The purpose of the study is to evaluate the safety, tolerability, PK and PD of a single-dose of ALXN1007 in healthy volunteers.

All subjects will be screened for eligibility after providing signed informed consent. Once a subject is determined to be eligible, the subject will be vaccinated with the quadrivalent meningococcal conjugate vaccine at least two weeks prior to dosing, if applicable. A total of 7 dose cohorts will be enrolled sequentially and randomized to receive ALXN1007 or placebo. Subjects will receive ALXN1007 or placebo at the clinic and be kept at the clinic for a total of 4 days for observation and completion of the required study tests.

The subjects will return for 8 additional clinic visits to complete the required study tests over the next 86 days. The total duration of the study is 90 days from the day of dosing with ALXN1007 or placebo.

Inclusion Criteria:

• Healthy individuals 25 to 55 years of age with documented vaccination with MCV4.

Exclusion Criteria:

• Abnormal renal or liver function.
• History of meningococcal disease.
• History of Guillain-Barre syndrome.
• Known infection with HIV or Hepatitis B or C.