Hydroxyurea Therapy for Children With Sickle Cell Anemia in Sub‐Saharan Africa: Rationale and Design of the REACH Trial

Background

Sickle cell anemia (SCA) is an inherited hematological disorder that causes a large but neglected global health burden, particularly in Africa. Hydroxyurea represents the only available disease‐modifying therapy for SCA, and has proven safety and efficacy in high‐resource countries. In sub‐Saharan Africa, there is minimal use of hydroxyurea, due to lack of data, absence of evidence‐based guidelines, and inexperience among healthcare providers.

Procedure

A partnership was established between investigators in North America and sub‐Saharan Africa, to develop a prospective multicenter research protocol designed to provide data on the safety, feasibility, and benefits of hydroxyurea for children with SCA.

Results

The Realizing Effectiveness Across Continents with Hydroxyurea (REACH, ClinicalTrials.gov NCT01966731) trial is a prospective, phase I/II open‐label dose escalation study of hydroxyurea that will treat a total of 600 children age 1–10 years with SCA: 150 at each of four different clinical sites within sub‐Saharan Africa (Angola, Democratic Republic of Congo, Kenya, and Uganda). The primary study endpoint will be severe hematological toxicities that occur during the fixed‐dose treatment phase. REACH has an adaptive statistical design that allows for careful assessment of toxicities to accurately identify a safe hydroxyurea dose.

Conclusions

REACH will provide data that address critical gaps in knowledge for the treatment of SCA in sub‐Saharan Africa. By developing local expertise with the use of hydroxyurea and helping to establish treatment guidelines, the REACH trial results will have the potential to transform care for children with SCA in Africa. Pediatr Blood Cancer © 2015 Wiley Periodicals, Inc.     

Adherence to hydroxyurea and clinical outcomes among children with sickle cell anemia

Objective

Hydroxyurea lowers the incidence of vaso-occlusive pain crises (VOC) and acute chest syndrome (ACS) among children with sickle cell anemia (SCA). Our objective was to assess the relationship between levels of adherence to hydroxyurea and clinical outcomes among children and adolescents with SCA.

Methods

This retrospective cohort study included Medicaid data (2005–2012) from Florida, Illinois, Louisiana, Michigan, South Carolina, and Texas. The study population consisted of children 1–17 years old with SCA enrolled in Medicaid for 3 years. Among children that initiated hydroxyurea, the medication possession ratio (MPR) was calculated as the proportion of days covered by hydroxyurea. Six months after initiation of hydroxyurea, clinical outcomes were assessed through the end of the study period: numbers of VOC-related inpatient admissions and emergency department visits, and encounters for ACS. Multivariable Poisson models were used to predict outcomes by MPR quartile adjusting for previous healthcare utilization, state, and age.

Results

Hydroxyurea was initiated by 515 children. The median MPR was 0.53 (interquartile range = 0.3–0.8). The annual median number of visits was 0.0 for ACS, 1.3 for VOC-related emergency department, and 1.4 for VOC-related inpatient admissions. For each outcome, the highest quartile of MPR had the lowest predicted count; this difference was significant for ACS visits when compared with the lowest quartile of MPR.

Conclusion

This study demonstrated a high level of adherence (>75%) was essential to achieve a lower incidence of common negative clinical outcomes. Further, moderate and severe hydroxyurea nonadherence may be more common than previously appreciated among children, emphasizing the importance of developing and testing innovative strategies to increase adherence.     

Effect of hydroxyurea on growth in children with sickle cell anemia: results of the HUG-KIDS Study

OBJECTIVES: Although hydroxyurea is effective in treating adults with sickle-cell anemia (SCA), there is concern that it may adversely affect growth in children. We report the growth characteristics of patients in the Phase I-II pediatric hydroxyurea trial (HUG-KIDS) before and during treatment at the maximum tolerated dose for one year. STUDY DESIGN: Children and adolescents with SCA (n = 68), aged 5 to 16 years at baseline, reached the maximum tolerated dose and had serial height, weight, and Tanner stage measurements. Data from the Cooperative Study of Sickle Cell Disease (CSSCD) were used for comparison. Mixed-effects models were used to compare serial measurements as a function of age and group. RESULTS: In girls, there were no significant differences in height or weight among the pretreatment, on-treatment, and CSSCD groups. Compared with the CSSCD group, HUG-KIDS boys were heavier starting at age 9 years, and pretreatment HUG-KIDS boys were taller starting at age 7 years. The Tanner stage transitions took place at appropriate ages. CONCLUSIONS: Hydroxyurea treatment had no adverse effect on height or weight gain or pubertal development in school-aged children with SCA.     

