Selective Histamine Research Articles

Highly selective and sensitive histamine and tryptamine analysis using SiO2@AuNPs@PDA molecularly imprinted polymer coupled with SALDI–TOF MS

A combination of SiO2@AuNPs@PDA molecularly imprinted and surface-assisted laser desorption/ionization–time-of-flight mass spectrometry (SALDI–TOF MS) was devised as a method for highly specific and ultrasensitive detection of two biogenic amines—histamine (HIS) and tryptamine (TRP)—in real samples. In this strategy, AuNPs modified amino-abundant silica nanospheres (SiO2@AuNPs). The prepared SiO2@AuNPs were used as a substrate to synthesize a molecularly imprinted polymer (MIP) through in situ dopamine self-polymerization with HIS and TRP as the template molecules (SiO2@AuNP@PDA-MIP). The as-prepared MIP structure, properties, and target-analyte identification conditions were characterized and optimized and it was used as the matrix for MS. Compared to the case of nonimprinted materials, the imprinting function endowed the matrix with a higher selectivity for capturing the target molecules. The enriched analytes were directly and rapidly identified using SALDI–TOF MS without elution. Meanwhile, the proposed method has low background interference, good reproducibility and stability, high salt tolerance, and satisfactory linearity (R2 > 0.99), and it enables ultrasensitive detection of HIS and TRP (limits of detection for HIS and TRP were 0.2 and 0.1 ng mL−1, respectively). Moreover, the proposed method was applied to analyze samples of real beer, sausage, and chicken, and the results agreed with those obtained via liquid chromatography–MS, suggesting that the method has excellent practical applications in the field of food safety.

Development of fluorescence chemo sensor for selective histamine determination in spiked human plasma samples

Histamine is crucial for controlling a variety of physiological processes and its dysregulation is linked to various pathological conditions, including allergic disorders, autoimmune diseases and inflammatory conditions. Herein, a novel fluorescence chemo sensor was produced to measure histamine in the pure form and spiked human plasma matrix. The proposed method is based on chemical transformation of histamine into a fluorescent product, N-(2-(1H-imidazol-4-yl) ethyl)-2-bromoacetamide, exhibiting unique fluorescence properties compared to non-fluorescent histamine molecule. This transformation occurs through a sequence of chemical reactions involving the interaction of histamine with trimethylamine, resulting in the formation of a nucleophilic intermediate that subsequently reacts with electrophilic bromoacetyl bromide. The transformed fluorescent product demonstrates an emission at 340 nm after being excited at 250 nm. Significant concentration-dependent fluorescence enhancement was obtained enabling histamine determination. The procedures were examined for accuracy, precision, selectivity, and robustness in line with the ICH M10 recommendations. The method exhibits a lower limit of quantification at 0.25 ng/mL and dynamic detection throughout a linearity range of 1–200 ng/mL, providing accurate assessment of histamine in the plasma matrix.

Validation and Greenness assessment of UPLC Method for bioanalysis of Bilastine in mice PK study

Bilastine, is a second-generation antihistamine drug which is used in the treatment of allergic rhinoconjunctivitis and urticaria. It exerts its effect as a selective histamine H1 receptor antagonist. In this study, an ultra-high-performance liquid chromatography (UPLC) method was developed to measure the concentrations of Bilastine in mouse blood, and the method was applied in measuring the pharmacokinetics of the analyte after oral and intravenous administration. The analyte was extracted by solid phase extraction method. A UPLC BEH C18 column (2.1 mm × 100 mm, 1.8 ?m particle size) was used for chromatographic separation by gradient elution using acetonitrile-water (0.1% formic acid) as the mobile phase at a flow rate of 0.4 mL/min. Bilastine was administered to the mice orally at 2 mg/kg and intravenously at 0.05 mg/kg. Blood was collected at various time intervals, and the blood samples were processed after collection and analyzed by UPLC. The intra-day and inter-day accuracy of Bilastine were 91%-103% and 85%-107%, respectively, and the precision (RSD, %) was less than 15% for both intra-day and inter-day measurements. The matrix effect ranged from 95% to 108%, and the recovery was higher than 70%. The half-life of bilastine in plasma was found to be 7.02 ± 5.21h. Bilastine has a good linear relationship in the range of 10-500 ng/mL, and the lower limit of quantification was 10 ng/mL. The precision, accuracy, extraction recovery, matrix effect, and stability meet the requirements of the guiding principles. A robust and reliable UPLC method was fully optimized and developed to detect the blood concentration of bilastine in mice and the samples were analyzed by Empower software.

