Worldwide clinical experience with the first marketed leukotriene receptor antagonist

G Protein-Coupled Receptors in Asthma Therapy: Pharmacology and Drug Action

Asthma is a heterogeneous inflammatory disease of the airways that is associated with airway hyperresponsiveness and airflow limitation. Although asthma was once simply categorized as atopic or nonatopic, emerging analyses over the last few decades have revealed a variety of asthma endotypes that are attributed to numerous pathophysiological mechanisms. The classification of asthma by endotype is primarily routed in different profiles of airway inflammation that contribute to bronchoconstriction. Many asthma therapeutics target G protein-coupled receptors (GPCRs), which either enhance bronchodilation or prevent bronchoconstriction. Short-acting and long-acting β 2-agonists are widely used bronchodilators that signal through the activation of the β 2-adrenergic receptor. Short-acting and long-acting antagonists of muscarinic acetylcholine receptors are used to reduce bronchoconstriction by blocking the action of acetylcholine. Leukotriene antagonists that block the signaling of cysteinyl leukotriene receptor 1 are used as an add-on therapy to reduce bronchoconstriction and inflammation induced by cysteinyl leukotrienes. A number of GPCR-targeting asthma drug candidates are also in different stages of development. Among them, antagonists of prostaglandin D2 receptor 2 have advanced into phase III clinical trials. Others, including antagonists of the adenosine A2B receptor and the histamine H4 receptor, are in early stages of clinical investigation. In the past decade, significant research advancements in pharmacology, cell biology, structural biology, and molecular physiology have greatly deepened our understanding of the therapeutic roles of GPCRs in asthma and drug action on these GPCRs. This review summarizes our current understanding of GPCR signaling and pharmacology in the context of asthma treatment. SIGNIFICANCE STATEMENT: Although current treatment methods for asthma are effective for a majority of asthma patients, there are still a large number of patients with poorly controlled asthma who may experience asthma exacerbations. This review summarizes current asthma treatment methods and our understanding of signaling and pharmacology of G protein-coupled receptors (GPCRs) in asthma therapy, and discusses controversies regarding the use of GPCR drugs and new opportunities in developing GPCR-targeting therapeutics for the treatment of asthma.

Cysteinyl leukotrienes as novel host factors facilitating Cryptococcus neoformans penetration into the brain

Cryptococcus neoformas infection of the central nervous system (CNS) continues to be an important cause of mortality and morbidity, and a major contributing factor is our incomplete knowledge of the pathogenesis of this disease. Here, we provide the first direct evidence that C. neoformans exploits host cysteinyl leukotrienes (LTs), formed via LT biosynthetic pathways involving cytosolic phospholipase A₂ α (cPLA₂ α) and 5-lipoxygenase (5-LO) and acting via cysteinyl leukotriene type 1 receptor (CysLT1), for penetration of the blood-brain barrier. Gene deletion of cPLA₂ α and 5-LO and pharmacological inhibition of cPLA₂ α, 5-LO and CysLT1 were effective in preventing C. neoformans penetration of the blood-brain barrier in vitro and in vivo. A CysLT1 antagonist enhanced the efficacy of an anti-fungal agent in therapy of C. neoformans CNS infection in mice. These findings demonstrate that host cysteinyl LTs, dependent on the actions of cPLA₂ α and 5-LO, promote C. neoformans penetration of the blood-brain barrier and represent novel targets for elucidating the pathogenesis and therapeutic development of C. neoformans CNS infection.

A Case of Pranlukast-Induced Anaphylactic Shock

Leukotriene receptor antagonists, which are generally considered safe with a few adverse drug reactions, are increasingly used in the treatment of various allergic diseases, including asthma and allergic rhinitis. Although a few anaphylactic reactions to montelukast have been reported worldwide, there is still a lack of reports about severe adverse drug reactions associated with pranlukast. Here, we report a case of severe hypersensitivity reaction associated with pranlukast. A 65-year-old woman developed anaphylactic shock that presented as generalized urticaria, angioedema, collapse, and loss of consciousness after receiving pranlukast. A positive response to oral challenge and skin prick testing with pranlukast was observed in the patient. In this case, it was demonstrated that pranlukast can induce anaphylaxis, possibly mediated by the IgE-dependent pathway.

Anti-leukotriene agents compared to inhaled corticosteroids in the management of recurrent and/or chronic asthma in adults and children

BACKGROUND

Anti-leukotrienes (5-lipoxygenase inhibitors and leukotriene receptors antagonists) serve as alternative monotherapy to inhaled corticosteroids (ICS) in the management of recurrent and/or chronic asthma in adults and children.

OBJECTIVES

To determine the safety and efficacy of anti-leukotrienes compared to inhaled corticosteroids as monotherapy in adults and children with asthma and to provide better insight into the influence of patient and treatment characteristics on the magnitude of effects.

SEARCH METHODS

We searched MEDLINE (1966 to Dec 2010), EMBASE (1980 to Dec 2010), CINAHL (1982 to Dec 2010), the Cochrane Airways Group trials register, and the Cochrane Central Register of Controlled Trials (Dec 2010), abstract books, and reference lists of review articles and trials. We contacted colleagues and the international headquarters of anti-leukotrienes producers.

SELECTION CRITERIA

We included randomised trials that compared anti-leukotrienes with inhaled corticosteroids as monotherapy for a minimum period of four weeks in patients with asthma aged two years and older.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the methodological quality of trials and extracted data. The primary outcome was the number of patients with at least one exacerbation requiring systemic corticosteroids. Secondary outcomes included patients with at least one exacerbation requiring hospital admission, lung function tests, indices of chronic asthma control, adverse effects, withdrawal rates and biological inflammatory markers.

