Hydroxyurea therapy for sickle cell anemia

Tolerability and age-dependent toxicokinetics following perinatal hydroxyurea treatment in Sprague Dawley rats

Hydroxyurea (HU) is a valuable therapy for individuals with sickle cell anemia. With increased use of HU in children and throughout their lives, it is important to understand the potential effects of HU therapy on their development and fertility. Thus, studies were conducted to identify appropriate doses to examine long‐term effects of prenatal and early postnatal HU exposure and to understand kinetics of HU at various life stages. Pregnant Sprague Dawley dams were administered HU (0–150 mg/kg/day) via oral gavage from gestation days 17 to 21 and during lactation. Pups were dosed with the same dose as their respective dam starting on postnatal day (PND) 10 and up to PND 34. There was minimal maternal toxicity, and no significant effects on littering at any dose of HU. Starting on ~PND 16, offspring displayed skin discoloration and alopecia at doses ≥75 mg/kg/day and lower body weight compared to controls at doses ≥100 mg/kg/day. Gestational transfer of HU was observed, but there was minimal evidence of lactational transfer. Our toxicokinetic studies suggest that the internal dose in offspring may be altered due to age, but not due to sex. The plasma area under the curve, a measure of systemic exposure, at doses tolerated by offspring was threefold to sevenfold lower than the internal therapeutic dose in humans. Therefore, strategies to establish clinically relevant exposures in animal studies are needed. Overall, these data are useful for the design of appropriate nonclinical studies in the future to evaluate the consequences of long‐term HU treatment starting in childhood.

Increased use of hydroxyurea (HU) to treat sickle cell disease in children and throughout their lives augments the importance of understanding potential effects of HU on development and fertility. To inform the design of studies to evaluate long‐term safety of HU use in children, tolerability of prenatal and early postnatal HU treatment was evaluated in Sprague Dawley rats. Additionally, studies investigating gestational and lactational transfer of HU and how toxicokinetics of HU vary with age were conducted.

Deferoxamine produces nitric oxide under ferricyanide oxidation, blood incubation, and UV-irradiation

Deferoxamine (DFO), an iron chelator, is used therapeutically for the removal of excess iron in multiple clinical conditions such as beta thalassemia and intracerebral hemorrhage. DFO is also used as an iron chelator and hypoxia-mimetic agent in in vivo and in vitro basic research. Here we unexpectedly discover DFO to be a nitric oxide (NO) precursor in experiments where it was intended to act as an iron chelator. Production of NO from aqueous solutions of DFO was directly observed by ozone-based chemiluminescence using a ferricyanide-based assay and was confirmed by electron paramagnetic resonance (EPR). DFO also produced NO following exposure to ultraviolet light, and its incubation with sheep adult and fetal blood resulted in considerable formation of iron nitrosyl hemoglobin, as confirmed by both visible spectroscopy and EPR. These results suggest that experiments using DFO can be confounded by concomitant production of NO, and offer new insight into some of DFO's unexplained clinical side effects such as hypotension.

Hydroxyurea: a reappraisal of its cutaneous side effects and their management

Hydroxyurea (HU) is known to cause a broad spectrum of cutaneous side effects, ranging from relatively benign to severe. Although dermatologists are often consulted for the treatment of these side effects, a comprehensive resource discussing the different types and their management is lacking. In this study, we conducted a literature search in order to critically evaluate the reported types and management of hydroxyurea's cutaneous side effects, as well as review its mechanism of action, dermatologic uses, and common systemic side effects. Relatively common and benign side effects include hyperpigmentation, xerosis, and skin atrophy. While serious cutaneous side effects such as leg ulcers or nonmelanoma skin cancers occur in a substantial proportion of patients, these may resolve with HU discontinuation and proper dermatologic management. Therefore, it is crucial for dermatologists to be aware of these various cutaneous side effects and their management as prompt diagnosis and proper treatment will improve patient outcomes.

Vaso-occlusive crises and costs of sickle cell disease in patients with commercial, Medicaid, and Medicare insurance - the perspective of private and public payers

AIM

To characterize vaso-occlusive crises (VOCs) and describe healthcare costs among commercially-insured, Medicaid-insured, and Medicare-insured patients with sickle cell disease (SCD).

