Acute bronchodilation with an intravenously administered leukotriene D4 antagonist, MK-679

Effects of using montelukast during acute wheezing attack in hospitalized preschool children on the discharge rate and the clinical asthma score

BACKGROUND

In chronic asthma treatment, leukotriene receptor antagonists have been recommended, but it is not clear whether montelukast can be used in acute recurrent wheezing attacks in children.

OBJECTIVE

To investigate the safety and effectiveness of oral montelukast in addition to standard treatment in hospitalized children aged between 6 and 72 months with acute recurrent wheezing attacks.

METHOD

One hundred patients aged between 6 and 72 months who had wheezing attacks with clinical asthma scores (CAS) ≥3 and were hospitalized were included in this randomized, double-blind, placebo-controlled, parallel-group clinical trial. All the patients included in the study were given 0.15 mg/kg (maximum 5 mg) nebulized salbutamol (8 L/min and with 100% O₂ ) with 4 h of intervals, 1 mg/kg prednisolone (maximum 5 days), nebulized ipratropium bromide (total eight doses) with 6 h of intervals. In addition to this treatment, one group received 4 mg montelukast, and the other group received a placebo. The CAS of the patients were evaluated with 4-h intervals.

RESULTS

Total hospital length of stay (LOS) was not different between the montelukast and placebo groups (p = 0.981). There was no statistically significant difference between the two treatment groups in terms of discharge time, CAS, and oxygen saturation (p ≥ 0.05).

CONCLUSION

Adding montelukast to standard treatment in patients hospitalized for moderate-to-severe wheezing attacks did not affect hospital LOS and CAS.

Effect of selective cysteinyl leukotriene receptor antagonists on airway inflammation and matrix metalloproteinase expression in a mouse asthma model

BACKGROUND

Cysteinyl leukotrienes (CysLTs) play a major role in the pathogenic changes of airway inflammation in asthma treatment. The matrix metalloproteinase (MMP) family, especially MMP-9 and MMP-2 levels, can reflect the status of airway remodeling. This study was undertaken to determine the role of a specific CysLT receptor antagonist in inhibition of airway inflammation and reversal of airway remodeling.

METHODS

Ovalbumin (OVA)-sensitized BALB/c mice were fed with a specific leukotriene receptor antagonist (MK-679), prednisolone or placebo from Days 15 to 27. Airway hyperreactivity, bronchoalveolar lavage fluid (BALF), and sera were analyzed. Pulmonary histology was obtained, and the levels of MMP-2 and MMP-9 in BALF were measured.

RESULTS

The OVA-sensitized mice developed significant airway inflammatory responses, including extensive eosinophils trafficking into BALF and lung interstitium, goblet cell hyperplasia, mucus hypersecretion, elevated serum immunoglobulin (Ig) E, and decreased level of serum IgG2a. Administration of MK-679 could reduce airway inflammation but was not as effective as prednisolone. However, MK-679 was more effective than prednisolone for reversing subepithelial fibrotic and myofibrotic reactions of airway remodeling. The levels of MMP-2 and -9 in BALF were proportional to the extent of airway remodeling, which can reflect the effects of treatment. Both prednisolone and MK-679 reverse airway hyperresponsiveness induced by OVA-sensitized mice.

CONCLUSION

Cysteinyl leukotriene receptor plays a more important role than CysLT in the pathogenesis of allergic airway inflammation. MMP-2 and -9 may be more sensitive indicators of airway remodeling.

Using guinea pigs in studies relevant to asthma and COPD

The guinea pig has been the most commonly used small animal species in preclinical studies related to asthma and COPD. The primary advantages of the guinea pig are the similar potencies and efficacies of agonists and antagonists in human and guinea pig airways and the many similarities in physiological processes, especially airway autonomic control and the response to allergen. The primary disadvantages to using guinea pigs are the lack of transgenic methods, limited numbers of guinea pig strains for comparative studies and a prominent axon reflex that is unlikely to be present in human airways. These attributes and various models developed in guinea pigs are discussed.