Secondary benefit of maintaining normal transcranial Doppler velocities when using hydroxyurea for prevention of severe sickle cell anemia

In a retrospective cohort study, we tested the hypothesis that when prescribing hydroxyurea (HU) to children with sickle cell anemia (SCA) to prevent vaso‐occlusive events, there will be a secondary benefit of maintaining low transcranial Doppler (TCD) velocity, measured by imaging technique (TCDi). HU was prescribed for 90.9% (110 of 120) of children with SCA ≥5 years of age and followed for a median of 4.4 years, with 70% (n = 77) receiving at least one TCDi evaluation after starting HU. No child prescribed HU had a conditional or abnormal TCDi measurement. HU initiation for disease severity prevention decreases the prevalence of abnormal TCDi velocities.     

Sickle cell anemia from central India: A retrospective analysis

Although sickle cell anemia in India is believed to have a mild clinical presentation, few studies report severe disease in many patients from central India. Hence, we have retrospectively studied 316 children with SCA who were followed up for a period of 5.8±5.7 years. There were 55.4 blood transfusions, 43.3 episodes of vaso-occlusive crises requiring hospitalization, and 108.9 hospitalizations per 100 person years. Ninety six (30%) patients had severe disease whereas 74 patients also fulfilled the criteria for hydroxyurea therapy. Significant proportion of children with sickle cell anemia from central India present with severe clinical presentation and require regular medical attention.     

Arterial spin-labeled perfusion combined with segmentation techniques to evaluate cerebral blood flow in white and gray matter of children with sickle cell anemia

Background

Changes in cerebral perfusion are an important feature of the pathophysiology of sickle cell anemia (SCA); cerebrovascular ischemia occurs frequently and leads to neurocognitive deficits, silent infarcts, and overt stroke. Non‐invasive MRI methods to measure cerebral blood flow (CBF) by arterial spin labeling (ASL) afford new opportunities to characterize disease‐ and therapy‐induced changes in cerebral hemodynamics in patients with SCA. Recent studies have documented elevated gray matter (GM) CBF in untreated children with SCA, but no measurements of white matter (WM) CBF have been reported.

Procedures

Pulsed ASL with automated brain image segmentation‐classification techniques were used to determine the CBF in GM, WM, and abnormal white matter (ABWM) of 21 children with SCA, 18 of whom were receiving hydroxyurea therapy.

Results

GM and WM CBF were highly associated (R² = 0.76, P < 0.0001) and the GM to WM CBF ratio was 1.6 (95% confidence interval: 1.43–1.83). Global GM CBF in our treated cohort was 87 ± 24 mL/min/100 g, a value lower than previously reported in untreated patients with SCA. CBF was elevated in normal appearing WM (43 ± 14 mL/min/100 g) but decreased in ABWM (6 ± 12 mL/min/100 g), compared to published normal pediatric controls. Hemispheric asymmetry in CBF was noted in most patients.

Conclusions

These perfusion measurements suggest that hydroxyurea may normalize GM CBF in children with SCA, but altered perfusion in WM may persist. This novel combined approach for CBF quantification will facilitate prospective studies of cerebral vasculopathy in SCA, particularly regarding the effects of treatments such as hydroxyurea. Pediatr Blood Cancer 2009;52:85–91. © 2008 Wiley‐Liss, Inc.     