The Potent and Selective Histamine H3 Receptor Antagonist E169 Counteracts Cognitive Deficits and Mitigates Disturbances in the PI3K/AKT/GSK-3β Signaling Pathway in MK801-Induced Amnesia in Mice.

The role of histamine H3 receptors (H3Rs) in memory and the prospective of H3R antagonists in pharmacological control of neurodegenerative disorders, e.g., Alzheimer's disease (AD), is well-accepted. Therefore, the procognitive effects of acute systemic administration of H3R antagonist E169 (2.5-10 mg/kg, i.p.) on MK801-induced amnesia in C57BL/6J mice using the novel object recognition test (NORT) were evaluated. E169 (5 mg) provided a significant memory-improving effect on MK801-induced short- and long-term memory impairments in NORT. The E169 (5 mg)-provided effects were comparable to those observed with the reference phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 and were abrogated with the H3R agonist (R)-α-methylhistamine (RAMH). Additionally, our results demonstrate that E169 ameliorated MK801-induced memory deficits by antagonism of H3Rs and by modulation of the level of disturbance in the expression of PI3K, Akt, and GSK-3β proteins, signifying that E169 mitigated the Akt-mTOR signaling pathway in the hippocampus of tested mice. Moreover, the results observed revealed that E169 (2.5-10 mg/kg, i.p.) did not alter anxiety levels and locomotor activity of animals in open field tests, demonstrating that performances improved following acute systemic administration with E169 in NORT are unrelated to changes in emotional response or in spontaneous locomotor activity. In summary, these obtained results suggest the potential of H3R antagonists such as E169, with good in silico physicochemical properties and stable retained key interactions in docking studies at H3R, in simultaneously modulating disturbed brain neurotransmitters and the imbalanced Akt-mTOR signaling pathway related to neurodegenerative disorders, e.g., AD.

Preparation and Optimization of Fexofenadine HCl Solid lipid Nanoparticles

Solid lipid nanoparticles (SLNs) are introduced as an efficient carrier method for correcting dynamic medicine and water-soluble medication. Fexofenadine HCl is a long-acting selective histamine (H1) receptor antagonist with anti-inflammatory properties of the second generation. Allergic rhinitis, angioedema, and chronic urticaria are treated with fexofenadine HCl. Solid lipid nanoparticles were prepared by hot homogenization method using a solid lipid of and different polymers. A solid lipid nanoparticle created by drug and polymer poloxamer 188 in ratio showed highest entrapment efficiency as well as drug release of the medication from the solid lipid nanoparticle formulation. The prepared nanoparticles were used to formulate the nanogel using Carbopol 934. The nano-drug delivery system developed by the hot homogenization method has demonstrated their suitability for a topical route for the treatment of skin allergy. Thus, the studies revealed that the developed system has a great appeal for the convenient treatment of dermatological allergy that may overcome in improving the limitations of the existing drug delivery system. Fexofenadine HCl is a white colored powder. It is practically insoluble in water and soluble in methanol. The melting point was found to be 194.1-195.2. The FTIR spectra of Fexofenadine HCl and the mixture of drug and excipients used in the formulation of nanoparticles reveal that there was no significant interaction between the drug and polymer and other excipients used in the formulation. The optimized batches (F2) showed highest entrapment efficiency. It was observed that as there is increase in concentration of surfactant increases the entrapment efficiency. The optimized solid lipid nanoparticle formulation showed maximum drug release within 6 hr. This showed that the increase in the concentration of surfactant there was increase in drug release from the SLN.

