The expanding role of leukotriene receptor antagonists in chronic asthma

Immune Modulation in Asthma: Current Concepts and Future Strategies

Asthma treatment concepts have profoundly changed over the last 20 years, from standard therapeutic regimens for all patients with asthma towards individually tailored interventions targeting treatable traits ("precision medicine"). A precise and highly effective immune modulation with minimal adverse effects plays a central role in this new concept. Recently, there have been major advances in the treatment of asthma with immune-modulatory compounds. One example is the approval of several highly potent biologics for the treatment of severe asthma. New immune-modulatory strategies are expected to enter clinical practice in the future; these innovations will be especially important for patients with treatment-resistant asthma.

Clinical effectiveness and safety of montelukast in asthma. What are the conclusions from clinical trials and meta-analyses?

Asthma is a common childhood atopic disease associated with chronicity and impaired quality of life. As there is no cure for this disease, treatment relies on avoidance of triggers such as food and aeroallergens, the use of inhaled bronchodilators/corticosteroids and antiallergic or immunomodulating therapies. Inhaled corticosteroids (ICSs) and bronchodilators have been the mainstay. However, in Asia, myths and fallacies regarding Western medicine and corticosteroids are prevalent and lead to nonadherence to treatment. Also, use of traditional and proprietary herbal medicines is popular. In the past decades, a novel class of nonsteroidal immunomodulating montelukasts has become available. This article reviews the evidence for the effectiveness and clinical efficacy of these medications. A number of randomized and controlled trials have been performed over the years. The majority of studies confirm the usefulness of montelukast as monotherapy and add-on therapy to ICS in mild to moderate childhood asthma across all age groups. ICSs are generally superior to montelukasts for asthma management. However, montelukast has a place in the treatment of young children with viral-triggered wheezing diseases, exercise-induced asthma, and in children whose parents are steroid-phobic and find ICS unacceptable.

Fracture healing and lipid mediators

Lipid mediators regulate bone regeneration during fracture healing. Prostaglandins and leukotrienes are well-known lipid mediators that regulate inflammation and are synthesized from the Ω-6 fatty acid, arachidonic acid. Cyclooxygenase (COX-1 or COX-2) and 5-lipoxygenase (5-LO) catalyze the initial enzymatic steps in the synthesis of prostaglandins and leukotrienes, respectively. Inhibition or genetic ablation of COX-2 activity impairs fracture healing in animal models. Genetic ablation of COX-1 does not affect the fracture callus strength in mice, suggesting that COX-2 activity is primarily responsible for regulating fracture healing. Inhibition of cyclooxygenase activity with nonsteroidal anti-inflammatory drugs (NSAIDs) is performed clinically to reduce heterotopic ossification, although clinical evidence that NSAID treatment impairs fracture healing remains controversial. In contrast, inhibition or genetic ablation of 5-LO activity accelerates fracture healing in animal models. Even though prostaglandins and leukotrienes regulate inflammation, loss of COX-2 or 5-LO activity appears to primarily affect chondrogenesis during fracture healing. Prostaglandin or prostaglandin analog treatment, prostaglandin-specific synthase inhibition and prostaglandin or leukotriene receptor antagonism also affect callus chondrogenesis. Unlike the Ω-6-derived lipid mediators, lipid mediators derived from Ω-3 fatty acids, such as resolvin E1 (RvE1), have anti-inflammatory activity. In vivo, RvE1 can inhibit osteoclastogenesis and limit bone resorption. Although Ω-6 and Ω-3 lipid mediators have clear-cut effects on inflammation, the role of these lipid mediators in bone regeneration is more complex, with apparent effects on callus chondrogenesis and bone remodeling.

Effects of add-on montelukast on airway hyperresponsiveness in patients with well-controlled asthma - a pilot study

Objective

Control of airway inflammation is the cornerstone of asthma management. The aim of the present pilot study was to assess the effects of a leukotriene receptor antagonist (LTRA) added to a basic treatment of inhaled corticosteroids (ICS) and long-acting beta-agonist (LABA) on airway hyperresponsiveness, inflammation, and quality of life in well-controlled patients with asthma.

