Hydroxyurea for sickle cell anemia: what have we learned and what questions still remain?

Vaso-occlusive crisis in sickle cell disease: current paradigm on pain management

This narrative review aims to highlight the current paradigm on pain management in sickle cell vaso-occlusive crisis. It specifically examines the pathophysiologic mechanisms of sickle cell pain as well as the pharmacologic and nonpharmacologic methods of pain management. Recurrent painful episodes constitute the major morbidity in sickle cell disease (SCD). While adolescents and young adults experience mostly acute episodic nociceptive pain, it is now recognized that a significant number of adult patients develop chronic neuropathic and centralized pain. In fact, current evidence points to an age-dependent increase in the frequency of SCD patients with chronic pain. Management of disease-related pain should be based on its pathophysiologic mechanisms instead of using recommendations from other non-SCD pain syndromes. Pain management in vaso-occlusive crisis is complex and requires multiple interventions such as pharmacologic, nonpharmacologic, and preventive therapeutic interventions. Pharmacologic treatment involves the use of non-opioid and opioid analgesics, and adjuvants - either singly or in combination - depending on the severity of pain. The basic approach is to treat SCD pain symptomatically with escalating doses of non-opioid and opioid analgesics. Given the moderate-to-severe nature of the pain usually experienced in this form of SCD crisis, opioids form the bedrock of pharmacologic treatment. Multimodal analgesia and structured, individualized analgesic regimen appear more effective in achieving better treatment outcomes. Although the current evidence is still limited on the supportive role of cognitive behavioral therapy in pain management, this nonpharmacologic approach is reportedly effective, but needs further exploration as a possible adjunct in analgesia.

Low-dose hydroxycarbamide therapy may offer similar benefit as maximum tolerated dose for children and young adults with sickle cell disease in low-middle-income settings

The multiple clinical benefits of hydroxycarbamide in sickle cell disease are supported by a large body of evidence. The maximum tolerated dose (MTD) is the regimen recommended by guidelines from a panel of National Heart, Lung, and Blood Institute (NHLBI) experts, but other dosage regimens have been used in babies (BABY-HUG) 9 to 18 months old (20 mg/kg per day) and developing countries such as India (10 mg/kg per day); however, there has been no direct comparison of the efficacy, effectiveness, or cost-effectiveness of these different regimens. The purpose of this review was to investigate the current situation with various hydroxycarbamide regimens with particular relevance to low-middle-income countries. In regard to methodology, a literature review was undertaken by using multiple databases in PubMed and Google and the search terms included sickle cell disease, hydroxyurea, hydroxycarbamide, sickle cell anaemia, low-middle-income countries, Sub-Saharan Africa, and India. Although MTD regimens have been widely used in research, especially within North America, clinical trials elsewhere tend to use fixed-dose regimens. In a survey of haematologists across Europe and Africa, 60% (75% response rate) did not use the MTD regimen for hydroxycarbamide treatment of sickle cell disease. The recommendations are (1) for practical purposes to commence using fixed-dose hydroxycarbamide in line with BABY-HUG recommendations and then (2) to consider or propose a trial comparing MTD escalation with various fixed doses and to include as end points health-related quality of life, haemoglobin F levels, adherence, and cost-effectiveness.

Hematopoietic stem cell transplantation for sickle cell disease: Progress and challenges

Sickle cell disease (SCD) presents challenges to hematopoietic stem cell transplantation (HSCT), including donor availability and morbidity with age/disease severity. However, severe SCD causes irreversible organ damage that HSCT can mitigate. This benefit must be balanced against preparative regimen toxicity, graft-versus-host disease, and mortality risk. We review efforts to balance HSCT complications with the promise of cure, and knowledge gaps that warrant further investigation. We highlight the burden of SCD, HSCT risks and benefits, and SCD families' approach to this balance. We emphasize the necessity for information exchange to ensure a joint decision-making process between providers and patients.

Perspective: A Novel Prognostic for Sickle Cell Disease

Sickle hemoglobin (α₂β^S ₂) polymerization drives disease pathophysiology in sickle cell anemia. Fetal hemoglobin (α₂γ₂) restricts disease severity by inhibiting the polymerization of sickle hemoglobin in a concentration-dependent manner. Clinical decision-making relies on diagnostic technologies evaluating fetal hemoglobin as mean percent or mean quantity in blood. Limitation of this approach is exemplified by patients with significant high fetal hemoglobin levels and severe disease, suggesting that fetal hemoglobin is unevenly distributed across F-cells. Therefore, determination of fetal hemoglobin/F-cell would provide a new paradigm for ascertaining prognosis and response to fetal hemoglobin-inducing agents. Measurement of fetal hemoglobin/F-cell, ultimately adapted to widespread standardized analytical use, is a promising fetal hemoglobin-related prognostic approach to monitor the severity of sickle cell disease and the best "phenotype" to follow when developing new candidate fetal hemoglobin inducers or titrating hydroxyurea in treated sickle cell patients.

Discovery of phenylsulfonylfuroxan derivatives as gamma globin inducers by histone acetylation

N-oxide derivatives 5(a-b), 8(a-b), and 11(a-c) were designed, synthesized and evaluated in vitro and in vivo as potential drugs that are able to ameliorate sickle cell disease (SCD) symptoms. All of the compounds demonstrated the capacity to releasing nitric oxide at different levels ranging from 0.8 to 30.1%, in vivo analgesic activity and ability to reduce TNF-α levels in the supernatants of monocyte cultures. The most active compound (8b) protected 50.1% against acetic acid-induced abdominal constrictions, while dipyrone, which was used as a control only protected 35%. Compounds 8a and 8b inhibited ADP-induced platelet aggregation by 84% and 76.1%, respectively. Both compounds increased γ-globin in K562 cells at 100 μM. The mechanisms involved in the γ-globin increase are related to the acetylation of histones H3 and H4 that is induced by these compounds. In vitro, the most promising compound (8b) was not cytotoxic, mutagenic and genotoxic.

