Licofelone [ML 3000], a novel pyrrolizine derivative, is as effective as naproxen and celecoxib in the treatment of osteoarthritis of the knee, but has a more favourable tolerability profile, according to studies presented at the annual congress of the European League Against Rheumatism (EULAR) [Lisbon, Portugal; June 2003]. In separate studies, licofelone produced improvements in pain scores and other efficacy measures that were comparable to those achieved in patients treated with celecoxib and naproxen. However, licofelone was better tolerated, particularly with respect to gastrointestinal adverse events. The improved safety profile of licofelone may be due to its unique mechanism of action; in addition to inhibiting cyclo-oxygenase (COX)-1 and COX-2, licofelone suppresses 5-lipoxygenase (5-LOX) activity.