Histamine H1- and H4-receptor expression in human colon-derived cell lines

In previous studies, we demonstrated the involvement of H4R in inflammatory bowel disease (IBD) and IBD-associated colon cancer in mice and could ascribe H4R-mediated histamine function to colon epithelial cells. The transferability of obtained data to humans is however lacking. Functional expression of H4R on colon epithelial cells is a prerequisite to pursue the hypothesis of involvement of H4R in carcinogenesis. Thus, we here compared the expression of histamine receptor subtypes in a series of cell lines. Out of these, three colon-derived cell lines displaying different combinations of H1R and H4R expression were submitted to functional analyses. Human hematopoietic HMC-1, HL-60, and U937, lung-derived A549 and Calu-3, and colorectal LoVo, SW 480, Caco-2, HT-29, and HCT116 cells were included in the study. mRNA expression was quantified by RT-qPCR. For functional analyses, Caco-2, HT-29, and HCT116 cells were treated by incubation with 1 – 10 µM histamine in the presence or absence of selective histamine receptor antagonists. Calcium mobilization, cAMP accumulation, and cell proliferation were measured by fluorimetry, mass spectrometry, and real-time bioimpedance measurements, respectively. Histamine receptor expression was heterogeneous in the cell lines tested. In most cell lines, we detected H1R mRNA while H4R mRNAs were found only occasionally. The colon-derived epithelial cell lines LoVo, SW480, and HT-29 expressed H1R mRNA exclusively, while in HCT116 cells H1R and H4R mRNAs and in CaCo-2 H2R mRNA were detectable. Subsequent functional analyses in HT29, Caco-2, and HCT116 cells, however, indicated that only HT-29 responded to histamine stimulation, by means of H1R. For a detailed analysis of histamine receptor function, esp. that of H1R and H4R, in human colon-derived cell lines, the cell lines tested here are not fully convenient unless genetically modified.

Effect of famotidine on cognitive and behavioral dysfunctions induced in post-COVID-19 infection: A randomized, double-blind, and placebo-controlled study

ObjectivesThis is an investigation of the efficacy and safety of famotidine, a selective histamine H2 receptor antagonist, on improvement of cognitive impairment, depression and anxiety symptoms developing post-COVID-19, in a 12-week, randomized controlled trial. MethodsA total of 50 patients with a confirmed diagnosis of COVID-19 and a score ≤ 23 on the Mini-Mental State Examination (MMSE) test or a score ≤ 22 on the Montreal Cognitive Assessment (MoCA) were randomly assigned to either the famotidine (40 mg twice daily) or the placebo group. Changes in MMSE scores at weeks 6 and 12 were the primary outcome, while changes in other scales were the secondary outcomes. Participants and evaluators were blinded. ResultsAt weeks 6 and 12, patients in the famotidine group had significantly higher MMSE scores (p = 0.014, p < 0.001, respectively). Regarding the MoCA scale, the famotidine group had a significantly higher score at weeks 6 and 12 (p = 0.001, p < 0.001, respectively). Considering the HAM-D scale (Hamilton Depression Rating Scale), at weeks 6 and 12, the famotidine group experienced a larger reduction (p = 0.009, p = 0.02, respectively). Additionally, comparison of the HAM-A scale scores (Hamilton Anxiety Rating Scale) at weeks 6 and 12 showed a statistically significant larger reduction in the famotidine group (p = 0.04, p = 0.02, respectively). The two groups did not differ in the frequency of adverse effects. ConclusionOur study supports safety and efficacy of famotidine in treating cognitive impairment, depression and anxiety symptoms induced by COVID-19. Trial registrationThis trial was registered at the Iranian registry of clinical trials (IRCT: www.irct.ir; registration number: IRCT20090117001556N138).

0609 Samelisant, Histamine 3 Receptor Agonist for the Potential Treatment of Excessive Daytime Sleepiness in Patients with Narcolepsy

Abstract Introduction Samelisant (SUVN-G3031) is a potent and selective histamine 3 receptor inverse agonist. In orexin knockout mice, samelisant produced wake-promoting and anticataplectic effects suggesting its potential therapeutic utility in the treatment of narcolepsy. Safety and tolerability studies in animals and healthy human volunteers suggested a favorable risk/benefit profile for samelisant. Methods Samelisant is currently being evaluated in a double blind, Phase-2 proof of concept study in USA and Canada for narcolepsy with or without cataplexy (ClinicalTrials.gov Identifier: NCT04072380). The study is recruiting subjects diagnosed with narcolepsy as per ICSD-3 criteria, aged between 18 to 65 years with an Epworth Sleepiness Scale (ESS) score of ≥12 and mean Maintenance of Wakefulness Test (MWT) time of &amp;lt; 12 min. A total of 171 subjects are expected to be randomized into 3 treatment arms (placebo, samelisant 2 mg and samelisant 4 mg) in 1:1:1 ratio. Each subject will receive either placebo or study drug once daily for 2 weeks. The primary efficacy endpoint is change in MWT score from baseline to week 2. Key secondary endpoint is change in ESS from baseline to week 2. Safety will be monitored throughout the study by medical monitor and by data safety monitoring committee. As the study is still recruiting, demographics and baseline characteristic data for the currently enrolled subjects is summarized descriptively. Since the study is blinded, a breakdown of baseline characteristics by treatment group will not be available until after completion. Results At the data cutoff date of Nov 30, 2022, a total of 155 subjects were randomized in the study. The median age of subjects was 30 years (range: 18-57 years) with mean BMI of 28.5 kg/m2 (range: 18.3- 43.9 kg/m2). Overall, 57% subjects were of narcolepsy type-1, 71% were female and 71% were Caucasian. Mean (SD) baseline values of MWT and ESS scores were 6.1 (4.4) and 17.2 (2.8), respectively. Conclusion Baseline characteristics are consistent with the general narcolepsy population. The study is currently enrolling subjects with narcolepsy and the data readout is expected in Q2 2023. Support (if any)

