To assess how the absolute bioavailability, dose proportionality, pharmacokinetics, safety and tolerability of epratuzumab compared when given as a subcutaneous (sc) injection as to when given as an intravenous (iv) infusion in Caucasian and Japanese healthy volunteers.

Inclusion Criteria:

• Subject is male or female.
• At the Screening Visit, subject is 18 years to 50 years, inclusive (for Caucasian subjects), or 20 years to 50 years (for Japanese subjects)
• Subject must be in good health (physically and mentally) as determined by the investigator on the basis of medical history
• Subject has a body weight of 45 kg to 90 kg, inclusive, and body mass index (BMI) between 18.0 kg/m2 and 29.9 kg/m2, inclusive
• Japanese subjects are defined as a person carrying a Japanese passport, who is a descendant of 4 Japanese grandparents and has not been outside Japan for more than 5 years prior to screening
• Females of childbearing potential are required to have a negative serum pregnancy test at the Screening Visit and must agree to use an acceptable method of birth control during the study and for a period of 3 months after the administration of investigational medicinal product (IMP)
• Male subjects must agree to use an acceptable method of contraception during the study and for at least 3 months after receiving IMP unless they have undergone vasectomy

Exclusion Criteria:

• Subject has donated blood (including through participation in another clinical study) or suffered blood loss (≥450 mL) <60 days prior to dosing, or has donated platelets <14 days prior to dosing
• Subject has active malignancies or a history of malignancy
• Subject has a history of severe or multiple allergies
• Subject has a history of chronic infection, recent serious or life-threatening infection
• Subject with a recurrent history or active systemic/respiratory infection due to fungal, parasitic, or mycotic pathogens
• Subject has a positive HBsAg, anti-HCV or anti-HIV test result during the Screening Period
• Subject has a history of or a concurrent clinically significant illness, medical condition, or laboratory abnormality that, in the investigator's opinion, could affect the safety of the subject upon exposure to epratuzumab or confound the results of the study
• Female subjects who are breast feeding, pregnant, or plan to become pregnant during the study or within 3 months following dosing of the IMP
• Subjects who are immunocompromised
• A confirmed positive urine drug screen
• Subject has a history of substance abuse, drug addiction, or alcoholism within 3 years prior to study admission
• Subject is unable or unwilling to stop smoking during the inpatient stay
• Subject has previous exposure to, or has participated in studies with, any other anti-B-cell therapies
• Subject has a medical condition that requires chronic medication
• Subject has received a live vaccine in the month prior to the administration of IMP or is scheduled or expected to receive live vaccines during the study period or for 3 months after administration of the IMP