Trial of Zileuton CR in Children and Adults With Sickle Cell Disease

Inflammation is now recognized as central to the pathophysiology of sickle cell disease
(SCD), and is manifest as leukocytosis, elevated levels of inflammatory cytokines, and
activation of monocytes, polymorphonuclear leukocytes (PMN) and endothelial cells. It is
present at steady state and is strongly associated with acute events, acute chest and early
mortality. Inflammation contributes to endothelial cell dysfunction, potentiates
vaso-occlusion, and may also give rise to the airway hyper-reactivity (AHR) that often
accompanies SCD. A spectrum of lung disease is seen in this patient population, from AHR
and obstructive lung disease in children, to restrictive lung disease and pulmonary vascular
remodeling in adults.

Evidence from our laboratory suggests that a specific angiogenic cytokine, Placenta Growth
Factor that is produced by hyperplastic erythroid marrow cells and elevated in SCD,
contributes to activation of monocytes and endothelial cells by inducing a key leukotriene
(LT) synthetic enzyme, 5-Lipoxygenase (5LO). 5LO increases production of LT. LT are among
the most potent inflammatory mediators known. LT-B4 is a very potent chemoattractant and
activator of PMN and enhances endothelial cell activation, and cysteinyl LT produce airway
smooth muscle constriction and inflammation in lung. Elevated LT-B4 and cysteinyl LT, and a
high incidence of AHR are observed in patients with SCD. Zileuton (ZL) is a specific
inhibitor of 5LO that decreases LT production, and is FDA-approved for treatment of asthma
for individuals 12 years of age or older. In the context of SCD, ZL reduced adhesion of PMN
and sickle RBC to rat pulmonary vasculature. In vitro data shows that ZL also increased
fetal hemoglobin (HbF) production from erythroid cells in vitro, and could have
additive/synergistic effects with hydroxyurea (HU). Thus, ZL may be beneficial in SCD by
reducing inflammation, mitigating AHR, and increasing HbF.

We hypothesize that inhibition of 5LO activity with ZL will be safe, feasible; will
significantly reduce leukotrienes and biomarkers of inflammation, will decrease AHR; and
will induce HbF in patients with SCD.

We will test this hypothesis in a Phase I study of ZL in SCD. First, we will establish a
safe dose of ZL and its pharmacokinetics in patients with SCD. The secondary objectives will
be to determine its pharmacodynamic effects on biological endpoints and compliance to twice
daily ZL administration.

Inclusion Criteria:

- Confirmed diagnosis of SCD (HbSS,HbSC,HBS Beta thalassemia, or HBS 0 thalassemia)

- Absence of an acute sickle event or ACS in the last 4 wks

- Not on hydroxyurea

- Ability to swallow pills

- Ability to comply with pulmonary function testing

Exclusion Criteria:

- History of active hepatitis

- HIV positivity

- Pregnant or nursing

- Unable to comply with contraceptive measures

- On an investigational drug within 4 weeks

- On hydroxyurea, leukotriene antagonists (e.g., Singulair) or steroids,
theophylline, coumadin, terfenadine or beta-2 blockers that affect the airway:
carteolol, carvedilol, labetalol, nadolol, penbutolol, pindolol, sotalol and timolol,
or on propranolol for the last four weeks

- On chronic transfusion therapy

- A serious, concurrent illness that would limit ability to complete or comply with the
study requirements

- Males who drink alcoholic beverages >5-6 drinks/day or females who drink alcoholic
beverages >3-4 drinks/day