Hydroxycarbamide adherence and cumulative dose associated with hospital readmission in sickle cell disease: a 6-year population-based cohort study

Sickle cell disease (SCD) is a congenital haemoglobinopathy that causes frequent acute care/emergency room visits and hospital admissions for affected individuals. Evidence from population-based studies demonstrating the role of hydroxycarbamide (HC, also termed hydroxyurea) in reducing hospital readmission rates is limited. Our objective was to describe the use of HC and its association with acute care utilization and readmission rates using a large, nationally-representative US health insurance claims database over a 6-year period between 2009 and 2014. We identified 20 721 SCD-related inpatient and acute care encounters. Patients had been exposed to HC within 6 months prior to admission in 4263 (21%) of SCD-related admission events. HC use was more common among children aged 10-17 years and young adults aged 18-29 years. HC was associated with lower 30-day all-cause readmission rates in adults treated with average daily doses ≥1 g (odds ratio [OR], 0·72, 95% confidence interval [CI] 0·52-0·99) and doses of 0·5-1 g (OR, 0·73, 95% CI 0·57-0·93), compared to HC treatment with average daily doses of <0·5 g; adherence to HC with proportion of days covered of ≥0·80 was also associated with significantly lower 30-day all-cause readmission risks (OR, 0·59, 95% CI 0·41-0·84). Optimal therapeutic dosing and adherence to HC treatment significantly reduces 30-day readmissions among patients with SCD.

Advances in new drug therapies for the management of sickle cell disease

Introduction

Sickle cell disease (SCD) is an orphan disease in the United States, but is highly prevalent worldwide. Only two drugs, hydroxyurea and L-glutamine, are approved for this disease. With an improved understanding of the pathophysiology of SCD as well as the success of several recently approved drugs for other orphan diseases, there is an increased interest in the development of drugs for SCD.

Areas covered

This review summarizes published studies of drug therapies and ongoing trials of novel agents.

Expert opinion

The development of drugs with different mechanisms of action offers opportunities for combination and individualized therapy in SCD. In addition to acute pain crisis, the evaluation of other SCD-related complications, exercise capacity, patient reported outcomes and validated surrogate endpoints are necessary to advance drug development. It is important to involve sites in sub-Saharan Africa and India, which have the highest burden of SCD, in trials of novel therapies.

Phytomedicines (medicines derived from plants) for sickle cell disease

BACKGROUND

Sickle cell disease, a common recessively inherited haemoglobin disorder, affects people from sub-Saharan Africa, the Middle East, Mediterranean basin, Indian subcontinent, Caribbean and South America. It is associated with complications and a reduced life expectancy. Phytomedicines (medicine derived from plants in their original state) encompass many of the plant remedies from traditional healers which the populations most affected would encounter. Laboratory research and limited clinical trials have suggested positive effects of phytomedicines both in vivo and in vitro. However, there has been little systematic appraisal of their benefits. This is an update of a Cochrane Review first published in 2004, and updated in 2010, 2013, and 2015.

OBJECTIVES

To assess the benefits and risks of phytomedicines in people with sickle cell disease of all types, of any age, in any setting.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Haemoglobinopathies Trials Register, the International Standard Randomised Controlled Trial Number Register (ISRCTN), the Allied and Complimentary Medicine Database (AMED), ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP).Dates of most recent searches: Cochrane Cystic Fibrosis and Genetic Disorders Haemoglobinopathies Trials Register: 10 April 2017; ISRCTN: 26 July 2017; AMED: 24 August 2017; ClinicalTrials.gov: 02 August 2017; and the WHO ICTRP: 27 July 2017.

SELECTION CRITERIA

Randomised or quasi-randomised trials with participants of all ages with sickle cell disease, in all settings, comparing the administration of phytomedicines, by any mode to placebo or conventional treatment, including blood transfusion and hydroxyurea.

DATA COLLECTION AND ANALYSIS

Both authors independently assessed trial quality and extracted data.

MAIN RESULTS

Two trials (182 participants) and two phytomedicines Niprisan® (also known as Nicosan®) and Ciklavit® were included. The Phase IIB (pivotal) trial suggests that Niprisan® was effective in reducing episodes of severe painful sickle cell disease crisis over a six-month period (low-quality evidence). It did not affect the risk of severe complications or the level of anaemia (low-quality evidence). No serious adverse effects were reported. The single trial of Cajanus cajan (Ciklavit®) reported a possible benefit to individuals with painful crises (low-quality evidence), and a possible adverse effect (non-significant) on the level of anaemia (low-quality evidence).

AUTHORS' CONCLUSIONS

While Niprisan® appeared to be safe and effective in reducing severe painful crises over a six-month follow-up period, further trials are required to assess its role in the management of people with sickle cell disease and the results of its multicentre trials are awaited. Currently no conclusions can be made regarding the efficacy of Ciklavit®. Based on the published results for Niprisan® and in view of the limitations in data collection and analysis of both trials, phytomedicines may have a potential beneficial effect in reducing painful crises in sickle cell disease. This needs to be further validated in future trials. More trials are required on the safety and efficacy of phytomedicines used in managing sickle cell disease.

Interventions for treating neuropathic pain in people with sickle cell disease

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To determine the effectiveness and safety of any pharmacological or non‐pharmacological therapies for treating neuropathic pain in people with SCD.

