A Study to Evaluate the Clinical Efficacy and Safety of Subcutaneously Administered C1-esterase Inhibitor in the Prevention of Hereditary Angioedema

Inclusion Criteria:

Run-In Period Inclusion Criteria:

- Males or females aged 12 years or older.

- A clinical diagnosis of hereditary angioedema type I or II.

- Hereditary angioedema attacks over a consecutive 2-month period that required acute
treatment, medical attention, or caused significant functional impairment.

- For subjects who have used oral therapy for prophylaxis against HAE attacks within 3
months of Screening: use of a stable regimen within 3 months of Screening, with no
plans to change.

Eligibility Criteria for Entering Treatment Period 1:

- Laboratory confirmation of type I or type II hereditary angioedema, including
C1-esterase inhibitor functional activity less than 50% AND C4 antigen level below the
laboratory reference range.

- No clinically significant abnormalities as assessed using laboratory parameters.

- During participation in the run-in period, subjects must have experienced hereditary
angioedema attacks that required acute treatment, required medical attention, or
caused significant functional impairment.

Exclusion Criteria:

Run-In Period Exclusion Criteria:

- History of clinical significant arterial or venous thrombosis, or current history of a
clinically significant prothrombotic risk.

- Incurable malignancies at screening.

- Any clinical condition that will interfere with the evaluation of C1-esterase
inhibitor therapy.

- Clinically significant history of poor response to C1-esterase therapy for the
management of hereditary angioedema.

- Receiving therapy prohibited by the protocol, including medications for hereditary
angioedema prophylaxis.

- Female subjects who started taking or changed dose of any hormonal contraceptive
regimen or hormone replacement therapy (i.e., estrogen/progesterone-containing
products) within 3 months prior to the screening visit.