A Phase I Study to Compare 3 Different Strengths of an Extended Release Formulation of ASP015K to an Immediate Release Formulation of ASP015K

Inclusion Criteria: * The subject must weigh at least 45 kg and have a body mass index (BMI) of 18-32 kg/m2, inclusive at Screening * If female, the subject is surgically sterile (with documentation provided by a healthcare professional), or is post-menopausal (defined as at least 2 years since last regular menstrual cycle and confirmatory follicle stimulating hormone (FSH) level of ≥ 30 U/L at screening) and the subject is not pregnant as documented by a negative serum pregnancy test at Screening and Day -1 and is not lactating * If male, the subject agrees to sexual abstinence, is surgically sterile (with documentation provided by a healthcare professional) or is using a medically acceptable method to prevent pregnancy and agrees to continue using this method during the study and until 90 days after the last dose of study drug administration * Male subject must agree to not donate sperm during the study and until 90 days after last dose of study drug administration * The subject's 12-lead electrocardiogram (ECG) is normal at Screening and Day -1 of initial treatment period or, if abnormal, the abnormality is not clinically significant as determined by the Investigator * The subject's clinical laboratory test results at Screening and Day -1 are within normal limits unless the Investigator considers the abnormality to be "not clinically significant" * The subject is medically healthy, with no clinically significant medical history or abnormalities observed upon physical examination as determined by the Investigator * The subject is willing and able to comply with the study requirements * The subject must be capable of swallowing multiple tablets * The subject is able to consume the FDA high fat breakfast within 30 minutes Exclusion Criteria: * The subject has a previous history of any clinically significant gastro-intestinal, neurological, renal, hepatic, pulmonary, metabolic, cardio-vascular, psychiatric, endocrine, hematological disorder or disease, malignancy excluding non-melanoma skin cancer or any other medical condition that, in the Investigator's opinion, would preclude participation in the study * The subject has had major GI surgery (such as colectomy, cholecystectomy, etc) which may inhibit the absorption and/or metabolism of study drug * The subject has a history of consuming more than 14 units of alcoholic beverages per week 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) * The subject has a positive test for alcohol or drugs of abuse at Screening or Day -1 * The subject has a positive cotinine test at Screening or Day -1 * The subject has had treatment with prescription, non-prescription or complementary and alternative medicines (CAM) within 14 days prior to Day -1 (of initial treatment period) with the exception of stable hormone replacement therapy (HRT) and/or occasional use of acetaminophen (up to a maximum of 2 g/day) * The subject has/had a symptomatic, viral, bacterial (including upper respiratory infection), or fungal (non-cutaneous) infection within 1 week prior to Day -1 * The subject has a positive test for hepatitis C antibody, or positive test for hepatitis B surface antigen (HBsAg), or positive hepatitis B core antibody at Screening * The subject has a history of the human immunodeficiency virus (HIV) antibody * The subject has a positive tuberculosis (TB) skin test, Quantiferon Gold test or T-SPOT® test at Screening * The subject received any vaccine within 60 days prior to study drug administration * The subject has received an experimental agent within 30 days or five half-lives, whichever is longer, prior to study drug administration * The 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 admission on Day -1 * The subject has an absolute neutrophil count (ANC) \< 2500 cells/mm3 or a CPK \> 1.5x upper limit of normal at Screening and Day -1 of initial treatment period * The subject has smoked or has used tobacco-containing products and nicotine or nicotine-containing products in the past six months prior to Screening