An adverse event (AE) is any untoward medical occurrence in a clinical investigation participant administered a pharmaceutical product and that does not necessarily have a causal relationship with this investigational product or medicinal product. A SAE is any untoward clinical manifestation of signs, symptoms or outcomes (whether considered related to investigational product or not and at any dose which results in death, is life-threatening, requires inpatient hospitalization or prolongation of hospitalization, results in persistent or significant disability/incapacity, results in a congenital abnormality/birth defect, is an important medical event. Adverse events of special interest for this study are hypersensitivity reactions and disordered coagulation (hypercoagulability events and bleeding events).

The Safety Analysis Set consisted of all participants who received study drug. Overall number analyzed are participants presented by the actual treatment regimen. Because of dose modifications, some participants were treated with both dosing regimens and were counted in both treatment groups.

Laboratory values (chemistry, hematology, and coagulation) were to be considered clinically significant based on investigator's discretion.

The Safety Analysis Set consisted of all participants who received study drug.

Vital signs included blood pressure, heart rate, body temperature, and respiratory rate.

The Safety Analysis Set consisted of all participants who received study drug.

The plasma concentration of lanadelumab over treatment period was assessed.

The Pharmacokinetic (PK) Set included all participants in the Safety Analysis Set who have at least 1 evaluable post dose PK concentration value. Number analyzed is the number of participants with data available for analysis at the given timepoint.

The PK Set included all participants in the Safety Analysis Set who have at least 1 evaluable post dose PK concentration value.

The PK Set included all participants in the Safety Analysis Set who have at least 1 evaluable post dose PK concentration value.

The PK Set included all participants in the Safety Analysis Set who have at least 1 evaluable post dose PK concentration value.

The PK Set included all participants in the Safety Analysis Set who have at least 1 evaluable post dose PK concentration value.

The PK Set included all participants in the Safety Analysis Set who have at least 1 evaluable post dose PK concentration value.

The PK Set included all participants in the Safety Analysis Set who have at least 1 evaluable post dose PK concentration value.

The PK Set included all participants in the Safety Analysis Set who have at least 1 evaluable post dose PK concentration value.

The PK Set included all participants in the Safety Analysis Set who have at least 1 evaluable post dose PK concentration value.

Normalized number of investigator-confirmed HAE attacks during overall period are expressed as a monthly HAE attack rate. Investigator-confirmed HAE attack rate was calculated for each participant as number of investigator-confirmed HAE attacks occurring during given study period divided by the number of days the participant contributed to the period multiplied by 28 days. A HAE attack is defined as the symptoms or signs consistent with an attack in >=1 of the following locations: peripheral angioedema (cutaneous swelling involving an extremity, the face, neck, torso, and/or genitourinary region), abdominal angioedema (abdominal pain, with or without abdominal distention, nausea, vomiting, or diarrhea), laryngeal angioedema (stridor, dyspnea, difficulty speaking, difficulty swallowing, throat tightening, or swelling of the tongue, palate, uvula, or larynx).

The Safety Analysis Set consisted of all participants who received study drug. Overall number analyzed are participants presented by the actual treatment regimen. Because of dose modifications, some participants were treated with both dosing regimens and were counted in both treatment groups.

Normalized number of investigator-confirmed HAE attacks during each efficacy evaluation period other than overall treatment period are expressed as a monthly HAE attack rate. Investigator-confirmed HAE attack rate was calculated for each participant as number of investigator-confirmed HAE attacks occurring during given study period divided by number of days participant contributed to period multiplied by 28 days. A HAE attack is defined as symptoms or signs consistent with an attack in at least 1 of following locations: peripheral angioedema (cutaneous swelling involving an extremity, face, neck, torso, and/or genitourinary region), abdominal angioedema (abdominal pain, with or without abdominal distention, nausea, vomiting, or diarrhea), laryngeal angioedema (stridor, dyspnea, difficulty speaking, difficulty swallowing, throat tightening, or swelling of the tongue, palate, uvula, or larynx).

The Safety Analysis Set consisted of all participants who received study drug. Overall number analyzed are participants presented by the actual treatment regimen. Because of dose modifications, some participants were treated with both dosing regimens and were counted in both treatment groups.

Time to first investigator-confirmed HAE attack (days) for each efficacy evaluation period was calculated from date and time of first dose of lanadelumab for that efficacy evaluation period to date and time of first investigator-confirmed HAE attack after first open-label dose for that efficacy evaluation period. A HAE attack is defined as symptoms or signs consistent with an attack in >=1 of following locations: peripheral angioedema (cutaneous swelling involving an extremity, face, neck, torso, and/or genitourinary region), abdominal angioedema (abdominal pain, with or without abdominal distention, nausea, vomiting, or diarrhea), laryngeal angioedema (stridor, dyspnea, difficulty speaking, difficulty swallowing, throat tightening, or swelling of tongue, palate, uvula, or larynx). Kaplan-Meier Method was used for analysis.

The Safety Analysis Set consisted of all participants who received study drug. Overall number analyzed are participants presented by the actual treatment regimen. Because of dose modifications, some participants were treated with both dosing regimens and were counted in both treatment groups.