Chemical and functional analysis of generic hydroxyurea formulations

Hydroxyurea has documented laboratory and clinical efficacy for children with sickle cell anemia (SCA), and has potential to become an effective and inexpensive treatment option for patients in countries with limited resources. Concerns exist, however, regarding product quality and manufacturing variability among different international vendors, particularly for generic formulations. To address these concerns, hydroxyurea capsules from 8 different pharmaceutical sources were analyzed using quantitative chemical and functional assays. All samples had measured values within 20% of expected results, with no significant differences observed among vendors. Generic hydroxyurea formulations represent a potent yet inexpensive therapeutic option for children with SCA worldwide.     

CHEMICAL AND FUNCTIONAL ANALYSIS OF GENERIC HYDROXYUREA FORMULATIONS

Hydroxyurea has documented laboratory and clinical efficacy for children with sickle cell anemia (SCA), and has potential to become an effective and inexpensive treatment option for patients in countries with limited resources. Concerns exist, however, regarding product quality and manufacturing variability among different international vendors, particularly for generic formulations. To address these concerns, hydroxyurea capsules from 8 different pharmaceutical sources were analyzed using quantitative chemical and functional assays. All samples had measured values within 20% of expected results, with no significant differences observed among vendors. Generic hydroxyurea formulations represent a potent yet inexpensive therapeutic option for children with SCA worldwide.     

Hydroxyurea therapy associated with declining serum levels of magnesium in children with sickle cell anemia

OBJECTIVE: To obtain quantitative serum levels of total and ionized magnesium (Mg(2+)) in children with homozygous sickle cell anemia (SCA) undergoing therapy with hydroxyurea. STUDY DESIGN: Five children, ages 11 to 14 years with homozygous SCA, were enrolled in a dose-escalating trial of hydroxyurea over an 18-month period. Serum levels of total and ionized magnesium together with ionized K(+), Na(+), and Ca(2+) were measured before hydroxyurea and every 6 months during hydroxyurea therapy. RESULTS: Before treatment, 4 of the 5 patients had low or below-normal serum concentrations of Mg(2+) (normal range, 0.51-0.67 mmol/L). All 5 became Mg(2+)-deficient during hydroxyurea therapy, with no indication of recovery until after 12 to 18 months of drug administration (P <.05). Similar changes were noted for total magnesium concentrations. Mean serum levels of K(+), Na(+), and Ca(2+) remained consistently within normal ranges. CONCLUSIONS: These findings warrant a controlled study of the effects of magnesium supplementation in patients with SCA receiving hydroxyurea. Potentially, such therapy could alleviate or prevent vaso-occlusive crises.     

The pediatric hydroxyurea phase III clinical trial (BABY HUG): Challenges of study design

Evidence of the laboratory benefits of hydroxyurea and its clinical efficacy in reducing acute vaso‐occlusive events in adults and children with sickle cell anemia has accumulated for more than 15 years. A definitive clinical trial showing that hydroxyurea can also prevent organ damage might support widespread use of the drug at an early age. BABY HUG is a randomized, double‐blind placebo‐controlled trial to test whether treating young children ages 9–17 months at entry with a liquid preparation of hydroxyurea (20 mg/kg/day for 2 years) can decrease organ damage in the kidneys and spleen by at least 50%. Creation of BABY HUG entailed unique challenges and opportunities. Although protection of brain function might be considered a more compelling endpoint, preservation of spleen and renal function has clinical relevance, and significant treatment effects might be discernable within the mandated sample size of 200. Concerns about unanticipated severe toxicity and burdensome testing and monitoring requirements were addressed in part by an internal Feasibility and Safety Pilot Study, the successful completion of which was required prior to enrolling a larger number of children on the protocol. Concerns over recruitment of potentially vulnerable subjects were allayed by inclusion of a research subject advocate, or ombudsman. Finally, maintenance of blinding of research personnel was aided by inclusion of an unblinded primary endpoint person, charged with transmitting endpoint data and monitoring blood work locally for toxicity (ClinicalTrials.gov number, NCT00006400). Pediatr Blood Cancer 2010;54:250–255. © 2009 Wiley‐Liss, Inc.     

Effect of hydroxyurea in sickle cell anemia: a clinical trial in children and teenagers with severe sickle cell anemia and sickle cell beta-thalassemia.