MATERIALS AND METHODS

The IBM Truven Health MarketScan Commercial (2000-2018), Medicaid Analytic eXtract (2008-2014), and Medicare Research Identifiable Files (2012-2016) databases were used to identify patients with ≥2 SCD diagnoses. Study measures were evaluated during a 12-month follow-up period, stratified by annual number of VOCs (i.e. 0, 1, and ≥2).

RESULTS

Among 16,092 commercially-insured patients (mean age = 36.7 years), 35.3% had 1+ VOCs. Mean annual total all-cause healthcare costs were $15,747, $27,194, and $64,555 for patients with 0, 1, and 2+ VOCs, respectively. Total all-cause healthcare costs were mainly driven by inpatient (0 VOC = 31.0%, 1 VOC = 53.1%, 2+ VOCs = 65.4%) and SCD-related costs (0 VOC = 56.4%, 1 VOC = 78.4%, 2+ VOCs = 93.9%). Among 18,287 Medicaid-insured patients (mean age = 28.5 years, fee-for-service = 50.2%), 63.9% had 1+ VOCs. Mean annual total all-cause healthcare costs were $16,750, $29,880, and $64,566 for patients with 0, 1, and 2+ VOCs, respectively. Inpatient costs (0 VOC = 37.2%, 1 VOC = 64.3%, 2+ VOCs = 72.9%) and SCD-related costs (0 VOC = 60.9%, 1 VOC = 73.8%, 2+ VOCs = 92.2%) accounted for a significant proportion of total all-cause healthcare costs. Among 15,431 Medicare-insured patients (mean age = 48.2 years), 55.1% had 1+ VOCs. Mean annual total all-cause healthcare costs were $21,877, $29,250, and $58,308 for patients with 0, 1, and ≥2 VOCs, respectively. Total all-cause healthcare costs were mainly driven by inpatient (0 VOC = 47.9%, 1 VOC = 54.9%, 2+ VOCs = 67.5%) and SCD-related costs (0 VOC = 74.9%, 1 VOC = 84.4%, 2+ VOCs = 95.3%).

LIMITATIONS

VOCs managed at home were not captured. Analyses were descriptive in an observational setting; thus, no causal relationships can be inferred.

CONCLUSIONS

A high proportion of patients experienced VOCs across payers. Furthermore, inpatient and SCD-related costs accounted for a significant proportion of total all-cause healthcare costs, which increased with VOC frequency.

New Zileuton-Hydroxycinnamic Acid Hybrids: Synthesis and Structure-Activity Relationship towards 5-Lipoxygenase Inhibition

A novel series of zileuton-hydroxycinnamic acid hybrids were synthesized and screened as 5-lipoxygenase (5-LO) inhibitors in stimulated HEK293 cells and polymorphonuclear leukocytes (PMNL). Zileuton’s (1) benzo[b]thiophene and hydroxyurea subunits combined with hydroxycinnamic acid esters’ ester linkage and phenolic acid moieties were investigated. Compound 28, bearing zileuton’s (1) benzo[b]thiophene and sinapic acid phenethyl ester’s (2) α,β-unsaturated phenolic acid moiety 28, was shown to be equipotent to zileuton (1), the only clinically approved 5-LO inhibitor, in stimulated HEK293 cells. Compound 28 was three times as active as zileuton (1) for the inhibition of 5-LO in PMNL. Compound 37, bearing the same sinapic acid (3,5-dimethoxy-4-hydroxy substitution) moiety as 28, combined with zileuton’s (1) hydroxyurea subunit was inactive. This result shows that the zileuton’s (1) benzo[b]thiophene moiety is essential for the inhibition of 5-LO product biosynthesis with our hydrids. Unlike zileuton (1), Compound 28 formed two π–π interactions with Phe177 and Phe421 as predicted when docked into 5-LO. Compound 28 was the only docked ligand that showed a π–π interaction with Phe177 which may play a part in product specificity as reported.

Changing the Clinical Paradigm of Hydroxyurea Treatment for Sickle Cell Anemia Through Precision Medicine

