Decitabine for High-Risk Sickle Cell Disease

Overview: Elevated fetal hemoglobin (HbF), whether pharmacologically induced or congenital,
has a favorable impact on the morbidity and mortality of SCD. The agent currently used to
elevate HbF, hydroxyurea (HU), has limited efficacy. There are mechanistic reasons to
believe that the DNA methyltransferase inhibitor 5-aza-2 -deoxycytidine (decitabine) can
more potently increase HbF. This has been demonstrated in vivo in animals and small phase
1/2 studies of decitabine in SCD subjects. Decitabine at low, non-cytotoxic doses was very
well tolerated and very efficacious at increasing HbF and total hemoglobin (Hb) in subjects
who did not respond to, or were intolerant of, HU. In addition to HbF levels, major
improvements were noted in a range of surrogate clinical endpoints measuring red blood cell
(RBC) adhesion, endothelial damage, and coagulation pathway activity. Also, substantial
clinical improvement was seen in severely ill patients treated off-label. The primary
objective herein is to provide evidence and guidance for a phase III study by demonstrating
the dose and schedule of decitabine that when given over a 12 month period, produces
sustained elevations in HbF without significant toxicity. Secondary objectives examine
patient reported outcome measurements (PROMIS), crisis frequency, and laboratory indices
that measure different domains of sickle cell pathophysiology and DNA methylation. These
secondary and scientific measurements will be correlated with each other and examined over
time to understand mechanisms of disease and the mechanism of action of the study drug.

Intervention: Decitabine starting dose of 0.2 mg/kg (range, 0.05-0.3 mg/kg) 1-2x/wk x 48
weeks

Hypotheses:

In SCD subjects at risk of early death, non-cytotoxic DNMT1 depletion using a metronomic
(frequent but intermittent) regimen of the nucleoside analogue decitabine directly
antagonizes a mechanism of gamma-globin repression, and produces sustained, clinically
significant HbF elevations.

Primary Objective: To measure, in high-risk SCD subjects, the effect of chronic metronomic
subcutaneous (SQ) decitabine administration on HbF levels. These aims are achieved through
the conduct of an extended, open-label, phase 2 study in subjects who remain at high risk of
early mortality and morbidity despite HU therapy.

Secondary Objectives: To measure, in high-risk SCD subjects, the effect of chronic
metronomic SQ decitabine administration on clinical and laboratory indices of safety,
patient reported outcome measures (PROMIS), frequency of crises, SCD pathophysiologic
activity (hemolysis, coagulation, platelet activation and inflammation), and molecular
effects of study drug.

Criteria for Evaluation:

Primary Endpoint: the percentage change in HbF level from baseline to the average percent
over the final 3 months of the study period (48 weeks).

Secondary Endpoints: clinical and laboratory assessment of safety, patient reported outcomes
(PROMIS), frequency of crises, quantity of F cells and F cell subsets, measurements of
hemolysis, coagulation, platelet activation, inflammation, endothelial damage, pulmonary
arterial pressure, DNMT levels, global and beta-globin locus specific DNA methylation.

Study Design: This is an extended, single arm, open-label, phase II clinical trial.

Study Population: Adults with symptomatic SCD who are at high risk of early mortality
despite greater than or equal to 6 months of HU therapy. Specifically, they still have: HbF
< 5 percent, OR 3 or more pain episodes per year requiring parenteral narcotics, OR 1 or
more acute chest syndrome episodes, OR hemoglobin < 9 g/dL and absolute reticulocyte count
(ARC) less than or equal to 250,000/mm(3). Subjects who meet the above criteria for high
risk but are unwilling or unable to tolerate HU are also eligible.

Clinical and Laboratory Evaluations:

Pre-treatment and every 2 weeks: CBC, chem 20 including LDH, and retic count

Pre-treatment and every 4 weeks: interim medical history & physical exam, HbF%, and
pregnancy test

Pre-treatment and every 12 weeks: urinanalysis, percent F-cells & percent F-reticulocytes,
biomarkers, scientific correlative studies of DNA methylation

Pre-treatment, 24 and 48 weeks: PROMIS, PFT, 6 minute walk, endo-PAT

Pre-treatment and 48 weeks: erythropoietin level

Follow-ups every 3-4 months between 52-54 weeks and 93-96 weeks: interim medical history &
physical exam, CBC, reticulocyte count, HbF percent, chem 20 (including LDH), and pregnancy
test

Sample Size: 40 subjects

Data Analyses: The effect of decitabine on HbF levels over time will be explored using a
general linear mixed model from which the average percent change from baseline to the
average HbF level on the final 3 months of treatment will be estimated along with a 95
percent confidence interval. AE and other safety measurements will be summarized by age
group, dose, and dose frequency at the time of AE onset. No interim analyses will be
performed in this study.

