The Week 1 to end of on-treatment period HAE attack rate was calculated for each participant as number of HAE attacks occurring from Week 1 to 28 days after the last dose date divided by the number of days the participant contributed to the period multiplied by 28 days. An HAE attack was defined as an event with signs or symptoms consistent with an attack in at least 1 of the 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 intent-to-treat (ITT) population included all enrolled or randomized participants.

The Week 5 to end of on-treatment period HAE attack rate was calculated for each participant as number of HAE attacks occurring from Week 5 to 28 days after the last dose date divided by the number of days the participant contributed to the period multiplied by 28 days. An HAE attack was defined as an event with signs or symptoms consistent with an attack in at least 1 of the 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).

ITT population included all enrolled or randomized participants.

The Week 5 to end of on-treatment period HAE attack rate was calculated for each participant as number of moderate or severe HAE attacks occurring from Week 5 to 28 days after the last dose date divided by the number of days the participant contributed to the period multiplied by 28 days. An HAE attack was defined as an event with signs or symptoms consistent with an attack in at least 1 of the 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). HAE attack severity: Mild: transient or mild discomfort, Moderate: mild to moderate limitation in activity, some assistance needed, and Severe: marked limitation in activity, assistance required.

ITT population included all enrolled or randomized participants.

Clinical response was defined as a ≥ 50%, ≥ 70%, or ≥ 90% reduction from Baseline in HAE attack rate from Week 5 to Week 17. The HAE attack rate was calculated as number of investigator-confirmed HAE attacks occurring from Week 5 to 28 days after last dose administration, divided by the number of days the participant contributed to the period multiplied by 28 days. An HAE attack was defined as an event with signs or symptoms consistent with an attack in at least 1 of the 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).

ITT population included all enrolled or randomized participants. Overall number of participants analyzed is the number of participants with data available for analyses.

The Week 5 to end of on-treatment period HAE attack rate was calculated for each participant as number of HAE attacks requiring acute therapy occurring from Week 5 to 28 days after the last dose date divided by the number of days the participant contributed to the period multiplied by 28 days. An HAE attack was defined as an event with signs or symptoms consistent with an attack in at least 1 of the 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). HAE attacks requiring acute therapy included those attacks with medical intervention or hospitalization marked on the case report form (CRFs).

ITT population included all enrolled or randomized participants.

High-molecular-weight kininogen (HMWK) is an abundant protein found in plasma and it has a critical role in acute attacks of HAE. During HAE attack plasma kallikrein cleaves HMWK producing cleaved HMWK (cHMWK) and bradykinin, the major biologic peptide that promotes the edema, one of the characteristic traits of HAE. Percentage of cHMWK levels were assessed to evaluate pharmacodynamics of donidalorsen.

ITT population included all enrolled or randomized participants. Number analyzed is number of participants with data available for analysis at specified time point.

Prekallikrein (PKK) has a critical role in acute attacks of HAE. During HAE attack PKK is activated to form plasma kallikrein. Plasma kallikrein cleaves HMWK producing cleaved HMWK (cHMWK) and bradykinin, the major biologic peptide that promotes the edema, one of the characteristic traits of HAE. Prekallikrein levels were measured to assess pharmacodynamics of donidalorsen.

ITT population included all enrolled or randomized participants. Number analyzed is number of participants with data available for analysis at specified timepoint.

Treatment options for HAE included on-demand treatment of attacks and prophylaxis. On-demand medication options included supplementation of C1-INH (either plasma-derived or recombinant C1-INH concentrate) and inhibition of BK2 receptor activation (BK2-receptor antagonist). The number of participants who used on-demand medication at Week 9 (Day 57) and at Week 17 (end of the on-treatment period) were reported.

ITT population included all enrolled or randomized participants.

The AE-QoL was developed to measure health-related quality of life (HRQoL) impairment in participants with recurrent angioedema. The AE-QoL is a self-administered questionnaire that can be completed in less than 5 minutes. It comprises 17 items across 4 domains: functioning, fatigue/mood, fears/shame, and food. Responses use a 5-point Likert scale ranging from '0 = never' to '4 = very often.' Per-participant scores for each domain were computed using the appropriate scoring algorithm applied to the question response scores for each domain. Per-participant total scores (including all 4 domains) were similarly computed using the question response scores for all 17 questions. The outputs from the scoring algorithm were normalized on a scale ranging from 0 (less adverse impact) to 100 (most adverse impact). Global total score ranges from 0 to 100, with higher scores indicating greater impairment. Mixed model for repeated measures (MMRM) was used for analyses.

ITT population included all enrolled or randomized participants. Number analyzed is the number of participants with data available at specified timepoint.