The objective of this study is to assess the safety, tolerability, and pharmacokinetics (PK) of single ascending intravenous (IV) doses of ASP2408 in non-elderly, healthy male and female subjects and to evaluate the pharmacodynamics of ASP2408.

This is single-dose escalation study composed of 8 sequential cohorts of healthy subjects receiving increasing doses of intravenously administered ASP2408 or matching placebo. Subjects will be confined in the clinic for 8 days.

Inclusion Criteria:

• Subject weighs at least 50 kg, and has a body mass index (BMI) of 18.0 to 32.0 kg/m2, inclusive.
• Results of subject's 12-lead electrocardiogram (ECG) are normal or, if abnormal, the abnormality is not clinically significant as determined by the investigator.
• Female subject must be at least two years postmenopausal OR surgically sterile (with documentation provided by a healthcare professional) and not pregnant or lactating.
• Male subject agrees to the use of male condoms until the end of study or 60 days post dose, whichever is longer.
• Subject is highly likely to comply with the protocol and complete the study.

Exclusion Criteria:

• Subject has a history of any clinically significant cardiac, endocrinologic, hematologic, hepatic, immunologic, metabolic, urologic, pulmonary, neurologic, dermatologic, psychiatric, renal, and/or other major disease or malignancy excluding adequately treated non-melanoma skin cancer.

• Subject has a history of severe allergic or anaphylactic reactions.

• Subject is a female of child-bearing potential.

• 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 (Note: one unit = 12 ounces of beer, 4 ounces of wine or 1 ounce of spirits).

• Subject has a positive test for alcohol or drugs of abuse.

• Subject has/had a symptomatic, viral, bacterial (including upper respiratory infection), or fungal (non-cutaneous) infection within 1 week prior to clinic check-in.

• Subject has a past history of opportunistic infection.

• Subject has a supine mean systolic blood pressure < 90 or > 160 mmHg and a mean diastolic blood pressure < 50 or > 90 mmHg, or mean pulse rate higher than 100 beats per min (bpm).

• Subject is known positive for human immunodeficiency virus (HIV) antibody.

• Subject has a positive TB skin test or Quantiferon Gold test or T-SPOT® test at Screening.

• Subject has a positive test for hepatitis C antibody, or positive test for hepatitis B surface antigen (HBsAg), or positive hepatitis B core antibody.

• Subject's laboratory test results:

  • alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST), are greater than 1.5 times the upper limit of normal
  • are outside the normal limits and considered by the investigator to be clinically significant with regard to the remaining per-protocol laboratory tests.

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

• Subject received any systemic immunosuppressant agent within 2 months prior to study drug administration.

• Subject has previously received any antibody or therapeutic biologic product prior to study drug administration.

• Subject received any systemic steroid within 2 months or steroid inhaler within 1 month prior to study drug administration.

• Subject has had treatment with prescription, non-prescription or complementary and alternative medicines (CAM) within 14 days prior to study drug administration.

• Subject has received an experimental agent within 30 days or five half-lives, whichever is longer, prior to study drug administration.

• Subject is participating in another clinical trial or has participated in another dose group of the current trial.

• 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.

• Subject has a history of heavy smoking or has used tobacco-containing products and nicotine or nicotine-containing products in the past six months.