Anti-leukotrienes as novel anti-inflammatory treatments in asthma

The anti-leukotrienes are effective asthma treatments. This observation demonstrates, by inference, that leukotrienes are important in the biology of asthma. The clinical data also indicate, however, that the leukotrienes are not the sole mediator of asthmatic responses as patients with asthma are totally free of airway obstruction or asthma symptoms when they are treated with these agents.

Effects of oral montelukast on airway function in acute asthma

Montelukast, a specific cysteinyl leukotriene receptor antagonist, has been shown to improve pulmonary function within 1 h of ingestion. This study was undertaken to compare the effects on peak expiratory flow rate (PEFR) of oral montelukast added to intravenous steroid, intravenous steroid alone and placebo during the 24 h period following administration. Seventy asthmatic patients (FEV1 40-80% predicted and > or = 15% improvement after inhaled beta agonist) were enrolled in a single blind study to receive oral montelukast (10 mg) plus intravenous prednisolone (1 mg/kg), intravenous prednisolone (1 mg/kg) or placebo in a randomised fashion. The patients received one ofthe above three groups of medication before any other treatments. This was immediately followed by the aerosol treatments of 100 mcg of terbutaline sulphate divided into three doses during 1 h as described in the consensus statement. Thereafter, patients were observed for 24 h to document the effects on PEFR, Borg dyspnoea score and need for rescue medication. The primary end point was percentage change at different time points. Secondary end points were Borg dyspnoea score and use of rescue medication. Compared with placebo, montelukast added to the prednisolone group and the prednisolone alone group had significant percentage change from baseline in PEFR in the entire 24 h period (P<0.05). The difference in PEFR between montelukast plus prednisolone group and prednisolone group favoured the montelukast plus prednisolone group but did not reach statistical significance. Furthermore, montelukast plus prednisolone group required less inhaled short-acting beta agonistthan other two groups. The results of this study indicate that adding montelukast to steroid in acute asthma may have some additive improvement in lung functions.

Lung function improvement in smokers suffering from COPD with zafirlukast, a CysLT(1)-receptor antagonist

The present study was designed to evaluate the bronchodilating role of zafirlukast, a CysLT(1)receptor antagonist, at the standard dosage currently recommended in the marketing of this agent in smokers with COPD. The study was performed using a double-blind, cross-over, randomized design and was conducted on 2 non-consecutive days. Sixteen outpatients suffering from stable COPD received 40 mg oral zafirlukast, or placebo. Lung function was controlled before drug administration and 30, 60, 120, 180, 240 min thereafter. At the end of the 4-h period, each patient received 400 microg inhaled salbutamol and spirometric testing was performed 30 min later. Zafirlukast, but not placebo, produced a significant (P<0.05) bronchodilation between 30 min and 4 h following administration, with a maximum mean increase in FEV(1)of 0.134 l (11.2%) above baseline after 2 h. Nine of 16 patients showed an increase in FEV(1)of at least 15% above baseline after zafirlukast. The maximum mean increase in FEV(1)after zafirlukast in these subjects, who were considered responders, observed after 2 h, was 0.221 (19.4%). The mean difference of post-salbutamol FEV(1)values after zafirlukast and placebo (-0.036 l) was not significant (P<0.05). In responders, the mean of differences in pre- and post-salbutamol FEV(1)values after zafirlukast was 0.077 l, whereas the mean of differences between post-salbutamol values after zafirlukast and those after placebo was -0.064 l. The mean AUC(0-4 h)for all patients was 0.121 l for placebo and 0.385 l for zafirlukast. The difference between the placebo and zafirlukast AUC(0-4 h)was significant (P<0.05). The individual FEV(1)AUC(0-4 h)after zafirlukast were higher than those after placebo in 12 out of 16 patients. These findings suggest that cysteinyl leukotrienes might be one of the causes of persistent bronchoconstriction in COPD, at least in several smokers, but do not confirm the hypothesis that the effects of zafirlukast and salbutamol are independent and additive.

