Leukotriene antagonists and symptom control in chronic persistent asthma

Asthma and COPD: A Focus on β-Agonists - Past, Present and Future

Asthma has been recognised as a respiratory disorder for millennia and the focus of targeted drug development for the last 120 years. Asthma is one of the most common chronic non-communicable diseases worldwide. Chronic obstructive pulmonary disease (COPD), a leading cause of morbidity and mortality worldwide, is caused by exposure to tobacco smoke and other noxious particles and exerts a substantial economic and social burden. This chapter reviews the development of the treatments of asthma and COPD particularly focussing on the β-agonists, from the isolation of adrenaline, through the development of generations of short- and long-acting β-agonists. It reviews asthma death epidemics, considers the intrinsic efficacy of clinical compounds, and charts the improvement in selectivity and duration of action that has led to our current medications. Important β2-agonist compounds no longer used are considered, including some with additional properties, and how the different pharmacological properties of current β2-agonists underpin their different places in treatment guidelines. Finally, it concludes with a look forward to future developments that could improve the β-agonists still further, including extending their availability to areas of the world with less readily accessible healthcare.

Role of leukotriene receptor antagonists in the management of pediatric asthma: an update

At present, the main indications for leukotriene receptor antagonists (LTRA) in pediatric asthma are as add-on therapy to inhaled corticosteroids (ICS) and as initial controller therapy in children with mild asthma, especially those who cannot or will not use ICS. LTRA are also useful for patients who have concomitant rhinitis, and patients with viral-induced wheeze and exercise-induced asthma. It should be noted that the benefits of LTRA therapy have been demonstrated in children as young as 6 months of age and recent clinical trials have further proven the benefits of LTRA in acute asthma exacerbations. However, considering the important pro-inflammatory effects that leukotrienes (LT) have in experimental models of asthma, it may seem surprising that LTRA treatment outcomes are not better and that in some clinical trials only a minority of patients could be classified as full responders. This could be explained by potential additional LT receptors that are not affected by LTRA. Such receptors could represent new therapeutic targets in asthma. Furthermore, progress in differentiating between asthma phenotypes that result from different pathogenic mechanisms, some of which may involve LT to a lesser degree, should lead to an improved, personalized use of LTRA for treating asthma.

Safety of a depigmented, polymerized vaccine for the treatment of allergic rhinoconjunctivitis and allergic asthma

BACKGROUND

Clinical efficacy of specific immunotherapy (SIT) with depigmented, polymerized allergen extracts is well documented in placebo-controlled trials, and safety data are encouraging although further data are required.

METHODS

We enrolled 768 patients (51% men; mean age, 31 years) in this prospective multicenter study on safety and clinical effects of Depigoid (Laboratorios LETI, S.L., Madrid, Spain). Immunotherapy consisted of four injections of increasing doses of Depigoid at weekly intervals followed by monthly maintenance injections. All adverse events were documented. Moreover, nose, eye, and lung symptoms were assessed at baseline after 3 and 6 months. Results were compared with the scores of the preceding season.

RESULTS

Rates for local and systemic reactions that might possibly be related to the study medication were 2.36 and 4.56/1000 injections, respectively. With 5923 injections given, 14 local reactions were reported (5 patients), and 27 systemic reactions were reported, including 20 of grade 1 (6 patients) and 7 of grade 2 (4 patients). The best safety profile was seen for patients vaccinated against house-dust mites. Reductions in nose, eye, and lung symptoms as well as in concomitant medication compared with either the preceding season (pollen-sensitized patients) or the baseline (house-dust mite-sensitized patients) were observed at the end of study.

CONCLUSION

In this large multicenter study on 768 patients with allergic rhinoconjunctivitis and allergic asthma under daily practice conditions SIT with Depigoid was well tolerated with low rates of local and systemic reactions. Furthermore, SIT resulted in considerable reductions in symptoms and concomitant medication.

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.

Treating asthma: is there a place for leukotriene receptor antagonists?

Asthma is a chronic disorder, characterized by airway hyperresponsiveness (AHR), airway inflammation and airway remodelling. Evidence has been provided for a relationship between pathophysiology, airway inflammation and remodelling. Moreover, these asthma features have been shown to respond to anti-inflammatory therapy. According to current guidelines, monitoring of asthma is predominantly based on symptoms and lung function data. However, these parameters appeared as poor indices for asthma control. Alternatively, asthma control relates well to exacerbations and (anamnestic) surrogate biomarkers of airway inflammation. Hence, appropriate treatment of asthma should primarily target the airway inflammation. According to current guidelines for asthma management, anti-inflammatory therapy with inhaled corticosteroids (ICS) is the cornerstone in the treatment of persistent asthma. To further optimize asthma control, add-on therapy with long-acting beta2-agonists (LABA) or leukotriene receptor antagonists (LTRA) should be combined with low to high doses of ICS. While the first combination focuses on optimal control of symptoms and lung function, the second provides a more complete suppression of the airway inflammation. In this paper we discuss treatment of asthma according to current guidelines versus new insights, addressing practical issues.

Therapeutic modulation of allergic airways disease with leukotriene receptor antagonists

Although asthma is one of the most common chronic respiratory conditions, it often remains unrecognized and undertreated, while patients are often reluctant to comply with regular inhaled anti-inflammatory and bronchodilator therapy. Allergic rhinitis co-exists with asthma in as many as 40% of patients, and can be regarded as a continuum of the same inflammatory disease process. Corticosteroids are the 'gold standard' first-line treatment for both conditions, and have a significant impact upon underlying inflammation, symptoms and long-term outcome. Cysteinyl leukotrienes are potent airway inflammatory mediators, suggesting that treatment antagonizing their effects could play a role in disease management. In recent years, leukotriene receptor antagonists have provided a further therapeutic option in the management of allergic airways disease. These drugs are orally active, can be administered once daily, and provide a systemic approach to the management of patients with asthma and allergic rhinitis. We review the pharmacology of leukotriene receptor antagonists, their potential role in clinical practice in patients with allergic airways disease, and likely areas for further research.

