Efalizumab ['Xanelim'], a humanised anti-CD11a monoclonal antibody that prevents T cell activation, is well tolerated and highly effective in the treatment of moderate-to-severe plaque psoriasis, according to updated results from two pivotal phase III trials presented at the 60th annual meeting of the American Academy of Dermatology (AAD) [New Orleans, US; February 2002]. Combined results from these studies showed that an improvement of ≥ 75% in Psoriasis Area and Severity (PASI) score ('response') was achieved in 27.6-29.2% of efalizumab recipients, compared with 3.4% of patients given placebo. Furthermore, rapid relief from psoriasis symptoms was reported, with improvements noted after administration of the second dose of efalizumab. In extensions of both studies, increased response rates were achieved when the duration of therapy was increased from 12 weeks to 24 weeks. Administration of efalizumab every second week was also shown to be sufficient to maintain responses in patients who had PASI score improvements of ≥ 75% in the initial treatment period.