Pharmacological and molecular approaches for the treatment of β-hemoglobin disorders

β-hemoglobin disorders, such as β-thalassemia and sickle cell anemia are among the most prevalent inherited genetic disorders worldwide. These disorders are caused by mutations in the gene encoding hemoglobin-β (HBB), a vital protein found in red blood cells (RBCs) that carries oxygen from lungs to all parts of the human body. As a consequence, there has been an enduring interest in this field in formulating therapeutic strategies for the treatment of these diseases. Currently, there is no cure available for hemoglobin disorders, although, some patients have been treated with bone marrow transplantation, whose scope is limited because of the difficulty in finding a histocompatible donor and also due to transplant-associated clinical complications that can arise during the treatment. On account of these constraints, reactivation of fetal hemoglobin (HbF) synthesis holds immense promise and is a viable strategy to alleviate the symptoms of β-hemoglobin disorders. Development of new genomic tools has led to the identification of important natural genetic modifiers of hemoglobin switching which include BCL11A, KLF1, HBSIL-MYB, LRF, LSD1, LDB1, histone deacetylases 1 and 2 (HDAC1 and HDAC2). miRNAs are also promising therapeutic targets for development of more effective strategies for the induction of HbF production. Many new small molecule pharmacological inducers of HbF production are already under pre-clinical and clinical development. Furthermore, recent advancements in gene and cell therapy includes targeted genome editing and iPS cell technologies, both of which utilizes a patient's own cells, are emerging as extremely promising approaches for significantly reducing the burden of β-hemoglobin disorders.

Coagulation profile of Sudanese children with homozygous sickle cell disease and the effect of treatment with omega-3 fatty acid on the coagulation parameters

Background

It has been reported that patients with SCD do have an abnormal coagulation profile. Coagulopathy is thought to be one of the key factors that contribute to the vaso-occlusive crisis that characterises sickle cell disease (SCD). In this study, we investigated whether Sudanese sickle cell patients have an abnormal coagulation profile. In addition, the effect of treatment with either omega-3 fatty acids or hydroxyurea on coagulation profile was assessed.

Methods

Homozygous SCD patients untreated (n = 52), omega-3 treated (n = 44), hydroxyurea (HU) treated (n = 8) and healthy (HbAA) controls (n = 52) matched for age (4–20 years), gender and socioeconomic status were enrolled. Patients on omega-3 fatty acids, according to age, received one to four capsules containing 277.8 mg DHA and 39.0 mg eicosapentnoic. Patients on Hydroxyurea were in on dosage more than 20 mg/kg/day. The steady state levels of the coagulation parameters and the effect of the treatments with either HU or omega-3 fatty acids on markers of coagulation were investigated.

Results

Compared to the healthy controls, treated and untreated HbSS patients had lower hemoglobin, plasma Protein C, proteins S and higher white blood cell count (WBC), platelets count (PLTs) and plasma D-dimer levels,(p < 0.05). In comparison to untreated HbSS, treatment with neither omega-3 nor HU had effect on the WBC, plasma proteins C and S, (p > 0.05). HU treated group had a lower PLTs count compared to HbSS untreated group (p < 0.5). The prothrombin and activated partial thromboplastin times and international normalized ratio (INR) of untreated patients are significantly higher than n-3 treated, HU-treated patients and health controls, (p < 0.05). Patients treated with omega-3 had lowered D-dimer levels in comparison to HU-treated and untreated HbSS patients, (p < 0.001).

Conclusion

This study provides evidence that Sudanes patients have abnormal coagulation profile and treatment with either HU or omega-3 fatty acids might partially ameliorate SCD-associated chronic coagulopathic state.

Hydroxyurea differentially modulates activator and repressors of γ-globin gene in erythroblasts of responsive and non-responsive patients with sickle cell disease in correlation with Index of Hydroxyurea Responsiveness

Hydroxyurea (HU), the first of two drugs approved by the US Food and Drug Administration for treating patients with sickle cell disease (SCD), produces anti-sickling effect by re-activating fetal γ-globin gene to enhance production of fetal hemoglobin. However, approximately 30% of the patients do not respond to HU therapy. The molecular basis of non-responsiveness to HU is not clearly understood. To address this question, we examined HU-induced changes in the RNA and protein levels of transcription factors NF-Y, GATA-1, -2, BCL11A, TR4, MYB and NF-E4 that assemble the γ-globin promoter complex and regulate transcription of γ-globin gene. In erythroblasts cultured from peripheral blood CD34⁺ cells of patients with SCD, we found that HU-induced changes in the protein but not the RNA levels of activator GATA-2 and repressors GATA-1, BCL11A and TR4 correlated with HU-induced changes in fetal hemoglobin (HbF) levels in the peripheral blood of HU high and low responders. However, HU did not significantly induce changes in the protein or RNA levels of activators NF-Y and NF-E4. Based on HU-induced changes in the protein levels of GATA-2, -1 and BCL11A, we calculated an Index of Hydroxyurea Responsiveness (IndexHU-3). Compared to the HU-induced fold changes in the individual transcription factor protein levels, the numerical values of IndexHU-3 statistically correlated best with the HU-induced peripheral blood HbF levels of the patients. Thus, IndexHU-3 can serve as an appropriate indicator for inherent HU responsiveness of patients with SCD.

Key Pharmacogenomic Considerations for Sickle Cell Disease Patients

Sickle cell disease (SCD), although a monogenic disease, exhibits a complex clinical phenotype that hampers optimum patient stratification and disease management, especially on hydroxyurea treatment. Moreover, theranostics, the combination of diagnostics to individualize and optimize therapeutic interventions, has not been firmly on the forefront of SCD research and clinical management to date. We suggest that if tailor-made theranostics in SCD is envisaged, pharmacogenomics is anticipated to be the way forward. Herein, we present the current key pharmacogenomic opportunities and challenges in SCD, considering population variation, ethics, and socioeconomic aspects. We focus on pharmacogenomics and pain management, genethics, and cost-effectiveness in SCD. We searched for and synthesized data from PubMed and Google Scholar, and the references from relevant articles, using the keywords "pharmacogenomics," "sickle cell disease," "hydroxyurea," "ethics," "pain management," "morphine metabolism," "opioids," "pharmacogenomics and chronic pain," "cost-effectiveness," and "economic evaluation." Only articles published in English were included. So far, when pharmacogenomics in SCD has been considered, interindividual variability in hydroxyurea response/toxicity has been of primary interest. We underscore the need to extend pharmacogenomic considerations on other therapeutic interventions currently present using a holistic patient-centric approach, and taking disease complications into account as well. Furthermore, we raise awareness toward socioeconomic, ethical, and population differences in the way sickle cell pharmacogenomics might unfold in the future. If pharmacogenomics in SCD is to be used in the clinic in an evidence-based manner, cost-effectiveness and population-specific empirical ethics data are urgently needed.

