Inclusion Criteria:

• Males and females, ≥ 12 years of age.
• Diagnosed with non-histaminergic normal C1-INH angioedema at the time of enrollment into the antecedent Study SHP643-303.  
• Participants must have completed the treatment period (through Visit 26/Day 182) of Study SHP643-303 without reporting a clinically significant TEAE that would preclude subsequent exposure to lanadelumab.
• Agree to adhere to the protocol-defined schedule of treatments, assessments, and  procedures.
• Males, or non-pregnant, non-lactating females who are of child-bearing potential and who agree to be abstinent or agree to comply with the applicable contraceptive requirements of this protocol for the duration of the study; or females of  non-childbearing potential, defined as surgically sterile (status post hysterectomy,  bilateral oophorectomy, or bilateral tubal ligation) or post-menopausal for at least  12 months.  
• The participant (or the participant's parent/legal guardian, if applicable) has provided written informed consent approved by the institutional review board/research  ethics board/ethics committee (IRB/REB/EC) at any time prior to study start.
• If the  participant is a minor (i.e., less than 18 years of age), have a parent/legal guardian who is informed of the nature of the study provide written informed consent (i.e., permission) for the minor to participate in the study before any study-specific  procedures are performed.
• Assent will be obtained from minor participants.  

Exclusion Criteria:  

• Discontinued from Study SHP643-303 after enrollment but before Visit 26  for any reason.
• Presence of important safety concerns identified in Study SHP643-303 that would preclude participation in this study.  
• Dosing with an investigational product (IP, not including IP defined in antecedent  Study SHP643-303 or exposure to an investigational device within 4 weeks prior to Day 0.
• Participant has a known hypersensitivity to the investigational product or its  components.
• Have any condition (surgical or medical) that, in the opinion of the investigator or sponsor, may compromise their safety or compliance, preclude the successful conduct of  the study, or interfere with interpretation of the results (e.g., significant  pre-existing illness or other major comorbidities that the investigator considers may confound the interpretation of study results).