This study evaluated the efficacy of hydroxyurea treatment in the prevention of vaso-occlusive crises among children and teenagers with severe sickle cell anemia and sickle cell beta-thalassemia. Nineteen children and young adults with severe sickle cell disease were enrolled to the hydroxyurea treatment trial. The incidence of vaso-occlusive crises, acute chest syndrome, hemolytic crises, splenic sequestration episodes, blood transfusions, and hospital days in the 2 years before hydroxyurea (HU) treatment were compared with the same parameters in the first 2 years of treatment. The patients received a mean dose of 21.3 mg/kg/day daily and were treated during a mean period of 40.3 +/- 14 months (range 20 to 68 months). Significant increases were observed after 1 month in the Hgb, MCV, MCH, and MCHC levels and were more notable after 3 months. The increase in the Hgb F level became important after 3 months of HU therapy and was highly significant (p < .001) beyond 6 months. No differences were observed in the RDW, reticulocyte count, Hgb S, and Hgb A2. Severe neutropenia was observed in one case. A decrease in the frequency of vaso-occlusive crises, acute chest syndrome, hemolytic crises, blood transfusions, and days spent in the hospital was demonstrated during the HU treatment period compared to the same period before. The clinical and laboratory response to HU was dramatic in severely affected sickle cell anemia (SCA) patients. The response to HU in children and teenagers with severe sickle cell anemia is similar to the response in adults, and no severe adverse effects were observed.     

Efficacy of fixed low dose hydroxyurea in Indian children with sickle cell anemia: A single centre experience

Introduction

Data on the efficacy of hydroxyurea (HU) in Indian children with sickle cell anaemia (SCA) is limited. Hence, we have evaluated the efficacy of fixed low dose HU in Indian children.

Methods

The study cohort consisted of 144 children (<18 years of age) with SCA having severe manifestations (≥3 episodes of vasocclusive crisis or blood transfusions, or having ≥1 episode of acute chest syndrome or cerebrovascular stroke or sequestration crisis) who were started on fixed low dose HU (10 mg/kg/day). They were followed up for two years and monitored for the hematological and clinical efficacy and safety.

Results

There was significant increase in the fetal hemoglobin level (HbF%), total hemoglobin and mean corpuscular volume. Vasoocclusive crises, blood transfusions, acute chest syndrome, sequestration crises and hospitalizations decreased significantly. Baseline HbF% had significant positive correlation with HbF% at 24 months. There was significant negative correlation between baseline HbF% and change in HbF% from baseline to 24 months. No significant correlation was found between HbF% at baseline and clinical event rates per year after HU. No major adverse events occurred during the study period.

Conclusion

Fixed low dose HU is effective and safe in Indian children with SCA.     

Enalapril and hydroxyurea therapy for children with sickle nephropathy

Proteinuria in children with sickle cell anemia (SCA) is an early sign of sickle nephropathy, and portends the development of nephrotic syndrome and chronic renal failure. Enalapril has been shown to reduce proteinuria in adult patients with SCA, but the potential benefits of hydroxyurea in this clinical setting have not been reported. A single institution retrospective analysis was performed. Children with sickle nephropathy were identified, and the laboratory effects of enalapril and hydroxyurea therapy were evaluated in children with substantial proteinuria. Three children developed proteinuria at 8 +/- 1 years of age. Pre-treatment laboratory studies included a low serum albumin (2.8 +/- 0.8 g/dl) and a highly elevated urine protein/creatinine ratio (6.9 +/- 3.7, normal <0.2). Enalapril treatment for 3.0 +/- 1.3 years normalized serum albumin (3.9 +/- 0.3 g/dl) without significant changes in serum potassium, serum creatinine, or systolic blood pressure. However, urine protein/creatinine remained elevated in the nephrotic range (1.6 +/- 0.7). The addition of hydroxyurea therapy for 3.5 +/- 1.2 years increased fetal hemoglobin levels (7.0 +/- 3.6% to 21.0 +/- 3.2%) and was associated with a near-normal urine protein/creatinine ratio (0.5 +/- 0.1). Enalapril therapy for children with sickle nephropathy reduces urinary protein excretion and normalizes serum albumin. Hydroxyurea therapy may further normalize the urine protein/creatinine ratio. Combination therapy should be tested prospectively in children with sickle nephropathy.     