Research design and methods

Seventeen patients (age 18–65, 11 women) with well-controlled asthma presenting airway hyperresponsiveness to mannitol and methacholine challenge were given add-on montelukast on a stable ICS + LABA for 4 weeks. Quality of life and selected parameters of airway inflammation were measured at baseline and at study end. (ClinicalTrials.gov (NCT01725360)).

Results

Adding montelukast to ICS + LABA resulted in an increase in mean FEV₁ (+4.5%, p = 0.057), cumulated higher dose of mannitol (+32.5%, p = 0.023) and methacholine (+17.2%, 0.237) in the provocation test, lower airway reactivity with mannitol and methacholine (response dose ratio (RDR) –50.0%, p = 0.024 and –44.3%, p = 0.006, respectively), and improved airway sensitivity to mannitol and methacholine (+12.1%, p = 0.590 and +48.0%, p = 0.129 for PD15 and PD20 FEV₁, respectively). Changes in inflammation parameters (blood eosinophil count, serum eosinophil cationic protein, and exhaled nitric oxide) were consistent with these findings. Asthma-related quality of life improved significantly in all domains and overall (from 5.3 at baseline to 6.1 at the final visit, p < 0.001). The main limitation was the absence of a control group.

Conclusion

The consistency of the changes in airway hyperresponsiveness and inflammation as well as in quality of life observed with an add-on therapy with montelukast in well-controlled asthma patients during 4 weeks suggests that residual inflammation may represent an area for further improvement of asthma control to be explored in adequately powered randomized controlled trials.

Targeting phosphoinositide 3-kinase γ in airway smooth muscle cells to suppress interleukin-13-induced mouse airway hyperresponsiveness

We recently reported that phosphoinositide 3-kinase γ (PI3Kγ) directly regulates airway smooth muscle (ASM) contraction by modulating Ca(2+) oscillations. Because ASM contraction plays a critical role in airway hyperresponsiveness (AHR) of asthma, the aim of the present study was to determine whether targeting PI3Kγ in ASM cells could suppress AHR in vitro and in vivo. Intranasal administration into mice of interleukin-13 (IL-13; 10 μg per mouse), a key pathophysiologic cytokine in asthma, induced AHR after 48 h, as assessed by invasive tracheostomy. Intranasal administration of a broad-spectrum PI3K inhibitor or a PI3Kγ-specific inhibitor 1 h before AHR assessment attenuated IL-13 effects. Airway responsiveness to bronchoconstrictor agonists was also examined in precision-cut mouse lung slices pretreated without or with IL-13 for 24 h. Acetylcholine and serotonin dose-response curves indicated that IL-13-treated lung slices had a 40 to 50% larger maximal airway constriction compared with controls. Furthermore, acetylcholine induced a larger initial Ca(2+) transient and increased Ca(2+) oscillations in IL-13-treated primary mouse ASM cells compared with control cells, correlating with increased cell contraction. As expected, PI3Kγ inhibitor treatment attenuated IL-13-augmented airway contractility of lung slices and ASM cell contraction. In both control and IL-13-treated ASM cells, small interfering RNA-mediated knockdown of PI3Kγ by 70% only reduced the initial Ca(2+) transient by 20 to 30% but markedly attenuated Ca(2+) oscillations and contractility of ASM cells by 50 to 60%. This report is the first to demonstrate that PI3Kγ in ASM cells is important for IL-13-induced AHR and that acute treatment with a PI3Kγ inhibitor can ameliorate AHR in a murine model of asthma.

Asthma in sickle cell disease: implications for treatment

Objective. To review issues related to asthma in sickle cell disease and management strategies. Data Source. A systematic review of pertinent original research publications, reviews, and editorials was undertaken using MEDLlNE, the Cochrane Library databases, and CINAHL from 1947 to November 2010. Search terms were [asthma] and [sickle cell disease]. Additional publications considered relevant to the sickle cell disease population of patients were identified; search terms included [sickle cell disease] combined with [acetaminophen], [pain medications], [vitamin D], [beta agonists], [exhaled nitric oxide], and [corticosteroids]. Results. The reported prevalence of asthma in children with sickle cell disease varies from 2% to approximately 50%. Having asthma increases the risk for developing acute chest syndrome , death, or painful episodes compared to having sickle cell disease without asthma. Asthma and sickle cell may be linked by impaired nitric oxide regulation, excessive production of leukotrienes, insufficient levels of Vitamin D, and exposure to acetaminophen in early life. Treatment of sickle cell patients includes using commonly prescribed asthma medications; specific considerations are suggested to ensure safety in the sickle cell population. Conclusion. Prospective controlled trials of drug treatment for asthma in patients who have both sickle cell disease and asthma are urgently needed.

