Inclusion Criteria:  Signed and dated informed consent form Diagnosis of HAE type I or II Documented history of at least 3 HAE attacks within the last 3 consecutive months prior to screening, or a minimum of 2 HAE attacks during the screening period Reliable access and experience to use standard of care acute attack medications  Exclusion Criteria:  Pregnancy or breast-feeding Clinically significant abnormal electrocardiogram Any other systemic disease or significant disease or disorder that would interfere with the patient's safety or ability to participate in the study Use of C1-esterase inhibitor, oral kallikrein inhibitors, attenuated androgens, anti-fibrinolytics, or monoclonal HAE therapy within a defined period prior to enrolment Abnormal hepatic function Abnormal renal function History of alcohol or drug abuse within defined period, or current evidence of substance dependence or abuse Participation in any other investigational drug study within defined period