A Study to Assess the Relative Bioavailability Between Two ASP015K Tablets and the Food Effect of a New Tablet in Healthy Adult Subjects

Inclusion Criteria:

- 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 of
treatment period 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 starting at screening and throughout the study
period and for 90 days after final study drug administration.

- 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.

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 ASP015K, or any components of
the formulation used.

- 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/had febrile illness or symptomatic, viral, bacterial (including upper
respiratory infection), or fungal (non-cutaneous) infection within 1 week prior to
first clinic check-in.

- 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), 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 six 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) prior to day -1 of treatment period 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 of treatment period
1.

- Subject has a positive test for hepatitis B surface antigen (HBsAg), anti-hepatitis A
virus (HAV) (Immunoglobulin [Ig] M), anti-hepatitis C virus (HCV), hepatitis B core
antibody, or anti-human immunodeficiency virus (HIV) type 1 or type 2 at screening.

- Subject has a positive tuberculosis (TB) skin test, Quantiferon Gold® test or T-SPOT®
test at screening.

- Subject received any vaccine within 60 days prior to study drug administration.

- Subject has an absolute neutrophil count (ANC) < 2000 cells/mm3 or a creatine
phosphokinase (CPK) > 1.5 x ULN at screening or day -1 of treatment period 1.

- Subject has had major gastrointestinal (GI) surgery or has a medical condition, which
may inhibit the absorption and/or metabolism of study drug.