A Study to Evaluate Safety and Efficacy of ASP015K in Patients With Rheumatoid Arthritis (RA) Who Had an Inadequate Response to DMARDs

Subject has RA diagnosed according to the 1987 American College of Rheumatology (ACR) criteria or the 2010 American College of Rheumatology/European League against Rheumatism (ACR/EULAR) criteria

Subject who did not receive the following drugs, or received the drugs with stable dosage for at least 28 days prior to the baseline (start of treatment) for RA treatment:

* Non-steroidal anti-inflammatory drugs (NSAIDs; excluding topical formulations), oral morphine or equivalent opioid analgesics (≤ 30 mg/day), acetaminophen, or oral corticosteroids (≤ 10 mg/day in prednisolone equivalent)

At screening subject has active RA as evidenced by both of the following:

* ≥ 6 tender/painful joints (using 68-joint assessment)

* ≥ 6 swollen joints (using 66-joint assessment)

CRP \> 0.50 mg/dL at screening

Subject meets the ACR 1991 Revised Criteria for the Classification of Global Functional Status in RA Class I, II or, III at screening.

Inadequate responder to (including subjects who were intolerant of) at least one DMARD administered for at least 90 days prior to screening

* Positive HCV antibody

Subject has a history of or concurrent active tuberculosis (TB)

Subject has a history of or concurrent interstitial pneumonia and investigator/sub-investigator judges that it is inappropriate for the subject to participate in this study

Subject has a history of or concurrent malignant tumor (except for successfully treated basal cell carcinoma)

Subject has received live or live attenuated virus vaccination within 56 days prior to baseline. (Inactivated vaccines including influenza and pneumococcal vaccines are allowed.)

Subject has a history of or concurrent demyelinating disorders

Subject has any ongoing severe, progressive, or uncontrolled renal, hepatic, hematological, gastrointestinal, metabolic, endocrine, pulmonary, cardiac, neurological, infectious, or autoimmune disease except for RA (excluding Sjogren's syndrome and chronic thyroiditis), or any ongoing illness which would make the subject unsuitable for the study as determined by the investigator/sub-investigator

Subject has a history of clinically significant allergy. (Clinically significant allergy includes allergies such as systemic urticaria induced by specific antigens and drugs, anaphylaxis, and allergy associated with shock necessitating hospitalized treatment.)

Subject has concurrent cardiac failure, defined as NYHA classification Class III or higher, or a history of it

Subject has concurrent prolonged QT syndrome or a history of it. Subject has prolonged QT interval (defined as QTc ≥ 500 msec. Subject has QTc ≥ 500 msec at retest will be excluded) at screening

Subject has a history of positive HIV infection

Subject has congenital short QT syndrome or a history of it. Subject has shortened QT interval (defined as QTc \< 330 msec. Subject has QTc \< 330 msec at retest will be excluded) at screening.

What this study is about