A Study to Evaluate the Safety and Tolerability of KJ103 in Healthy Adults

This single ascending dose (SAD), randomized, single-blinded, placebo controlled study is the first study and it is designed to evaluate the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of KJ103 in healthy subjects after a single intravenous dose. It will include up to 34 healthy subjects in up to five dose groups.

Inclusion criteria

• Male or female between the ages of 18 and 55 years, inclusive.
• Male body weight ≥50kg, female body weight ≥45kg, body mass index (BMI) within 18 kg/m2to 35 kg/m2, inclusively.
• Immunoglobulin (IgG) levels at screening is within the normal range.
• Considered "healthy" by the investigator. Healthy status is defined by absence of evidence of any active or chronic disease following a detailed medical and surgical history, as well as a complete physical examination including vital signs, 12-lead ECG, hematology, biochemistry, and urinalysis.

Exclusion criteria

• History of or diagnosis at screening of any clinically significant immunodeficiency including but not limited to immunoglobulin A deficiency.
• History of significant cardiovascular, pulmonary, hematologic, neurological, psychiatric, endocrine, immunologic or dermatologic disease.
• Any clinically significant illness in the 28 days prior to the first study drug administration.
• Any history of tuberculosis.
• Positive screening results to HIV Ag/Ab combo, syphilus, hepatitis A, hepatitis B surface antigen or hepatitis C virus tests.
• Positive test result for alcohol and/or drugs of abuse at screening or prior to the first drug administration.
• Current use of tobacco or nicotine-containing products exceeding 10 cigarettes per day or equivalent.
• Received an investigational drug (or was using an investigational device at the time) within 30 days prior to screening, or at least 5 times the respective elimination half-life (if known), whichever is longer.
• Female who is lactating.
• Female who is pregnant according to the pregnancy test at screening or prior to the first study drug administration.