SC Youth Treatment With Hydroxyurea Effects
Phase: PHASE2
Conditions: Hemoglobin SC Disease
Sponsor: Baylor College of Medicine

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Treatment of Hemoglobin SC Disease 
 
Principal Investigator 
 
Vivien Sheehan MD, PhD 
 
Co-Investigators 
 
Donald Mahoney MD 
Amber Yates MD 
Alex George MD, PhD 
Ionela Iacobas MD 
 
 
Statistician 
Charles Minard, PhD 
 
 
 
 
                                  
Texas Children’s Hospital 
6621 Fannin St. 
Houston, TX  77030-2399
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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Abstract 
 
Decades of observational data, including landmark natural history studies from 
the Cooperative Study of Sickle Cell Disease (CSSCD), have documented that sickle 
cell disease (SCD) is a severe, debilitating hematological disorder.  Hydroxyurea has 
emerged as an excellent therapeutic agent for the pharmacological induction of HbF in 
patients with SCD, due to its ease of oral administration, modest toxicity profile, and 
clinical efficacy for preventing acute vaso-occlusive events.  However, all completed 
clinical trials have excluded patients with hemoglobin SC (HbSC), restricting the 
inclusion criteria to patients with HbSS or HbS0 disease. HbSC differs significantly in 
pathophysiology from HbSS, as HbC does not sickle, but instead causes cellular 
dehydration which potentiates sickling of HbS. HbSC patients demonstrate a wide 
variability of clinical courses and a rate of life threatening complications much higher 
than the general population.1 Many severely affected HbSC patients have been placed 
on hydroxyurea on a case by case basis,2,3 but there is no large scale prospective data 
on safety or efficacy of hydroxyurea in this subset of SCD patients.  
 
The primary objective of this Phase II clinical trial is to treat symptomatic HbSC patients 
prospectively with hydroxyurea to maximum tolerated dose (MTD), and monitor for 
improvement using the PedsQLTM 3.0 Sickle Cell Disease Module by comparing scores 
at entry and at 6 months.  
 
Secondary objectives for this trial are the following: 
 
Effect of hydroxyurea on the following laboratory values: 
o Whole blood viscosity  
o %DRBC  
o Fetal hemoglobin (HbF) levels  
o Mean corpuscular volume (MCV) 
o Mean corpuscular hemoglobin concentration (MCHC) 
o Hemoglobin (Hb) levels 
o Absolute reticulocyte count (ARC) 
o Absolute neutrophil count (ANC) 
o Liver function tests (LFT) 
o Creatinine  
o Lactate dehydrogenase (LDH)  
o Unconjugated bilirubin (u.bili) levels 
o Microalbuminuria as measured by routine urinalysis (UA) 
 
 
 
Genomic analysis of variants associated with HbF response and disease related 
complications. Sequencing will be performed by whole exome sequencing (WES) 
and traditional sequencing as indicated. 
 
 
Assessment of effect on retinopathy, sensorineural hearing loss or avascular 
necrosis (AVN) if found to be present at entrance screening. 
 
This study will enroll patients with HbSC disease from 5 through 21 years of age, who 
have a PedsQLTM 3.0 Sickle Cell Disease Module score of 80 or lower. 

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Table of Contents 
 
Study Abstract………………………………………………….……………………..…..1 
1.0     OBJECTIVES 
1.1   Primary Objectives .............................................................................. 4 
1.2   Secondary Objectives ......................................................................... 4 
2.0     BACKGROUND AND RATIONALE ............................................................. 4 
2.1   HbSC disease ..................................................................................... 4 
2.2   Role of viscosity on the pathophysiology of HbSC disease.................. 5 
          2.3   Hydroxyurea Therapy for HbSC disease: HbF response ..................... 7 
          2.4   Effect of hydroxyurea on whole blood viscosity…………….…….….….8 
          2.5   Variability of hydroxyurea response in sickle cell disease……...….…..8 
          2.6   Treatment rationale…………………………………………………… …..9 
 
2.7    PedsQLTM 3.0 Sickle Cell Disease Module ......................................... 9 
3.0     RESEARCH PARTICIPANT ELIGIBILITY CRITERIA 
          AND STUDY ENROLLMENT ...................................................................... 9 
3.1   Inclusion Criteria ................................................................................. 9 
3.2   Exclusion Criteria ................................................................................ 10 
3.3   Research Participant Recruitment and Screening ............................... 10 
3.4   Subject Recruitment and Informed Consent ........................................ 10 
4.0     STUDY DESIGN AND METHODS .............................................................. 10 
 4.1   Study Design ....................................................................................... 10 
 4.2   Methods .............................................................................................. 11 
5.0     CLINICAL AND LABORATORY EVALUATIONS ......................................... 12 
5.1   Special Instructions for Evaluations ..................................................... 13 
5.2   Medical Record Review ....................................................................... 14 
5.3   Off-Study Evaluations .......................................................................... 14 
6.0     OUTCOME MEASURES ............................................................................. 14 
7.0     CRITERIA FOR REMOVAL FROM PROTOCOL AND 
OFF-STUDY CRITERIA............................................................................. 15 
7.1   Off Study Criteria ................................................................................. 15 
8.0    SAFETY AND ADVERSE EVENT REPORTING REQUIREMENTS ............. 16 
9.0    DATA COLLECTION, STUDY MONITORING, 
             AND CONFIDENTIALITY ......................................................................... 16 
10.0    STATISTICAL CONSIDERATIONS ............................................................ 18 
11.0    STUDY DURATION.................................................................................... 19 
12.0    REFERENCES ........................................................................................... 19 
 
 
 
 
 
 
 
 
 
 

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1.0  
OBJECTIVES 
 
1.1  
Primary objective of this Phase II study: To determine if hydroxyurea, 
dosed to MTD, improves PedsQLTM 3.0 Sickle Cell Disease Module 
scores after 6 months on hydroxyurea at MTD compared to score at 
entry. 
 