Drug therapy approaches in the treatment of acute severe asthma in hospitalised children

Acute severe paediatric asthma remains a serious and debilitating disease throughout the world. The incidence and mortality from asthma continue to increase. Early, effective and aggressive outpatient therapy is essential in reducing symptoms and preventing life-threatening progression. When complications occur or when the disease progresses to incipient respiratory failure, these children need to be managed in a continuous care facility where aggressive and potentially dangerous interventions can be safely instituted to reverse persistent bronchospasm. The primary drugs for acute severe asthma include oxygen, corticosteroids, salbutamol (albuterol) and anticholinergics. Second-line drugs include heliox, magnesium sulfate, ketamine and inhalational anaesthetics. Future therapies may include furosemide, leukotriene modifiers, antihistamines and phosphodiesterase inhibitors. This review attempts to explore the multitude of medications available with emphasis on pharmacology and pathophysiology.

Current treatment of asthma--focus on leukotrienes

Since their identification in 1979, the cysteinyl leukotrienes (cysLTs) have been shown to be prominent in many inflammatory conditions, including asthma, allergic rhinitis, rheumatoid arthritis, psoriasis, cystic fibrosis and inflammatory bowel disease. They are potent pro-inflammatory agents, as well as causing bronchoconstriction, and undoubtedly have a role in asthma. The cysLTs are products of arachidonic acid metabolism and have been shown to have effects via a cysteinyl leukotriene receptor (CysLTR1) on vascular permeability, mucus production, chemotaxis and bronchial smooth muscle. Their detection in certain body fluids in allergic, aspirin-sensitive and exercise-induced asthma is well documented and potential roles in pathogenesis, proposed. The development of agents affecting production or action offers an exciting new approach to the treatment of asthma. Two approaches to antileukotriene therapy have been developed: blocking their production by inhibiting the action of 5-lipoxygenase enzyme or blocking the CysLTR1. Both approaches have been tried in studies in asthma and overall the results are encouraging, with a decrease in both daytime and nocturnal symptoms, a decrease in additional beta 2 agonist usage and improvement in lung function. The changes, however, are small in some studies. This may be a reflection of disease severity in the study subjects, but of note is a heterogeneity of response to these treatments that may be genetically determined. Antileukotriene therapy has been shown to have an effect in specific types of asthma where the role of cysLTs seems well established--aspirin-sensitive/intolerant asthma and exercise-induced asthma. Longer term studies are needed in other areas such as severe asthma and chronic persistent asthma in both children and adults to provide evidence for the appropriate placement of antileukotriene treatment in current asthma guidelines, in comparison with other established treatments.

Comparison of the effects of intravenous and oral montelukast on airway function: a double blind, placebo controlled, three period, crossover study in asthmatic patients

BACKGROUND

Montelukast, a leukotriene receptor antagonist, improves parameters of asthma control including forced expiratory volume in one second (FEV(1)) when given orally to patients aged six years or older. This study was undertaken to compare the effect on FEV(1) of intravenous and oral montelukast and placebo during the 24 hour period following administration.

METHODS

Fifty one asthmatic patients (FEV(1) 40-80% predicted and > or =15% improvement after inhaled beta agonist) were enrolled in a double blind, single dose, three period, crossover study to receive intravenous montelukast (7 mg), oral montelukast (10 mg), or placebo in a randomised fashion. The primary end point was area under the curve (AUC)(0-24 h) of the percentage change from baseline in FEV(1). Additional end points were maximum percentage change in FEV(1) and percentage change at different time points.

RESULTS

Compared with placebo, intravenous and oral montelukast significantly increased the AUC(0-24 h) (means of 20.70%, 15.72%, and 7.75% for intravenous, oral and placebo, respectively; no statistical difference between intravenous and oral). The difference in least square means from placebo for intravenous montelukast was 13.27% (95% CI 7.07 to 19.46), p<0.001 and for oral montelukast was 7.44% (95% CI 1.20 to 13.68), p = 0.020. The maximum percentage change in FEV(1) was not significantly different for intravenous and oral montelukast (difference in least square means 6.78% (95% CI -0.59 to 14.15), p = 0.071). The mean percentage change in FEV(1) for intravenous montelukast was greater than for oral montelukast within the first hour (15.02% vs 4.67% at 15 min, p< or =0.001; 18.43% vs 12.90% at one hour, p<0.001 for intravenous and oral montelukast, respectively (placebo 3.05% at 15 minutes, 7.33% at one hour). Intravenous and oral montelukast were similar to placebo in the frequency of adverse events.

