The overall aims of the study are:

• To assess the bioavailability of single doses of ALX-0061, administered s.c. at three dose levels, using 2 corresponding single i.v. dose levels as reference.
• To provide additional information on pharmacokinetics and pharmacodynamics of ALX-0061.
• To further determine the safety and tolerability of ALX-0061.
• To further evaluate the systemic (serum) immunogenicity of ALX-0061.

Key Inclusion Criteria:

1. Healthy volunteers.
2. Gender: male or female.
3. Age 18 to 55 years.
4. Body mass index (BMI): 18.0 ≥ BMI < 30.0 kg/m2.

Key Exclusion Criteria:

1. Any active inflammatory condition, or autoimmune disorder such as lupus erythematosus, multiple sclerosis or rheumatoid arthritis (RA).
2. Any current or recent (within 4 weeks prior to dose) signs or symptoms of infection that requires parenteral antibiotic administration.
3. Symptomatic infection, or suspicion thereof in the last 1 week prior to dosing.