1.2  
Secondary objectives of this study:  
 
1. To investigate the effect of hydroxyurea on HVR in HbSC patients 
treated with hydroxyurea.  
 
2. To investigate the effect of hydroxyurea use on %DRBC in HbSC 
patients. 
 
3. To investigate changes in the following laboratory values of HbSC 
patients using serial measurements monthly for the duration of the 
study:  
 
Fetal hemoglobin (HbF) levels as determined by HPLC in the 
hemoglobin profile 
 
Mean corpuscular volume (MCV) 
 
Mean corpuscular hemoglobin concentration (MCHC) 
 
Hemoglobin (Hb) levels 
 
Absolute reticulocyte count (ARC) 
 
Absolute neutrophil count (ANC) 
 
Complete metabolic panel (CMP) 
 
Lactate dehydrogenase (LDH)  
 
Unconjugated bilirubin (u.bili) levels 
 
Microalbuminuria as measured by routine urinalysis (UA) 
 
4. Genomic analysis of variants associated with HbF response and 
disease related complications in HbSC. 
 
5. Assessment of effect of hydroxyurea therapy on retinopathy, 
sensorineural hearing loss or avascular necrosis (AVN) if found to be 
present at entrance screening. 
 
     
 
2.0  
BACKGROUND AND RATIONALE 
 
2.1  
Hemoglobin SC disease 
Patients with hemoglobin SC disease are compound heterozygotes.  One 
beta globin gene contains the sickle mutation, glutamic acid to valine 
change at the 6th codon, and the other beta globin gene contains the C 
mutation, a change from glutamic acid to lysine, also at the 6th codon.  
Each erythrocyte contains HbS and HbC in an approximate 50:50 ratio. 

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Hemoglobin SC disease is one of the most common inherited diseases in 
the United States, affecting approximately 1 in 833 African-American live 
births.4  HbS undergoes intracellular polymerization in the deoxygenated 
state, leading to deformation of the red cell membrane and alteration of 
cellular physiology. While HbC does not polymerize, it increases the 
mean corpuscular hemoglobin concentration (MCHC) of the cell via 
volume regulated K+ efflux, thereby potentiating the polymerization of 
HbS.5  In vitro studies of HbSC red blood cells found that reduction of 
MCHC from 37 to 33 g/dL would restore normal red blood cell 
morphology.6  
 
 
 
Clinical manifestations of HbSS disease result primarily from chronic 
severe hemolytic anemia and the effects of repeated intravascular 
sickling of erythrocytes within the capillaries and small venules.  
Hemolysis leads to chronic anemia, gallstone formation, and intimal 
damage/hyperplasia within the arterial vasculature.  Red blood cell 
sickling leads to acute vaso-occlusive events with varied presentations, 
including painful events, priapism, splenic sequestration, acute chest 
syndrome, or stroke.  These processes occur in HbSC disease as well, 
but at 25-50% the frequency. Hemolysis in HbSC is reduced due to 
longer RBC survival, approximately 25% of a normal individual, or 28.9 
(+4) days, compared to less than 21 days in HbSS disease.7 
 
 
2.2  
Hydroxyurea Therapy for HbSC disease: HbF response 
 
Low levels of HbF in patients with SCD are associated with a variety of 
vaso-occlusive complications and an increased risk for early death.  In 
patients with HbSS, hydroxyurea provides an important therapeutic option 
for patients with SCD, since it increases the amount of HbF within 
circulating erythrocytes, can be administered orally with once-daily 
dosing, has minimal short-term adverse effects, and is clinically effective.  
In a randomized, double-blinded, placebo-controlled Phase III trial 
involving severely affected adults with homozygous HbSS, hydroxyurea 
therapy was associated with significantly fewer painful vaso-occlusive 
events, episodes of acute chest syndrome, erythrocyte transfusions, and 
hospitalizations compared to observation alone.8  The Multicenter Study 
of Hydroxyurea in Sickle Cell Anemia trial reported that adult patients 
treated with hydroxyurea had a 40% reduction in overall mortality after 9 
years of follow-up.9  In adults with SCD, hydroxyurea is well tolerated and 
leads to increases in hemoglobin concentration, mean corpuscular 
volume (MCV), and percentage HbF, as well as decreases in white blood 
cell and reticulocyte counts.10 
 
Similar efficacy for hydroxyurea therapy has been observed in children 
with HbSS.  A Phase I/II trial of hydroxyurea therapy in children 5 to 15 
years of age with severe clinical manifestations (HUG-KIDS) 
demonstrated similar safety and hematological toxicities and efficacy at 
MTD as seen in adults.11  Hydroxyurea was well tolerated and had no 

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negative effects on growth or development.12  The most common short-
term hydroxyurea toxicity was transient and reversible myelosuppression, 
primarily of the granulocyte series.  While there is compelling evidence for 
the effectiveness of hydroxyurea in HbSS, HbSC patients were not 
included in these studies.  
 
