In this small, randomized, double-blind, Phase II, multicenter, placebo-controlled, exploratory study, researchers investigated whether monotherapy with Orencia, administered for six months and then withdrawn, was more effective than placebo in delaying the development of rheumatoid arthritis (RA) in adult patients with undifferentiated inflammatory arthritis (UA) who were positive for anti-cyclic citrullinated peptide (anti-CCP2) antibodies, a serum biomarker associated with increased risk of progression to erosive RA.
In this study, 56 individuals with UA who were positive for anti-CCP2 antibodies were randomized to receive either monotherapy with Orencia (abatacept) (n=28; dose approximating 10mg/kg based on weight range) or placebo (n=28) for six months, after which treatment was discontinued.
The primary endpoint of this study was the proportion of patients who developed RA as measured by the American College of Rheumatology criteria at month 12, six months after treatment was ended.
At year one, 50 of the patients were evaluable and 12 of the 26 (46.2%) patients treated with Orencia developed RA, compared to 16 of the 24 (66.7%) placebo-treated patients.
The mean changes in total score, erosion score and joint space narrowing score from baseline to year one were 0.02 units for Orencia versus 1.11 units for placebo, 0.02 units for Orencia versus 0.85 units for placebo and 0.00 units for Orencia versus 0.26 units for placebo, respectively. Further studies in larger patient populations of UA are required to validate these findings.