CONCLUSIONS

The onset of action for intravenous montelukast was faster than for oral montelukast and the improvement in airway function lasted over the 24 hour observation period for both treatments. Although not well understood, there was a trend toward a greater improvement in FEV(1) with intravenous than with oral montelukast. These findings suggest that leukotriene receptor antagonists should be investigated as a treatment for acute severe asthma.

Effect of leukotriene and thromboxane antagonist on propranolol-induced bronchoconstriction

beta-adrenoreceptor blockers such as propranolol provoke bronchoconstriction only in asthmatic patients. Although cysteinyl leukotrienes (cLTs) and thromboxane A2 (TXA2) have been proposed to be involved in the pathophysiology of asthma, the role of these lipid mediators in propranolol-induced bronchoconstriction (PIB) has not been evaluated in asthmatics. This study was conducted to elucidate it. Nine patients with stable asthma, in whom a 20% or more decrease in FEV(1) occurred by inhalation of 20 mg/ml or less propranolol, participated in this study. A cLT antagonist, pranlukast (225 mg twice a day), a TXA2 antagonist, seratrodast (80 mg once a day), and placebo were orally given for 2 wk in a randomized and double-blinded manner. The provocative concentration of propranolol causing a 20% fall in FEV(1) (PC(20)) was determined on the last day of each 2-wk treatment. Pranlukast, but not seratrodast, tented to increase FEV(1) compared with placebo (2.14 +/- 0.29 versus 1.99 +/- 0.34 L, p = 0.0543). Pranlukast or seratrodast did not affect the PC(20) in comparison with placebo. We conclude that cLTs or TXA2 are not involved in PIB of asthmatics.

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.

Leukotrienes as mediators of airway obstruction

The cysteinyl leukotrienes are potent mediators of airway narrowing derived from the lipoxygenation of arachidonic acid and the adduction of glutathione to this eicosanoid backbone. In lower animals and humans, the cysteinyl leukotrienes are among the most potent airway contractile substances ever identified. Furthermore, these moieties can be recovered from the urine during induced or spontaneous asthma attacks. Most important, inhibition of the synthesis of the leukotrienes or prevention of their action at the CysLT1 receptor is associated with an improvement in the airway dysfunction that occurs in both induced and spontaneous asthma. These data indicate that the cysteinyl leukotrienes have a clinically significant role in the airway obstruction that characterizes asthma.

The prospects for long-term intervention in asthma with antileukotrienes

The antileukotriene drugs are the first new therapeutic agents approved for the treatment of asthma in more than 20 years. The currently available compounds are orally active and either prevent the cysteinyl leukotrienes from binding to and activating the cysLT-1 receptor in the lung (leukotriene receptor antagonists, LTRAs) or inhibit leukotriene synthesis (leukotriene synthesis inhibitors, LTSIs). The antileukotrienes acutely bronchodilate the airways of patients with baseline bronchoconstriction, although usually not as well as beta-agonists. When used regularly they produce rapid improvements of pulmonary function and symptoms in patients with mild-to-moderate asthma, and probably of those with more severe asthma as well, which persists for the duration of treatment. Yet, individual responses to the antileukotrienes are variable and not predictable based on clinical criteria. Recent studies suggest they reduce asthmatic airway inflammation. The few comparator studies with other asthma medications indicate they are equal or more effective than cromolyn but equal or less effective than low-to-moderate doses of inhaled corticosteroids. Initial experience with the antileukotrienes reveals limited toxicity and a favourable therapeutic-to-toxic ratio. The exact role of the antileukotrienes in the treatment of asthma remains to be determined, as does the relative potency of the various agents.

