Ecallantide (DX-88) for acute hereditary angioedema attacks: integrated analysis of 2 double-blind, phase 3 studies

Hereditary angioedema (HAE) is a rare disorder characterized by recurrent angioedema attacks. Ecallantide, a novel plasma kallikrein inhibitor, inhibits production of bradykinin, the key mediator of these angioedema attacks.

We sought to further characterize the safety and efficacy of ecallantide for HAE attacks by performing an integrated analysis of pooled data from 2 phase 3 studies.

An integrated analysis was conducted with data from 2 randomized, double-blind, placebo-controlled studies in which patients with HAE (age ≥10 years) received 30 mg of subcutaneous ecallantide or placebo within 8 hours of onset of a moderate-to-severe attack at any anatomic site. Efficacy was evaluated by using validated patient-reported outcome measures: the Mean Symptom Complex Severity (MSCS) score and the Treatment Outcome Score (TOS).

Compared with placebo, ecallantide resulted in significantly greater reduction in MSCS scores from baseline to 4 hours after dosing (ecallantide [mean ± SD], -0.97 ± 0.78; placebo, -0.47 ± 0.71; P < .001) and a significantly greater increase in TOSs at 4 hours (ecallantide, 55.5 ± 46.5; placebo, 20.0 ± 58.9; P < .001). Significantly greater symptomatic improvement over placebo occurred through 24 hours after dosing (MSCS score, P = .028; TOS, P = .039). Ecallantide demonstrated efficacy at all attack sites. The incidence of treatment-emergent adverse events was similar between groups.

This integrated analysis supports and expands on the results of the phase 3 studies. Ecallantide appears to be effective and well tolerated for the treatment of HAE attacks.