achieve a proportion of responders was shorter in the rupatadine 20 mg group than in the rupatadine 10 mg and placebo groups for all the symptom scores. The number of patients who achieved a complete/near-to-complete response for both symptom scores was higher in rupatadine groups than in the placebo group, with higher proportions in the 20 mg group. Conclusions:This responder analysis confirms the superior efficacy of rupatadine vs placebo to treat SAR. Rupatadine promoted higher proportions of responders according to stringent response criteria and in a dose-dependent manner, with faster and higher response rates in the 20 mg group.
Project description:Background:The clinical efficacy of rupatadine in terms of responders has not been previously explored in perennial allergic rhinitis (PAR). Methods:This pooled analysis included data from 6 randomised, double-blind, placebo-controlled trials conducted in PAR patients treated with rupatadine 10 mg or 20 mg, or placebo. Participants were aged???18 years, with diagnosis of PAR and a Total 4 Nasal Symptom Score (T4NSS)???5. We evaluated the T4NSS and Total 5 Symptom Score (T5SS) for 28 days of treatment, the responder proportion (50% and 75% response), and the time to response. Results:Efficacy data from 1486 patients were analysed: 585 received placebo, 682 rupatadine 10 mg, and 219 rupatadine 20 mg. Compared with placebo, rupatadine promoted greater symptom improvements and higher responder proportions (50% and 75% response) for T4NSS and T5SS over 28 days. Symptom improvements and responder proportions were higher in the rupatadine 20 mg group vs the 10 mg group. The time to response was shorter in the rupatadine 20 mg group vs the 10 mg group for T4NSS (16 and 9 days for the 50% and 75% responses, respectively) and for T5SS (13 and 8 days for the 50% and 75% responses, respectively). Conclusions:Rupatadine was efficacious in reducing allergic rhinitis symptoms, showing high responder proportions. The faster and stronger effect of rupatadine 20 mg may suggest its use in patients with severe PAR or not responding to the standard dose.
Project description:BACKGROUND:Schistosomiasis is a socioeconomically devastating parasitic infection afflicting hundreds of millions of people and animals worldwide. It is the most important helminth infection, and its treatment relies solely on the drug praziquantel. Oral H1-antihistamines are available worldwide, and these agents are among the most widely used of all medications in children and adults. Given the importance of the drug repositioning strategy, we evaluated the antischistosomal properties of the H1-antihistamine drugs commonly used in clinical practices. METHODS:Twenty-one antihistamine drugs were initially screened against adult schistosomes ex vivo. Subsequently, we investigated the anthelmintic properties of these antihistamines in a murine model of schistosomiasis for both early and chronic S. mansoni infections at oral dosages of 400 mg/kg single dose or 100 mg/kg daily for five consecutive days. We also demonstrated and described the ability of three antihistamines to induce tegumental damage in schistosomes through the use of scanning electron microscopy. RESULTS:From phenotypic screening, we found that desloratadine, rupatadine, promethazine, and cinnarizine kill adult S. mansoni in vitro at low concentrations (5-15 µM). These results were further supported by scanning electron microscopy analysis. In an animal model, rupatadine and cinnarizine revealed moderate worm burden reductions in mice harboring either early or chronic S. mansoni infection. Egg production, a key mechanism for both transmission and pathogenesis, was also markedly inhibited by rupatadine and cinnarizine, and a significant reduction in hepatomegaly and splenomegaly was recorded. Although less effective, desloratadine also revealed significant activity against the adult and juvenile parasites. CONCLUSIONS:Although the worm burden reductions achieved are all only moderate, comparatively, treatment with any of the three antihistamines is more effective in early infection than praziquantel. On the other hand, the clinical use of H1-antihistamines for the treatment of schistosomiasis is highly unlikely.
Project description:<h4>Introduction</h4>Rupatadine is a marketed second generation antihistamine, with anti-PAF activity, indicated for symptomatic treatment of allergic rhinitis and urticaria. This study was conducted to evaluate the pharmacokinetics (PK), pharmacodynamics (PD), safety and tolerability of rupatadine in healthy Japanese subjects after single and multiple oral doses.<h4>Methods</h4>In this randomised, double-blind, placebo-controlled study, 27 male and female healthy Japanese subjects were administered single and multiple escalating rupatadine dose of 10, 20 and 40 mg or placebo. Blood samples were collected at different time points for PK measurements and subjects were assessed for safety and tolerability. The effect of rupatadine on cognitive functioning was evaluated by means of computerized cognitive tests: rapid visual information processing (RVP), reaction time (RT), spatial working memory (SWM) and visual analogue scales (VAS).<h4>Results</h4>Exposure to rupatadine as measured by Cmax and AUC was found to increase in a dose dependent manner over the dose range of 10-40 mg for both single and multiple dose administration. The safety assessments showed that all treatment related side effects were of mild intensity and there were no serious adverse events (SAEs) or withdrawals due to treatment-emergent adverse events (TEAEs) in this study. The therapeutic dose of rupatadine did not show any CNS impairment in any of the cognitive tests.<h4>Conclusions</h4>This study demonstrated that rupatadine is safe and well tolerated by Japanese healthy subjects. The PK-PD profile confirmed previous experience with rupatadine.
Project description:Chronic spontaneous urticaria (CSU) is a common and hard to treat condition associated with a substantial negative impact on patients' quality of life (QoL). Clinical studies have shown that rupatadine is effective and safe in the treatment of CSU, but data from routine clinical care are scarce. Therefore, we assessed the effectiveness and tolerability of rupatadine in established dosages on CSU activity and patients' QoL in a routine daily practice setting.This was an open, prospective, non-interventional study performed in 146 dermatological practices in Germany. CSU patients for whom treatment with rupatadine was indicated were eligible to participate. Key symptoms of urticaria activity and their impact on patients' QoL were assessed at the beginning and the end of treatment. Adverse events (AEs) and withdrawals, as well as the dosage regimens chosen, were documented. Patients and physicians were requested to rate effectiveness and tolerability of therapy at the final visit. All statistical analyses were descriptive.The majority of the 660 patients screened to be treated (median age 44 years, IQR = 31-59 years, n = 654) received rupatadine 10 mg tablets once (477 patients) or twice (105 patients) daily for a median time of 28 days. After treatment, 93.2% of the patients (606/650) reported a clear overall improvement of symptoms. Rupatadine significantly reduced the urticaria activity score (UAS7) as well as the frequency and severity of existing angioedema episodes. Similarly all domains of the urticaria-specific QoL questionnaire (CU-Q2oL) were markedly improved. The majority of physicians and patients rated rupatadine treatment as effective and well tolerated. There were 39 (5.9%) early treatment withdrawals, and 21 patients (3.2%) experienced AEs.Rupatadine when given according to the routine treating schemes improves symptoms and CU-Q2oL of CSU patients; the drug is also safe and well tolerated.Dr. R. Pfleger GmbH.
Project description:The pharmacodynamics of drug-candidates is often optimized by metrics that describe target binding (Kd or Ki 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.