It has been hypothesized that HbSC patients may not benefit from 
hydroxyurea because adult patients have baseline HbF<5%, and exhibit 
little or no HbF induction on hydroxyurea.13  In a cohort of 10 adult HbSC 
patients treated with hydroxyurea at doses ranging 500-1000 mg per day, 
a significant increase in MCV was noted.  No significant change in HbF 
was noted for the group but one individual had a 6.8% rise in HbF.14   
 
A report by Dr. Russell Ware of 6 pediatric patients with HbSC disease 
treated with hydroxyurea at MTD between 1995 and 2002 in the Duke 
Pediatric Sickle Cell Program supports the clinical and hematological 
efficacy of hydroxyurea therapy in children with HbSC disease.  MCV 
increased significantly without increase in hemoglobin.  Additionally HbF 
percentage and percentage of F-cells increased.3  CHAMPS, a Phase II 
double blinded multicenter trial examined the efficacy of hydroxyurea and 
magnesium pidolate in children and adults with HbSC.  In this trial, 
participants who received hydroxyurea (± magnesium pidolate) had 
significant increases in MCV and HbF, without changes in hemoglobin 
level.  Additionally, children treated with hydroxyurea had greater 
increases in MCV and HbF after 24 weeks than adults.  Unfortunately, 
clinical conclusions from this trial were limited because of its incomplete 
enrollment and early termination. 15 
 
Another study of eight pediatric HbSC patients placed on hydroxyurea 
therapy demonstrated an increase in MCV, but only two patients had an 
increase in HbF. However, the hydroxyurea dose was not increased to 
MTD, but remained stable at 15 mg/kg.16 Of note, review of the medical 
charts of HbSC patients treated with hydroxyurea in our institutionfound 
the dose of hydroxyurea needed to reach MTD ranged between 15-
25mg/kg, average 20 mg/kg. This is significantly lower than the average 
dose of 30 mg/kg needed to reach MTD in HbSS patients;17 therefore, it is 
likely that a HbSC patient will reach MTD more rapidly, typically after 1-2 
dose increases. Two patients had hydroxyurea held for 
thrombocytopenia, two more for neutropenia. These reports also highlight 
the importance of establishing safe drug dose initiation and titration in 
HbSC patients, who may be more sensitive to the myleosuppressive 
effects of hydroxyurea than HbSS patients. 
 
 
 
 
 
 

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2.3  
Role of whole blood viscosity and hematocrit to viscosity ratio 
(HVR) in the pathophysiology of HbSS and HbSC disease: 
Recent reports have shown higher whole blood viscosity to correlate with 
more frequent pain events, leg ulcers, and ACS in patients with HbSS. 
Patients with HbSC disease have similar rates of AVN, and higher rates 
of proliferative sickle retinopathy (PSR), than HbSS patients. Pain events 
and ACS, while less frequent than in HbSS, still occur in HbSC, especially 
in adolescence. These observations lead some providers to offer 
therapeutic phlebotomy to symptomatic HbSC patients. A large series of 
179 HbSC patients treated with phlebotomy, reported 71% had significant 
reduction in pain events. The authors have recommended phlebotomy for 
all symptomatic adult HbSC patients with Hb greater than 10.5 g/dL. In 
this phlebotomy therapy applied to adult HbSC patients, the Hb set point 
reduction is achieved by inducing iron deficiency, an undesirable event in 
a developing child. It is therefore imperative that alternative therapies like 
hydroxyurea be thoroughly tested in pediatric HbSC patients prior to 
investigating phlebotomy as a therapeutic option.  
 
A more specific measure of SCD pathology is the HVR, a measure of 
oxygen carrying capacity, calculated by the ratio of hematocrit to viscosity 
at various shear rates. It is abnormally low at both high and low shear in 
HbSS and HbSC patients. Individuals with sickle cell related leg ulcers 
have a statistically significant lower HVR compared to sickle cell patients 
without leg ulcers. Since microcirculatory dysfunction is the root of SCD 
pathology, contributing to pain events, avascular necrosis and chronic leg 
ulcers, it is essential that SCD therapies are evaluated for their effect on 
HVR. Chronic transfusion therapy does not improve HVR, and may 
decrease HVR at low shear rates that model the venous circulation. 
 
The HVR has been calculated at high and low shear rates for 98 HbSS 
patients on hydroxyurea, 53 HbSC (untreated) and 43 HbSS (untreated),  
Table 1. Hydroxyurea treatment improved HVR in HbSS patients, 
indicating an increase in oxygen carrying capacity. HVR did not correlate 
with HbF in any of the three groups individually, or as a whole. It is 
encouraging that HVR, low in both HbSC and HbSS patients, significantly 
improves on hydroxyurea in a HbF independent manner, especially since 
few HbSC patients demonstrate a meaningful rise (final %HbF of 20% or 
more) in HbF on hydroxyurea. A secondary endpoint of this protocol is to 
evaluate the effect of hydroxyurea on HVR in HbSC patients. 
 