0909 Pitolisant Pregnancy Registry: An Observational Study of the Safety of Pitolisant Exposure in Pregnant Women and Their Offspring

Abstract Introduction WAKIX (pitolisant) is a potent and highly selective histamine 3 receptor antagonist/inverse agonist approved for the treatment of excessive daytime sleepiness or cataplexy in adult patients with narcolepsy. The safety of pitolisant in pregnant women has not been established. Available case reports from clinical trials and postmarketing experience have not demonstrated a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes. The registry is a prospective, observational cohort study designed to evaluate the association between pitolisant exposure during pregnancy and subsequent maternal, fetal, and infant outcomes. Methods The primary study population consists of 3 cohorts: pregnant women with a diagnosis of narcolepsy who are exposed to pitolisant during pregnancy, pregnant women with narcolepsy who are unexposed to pitolisant but exposed to comparator products during pregnancy, and pregnant women with narcolepsy who are neither exposed to pitolisant nor comparator products. Comparator products include modafinil, armodafinil, sodium oxybate, oxybate mixed salts, solriamfetol, methylphenidate, and amphetamines. Outcomes of interest include major congenital malformation (primary outcome), minor congenital malformation, pre-eclampsia, eclampsia, spontaneous abortion, stillbirth, elective termination, small for gestational age, preterm birth, postnatal growth deficiency, and infant developmental deficiency. Data are collected from enrolled pregnant women and healthcare providers involved in their care or the care of their infants, if applicable. Only data that are routinely documented in patients' medical records during usual care are collected. Participation in the registry is voluntary and participants may withdraw their consent to participate at any time. The registry design follows current FDA guidance for designing and implementing pregnancy exposure registries. Results The registry was initiated in May 2021. Presently, data are insufficient to assess an association between pitolisant exposure and any endpoint of interest. Study completion is planned in 2030. Conclusion Healthcare providers are encouraged to discuss this voluntary pregnancy registry with their eligible patients and assist women who are interested in enrolling. The study is registered on Clinicaltrials.gov (ID# NCT05536011). Support (if any) This study is sponsored by Harmony Biosciences LLC.

Is obstructive sleep apnea a circadian rhythm disorder?

Obstructive sleep apnea is the most common sleep-related breathing disorder worldwide and remains underdiagnosed. Its multiple associated comorbidities contribute to a decreased quality of life and work performance as well as an increased risk of death. Standard treatment seems to have limited effects on cardiovascular and metabolic aspects of the disease, emphasising the need for early diagnosis and additional therapeutic approaches. Recent evidence suggests that the dysregulation of circadian rhythms, processes with endogenous rhythmicity that are adjusted to the environment through various cues, is involved in the pathogenesis of comorbidities. In patients with obstructive sleep apnea, altered circadian gene expression patterns have been demonstrated. Obstructive respiratory events may promote circadian dysregulation through the effects of sleep disturbance and intermittent hypoxia, with subsequent inflammation and disruption of neural and hormonal homeostasis. In this review, current knowledge on obstructive sleep apnea, circadian rhythm regulation, and circadian rhythm sleep disorders is summarised. Studies that connect obstructive sleep apnea to circadian rhythm abnormalities are critically evaluated. Furthermore, pathogenetic mechanisms that may underlie this association, most notably hypoxia signalling, are presented. A bidirectional relationship between obstructive sleep apnea and circadian rhythm dysregulation is proposed. Approaching obstructive sleep apnea as a circadian rhythm disorder may prove beneficial for the development of new, personalised diagnostic, therapeutic and prognostic tools. However, further studies are needed before the clinical approach to obstructive sleep apnea includes targeting the circadian system.

