Leukotriene activity modulation in asthma

Current Thinking on the Relationship Between Rhinosinusitis and Asthma

An observation made initially on clinical grounds and epidemiologic evidence, i.e., that rhinosinusitis and asthma are closely linked diseases is now supported by a growing body of scientific evidence. Most recent evidence supports the characterization of rhinosinusitis and asthma as two compartmental expressions of a common mucosal susceptibility to exogenous stimuli. In addition, there is evidence that the compartmental processes can affect and amplify each other via a systemic intermediary. The bone marrow is involved in this process, and IL-5 may be a key cytokine for orchestrating the systemic interaction. These facts argue that rhinosinusitis and asthma are not simply localized disease processes but part of a systemic inflammatory disease affecting the respiratory tract. They also provide a compelling rationale for combined treatment strategies with consideration of the treatment of rhinosinusitis as a means of improving asthma control and monitoring for signs of bronchial involvement in those with rhinosinusitis.

Biomarkers in breath condensate: a promising new non-invasive technique in free radical research

Oxidative stress is associated with a range of inflammatory lung diseases including asthma, adult respiratory distress syndrome, idiopathic pulmonary fibrosis, pneumonia, lung transplantation, chronic obstructive pulmonary disease, cystic fibrosis, bronchiectasis and lung cancer. Increased concentrations of reactive oxygen species (ROS) in the airways of such patients are reflected by elevated concentrations of oxidative stress markers in the breath, airways, lung tissue and blood. Traditionally, the measurement of these biomarkers has involved invasive procedures to procure the samples, or examine the compartments. As a consequence, there is a need for less invasive approaches to measure oxidative stress. Analysis of breath hydrocarbons has partly fulfilled this need, however only gas phase volatile constituents can be assessed by this approach. The collection of exhaled breath condensate (EBC) is a simple, non-invasive approach, which comprehensively samples the lower respiratory tract. It is currently used as a research and diagnostic tool in the free radical field, yielding information on redox disturbance and the degree and type of inflammation in the lung. With further technical developments, such an approach may ultimately have a role in the clinic, in helping to diagnose specific lung diseases. EBC can be exploited to assess a spectrum of potential biomarkers, thus generating a "finger print" characteristic of the disease. By assessing the nature of oxidative stress in this manner, the most appropriate therapy can be selected and the response to treatment monitored.

Diet and asthma: has the role of dietary lipids been overlooked in the management of asthma?

OBJECTIVE

This article discusses the role of diet in the management of asthma. Readers will gain an understanding of how evolution of the western diet has contributed to increased asthma prevalence and how dietary modification that includes management of dietary lipids may reduce symptoms of asthma.

DATA SOURCES

Relevant studies published in English were reviewed.

STUDY SELECTION

Medline search to identify peer-reviewed abstracts and journal articles.

RESULTS

Asthma and obesity, which often occur together, have increased in prevalence in recent years. Studies suggest adaption of a western diet has not only contributed to obesity, but that increased intake of specific nutrients can cause changes in the frequency and severity of asthma. Increased asthma prevalence has also been proposed to arise from increased exposure to diesel particles or lack of exposure to infectious agents or endotoxins during childhood, generating a biased Th2 immune response, and increased cytokine and leukotriene production. Antagonists directed against these pro-inflammatory mediators include anticytokines and antileukotrienes. A reduction in the levels of inflammatory mediators associated with asthma has also been seen with dietary interventions, such as the administration of oils containing gamma-linolenic acid and eicosapentaenoic acid.

CONCLUSIONS

Evidence suggests elevated body mass index and dietary patterns, especially intake of dietary lipids, contribute to symptoms of asthma. Dietary modification may help patients manage their asthma as well as contribute to their overall health.

