By Liz Meszaros
PHILADELPHIA -- October 22, 2009 -- A novel Janus kinase (JAK) inhibitor, CP-660,550 (CP), may be effective in the treatment of rheumatoid arthritis (RA), researchers stated here at the according to a study presented here at the 2009 Annual Scientific Meeting of the American College of Rheumatology/Association of Rheumatology Health Professionals (ACR/ARHP).
Joel M. Kremer, MD, Albany Medical College, and the Center for Rheumatology, Albany, New York, presented the results of a 24-week, double-blind, placebo-controlled, phase 2B study here on October 20.
The study included 507 patients with RA. Patients were assigned to 1 of 7 dosing groups: CP at 1, 3, 5, 10, or 15 mg twice daily; CP 20 mg once daily; or placebo. All patients continued treatment with methotrexate throughout the study. Patients randomised to placebo and to the 1-, 3-, or 20-mg doses who did not have a decrease of 20% in tender and swollen joints (ACR20 response) by week 12 were given CP 5 mg twice daily for the duration of the study.
Clinical response was seen in all 6 doses of CP, and efficacy was seen at doses of 5 mg and higher by week 24. At this time, ACR20 responses were the greatest in the 5-mg (59.2%), 10-mg (66.2%), 15-mg (65.3%), and 20-mg (53.8%) doses, compared with placebo (34.8%).
ACR50 and ACR70 responses were greatest in the group receiving the 15-mg dose (46.7% and 30.7%, respectively). Remission rates were highest in the 5-, 10-, and 15-mg groups (31.0%, 31.5%, and 29.3%, respectively), compared with placebo (10.1%).
In all, 37.1% of patients (n = 188) had 896 treatment emergent adverse events. The most common of these were urinary tract infection (6.2%), headache (5.9%), diarrhoea (5.7%), nasopharyngitis (5.5%), and nausea (4.8%). These events were more common in the groups treated with the higher doses. Serious adverse events were observed in 21 patients.
"JAK inhibition is clearly a promising treatment for patients with RA," said Dr. Kremer. "JAK is unique in that it has the efficacy of the biologic agents and is an oral drug. Like all new agents in development, we will need to determine the longer-term safety and efficacy of the JAK inhibitor. The dose of the JAK inhibitor that may eventually be used in the clinic has not yet been determined with finality," he said.
[Presentation title: Safety and Efficacy After 24 Week (WK) Dosing of the Oral JAK Inhibitor CP-690,550 (CP) in Combination With Methotrexate (MTX) in Patients (PTS) With Active Rheumatoid Arthritis (RA). Abstract 1925]
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