PI indicated departure from institution, inability to complete study.

The objective of this study is to evaluate the safety and tolerability of a single Subcutaneous (SC) dose of Ecallantide in children and adolescents with Hereditary Angioedema (HAE).

This pilot study is an open-label, non-randomized, single-arm study to evaluate the tolerability and safety of a single SC administration of ecallantide in up to approximately 10 pediatric subjects with HAE during an initial acute attack. The study is planned to enroll subjects 2 through 15 years of age who present with an acute cutaneous, abdominal, or laryngeal HAE attack. No more than 3 study sites will be included until a goal of 10 patients is achieved.

After treatment for an initial attack, one additional open label treatment with ecallantide will be offered to subjects contingent upon having been treated previously and presenting with a subsequent acute cutaneous, abdominal, or laryngeal attack of HAE at least 7 days after initial treatment. Open-label treatment for a second HAE attack will continue until 10 patients have been treated for an initial attack. Safety evaluations will be performed at each subsequent ecallantide-treated attack as for the initial treated attack

Inclusion Criteria:

1. 2 through 15 years of age, inclusive (ie, from the second birthday through the day prior to the sixteenth birthday) at the time of the subject's first attack.
2. Documented diagnosis of HAE type I or II. Diagnosis must be confirmed by a documented immunogenic (below the lower limit of normal) and/or functional (< 50% of normal levels) C1- Inhibitor deficiency. Diagnosis may be on the basis of historic data or by diagnostic testing conducted at the time of screening.
3. Informed consent (and subject assent as appropriate) signed by the subject's parent(s) or legal guardian(s).

Exclusion Criteria:

1. History of an adverse reaction (AE) to Ecallantide in the past
2. Diagnosis of angioedema other than HAE
3. Participation in another clinical study during the 30 days prior to treatment
4. Any known factor/disease that might interfere with the treatment compliance, study conduct, or result interpretation
5. Congenital or acquired cardiac anomalies that interfere significantly with cardiac function.
6. Treatment with angiotensin converting enzyme (ACE) inhibitors within 7 days prior to treatment.
7. Use of hormonal contraception within the 90 days prior to treatment for females of childbearing potential
8. The subject is pregnant or breastfeeding