Safety and efficacy of pitolisant in children aged 6 years or older with narcolepsy with or without cataplexy: a double-blind, randomised, placebo-controlled trial

Narcolepsy is a life-long disorder characterised by excessive daytime sleepiness and cataplexy, often arising in childhood or adolescence. Pitolisant, a selective histamine H3 receptor inverse agonist, has been approved in Europe and USA for adults with narcolepsy with or without cataplexy, with a favourable safety profile. This phase 3 study aimed to assess the safety and efficacy of pitolisant in children with narcolepsy with or without cataplexy. For this double-blind, randomised, placebo-controlled, multisite study, we recruited patients aged 6-17 years with narcolepsy with or without cataplexy in 11 sleep centres in five countries (Italy, France, Netherlands, Russia, and Finland). Participants were required to have a Pediatric Daytime Sleepiness Scale score of 15 or greater and to have not received psychostimulants for at least 14 days before enrolment; participants who needed anticataplectics (including sodium oxybate) were required to have been on a stable dose for at least 1 month. Participants were randomly assigned to treatment with pitolisant or placebo in a 2:1 ratio at the end of screening. Randomisation was stratified by study centre and treatment was allocated using an interactive web response system. After a 4-week screening period including a 2-week baseline period, patients entered in a 4-week individual up-titration scheme from 5 mg a day to a maximum of 40 mg a day of pitolisant or placebo; treatment was administered at a stable dose for 4 weeks, followed by a 1-week placebo period. For the primary analysis, we assessed pitolisant versus placebo using change in the Ullanlinna Narcolepsy Scale (UNS) total score from baseline to the end of double-blind period in the full analysis set, defined as all randomly allocated patients who received at least one dose of treatment and who had at least one baseline UNS value. A decrease in the UNS total score reflects a reduction in both excessive daytime sleepiness and cataplexy. All adverse events were assessed in the safety population, defined as all participants who took at least one dose of study medication. An open-label follow-up is ongoing. This study is registered at ClinicalTrials.gov, NCT02611687. Between June 6, 2016, and April 3, 2021, we screened 115 participants and 110 were randomly assigned (mean age 12·9 [SD 3·0] years, 61 [55%] male, and 90 [82%] with cataplexy; 72 assigned to pitolisant and 38 to placebo); 107 (70 receiving pitolisant and 37 receiving placebo) completed the double-blind period. The mean adjusted difference in UNS total score from baseline to the end of the double-blind period was -6·3 (SE 1·1) in the pitolisant group and -2·6 (1·4) in the placebo group (least squares mean difference -3·7; 95% CI -6·4 to -1·0, p=0·007). Treatment-emergent adverse events were reported in 22 (31%) of 72 patients in the pitolisant group and 13 (34%) of 38 patients in the placebo group. The most frequently reported adverse events (affecting ≥5% of patients) in either group were headache (14 [19%] in the pitolisant group and three [8%] in the placebo group) and insomnia (five [7%] in the pitolisant group and one [3%] in the placebo group). Pitolisant treatment resulted in an improvement in narcolepsy symptoms in children, although the UNS was not validated for use in children with narcolepsy when our study began. The safety profile was similar to that reported in adults but further studies are needed to confirm long-term safety. Bioprojet.

Green Solvents for Eco-Friendly Synthesis of Dimethindene: A Forward-Looking Approach.

Dimethindene is a selective histamine H1 antagonist and is commercially available as a racemate. Upon analyzing the synthetic pathways currently available for the industrial preparation of dimethindene, we set up a sustainable approach for the synthesis of this drug, switching from petroleum-based volatile organic compounds (VOCs) to eco-friendly solvents, such as 2-methyltetrahydrofuran (2-MeTHF) and cyclopentyl methyl ether (CPME) belonging to classes 3 and 2, respectively. Beyond decreasing the environmental impact of the synthesis (E-factor: 24.1-54.9 with VOCs; 12.2-22.1 with 2-MeTHF or CPME), this switch also improved the overall yield of the process (from 10% with VOCs to 21-22% with 2-MeTHF or CPME) and remarkably simplified the manual operations, working under milder conditions. Typical metrics applied at the first and second pass, according to the CHEM21 metrics toolkit, were also calculated for the whole synthetic procedure of dimethindene, and the results were compared with those of the classical procedure.

