WASHINGTON, Nov. 12 -- The novel agent Actemra (tocilizumab), an investigational a humanized monoclonal antibody is safe and effective in children with systemic juvenile idiopathic arthritis, a Japanese researcher said here.

In a prospective, randomized phase III trial, 90% of children had an improvement of 50% over 12 weeks of therapy with Actemra, which blocks the interleukin-6 receptor, according to Shumpei Yokota, M.D., of Yokohama City University School of Medicine.

"It works," Dr. Yokota said before he presented data from the study at the American College of Rheumatology meeting.

He noted that the drug is now being tested in various indications in adults as well as in children but has so far been approved only for Castleman's Disease and only in Japan.