Human Subjects: There is a risk of neutropenia, thrombocytosis, and teratogenicity. Patients
must take precautions to use contraception and avoid pregnancy during treatment.

- INCLUSION CRITERIA:

Subjects who meet all of the following criteria are eligible for enrollment into the
study:

1. Age 18 years or older.

2. Written, informed consent provided by the subject before study entry.

3. Confirmed SCD (SS, S-beta (0)-thalassemia, or SC on hemoglobin electrophoresis),

4. Symptomatic SCD while on 6 months of HU OR symptomatic SCD and intolerant of HU
(unable or unwilling to tolerate HU due to hematological or other toxicities).
Symptomatic SCD is defined as having one of following:

- HbF < 5 percent, OR

- 3 or more pain episodes per year requiring parenteral narcotics, OR

- 1 or more acute chest syndrome episodes, OR

- Hemoglobin < 9 degree g/dL and ARC less than or equal to 250,000/mm(3),

5. Subject is in his/her steady state and not amidst any acute complication due to SCD.

6. Willing to use 2 forms of contraception. Some acceptable combinations include male
partner using condoms and female partner using oral contraceptives, male partner
using condoms and female partner who had bilateral oophorectomy, male partner who had
a vasectomy and female partner using injectable contraceptives (e.g. Depo Provera).

EXCLUSION CRITERIA:

Since the protocol targets an at risk population, and the tolerability and potential
benefits of this approach have been suggested in off-label treatment of seriously ill SCD
patients, the exclusion criteria are not overly stringent and are primarily directed at
avoiding teratogenic risks.

Subjects who meet any of the following criteria are disqualified from enrollment in the
study:

1. Inability to give informed consent.

2. Experienced severe sepsis or septic shock within the previous 12 weeks.

3. Last HU or erythropoietin dose obtained within the previous 4 weeks. Renal
replacement doses of erythropoietin is allowed as decitabine would not be expected to
exert a red cell and/or HbF response when there is no endogenous erythropoietin
production.

4. Participant is on chronic transfusion therapy (e.g., for history of TIA or stroke)
and medically contraindicated to discontinue transfusions.

5. Currently pregnant or breast-feeding.

6. Sexually active female of childbearing potential (all females except those who are
menopausal [appropriate age and no period for more than 12 months] or have had a
hysterectomy and/or bilateral oophorectomy) who is unwilling to use at least 2
acceptable methods of contraception as determined by the investigators. The use of a
condom by a male partner would be considered one acceptable method of contraception.

7. Sexually active male whose partner is of child-bearing potential and who is unwilling
to use at least 2 acceptable methods of contraception as determined by the
investigators during treatment and for 8 weeks after the last dose of decitabine.

8. Moribund or any concurrent disease (e.g., hepatic, renal, cardiac, metabolic) of such
severity that death within 24 weeks is likely.

9. Other experimental or investigational drug therapy in the past 28 days.

10. Inability to bring ANC above 2 x 10(9) cells/L or platelet count less than 1,000 x
10(9) cells/L.

For female participants: Not having heterosexual sexual contact starting 4 weeks before
beginning to take decitabine and continuing until 4 weeks after the last dose of
decitabine OR using TWO methods of birth control. One birth control method must be highly
effective, such as an Intrauterine Device (IUD), birth control pills, Depo-Provera
(medroxyprogesterone acetate) injections, or tying of the fallopian tubes. The other
additional effective method of birth control can be use of a diaphragm or a condom by the
male partner. Birth control should begin at the screening visit and continue until 4 weeks
after the last dose of decitabine. These steps must be taken even if the patient has a
history of infertility, unless the patient has had a hysterectomy or has not had periods
for at least 24 months.

For male participants: during decitabine treatment and 8 weeks after last dose of drug, a
condom must be used when engaging in any sexual contact with a woman of child-bearing age,
even in patients who have had a successful vasectomy.