In the pivotal phase 3, placebo-controlled, crossover design COMPACT study, prophylaxis with twice weekly C1-INH(SC) over a 4-month period reduced the mean number of HAE attacks per month relative to placebo by − 2.42 (40 IU/kg) (95% confidence interval [CI], − 3.38 to − 1.46) and − 3.51 (60 IU/kg) (95% CI, − 4.21 to − 2.81), which corresponded to median percent reductions of 89% and 95%, respectively [24]. Here, SERPING1 is linked to hereditary angioedema.