MAIN RESULTS

Sixty-five trials met the inclusion criteria for this review. Fifty-six trials (19 paediatric trials) contributed data (representing total of 10,005 adults and 3,333 children); 21 trials were of high methodological quality; 44 were published in full-text. All trials pertained to patients with mild or moderate persistent asthma. Trial durations varied from four to 52 weeks. The median dose of inhaled corticosteroids was quite homogeneous at 200 µg/day of microfine hydrofluoroalkane-propelled beclomethasone or equivalent (HFA-BDP eq). Patients treated with anti-leukotrienes were more likely to suffer an exacerbation requiring systemic corticosteroids (N = 6077 participants; risk ratio (RR) 1.51, 95% confidence interval (CI) 1.17, 1.96). For every 28 (95% CI 15 to 82) patients treated with anti-leukotrienes instead of inhaled corticosteroids, there was one additional patient with an exacerbation requiring rescue systemic corticosteroids. The magnitude of effect was significantly greater in patients with moderate compared with those with mild airway obstruction (RR 2.03, 95% CI 1.41, 2.91 versus RR 1.25, 95% CI 0.97, 1.61), but was not significantly influenced by age group (children representing 23% of the weight versus adults), anti-leukotriene used, duration of intervention, methodological quality, and funding source. Significant group differences favouring inhaled corticosteroids were noted in most secondary outcomes including patients with at least one exacerbation requiring hospital admission (N = 2715 participants; RR 3.33; 95% CI 1.02 to 10.94), the change from baseline FEV(1) (N = 7128 participants; mean group difference (MD) 110 mL, 95% CI 140 to 80) as well as other lung function parameters, asthma symptoms, nocturnal awakenings, rescue medication use, symptom-free days, the quality of life, parents' and physicians' satisfaction. Anti-leukotriene therapy was associated with increased risk of withdrawals due to poor asthma control (N = 7669 participants; RR 2.56; 95% CI 2.01 to 3.27). For every thirty one (95% CI 22 to 47) patients treated with anti-leukotrienes instead of inhaled corticosteroids, there was one additional withdrawal due to poor control. Risk of side effects was not significantly different between both groups.

AUTHORS' CONCLUSIONS

As monotherapy, inhaled corticosteroids display superior efficacy to anti-leukotrienes in adults and children with persistent asthma; the superiority is particularly marked in patients with moderate airway obstruction. On the basis of efficacy, the results support the current guidelines' recommendation that inhaled corticosteroids remain the preferred monotherapy. 

Tolerability profiles of leukotriene receptor antagonists and long-acting beta2-adrenoceptor agonists in combination with inhaled corticosteroids for treatment of asthma: a review

Inhaled corticosteroids, long-acting beta2-adrenoceptor agonists, and leukotriene receptor antagonists are widely used for treatment of asthma. Inhaled corticosteroids are recommended as first-line therapy, whereas long-acting beta2-adrenoceptor agonists and leukotriene receptor antagonists are indicated as add-on therapy in patients not adequately controlled with corticosteroids alone. A number of studies have investigated the efficacy of combinations of these drugs in asthma, but several issues concerning the safety of these treatments are highly debated. This review provides a critical appraisal of the tolerability profiles of long-acting beta2-agonists and leukotriene receptor antagonists used in combination with inhaled corticosteroids for the treatment of asthma.

Targeting cysteinyl leukotrienes in patients with rhinitis, sinusitis and paranasal polyps

Leukotrienes have been known in the field of immunology since the 1930s. At that time they were referred to as the slow reacting substance of anaphylaxis. They were not, however, characterized until the 1980s, when they were noted to be formed during the breakdown of arachidonic acid by the enzyme 5-lipoxygenase. The leukotrienes consist of leukotriene (LT) A4, LTB4, LTC4, LTD4 and LTE4, so named because the molecule was originally isolated from leukocytes and therefore its carbon backbone contains three double bonds in series, which constitutes a trion. This structural information provided the key to the oxidative pathway of lipometabolism, known as the 5-lipoxygenase. Leukotrienes are classified as inflammatory mediators, and therefore they are produced by a number of cell types, particularly mast cells, eosinophils, basophils, macrophages and monocytes. With the identification of asthma, allergic rhinitis and paranasal sinusitis associated with inflammatory pathways, the leukotrienes have been implicated in the pathogenesis of these conditions and have become targets for therapeutic modulation. Leukotriene synthesis inhibitors have been used successfully in the treatment of patients with asthma where they have demonstrated the ability to induce bronchial dilatation, provide protection against broncho-provocation tests and significantly diminish symptoms. When it was serendipitously noted that patients who had concomitant nasal pathology also showed improvement, leukotriene synthesis inhibitors were used as adjuvant therapy in the management of patients with rhinitis, sinusitis and nasal polyposis. Preliminary studies have demonstrated improvements in nasal airflow and reduced recurrence of nasal polyps as noted by endoscopy and imaging studies. Leukotriene synthesis inhibitors therefore appear to be a novel treatment modality for patients with rhinitis, sinusitis and nasal polyps when used as adjunctive therapy.

Anti-leukotriene agents compared to inhaled corticosteroids in the management of recurrent and/or chronic asthma in adults and children

BACKGROUND

Anti-leukotrienes agents are currently being studied as alternative first line agents to inhaled corticosteroids in mild to moderate chronic asthma.

OBJECTIVES

To compare the safety and efficacy of anti-leukotriene agents with inhaled glucocorticoids (ICS) and to determine the dose-equivalence of anti-leukotrienes to daily dose of ICS.