Sickle cell anemia (SCA) is a common and devastating inherited blood disorder, affecting millions of people across the world. Without treatment, SCA results in tremendous morbidity and early mortality. Hydroxyurea is the primary and most well-established pharmacologic therapy with proven benefits to ameliorate the clinical course of SCA, primarily due to its ability to increase the expression of fetal hemoglobin (HbF), which prevents sickling of red blood cells. The optimal induction of HbF depends upon selection and maintenance of the proper dose that maximizes benefits and minimizes toxicity. Due to the significant interpatient variability in hydroxyurea pharmacokinetics, pharmacodynamics, and dosing, most patients treated with hydroxyurea receive suboptimal doses and have only modest treatment responses. Recognizing this variability, using a precision medicine approach, we developed and prospectively evaluated an individualized dosing model for children with SCA, designed to optimize the hydroxyurea dose and clinical response. We utilize novel laboratory methods and a sparse sampling strategy requiring only 10 μL of blood collected 15 minutes, 60 minutes, and 180 minutes after a test dose. We use Bayesian adaptive control to estimate hydroxyurea exposure and to select an individual, optimal starting dose. This dosing model has resulted in HbF responses >30-40%, levels beyond what is achieved with traditional weight-based dosing and trial and error dose escalation. This hydroxyurea dosing strategy, if widely implemented, has the potential to change the treatment paradigm of hydroxyurea therapy and improve outcomes for the millions of patients with SCA across the world.

Oral hyperpigmentation associated with hydroxyurea in a patient with polycythemia vera: A case report

Patients may report to health practitioners with unusual symptoms that necessitate a thorough examination and review of underlying medical conditions and medications for rare side effects. Hence, it is crucial to report such rare cases to raise awareness and increase the related body of knowledge. Hydroxyurea‐associated oral hyperpigmentation has been reported.

End points for sickle cell disease clinical trials: renal and cardiopulmonary, cure, and low-resource settings

To address the global burden of sickle cell disease and the need for novel therapies, the American Society of Hematology partnered with the US Food and Drug Administration to engage the work of 7 panels of clinicians, investigators, and patients to develop consensus recommendations for clinical trial end points. The panels conducted their work through literature reviews, assessment of available evidence, and expert judgment focusing on end points related to patient-reported outcome, pain (non-patient-reported outcomes), the brain, end-organ considerations, biomarkers, measurement of cure, and low-resource settings. This article presents the findings and recommendations of the end-organ considerations, measurement of cure, and low-resource settings panels as well as relevant findings and recommendations from the biomarkers panel.

Managing patients with sickle cell disease in primary care

Sickle cell disease (SCD) is a group of disorders affecting the hemoglobin in erythrocytes. SCD is associated with significant morbidity and mortality and occurs most commonly among people of African ancestry. In 2014, the National Heart, Lung, and Blood Institute updated its guidelines for the management of SCD. These guidelines were implemented to provide evidence-based recommendations to assist primary care clinicians in the proper management of patients with SCD. This article reviews the current practice guidelines for SCD, with attention to health maintenance and hydroxyurea.

CXCR4hi effector neutrophils in sickle cell anemia: potential role for elevated circulating serotonin (5-HT) in CXCR4hi neutrophil polarization

Leukocyte recruitment and heterocellular aggregate formation drive the inflammatory vaso-occlusive processes associated with sickle cell anemia (SCA). We characterized neutrophils in a population of patients with SCA and investigated whether platelet-derived molecules can induce phenotypic alterations in this cell type. Imaging flow cytometry analysis demonstrated that the frequency of circulating CXCR4^hi neutrophils was significantly higher in steady-state SCA individuals than in healthy control individuals and that these cells presented increased CD11b activation and toll-like receptor-4 expression. SCA neutrophils display increased neutrophil-platelet aggregation, and CXCR4^hi neutrophils demonstrated augmented neutrophil-platelet aggregate frequency with a higher mean number of platelets adhered per neutrophil. Importantly, incubation of neutrophils with platelets significantly elevated their CXCR4 expression, while SCA plasma was found to induce CXCR4^hi neutrophil polarization significantly more than control plasma. SCA individuals had significantly increased plasma levels of serotonin (5-HT), and serotonin molecule and SCA plasma induced neutrophil CXCR4 expression in a serotonin-receptor-dependent manner. Thus, the augmented CXCR4^hi neutrophil population may contribute to mechanisms that promote vaso-occlusion in SCA; furthermore, circulating serotonin, derived from platelet activation, may play a role in the polarization of neutrophils, suggesting that serotonin-receptor antagonists or serotonin reuptake inhibitors could represent therapeutic approaches to reduce neutrophil activation in SCA.

Quality of life assessments in a cohort of Mozambican children with sickle cell disease

Introduction

sickle cell disease (SCD) has significant pediatric morbidity and mortality in sub-Saharan Africa, where access to therapies such as hydroxyurea and opioids is often limited. Poor disease control and Pain management adversely affects the well-being and mental health of affected children. Questionnaires have been utilized in other regions to report the quality of life (QOL) in children with SCD, but assessments from Africa are lacking.

