At week 12 , the ACR20 response rates were 39.0 % , 61.0 % , 65.0 % , and 65.9 % in the 25-mg , 50-mg , 100-mg , and 150-mg groups , respectively , and were significantly higher in the 50-mg group ( P = 0.007 ) and the 100-mg and 150-mg groups ( P = 0.002 ) as compared to the response rates in the placebo group ( 29.3 % ) .