Aggressive Systemic Mastocytosis with a Relatively Non-aggressive Course

Background: Mastocytosis is a heterogeneous group of disorders that is characterized by excessive proliferation and pathologic accumulation of mast cells in various body tissues. The mast cells also have abnormal morphology and aberrant expression of surface receptors. Clinical Description: A 4-year-old boy was brought with a history of generalized skin lesions since birth and abdominal distension for 3 years. The diagnosis had not been established to date. General physical examination revealed severe acute malnutrition, pallor, dental staining, facial hypertrichosis, polymorphous skin lesions (cicatricial alopecia, diffuse erythema, multiple plaques of variable diameter, skin-colored nodules, and hypertrophic irregular scars), and positive Darier's sign. He also had hepatosplenomegaly. The differentials considered were congenital erythropoietic porphyria, systemic mastocytosis (SM), multifocal Langerhans cell histiocytosis, and linear immunoglobulin A bullous dermatosis. The presence of mast cells on skin biopsy and elevated serum tryptase levels led us to suspect SM and perform bone marrow studies. The diagnosis of “aggressive” SM was initially made on the application of the diagnostic criteria but revised to “smoldering” SM with the emergence of Vitamin B12 deficiency as the probable cause of pancytopenia. Management: Management was planned by a multidisciplinary team: pediatrician, dermatologist, and hematopathologist. The parents were counseled about the nature, natural history, treatment options, and prognosis of the disorder. The child was provided with nutritional rehabilitation and medication for the cutaneous symptoms (selective histamine H1 receptor inverse agonist, H2-receptor antagonist, and application of topical tacrolimus and calamine lotion). Conclusion: The prognosis varies according to subtype. Careful correlation of clinical and laboratory investigations is required when applying the diagnostic criteria for staging.

Selective histamine H2 receptor agonists alleviate blood-brain barrier disruption by promoting the expression of vascular protective factors following traumatic brain injury in mice

Histamine is a major neurotransmitter and alleviates neuronal damage after ischemic injury via H2 receptors. Herein, we investigated the effects of H2 receptor agonists on the blood-brain barrier (BBB) disruption after traumatic brain injury (TBI). Male ddY mice were used to generate the TBI model, in which a fluid percussion injury (FPI) was induced by a hydraulic impact. The BBB disruption was evaluated using Evans blue extravasation. H2 receptor agonists, amthamine and dimaprit, were administered into the lateral cerebroventricle (i.c.v.) or tail vein (i.v.) from 3 hours to 3 days after FPI. The i.c.v. or i.v. administration of amthamine and dimaprit reduced FPI-induced Evans blue extravasation and promoted mRNA expression of vascular protective factors, including angiopoietin-1 and sonic hedgehog. The co-administration of ranitidine, a H2 receptor antagonist, inhibited these effects. Expression of the H2 receptor was observed in astrocytes and brain microvascular endothelial cells (BMECs) in the injured cortex. Treatment with amthamine and dimaprit promoted mRNA expression of vascular protective factors in astrocytes and BMECs. These results suggest that H2 receptor agonists alleviate TBI-induced BBB disruption by increasing the expression of vascular protective factors in astrocytes and BMECs.

Bilastine - Novel anti histamine drug for allergic rhinitis

The immune system is a fundamental part of human protection against infection and disease.The immune system can occasionally lead to unfavourable reactions in the host which are known as hypersensitivity reactions. The exaggerated immune reactivity (hypersensitivity) to certain environmental substances (allergens) like airborne pollens, dust, mites, pet dander, and reactions to certain foods that normally have little effect on most people is known as allergy. The incidence of allergic disease like allergic rhinitis (AR), food borne allergy, asthma and anaphylactic reactions are prevalent in 25% of populations predominately in adolescents and adults in industrialised countries. Bilastine is a novel second-generation non-sedative, highly selective histamine H1 receptor antagonist that suppresses some allergic inflammatory processes that inhibits the release of histamine from mast cells and is approved in the treatment allergic rhinitis, urticaria and pruritus associated with skin diseases. This review covers the safety, efficacy and pharmacological aspects of Bilastine as an important product for treatment of allergic rhinitis.

Votucalis, a Novel Centrally Sparing Histamine-Binding Protein, Attenuates Histaminergic Itch and Neuropathic Pain in Mice.

