Serum levels of cartilage oligomeric matrix protein during long-term treatment with etanercept in rheumatoid arthritis patients

Background: Cartilage oligomeric matrix protein (COMP) is considered a good predictor of joint damage in rheumatoid arthritis (RA), and the evaluation of this biomarker may be useful to assess the efficacy of the new biological therapies. Objectives: The aim of this study was to evaluate the effect of anti-TNFalpha-blockade treatment on serum levels of COMP in RA patients. Methods: 21 patients with active RA (M/F = 1/20; mean age = 50.8 yrs, range 28-70; mean disease duration = 126.6 months, range 24-288), according to ACR criteria, entered the study. Each patient was monitored during a one-year period while assuming etanercept therapy (25mg subcutaneously twice a week). At baseline and at 3, 6, and 12-month intervals the main clinical and laboratory parameters were measured, including serum levels of COMP (ELISA kit; AnaMar Medical, Uppsala, Sweden). Results: We found serum levels of COMP suggestive for tissue damage (>10 U/L) in 12 (57%) of our RA patients. During etanercept therapy, in those patients with increased COMP levels, we observed a reduction of this biomarker at 3, 6 and 12-month intervals in 6 (50%), 6 (50%) and 8 (75%) patients respectively. They also showed lower Disease Activity Score (DAS), Ritchie Index (RI) and Health Assessment Questionnaire (HAQ) values respect to the baseline findings. After one-year treatment with etanercept we did not find any significant difference in the clinical and laboratory responses between patients with or without increased serum levels of COMP at baseline. Conclusion: Our 12-month study strengthens previous report findings, regarding etanercept effect on serum levels of COMP, and furthermore shows the maintaining of its reduced serum levels during long-term treatment. Thus, in RA patients with COMP abnormal levels, the assessment of this biomarker may be useful to evaluate the protective effect of anti-TNF therapy on the tissue damage. References: 1. Skoumal M et al. Scand J Rheumatol 2003; 32: 156-161. 2. Crnkic M et al. Arthritis Res Ther 2003; 5: 181-185. 3. Lindqvist E et al. Ann Rheum Dis. 2005; 64: 196-201.