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

Study involves 3 parallel groups. Subjects in each group will receive 3 single-dose
treatments with a washout period of at least 7 days separating the dosing between two
consecutive treatments. Dosing conditions include both fed and fasted conditions.

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