Mediators of adenosine- and ovalbumen-induced bronchoconstriction of sensitized guinea-pig isolated airways

The mediators of bronchoconstriction of isolated lungs and trachea from ovalbumen sensitized guinea-pigs to adenosine and ovalbumen were examined using relevant antagonists. Changes in perfusion pressure and tension of paired lung halves and tracheal spiral strips, respectively, were recorded in response to adenosine (1 mM lung, 300 microM trachea), histamine (10 microM), methacholine (10 microM) and ovalbumen (10 microg). One half was perfused with antagonist while the other received vehicle. Tracheal strips were superfused throughout with the P(1) receptor antagonist 8-phenyltheophylline, to examine 8-phenyltheophylline-resistant responses. The histamine H(1) receptor antagonist, mepyramine (1.5 mM), the cyclooxygenase inhibitors, indomethacin (5 mM) and diclofenac (5 mM), the leukotriene receptor antagonist, zafirlukast (1 mM), and the lipoxygenase inhibitor, zileuton (20 mM), alone failed to inhibit bronchoconstriction by adenosine and ovalbumen of the lung and trachea. When two antagonists were combined, only mepyramine and zafirlukast significantly reduced the lung responses to adenosine and ovalbumen. The tracheal adenosine response was substantially reduced, although not significantly, while ovalbumen was significantly reduced. When mepyramine, indomethacin and zafirlukast were combined, the lung constriction by adenosine and ovalbumen were virtually abolished. Similarly, the combination of mepyramine, diclofenac and zafirlukast significantly attenuated the lung responses to adenosine and ovalbumen. Thus, histamine, cyclooxygenase products and leukotrienes alone are not responsible for the bronchoconstriction of isolated sensitized lung tissues to adenosine or ovalbumen, which appears to be due to the release of all three mediators.

Design, synthesis and pharmacological evaluation of novel pyrazolo[3,4-b]thieno[2,3-d]pyridine acid derivatives: a new class of anti-inflammatory and anti-platelet agents

A series of pyrazolo[3,4-b]thieno[2,3-d]pyridine alkanoic acid derivatives has been synthesized and evaluated as thromboxane synthetase inhibitors and leukotriene D(4) receptor antagonists. The glutaric acid derivative LASSBio341 (6) was shown to be active in arachidonic acid-induced platelet aggregation (IC(50)=0.14 microM) and inhibition of the contraction of guinea pig tracheal strip induced with LTD(4) (IC(50) = 43.7 microM), displaying still in vivo anti-inflammatory profile.

Safety of antileukotriene agents in asthma management

OBJECTIVE

This article presents information on the safety of zafirlukast, montelukast, and zileuton, three antileukotrienes (anti-LTs) approved in the United States for the prophylaxis and treatment of asthma. After reading this article, readers should have an understanding both of the general safety of anti-LTs and their specific adverse effects.

DATA SOURCES

Relevant and appropriate controlled clinical studies on the safety of anti-LTs in asthma were used. Only literature in the English language was reviewed.

STUDY SELECTION

Material was taken from academic/scholarly journals and appropriate reviews.

RESULTS

Antiasthma agents, including corticosteroids, beta2-agonists, and methylxanthines, may be categorized into two classes: those used for the long-term control and prevention of persistent asthma and those used for the prompt relief of acute symptoms and exacerbations of the disease. Although most agents are safe and well tolerated when used properly, adverse effects may occur with use at higher dose levels. The anti-LTs, including zafirlukast, montelukast, and zileuton, are the first new pharmacologic class in the therapeutic armamentarium for asthma management to be approved in the United States in the past 20 years. Both zafirlukast and montelukast carry pregnancy category B classification whereas zileuton carries pregnancy category C classification. The most common adverse effects observed in clinical trials were headache, pharyngitis, abdominal pain, dyspepsia, and cough.

CONCLUSIONS

The results of clinical trials and real-world experience indicate that these agents are generally safe and well tolerated, with an incidence of adverse effects comparable with placebo.

Discovery of CP-199,330 and CP-199,331: two potent and orally efficacious cysteinyl LT1 receptor antagonists devoid of liver toxicity

CP-199,330 (3) and CP-199,331 (4) are cysLT1 receptor antagonists that are equipotent to marketed cysLT1 receptor antagonists zafirlukast and pranlukast, show good pharmacokinetics in rats and monkeys, and are devoid of liver toxicity in monkeys as seen in CP-85,958 (1).

