A SAE was any adverse experience occurring at any dose that resulted in any of the following outcomes: Death, Life-threatening experience, required inpatient hospitalization or prolongation of existing hospitalization. Resulted in persistent or significant disability or incapacity. Was a congenital anomaly or birth defect. Was considered to be an important medical event. An AE was considered treatment-emergent if the onset time was after administration of study drug through the Day 120 post-dose final follow-up visit or, in the event that onset time preceded study drug administration, the AE increased in severity during the 120-day post-dose follow-up period.

Safety Population included all randomized participants who received at least 1 dose of study drug.

Pharmacokinetic (PK) parameter Cmax data were reported.

Pharmacokinectic (PK) population included all randomized HAE participants in the safety population who had sufficient blood samples to obtain a plasma concentration versus time profile.

PK parameter Tmax data were reported.

Pharmacokinectic (PK) population included all randomized HAE participants in the safety population who had sufficient blood samples to obtain a plasma concentration versus time profile.

PK paramenter AUC data were reported.

Pharmacokinectic (PK) population included all randomized HAE participants in the safety population who had sufficient blood samples to obtain a plasma concentration versus time profile.

PK parameter CL/F data were reported.

Pharmacokinectic (PK) population included all randomized HAE participants in the safety population who had sufficient blood samples to obtain a plasma concentration versus time profile.

PK parameter Vd/F data were reported.

Pharmacokinectic (PK) population included all randomized HAE participants in the safety population who had sufficient blood samples to obtain a plasma concentration versus time profile.

PK parameter t(1/2) data were reported.

Pharmacokinectic (PK) population included all randomized HAE participants in the safety population who had sufficient blood samples to obtain a plasma concentration versus time profile.

Analysis of this outcome measure was based on participants in the 300 mg, 400 mg, and placebo dose groups with a historical baseline attack rate of at least 2 attacks over the last 3 months prior to enrollment. The result is based on General Estimating Equation (GEE) analysis of repeated counts per week during the pre-specified assessment period (Days 8 to 50; predicted to correspond to a period of notable drug exposure). Baseline HAE attack rate per week was a covariate, treatment group is a fixed effect, and participant was a random effect in the GEE model with independence working correlation structure.

All randomized participants in the 300 mg, 400 mg, and placebo groups who received at least 1 dose of study drug and who had a historical baseline attack rate of at least 2 attacks in the 3 months prior to enrollment.

This endpoint analysis was based on participants in the 300 mg, 400 mg, and placebo dose groups with a historical baseline attack rate of at least 2 attacks over the last 3 months prior to enrollment. The result is based on General Estimating Equation (GEE) analysis of repeated counts per week during the prespecified assessment period (Day 8 to Day 92 predicted to correspond to a period of notable drug exposure). Baseline HAE attack rate per week is a covariate, treatment group is a fixed effect, and participant is a random effect in the GEE model with independence working correlation structure.

All randomized participants in the 300 mg, 400 mg, and placebo groups who received at least 1 dose of study drug and who had a historical baseline attack rate of at least 2 attacks in the 3 months prior to enrollment.

This endpoint analysis was based on participants in the 300 mg, 400 mg, and placebo dose groups with a historical baseline attack rate of at least 2 attacks over the last 3 months prior to enrollment. The result is based on General Estimating Equation (GEE) analysis of repeated counts per week during the prespecified assessment period (Day 8 to Day 64 predicted to correspond to a period of notable drug exposure). Baseline HAE attack rate per week is a covariate, treatment group is a fixed effect, and participant is a random effect in the GEE model with independence working correlation structure.

All randomized participants in the 300 mg, 400 mg, and placebo groups who received at least 1 dose of study drug and who had a historical baseline attack rate of at least 2 attacks in the 3 months prior to enrollment.

This endpoint analysis was based on participants in the 300 mg, 400 mg, and placebo dose groups with a historical baseline attack rate of at least 2 attacks over the last 3 months prior to enrollment. The result is based on General Estimating Equation (GEE) analysis of repeated counts per week during the prespecified assessment period (Day 1 to Day 50 predicted to correspond to a period of notable drug exposure). Baseline HAE attack rate per week is a covariate, treatment group is a fixed effect, and participant is a random effect in the GEE model with independence working correlation structure.

All randomized participants in the 300 mg, 400 mg, and placebo groups who received at least 1 dose of study drug and who had a historical baseline attack rate of at least 2 attacks in the 3 months prior to enrollment.