Prevention of secondary stroke and resolution of transfusional iron overload in children with sickle cell anemia using hydroxyurea and phlebotomy

OBJECTIVE: Transfusions prevent secondary stroke in children with sickle cell anemia (SCA) but also cause iron overload. Alternatives for stroke prophylaxis with effective therapy to reduce iron burden are needed. STUDY DESIGN: For 35 children with SCA and stroke, transfusions were prospectively discontinued. Hydroxyurea was prescribed for stroke prophylaxis, and phlebotomy removed excess iron. Initial patients discontinued transfusions before hydroxyurea therapy, but later patients overlapped transfusions with hydroxyurea until tolerating full-dose therapy. RESULTS: Children received hydroxyurea for 42 +/- 30 months (range, 3-104 months). Hydroxyurea (26.7 +/- 4.8 mg/kg per day) led to mild neutropenia (3.9 +/- 2.3 x 10(9)/L) with significant increases in hemoglobin concentration, mean corpuscular volume, and fetal hemoglobin. Stroke recurrence rate was 5.7 events per 100 patient-years, but children receiving overlapping hydroxyurea therapy had only 3.6 events per 100 patient-years. For 26 children with >6 months of phlebotomy, 14,311 +/- 12,459 mL blood (315 +/- 214 mL/kg) was removed, with serum ferritin decreasing from a median of 2722 to 298 ng/mL. Among patients completing phlebotomy, liver biopsy documented normal histology and no excess iron deposition. CONCLUSIONS: For children with SCA and stroke, hydroxyurea effectively prevents secondary stroke and serial phlebotomy leads to complete resolution of transfusional iron overload.     

Intergenerational breastfeeding practices among parents and children: 1993 Pelotas (Brazil) birth cohort

The objective of this study was to investigate intergenerational breastfeeding practices according to parental sex and age at delivery in the 1993 Pelotas (Brazil) birth cohort study. This is a prospective birth cohort study, and at the 22‐year follow‐up, a substudy with all children of the cohort members who had become parents was conducted (93Cohort‐II). First generation breastfeeding data were collected at 3 months and 4‐year‐old follow‐ups. In the 93Cohort‐II, parents answered a questionnaire about their children's breastfeeding practices. Adjusted Tobit and Poisson regression models with robust variance were applied to estimate the association between predominant parental breastfeeding duration and exclusive breastfeeding duration of the children at 3 and 6 months. Out of 3,810 cohort participants, 955 (25%) had delivered at least one live‐born infant, and 1,222 children were assessed. Fifty‐four percent of parents were ≤19 years old. Direct effects of predominant parental breastfeeding duration on exclusive breastfeeding duration of their children were only observed when data were stratified by parental age: children born to parents aged ≥20 years old and who were predominantly breastfed for at least 3 months presented higher exclusive breastfeeding duration and higher prevalence of being exclusively breastfed for at least 3 months. When analyses were stratified by mothers and fathers, the result remained significant only among mothers. Longer predominant breastfeeding duration in the first generation was associated with longer exclusive breastfeeding duration in the second generation, but only among older mothers. Education and social support surrounding breastfeeding should be intensified among fathers and younger parents to create a positive environment supportive of breastfeeding.     

A two-year pilot trial of hydroxyurea in very young children with sickle-cell anemia.

OBJECTIVE: Hydroxyurea improves hematologic values and decreases vaso-occlusive complications in adults and children with sickle cell anemia (SCA), but has not been tested in infants before the onset of chronic organ dysfunction. We conducted a collaborative pilot trial of hydroxyurea in infants with SCA to assess its (1) feasibility of administration, (2) toxicity, (3) hematologic effects, and (4) effect on spleen function. STUDY DESIGN: Patients with hemoglobin (Hb) SS or Sbeta(0) thalassemia (n = 28, median age 15 months) received hydroxyurea for 2 years at 20 mg/kg/day. Hydroxyurea was temporarily discontinued for predefined toxicity. RESULTS: Seven patients exited the study early: five for noncompliance or refusal to continue, one for mild stroke, and one for fatal splenic sequestration. The predominant toxicity was transient neutropenia, which was usually associated with a viral-like illness. After 2 years of treatment, mean Hb level = 8.8 g/dL and Hb F = 20.3%, both higher than predicted age-specific levels. Radionuclide splenic uptake was absent in 47% of patients at study completion, compared with predicted functional asplenia in 80% of the patients. CONCLUSIONS: Hydroxyurea therapy for infants with SCA is feasible and well tolerated, has hematologic efficacy, and may delay functional asplenia. The potential for hydroxyurea to preserve organ function in SCA should be further evaluated.     