SEARCH STRATEGY

We searched MEDLINE (1966 to Aug 2003), EMBASE (1980 to Aug 2003), CINAHL (1982 to Aug 2003), the Cochrane Airways Group trials register, and the Cochrane Central Register of Controlled Trials (August 2003), abstract books, and reference lists of review articles and trials. We contacted colleagues and international headquarters of anti-leukotrienes producers.

SELECTION CRITERIA

Randomised controlled trials that compared anti-leukotrienes with inhaled corticosteroids during a minimal 30-day intervention period in asthmatic patients aged 2 years and older.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the methodological quality or trials and extracted trial data. The primary outcome was the rate of exacerbations requiring systemic corticosteroids. Secondary outcomes included lung function, indices of chronic asthma control, adverse effects and withdrawal rates.

MAIN RESULTS

27 trials (including 1 trial testing two protocols) met the inclusion criteria; 13 were of high methodological quality; 20 are published in full-text. All trials pertained to patients with mild to moderate persistent asthma. Only 3 trials focused on children and adolescents. Trial duration varied from 4 to 37 weeks. In most trials, daily dose of ICS was 400 mcg of beclomethasone or equivalent. Patients treated with anti-leukotrienes were 65% more likely to suffer an exacerbation requiring systemic steroids [Relative Risk 1.65; 95% Confidence Interval (CI) 1.36 to 2.00]. Twenty six (95% CI: 17 to 47) patients must be treated with anti-leukotrienes instead of inhaled corticosteroids to cause one extra exacerbation. Significant differences favouring ICS were noted in secondary outcomes where()the improvement in FEV(1) reached 130 mL [13 trials; 95% CI: 50, 140 mL ]. Other significant benefits of ICS were seen for symptoms, nocturnal awakenings, rescue medication use, symptom-free days, and quality of life. Anti-leukotriene therapy was associated with 160% increased risk of withdrawals due to poor asthma control. Twenty nine (95% CI 20 to 48) patients must be treated with anti-leukotrienes instead of inhaled corticosteroids to cause one extra withdrawal due to poor control. Risk of side effects was not different between groups.

REVIEWERS' CONCLUSIONS

Inhaled steroids at a dose of 400 mcg/day of beclomethasone or equivalent are more effective than anti-leukotriene agents given in the usual licensed doses. The exact dose-equivalence of anti-leukotriene agents in mcg of ICS remains to be determined. Inhaled glucocorticoids should remain the first line monotherapy for persistent asthma.

Pranlukast: a review of its use in the management of asthma

Pranlukast (Onon, Azlaire), is an orally administered, selective, competitive antagonist of the cysteinyl leukotrienes (LT) C(4), LTD(4) and LTE(4). It is indicated for the prophylactic treatment of chronic bronchial asthma in paediatric and adult patients. The efficacy of pranlukast 225mg twice daily in adults with mild to moderate asthma was demonstrated in double-blind, placebo- or azelastine-controlled studies of 4 or 8 weeks' duration. The drug at this dosage was superior to both comparators in improving mean attack scores and morning and/or evening peak expiratory flow rates, and decreasing the use of rescue bronchodilators (p < 0.05). In limited clinical studies, pranlukast 225mg twice daily appeared to be as effective as montelukast 10mg once daily and zafirlukast 40mg twice daily in adults with mild to moderate asthma. Tachyphylaxis was absent when the drug was administered for up to 4 years. In patients requiring high-dose inhaled corticosteroid therapy, pranlukast 225 mg twice daily plus a halved dosage of inhaled corticosteroid was as effective as the original dosage of inhaled corticosteroid. Pranlukast was also effective in patients with mild to severe asthma in a clinical practice setting. In a double-blind trial, greater improvements in most outcome measures were observed with pranlukast than with oxatomide in children and adolescents with asthma. In clinical trials, pranlukast was well tolerated in adult and paediatric patients with asthma, with an adverse event profile similar to that of placebo. Gastrointestinal events and hepatic function abnormalities were the most commonly reported adverse events. No clinically significant differences in adverse event profiles between pranlukast, zafirlukast or montelukast were shown in limited comparisons. Although Churg-Strauss syndrome has been noted in pranlukast recipients, a direct causal relationship is unlikely.

CONCLUSIONS

Pranlukast is a well tolerated and effective preventative treatment in adult and paediatric patients with persistent asthma of all severities. In some patients, pranlukast may be beneficial when added to low-dose inhaled corticosteroids; it may also be a viable alternative to increasing inhaled corticosteroid dosages. The efficacy of pranlukast relative to placebo has been confirmed; its efficacy relative to other therapy awaits further investigation. Nonetheless, pranlukast is a useful therapeutic option (with as-required short-acting beta(2)-agonists), either as preventative monotherapy for the treatment of mild persistent asthma or in conjunction with inhaled corticosteroids in the management of moderate or severe persistent asthma.