A risk-benefit assessment of antileukotrienes in asthma

The antileukotriene drugs are the first new therapeutic agents approved for the treatment of asthma in more than 20 years. The currently available compounds are orally active and either prevent the cysteinyl leukotrienes from binding to and activating the cysLT-1 receptor in the lung (leukotriene receptor antagonists) or inhibit leukotriene synthesis (leukotriene synthesis inhibitors). Studies performed in individuals without asthma and patients with asthma reveal that antileukotrienes prevent the bronchoconstriction produced by exercise, cold-air, allergen, aspirin (acetylsalicylic acid) and sulphur dioxide. Except for the setting of aspirin sensitivity where the antileukotrienes are nearly uniformly effective, individual responses to them are variable with complete protection in some, no protection in others and a modest degree of protection in the majority. The antileukotrienes bronchodilate the airways of patients with baseline bronchoconstriction, although usually not as well as beta-agonists. When given for weeks to months they rapidly improve pulmonary function and symptoms in patients with mild-to-moderate asthma, and probably in patients with more severe asthma as well, and these improvements persist for the duration of treatment. Here too, their beneficial effects are variable and not predictable based on clinical criteria. Recent studies suggest they can reduce asthma-induced airway inflammation and are equal or more effective than sodium cromoglycate, but equal or less effective than low-to-moderate dosages of inhaled corticosteroids. Initial experience with the antileukotrienes reveals limited toxicity and what appears to be a favourable therapeutic-to-toxic ratio. However, exposure of more patients with differing characteristics for longer periods of time is needed to substantiate this initial impression. The exact role of the antileukotrienes in the treatment of asthma remains to be determined, as does the relative potency of the various agents.

A placebo-controlled, dose-ranging study of montelukast, a cysteinyl leukotriene-receptor antagonist. Montelukast Asthma Study Group

BACKGROUND

The cysteinyl leukotrienes are important mediators of bronchial asthma. The clinical effect of montelukast, a potent cysteinyl leukotriene-receptor antagonist, was investigated in a randomized, placebo-controlled, multicenter, parallel-group, dose-ranging study.

METHODS

After a 3-week, single-blind, placebo run-in period, 343 asthmatic patients (FEV1 40% to 80% of the predicted value with an improvement in FEV1 of at least 15% [absolute value] after receiving inhaled beta-agonists on at least two occasions) were randomly assigned to one of six treatment groups: placebo; 10, 100, or 200 mg once daily montelukast in the evening; or 10 or 50 mg twice daily montelukast for a 6-week, double-blind treatment period followed by a 1-week placebo washout period. All patients used inhaled, short-acting beta-agonists as needed.

RESULTS

All montelukast doses caused similar and significant differences compared with placebo in asthma control endpoints. The least-square mean difference between pooled montelukast groups and placebo in the percentage change from baseline in morning FEV1 (10.30%; 95% CI: 5.56 to 15.04), as-needed beta-agonist use (-0.98 puffs; 95% CI: -1.53 to -0.44), morning peak expiratory flow rate (18.80 L/min; 95% CI: 8.62 to 28.98), physicians' and patients' global evaluations, and asthma-specific quality-of-life scores were all significant (p < or = 0.050). The incidence of adverse experiences was not dose related and was similar between placebo and montelukast treatment.

CONCLUSION

Montelukast caused a significant improvement in chronic asthma at an oral, once daily evening dose as low as 10 mg.

Inflammation, inflammatory mediators, and mediator antagonists in asthma

Asthma is an inflammatory disease that involves mast cells, antigen-presenting cells, eosinophils, neutrophils, and TH2-lymphocytes. These cells produce a broad array of mediators and cytokines that lead to the bronchoconstriction, mucosal edema, mucus secretion, and bronchial hyperresponsiveness that characterize asthma. Current guidelines for therapy recommend that all patients whose asthma is more severe than mild intermittent receive chronic treatment with drugs that interrupt this inflammatory cascade. Corticosteroids have been the gold standard for treatment, but a greater understanding of the specific cells and mediators involved in the pathogenesis of asthma has led to more focused, specific therapy. Pharmacologic agents that interrupt the synthesis of action of leukotrienes, and monoclonal antibodies directed against intracellular adhesion molecules or immunoglobulin E are examples of the new generation of specific targeted therapy for use in asthma.

