FDA approves kallikrein inhibitor to treat hereditary angioedema

Dyax Corp. on December 1 announced that FDA approved the marketing of the company’s ecallantide injection, or Kalbitor, for the treatment of acute attacks of hereditary angioedema in patients age 16 years or older. Ecallantide, the company said, binds to plasma kallikrein and blocks its binding site, resulting in less production of bradykinin, a vasodilator. According to the United States Hereditary Angioedema Association, most physicians and researchers have decided that bradykinin is the primary mediator of hereditary angioedema attacks, which can be fatal. The FDA-approved labeling for ecallantide states that the dose to treat an acute attack is 30 mg, given as three 10-mg s.c. injections. If the attack persists, a second 30-mg dose may be given within 24 hours. A boxed warning in the labeling states that the drug should be administered only by a health care professional who has medical support to manage anaphylaxis and hereditary angioedema. In the clinical studies of ecallantide for the treatment of hereditary angioedema, 2.7% of the 187 patients who received the drug by s.c. injection had an anaphylactic reaction within an hour, according to the labeling’s section on warnings and precautions. Symptoms included chest discomfort, pharyngeal edema, wheezing, and hypotension. Some 7.4% of the 68 patients who received the drug by i.v. injection had an anaphylactic reaction.