Methods

children age 2-14 years with SCD presenting for routine outpatient consultations at Hospital Central de Maputo from June-August 2017 were offered participation. After informed consent, the Pediatric QOL Inventory (PedsQL) SCD Module was administered to all caregivers and children > 5 years. Responses were scored from 0-100, with higher scores representing better QOL.

Results

a total of 14 children were included, with six (43%), four (29%), two (14%), and two (14%) from the age groups of 2-4, 5-7, 8-12, and 13-14 years, respectively. Mean overall patient QOL was 65.3 and 56.0 in child and caregiver respondents. In patients > 5 years, the difference in mean overall QOL for those on/not on hydroxyurea was 0.6 (66.5-64.9) in child respondents and 15.8 (68.4-52.6) in caregiver respondents. Domains related to worry/emotions and communication scored lower in QOL than Pain-related domains for both patient and caregiver respondents.

Conclusion

SCD has a negative impact on QOL as reported by this cohort of Mozambican pediatric patients and caregivers, with Pain being less of a concern than emotional and interpersonal issues. A comprehensive, child-focused care approach with robust psychosocial support is needed.

MEMSID: Results From a Phase 2 Pilot Study on Memantine Treatment for Sickle Cell Disease

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Synthesis and evaluation of resveratrol derivatives as fetal hemoglobin inducers

Resveratrol (RVT) derivatives (10a-i) were designed, synthesized, and evaluated for their potential as gamma-globin inducers in treating Sickle Cell Disease (SCD) symptoms. All compounds were able to release NO at different levels ranging from 0 to 26.3%, while RVT did not demonstrate this effect. In vivo, the antinociceptive effect was characterized using an acetic acid-induced abdominal contortion model. All compounds exhibited different levels of protection, ranging from 5.9 to 37.3%; the compound 10a was the most potent among the series. At concentrations between 3.13 and 12.5 µM, the derivative 10a resulted in a reduction of 41.1-64.3% in the TNF-α levels in the supernatants of macrophages that were previously LPS-stimulated. This inhibitory effect was higher than that of RVT used as the control. In addition, the compound 10a and RVT induced double the production of the gamma-globin chains (γG + γA), compared to the vehicle, using CD34+ cells. Compound 10a also did not induce membrane perturbation and it was not mutagenic in the in vivo assay. Thus, compound 10a emerged as a new prototype of the gamma-globin-inducer group with additional analgesic and anti-inflammatory activities and proving to be a useful alternative to treat SCD symptoms.

Hydroxyurea Dose Escalation for Sickle Cell Anemia in Sub-Saharan Africa

BACKGROUND

Hydroxyurea has proven safety, feasibility, and efficacy in children with sickle cell anemia in sub-Saharan Africa, with studies showing a reduced incidence of vaso-occlusive events and reduced mortality. Dosing standards remain undetermined, however, and whether escalation to the maximum tolerated dose confers clinical benefits that outweigh treatment-related toxic effects is unknown.

METHODS

In a randomized, double-blind trial, we compared hydroxyurea at a fixed dose (approximately 20 mg per kilogram of body weight per day) with dose escalation (approximately 30 mg per kilogram per day). The primary outcome was a hemoglobin level of 9.0 g or more per deciliter or a fetal hemoglobin level of 20% or more after 24 months. Secondary outcomes included the incidences of malaria, vaso-occlusive crises, and serious adverse events.

RESULTS

Children received hydroxyurea at a fixed dose (94 children; mean [±SD] age, 4.6±1.0 years) or with dose escalation (93 children; mean age, 4.8±0.9 years); the mean doses were 19.2±1.8 mg per kilogram per day and 29.5±3.6 mg per kilogram per day, respectively. The data and safety monitoring board halted the trial when the numbers of clinical events were significantly lower among children receiving escalated dosing than among those receiving a fixed dose. At trial closure, 86% of the children in the dose-escalation group had reached the primary-outcome thresholds, as compared with 37% of the children in the fixed-dose group (P<0.001). Children in the dose-escalation group had fewer sickle cell-related adverse events (incidence rate ratio, 0.43; 95% confidence interval [CI], 0.34 to 0.54), vaso-occlusive pain crises (incidence rate ratio, 0.43; 95% CI, 0.34 to 0.56), cases of acute chest syndrome or pneumonia (incidence rate ratio, 0.27; 95% CI, 0.11 to 0.56), transfusions (incidence rate ratio, 0.30; 95% CI, 0.20 to 0.43), and hospitalizations (incidence rate ratio, 0.21; 95% CI, 0.13 to 0.34). Laboratory-confirmed dose-limiting toxic effects were similar in the two groups, and there were no cases of severe neutropenia or thrombocytopenia.