Perioperative considerations for patients with sickle cell disease: a narrative review

PURPOSE

Approximately 200,000 individuals worldwide are born annually with sickle cell disease (SCD). Regions with the highest rates of SCD include Africa, the Mediterranean, and Asia, where its prevalence is estimated to be 2-6% of the population. An estimated 70,000-100,000 people in the United States have SCD. Due to enhanced newborn screening, a better understanding of this disease, and more aggressive therapy, many sickle cell patients survive into their adult years and present more frequently for surgery.

SOURCE

The authors identified relevant medical literature by searching PubMed, MEDLINE®, EMBASE™, Scopus™, Web of Science, and Google Scholar databases for English language publications appearing from 1972-September 2016. Case reports, abstracts, review articles, and original research articles were reviewed-with particular focus on the pathophysiology and medical management of SCD and any anesthesia-related issues.

PRINCIPAL FINDINGS

Perioperative physicians should be familiar with the triggers of a sickle cell crisis and vaso-occlusive disease. Sickle cell disease affects various organ systems, including the central nervous, cardiovascular, pulmonary, genitourinary, and musculoskeletal systems. Preoperative assessment should focus on end-organ dysfunction. Controversy continues regarding if and when sickle cell patients should receive transfusions and which anesthetic technique (regional or general) confers any benefits. Timely, appropriate, and sufficient analgesia is critical, especially when patients experience a vaso-occlusive crisis, acute chest syndrome, or acute postoperative pain.

CONCLUSION

Effective management of SCD patients in the perioperative setting requires familiarity with the epidemiology, pathophysiology, clinical manifestations, and treatment of SCD.

Klf10 Gene, a Secondary Modifier and a Pharmacogenomic Biomarker of Hydroxyurea Treatment Among Patients With Hemoglobinopathies

BACKGROUND

The klf10 gene could indirectly modify γ-globin chain production and hence the level of fetal hemoglobin (HbF) ameliorating the phenotype of β-hemoglobinopathies and the response to hydroxycarbamide (hydroxyurea [HU]) therapy. In this study, we aimed to evaluate the frequency of different genotypes for the klf10 gene in β-thalassemia major (B-TM), β-thalassemia intermedia (B-TI), and sickle cell disease (SCD) patients by polymerase chain reaction and to assess its relation to disease phenotypes and HU response.

METHODS

This cross-sectional study included 75 patients: 50 B-TM, 12 SCD, and 13 B-TI patients (on stable HU dose). The relation of the klf10 gene polymorphism (TIEG, TIEG1, EGRα) (rs3191333: c*0.141C>T) to phenotype was studied through baseline mean corpuscular volume, HbF, and transfusion history, whereas evaluation of response to HU therapy was carried out clinically and laboratory.

RESULTS

The frequency of the mutant klf10 genotype (TT) and that of the mutant allele (T) was significantly higher among B-TM patients compared with those with B-TI and SCD patients. Only homozygous SCD patients for the wild-type allele within the klf10 gene had a significantly lower transfusion frequency. The percentage of HU responders and nonresponders between different klf10 polymorphic genotypes among B-TI or SCD patients was comparable.

CONCLUSIONS

Although the klf10 gene does not play a standalone role as an HbF modifier, our data support its importance in ameliorating phenotype among β-hemoglobinopathies.

Hydroxyurea therapy in adult Nigerian sickle cell disease: a monocentric survey on pattern of use, clinical effects and patient's compliance

BACKGROUND

The clinical prospects of hydroxyurea therapy in the management of sickle cell disease (SCD) require evaluation in the Nigerian setting to develop indigenous guidelines. This survey examines the pattern of hydroxyurea therapy, its clinico-haematologic benefits and safety profile in Nigerian SCD subjects.

METHODS

A cross sectional pilot survey was carried out among 60 adult SCD subjects over 3 months. Data on clinical phenotypes, relevant haematological parameters and details of hydroxyurea therapy were obtained using a structured questionnaire through an interview process and case file review.

RESULTS

The median age was 30 years. Thirty-four (56.7%) of the subjects are aware of hydroxyurea therapy in SCD. Twenty-four (40%) SCD patients had previously used hydroxyurea. Only 4 subjects were fully compliant. Reasons for non-compliance included poor knowledge and lack of funds. In particular, hydroxyurea reduced leucocyte count and increased mean red cell volume (MCV) in compliant subjects.

CONCLUSION

Hydroxyurea use is low among Nigerian SCD subjects despite its proven efficacy/clinical prospects in the developed nations. Large scale multicenter studies and clinical trials are needed to form a basis for developing standard local treatment protocol for its use.

Risk factors for mortality in adult patients with sickle cell disease: a meta-analysis of studies in North America and Europe

Although recent studies show an improved survival of children with sickle cell disease in the US and Europe, for adult patients mortality remains high. This study was conducted to evaluate the factors associated with mortality in adult patients following the approval of hydroxyurea. We first evaluated the association between selected variables and mortality at an academic center (University of North Carolina). Data sources were then searched for publications from 1998 to June 2016, with meta-analysis of eligible studies conducted in North America and Europe to evaluate the associations of selected variables with mortality in adult patients. Nine studies, combined with the UNC cohort (total n=3257 patients) met the eligibility criteria. Mortality was significantly associated with age (per 10-year increase in age) [7 studies, 2306 participants; hazard ratio (HR): 1.28; 95% confidence interval (CI): 1.10-1.50], tricuspid regurgitant jet velocity 2.5 m/s or more (5 studies, 1577 participants; HR: 3.03; 95%CI: 2.0-4.60), reticulocyte count (3 studies, 1050 participants; HR: 1.05; 95%CI: 1.01-1.10), log(N-terminal-pro-brain natriuretic peptide) (3 studies, 800 participants; HR: 1.68; 95%CI: 1.48-1.90), and fetal hemoglobin (7 studies, 2477 participants; HR: 0.97; 95%CI: 0.94-1.0). This study identifies variables associated with mortality in adult patients with sickle cell disease in the hydroxyurea era.

