A Study to Evaluate the Safety and Effect of Escalating Doses of CINRYZE

Qualifying subjects entered a 3-step dose escalation algorithm: * Step 1: 1500 Units twice per week (starting dosing regimen for all subjects in the study) * Step 2: 2000 Units twice per week * Step 3: 2500 Units twice per week Each step consisted of 12 weeks of safety monitoring, followed by calculation of average monthly angioedema attack rate based on subject reports of angioedema symptoms (regardless of intensity) and actual duration of therapy for that step. If a subject was deemed a "success" at a given step and the investigator and medical monitor determined that it was safe for the subject to continue on that dose, the subject entered a 3 month follow-up period at that dose level with continued safety monitoring. The subject could not re-enter the study for purposes of dose escalation during the follow-up period. If a subject was not deemed a "success," the subject initiated the next highest step of the dose escalation algorithm provided that the investigator and medical monitor agreed that dose escalation was appropriate. If at the end of Step 3 (2500 Units), a subject was not deemed a "success," then the Week 12 visit represented study completion and the subject was referred to the physician who manages their HAE care.