CONCLUSIONS

Among children with sickle cell anemia in sub-Saharan Africa, hydroxyurea with dose escalation had superior clinical efficacy to that of fixed-dose hydroxyurea, with equivalent safety. (Funded by the Doris Duke Charitable Foundation and the Cincinnati Children's Research Foundation; NOHARM MTD ClinicalTrials.gov number, NCT03128515.).

The vaso-occlusive pain crisis in sickle cell disease: Definition, pathophysiology, and management

Early diagnosis, treatment, and prevention of a vaso-occlusive crisis (VOC) are critical to the management of patients with sickle cell disease. It is essential to differentiate between VOC-associated pain and chronic pain, hyperalgesia, neuropathy, and neuropathic pain. The pathophysiology of VOCs includes polymerization of abnormal sickle hemoglobin, inflammation, and adhesion. Hydroxyurea, L-glutamine, crizanlizumab, and voxelotor have been approved by the US Food and Drug Administration for reducing the frequency of VOCs; the European Medicines Agency has approved only hydroxyurea. Other novel treatments are in late-stage clinical development in both the United States and the European Union. The development of agents for prevention and treatment of VOCs should be driven by our understanding of its pathophysiology.

Effect of High-dose Vitamin A Supplementation in Children With Sickle Cell Disease: A Randomized, Double-blind, Dose-finding Pilot Study

Suboptimal vitamin A status (serum retinol <30 µg/dL) is associated with poor clinical outcomes in children with the hemoglobin-SS disease (HbSS), and supplementation with the recommended daily allowance of retinol is ineffective in improving vitamin A status. In a single-center randomized blinded dose-finding pilot study, we compared vitamin A and nutritional status in children with HbSS to healthy children and explored the impact of high-dose supplementation on the primary outcome serum vitamin A status. Exploratory outcomes included hematologic, nutritional, immunologic, and muscle function status in children with HbSS. A mixed-effects linear regression model evaluated associations between vitamin A dose, serum retinol, and exploratory outcomes. Twenty healthy children participated, and 22 subjects with HbSS were randomized to oral 3000 or 6000 IU/d retinol for 8 weeks; 21 subjects completed all evaluations. Serum retinol, growth, and nutritional status were all suboptimal in HbSS subjects at baseline, and supplementation did not change vitamin A status. Fetal hemoglobin (Δ=2.5, 95% confidence interval [CI], 0.5-4.3), mean corpuscular volume (Δ=2.7, 95% CI, 0.7-4.7), mean corpuscular hemoglobin (Δ=1.4, 95% CI, 0.5-2.3), and mean corpuscular hemoglobin concentration (Δ=0.5, 95% CI, 0.1-0.9) all improved with supplementation. Mild improvements in erythrocyte indices, growth status, and muscle function occurred independent of hydroxyurea use.

Safety and efficacy of hydroxyurea and eflornithine against most blood parasites Babesia and Theileria

BACKGROUND

The plenteous resistance to and undesirable consequences of the existing antipiroplasmic therapies have emphasized the urgent need for new chemotherapeutics and drug targets for both prophylaxis and chemotherapy. Hydroxyurea (HYD) is an antineoplastic agent with antitrypanosomal activity. Eflornithine (α-difluoro-methyl ornithine, DFMO) is the best choice therapy for the treatment of late-stage Gambian human African trypanosomiasis.

METHODS

In this study, the inhibitory and combination efficacy of HYD and DFMO with existing babesicidal drugs (diminazene aceturate (DA), atovaquone (ATV), and clofazimine (CLF)) deoxyribonucleotide in vitro against the multiplication of Babesia and Theileria. As well as, their chemotherapeutic effects were assessed on B. microti strain that infects rodents. The Cell Counting Kits-8 (CCK-8) test was used to examine their cytotoxicity on human foreskin fibroblast (HFF), mouse embryonic fibroblast (NIH/3T3), and Madin-Darby bovine kidney (MDBK) cells.