Emerging point-of-care technologies for sickle cell disease screening and monitoring

INTRODUCTION

Sickle Cell Disease (SCD) affects 100,000 Americans and more than 14 million people globally, mostly in economically disadvantaged populations, and requires early diagnosis after birth and constant monitoring throughout the life-span of the patient. Areas covered: Early diagnosis of SCD still remains a challenge in preventing childhood mortality in the developing world due to requirements of skilled personnel and high-cost of currently available modalities. On the other hand, SCD monitoring presents insurmountable challenges due to heterogeneities among patient populations, as well as in the same individual longitudinally. Here, we describe emerging point-of-care micro/nano platform technologies for SCD screening and monitoring, and critically discuss current state of the art, potential challenges associated with these technologies, and future directions. Expert commentary: Recently developed microtechnologies offer simple, rapid, and affordable screening of SCD and have the potential to facilitate universal screening in resource-limited settings and developing countries. On the other hand, monitoring of SCD is more complicated compared to diagnosis and requires comprehensive validation of efficacy. Early use of novel microdevices for patient monitoring might come in especially handy in new clinical trial designs of emerging therapies.

Decreased fetal hemoglobin over time among youth with sickle cell disease on hydroxyurea is associated with higher urgent hospital use

BACKGROUND

Hydroxyurea (HU) induces dose-dependent increased fetal hemoglobin (HbF) for sickle cell disease (SCD). Large deviation from historical personal best (PBest) HbF, a clinic-based version of maximum dose, may identify a subset with suboptimal HU adherence over time.

PROCEDURE

Retrospective clinical data from youth ages 10-18 years prescribed HU at two centers were extracted from medical records at three time points: pre-HU initiation, PBest and a recent assessment. Decrease from PBest HbF of 20% or more at recent assessment despite stable dosing was designated as high deviation from PBest. Acute hospital use was compared between 1-year periods, pre-HU and ±6 months for PBest and recent assessment. Groups were compared using descriptive and bivariate nonparametric statistics.

RESULTS

Seventy-five youth, mean HU duration 5.9 years, met eligibility criteria. Mean ages of HU initiation, PBest and recent assessment were 8.0, 10.9 and 13.9 years, respectively. Despite stable dosing, average HbF of 19.5% at PBest overall declined by 31.8% at recent assessment. PBest HbF declined by 11.7 and 40.1% in two groups, the latter comprised 70.7% of the sample, had lower pre-HU and recent HbF and higher dosing. They experienced more urgent hospital use during the year framing recent assessment than during PBest; these findings were supported by sensitivity analysis.

CONCLUSIONS

Decline from PBest HbF is a novel approach to assess HU effectiveness, is common among youth and may represent suboptimal adherence. Larger prospective studies using additional adherence measures are needed to confirm our approach of tracking HbF deviation over time and to define an appropriate cutoff.

Study protocol for a randomized controlled trial to assess the feasibility of an open label intervention to improve hydroxyurea adherence in youth with sickle cell disease

BACKGROUND

Community health workers (CHW) are increasingly recognized as a strategy to improve health outcomes for the underserved with chronic diseases but has not been formally explored in adolescents with sickle cell disease (SCD). SCD primarily affects African American, Hispanic and other traditionally underserved populations. Hydroxyurea (HU), an oral, once-daily medication, is the only approved therapeutic drug for sickle cell disease and markedly reduces symptoms, morbidity and mortality and improves quality of life largely by increasing hemoglobin F blood levels. This paper presents the rationale, study design and protocol for an open label randomized controlled trial to improve parent-youth partnerships in self-management and medication adherence to HU in adolescents with SCD.

METHODS/DESIGN

A CHW intervention augmented by text messaging was designed for adolescents with SCD ages 10-18years and their parents to improve daily HU adherence. Thirty adolescent parent dyads will be randomized with 2:1 intervention group allocation. Intervention dyads will establish a relationship with a culturally aligned CHW to identify barriers to HU use, identify cues to build a habit, and develop a dyad partnership to improve daily HU adherence and achieve their individualized "personal best" hemoglobin F target. Intervention feasibility, acceptability and efficacy will be assessed via a 2-site trial. Outcomes of interest are HU adherence, dyad self-management communication, quality of life, and resource use.

DISCUSSION

Despite known benefits, poor HU adherence is common. If feasible and acceptable, the proposed intervention may improve health of underserved adolescents with SCD by enhancing long-term HU adherence.

TRIAL REGISTRATION

NCT02029742.

Erythrocyte oxidative stress markers in children with sickle cell disease

OBJECTIVE

To determine eight parameters of oxidative stress markers in erythrocytes from children with sickle cell disease and compare with the same parameters in erythrocytes from healthy children, since oxidative stress plays an important role in the pathophysiology of sickle cell disease and because this disease is a serious public health problem in many countries.

METHODS

Blood samples were obtained from 45 children with sickle cell disease (21 males and 24 females with a mean age of 9 years; range: 3-13 years) and 280 blood samples were obtained from children without hemoglobinopathies (137 males and 143 females with a mean age of 10 years; range: 8-11 years), as a control group. All blood samples were analyzed for methemoglobin, reduced glutathione, thiobarbituric acid reactive substances, percentage of hemolysis, reactive oxygen species, and activity of the enzymes glucose 6-phosphate dehydrogenase, superoxide dismutase, and catalase. Data were analyzed using Student's t-test and were expressed as the mean±standard deviation. A p-value of <0.05 was considered significant.

