A randomized, controlled trial to study the efficacy and safety of C1 inhibitor concentrate in treating hereditary angioedema

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Abstract
BACKGROUND: No effective treatment exists in the United States for acute attacks of hereditary angioedema (HAE). STUDY DESIGN AND METHODS: To evaluate the efficacy and safety of C1 inhibitor concentrate in treating HAE, a large primary care and referral center hospital conducted a randomized, placebo‐controlled, double‐blind trial with intent‐to‐treat analysis. Of the 36 patients enrolled in the study, 23 received treatment, and 22 completed the trial. C1 inhibitor concentrate or albumin (placebo) infusions were administered in a blind fashion to HAE patients who came to the hospital for treatment no later than 5 hours after an attack began. RESULTS: Relief was almost twice as fast in persons receiving C1 inhibitor concentrate than in the controls: 7.62 hours (mean; SD 7.08) versus 15.35 hours (mean; SD 8.31), respectively. The difference for time‐to‐relief was highly significant (p = 0.007, Mann‐Whitney U test). The median time‐to‐relief was 6.17 hours (interquartile range 0.33‐15.35) in the treatment group and 15.35 hours (interquartile range 14.00–22.83) in the control group. Resolution of symptoms was one‐third faster in the C1 inhibitor concentrate group than in the placebo group: 23.98 hours (mean; SD 14.81) and 34.58 hours (mean; SD 13.56), respectively (p = 0.09, Mann‐ Whitney U test). Recovery of functional C1 inhibitor was 119.65 percent (mean; SD 50.80), and half‐life was 37.87 hours (mean; SD 19.75). Recovery of antigenic C1 inhibitor was 147.75 percent (mean; SD 97.68), and half‐life was 24.01 hours (mean; SD 9.70). There were no viral infections or serious adverse effects from the drug after 70 attacks in the treatment group and 96 attacks in the control group. CONCLUSIONS: C1 inhibitor concentrate is a safe, effective treatment for acute attacks of HAE.