Benefit-risk assessment of antileukotrienes in the management of asthma

Antileukotrienes are a relatively new class of anti-asthma drugs that either block leukotriene synthesis (5-lipoxygenase inhibitors) like zileuton, or antagonise the most relevant of their receptors (the cysteinyl leukotriene 1 receptor [CysLT1]) like montelukast, zafirlukast or pranlukast. Hence, their major effect is an anti-inflammatory one. With the exception of pranlukast, the other antileukotrienes have been studied and marketed in the US and Europe for long enough to establish that they are useful drugs in the management of asthma. Their effects, significantly better than placebo, seem more pronounced in subjective measurements (i.e. symptoms scores or quality-of-life tests) than in objective parameters (i.e. forced expiratory volume in 1 second or peak expiratory flow rate). Also, there is some evidence that these drugs work better in some subsets of patients with certain genetic polymorphisms - probably related to their leukotriene metabolism - or patients with certain asthma characteristics. There are a small number of comparative studies only, and with regard to long-term asthma control differences between the agents have not been evaluated. Nevertheless, their overall effect appears comparable with sodium cromoglycate (cromolyn sodium) or theophylline, but significantly less than low-dose inhaled corticosteroids. Antileukotrienes have been shown to have a degree of corticosteroid-sparing effect, but salmeterol appears to perform better as an add-on drug. Montelukast is probably the most useful antileukotriene for continuous treatment of exercise-induced asthma, performing as well as salmeterol without inducing any tolerance. All antileukotrienes are taken orally; their frequency of administration is quite different ranging from four times daily (zileuton) to once daily (montelukast). Antileukotrienes are well tolerated drugs, even though zileuton intake has been related to transitional liver enzyme elevations in some cases. Also Churg-Strauss syndrome (a systemic vasculitis), has been described in small numbers of patients taking CysLT1 antagonists. It is quite probable that this disease appears as a consequence of an 'unmasking' effect when corticosteroid dosages are reduced in patients with severe asthma once CysLT1 antagonists are introduced, but more data are needed to definitely establish the mechanism behind this effect. Overall, however, the benefits of antileukotrienes in the treatment of asthma greatly outweigh their risks.

The role of leukotriene inhibitors in patients with paranasal sinus disease

Leukotrienes are inflammatory mediators that are known as the slow-reacting substance of anaphylaxis produced by a number of cell types including mast cells, eosinophils, basophils, macrophages, and monocytes. Synthesis of these mediators results from the cleavage of arachidonic acid in cell membranes, and they exert their biologic effects by binding and activating specific adaptors. This occurs in a series of events that lead to contraction of the human airway smooth muscle, chemotaxis, and increased vascular permeability. These effects have led to their important role in the diseases of asthma, allergic rhinitis, and possible paranasal sinusitis with the formation of nasal polyps. Because these agents lead to the production of symptoms in patients that are asthmatic, the use of leukotriene enzyme inhibitors, particularly montelukast, and zafirlukasts seem appropriate. These classes of drugs can block the binding of leukotrienes to CysLT(1) receptors. Zileuton is a 5-lipoxygenase inhibitor that prevents the formation of leukotrienes and can also result in the prevention of leukotriene activity. Demonstrated efficacy in these patients in a number of studies has also suggested their role in inhibiting nasal symptoms in asthmatic patients. In addition, it has been suggested by serendipitous observations that many of the aspirin-intolerant patients have nasal polyps and that treatment with the leukotriene inhibitors has resulted in improvement and resolution of the polyps. Therefore, these agents may also play a role in patients afflicted with chronic sinusitis with concomitant nasal polyposis. These papers are discussed in detail because this form of therapy may represent a novel way to treat patients with this malady in addition to or in lieu of surgical treatment and steroid therapy.

The effect of seratrodast on eosinophil cationic protein and symptoms in asthmatics

Thromboxane A2 (TXA2), an arachidonate derivative, is a potent bronchoconstrictor; therefore, blocking TXA2 should attenuate airway narrowing. Seratrodast, a TXA2 receptor antagonist, is expected to be a potent antiasthmatic. It was reported that seratrodast reduced bronchial hyperresponsiveness. However, it is controversial whether it reduces airway inflammation. We studied some additional effects of oral seratrodast to inhaled corticosteroids on 10 adult asthmatics in an open-label, crossover design study. Eosinophil cationic protein (ECP) levels in serum and sputum, peak expiratory flow rate (PEF), clinical symptoms, and airway responsiveness were evaluated. Clinical symptom scores were improved by administration of seratrodast (p < 0.05). The addition of seratrodast to asthmatic patients significantly improved mean PEF (p < 0.05). In addition, withdrawal of seratrodast resulted in deterioration of PEF. Airway hyperresponsiveness to acetylcholine measured by Astograph was improved by administration of seratrodast (p < 0.01), and returned to the level of "run-in period" after withdrawal. Administration of seratrodast decreased the concentration of ECP in sputum significantly (p < 0.05), and sputum ECP significantly increased again after withdrawal of (p < 0.05). These results suggest that seratrodast improves clinical symptoms andairway hyperresponsiveness by reducing airway inflammation. Seratrodast may be useful as an anti-inflammatory agent and beneficial when added to inhaled corticosteroids in the treatment of bronchial asthma.

Inflammatory cells in asthma: mechanisms and implications for therapy

Recent clinical studies have brought asthma's complex inflammatory processes into clearer focus, and understanding them can help to delineate therapeutic implications. Asthma is a chronic airway inflammatory disease characterized by the infiltration of airway T cells, CD(+) (T helper) cells, mast cells, basophils, macrophages, and eosinophils. The cysteinyl leukotrienes also are important mediators in asthma and modulators of cytokine function, and they have been implicated in the pathophysiology of asthma through multiple mechanisms. Although the role of eosinophils in asthma and their contribution to bronchial hyperresponsiveness are still debated, it is widely accepted that their numbers and activation status are increased. Eosinophils may be targets for various pharmacologic activities of leukotriene receptor antagonists through their ability to downregulate a number of events that may be key to the effector function of these cells.