A proof of concept study to evaluate putative benefits of montelukast in moderate persistent asthmatics

AIMS

Whether chronic dosing with montelukast confers benefit in patients with moderate to severe asthma remains to be fully established. A proof of concept study was performed evaluating putative benefits with montelukast in moderate persistent asthmatics who were taken off inhaled corticosteroids (ICS) and switched to salmeterol. The latter was done to dissociate the effects of montelukast from ICS.

METHODS

Twenty moderate to severe persistent asthmatics completed a randomized double-blind crossover study. Subjects received montelukast 10 mg daily or placebo for 2 weeks each. This was preceded by a 2-week run-in when ICS were discontinued and salmeterol started, and used on a regular basis throughout the study. Measurements were made after run-in and after both randomized treatments.

RESULTS

There were no significant sequence effects for responses as to whether placebo or montelukast were given first or second. Methacholine PD20 values after run-in, first and second placebo were 63 micro g, 60 micro g and 64 micro g, respectively (corresponding to 2, 4 and 6 weeks of ICS washout, respectively). Lung function deteriorated pre vs post run-in, which was significant (P < 0.05) for FEF25-75 % predicted. Montelukast conferred significant (P < 0.05) improvements as change from post run-in compared with placebo in methacholine PD20, FEV1 % predicted, FEF25-75 % predicted, diurnal peak expiratory flow, symptoms and salbutamol use. For the primary outcome of methacholine PD20, this amounted to a 1.6-fold difference (95% CI 1.1, 2.5).

CONCLUSIONS

In moderate persistent asthmatics switched from taking ICS to salmeterol alone, adding montelukast conferred significant benefits on all parameters of asthma control. Further studies are indicated to evaluate whether montelukast exhibits additive effects to ICS/long-acting beta2-adrenoceptor agonist combination inhalers upon clinically important outcomes.

Effects of montelukast on surrogate inflammatory markers in corticosteroid-treated patients with asthma

We evaluated whether montelukast conferred additive effects in patients with asthma receiving fluticasone/salmeterol (FP/SM) combination and FP alone. Twenty-two patients with mild to moderate asthma completed a double-blind, placebo-controlled study. After a 2-week run-in using FP 250 microg/SM 50 microg 1 puff twice daily, patients entered a randomized crossover period to receive additional montelukast 10 mg daily or placebo for 3 weeks each. For the first 2 weeks, they received FP/SM 1 puff BID, and then they received FP 250 microg 1 puff BID for the 3rd week. The primary outcome was adenosine monophosphate challenge threshold and recovery time; secondary outcomes included surrogate inflammatory markers and lung function. Compared with FP/SM run-in, adding montelukast to FP/SM was better (p < 0.05) than placebo for inflammatory markers but not for lung function. For adenosine monophosphate threshold, recovery, exhaled nitric oxide, and blood eosinophils, there were 1.4 (95% confidence interval, 1.1-1.8) geometric mean fold, 10 minutes (3-17 minutes), 2.1 parts per billion (0.2-3.9 parts per billion), and 88 (34-172) x 10(6)/L differences, respectively. The combination of FP plus montelukast was superior to FP/SM for inflammatory markers but was inferior for lung function. Thus, in patients taking FP/SM or FP, montelukast conferred complimentary effects on surrogate inflammatory markers, which were dissociated from lung function. Further studies are required to evaluate whether these effects of montelukast translate into clinical benefits.

The role of antileukotrienes in the treatment of asthma

Cysteinyl leukotrienes (Cys-LTs) are mediators released in asthma and are both direct bronchoconstrictors and proinflammatory substances that mediated several steps in the pathophysiology of chronic asthma, including inflammatory cells recruitment, vascular leakage, and possibly airway remodelling. Available evidence from clinical trials and real world experience derived from managing patients with asthma justifies a broader role for antiLTRAs in asthma management than that recommended in the National Asthma Education and Prevention Programm (NAEPP) and National Health Lung and Blood Institute (NHLBI) treatment guidelines. Leukotriene-receptor antagonist drugs (LTRAs) seem to be effective alternatives to inhaled corticosteroids (ICS) either as monotherapy or as adjunctive therapy that reduces the need for higher doses of ICS in patients with mild-to-moderate persistent asthma. LTRAs may be used as adjunctive therapy for al levels of disease severity because they are effective in combination with ICS during long-term maintenance therapy. The agents seem especially effective in preventing aspirin-induced asthma, exercise-induced asthma (EIA) and they may provide an additional advantage of reducing nasal congestion in patients with both asthma and rhinitis.

Prostaglandins and leukotrienes: advances in eicosanoid biology

Prostaglandins and leukotrienes are potent eicosanoid lipid mediators derived from phospholipase-released arachidonic acid that are involved in numerous homeostatic biological functions and inflammation. They are generated by cyclooxygenase isozymes and 5-lipoxygenase, respectively, and their biosynthesis and actions are blocked by clinically relevant nonsteroidal anti-inflammatory drugs, the newer generation coxibs (selective inhibitors of cyclooxygenase-2), and leukotriene modifiers. The prime mode of prostaglandin and leukotriene action is through specific G protein-coupled receptors, many of which have been cloned recently, thus enabling specific receptor agonist and antagonist development. Important insights into the mechanisms of inflammatory responses, pain, and fever have been gleaned from our current understanding of eicosanoid biology.