Drug-Drug Interaction Study Evaluating Effects of ASP015K on Rosuvastatin

Inclusion Criteria: * Subject has a Body Mass Index (BMI) range of 18.5-32.0 kg/m2, inclusive, and must weigh at least 50 kg at screening. * Asian subject must be first generation Japanese born in Japan with both parents and four grandparents of Japanese descent and have resided outside of Japan for 5 years or less, or first generation Chinese born in China with both parents and four grandparents of Chinese descent and have resided outside of China for 5 years or less, or first generation Korean born in Korea with both parents and four grandparents of Korean descent and have resided outside of Korea for 5 years or less. * Non-Asian subject is self-reported as White, Black or African American, and Hispanic or Latino. * Female subject must be of non-childbearing potential (i.e., post-menopausal \[defined as at least 1 year without menses\] prior to screening or documented surgically sterile or status post hysterectomy \[at least 1 month prior to screening\]). * Female subject must have a negative pregnancy test at screening and day -1. * Female subject must not donate ova starting at screening and throughout the study period, and for 90 days after the final study drug administration. * Male subject and his female spouse/partner who is of childbearing potential must be using highly effective contraception consisting of two forms of birth control (one of which must be a barrier method) starting at screening and continue throughout the study period and for 90 days after final study drug administration. * Male subject must not donate sperm from screening and throughout the study period and for 90 days after final study drug administration. * Subject agrees not to participate in another investigational study while on treatment. * Subject must be capable of swallowing multiple tablets. Exclusion Criteria: * Female subject who has been pregnant within 6 months before screening assessment or breast feeding within 3 months before screening. * Subject has a known or suspected hypersensitivity to rosuvastatin, ASP015K, or any components of the formulations used. * Subject has had a previous intolerance or adverse reaction to a statin therapy. * Subject has any clinically significant history of allergic conditions (including drug allergies, asthma, eczema, or anaphylactic reactions, but excluding untreated, asymptomatic, seasonal allergies at time of dosing). * Subject has any history or evidence of any clinically significant cardiovascular, gastro intestinal, endocrinologic, hematologic, hepatic, immunologic, metabolic, urologic, pulmonary neurologic, dermatologic, psychiatric, renal, and/or other major disease or malignancy, as judged by the Investigator or designee. * Subject has/had febrile illness or symptomatic, viral, bacterial (including upper respiratory infection), or fungal (non-cutaneous) infection within 1 week prior to day -1. * Subject has a mean pulse \< 40 or \> 90 beats per minute (bpm); mean systolic blood pressure (SBP) \> 140 mmHg; mean diastolic blood pressure (DBP) \> 90 mmHg (measurements taken in triplicate after subject has been resting in sitting position for at least 5 minutes at screening and day -1. * Subject has used any prescribed or non-prescribed drugs (including vitamins, natural and herbal remedies, e.g. St. John's Wort) in the 2 weeks prior to study drug administration, with the exception of hormone replacement therapy (HRT) and intermittent acetaminophen (to a maximum of 2 g/day). * Subject has smoked or has used tobacco-containing products and nicotine or nicotine containing products in the past 6 months prior to screening. * Subject has a history of consuming more than 14 units of alcoholic beverages per week within 6 months prior to screening or has a history of alcoholism or drug/chemical/substance abuse within past 2 years prior to screening (Note: one unit = 12 ounces of beer, 4 ounces of wine or 1 ounce of spirits). * Subject has a positive test for alcohol, drugs of abuse, or cotinine at screening or day -1. * Subject has used any inducer of liver metabolism (e.g. barbiturates, rifampin) in the 3 months prior to day -1. * Subject has had any significant blood loss, donated one unit (450 mL) of blood or more, or received a transfusion of any blood or blood products within 60 days or donated plasma within 7 days prior to clinic check-in on day -1. * Subject has a positive serology test for hepatitis B surface antigen (HBsAg) (total), anti hepatitis A virus (Ig M), anti-hepatitis C virus, anti-hepatitis B core, or anti HIV type 1 or type 2 at screening. * Subject has participated in any interventional clinical study or has been treated with any investigational drugs within 30 days or 5 half-lives of the drug, whichever is longer, prior to screening. * Subject has a positive tuberculosis (TB) skin test, Quantiferon Gold test or T-SPOT® test at screening. * Subject has received any vaccine within 60 days prior to study drug administration. * Subject has had major gastrointestinal surgery or has a medical condition which may inhibit the absorption and/or metabolism of study drug. * Subject anticipates an inability to abstain from xanthine (e.g., caffeine), grapefruit, Seville blood oranges (including marmalade), star fruit, or any products containing these items from 72 hours prior to day -1 and throughout the duration of the study.