RESULTS

Significant differences were observed between children with sickle cell disease and the control group for the parameters methemoglobin, thiobarbituric acid reactive substances, hemolysis, glucose 6-phosphate dehydrogenase activity, and reactive oxygen species, with higher levels in the patients than in the controls.

CONCLUSIONS

Oxidative stress parameters in children's erythrocytes were determined using simple laboratory methods with small volumes of blood; these biomarkers can be useful to evaluate disease progression and outcomes in patients.

Novel Use of Hydroxyurea in an African Region With Malaria: Protocol for a Randomized Controlled Clinical Trial

BACKGROUND

Sickle cell anemia (SCA), one of most prevalent monogenic diseases worldwide, is caused by a glutamic acid to valine substitution on the beta globin protein of hemoglobin, which leads to hemolytic anemia. Hydroxyurea, the only disease-modifying therapy approved by the Food and Drug Administration for SCA, has proven to be a viable therapeutic option for SCA patients in resource-rich settings, given clinical improvements experienced while taking the medication and its once-daily oral dosing. Significant studies have demonstrated its safety and clinical efficacy among children and adults in developed countries. In Sub-Saharan Africa, however, the risk of malaria, hematologic toxicities, and safety of hydroxyurea in children with SCA living in malaria-endemic areas are unknown.

OBJECTIVES

Study objectives include determining the incidence of malaria in SCA patients taking hydroxyurea versus placebo; establishing the frequency of hematologic toxicities and adverse events (AEs) in children with SCA treated with hydroxyurea versus placebo; and defining the relationships between hydroxyurea treatment and fetal hemoglobin, soluble intracellular adhesion molecule-1, and nitric oxide levels, and between levels of these factors and risk of subsequent malaria.

METHODS

Novel use Of Hydroxyurea in an African Region with Malaria (NOHARM, NCT01976416) is a prospective, randomized, placebo-controlled, double-blinded phase III trial to compare risk of malaria with oral hydroxyurea versus placebo. Children will be recruited from the Mulago Hospital Sickle Cell Clinic in Kampala, Uganda.

RESULTS

Two hundred Ugandan children aged between 1.00 and 3.99 years with confirmed SCA will be randomized into treatment groups by order of entry in the study, based on a predetermined blinded randomization list. The primary outcome of the trial is malaria incidence in the 2 study groups, defined as episodes of clinical malaria occurring over the 1-year randomized study treatment period.

CONCLUSION

NOHARM will be the first prospective randomized, placebo-controlled clinical trial investigating the use of hydroxyurea for children with SCA in a malaria-endemic region within Africa. The results of this trial have the potential to significantly advance understanding of how to safely and effectively use hydroxyurea in children with SCA in malaria-endemic areas.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01976416; https://clinicaltrials.gov/ct2/show/NCT01976416 (Archived by WebCite at http://www.webcitation.org/6hmoilZnp).

rs11886868 and rs4671393 of BCL11A associated with HbF level variation and modulate clinical events among sickle cell anemia patients

AIMS

Fetal hemoglobin (HbF) modulates the phenotype of sickle cell anemia (SCA) by inhibiting deoxy sickle hemoglobin (HbS) polymerization. HbF genes are genetically regulated, and the level of HbF and its distribution among sickle erythrocytes is highly variable. Herein, we aimed to determine whether two functional polymorphisms of BCL11A are implicated in the variation of HbF and clinical events in SCA Tunisian patients.

MATERIAL AND METHODS

The studied population consisted of 148 SCA patients with SS phenotype. The group of patients was divided into two subgroups according to the threshold point of %HbF which is 15%. Genotyping of rs11886868 and rs4671393 was performed using PCR/Sequencing. To test for trait association with the candidate SNPs, genotype and allele frequencies between 'group who had %HbF < 15' and 'group who had %HbF >15' (controls) were compared using Pearson's chi-square test (compare 2, version 1.02). The association of each genotype and the combined genotype with complications was performed by logistic regression test.

RESULTS

Our findings showed that the majority of patients carried genotype CT of rs11886868 and genotypes AG and GG of rs4671393 present HbF level < 15%. RR = 0.08, RR = 0.176, and RR = 0.189, respectively. The results showed a significant association between the alleles T of rs11886868 and G of rs4671393 and %HbF < 15% with P = 0.016; RR = 0.39 and P = 8.9 × 10(-3): RR = 0.567, respectively. Interestingly, the C allele of the rs11886868 and the A allele of the rs46713939 were associated with an ameliorated phenotype in patient's SCA. The combination of the genotypes GG and CT explains more phenotypic variance than the sum of the two BCL11A SNPs taken individually.

Neutrophils, platelets, and inflammatory pathways at the nexus of sickle cell disease pathophysiology

Sickle cell disease (SCD) is a severe genetic blood disorder characterized by hemolytic anemia, episodic vaso-occlusion, and progressive organ damage. Current management of the disease remains symptomatic or preventative. Specific treatment targeting major complications such as vaso-occlusion is still lacking. Recent studies have identified various cellular and molecular factors that contribute to the pathophysiology of SCD. Here, we review the role of these elements and discuss the opportunities for therapeutic intervention.

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.

