The primary objective of this study is to characterize the PK properties of a single dose of gefurulimab in healthy Chinese participants.

Inclusion Criteria:

• Participants must be 18 to 45 years of age, inclusive, at the time of signing the informed consent.
• Body weight within ≥ 45 kg to < 110 kg and BMI within the range 18 to 30 kg/m2 (inclusive) at Screening and Admission (Day -1).
• Participants who are healthy as determined by medical evaluation with no clinically significant or relevant abnormalities as determined by medical history, physical examination, vital signs, 12-lead ECG, and clinical laboratory evaluation.
• QTcF ≤ 450 msec for male participants and ≤ 460 msec for female participants at Screening and prior to dosing on Day 1.
• Documented vaccination against N meningitidis serotypes A, C, W-135, Y at least 28 days and not more than 3 years prior to dosing on Day 1.

Exclusion Criteria:

• History of any Neisseria meningitidis infection.
• History or presence of cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrinological, hematological, or neurological disorders.
• Abnormal blood pressure as determined by the Investigator.
• History of latent or active TB (Tuberculosis) or exposure to endemic areas.
• Active systemic bacterial, viral, or fungal infection within 14 days prior to dosing.
• History of latent or active TB or exposure to endemic areas within 8 weeks prior to the Screening Visit confirmed by QuantiFERON®-TB test.
• Significant allergies to humanized biologics.
• Clinically significant multiple or severe drug allergies, intolerance to topical corticosteroids, or severe post-treatment hypersensitivity reactions.
• History of clinically significant allergic reaction (eg, anaphylaxis or angioedema) to any product (eg, food, pharmaceutical).
• History of allergy or intolerance to penicillin or cephalosporin.
• Lymphoma, leukemia, or any malignancy within the past 5 years except for basal cell or squamous epithelial carcinomas of the skin that have been resected with no evidence of metastatic disease for 3 years.
• Current or chronic history of liver disease.
• Evidence of human immunodeficiency virus (HIV) infection (positive HIV type 1 or type 2 antibody).
• Evidence of hepatitis B infection (positive hepatitis B surface antigen [HBsAg] or positive total hepatitis B core antibody [HBcAb] with negative surface antibody [anti-HBs]), or hepatitis C viral infection (positive HCV RNA).
• Female participants who have a positive pregnancy test at Screening or Admission.
• Positive prestudy drug/alcohol screen; positive result may be repeated once.

Alexion has a public commitment to allow requests for access to study data and will be supplying a protocol, CSR, and plain language summaries.