Efficacy and Safety Study of DX-2930 to Prevent Acute Angioedema Attacks in Patients With Type I and Type II HAE

Inclusion Criteria: * Males and females 12 years of age or older at time of screening * Documented diagnosis of HAE, Type I or II * Baseline rate of at least 1 Investigator-confirmed HAE attack per 4 weeks * Adult subjects and caregivers of subjects under the age of 18 are willing and able to read, understand, and sign an informed consent form. Subjects age 12 to 17, whose caregiver provides informed consent, are willing and able to read, understand an dsign an assent form. * Males and femailes who are fertile and sexually active must adhere to contraception requirements. Exclusion Criteria: * Concomitant diagnosis of another form of chronic, recurrent angioedema, such as acquired angioedema, idiopathic angioedema, or recurrent angioedema associated with urticaria. * Participation in a prior DX-2930 study * Treatment with any other investigational drug or exposure to an investigational device within 4 weeks prior screening * Exposure to angiotensin-converting enzyme (ACE) inhibitors or any estrogen-containing medications within 4 weeks prior to screening. * Exposure to androgens within 2 weeks prior to entering the run-in period. * Use of long-term prophylactic therapy for HAE within 2 weeks prior to entering the run-in period. * Use of short-term prophylaxis for HAE within 7 days prior to entering the run-in period. * Any of the following liver function test abnormalities: alanine aminotransferase (ALT) \> 3x upper limit of normal, or aspartate aminotransferase (AST) \> 3x upper limit of normal, or total bilirubin \> 2x upper limit of normal (unless the bilirubin elevation is a result of Gilbert's syndrome). * Pregnancy or breastfeeding.