FINDINGS

HYD and DFMO suppressed the multiplication of all tested species (B. bigemina, B. bovis, B. caballi, B. divergens, and T. equi) in a dose-related manner. HFF, NIH/3T3, or MDBK cell viability was not influenced by DFMO at 1000 μM, while HYD affected the MDBK cell viability at EC50 value of 887.5±14.4 μM. The in vitro combination treatments of DFMO and HYD with CLF, DA, and ATV exhibited synergistic and additive efficacy toward all tested species. The in vivo experiment revealed that HYD and DFMO oral administration at 100 and 50 mg/kg inhibited B. microti multiplication in mice by 60.1% and 78.2%, respectively. HYD-DA and DFMO-DA combined treatments showed higher chemotherapeutic efficacy than their monotherapies.

CONCLUSION

These results indicate the prospects of HYD and DFMO as drug candidates for piroplasmosis treatment, when combined mainly with DA, ATV, and CLF. Therefore, further studies are needed to combine HYD or DFMO with either ATV or CLF and examine their impact on B. microti infection in mice.

The role of hydroxyurea in decreasing the occurrence of vasso-occulusive crisis in pediatric patients with sickle cell disease at King Saud Medical City in Riyadh, Saudi Arabia

OBJECTIVES

To measure the incidence of vaso-occlusive crises (VOC) and the role of hydroxyurea (HU) in reducing VOC in sickle cell anemia  patients being treated at a large tertiary care setting in Kingdom of Saudi Arabia (KSA). The secondary objective of this study is to observe the gradual improvement in laboratory data (white blood cell [WBC], platelets, mean corpuscular volume [MCV], hemoglobin [Hgb], HgbF) following regular use of HU. Methods: Clinical effectiveness of HU was evaluated in a large pediatric population using a retrospective cohort, non-interventional, pre-post treatment study designed to control disease severity selection bias. The cohort included children with SCA (sickle cell (SS), sickle-beta thalassemia) at King Saud Medical City, Riyadh, KSA, who initiated HU between January 2012 and June 2017. For each patient healthcare utilization, laboratory values, and clinical outcomes were observed for an equal duration of time pre and post hydroxyurea. Results: Out of 416 SCD patients, 128 children with SCD who initiated HU, of them 82 met the eligibility criteria. After initiation of HU, there was significant reduction in both VOC (80%) and length of stay (LOS) (73%). Significant increase in Hgb (13%), MCV (10%), and HgbF (28%) and significant decrease in WBC (28%) was observed. Only the mean platelet count decreased by 3% with a p greater than 0.05. Conclusion: Hydroxyurea treatment significantly decreased episodes of VOC and LOS, it also led to reductions in hospitalizations and significant improvement in complete blood count indices.

Sickling-suppressive effects of chrysin may be associated with sequestration of deoxy-haemoglobin, 2,3-bisphosphoglycerate mutase, alteration of redox homeostasis and functional chemistry of sickle erythrocytes

Sickle cell disease (SCD) is a medical condition caused by mutation in a single nucleotide in the β-globin gene. It is a health problem for people in sub-Saharan Africa, the Middle East and India. Orthodox drugs developed so far for SCD focus largely on symptomatic respite of pain and crisis mitigation. We investigated the antisickling effects of chrysin via modulation of deoxy-haemoglobin, 2,3-bisphosphoglycerate mutase, redox homeostasis and alteration of functional chemistry in human sickle erythrocytes. In silico and in vitro methods were adopted for the studies. Chrysin was docked against deoxy-haemoglobin and 2,3-bisphosphoglycerate mutase, with binding energies (-24.064 and -18.171 kcal/mol) and inhibition constant (K _i) of 0.990 µM and 0.993 µM at their active sites through strong hydrophobic and hydrogen bond interactions. Sickling was induced with 2% metabisulphite at 3 h. Chrysin was able to prevent sickling maximally at 2.5 µg/mL and reversed the same at 12.5 µg/mL, by 66.5% and 69.6%, respectively. Treatment with chrysin significantly (p < 0.05) re-established the integrity of erythrocytes membrane as evident from the observed percentage of haemolysis relative to induced erythrocytes. Chrysin also significantly (p < 0.05) prevented and reversed lipid peroxidation. Similarly, glutathione and catalase levels were observed to significantly (p < 0.05) increase with concomitant significant (p < 0.05) decrease in superoxide dismutase activity relative to untreated. From Fourier-transform infrared results, treatment with chrysin was able to favourably alter the functional chemistry, judging from the shifts and functional groups observed. Sickling-suppressive effects of chrysin may therefore be associated with sequestration of deoxy-haemoglobin, 2,3-bisphosphoglycerate mutase, alteration of redox homeostasis and functional chemistry of sickle erythrocytes.

