This study was an extension study conducted as an open-label multicenter study in rheumatoid arthritis (RA) participants who completed the Phase IIb Study of ASP015K [015K-CL-RAJ1 (hereinafter referred to as study RAJ1)], Phase III Study of ASP015K [015K-CL-RAJ3 (RAJ3)], or Phase III Study of ASP015K [015K-CL-RAJ4 (RAJ4)]. After the marketing approval in Japan on 26 Mar 2019, this study continued as post marketing clinical study in Japan. In Taiwan and Korea, this study continued as clinical study.~Participants received oral ASP015K once daily (QD) after breakfast. The ASP015K dose was increased later for participants who have no safety problems but showed lack of efficacy.~The duration of treatment with the study drug was differed depending upon the participants.
This study evaluated the safety and efficacy of long-term administration of ASP015K in patients who have completed Phase IIb or Phase III studies.