Acute hemolytic vascular inflammatory processes are prevented by nitric oxide replacement or a single dose of hydroxyurea

Hemolysis and consequent release of cell-free hemoglobin (CFHb) impair vascular nitric oxide (NO) bioavailability and cause oxidative and inflammatory processes. Hydroxyurea (HU), a common therapy for sickle cell disease (SCD), induces fetal Hb production and can act as an NO donor. We evaluated the acute inflammatory effects of intravenous water-induced hemolysis in C57BL/6 mice and determined the abilities of an NO donor, diethylamine NONOate (DEANO), and a single dose of HU to modulate this inflammation. Intravenous water induced acute hemolysis in C57BL/6 mice, attaining plasma Hb levels comparable to those observed in chimeric SCD mice. This hemolysis resulted in significant and rapid systemic inflammation and vascular leukocyte recruitment within 15 minutes, accompanied by NO metabolite generation. Administration of another potent NO scavenger (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) to C57BL/6 mice induced similar alterations in leukocyte recruitment, whereas hemin-induced inflammation occurred over a longer time frame. Importantly, the acute inflammatory effects of water-induced hemolysis were abolished by the simultaneous administration of DEANO or HU, without altering CFHb, in an NO pathway-mediated manner. In vitro, HU partially reversed the Hb-mediated induction of endothelial proinflammatory cytokine secretion and adhesion molecule expression. In summary, pathophysiological levels of hemolysis trigger an immediate inflammatory response, possibly mediated by vascular NO consumption. HU presents beneficial anti-inflammatory effects by inhibiting rapid-onset hemolytic inflammation via an NO-dependent mechanism, independently of fetal Hb elevation. Data provide novel insights into mechanisms of hemolytic inflammation and further support perspectives for the use of HU as an acute treatment for SCD and other hemolytic disorders.

Emerging drugs for sickle cell anemia

INTRODUCTION

The search for effective therapeutic interventions for sickle cell disease (SCD) has been an ongoing endeavor for over 50 years. During this period, only hydroxyurea (HU), which received US FDA approval in February 1998, was identified as an effective therapeutic agent in preventing or ameliorating the frequency of vaso-occlusive crises, acute chest syndrome and the need for blood transfusion. Approximately 25% of patients with sickle cell anemia (SCA), however, do not respond to HU and some patients experiencing serious side effects of this chemotherapeutic agent. Nevertheless, the success of HU opened the sluice gates to identify other effective drug therapies. The objective of this review is to describe the emerging drug therapies for SCA.

AREAS COVERED

In this review, we describe the pathophysiology of SCD and provide an in-depth analysis of the current and new pharmacologic therapies in the field. Literature searches involved multiple databases including Medline In-Process & Other Non-Indexed Citations, MEDLINE, Embase, Cochrane Database of Systematic Reviews, and Scopus.

EXPERT OPINION

SCA is a heterogeneous disease that has caused tremendous global morbidity and early mortality. More effective, individualized and inexpensive therapies are needed. New therapies targeting multiple pathways in its complex pathophysiology are under investigation.

Reduced plasma angiotensin II levels are reversed by hydroxyurea treatment in mice with sickle cell disease

AIMS

Sickle cell disease (SCD) pathogenesis leads to recurrent vaso-occlusive and hemolytic processes, causing numerous clinical complications including renal damage. As vasoconstrictive mechanisms may be enhanced in SCD, due to endothelial dysfunction and vasoactive protein production, we aimed to determine whether the expression of proteins of the renin-angiotensin system (RAS) may be altered in an animal model of SCD.

MAIN METHODS

Plasma angiotensin II (Ang II) was measured in C57BL/6 (WT) mice and mice with SCD by ELISA, while quantitative PCR was used to compare the expressions of the genes encoding the angiotensin-II-receptors 1 and 2 (AT1R and AT2R) and the angiotensin-converting enzymes (ACE1 and ACE2) in the kidneys, hearts, livers and brains of mice. The effects of hydroxyurea (HU; 50-75mg/kg/day, 4weeks) treatment on these parameters were also determined.

KEY FINDINGS

Plasma Ang II was significantly diminished in SCD mice, compared with WT mice, in association with decreased AT1R and ACE1 expressions in SCD mice kidneys. Treatment of SCD mice with HU reduced leukocyte and platelet counts and increased plasma Ang II to levels similar to those of WT mice. HU also increased AT1R and ACE2 gene expression in the kidney and heart.

SIGNIFICANCE

Results indicate an imbalanced RAS in an SCD mouse model; HU therapy may be able to restore some RAS parameters in these mice. Further investigations regarding Ang II production and the RAS in human SCD may be warranted, as such changes may reflect or contribute to renal damage and alterations in blood pressure.

Sickle cell disease in mice is associated with sensitization of sensory nerve fibers

The pain phenotype in sickle cell disease (SCD) patients is highly variable. A small percentage of SCD patients experience many vaso-occlusive crises/year, 5% of patients account for over 30% of pain episodes, while 39% report few episodes of severe pain. Clearly, a better understanding of the pathobiology of SCD is needed to improve its therapy. Humanized sickle cell mice recapitulate several phenotypes of SCD patients and provide a model for the study of SCD pain. Researchers have shown that one strain of humanized SCD mice, the BERK strain, has abnormal pain phenotype. However, the nociception phenotype of another humanized SCD mouse strain, the Townes strain, has not been described. In a large cross-sectional study of BERK and Townes SCD mice, we examined thermosensory response and sensory nerve fiber function using sine-wave electrical stimulation at 2000, 250, and 5 Hz to stimulate preferentially Aβ, Aδ, and C sensory nerve fibers, respectively. We found that BERK and Townes mice, compared to respective controls, had decreases in 2000, 250, and 5 Hz current vocalization thresholds in patterns that suggest sensitization of a broad spectrum of sensory nerve fibers. In addition, the pattern of sensitization of sensory fibers varied according to strain, sex, age, and mouse genotype. In a similarly variable pattern, Townes and BERKs also had significantly altered sensitivity to noxious thermal stimuli in agreement with what has been shown by others. In summary, the analysis of somatosensory function using sine-wave electrical stimulation in humanized sickle cell mice suggests that in SCD, both myelinated and unmyelinated, fibers are sensitized. The pattern of sensory fiber sensitization is distinct from that observed in pain models of neuropathic and inflammatory pain. These findings raise the possibility that sensitization of a broad spectrum of sensory fibers might contribute to the altered and variable nociception phenotype in SCD.