Allogeneic Hematopoietic Stem Cell Transplantation for Adults with Sickle Cell Disease

Sickle cell disease (SCD) is an inherited red blood cell disorder that leads to substantial morbidity and early mortality. Acute and chronic SCD-related complications increase with older age, and therapies are urgently needed to treat adults. Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative therapy, but has been used less frequently in adults compared to children. This is, in part, due to (1) greater chronic organ damage, limiting tolerability to myeloablative conditioning regimens, (2) a higher rate of HSCT-related complications in adults versus children with SCD, and (3) limited coverage by public and private health insurance. Newer approaches using nonmyeloablative and reduced-intensity conditioning HSCT regimens have demonstrated better safety and tolerability, with high rates of stable engraftment in SCD adults. This review will focus on the impacts of HSCT, using more contemporary approaches to SCD-related complications in adults.

Barriers to the use of hydroxyurea in the management of sickle cell disease in Nigeria

Hydroxyurea (HU) is a well-known Hb F-inducing agent with proven clinical and laboratory efficacy for patients with sickle cell disease. However, concerns about its long-term safety and toxicity have limited its prescription by physicians and acceptability by patients. Thus, this study aims to evaluate clinician's barriers to the use of HU in the management of patients with sickle cell disease in Nigeria. An online survey targeted physicians in pediatrics, hematology, medicine, family medicine and general medical practice managing sickle cell disease in Nigeria. The survey was in four sections: demographic, knowledge and experience with HU, and barriers to the use of HU. Ninety-one (73.0%) of 123 contacts completed the survey. Seventy-three percent and 74.0% of the respondents noted that HU reduced transfusion rates and improved overall quality of life (QOL) of patients, respectively. While the majority of the practitioners (55.6%) see between 10-50 patients per month, most (66.7%) write <5 prescriptions for HU per month. Lack of a national guideline for use of HU, especially in children (52.0%), concern for infertility (52.0%), and safety profile of HU in pregnancy and lactation (48.2%), top the factors considered by the respondents as major barriers to the use of HU. Hydroxyurea is grossly under prescribed in Nigeria, despite that the vast majority of physicians who attend patients with sickle cell disease know about its clinical efficacy. Evidence-based clinical practice guidelines could be explored as a way to standardize practices and improve confidence of practitioners to improve physicians' prescription of HU in the management of sickle cell disease.

Emerging disease-modifying therapies for sickle cell disease

Sickle cell disease afflicts millions of people worldwide and approximately 100,000 Americans. Complications are myriad and arise as a result of complex pathological pathways ‘downstream’ to a point mutation in DNA, and include red blood cell membrane damage, inflammation, chronic hemolytic anemia with episodic vaso-occlusion, ischemia and pain, and ultimately risk of cumulative organ damage with reduced lifespan of affected individuals. The National Heart, Lung, and Blood Institute’s 2014 evidence-based guideline for sickle cell disease management states that additional research is needed before investigational curative therapies will be widely available to most patients with sickle cell disease. To date, sickle cell disease has been cured by hematopoietic stem cell transplantation in approximately 1,000 people, most of whom were children, and significantly ameliorated by gene therapy in a handful of subjects who have only limited follow-up thus far. During a timespan in which over 20 agents were approved for the treatment of cystic fibrosis by the Food and Drug Administration, similar approval was granted for only two drugs for sickle cell disease (hydroxyurea and L-glutamine) despite the higher prevalence of sickle cell disease. This trajectory appears to be changing, as the lack of multimodal agent therapy in sickle cell disease has spurred engagement among many in academia and industry who, in the last decade, have developed new drugs poised to prevent complications and alleviate suffering. Identified therapeutic strategies include fetal hemoglobin induction, inhibition of intracellular HbS polymerization, inhibition of oxidant stress and inflammation, and perturbation of the activation of the endothelium and other blood components (e.g. platelets, white blood cells, coagulation proteins) involved in the pathophysiology of sickle cell disease. In this article, we present a crash-course review of disease-modifying approaches (minus hematopoietic stem cell transplant and gene therapy) for patients with sickle cell disease currently, or recently, tested in clinical trials in the era following approval of hydroxyurea.