The role of leukotriene inhibitors in allergic rhinitis and paranasal sinusitis

Leukotrienes are inflammatory mediators that are known as the slow-reacting substance of anaphylaxis produced by a number of cell types, including mast cells, eosinophils, basophils, macrophages, and monocytes. Synthesis of these meditators in the text result from the cleavage of arachidonic acid in cell membranes, and exert their biologic effects by binding and activating specific adaptors. This occurs in a serious of events that lead to contraction of the human airway smooth muscle, chemotaxis, and increased vascular permeability. These effects have lead to their important role in the diseases of asthma, allergic rhinitis, and possible paranasal sinusitis with the formation of nasal polyps. Since these agents lead to the production of symptoms in patients who are asthmatic, the use of leukotriene enzyme inhibitors, particularly montelukast, zafirlukasts seem appropriate.

Anti-leukotriene agents compared to inhaled corticosteroids in the management of recurrent and/or chronic asthma in adults and children

BACKGROUND

Anti-leukotrienes agents are currently being studied as alternative first line agents to inhaled corticosteroids in mild to moderate chronic asthma.

OBJECTIVES

To compare the safety and efficacy of anti-leukotriene agents with inhaled glucocorticoids (ICS) and to determine the dose-equivalence of anti-leukotrienes to daily dose of ICS.

SEARCH STRATEGY

Medline (1966 to Jan 2002), Embase (1980 to Jan 2002), and Cinahl (1982 to Jan 2002) were searched and reference lists of review articles and trials. We contacted colleagues and international headquarters of anti-leukotrienes producers.

SELECTION CRITERIA

Randomised controlled trials that compared leukotriene antagonists with inhaled corticosteroids during a minimal 30-day intervention period in asthmatic patients aged 2 years and older.

DATA COLLECTION AND ANALYSIS

Two reviewers performed assessments of methodological quality and data extraction independently and blindly. The primary outcome was the rate of exacerbations requiring systemic corticosteroids. Secondary outcomes included lung function, indices of chronic asthma control, adverse effects and withdrawal rates.

MAIN RESULTS

14 trials met the inclusion criteria; 10 were of high methodological quality; 8 are published in full-text. All were in mild-to-moderate chronic asthma, Two included children or adolescents. Trial duration was 4 - 37 weeks. In most trials, daily dose of ICS was 400 mcg of beclomethasone-equivalent. Patients treated with anti-leukotrienes were 60% more likely to suffer an exacerbation requiring systemic steroids [12 trials; Relative Risk 1.61; 95% Confidence Interval (CI) 1.15, 2.25]. Significant differences favouring ICS were noted in most secondary outcomes, eg improvement in FEV1 [7 trials; Weighted Mean Difference 120 ml; 95% CI: 80, 170 ml ]; symptom scores [5 trials: Standardized Mean Difference 0.3; 95% CI 0.2, 0.4]. Other significant benefits of ICS were seen for nocturnal awakenings, rescue medication use, and quality of life. Risk of side effects was not different between groups, but anti-leukotriene therapy was associated with 30% increased risk of "withdrawals for any cause" or "withdrawals due to poor asthma control".

REVIEWER'S CONCLUSIONS

For most asthma outcomes, ICS at 400 mcg/day of beclomethasone-equivalent are more effective than anti-leukotriene agents given in the usual licensed doses. The exact dose-equivalence of anti-leukotriene agents in mcg of ICS remains to be determined.

Effects of pranlukast, a cysteinyl leukotriene receptor 1 antagonist, combined with inhaled beclomethasone in patients with moderate or severe asthma

BACKGROUND

Although inhaled steroids are used as the first line of therapy in asthmatic patients, symptoms of asthma do not improve completely in some patients.

OBJECTIVE

To investigate the effects of pranlukast, a cysteinyl leukotriene receptor 1 antagonist, in patients with moderate/severe asthma, when combined with beclomethasone dipropionate (BDP).

METHODS

Protocol 1: After a 2-week observation period, 41 patients with moderate asthma were divided into those receiving BDP at 1,600 microg/day or 800 microg/day + pranlukast (450 mg/day). The effect of treatment was evaluated by measuring AM peak expiratory flow rate, symptom score, frequency of beta2-agonists, and daily variability of peak expiratory flow rate. Protocol 2: 39 patients participated in this study including those with moderate asthma on 800 microg/day BDP (group I), severe asthma on BDP at 1,600 microg/day (group II), and severe asthma on 1,600 microg/day BDP + 5 to 20 mg prednisolone (group III). Patients of all groups were additionally treated with pranlukast.

RESULTS

Protocol 1: Both treatment regimens resulted in improvement in each clinical parameter. There were no significant differences in the effects of two treatment regimens. Protocol 2: Pranlukast was effective in group I and II, but not in group III. In groups I and II, pranlukast tended to be more effective when BDP was introduced within the first year of onset of asthma.

CONCLUSIONS

Pranlukast is effective for patients with moderate asthma and those patients with severe asthma who are not treated with oral steroids. Pranlukast is more effective in patients treated with BDP early after onset.

The anti-inflammatory effects of leukotriene-modifying drugs and their use in asthma

Asthma is a chronic inflammatory disease of the airways. Anti-inflammatory drug therapy, primarily using corticosteroids, is now considered the first-line treatment in the management of all grades of asthma severity. Although corticosteroids are believed to be the most potent anti-inflammatory agents available, they do not suppress all inflammatory mediators involved in the asthmatic response. Leukotrienes, which are lipid mediators generated from the metabolism of arachidonic acid, play an important role in the pathogenesis of asthma. They produce bronchospasm, increase bronchial hyperresponsiveness, mucus production, and mucosal edema, and enhance airway smooth muscle cell proliferation and eosinophil recruitment into the airways, and their synthesis or release is unaffected by corticosteroid administration. The use of leukotriene synthesis inhibitors or leukotriene receptor antagonists as anti-inflammatory therapies in asthma has therefore been investigated. Beneficial effects of leukotriene-modifying drugs have been demonstrated in the management of all grades of asthma severity, and there is evidence that certain patient groups (such as those with exercise-induced asthma or aspirin-induced asthma) may be particularly suitable for such therapy.