 
 
 
 
 
 
 
 

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Table 1: 
 
HbAA 
n=19 
HbSS, 
untreated 
n=43 
HbSS, on 
Hydroxyurea 
n=98 
HbSC 
n=53 
Age (years) 
15.4 ± 3.8 
10.4 ± 5.1 
10.7 ± 3.4 
10.5 ± 4.3 
Hemoglobin 
(gm/dL) 
13.5 ± 1.7 
8.5 ± 1.0 
9.9 ± 1.4 
11.0 ± 1.2 
Hematocrit (%) 
40.9 ± 5.3 
25.5 ± 3.1 
28.4 ± 3.7 
31.3 ± 3.2 
Viscosity (cP) at 
45s-1 
5.3 ± 0.9 
4.6 ± 1.2 
4.3 ± 0.9 
5.5 ±0.9 
HVR at 45s-1 
7.5 ± 0.9 
5.8 ± 1.1 
6.75 ± 1.0 
5.77 ± 0.7 
Viscosity (cP)at 
225s-1 
3.8 ± 0.5 
3.3 ± 0.5 
3.4 ± 0.5 
4.1 ± 0.5 
HVR at 225s-1 
10.3 ± 0.7 
7.7 ± 0.8 
8.53 ± 0.8 
7.72 ± 0.6 
 
 
 
2.4 
Role of % dense red blood cells (HVR) in the pathophysiology of 
HbSS and HbSC disease:  
 
Another contributor to SCD pathology is the abnormal density of the red 
cells. K+ efflux from red blood cells (RBC) decrease water content and 
increase hemoglobin concentration. Dense red blood cells, or DRBC’s, 
have a intracellular hemoglobin concentration of 40-50 g/dL, compared to 
a normal cell, with a hemoglobin concentration of approximately 33 g/dL. 
DRBCs are highly prone to sickling, have increased rigidity, and 
decreased stability. %DRBC correlated significantly with skin ulcers, 
priapism, and renal dysfunction. Hydroxyurea has been shown to 
decrease %DRBCs by 34% after 6 months of therapy in HbSS patients, 
independent of degree of HbF induction. Its impact on DRBC’s in HbSC 
patients is unknown; this determination is another secondary endpoint of 
our protocol. %DRBCs have been measured using Pthalate oil mixtures 
in the past; our ADVIA hematology system is able to measure % RBC in 
an automated fashion.   
 
 
2.5  
Hydroxyurea Response Variability in Sickle Cell Disease 
 
The response to hydroxyurea therapy in SCD is highly variable.18  
Patients are typically escalated to the MTD based on laboratory 
myelosuppression, aiming for an absolute neutrophil count of 1.0 – 3.0 x 
109/L.  With proper compliance, virtually every child with SCD will 
increase their HbF during hydroxyurea therapy at MTD, but the 
magnitude of the response varies from 10% to >30% in HbSS.  
Currently, there is no way to predict which child will have a high or low 
HbF response to hydroxyurea prior to reaching MTD for HbSS patients, 
much less the HbSC subtype.  We hypothesize that genetic differences 
beyond the sickle gene mutation influence the HbF response to 
hydroxyurea therapy, and that these differences may be found in the 
various SCD subtypes as well as HbSS.   

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2.6 
Treatment Rationale 
Patients with HbSC generally have a milder course than HbSS patients. 
However, a select number will have significant clinical complications in 
childhood, and a majority of patients with HbSC develop chronic organ 
damage in adulthood.  The potential efficacy of hydroxyurea to 
postpone, prevent, or even reverse chronic organ damage in patients 
with HbSC disease has not been determined for either children or adults.  
Viscosity and HVR is of major importance in the pathophysiology of 
HbSC disease. A small trial of hydroxyurea in HbSC patients showed a 
statistically rise in hemoglobin levels, which may increase whole 
viscosity.19 However, even a rise in hemoglobin may lead to an 
improvement in HVR, if other rheological benefits, observed in 
hydroxyurea treated HbSS patients, such as a reduction in dense cells, 
are also experienced in HbSC patients on hydroxyurea. In our study 
patients whose HVR drops 20% below baseline levels will be removed 
from the study. Serial measures of HVR in the same individual on 
different days in the PI’s laboratory exhibit 20% variability.  This is an 
important safety measure for patients who may experience a rise in 
whole blood viscosity and viscosity related complications on 
hydroxyurea, a theoretical concern.  
 
2.7  
PedsQLTM 3.0 Sickle Cell Disease Module 
The PedsQLTM 3.0 Sickle Cell Disease Module is based on frequently 
used generic health related quality of life tools (HRQL). It is a 43 item 
module, divided onto age ranges 5-7 years, 8-12 years, 13-18 years, and 
adult. It contains questionnaires to be administered to the patient and the 
parent. This clinical research tool has been validated, found reliable and 
feasible in a multi-center trial. Texas Children’s Hematology Center 
participated in this trial, where it was self-administered in the clinic setting 
where appropriate. The PedsQLTM 3.0 Sickle Cell Disease Module is not a 
standard clinic procedure, therefore utilization of the module will occur 
after consent.  
 
