New therapeutic approaches

New therapeutic approaches to asthma involve either improvements in existing classes of drug, or the development of novel drugs. Over the last 20 years there have been no new types of drug introduced, although several new classes of compound are now under development. Improvements in existing bronchodilators include long-acting inhaled beta 2-agonists, methyl xanthines with a reduced side effect profile and M3-selective anticholinergics. New bronchodilators include K+ channel activators and selective phosphodiesterase inhibitors. Corticosteroids are the most effective anti-inflammatory drugs and there are attempts to develop inhaled steroids with greater topical potency or increased systemic metabolism, or to develop drugs which retain the anti-inflammatory effects of steroids without side effects. Steroids are probably effective in asthma by inhibiting the synthesis of cytokines and drugs which inhibit cytokine synthesis or receptors are now being sought. Inhibitors of mediator synthesis and receptors currently under development and leukotriene D4-antagonists are promising. Immunomodulatory drugs such as methotrexate, cyclosporin A and gold may be useful in more severe asthma, but drugs which modulate the immune abberation of asthma more specifically may be of more widespread use in the future. There is no immediate prospect of a cure for asthma and a drug which may be taken orally once daily and has no side effects would be ideal.