Effect of pranlukast, a leukotriene receptor antagonist, in patients with severe asthma refractory to corticosteroids

We investigated the effect of pranlukast (ONO-1078), a cysteinyl leukotriene receptor antagonist, in 11 patients with severe bronchial asthma. The patients had been treated with 1600 micrograms/day of beclomethasone or 800-1600 micrograms/day of beclomethasone plus 2.5-20 mg/day of prednisolone, but remained symptomatic. After a 2-week baseline period, the patients received 225 mg of pranlukast twice daily for 8 weeks. Morning and evening peak expiratory flow rate (PEF) and symptom scores (cough, dyspnea, sleep) were recorded in an asthma diary. Ten patients completed the study. Symptom scores, especially dyspnea and sleep scores, and the number of rescue beta 2-agonist inhalations were significantly decreased. The morning PEF significantly improved from a mean baseline value of 311 to 341 L/min by the end of the study period. The evening PEF also improved, from 328 to 348 L/min, although the difference was not significant. These results suggest that pranlukast may be effective in treating patients with severe asthma who are refractory to corticosteroid therapy.

Effects of montelukast (MK-0476); a potent cysteinyl leukotriene receptor antagonist, on bronchodilation in asthmatic subjects treated with and without inhaled corticosteroids

BACKGROUND

Cysteinyl leukotriene release in association with airway inflammation is a feature of clinical asthma. The acute effects of montelukast (MK-0476), a potent, orally administered, specific cysteinyl leukotriene receptor antagonist, on airways obstruction was assessed in patients with mild to moderately severe asthma.

METHODS

Twenty two asthmatic subjects were randomised to receive montelukast, 100 mg or 250 mg, or placebo in a double blind, three period, crossover trial. Ten of the patients were using concomitant inhaled corticosteroids.

RESULTS

Montelukast increased the forced expiratory volume in one second (FEV1) from predose baseline values compared with placebo, the percentage point differences between montelukast and placebo being 8.6% (95% CI 3.6 to 13.6) and 8.5% (95% CI 3.5 to 13.5) for the 100 mg and 250 mg doses, respectively.

CONCLUSION

Single oral doses of montelukast 100 mg and 250 mg produced significant increases in FEV1 irrespective of the concurrent use of inhaled corticosteroids in asthmatic subjects with airflow limitation.

Montelukast causes prolonged, potent leukotriene D4-receptor antagonism in the airways of patients with asthma

Montelukast, a new specific oral cysteinyl LT3-receptor antagonist was evaluated for its activity in attenuating inhaled leukotriene D4 (LTD4) bronchoconstriction in patients with asthma. In two double-blind, placebo-controlled, randomized crossover studies, patients with mild asthma (forced expiratory volume in 1 second [FEV1] > or = 70%) were studied. In trial A, LTD4 challenge began 4 hours (peak plasma concentration) after a single dose of placebo or 5, 20, 100, and 250 mg montelukast. In trial B, and LTD4 challenge was started 20 hours after administration of placebo, 40 mg montelukast, or 200 mg montelukast. During each challenge, twofold increasing concentrations of LTD4 were inhaled until specific airways conductance (sGaw) decreased by at least 50% (PC50) or the highest concentration of LTD4 was inhaled. In trial A with all doses and in trial B with the 200 mg dose, bronchoconstriction was attenuated (50% fall in sGaw was not observed) up to the highest dose of LTD4 administered. In trial B, during the 40 mg period, only two of six patients exhibited a 50% fall in sGaw; PC50 ratios (montelukast 40 mg/placebo) were 18 and 45 in these two patients. These results indicate that montelukast is a highly potent and long-lasting antagonist of LTD4-induced bronchoconstriction in patients with asthma.

Inhibitory effect of thromboxane A2 synthetase inhibitor, DP-1904, on antigen-induced contraction of human lung parenchyma

BACKGROUND

Several mediators are released from mast cells during allergic reactions. These substances cause contraction of airway smooth muscles, increase the permeability of blood vessels, and enhance mucous secretion. Among these mediators, thromboxane A2 (TXA2) has a particularly strong bronchoconstrictive effect.

