Study to Assess the Tolerability and Safety of Ecallantide in Children and Adolescents With Hereditary Angioedema

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-INH (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