Leukotriene receptor antagonists and related compounds.

Leukotrienes (LTs), lipid mediators of inflammation, have proved to be important biochemicals involved in the symptoms and physiological changes of asthma. In the past year and a half, the development of three new drugs that modulate the LT pathway has been completed. The first subclass of these drugs, leukotriene receptor antagonists (LTRA) (zafirlukast and montelukast), blocks the interaction of the cysteinyl form of the LTs with the cell type bearing the receptor. The second subclass, the 5-lipoxygenase (5-LO) inhibitors (zileuton) inhibits the 5-LO enzyme, which prevents the formation of both cysteinyl LTs and LTB4. The LT modulators have shown efficacy in inhibiting the physiological changes occurring after allergen, acetylsalicylic acid and exercise challenge in asthmatics. In addition, they have shown efficacy in improving symptoms, beta-agonist use and forced expiratory volume in 1 s (FEV1) in chronic, 'day-to-day' asthma in patients with mild disease. Comparison studies with low doses of inhaled corticosteroids suggest that LT modulators may have similar effects on symptom scores and beta-agonist use, but have lesser effects on FEV1. Finally, emerging data suggest that these drugs are beneficial in decreasing the dose of inhaled corticosteroids necessary to control more moderate to severe asthma. While long term studies will be helpful in determining the 'disease modifying' effects of these drugs, data suggest that these drugs are useful in the treatment of a broad range of asthmatic patients.