Leukotrienes, leukotriene receptor antagonists and leukotriene synthesis inhibitors in asthma: an update. Part II: clinical studies with leukotriene receptor antagonists and leukotriene synthesis inhibitors in asthma

The demonstration that leukotrienes, mainly cysteinyl leukotrienes, have biological properties relevant to the pathogenesis of asthma has stimulated the development of many therapeutic compounds to block these deleterious effects. Two main classes of leukotriene modulators have been developed: CysLT1 receptor antagonists and leukotriene synthesis inhibitors. This article reviews the pharmacodynamics, the effects on baseline airway function, the protective effects in airway challenges as well as the results in chronic asthma of the different leukotriene modulators. In addition, the complementary anti-inflammatory effect of leukotriene modulators to that of corticosteroids and H1-histamine receptor antagonists is reviewed. Finally, a concise overview of the clinical responsiveness to this new class of drug, the safety and the drug interactions as well as the place in the strategies of treatment for asthmatic patients of the leukotriene modulators is also provided.

Comparison of inhaled salmeterol and oral zafirlukast in patients with asthma

BACKGROUND

Salmeterol, a long-acting beta2 -agonist, and zafirlukast, a leukotriene receptor antagonist, are both indicated for the treatment of asthma in adolescent and adult patients.

OBJECTIVE

We sought to compare the effect of 4 weeks of treatment with inhaled salmeterol xinafoate versus oral zafirlukast in the treatment of persistent asthma.

METHODS

This was a randomized, double-blind, double-dummy, parallel-group, multicenter clinical trial. Patients, over 80% of whom were on a concurrent inhaled corticosteroid regimen, were treated for 4 weeks with either inhaled salmeterol xinafoate 42 microgram twice daily administered by means of a metered-dose inhaler or oral zafirlukast 20 mg twice daily. The primary efficacy measure was morning peak expiratory flow (PEF); secondary efficacy measures included evening PEF, asthma symptom scores, supplemental albuterol use, nighttime awakenings, sleep symptoms, asthma exacerbations, and FEV1.

RESULTS

Both inhaled salmeterol and oral zafirlukast resulted in within-group improvements from baseline in measures of pulmonary function, asthma symptoms, and supplemental albuterol use. Salmeterol treatment resulted in significantly greater improvements from baseline compared with zafirlukast for most efficacy measurements, including morning PEF (29.6 vs 13.0 L/min; P </= .001), percentage of symptom-free days (22.4% vs 8.8%; P </= .001), and percentage of days and nights with no supplemental albuterol use (30.5% vs 11.3%; P </= .001). There were no differences in safety profiles as assessed by adverse event monitoring.

CONCLUSION

In patients with persistent asthma, most of whom were concurrently using inhaled corticosteroids, treatment with inhaled salmeterol provided significantly greater improvement than oral zafirlukast in overall asthma control over the 4-week treatment period.

An evaluation of zafirlukast in the treatment of asthma with exploratory subset analyses

BACKGROUND

Consensus asthma guidelines recommend antileukotriene agents as alternative therapy to existing anti-inflammatory medications; however, the full therapeutic potential of these medications has not yet been determined.

OBJECTIVE

The purpose of this study was to assess the efficacy and safety of the oral leukotriene receptor antagonist zafirlukast (20 mg twice daily) in subgroups of patients who have asthma with the use of integrated data from four 13-week trials.

METHODS

The trials had comparable designs, entry criteria, and clinical assessments. Patient subgroups were characterized by demographic and baseline asthma characteristics. Analysis of covariance models were tested for overall treatment effect and for interactions between treatment and subgroup characteristics.

RESULTS

Patients with mild-to-moderate asthma (12 to 76 years old) who were treated with albuterol alone were randomized (nZ = 879; nP = 605) and included in subset analyses. Significant overall treatment effects, favoring zafirlukast, were noted for measures of daytime and nighttime symptoms, beta2 -agonist use, and pulmonary function (P <.05). A significant, quantitative, treatment-by-age interaction was noted for beta2 -agonist use (P <. 03), suggesting greater reductions in rescue medication use with increasing patient age. Compared with placebo, similar size and/or direction of response was noted with zafirlukast in the various subgroups, indicating a benefit with zafirlukast regardless of subgroup. Significant treatment-by-strata interactions (P <.05), favoring zafirlukast, were noted for various outcome measures in subgroups with the greatest amount of baseline beta2 -agonist use (>8 puffs/day) and with greater baseline peak flow variability (>/=20%) and baseline airflow obstruction (FEV1 /forced vital capacity ratio, <0.70). The overall treatment failure rate was significantly lower in the zafirlukast group compared with the placebo group (P <.003). No associations were observed between any adverse events and subgroups defined by demographic characteristics.

