Inhaled Tissue Plasminogen Activator for Acute Plastic Bronchitis

Background and Rationale: Plastic bronchitis (PB) is a rare, disease characterized by the
formation of obstructive fibrin airway casts. Presently, acute exacerbations of the illness
are often treated with inhaled tissue plasminogen activator (tPA), in part, because there are
no FDA approved treatments. To date, there has been no safety or efficacy testing of inhaled
tPA. In addition, there is presently no reliable marker that could be used to assess adverse
drug events. However, in the absence of inhaled tPA treatment, PB-induced respiratory
distress can be severe, often warranting urgent or emergent bronchoscopy for cast removal, or
can sometimes result in respiratory failure. This clinical trial will address the unmet need
for safety and efficacy testing of inhaled tPA and for assessing biomarkers of drug response.

Objectives and Endpoints: This is an open-label, multi-center clinical trial of inhaled tPA
for the treatment of acute PB. The objectives of this protocol are to: 1) test the safety and
efficacy of an inhaled tPA regimen in children with PB; and 2) identify potential candidate
biomarkers of inhaled tPA drug response. Safety endpoints will consist of the development of
new, active bleeding that is systemic and/or pulmonary and/or new hematuria (defined as gross
hematuria). Secondary endpoints of efficacy will also be measured (e.g., frequency of cast
production). Urine and blood will also be collected for the development of potential
biomarkers of inhaled tPA drug response.

Assessments: Enrolled subjects will be routinely clinically monitored and blood work will be
assessed for the development of new, active bleeding that is systemic and/or pulmonary or new
gross hematuria. Levels of oxygenation and pulmonary function will be assessed during the
study period. We will also include the incidence of expectorated casts as a measurement of
efficacy.

Statistical Methods: This is an open-label study of 24 subjects with PB that will serve as
their own controls. A group of age-matched healthy subjects (n=12), Fontan subjects without
PB (n=12), and Fontan subjects with protein losing enteropathy (PLE) (n=12) will serve as
controls for biomarker assay development. The incidence of new, active bleeding events and
the frequency of airway cast expectoration will be assessed in subjects with PB. PLE is
another illness that is associated with congenital heart disease in children that has been
surgically remedied by the Fontan procedure.

The active treatment arm (inhaled tPA) will be conducted across six clinical centers. In
addition, these centers will enroll PLE control patients. All other control subjects will
only be enrolled at the University of Michigan.

The outcome measures only pertain to tPA treated patients. Since the control subjects are not
included in the outcome analysis, recruitment/enrollment status pertains to the PB patients.
The University of Michigan has initiated enrollment of healthy control subjects and there
have been consented subjects.

Inclusion Criteria (patients with plastic bronchitis):

1. ≥ 5 years of age but ≤18 years of age and weigh at least 18.6 kg (41 lbs).

2. Patients with CHD that have a history of PB with previous airway cast production.

3. Patients without CHD that present with an acute exacerbation of PB, defined as the
expectoration of, or a bronchoscopy retrieved, fibrin PB cast that causes acute
respiratory distress (e.g., severe coughing, difficulty breathing, dyspnea) or a
history of PB with pathologic evidence of fibrin airway cast production. Either a cast
sample (at least ½ inch (~4cm)) or a pathology report that documents PB cast fibrin
content must be submitted to the UM pathology core.

4. Must be able to use a mouthpiece nebulizer.

5. Informed consent (with parental if age ≥14 years) or assent for age ≥10 and < 14 years
old with parental informed consent.

Exclusion Criteria (patients with plastic bronchitis):

1. Known contraindication(s) to the use of tPA, including:

- active internal bleeding;

- history of cerebrovascular accident;

- recent intracranial or intraspinal surgery or trauma;

- intracranial neoplasm, arteriovenous malformation or aneurysm;

- known bleeding diathesis;

- and/or severe uncontrolled hypertension

2. Body weight >/= 100th percentile or BMI > 30

3. Known cystic fibrosis

4. Currently receiving inhaled tPA and/or dornase-alpha and/or inhaled unfractionated or
low molecular weight heparin

5. Protein losing enteropathy

6. Liver dysfunction (defined as ≥ 3X the normal levels of one or both liver
transaminases)

7. Need for concomitant intravenous or sub-cutaneous anti-coagulation with resulting
anti- Xa levels > 0.5 (low molecular weight heparins) or > 0.3 (unfractionated
heparin)

8. International normalized ratio (INR) > 2.0 if not receiving warfarin

9. Patients being actively treated for thrombosis

10. Concomitant use of a thienopyridine class antiplatelet agent (e.g., clopidogrel)

11. A platelet count of < 100,000 platelets/µL

12. A hematocrit <30%

13. Gross hematuria on screening urinalysis

14. Pregnant or lactating women (negative pregnancy test required for girls/women of
childbearing potential at the time of inhaled tPA administration). All women of child-
bearing potential must be willing to practice appropriate contraception throughout the
study.

Inclusion Criteria for Healthy Controls

1. Healthy children ≥ 5 years of age but ≤18 years of age with no other underlying
concomitant illness or chronic medication use (with the exception of vitamin
supplements)

2. Weigh at least 18.6 kg (41 lbs)

Inclusion Criteria for Healthy Fontan Controls

1. Children ≥ 5 years of age but ≤18 years of age with uncomplicated Fontan physiology
with no history of PB, other Fontan-associated complications (e.g., hepatopathy, PLE),
or other concomitant illnesses (e.g., asthma).

2. Weigh at least 18.6 kg (41 lbs)

Inclusion Criteria for PLE Fontan Controls

1. Children ≥ 5 years of age but ≤18 years of age with Fontan physiology, no history of
PB and a diagnosis of PLE defined as clinically symptomatic hypoproteinemia and/or
enteral protein loss.

2. Weigh at least 18.6 kg (41 lbs)

Exclusion Criteria for Healthy, Fontan Controls and PLE controls

1. Exceed the 100th percentile for body weight or have a BMI greater than 30.

2. History of post-operative chylothorax following any palliation surgery (Fontan
patients).

3. Known liver dysfunction per medical record review (e.g., liver transaminases of > 3X
normal).