OBJECTIVES

We examined antigen-induced contraction of excised human lungs and the suppressive effects of TXA2 synthetase inhibitor on TXA2 release.

METHODS

Human lung parenchymal strips were subjected to passive sensitization with sera of 5+ RAST titer to the mite. They were suspended in magnus baths, to which buffer and 10(-4) to 10(-8) M of DP-1904, an inhibitor of TXA2 synthetase, were added. Following the measurement of TXB2 and leukotriene (LT) concentrations in each bath, parenchymal contraction was induced by the addition of a mite antigen. The concentration of TXB2 and LT was measured after contraction.

RESULTS

Antigen-induced release of TXB2 was significantly suppressed by DP-1904 in a concentration-dependent manner. DP-1904 did not inhibit parenchymal contraction and the release of LT.

CONCLUSIONS

Antigen-induced parenchymal contraction was not suppressed by inhibition of TXA2 release, suggesting that DP-1904 may not be effective in asthma.

Single dose pharmacokinetics, safety and tolerability of MK-0476, a new leukotriene D4-receptor antagonist, in healthy volunteers

MK-4076 or sodium 1-(1(R)-(3-(2-(7-chloro-2-quinolinyl)-(E)- ethenyl)phenyl) 3-(1-hydroxy-1-methylethyl)phenyl)propyl)thio)methyl) cycloproprane) acetate is a novel, potent, and specific LTD4-receptor antagonist. The safety, tolerability and plasma drug profiles of single oral doses of MK-0476 (capsules) were evaluated in 18 healthy male volunteers assigned to one of the two parallel 9-subject panels. Under fasting conditions, increasing single doses of 20 to 800 mg were administered in a first part of the study and in a second part, 200 mg MK-0476 was given either as a solution, under fasting conditions, or as capsules, after a standard breakfast. All volunteers completed the study. Side effects, reported by the investigator to be related to study drug, were mild and transient. No laboratory abnormalities were noted. In the evaluated dose range of MK-0476 (20 to 800 mg) the median value of tmax ranged from 2 to 4 h, while the apparent t1/2 value averaged 4 to 5 h. The median tmax value of the 200 mg capsule dose was not significantly different from the median tmax of the 200 mg oral solution dose indicating that neither disintegration nor dissolution is a rate-limiting step for the absorption of MK-0476 from capsules. There was a statistically significant increase in the AUC (geometric mean ratio of fed/fast was 2.52 with 95% confidence interval of 1.25, 5.06) and in Cmax (geometric mean ratio of fed/fast was 1.36 with 95% confidence interval of 0.60, 3.04) when MK-0476 was given together with a breakfast, suggesting an increase in bioavailability.(ABSTRACT TRUNCATED AT 250 WORDS)

Cysteinyl leukotrienes in asthma: old mediators up to new tricks

The cysteinyl leukotrienes have long been suspected to play a role in the pathogenesis of asthma. This speculation was based largely on their release in human lung following antigen challenge as well as their potent bronchoconstrictor activity. However, there is increasing evidence that the cysteinyl leukotrienes also produce several pro-inflammatory effects and alter the activity of neuronal pathways in the airways. Douglas Hay, Theodore Torphy and Bradley Undem review these recent data and discuss the therapeutic possibilities of cysteinyl leukotriene receptor antagonists and 5-lipoxygenase inhibitors.

Eicosanoids and asthma: an update

There have been significant advances in our understanding of the role of eicosanoids as mediators in inflammation since their discovery over 50 years ago. Our more recent understanding of asthma as an inflammatory disease has led to the appreciation of eicosanoids potentially being pivotal mediators in promoting some of the changes in asthma. Of particular importance are the cysteinyl LTs in producing bronchospasm and bronchial hyperresponsivenss, and PGE2 in modulating the bronchospastic and inflammatory response. Evidence from clinical studies suggests that other eicosanoids may also contribute, but their importance is secondary and their relative contributions vary between individuals. The development of new drugs based on our partial understanding of the role that eicosanoid mediators may play in asthma promises new approaches to the treatment of this common chronic inflammatory condition.