Lack of mortality in 22 children with sickle cell anemia and severe malarial anemia

Retrospective studies suggest that there is high mortality in children with sickle cell anemia (SCA) and severe malaria. We assessed mortality in Ugandan children with severe malarial anemia (SMA, n = 232) or cerebral malaria (CM, n = 267) by sickle cell hemoglobin genotype. Admission and 2‐year follow‐up mortality did not differ among children with SMA who had homozygous form of sickle cell hemoglobin (HbSS) versus normal form of adult hemoglobin (admission, 0/22, 0%, vs. 1/208, 0.5%; follow‐up, 1/22, 4.5%; 7/207, 3.4%, respectively; all P > 0.6). The single child with CM and HbSS survived. The study findings highlight the need for large prospective studies of malaria‐related mortality in children with SCA.     

Subclinical parvovirus B19 infection in children with sickle cell anemia

PURPOSE: To investigate the prevalence and clinical consequences of previous parvovirus B19 exposure in a large cohort of pediatric patients with sickle cell anemia (SCA). METHODS: Prospective serologic testing for previous parvovirus B19 exposure was performed in steady-state pediatric patients with SCA, either prior to starting hydroxyurea therapy or in preparation for transition to the adult service. A retrospective chart review was performed to ascertain whether patients had a documented history of a transient aplastic crisis. RESULTS: The prevalence of serologic evidence of previous parvovirus infection increased with age. The overall prevalence in 102 children with SCA was 53%, ranging from 44% between 5 and 9 years of age to 71% between 17 and 21 years of age. Only 27% of patients had a previous clinically recognized transient aplastic crisis. CONCLUSIONS: By the teenage years, most pediatric patients with SCA have serologic evidence of previous parvovirus B19 exposure. However, subclinical parvovirus infection appears to be common in children with SCA, since most patients have no documented previous transient aplastic crisis.     

Nocturnal haemoglobin oxygen saturation variability is associated with vitamin C deficiency in Tanzanian children with sickle cell anaemia

Aim: To compare pulse oximetry in children with sickle cell anaemia (SCA) and controls and test the hypothesis that vitamin C deficiency (VCD; <11.4 μmol/L) is associated with nocturnal haemoglobin oxygen desaturation in SCA. Methods: We undertook nocturnal and daytime pulse oximetry in 23 children with SCA (median age 8 years) with known steady‐state plasma vitamin C concentrations and 18 siblings (median 7 years). Results: Median nocturnal delta 12 s index (delta12 s), a measure of haemoglobin oxygen saturation (SpO₂) variability, was 0.38 (interquartile range 0.28–0.51) in SCA and 0.35 (0.23–0.48) in controls, with 9/23 and 6/18, respectively, having a delta12 s >0.4, compatible with obstructive sleep apnoea (OSA). Eleven of twenty‐three with SCA had VCD; logged vitamin C concentrations showed a 66% decrease per 0.1 unit increase in delta12 s ([95% CI ?86%, ?15%]; p = 0.023) and delta12 s >0.4 was associated with VCD (odds ratio 8.75 [1.24–61.7], p = 0.029). Daytime and mean nocturnal SpO₂ were lower in SCA but there was no association with vitamin C. Conclusion: Obstructive sleep apnoea (OSA), detected from nocturnal haemoglobin oxygen saturation variability, is common in Tanzanian children and associated with vitamin C Deficiency in SCA. The direction of causality could be determined by comparing OSA treatment with vitamin C supplementation.