Montelukast in the treatment of asthma and beyond

Asthma is a chronic inflammatory disease affecting over 300 million people worldwide. The common association with allergic rhinitis and the presence of proinflammatory cells and mediators in the circulation of patients qualify asthma as a systemic disease. This characteristic and the fact that the gold-standard therapy for persistent asthma, inhaled corticosteroids, cannot suppress all components of airway inflammation and fail to adequately penetrate into the small airways, warrant the quest for effective systemic anti-asthma therapies. This review describes the most important controlled studies of montelukast, a once-daily leukotriene receptor antagonist, in asthma and allergic rhinitis in both adults and children. Montelukast is a systemically active drug with a targeted, dual mechanism of action, acting both as a bronchodilator and anti-inflammatory. In patients of all ages, montelukast has shown a favorable safety profile and was well-tolerated. Both as monotherapy or in combination with inhaled corticosteroids, montelukast produced clinically relevant improvements in asthma-related parameters, including symptoms, lung function parameters, quality of life and the number of asthma exacerbations. Furthermore, bronchoprotective effects have been reported both against specific and nonspecific bronchoactive stimuli. Similarly, in patients with allergic rhinitis, montelukast produced substantial improvements in symptoms and quality of life. Long-term studies aimed to determine its effects on airway remodeling are still lacking.

Add-on montelukast to inhaled corticosteroids protects against excessive airway narrowing

RATIONALE

Excessive airway narrowing in response to broncho-active stimuli is a predictor for severe exacerbations in asthma. Leukotriene receptor antagonists (LTRAs) have complementary properties to inhaled corticosteroids (ICS) on asthma control.

OBJECTIVES

The LTRA montelukast may provide an additional protection against excessive airway narrowing. We tested the add-on effects of montelukast on the maximal response plateau and PD(20) to inhaled methacholine in asthmatics on a stable dose of ICS.

METHODS

Thirty-one patients with allergic asthma [14M/17F, 19-50 years, forced expiratory volume in 1 s (FEV(1)) >70% pred., PD(20) <3.9 micromol methacholine], with a twice documented response plateau to methacholine, were randomized in a double-blind (montelukast 10 mg or matching placebo once daily), 12-week parallel study. Bronchoprovocation tests with methacholine (0.03-256 micromol or > or =40% decline in FEV(1)) were repeated every 4 weeks and after wash-out. The main study objectives were changes from baseline in maximal FEV(1) decline at the response plateau (i.e. >2 post-dose FEV(1) values within 5%) and PD(20) to methacholine after 12 weeks' treatment.

RESULTS

Neither treatment affected baseline FEV(1) (P=0.62). Compared with placebo, montelukast significantly decreased the maximal response plateau to methacholine (mean difference 9.4%; 95% confidence interval 3.9-15.7; P<0.005), improved the FEV(1) decline (mean change in FEV(1) decline was 2.1% [montelukast] and -0.8% [placebo], respectively, P<0.05), and increased PD(20) methacholine (mean change in PD(20) of 5.3 [montelukast] and 1.4 [placebo] doubling doses, respectively, P<0.001).

CONCLUSION

Add-on montelukast to ICS has disease-modifying effects in adults with persistent asthma, and hence reduces the risk of excessive airway narrowing (NCT 00913328).