Efficacy and safety of long-term treatment of asthmatic patients with pranlukast, a cysteinyl-leukotriene-receptor antagonist: four-year followup study

BACKGROUND

There are few studies that have examined the long-term efficacy and safety of pranlukast, a leukotriene receptor antagonist, in asthmatic patients.

METHODS

Sixty-three asthmatic patients were entered in this 4-year study [group 1, mild or moderate (N = 22); group 2, severe without using oral prednisolone (N = 22); group 3, severe with using oral prednisolone (N = 19)]. Pranlukast was administered at 225 mg twice daily to 14 subjects in group 1 (group 1p), 14 in group 2 (group 2p), and 11 in group 3 (group 3p), chosen for pranlukast additional therapy at random. Another group of 24 asthmatic patients was assigned to conventional therapy group (groups 1c, 2c, and 3c). Efficacy was determined by improvement in symptom score, peak expiratory flow rate (PEFR) percentage predicted, reduced daily variability of PEFR (percentage), and reduced frequency of use of rescue beta2-agonist (times per week).

RESULTS

In groups 1p and 2p, PEFR percentage predicted began to improve from 2 weeks after commencement of treatment. The symptom score, daily variability of PEFR, and use of rescue beta2-agonist diminished significantly. In group 3p, pranlukast was ineffective in improving PEFR percentage predicted. All but two patients continued to receive pranlukast and no adverse effects were noted, at least during the 16-week therapy. Further, 22 patients continued to receive pranlukast for 4 years, and none experienced any adverse effects.

CONCLUSIONS

We showed in this study that long-term treatment with pranlukast is effective for asthmatic patients without any adverse effects.

The role of antileukotrienes in the treatment of asthma

OBJECTIVE

This article reviews the literature on the role of antileukotrienes (anti-LTs), specifically montelukast, zafirlukast, and zileuton, in the treatment of asthma.

DATA SOURCES

Relevant and appropriate controlled clinical studies were used. Only literature in the English language was reviewed.

STUDY SELECTION

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

RESULTS

In guidelines established by the National Asthma Education and Prevention Program and the National Heart, Lung, and Blood Institute, a stepwise approach to asthma management is recommended, with recommendations varying depending on degree of disease severity. The anti-LTs, the newest class of drugs for the treatment of asthma, play a circumscribed role in the guidelines as they were only recently available when the latest guidelines were published. Subsequently, however, extensive clinical experience with the anti-LTs has been amassed. Multiple clinical studies have demonstrated that the anti-LTs improve pulmonary function and quality of life, and reduce asthma symptoms, asthma exacerbations, and use of beta2-agonists and oral steroids. The anti-LTs may be particularly useful in asthma patients with aspirin sensitivity or concomitant allergic rhinitis, as well as in pediatric patients. These agents have additive effects with inhaled corticosteroids and may permit a reduction in inhaled corticosteroid dosages.

CONCLUSIONS

The anti-LTs have several features that are likey to promote adherence to treatment and are generally well tolerated. The available clinical data suggest that anti-LTs should be considered as a therapeutic option or as additive therapy in patients with mild to severe asthma.

Acute Effects of Antileukotrienes on Sinonasal Polyposis and Sinusitis

Recently, leukotrienes have been implicated in the mediation of bronchoconstriction and inflammatory changes in asthma. Leukotriene levels have also been shown to be elevated in patients with asthma as well as in those with sinonasal polyposis and sinusitis. The leukotriene synthesis inhibitor zileuton and the leukotriene receptor antagonist zafirlukast have been shown to produce subjective and objective improvements in patients with mild to moderate asthma. Given these findings, we evaluated the efficacy of these two medications in controlling sinonasal polyposis and their associated symptoms.

We treated 40 patients diagnosed with sinonasal polyposis and sinusitis with either zileuton or zafirlukast. No other change was made in their standard therapy. Outcome measures included subjective interviews and questionnaire responses, as well as office endoscopic examinations and chart reviews.

At study's end, 36 patients were available for evaluation. Twenty-six had taken zafirlukast, five had taken zileuton, and five others had switched from zafirlukast to zileuton. Overall, 26 patients (72%) experienced subjective improvement in their symptomatology after starting their medication. Statistically significant improvement was noted with respect to headache, facial pain and pressure, ear discomfort, dentalgia, purulent nasal discharge, postnasal drip, nasal congestion and obstruction, olfaction, and fever. An objective alleviation, or at least stabilization, of sinonasal polyposis was seen in 50% of the patients. Four patients (11%) discontinued their medication because of side effects.

We conclude that antileukotrienes might play a significant role in controlling polyposis and symptoms secondary to sinonasal disease, and they might be a viable alternative to long-term oral steroid therapy and repeated surgical debridement.