 
 
3.0  
RESEARCH PARTICIPANT ELIGIBILITY CRITERIA AND STUDY  
ENROLLMENT 
 
3.1 
Inclusion Criteria 
 
3.1.1 Diagnosis of HbSC disease 
3.1.2 Age from 5 to 21 years of age.  
3.1.3  Score equal or lower than 80 on the PedsQLTM 3.0 Sickle Cell 
Disease Module 
3.1.4    Have experienced a sickle cell disease related complication 
 
 

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3.2 
Exclusion Criteria 
 
3.2.1 Failure to meet inclusion criteria 
3.2.2    Hydroxyurea usage in the last 3 
                        months. 
 
3.2.3 Chronic RBC transfusion therapy 
 
3.2.4    Packed red blood cell transfusion in the last 3 months (temporary  
                        exclusion). 
3.2.5   Pregnancy, or refusal to use medically effective birth control if      
female and sexually active. 
 
 
3.3 
Research Participant Recruitment and Screening 
Study participants will be patients with HbSC disease who receive 
medical care from the Hematology Center of Texas Children’s Hospital. 
Recruitment of external participants will consist of those physicians and 
patients who contact the Texas Children’s Hospital principal investigator 
and express an interest in participating. Physicians and patients may 
learn of this study either through the www.clinicaltrials.gov website or via 
presentations at scientific meetings.  Of patients followed at Texas 
Children’s Hospital, all patients with HbSC disease will be consented prior 
to screening for eligibility with the PedsQLTM 3.0 Sickle Cell Disease 
Module.  Those with a score equal to or lower than 80, will be offered 
hydroxyurea therapy and invited to participate in this study.  The protocol 
will be explained to them and consent obtained by the Principal 
Investigator or designee.   
 
3.4       Subject Recruitment and Informed Consent 
Subjects will be recruited from the patient population followed at Texas 
Children's Hospital. All pediatric patients who meet eligibility criteria will 
be approached for consent at their scheduled physician/clinic visit.  
 
The Principal Investigator, Study Coordinator, or another member of 
the research team will confirm eligibility based on the criteria listed above, 
explain the protocol, and obtain informed consent from the subject's legal 
guardian(s) in accordance with federal regulations and IRB policies at 
Baylor College of Medicine. Where applicable, assent from the subject 
will also be obtained.  No undue coercion will be placed on subjects or 
parents to participate in the study 
 
 
4.0 
STUDY DESIGN AND METHODS 
 
4.1  
Study Design 
The primary objective of this Phase II study is to prospectively and 
uniformly treat symptomatic HbSC patients to MTD on hydroxyurea, and 
assess for clinical improvement using the PedsQLTM 3.0 Sickle Cell 
Disease Module after 6 months at MTD, compared to entrance scores. 

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Patients will be consented prior to screening for eligibility with the 
PedsQLTM 3.0 Sickle Cell Disease Module. 
 
Also examined will be the effects of hydroxyurea on HVR, %DRBC, Hb, 
HbF, MCV, MCHC, ANC and ARC. LDH and u bilirubin will be monitored 
as indirect measures of hemolysis. Hydroxyurea dose escalation to a 
stable MTD with evidence of mild myelosuppression will occur according 
to published guidelines.20  
 
This is an unblinded Phase II trial; all patients enrolled will be placed on 
open-label hydroxyurea. Drug effect will be determined based on change 
in laboratory values from baseline. All laboratory tests, red cell density 
and viscosity measures will be performed every two months. Testing will 
be performed on peripheral blood obtained during hydroxyurea monitoring 
visits.  
 
 
4.2  
METHODS 
 
4.2.1. Viscosity measurements 
Measures of whole blood viscosity will be performed according to current 
guidelines.21 Whole blood will be obtained at routine clinic visits and 
collected in EDTA tubes, and analyzed within 4 hours of venipuncture. All 
specimens will be warmed to 37oC prior to measurement. A Brookfield 
cone and plate viscometer in Dr. Sheehan’s laboratory will be used. 
Samples will be run at moderate and high shear stress, 45 s-1 and 225 s-1 
respectively, at 37oC.  0.5 mL of whole blood will be used for each 
measure. The sample used for viscosity measures will also be analyzed 
on the ADVIA 120 hematology analyzer in order to measure the red cell 
density. 
 
 
4.2.2    Laboratory measurements 
Routine clinical laboratory assays will be performed at Texas Children’s 
Hospital clinical laboratories. Research lab assays will be performed in Dr 
Sheehan’s laboratory.  ADVIA and measurements will be used for 
research purposes only, to determine %DRBC. 
 
4.2.3. Studies of phenotypic variability 
The HbF response will be evaluated as both a continuous and a 
categorical variable.  Change in HbF at MTD will be analyzed as a 
continuous variable using linear regression analysis.  Peripheral blood 
mononuclear cells will be isolated from 5mL venous blood, and genomic 
DNA will be purified using standard laboratory techniques.  Small aliquots 
of DNA will then be tested for genetic variations that could modify the 
baseline and treatment HbF levels.  Analyses will be performed to identify 
gene polymorphisms associated with HbF response and other laboratory 
and clinical variables.   
 