Leukotriene modifiers in the treatment of asthma in children

Asthma is one of the most common respiratory disorders in clinical practice, affecting up to 13% of people worldwide. Inflammation is the most important component of asthma and inhaled corticosteroids (ICS) are recommended as the first line controller treatment for patients of all ages. Treatment with corticosteroids is often unable to fully control asthma symptoms and progression. Recently, leukotrienes have come to the forefront of research as they have been found play a pivotal role in the airway inflammatory process, and specific drugs have been developed to target them. Cysteiny leukotriene antagonists (LTRAs) have recently emerged as important therapeutic options that show a large potential clinical utility. Three specific LTRAs are licensed for clinical use: montelukast, zafirlukast and pranlukast, although montelukast is the only drug approved in the paediatric age range. It is well tolerated (although adverse effects such as headaches, abdominal pain, rashes, angioedema, pulmonary eosinophilia and arthralgia have been reported) and shows many positive effects in asthmatic patients. Current Global Initiative for Asthma guidelines recommend LTRAs as: (1) a second choice treatment to ICS for patients with mild persistent asthma, (2) an add-on therapy to reduce the dose of ICS in patients with moderate or severe asthma, due to the different and complementary mechanisms of action of these agents. LTRAs may be particularly appropriate choices in a number of clinical situations, including the following: patients with concomitant rhinitis; patients with viral-induced wheeze; patients with exercise-induced bronchoconstriction (EIB) and, in children aged 2-5 years, to reduce the frequency of asthma exacerbations.

Inhaled montelukast inhibits cysteinyl-leukotriene-induced bronchoconstriction in ovalbumin-sensitized guinea-pigs: the potential as a new asthma medication

Oral cysteinyl-leukotriene (LT) receptor antagonists such as montelukast are used for reducing airway inflammation and exacerbations. However, inhaled therapy using LT receptor antagonists has not been studied. In the present study, the effect of inhaled montelukast was investigated on airway hyperresponsiveness measured by cysteinyl-LT induced bronchoconstriction in an animal model of asthma. Bronchoconstriction responses were induced by inhaled LTC4 and LTD4 (0.2 microg/ml each) or three doses of intravenous LTC4 and LTD4 (0.3, 1, 3 microg/kg) in ovalbumin (OVA)-sensitized Hartley male guinea-pigs. The response was measured by the change in peak pressure of airway opening (Pao). The effect of montelukast was evaluated by the comparison of bronchoconstriction responses between the groups of animals pre-treated with 15-min inhalation of 10mg/ml montelukast and saline. To evaluate the tissue injury which might be caused by montelukast inhalation, lung tissues were examined for the histology. The broncoconstriction responses induced by inhaled LTC4 and LTD4 were enhanced by OVA sensitization in the guinea-pigs. In sensitized animals, the significant increases in peak Pao were 18.5+/-2.1 cmH(2)O by LTC4 inhalation and 25.0+/-1.6 cmH(2)O by LTD4 inhalation on average. Prior treatment of inhaled montelukast potently suppressed the peak Pao increases induced by both inhaled and intravenous LTC4 and LTD4 (all P<0.01 vs. saline control). Moreover, the suppression of inhaled montelukast against LTD4-induced bronchoconstriction was observed for at least up to 24h. According to the histological examination, montelukast inhalation produced no injury to the lung tissue. Inhaled montelukast, a cysteinyl-LT receptor antagonist, was effective in inhibiting cysteinyl-LT-induced acute bronchoconstriction, and may have the potential for clinical use as a new asthma drug.

Montelukast and bronchial inflammation in asthma: a randomised, double-blind placebo-controlled trial

BACKGROUND

Examination of bronchoalveolar lavage, induced sputum, and peripheral blood indicate that cysteinyl leukotriene receptor blockers decrease inflammatory cells in asthma but these do not examine airway tissue per se.

OBJECTIVES

Our objective was to determine the effect of montelukast, a leukotriene receptor antagonist, on airway tissue inflammatory cells by direct bronchoscopic examination of the bronchial mucosa.

METHODS

Adult subjects with mild asthma (pre-bronchodilator FEV(1)> or =70% predicted; PC(20) of < or =4 mg/mL) were given 10mg/day oral montelukast (N=38) or placebo (N=37) for 6 weeks. Bronchial mucosal eosinophils and mast cells were identified and counted.