New perspectives for asthma treatment: anti-leukotriene drugs

Leukotrienes are synthesized by different cells, including eosinophils, neutrophils, basophils, lymphocytes, macrophages, and mast cells. Cysteinyl leukotrienes (LTC4, LTD4, and LTE4) are the most important leukotrienes in the pathogenesis of asthma. Pharmacologically, there are two different ways of blocking the action of leukotrienes: inhibiting their production by blocking 5-lipoxygenase or its activating protein, 5-lipoxygenase-activating protein (FLAP), (inhibitors) or by blocking their receptors (antagonists). The available antagonists are, for the moment, directed against the one receptor demonstrated to play a role in asthma symptoms, CysLT1, and they act in a competitive way. The only marketed 5-lipoxygenase inhibitor is zileuton (Zyflo). CysLT1 antagonists, currently on the pharmaceutical market in some countries, are zafirlukast (Accolate), pranlukast (Ultair, Onon), and montelukast (Singulair). Undoubtedly, drugs acting on leukotrienes constitute a new pharmacologic class in the therapeutic armamentarium for the management of asthma. From the pediatric point of view, montelukast is currently the most interesting drug of the group to date because of published trials in patients as young as 6 yr of age. At present, zafirlukast is only approved for use in patients 12 yr of age and older, although we understand that applications are likely to extend the age range into childhood shortly. However, more experience is necessary to establish a definite place for both leukotrienes in the step-by-step asthma treatment. New comparative studies (with sodium cromoglycate and inhaled steroids), which will probably be published in the near future, as well as studies on the use of montelukast in the treatment of children under 6 yr of age will add crucial information to our knowledge, and help to identify an appropriate use in the therapeutic algorithm. Montelukast will not be a substitute for inhaled corticosteroids or beta-agonists, although it may act as a 'sparing drug' (which might help tapering of steroids in some instances). Its role in exercise-induced asthma seems promising. Although its more widespread use could highlight low-frequency adverse effects, its apparent excellent tolerability is an additional advantage for the drug. Patients' preference for a twice-daily dosage over the inhaled medication, resulting in a better compliance, is relatively well established, at least for zafirlukast in adults, and these findings can probably be extended to montelukast, which only requires once-daily dosing in children.

Long-term safety and efficacy of zafirlukast in the treatment of asthma: interim results of an open-label extension trial

BACKGROUND

Current guidelines recommend anti-leukotriene agents as alternative treatments for mild persistent asthma; however, information on their long-term safety and efficacy is needed.

OBJECTIVE

To evaluate long-term safety and efficacy of and compliance with oral zafirlukast (Z; 20 mg BID) during the first 39 weeks of ongoing, multicenter, open-label extension (OLE) of a previously reported 13-week, randomized (2:1), double-blind (DB), placebo (P)-controlled trial in mild-to-moderate asthmatic patients treated previously with beta2-agonists alone.

METHODS

Patients (12 to 76 years; FEV1 > or = 55% predicted) elected to enter OLE after completing the DB trial. Safety evaluated by adverse events (AEs), laboratory tests, and physical and electrocardiographic examinations. Efficacy assessed by spirometry measurements [FEV1, FEV1 % predicted, personal-best (post-bronchodilator) FEV1] and treatment failure rates. Compliance was calculated as percentage of treatment dispensed. After a visit at OLE week 3 (week 16), patients had visits every 12 weeks.

RESULTS

A total of 443 patients (nz-->z = 310, np-->z = 133) entered the OLE. Results through the OLE period showed that 80% of patients overall reported AEs. Of patients randomized to Z and P during DB period, 68% and 67%, respectively, reported AEs during quarter I (Q1); percentage of Z-treated patients reporting AEs during the OLE ranged from 66% (Q2) to 44% (Q4). Review by quarters showed occurrence of AEs in Z-treated groups (Q2-4) was similar to that in P group (Q1). Compared with baseline (week 0), modest yet significant improvements (P < or = .02) in all spirometry measurements were noted in Z --> Z and P --> Z groups at OLE week 3, with sustained effects noted during OLE period. Treatment failure rates during OLE ranged from 7.2% (Q2) to 3.3% (Q4). Mean compliance ranged from 98% (OLE week 3) to 95% (OLE week 39).

CONCLUSIONS

Long-term treatment with zafirlukast was safe and well tolerated in asthmatic patients. Sustained efficacy and asthma control and good compliance were observed over extended treatment period. Results demonstrate long-term safety and effectiveness of and compliance with this anti-leukotriene agent.

Asthma and leukotrienes: antileukotrienes as novel anti-asthmatic drugs

Antileukotriene drugs inhibit the formation or action of leukotrienes, which are potent lipid mediators generated from arachidonic acid in lung tissue and inflammatory cells. The leukotrienes were discovered in basic studies of arachidonic acid metabolism in leucocytes 20 years ago and were found to display a number of biological activities which may contribute to airway obstruction. Clinical studies with antileukotriene drugs have indeed demonstrated that leukotrienes are significant mediators of airway obstruction evoked by many common trigger factors in asthma. Moreover, treatment trials have established that this new class of drugs has beneficial anti-asthmatic properties, and several antileukotrienes have recently been introduced as new therapy of asthma. This communication presents an overview of the biosynthesis of leukotrienes, their biological effects and clinical effects of antileukotrienes in the treatment of asthama.

A leukotriene receptor antagonist, ONO-1078, modulates drug sensitivity and leukotriene C4 efflux in lung cancer cells expressing multidrug resistance protein

ONO-1078 is a new class of peptide leukotriene receptor antagonist, and multidrug resistance protein (MRP) is a membrane tranporter of multiple anticancer drugs and endogenous leukotriene C4 (LTC4). We investigated the effects of ONO-1078 on drug sensitivity and LTC4-efflux in MRP-expressing lung cancer cells. Drug sensitivity, intracellular vincristine accumulation, and intracellular and extracellular LTC4 concentrations were measured with or without ONO-1078. The effect of ONO-1078 on MRP-mediated calcein-efflux was determined by flow cytometry. ONO-1078 (1 to 10 microM) dose-dependently enhanced the sensitivity of NCI-H520 cells to vincristine with the reduced accumulation, and also enhanced the sensitivity to doxorubicin and etoposide. ONO-1078 inhibited both LTC4- and calcein-efflux from the cells with increased intracellular accumulations. Our findings indicate that ONO-1078 modulates multidrug resistance and inhibits LTC4-efflux in lung cancer cells, by inhibition of MRP function.