Votucalis is a biologically active protein in tick (R. appendiculatus) saliva, which specifically binds histamine with high affinity and, therefore, has the potential to inhibit the host’s immunological responses at the feeding site. We hypothesized that scavenging of peripherally released endogenous histamine by Votucalis results in both anti-itch and anti-nociceptive effects. To test this hypothesis, adult male mice were subjected to histaminergic itch, as well as peripheral nerve injury that resulted in neuropathic pain. Thus, we selected models where peripherally released histamine was shown to be a key regulator. In these models, the animals received systemic (intraperitoneal, i.p.) or peripheral transdermal (subcutaneous, s.c. or intraplantar, i.pl.) administrations of Votucalis and itch behavior, as well as mechanical and thermal hypersensitivity, were evaluated. Selective histamine receptor antagonists were used to determine the involvement of histamine receptors in the effects produced by Votucalis. We also used the spontaneous object recognition test to confirm the centrally sparing properties of Votucalis. Our main finding shows that in histamine-dependent itch and neuropathic pain models peripheral (s.c. or i.pl.) administration of Votucalis displayed a longer duration of action for a lower dose range, when compared with Votucalis systemic (i.p.) effects. Stronger anti-itch effect was observed after co-administration of Votucalis (s.c.) and antagonists that inhibited peripheral histamine H1 and H2 receptors as well as central histamine H4 receptors indicating the importance of these histamine receptors in itch. In neuropathic mice, Votucalis produced a potent and complete anti-nociceptive effect on mechanical hypersensitivity, while thermal (heat) hypersensitivity was largely unaffected. Overall, our findings further emphasize the key role for histamine in the regulation of histaminergic itch and chronic neuropathic pain. Given the effectiveness of Votucalis after peripheral transdermal administration, with a lack of central effects, we provide here the first evidence that scavenging of peripherally released histamine by Votucalis may represent a novel therapeutically effective and safe long-term strategy for the management of these refractory health conditions.

Pharmacokinetic Modeling of [11C]GSK-189254, PET Tracer Targeting H3 Receptors, in Rat Brain.

The histamine H3 receptor has been considered as a target for the treatment of various central nervous system diseases. Positron emission tomography (PET) studies with the radiolabeled potent and selective histamine H3 receptor antagonist [11C]GSK-189254 in rodents could be used to examine the mechanisms of action of novel therapeutic drugs or to assess changes of regional H3 receptor density in animal models of neurodegenerative disease. [11C]GSK-189254 was intravenously administered to healthy Wistar rats (n = 10), and a 60 min dynamic PET scan was carried out. Arterial blood samples were obtained during the scan to generate a metabolite-corrected plasma input function. PET data were analyzed using a one-tissue compartment model (1T2k), irreversible (2T3k) or reversible two-tissue compartment models (2T4k), graphical analysis (Logan and Patlak), reference tissue models (SRTM and SRTM2), and standard uptake values (SUVs). The Akaike information criterion and the standard error of the estimated parameters were used to select the most optimal quantification method. This study demonstrated that the 2T4k model with a fixed blood volume fraction and Logan graphical analysis can best describe the kinetics of [11C]GSK-189254 in the rat brain. SUV40–60 and the reference tissue-based measurements DVR(2T4k), BPND(SRTM), and SUV ratio could also be used as a simplified method to estimate H3 receptor availability in case blood sampling is not feasible.

A Selective Histamine H4 Receptor Antagonist, JNJ7777120, Role on glutamate Transporter Activity in Chronic Depression

Glutamate release and reuptake play a key role in the pathophysiology of depression. glutamatergic nerves in the hippocampus region are modulated by histaminergic afferents. Excessive accumulation of glutamate in the synaptic area causes degeneration of neuron cells. The H4 receptor is defined as the main immune system histamine receptor with a pro-inflammatory role. To understand the role of this receptor, the drug JNJ7777120 was used to reveal the chronic depression-glutamate relationship. We have important findings showing that the H4 antagonist increases the glutamate transporters’ instantaneous activity. In our experiment, it has been shown that blocking the H4 receptor leads to increased neuron cell viability and improvement in behavioral ability due to glutamate. Therefore, JNJ can be used to prevent neurotoxicity, inhibit membrane phospholipase activation and free radical formation, and minimize membrane disruption. In line with our findings, results have been obtained that indicate that JNJ will contribute to the effective prevention and treatment of depression.