CONCLUSIONS

Exploratory subset analyses showed that zafirlukast is similarly efficacious in patients with asthma who have differing demographic characteristics and degrees of subjective symptoms. Additionally, zafirlukast appears to be incrementally beneficial in patients with more moderate disease, defined by a greater requirement for as-needed rescue medication and more abnormal pulmonary function at baseline. Over 13 weeks, zafirlukast was well tolerated and demonstrated a safety profile clinically indistinguishable from placebo.

Therapeutic advances: leukotriene antagonists for the treatment of asthma

Asthma is the most common respiratory disease encountered in clinical practice, affecting both children and adults. It is an important cause of respiratory morbidity and mortality. Recent therapeutic developments have shown that leukotrienes are the most potent and important inflammatory mediators in the pathology of both acute and chronic asthma. They cause increased bronchoconstriction, mucous secretion, and vascular permeability. Studies using compounds that block leukotrienes (receptor antagonists - montelukast and zafirlukast and 5-lipoxygenase inhibitors - zileuton) have demonstrated improved asthma control in patients aged 12 years and older. In this article we assess the therapeutic importance of these new compounds.

Zafirlukast. A review of its pharmacology and therapeutic potential in the management of asthma

Zafirlukast is a competitive and selective leukotriene receptor antagonist indicated for the prophylaxis and treatment of chronic asthma. The rationale for the development of leukotriene antagonists was based on in vitro and in vivo data demonstrating the extensive role of the cysteinyl leukotrienes C4 (LTC4), D4 (LTD4) and E4 (LTE4) in the pathogenesis of asthma. Initial data have demonstrated an improvement in pulmonary function and symptom control and a reduction in the use of short-acting inhaled beta 2-adrenoceptor agonist therapy in patients with mild to moderate asthma treated with oral zafirlukast at the recommended dosage of 20 mg twice daily. Available data also suggest that zafirlukast may significantly reduce the incidence of asthma exacerbations. Data on the comparative efficacy of zafirlukast and existing antiasthma medications are limited. Results from 2 double-blind randomised studies comparing zafirlukast 20 mg twice daily with sodium cromoglycate aerosol or dry powder inhalation reported similar efficacy for both drugs. In a comparison with inhaled beclomethasone dipropionate (0.2 to 0.25 mg twice daily), improvements in morning peak expiratory flow rate, forced expiratory volume in 1 second and daytime symptom score were significantly less with zafirlukast 20 mg twice daily for 6 weeks. However, available data suggest that patient compliance and patient preference may be greater with oral zafirlukast 20 mg twice daily than with twice-daily inhaled corticosteroid therapy. Confounding results from 2 studies preclude any clear conclusions regarding the potential steroid-sparing effect of zafirlukast at the recommended dosage of 20 mg twice daily. Furthermore, Churg-Strauss syndrome has been reported in 6 patients who were being withdrawn from oral corticosteroid therapy while receiving treatment with oral zafirlukast. It is, therefore, recommended that zafirlukast-treated patients who require a reduction in their oral corticosteroid therapy are closely monitored. Zafirlukast is generally well tolerated. Reports of elevated liver enzymes in patients receiving high dosages of zafirlukast (80 mg twice daily) preclude the use of dosages exceeding 40 mg twice daily. Careful monitoring is necessary in zafirlukast-treated patients receiving concomitant therapy with drugs such as warfarin, terfenadine and erythromycin because of the potential for drug interactions. Thus, zafirlukast is a potentially useful addition to current antiasthma therapies in patients with mild to moderate asthma. Because zafirlukast is administered orally, it may be particularly beneficial in patients poorly compliant with asthma therapy as a result of poor inhaler technique. Further investigation of the efficacy of zafirlukast is expected to more clearly define its position in the management of asthma.