The normalized number of investigator-confirmed HAE attacks requiring acute treatment during each efficacy evaluation period are expressed as a monthly HAE attack rate. The investigator-confirmed HAE attack rate was calculated for each participant as the number of investigator-confirmed HAE attacks occurring during the given study period divided by the number of days the participant contributed to the period multiplied by 28 days. A HAE attack is defined as the symptoms or signs consistent with an attack in at least 1 of the following locations: peripheral angioedema (cutaneous swelling involving an extremity, the face, neck, torso, and/or genitourinary region), abdominal angioedema (abdominal pain, with or without abdominal distention, nausea, vomiting, or diarrhea), laryngeal angioedema (stridor, dyspnea, difficulty speaking, difficulty swallowing, throat tightening, or swelling of the tongue, palate, uvula, or larynx).

The Safety Analysis Set consisted of all participants who received study drug. Overall number analyzed are participants presented by the actual treatment regimen. Because of dose modifications, some participants were treated with both dosing regimens and were counted in both treatment groups.

The normalized number of moderate or severe investigator-confirmed HAE attacks requiring acute treatment during each efficacy evaluation period are expressed as a monthly HAE attack rate. The investigator-confirmed HAE attack rate was calculated for each participant as the number of investigator-confirmed HAE attacks occurring during the given study period divided by the number of days the participant contributed to the period multiplied by 28 days. A HAE attack is defined as the symptoms or signs consistent with an attack in at least 1 of the following locations: peripheral angioedema (cutaneous swelling involving an extremity, the face, neck, torso, and/or genitourinary region), abdominal angioedema (abdominal pain, with or without abdominal distention, nausea, vomiting, or diarrhea), laryngeal angioedema (stridor, dyspnea, difficulty speaking, difficulty swallowing, throat tightening, or swelling of the tongue, palate, uvula, or larynx).

The Safety Analysis Set consisted of all participants who received study drug. Overall number analyzed are participants presented by the actual treatment regimen. Because of dose modifications, some participants were treated with both dosing regimens and were counted in both treatment groups.

The normalized number of high morbidity investigator-confirmed HAE attacks requiring acute treatment during each efficacy evaluation period are expressed as a monthly HAE attack rate. The investigator-confirmed HAE attack rate was calculated for each participant as the number of investigator-confirmed HAE attacks occurring during the given study period divided by the number of days the participant contributed to the period multiplied by 28 days. A HAE attack is defined as the symptoms or signs consistent with an attack in at least 1 of the following locations: peripheral angioedema (cutaneous swelling involving an extremity, the face, neck, torso, and/or genitourinary region), abdominal angioedema (abdominal pain, with or without abdominal distention, nausea, vomiting, or diarrhea), laryngeal angioedema (stridor, dyspnea, difficulty speaking, difficulty swallowing, throat tightening, or swelling of the tongue, palate, uvula, or larynx).

The Safety Analysis Set consisted of all participants who received study drug. Overall number analyzed are participants presented by the actual treatment regimen. Because of dose modifications, some participants were treated with both dosing regimens and were counted in both treatment groups.

Characteristics of investigator-confirmed HAE attacks for each efficacy evaluation period included duration, severity, attack location, and rescue medication use. A HAE attack is defined as the symptoms or signs consistent with an attack in at least 1 of the following locations: peripheral angioedema (cutaneous swelling involving an extremity, the face, neck, torso, and/or genitourinary region), abdominal angioedema (abdominal pain, with or without abdominal distention, nausea, vomiting, or diarrhea), laryngeal angioedema (stridor, dyspnea, difficulty speaking, difficulty swallowing, throat tightening, or swelling of the tongue, palate, uvula, or larynx). Only categories with data are reported.

The Safety Analysis Set consisted of all participants who received study drug. Overall number analyzed are participants presented by the actual treatment regimen. Because of dose modifications, some participants were treated with both dosing regimens and were counted in both treatment groups.

A HAE attack is defined as the symptoms or signs consistent with an attack in at least 1 of the following locations: peripheral angioedema (cutaneous swelling involving an extremity, the face, neck, torso, and/or genitourinary region), abdominal angioedema (abdominal pain, with or without abdominal distention, nausea, vomiting, or diarrhea), laryngeal angioedema (stridor, dyspnea, difficulty speaking, difficulty swallowing, throat tightening, or swelling of the tongue, palate, uvula, or larynx).

The Safety Analysis Set consisted of all participants who received study drug. Overall number analyzed are participants presented by the actual treatment regimen. Because of dose modifications, some participants were treated with both dosing regimens and were counted in both treatment groups.

pKal activity was measured by biomarker cleaved high molecular weight kininogen (cHMWK) level to assess pharmacodynamics of lanadelumab.

The Pharmacodynamic (PD) Set included all participants in the Safety Analysis Set who have at least 1 evaluable post dose PD value. Number analyzed is the number of participants with data available for analysis at the given timepoint.

Immunogenicity was measured based on the presence or absence of neutralizing or non-neutralizing Anti-drug Antibody (ADA) in plasma.

The Safety Analysis Set consisted of all participants who received study drug. Number analyzed are the number of participants with data available for given category.