A Study of Single and Multiple Doses of ALXN1210 in Healthy, Adult Japanese Participants

Inclusion Criteria

• Healthy Japanese males or females aged 25 through 55 years, inclusive (participants who lived outside of Japan for ≤ 10 years and were first-generation Japanese, defined as born in Japan and having 4 biological grandparents who were ethnic Japanese).
• Body mass index from 18 through 29.9 kilogram/square meter (kg/m^2), inclusive, with weight between 50 and 100 kg, inclusive.
• QT interval (corrected using the Fridericia's formula) ≤ 450 milliseconds (msec) for males and ≤ 470 msec for females at Screening and prior to dosing on Day 1.
• Willing and able to give written informed consent and comply with the study visit schedule
• Documented vaccination with tetravalent meningococcal conjugate vaccine (MCV4) at least 56 days and not more than 3 years prior to dosing. Documentation included a positive serum bactericidal assay to confirm an immune response before study drug administration.
• Vaccination with serogroup B meningococcal vaccine at least 56 days prior to dosing on Day 1, with a booster administered at least 28 days prior to dosing on Day 1, with at least 28 days between the first and second injections.
• Female participants of childbearing potential were required to use highly effective contraception, starting at Screening and continuing until at least 6 months (Cohort 1) or 8 months (Cohorts 2 and 3) after the last dose of ALXN1210.
• Male participants with a female spouse/partner of childbearing potential or a pregnant or breastfeeding spouse or partner had to agree to use barrier contraception during the treatment period and for at least 6 months (Cohort 1) or 8 months (Cohorts 2 and 3) after the last dose of ALXN1210.

Exclusion Criteria

• Participants who were in intimate and prolonged contact with (defined as living under the same roof or providing personal care) people younger than 2 years of age or older than 65 years of age, or who were either immunocompromised or had one of the following underlying medical conditions: anatomic or functional asplenia (including sickle cell disease); congenital complement, properdin, factor D, or primary antibody deficiencies; acquired complement deficiencies (for example, those receiving eculizumab); or human immunodeficiency virus (HIV).
• Participants who were professionals exposed to environments of greater risk for meningococcal disease; research, industrial, and clinical laboratory personnel routinely exposed to Neisseria meningitidis; military personnel during recruit training (military personnel may be at increased risk of meningococcal infection when accommodated in close quarters); daycare center workers; those who lived on a college or university campus; and those who planned to travel during the course of the study or have travelled to endemic areas for meningococcal meningitis (for example, India, Sub-Saharan Africa, pilgrimage to Saudi Arabia for Hajj) 6 months prior to dosing.
• History of any Neisseria infection
• History of unexplained, recurrent infection; or infection requiring treatment with systemic antibiotics within the 90 days prior to dosing.
• HIV infection (evidenced by HIV-1 or HIV-2 antibody titer)
• Acute or chronic hepatitis B virus infection. Hepatitis B surface antigen (HBsAg) testing was required for all participants prior to enrollment. Participants with positive HBsAg were not enrolled. For participants with negative HBsAg, the following testing algorithms were required: If hepatitis B core antibody (HBcAb) was negative, the participants was eligible to enroll and If HBcAb was positive, the hepatitis B surface antibody (HBsAb) was tested. (If both HBcAb and HBsAb were positive, the participants was eligible to enroll and If HBcAb was positive and HBsAb was negative, the participants was not enrolled.)
• Acute or chronic hepatitis C virus infection (evidenced by antibody titer)
• Active systemic viral or fungal infection 14 days prior to dosing.
• Positive or indeterminate QuantiFERON-TB test indicating possible tuber