Treatment
Patients were randomised by the central registration method using an interactive web response system in a 1:1:1 ratio to receive either TAS5315 4 or 2 mg or placebo orally once daily for the study duration, taken in combination with MTX. MTX was purchased by the participating medical institutions and provided to the patients; all expenses were covered by Taiho. TAS5315 1 mg tablets were used; patients in the 4 mg group took four TAS5315 tablets and those in the 2 mg group took two TAS5315 and two placebo tablets.