 

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5.0 
CLINICAL AND LABORATORY EVALUATIONS  
 
Hydroxyurea Dosing Parameters: 
Initiation: Initiate hydroxyurea (HU) at 10 mg/kg daily, with the 
exact dose rounded up or down to the nearest practical dose based on 
formulation. The actual starting dose should be within 2.5 mg/kg of the 
calculated 10 mg/kg dose. A liquid formulation of hydroxyurea may be 
used for children unable to swallow pills, or to improve dosing accuracy. 
 
Dose escalation: Escalate HU dose by 5 mg/kg/day every 8 
weeks up to a maximum dose of 35 mg/kg/day if blood counts meet 
escalation criteria prior to dose increase (Table 3). 
 
Response to Toxicity: Hematologic toxicity: If one or more blood 
counts fall into the toxic range, stop hydroxyurea and recheck blood 
counts weekly. Restart hydroxyurea at the same dose if the affected blood 
counts recover within 1 week. Reduce hydroxyurea dose by 2.5 mg/kg if 
toxicity persists for more than 1 week or if there is a previous history of 
toxicity at the current dose. 
  
Non-hematologic toxicity: Hydroxyurea will be held if liver function tests 
rise to twice the upper limit of normal, or if creatinine rises to 1.5 the upper 
limit of normal. Relevant laboratory values will be rechecked weekly, and 
hydroxyurea restarted at a reduced dose, 2.5 mg/kg lower than the dose 
at which non-hematologic toxicity was experienced. 
 
Definition of MTD: dose of hydroxyurea at which ANC is between 1000 
and 3000/μL, OR ARC is between 70,000 and 100,000/μL, or platelet 
count is between 70,000 and 100,000/μL on CBC. 
 
In order to evaluate the effectiveness of hydroxyurea therapy in HbSC 
patients, patients must remain at MTD through the 6 month evaluation 
period. MTD is defined in this protocol. If a study participant is not at MTD 
at a given clinic visit after achieving MTD at the current dose, the 
laboratory values and PedsQLTM 3.0 Sickle Cell Disease Module scores 
will not be included in the study analysis, and an additional month will be 
added to the study duration. 
 
 
 
 
 
 
 
 

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Table 2: Schedule of Evaluations 
 
 
Entry 
Scheduled 
Clinic Visits * 
Exit 
PedsQLTM 3.0 Sickle 
Cell Disease 
Module 
x 
x 
x 
X-ray bilateral 
shoulders 
 
x 
 
x 
X-ray bilateral hips 
x 
 
x 
Retinal exam 
x 
 
x 
Sensorineural 
hearing test 
x 
 
x 
Genomic DNA 
extraction from 
peripheral blood 
x 
 
 
CBC with 
differential 
ARC 
Hemoglobin profile 
CMP 
LDH 
u. bili 
x 
x 
x 
UA/microalbumin * 
x 
 
x 
Whole blood 
viscosity 
x 
x 
x 
%DRBC 
x 
x 
x 
* Microalbumin will be measured at study entry and exit only if within normal limits at entry. If above 
normal limits, it will be measured at * scheduled clinic visits occuring every two months .Retinal 
exam, x-rays, and sensorineural hearing tests must be no older than one year, or obtained within 2 
months of study entry. Baseline studies may be obtained at or before second study visit. 
 
 
5.1   
Special Instructions for Evaluations 
Whole blood viscosity measures will be performed on blood collected in 
EDTA vacutainer tubes, on a Brookfield cone and plate viscometer. 
Measures will be taken no more than 4 hours after sample collection, at 
shear rates of 45 and 225 s-1. Red cell density will be obtained using an 
ADVIA hematology analyzer.  
 
 
5.1.1  Laboratory Evaluations: All laboratory testing, excepting microalbumin, 
whole blood viscosity and red cell density measurements, are currently 
obtained as a part of routine clinical management every 2 months in 
patients with SCD who are initiating hydroxyurea therapy.  

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Vital Signs, weights and measures will be recorded during the subject’s 
participation in the study. Results of laboratory studies for all study 
participants will be collected in the study database for future analysis.  
 
 
 
Table 3: Criteria for Hydroxyurea escalation and cessation 
 
 
 
5.2       Medical Record Review 
Study personnel will review the subject’s medical record to abstract all 
laboratory test results and other testing obtained as described for this 
study, for the study duration. We will also review the history of disease-
related complications from birth. We would like to monitor significant 
clinical events on an ongoing basis as well, for the duration of the study 
and the two year post-study observation period if indicated.  Key areas to 
be collected include information such as: 1) pain episodes 2) acute chest 
syndrome 3) stroke or transient ischemic attacks, 4) acute splenic 
sequestration, 5) death.   
 
Specific diagnoses, rather than signs or symptoms will be recorded 
whenever possible. 
 
 
5.3 
Off-Study Evaluations 
 
 
No off study evaluations will be required.  
 
 
6.0  
OUTCOME MEASURES 
 
6.1 
Peds QL Sickle Cell ModuleTM scores 
6.2 
Whole blood viscosity and HVR 
6.3 
%DRBC 
6.4 
Laboratory analysis 
6.5 
Observed disease related complications during study period, 
compared to same duration of time immediately preceding study 
entry. 
6.6 
Variability in Hydroxyurea Response: The genetic basis for 
hematological variability of HbF induction for children receiving 
Laboratory value 
Toxicity Criteria (Any) 
Escalation Criteria 
(All Must be Met) 
ANC (per uL) 
< 1000 
> 3000 
ARC (per uL) 
<70,000 
> 100,000 
Platelets (per µL) 
< 70,000 
> 100,000 

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hydroxyurea therapy at maximum tolerated dose (MTD) will be 
assessed, through collection of genomic DNA, which will be 
submitted for whole exome sequencing under NHGRI 
U54HG003273. This sequencing information may also be used to 
investigate associations between variants and disease related 
complications. 
 