RESULTS

Change from baseline in numbers of biopsy EG2+ ("activated") eosinophils was the primary endpoint; numbers of total (chromotrope 2R+) eosinophils and (tryptase+) mast cells were secondary. Unexpectedly, there were many patients with zero EG2+ eosinophils at baseline. There was a within-group decrease in EG2+ cells, from 13.54 cells/mm (at baseline) to 0.79 cells/mm at 6 weeks in the montelukast group (LS mean change; 95% confidence interval=-13.59 [-25.45, -1.74]cells/mm; P<0.05), a change not observed in the placebo group (-1.17 [-13.26, 10.91]cells/mm; NS). The zero-inflated Poisson statistical model demonstrated that montelukast significantly reduced post-treatment EG2+ cells by 80% compared with placebo (95% CI [70.6-86.8%]; P<0.0001). The data for total eosinophils showed similar changes. The reduction in mast cell numbers was 12% (95% CI [7.9, 16.0]; P<0.0001).

CONCLUSION

Direct examination of airway tissue confirms that montelukast decreases the number of eosinophils and mast cells in asthma.

Prevalence of pharyngeal and laryngeal complications in adult asthmatics using inhaled corticosteroids

OBJECTIVES

To investigate the prevalence in adults of pharyngeal and laryngeal symptoms associated with the use of inhaled corticosteroids.

DESIGN

Prospective, observational and based on a structured, specifically designed postal questionnaire.

SETTING

University Hospital Aintree, Liverpool, UK.

PARTICIPANTS

The questionnaire was distributed to 190 patients on the basis of current inhaled corticosteroid use. Recruitment was from the databases of two local general practices. Individuals were classified as mild, moderate or severe asthmatics, using the guidelines of the British Thoracic Society.

MAIN OUTCOME MEASURES

Demographic data, including smoking history, were recorded. The number, type, strength, dosing regime and duration of individual inhaler use were recorded. Specific pharyngeal and laryngeal side effects were enquired about. Co-morbidities and preventive measures were also recorded. Results were analysed using univariate and multivariate statistical tests.

RESULTS

There was a 75.8 per cent response rate (144/190 questionnaires); 63 (43.8 per cent) of respondents were male and 81 (56.2 per cent) were female. The majority of our patients were either mild or moderate asthmatics. Longer use of an inhaled corticosteroid predisposed to weak voice (p = 0.0016), hoarseness (p = 0.0001) and throat irritation (p = 0.008). Hoarseness, throat irritation, sore throat and cough were observed much more frequently than anticipated. Severe asthmatics were more likely to use a spacer device compliantly (p = 0.0487; odds ratio 1.53). Side effects were more prevalent as asthma severity worsened (p = 0.0049; odds ratio 1.87).

CONCLUSIONS

Inhaled corticosteroids cause sore throats, throat irritation, hoarseness and cough. Further research in this area is required in order to elucidate the mechanism of inflammation. Only then can effective preventive measures be introduced and implemented.

Update on montelukast and its role in the treatment of asthma, allergic rhinitis and exercise-induced bronchoconstriction

Montelukast sodium (Singulair, Merck and Co., Inc., Whitehouse Station, NJ) is a selective and orally-active leukotriene receptor antagonist with demonstrated effectiveness for treating allergic asthma and allergic rhinitis in adults and children as young as 12 months of age for allergic asthma and 6 months of age for allergic rhinitis. It was recently approved in the US for prevention of exercise-induced bronchoconstriction in patients who are > or = 15 years of age. This paper updates a prior review of the data on the clinical efficacy of montelukast published in this journal.

Novel medications for asthma: a look at the future

The principal components of the asthmatic response are airways hyper-responsiveness, persistent inflammation and mucus hypersecretion. Although these components are inter-related, any of these can predominate at different times and for different patients and each requires a different approach to therapy. As a result of the inflammation and epithelial damage, there can be abnormal repair mechanisms leading to fixed airflow obstruction that has been termed 'airways remodeling'. Although there are a number of highly effective therapeutic agents used to treat asthma today, novel therapies are being designed to more specifically and safely target these different components and better meet the needs of patients with asthma.