C1-INH Compared to Placebo at the Time of Prodromal Symptoms for Hereditary Angioedema (HAE) Exacerbation

Section 3 Study Design and Methods:

Our proposal is to perform a randomized double-blind, three-arm, three-way cross-over study in which subjects with HAE would be placed into one of three different treatment groups based on computer randomization. Subjects will be randomized to receive placebo, 1000 units, or 1500 units of C1-INH at the onset of prodromal symptoms although they would be blinded to which one they were receiving. Randomization will be to one of the two doses or placebo and the sequence of further treatments will be determined randomly in a double-blinded fashion by a person who is not involved in the study. The randomized drug will be available 24 hours and 7 days a week. They would have to come to the study office to receive the blinded drug, and would need to seek treatment within 6 hours of the onset of the prodrome. Following the blinded treatment, the subject would need to be observed for at least 30 minutes. If a subject develops an acute HAE exacerbation in any of the three treatment periods, they would have access to 20 units/kg of open label C1-INH for acute treatment also received at the study office, and the time from onset of symptoms of an acute attack until the time the subject sought open-label treatment could not exceed 12 hours. Following open label rescue, the subject would need to be observed for at least 1 hour or until symptoms started to improve. The subject would also be expected to complete a symptom diary card over the next 24 hours after receiving open-label C1-INH to monitor severity and duration of symptoms (24 Hour Prodrome/Open-Label Diary Appendix IV) associated with the acute attack. The number, duration, and severity of acute HAE attacks would be compared for each treatment period. Each treatment period would last 16 weeks so each subject would be studied for a total of 48 weeks. Because safety has been established when C1-INH is used every third day with prophylaxis therapy, and patients may receive C1-INH for an attack without limits on the closeness of the attacks, our patients in this study may be retreated for prodromal symptoms as they require it, but not more than every other day since prodromes may precede the swelling and abdominal pain by up to 2 days.

Thrombosis has been identified with C1-INH, but only in neonates who were premature and at much higher doses than 1500 units every third day. Cinryze, also a C1-INH, is FDA approved for 1000 units every third day for prophylaxis. The dosing used in our study reflects the FDA approval dosing for Berinert, which is 20 units per kg for acute therapy, so that most patients will receive 1000 to 2500 units of C1-inh whenever they have an attack without day restrictions between dosing. The dosage approved by the FDA is 20 units per kg for Berinert and 1000 units total dose for Cinryze. The dose used in our study approximates these doses, but is not an FDA approved dose. There are no limits on how often Berinert can be dosed for acute attacks.

Figure IV outlines our treatment protocol.

Figure IV: Three-arm, randomized, cross-over, double-blind, placebo-controlled trial to determine effect of treating prodromal symptoms with C1-INH infusions of 1000 units, or 1500 units versus placebo. The sequence is random and double-blinded.