Background: Severe attacks of hereditary angioedema (HAE) are debilitating and potentially life threatening, and can increase anxiety and the use of medical resources.
Objective: This post hoc assessment evaluated recombinant human C1 esterase inhibitor (rhC1-INH) used to treat acute severe HAE attacks.
Methods: In a double-blind, randomized-controlled trial (RCT), patients with an HAE attack (baseline visual analog scale score of ≥50 mm, with severe attacks defined as ≥75 mm) were randomly assigned to receive rhC1-INH (50 IU/kg for patients who weighed <84 kg; 4200 IU for patients who weighed ≥84 kg) or placebo. Also, in an open-label extension (OLE) study of rhC1-INH, oropharyngeal-laryngeal attacks were analyzed. Rescue therapy with rhC1-INH 50 IU/kg (≤4200 IU) was permitted after 4 hours or for life-threatening symptoms (in the RCT) or after 1 hour (in the OLE study). The primary end point measured the time to the beginning of symptom relief by using the Treatment Effects Questionnaire.
Results: Of 75 adults in the RCT, 43 had severe attacks and received either rhC1-INH (n = 24) or placebo (n = 19). The median (95% confidence interval) time to the onset of symptom relief totaled 90.0 minutes (95% confidence interval, 47.0-120.0 minutes) versus 334.0 minutes (95% confidence interval, 105.0 to not calculable minutes; hazard ratio, 2.5; p = 0.02), for rhC1-INH and placebo, respectively. Open-label rhC1-INH rescue therapy was administered to 1 of 24 in the rhC1-INH group (4.2%) and 10 of 19 in the placebo group (52.6%). During the OLE study, the median onset of symptom relief with rhC1-INH for eight oropharyngeal-laryngeal HAE attacks was 69.0 minutes (95% confidence interval, 59.0-91.0 minutes).
Conclusion: In the current study, rhC1-INH was efficacious in resolving severe HAE attacks, including oropharyngeal-laryngeal attacks. The rhC1-INH rescue treatment rapidly improved symptoms for patients who received placebo and who experienced worsening or sustained symptoms.