 
 
 
 
7.0 
CRITERIA FOR REMOVAL FROM PROTOCOL AND  
OFF-STUDY CRITERIA 
 
7.1 
Off-Study Criteria 
 
 
1) Subject decides to no longer participate in the study 
 
2) Pregnancy 
 
3) Investigators may discontinue any subject at their discretion, if in their 
professional opinion, the subject’s health, safety, and/or well-being is 
threatened by continued participation in the study.  
 
4) Subject decides to stop hydroxyurea treatment permanently 
 
5) Reduction of more than 20% below baseline of HVR 
 
6) Lost to follow-up—a letter will be sent to the last known address of 
study participants who are lost to follow up informing them that they are 
being taken off-study. 
 
7) Death 
 
8) If a study patient requires a transfusion for any reason, they will be 
removed from the study for a duration of 3 months, while continuing on 
hydroxyurea during that period. At the end of the 3 months, they will 
resume all normal study activities.  
 
 
 
 
 
 
 
 
 
 

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8.0 
SAFETY AND ADVERSE EVENT REPORTING REQUIREMENTS 
 
This protocol has a category 2 risk, research involving greater than minimal risk, 
but presenting the prospect of direct benefit to the individual subjects. Monitoring 
and reporting of adverse events will comply with the BCM Institutional Review 
Board requirements.  
 
Subjects on study will have scheduled clinic visits every two months, and 
laboratory evaluations throughout the period of dose titration to MTD and clinical 
observation, totaling 12 months. During these visits, they will be closely 
monitored for any clinical or laboratory evidence of toxicity associated with 
hydroxyurea or study participation.  All toxicities and adverse events will be 
scored utilizing criteria listed in the Common Terminology Criteria for Adverse 
Events (CTCAE) version 4.0 and toxicities ≥ grade 3 will be included in the visit 
data collection. Further assessment, testing, and interventions for any adverse 
events, including hydroxyurea dose reduction or interruption of therapy, will be 
performed according to section 5.0, Response to Toxicity. Subjects with severe 
(grade 3 or worse) toxicities or adverse events will be reviewed in detail by the 
study P.I. in conjunction with the Study Coordinator and primary clinician and will 
be considered for termination from the study. The Principal Investigator will 
provide a Continuing Review Report to the Baylor College of Medicine IRB at 
least annually. In addition, all serious adverse events and UPIRSOs that meet 
reporting criteria as defined by the BCM IRB will be submitted to the BCM IRB 
per their policy. Expected adverse events will not be reported, only adverse 
events related to hydroxyurea and study participation. 
 
 
All safety data collected on study participants will be reviewed by the Texas 
Children’s Non-Cancer Data Review Committee (TXCH DRC). An interim 
analysis for safety and efficacy will be performed when half of the enrolled 
participants have reached the 6 month point. 
 
 
 
 
9.0 
DATA COLLECTION, STUDY MONITORING, AND CONFIDENTIALITY 
 
Data collection and data management for this investigation will be conducted 
through the BCM Department of Pediatrics, Section of Hematology-Oncology. 
Co-investigators assigned to this protocol will be responsible for assisting the PI 
in assuring protocol compliance as well as reviewing, transcribing and tracking of 
all clinical and safety related data.  All personnel will receive Human Subjects 
Protection training with appropriate annual updates as required. 
 
Each subject’s medical record will be reviewed and existing data will be collected 
that is relevant to this study.  

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Clinical data will be transcribed from source documents directly into an electronic 
database.  This database will be password protected and accessible only to the 
Principal Investigator and her designated staff. 
 
Copies of the subject’s Informed Consent document will be maintained in a 
locked file in the BCM Department of Pediatrics, Section of Hematology-
Oncology 
 
 
Confidentiality 
Protocol Accession Numbers assigned in the Patient and Protocol Management 
(PPM) will be used in place of an identifier such as a medical record number. No 
research participant names will be recorded on documents used in data analysis, 
or used on any documents submitted for publication of study results. 
 
9.1      Potential Risks 
 
All patients in this study will be on hydroxyurea, which has repeatedly been 
shown to be safe and cause minimal side effects in patients with sickle cell 
disease when used with appropriate clinical monitoring. The most common side 
effects associated with hydroxyurea therapy are a drop in infection fighting cells, 
or white blood cells, a drop in platelet count, stomach discomfort, skin 
discoloration or roughness, blood may become thicker and less efficient at 
carrying oxygen and mild hair loss. Most patients taking hydroxyurea do not 
experience these symptoms.  
 
Potential risks include the risks associated with laboratory blood draws, which will 
be minimized by the use of careful sterile technique when drawing blood from 
peripheral veins or venous access lines that are already in place.  The blood 
volume (total 3 mL per sampling point) being procured for this study is well within 
our local institutional guideline for maximal volume allowed for the smallest 
potential study subject.   
 