Clinical activity of leukotriene inhibitors

Data from the emerging clinical trials with compounds such as zileuton, ICI 204,219, Bay X1005, MK571, MK679, and MK591 are demonstrating the importance of the leukotrienes as mediators of asthma and possibly other diseases such as rheumatoid arthritis, psoriasis, and inflammatory bowel disease. One of the major questions facing the asthma community is how much improvement in the FEV1 is needed to improve the quality of life of the asthmatic patient. Comparing the various approaches to asthma treatment, there is typically 15-20% improvement in the lung function with inhaled steroids. Leukotriene interventions apparently will improve lung function to similar levels as with inhaled steroids, and thus may offer an alternative to steroids. Like the steroids, zileuton appears to also reduce the inflammatory cell influx into the antigen-challenged site, which may have the long-term effect of reversing some of the tissue alterations that occur as a result of the inflammation seen with asthma. Importantly, the reported experience to date has shown that the leukotriene modulators do not have the same side-effects as the current therapies, and thus offer the hope that both safe and effective treatment may be derived from this approach. The clinical data reported do not yet define a preferred approach to the modulation of leukotriene pathology. As more studies are published in other diseases the broad spectrum use of these inhibitors will become known.

Pharmacology of montelukast sodium (Singulair), a potent and selective leukotriene D4 receptor antagonist

Montelukast sodium (Singulair), also known as MK-0476 (1-(((1(R)-(3-(2-(7-chloro-2-quinolinyl)-(E)-ethenyl)phenyl)(3-2-(1- hydroxy-1-methylethyl)phenyl)propyl)thio)methyl)cyclopropane) acetic acid sodium salt, is a potent and selective inhibitor of [3H]leukotriene D4 specific binding in guinea pig lung (Ki 0.18 +/- 0.03 nM), sheep lung (Ki 4 nM), and dimethylsulfoxide-differentiated U937 cell plasma membrane preparations (Ki 0.52 +/- 0.23 nM), but it was essentially inactive versus [3H]leukotriene C4 specific binding in dimethylsulfoxide-differentiated U937 cell membranes (IC50 10 microM) and [3H]leukotriene B4 specific binding in THP-1 cell membranes (IC50 40 microM). Montelukast also inhibited specific binding of [3H]leukotriene D4 to guinea pig lung in the presence of human serum albumin, human plasma, and squirrel monkey plasma with Ki values of 0.21 +/- 0.08, 0.19 +/- 0.02, and 0.26 +/- 0.02 nM, respectively. Functionally, montelukast antagonized contractions of guinea pig trachea induced by leukotriene D4 (pA2 value 9.3; slope 0.8). In contrast, montelukast (16 microM) failed to antagonize contractions of guinea pig trachea induced by leukotriene C4 (45 mM serine-borate), serotonin, acetylcholine, histamine, prostaglandin D2, or U-44069. Intravenous montelukast antagonized bronchoconstriction induced in anesthetized guinea pigs by i.v. leukotriene D4 but did not block bronchoconstriction to arachidonic acid, histamine, serotonin, or acetylcholine. Oral administration of montelukast blocked leukotriene D4 induced bronchoconstriction in conscious squirrel monkeys, ovalbumin-induced bronchoconstriction in conscious sensitized rats (ED50 0.03 +/- 0.001 mg/kg; 4 h pretreatment), and also ascaris-induced early and late phase bronchoconstriction in conscious squirrel monkeys (0.03-0.1 mg/kg; 4 h pretreatment). A continuous i.v. infusion of montelukast (8 micrograms.kg-1.min-1) resulted in a 70% decrease in the peak early response and a 75% reduction of the late response to ascaris aerosol in allergic conscious sheep. Montelukast, a potent and selective leukotriene D4 receptor antagonist with excellent in vivo activity is currently in clinical development for the treatment of asthma and related diseases.

Clinical studies with agents active on the 5-lipoxygenase pathway

Leukotrienes may be considered asthmatic mediators. Compounds inhibiting their production and activity show promise in the treatment of asthma. Further clinical studies will determine the clinical usefulness of such agents.