A Study of a Single Dose of ALXN1210 in Healthy Participants

Inclusion Criteria

• Body mass index from 18 through 29.9 kilogram (kg)/square meter, inclusive, and weight between 50 and 100 kg, inclusive.
• QT interval (Fridericia's correction); ≤450 milliseconds (msec) for males and ≤470 msec for females at screening and pre-dose on Day 1.
• Willing and able to give written informed consent and comply with the study visit schedule.
• Male participant and his female spouse/partner who was of childbearing potential must be using highly effective contraception consisting of 2 forms of birth control (at least 1 of which must be a barrier method), starting at screening and continuing until at least 5 months after the last dose of ALXN1210.
• Documented vaccination with meningococcal conjugate vaccine (MCV4) at least 14 days and not more than 3 years prior to dosing.

Exclusion Criteria

• Participants in intimate and prolonged contact (defined as living under the same roof or providing personal care) with individuals who are either immunocompromised, or with a specific 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]; and human immunodeficiency virus [HIV]), people younger than 2 years old and older than 65 years old, and professionals exposed to environments of greater risk for meningococcal disease (research, industrial, and clinical laboratory personnel who are routinely exposed to Neisseria meningitidis, military personnel during recruit training [military personnel may be at increased risk when accommodated in close quarters], daycare center workers, or those living on a college or university campus).
• Participants living or working in the Saguenay-Lac-St-Jean area (due to increased incidence of meningococcal infections in that specific area).
• Female participants of childbearing potential, including any female who has experienced menarche and who has not undergone successful surgical sterilization (hysterectomy, bilateral tubal ligation, or bilateral oophorectomy), or who was pregnant, breastfeeding, or was not postmenopausal.
• Positive serum pregnancy test at screening or Day -1.
• Serum creatinine greater than the upper limit of normal (ULN) of the testing laboratory at screening and Day -1.
• Alanine aminotransferase or aspartate aminotransferase >ULN of the testing laboratory at screening and Day -1.
• Any of the following hematology tests: hemoglobin ULN of the testing laboratory; absolute neutrophils ULN of the testing laboratory; and platelets 450*10^3/μL at screening and Day -1.
• HIV infection (evidenced by HIV-1 or HIV-2 antibody titer).
• Acute or chronic hepatitis B virus (HBV) infection (evidenced by the presence of HBV surface antigen or immunoglobulin M antibodies against HBV core antigen).
• Acute or chronic hepatitis C virus infection (evidenced by antibody titer).
• Active systemic bacterial, viral, or fungal infection within 14 days prior to dosing.
• Positive QuantiFERON-TB test, indicating possible tuberculosis (TB) infection.
• History of complement deficiency.
• History of malignancy other than basal cell carcinoma.
• Participated in a clinical trial within 30 days before initiation of dosing on Day 1, or used any experimental small-molecule therapy within 30 days prior to dosing on Day 1, or biologic therapy within 90 days prior to initiation of dosing on Day 1 or within 5 half-lives of the product, whichever is greater.
• Major surgery within the last 90 days prior to dosing.
• History of any Neisseria infection; history of unexplained, recurrent infection; or infection requiring treatment with systemic antibiotics within the last 90 days prior to dosing.
• Contraindication to receiving MCV4, including severe (life-threatening) allergic reaction to a previous dose of MCV4; severe (life-threatening) allergy to any vaccine component; previous diagnosis of Guilla