Subjects may risk loss of confidentiality pertaining to protected health information 
obtained during the study.  To minimize this risk, these data will be collected and 
stored using coded identifiers, locked storage facilities and password-protected 
databases, each accessible only to the investigators.   
 
There exists a small potential for special risks to privacy relevant to the collection 
and storage of specimens for DNA, and the planned posting of coded genomic 
sequences to dbGaP.  As the study of these specimens will be restricted solely to 
identify gene polymorphisms in low versus high Hydroxyurea responders, and 
stored samples will be labeled only by coded identifiers, these special risks will 
be minimized.      
 
 
 
 

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10.0 
STATISTICAL CONSIDERATIONS 
 
 
The primary outcome measure of interest is the change in PedsQL 3.0 Sickle 
Cell Disease Module score at 6 months after achieving MTD compared with 
baseline. Previous research suggests that the standard deviation (SD) of scores 
is expected to be about 20 points.22 Assuming SD=20 at each time point and a 
correlation between repeated measures of 0.50, a sample size of 34 subjects 
would be required to detect a 10 point change in scores at 6 months versus 
baseline with 80% power using a two-sided, paired t-test. Therefore, a total of 41 
subjects will be recruited for this study to allow for a 20% attrition rate. Baseline 
patient characteristics will be summarized by means with standard deviations, 
medians with 25th and 75th percentiles or frequencies with percentages as 
appropriate.  
 
A two-sided, paired t-test will be used to test the primary null hypothesis that 
there is no change in PedsQL 3.0 Sickle Cell Disease Module score at 6 months 
after achieving MTD versus baseline. Statistical significance will be assessed at 
the 0.05 level. This hypothesis will also be tested using a general linear mixed 
model. The mixed model will use all available data, include a fixed effect for time 
(discrete) and will assume an unstructured matrix of correlated error terms.  
Approximate normality will be qualitatively assessed using quantile-quantile plots, 
and data transformations will be used if required. The mixed model will also be 
used to explore associations between the primary outcome measure and 
baseline characteristics, simultaneously adjusting for time. A similar mixed model 
will also be used to simultaneously assess differences from baseline at all 
repeated, every two months time points up to 12 months post-study entry. P-
values will be adjusted using Holm’s step-down Bonferonni correction, and 
statistical significance will be assessed at the 0.05 corrected level. 
 
Secondary outcome measures, including HVR, %DRBC, Hb, HbF, MCV, MCHC, 
ANC, ARC, LDH and unconjugated bilirubin will be similarly assessed. Baseline 
values will be compared to laboratory values obtained at stable MTD (5 months 
or longer at MTD) using a two-sided paired t-test. Laboratory values that differ 
significantly between baseline and MTD will be analyzed by simple linear 
regression. 
 
Samples collected for genetic testing will be subjected to whole exome 
sequencing, and analyzed for the association between change in HbF at MTD 
and exonic variants using linear association and burden analysis. Other 
phenotypes of interest, such as HVR, %DRBC, or SCD related complications 
may also be investigated in a similar manner, together with non-study 
participants 
 
Subjects who stop HU therapy for any reason (e.g., pregnancy, toxicity, SCD 
complications requiring other intervention, non-adherence to medication dosing, 
patient or family’s request to discontinue therapy) will be considered off-therapy.  

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Subjects who miss two or more follow-up evaluations will be sent a letter 
indicating that they are “off-study”.  
 
 
11.0  STUDY DURATION 
 
 
This protocol describes a planned 12 months of therapy. At the end of this 
period, study participants will be asked if they would like to participate in a 2 year 
observation period. In this observation period, the laboratory tests and  
PedsQLTM 3.0 Sickle Cell Disease Module scores that were obtained every two 
months during the 12 months of the study will be administered at each clinic visit, 
scheduled according to clinic guidelines and individual need.  
 
 
 
 
12.0 
REFERENCES 
 
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3. 
Miller MK, Zimmerman SA, Schultz WH, Ware RE. Hydroxyurea therapy for 
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Motulsky AG. Frequency of sickling disorders in U.S. blacks. N Engl J Med 
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8. 
Charache S, Terrin ML, Moore RD, et al. Effect of hydroxyurea on the frequency 
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Steinberg MH, Barton F, Castro O, et al. Effect of hydroxyurea on mortality and 
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Schroeder WA, Powars DR, Kay LM, et al. Beta-cluster haplotypes, alpha-gene 
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Lee K, Prehu C, Merault G, et al. Genetic and hematological studies in a group of 
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Wang W, Brugnara C, Snyder C, et al. The effects of hydroxycarbamide and 
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16. 
Iyer R, Baliga R, Nagel RL, et al. Maximum urine concentrating ability in 
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17. 
Ware RE. How I use hydroxyurea to treat young patients with sickle cell anemia. 
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18. 
Zimmerman SA, Schultz WH, Davis JS, et al. Sustained long-term hematologic 
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Steinberg MH, Nagel RL, Brugnara C. Cellular effects of hydroxyurea in Hb SC 
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Ware RE. How I use hydroxyurea to treat young patients with sickle cell anemia. 
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Baskurt OK, Boynard M, Cokelet GC, et al. New guidelines for hemorheological 
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Panepinto JA, Torres S, Bendo CB, et al. PedsQL sickle cell disease module: 
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