Convergent cross-species pro-cognitive effects of RGH-235, a new potent and selective histamine H3 receptor antagonist/inverse agonist

The histamine H3 receptor is a favourable target for the treatment of cognitive deficits. Here we report the in vitro and in vivo profile of RGH-235, a new potent, selective, and orally active H3 receptor antagonist/inverse agonist developed by Gedeon Richter Plc. Radioligand binding and functional assays were used for in vitro profiling. Procognitive efficacy was investigated in rodent cognitive tests, in models of attention deficit hyperactive disorder (ADHD) and in cognitive tests of high translational value (rat touch screen visual discrimination test, primate fixed-foreperiod visual reaction time task). Results were supported by pharmacokinetic studies, neurotransmitter release, sleep EEG and dipsogenia. RGH-235 displayed high affinity to H3 receptors (Ki = 3.0–9.2 nM, depending on species), without affinity to H1, H2 or H4 receptors and >100 other targets. RGH-235 was an inverse agonist ([35S] GTPγS binding) and antagonist (pERK1/2 ELISA), showing favourable kinetics, inhibition of the imetit-induced dipsogenia and moderate effects on sleep-wake EEG. RGH-235 stimulated neurotransmitter release both in vitro and in vivo. RGH-235 was active in spontaneously hypertensive rats (SHR), generally considered as a model of ADHD, and revealed a robust pro-cognitive profile both in rodent and primate tests (in 0.3–1 mg/kg) and in models of high translational value (e.g. in a rodent touch screen test and in non-human primates). The multiple and convergent procognitive effects of RGH-235 support the view that beneficial cognitive effects can be linked to antagonism/inverse agonism of H3 receptors.

Clinical Impact of Pitolisant on Excessive Daytime Sleepiness and Cataplexy in Adults With Narcolepsy: An Analysis of Randomized Placebo-Controlled Trials.

BackgroundPitolisant, a selective histamine 3 receptor antagonist/inverse agonist, is indicated for the treatment of excessive daytime sleepiness or cataplexy in adults with narcolepsy. The efficacy and safety of pitolisant have been demonstrated in randomized placebo-controlled trials. When evaluating the results of randomized placebo-controlled trials, the clinical impact of a treatment can be assessed using effect size metrics that include Cohen’s d (the standardized mean difference of an effect) and number needed to treat (NNT; number of patients that need to be treated to achieve a specific outcome for one person).ObjectiveThe objective of this study was to evaluate the clinical impact of pitolisant for the reduction in excessive daytime sleepiness or cataplexy in adults with narcolepsy.MethodsThis post hoc analysis incorporated data from two 7-week or 8-week randomized placebo-controlled trials (HARMONY 1, HARMONY CTP). Study medication was individually titrated, with a maximum possible pitolisant dose of 35.6 mg/day. Efficacy was assessed using the Epworth Sleepiness Scale (ESS) and weekly rate of cataplexy (HARMONY CTP only). Cohen’s d was derived from the least-squares mean difference between treatment groups (pitolisant vs placebo), and NNTs were calculated from response rates. Treatment response was defined for excessive daytime sleepiness in two ways: (a) reduction in ESS score ≥ 3 or final ESS score ≤ 10 and (b) final ESS score ≤ 10. Treatment response was defined for cataplexy as a ≥ 25%, ≥ 50%, or ≥ 75% reduction in weekly rate of cataplexy.ResultsThe analysis population included 61 patients in HARMONY 1 (pitolisant, n = 31; placebo, n = 30) and 105 patients in HARMONY CTP (pitolisant, n = 54; placebo, n = 51). For pitolisant vs placebo, Cohen’s d effect size values were 0.61 (HARMONY 1) and 0.86 (HARMONY CTP) based on changes in ESS scores, and 0.86 (HARMONY CTP) based on changes in weekly rate of cataplexy. NNTs for pitolisant were 3–5 for the treatment of excessive daytime sleepiness and 3–4 for the treatment of cataplexy.ConclusionsThe results of this analysis demonstrate the robust efficacy of pitolisant for the reduction in both excessive daytime sleepiness and cataplexy. These large effect sizes and low NNTs provide further evidence supporting the strength of the clinical response to pitolisant in the treatment of adults with narcolepsy.Clinical Trial RegistrationClinicalTrials.gov identifiers: NCT01067222 (February 2010), NCT01800045 (February 2013).