Tubulointerstitial nephritis induced by the leukotriene receptor antagonist pranlukast

A 7-year-old boy with asthma was receiving the leukotriene receptor antagonist pranlukast (Ultair; SmithKline Beecham; Pittsburgh) as part of an open-label clinical trial. The patient's asthma improved, and he remained asymptomatic; but routine study evaluations 9 to 12 months into therapy showed microhematuria, proteinuria, glucosuria, anemia, and renal insufficiency. Renal biopsy demonstrated changes classic for acute allergic tubulointerstitial nephritis (ATIN), with mixed interstitial inflammatory infiltrate including eosinophils. Within 6 months of pranlukast withdrawal, anemia resolved and urinary sediment and renal function normalized. The case demonstrates that hypersensitivity reaction to pranlukast and resultant ATIN is possible, and that periodic urine testing in patients receiving pranlukast should be considered.

Effects of LTD4 on human airway smooth muscle cell proliferation, matrix expression, and contraction In vitro: differential sensitivity to cysteinyl leukotriene receptor antagonists

The cysteinyl leukotrienes (CysLTs) mimic many of the features of asthma and are implicated in its pathophysiology. Little, however, is known about the effects of the CysLTs on airways remodeling. In this study the effects of leukotriene D4 (LTD4) on human airway smooth muscle (HASM) cell proliferation and expression of extracellular matrix proteins were investigated. LTD4 (0.1-10 microM) alone had no effect on DNA synthesis in HASM. LTD4, however, markedly augmented proliferation induced by the mitogen, epidermal growth factor (EGF, 1 ng/ml). The potentiating effect of LTD4 (1 microM) on EGF-induced DNA synthesis was abolished by pranlukast (1 microM) or pobilukast (30 microM), but unaffected by zafirlukast (1 microM). In contrast, pranlukast (pKB = 6.9), pobilukast (pKB = 7.0), and zafirlukast (pKB = 6.5) had equivalent potencies for inhibition of LTD4-induced contraction in human bronchus. LTD4 (0.1 or 10 microM) did not increase the total messenger RNA expression of the extracellular matrix proteins (pro-alpha[I] type I or alpha1[IV] type IV collagen), elastin, biglycan, decorin, and fibronectin, and did not influence tumor growth factor-beta (10 ng/ml)-induced effects on the expression of these proteins in HASM cells. These data indicate that LTD4 augments growth factor-induced HASM proliferation but does not alter the expression of various extracellular matrix components. The observed differences in sensitivity to the antagonists suggests that the former phenomenon may be mediated by a CysLT receptor distinct from that which mediates LTD4-induced HASM contraction. Collectively, these results provide preliminary evidence that CysLTs may play a role in airways remodeling in asthma.

Effects of the cysteinyl leukotriene receptor antagonists pranlukast and zafirlukast on tracheal mucus secretion in ovalbumin-sensitized guinea-pigs in vitro

1. We investigated the inhibitory effects of the cysteinyl leukotriene (CysLT1) receptor antagonists, pranlukast and zafirlukast, on 35SO4 labelled mucus output, in vitro, in guinea-pig trachea, induced by leukotriene D4 (LTD4) or by antigen challenge of sensitized animals. Agonists and antagonists were administered mucosally, except in selected comparative experiments where drugs were administered both mucosally and serosally to assess the influence of the epithelium on evoked-secretion. 2. LTD4 increased 35SO4 output in a concentration-related manner with a maximal increase of 23 fold above controls at 100 microM and an approximate EC50 of 2 microM. Combined mucosal and serosal addition of LTD4 did not significantly affect the secretory response compared with mucosal addition alone. Neither LTC4 nor LTE4 (10 microM each) affected 35SO4 output. Pranlukast or zafirlukast significantly inhibited 10 microM LTD4-evoked 35SO4 output in a concentration-dependent fashion, with maximal inhibitions of 83% at 10 microM pranlukast and 78% at 10 microM zafirlukast, and IC50 values of 0.3 microM for pranlukast and 0.6 microM for zafirlukast. Combined mucosal and serosal administration of the antagonists (5 microM each) gave degrees of inhibition of mucosal-serosal 10 microM LTD4-evoked 35SO4 output similar to those of the drugs given mucosally. Pranlukast (0.5 microM) caused a parallel rightward shift of the LTD4 concentration-response curve with a pKB of 7. Pranlukast did not inhibit ATP-induced 35SO4 output. 3. Ovalbumin (10-500 microg ml(-1) challenge of tracheae from guinea-pigs actively sensitized with ovalbumin caused a concentration-related increase in 35SO4 output with a maximal increase of 20 fold above vehicle controls at 200 microg ml(-1). The combination of the antihistamines pyrilamine and cimetidine (0.1 mM each) did not inhibit ovalbumin-induced 35SO4 output in sensitized guinea-pigs. Neither mucosal (10 microM or 100 microM) nor mucosal-serosal (100 microM) histamine had any significant effect on 35SO4 output. 4. Pranlukast or zafirlukast (5 microM each) significantly suppressed ovalbumin-induced secretion in tracheae from sensitized guinea-pigs by 70% and 65%, respectively. 5 We conclude that LTD4 or ovalbumin challenge of sensitized animals provokes mucus secretion from guinea-pig trachea in vitro and this effect is inhibited by the CysLT1 receptor antagonists pranlukast and zafirlukast. These antagonists may be beneficial in the treatment of allergic airway diseases in which mucus hypersecretion is a clinical symptom, for example asthma and allergic rhinitis.