BETHESDA, MD 02 December 2009—Dyax Corp. announced Tuesday that FDA has 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 (PDF) 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.

Dyax said the company and FDA jointly established a risk evaluation and mitigation strategy to communicate the risk of anaphylaxis from ecallantide therapy and the importance of distinguishing a hypersensitivity reaction from the symptoms of a hereditary angioedema attack.

The medication guide for the drug tells patients that the symptoms of a serious allergic, or hypersensitivity, reaction include wheezing, shortness of breath, cough, chest tightness, dizziness, faintness, fast or weak heartbeat, nervousness, reddening of the face, itching, hives, swelling of the throat or tongue, throat tightness, hoarse voice, difficulty swallowing, runny nose, and sneezing. The guide also states that the symptoms of a serious allergic reaction to ecallantide can be similar to the symptoms of a hereditary angioedema attack.

During the two placebo-controlled studies of ecallantide 30 mg by s.c. injection, the most frequent adverse events among patients who received the drug were headache, nausea, diarrhea, fever, injection-site reaction, and inflammation of the nasopharynx.

The company did not announce when it will make its new product available.

An operator at Kalbitor Access, which is handling inquiries from patients and health care providers, said shipments of the drug will start in early 2010. Those shipments, the operator said, will go to health care providers, not patients. A clinical staff member said she did not yet have the information to explain the logistics of ecallantide therapy.

Kalbitor will be supplied in cartons containing three 10-mg/mL single-use vials. Each vial contains 10 mg of the drug and should be kept at 2–8 °C.