A Long Term Safety Study of BCX7353 in Hereditary Angioedema

Key Inclusion Criteria: * Subjects with HAE Type I or II who either have participated in a previous BCX7353 study or, in selected countries, in the opinion of the Investigator are expected to derive benefit from an oral treatment for the prevention of angioedema attacks. * Access to appropriate medication for treatment of acute attacks * Acceptable effective contraception * Written informed consent Key Exclusion Criteria: * Pregnancy or breast-feeding * Any clinically significant medical condition or medical history that, in the opinion of the Investigator or Sponsor, would interfere with the subject's safety or ability to participate in the study * Any laboratory parameter abnormality that, in the opinion of the Investigator, is clinically significant and relevant for this study * Discontinuation of study drug due to a hypersensitivity reaction BCX7353 in a prior study * Severe hypersensitivity to multiple medicinal products or severe hypersensitivity/ anaphylaxis with unclear etiology * Unacceptable noncompliance in a previous BCX7353 study (if applicable) as assessed by the Sponsor or Investigator * Investigational drug exposure, other than BCX7353, within 30 days prior to the screening visit (or baseline if no screening visit)