Acute pulmonary complications of sickle cell disease

Acute pulmonary problems in sickle cell disease (SCD) patients, in particular acute chest syndrome (ACS), cause significant mortality and morbidity. It is important to differentiate ACS from pneumonia to avoid inappropriate or inadequate treatment. Asthma may increase the risk of ACS and co-morbid asthma and SCD are associated with worse patient outcomes and, in preclinical models, more severe inflammation. Recurrent wheezing, however, can occur in the absence of a diagnosis of asthma; it is likely due to SCD related inflammation and additional therapies than those that treat asthma may be required. Further research is merited to clarify these issues.

Emerging science of hydroxyurea therapy for pediatric sickle cell disease

Hydroxyurea (HU) is the sole approved pharmacological therapy for sickle cell disease (SCD). Higher levels of fetal hemoglobin (HbF) diminish deoxygenated sickle globin polymerization in vitro and clinically reduce the incidence of disease morbidities. Clinical and laboratory effects of HU largely result from induction of HbF expression, though to a highly variable extent. Baseline and HU-induced HbF expression are both inherited complex traits. In children with SCD, baseline HbF remains the best predictor of drug-induced levels, but this accounts for only a portion of the induction. A limited number of validated genetic loci are strongly associated with higher baseline HbF levels in SCD. For induced HbF levels, genetic approaches using candidate single-nucleotide polymorphisms (SNPs) have identified some of these same loci as being also associated with induction. However, SNP associations with induced HbF are only partially independent of baseline levels. Additional approaches to understanding the impact of HU on HbF and its other therapeutic effects on SCD include pharmacokinetic, gene expression-based, and epigenetic analyses in patients and through studies in existing murine models for SCD. Understanding the genetic and other factors underlying the variability in therapeutic effects of HU for pediatric SCD is critical for prospectively predicting good responders and for designing other effective therapies.

A prospective newborn screening and treatment program for sickle cell anemia in Luanda, Angola

Over 300,000 infants are born annually with sickle cell anemia (SCA) in sub-Saharan Africa, and >50% die young from infection or anemia, usually without diagnosis of SCA. Early identification by newborn screening (NBS), followed by simple interventions dramatically reduced the mortality of SCA in the United States, but this strategy is not yet established in Africa. We designed and implemented a proof-of-principle NBS and treatment program for SCA in Angola, with focus on capacity building and local ownership. Dried bloodspots from newborns were collected from five birthing centers. Hemoglobin identification was performed using isoelectric focusing; samples with abnormal hemoglobin patterns were analyzed by capillary electrophoresis. Infants with abnormal FS or FSC patterns were enrolled in a newborn clinic to initiate penicillin prophylaxis and receive education, pneumococcal immunization, and insecticide-treated bed nets. A total of 36,453 infants were screened with 77.31% FA, 21.03% FAS, 1.51% FS, and 0.019% FSC. A majority (54.3%) of affected infants were successfully contacted and brought to clinical care. Compliance in the newborn clinic was excellent (96.6%). Calculated first-year mortality rate for babies with SCA compares favorably to the national infant mortality rate (6.8 vs. 9.8%). The SCA burden is extremely high in Angola, but NBS is feasible. Capacity building and training provide local healthcare workers with skills needed for a functional screening program and clinic. Contact and retrieval of all affected SCA infants remains a challenge, but families are compliant with clinic appointments and treatment. Early mortality data suggest screening and early preventive care saves lives.

How does catalase release nitric oxide? A computational structure-activity relationship study

Hydroxyurea (HU) is the only FDA approved medication for treating sickle cell disease in adults. The primary mechanism of action is pharmacological elevation of nitric oxide (NO) levels which induces propagation of fetal hemoglobin. HU is known to undergo redox reactions with heme based enzymes like hemoglobin and catalase to produce NO. However, specific details about the HU based NO release remain unknown. Experimental studies indicate that interaction of HU with human catalase compound I produces NO. Presently, we combine flexible receptor-flexible substrate induced fit docking (IFD) with energy decomposition analyses to examine the atomic level details of a possible key step in the clinical conversion of HU to NO. Substrate binding modes of nine HU analogs with catalase compound I were investigated to determine the essential properties necessary for effective NO release. Three major binding orientations were found that provide insight into the possible reaction mechanisms for producing NO. Further results show that anion/radical intermediates produced as part of these mechanisms would be stabilized by hydrogen bonding interactions from distal residues His75, Asn148, Gln168, and oxoferryl-heme. These details will ideally contribute to both a clearer mechanistic picture and provide insights for future structure based drug design efforts.

Development of phenotypic screening assays for γ-globin induction using primary human bone marrow day 7 erythroid progenitor cells

Sickle cell anemia (SCA) is a genetic disorder of the β-globin gene. SCA results in chronic ischemia with pain and tissue injury. The extent of SCA symptoms can be ameliorated by treatment with drugs, which result in increasing the levels of γ-globin in patient red blood cells. Hydroxyurea (HU) is a Food and Drug Administration-approved drug for SCA, but it has dose-limiting toxicity, and patients exhibit highly variable treatment responses. To identify compounds that may lead to the development of better and safer medicines, we have established a method using primary human bone marrow day 7 erythroid progenitor cells (EPCs) to screen for compounds that induce γ-globin production. First, human marrow CD34(+) cells were cultured and expanded for 7 days and characterized for the expression of erythroid differentiation markers (CD71, CD36, and CD235a). Second, fresh or cryopreserved EPCs were treated with compounds for 3 days in 384-well plates followed by γ-globin quantification by an enzyme-linked immunosorbent assay (ELISA), which was validated using HU and decitabine. From the 7408 compounds screened, we identified at least one new compound with confirmed γ-globin-inducing activity. Hits are undergoing analysis in secondary assays. In this article, we describe the method of generating fit-for-purpose EPCs; the development, optimization, and validation of the ELISA and secondary assays for γ-globin detection; and screening results.