Advances in the Development of Antiviral Strategies against Parvovirus B19

Parvovirus B19 (B19V) is a human pathogenic virus, responsible for an ample range of clinical manifestations. Infections are usually mild, self-limiting, and controlled by the development of a specific immune response, but in many cases clinical situations can be more complex and require therapy. Presently available treatments are only supportive, symptomatic, or unspecific, such as administration of intravenous immunoglobulins, and often of limited efficacy. The development of antiviral strategies against B19V should be considered of highest relevance for increasing the available options for more specific and effective therapeutic treatments. This field of research has been explored in recent years, registering some achievements as well as interesting future perspectives. In addition to immunoglobulins, some compounds have been shown to possess inhibitory activity against B19V. Hydroxyurea is an antiproliferative drug used in the treatment of sickle-cell disease that also possesses inhibitory activity against B19V. The nucleotide analogues Cidofovir and its lipid conjugate Brincidofovir are broad-range antivirals mostly active against dsDNA viruses, which showed an antiviral activity also against B19V. Newly synthesized coumarin derivatives offer possibilities for the development of molecules with antiviral activity. Identification of some flavonoid molecules, with direct inhibitory activity against the viral non-structural (NS) protein, indicates a possible line of development for direct antiviral agents. Continuing research in the field, leading to better knowledge of the viral lifecycle and a precise understanding of virus–cell interactions, will offer novel opportunities for developing more efficient, targeted antiviral agents, which can be translated into available therapeutic options.

Muscle dysfunction is associated with poorer health-related quality of life in adults with sickle cell anaemia

BACKGROUND

It is known that episodes of microvascular obstruction and oxidative stress in sickle cell anaemia (SCA) can damage muscle tissue. As a consequence, deterioration in muscle function may potentially contribute to poor health-related quality of life (HRQoL) in subjects with SCA, particularly those who do not use long-term treatment.

OBJECTIVES

To evaluate muscle function in adults with SCA, to study the correlations between muscle function and HRQoL and to analyse the impact of hydroxyurea treatment.

METHODS

Twenty-two adults with SCA and 20 matched controls were subjected to Short Form-36 (SF-36), respiratory muscle strength measurement, isometric hand grip strength (iHGS) measurement and knee isokinetic dynamometry.

RESULTS

In relation to their healthy peers, adults with SCA had lower SF-36 scores, respiratory muscle strength and iHGS. Regarding the isokinetic test, adults with SCA showed lower values, especially in the variables measured in flexion and with an angular velocity of 240∘/s. There was a significant correlation between the peak torque (PT) at 240∘/s and the physical component summary (SF-36PCS) in both extension (r= 0.77; p< 0.001) and flexion (r= 0.82; p< 0.001). Significant correlations were also observed between the agonist/antagonist ratio at 240∘/s and the SF-36PCS (r= 0.50; p< 0.001). The use of hydroxyurea led to higher scores on the SF-36 and higher values in knee isokinetic dynamometry.

CONCLUSIONS

Adults with SCA have muscle dysfunction, especially with regard to endurance of the knee flexor muscles. In these patients, there is a significant association between muscle function and HRQoL. Moreover, the use of hydroxyurea is associated with better HRQoL and less muscle dysfunction.

Annual stroke incidence in Nigerian children with sickle cell disease and elevated TCD velocities treated with hydroxyurea

BACKGROUND

Elevated transcranial Doppler (TCD) velocities accurately predict stroke risk in children with sickle cell disease (SCD). Chronic blood transfusion, the gold standard for primary stroke prevention, is faced with numerous challenges in Africa. Hydroxyurea (HU) has been shown to reduce elevated TCD velocities in children with SCD.

AIM

To determine the effectiveness of HU in reducing the risk of primary stroke in a cohort of Nigerian children with SCD and elevated velocities treated with HU.

METHODS

Children with SCD and TCD velocities ≥170 cm/sec treated with HU were prospectively followed with 3-monthly TCD and neurological evaluations for ≥12 months to determine the incidence of primary stroke.

RESULTS

One hundred and four children, 53 males, and 51 females were enrolled into the study. Their ages ranged from 2 to 16 years with a mean of 6 years. At first TCD examination, velocities ranged from 173 to 260 cm/sec with conditional and abnormal risk velocities in 60 (57.7%) and 44 (42.3%) children, respectively. Follow up ranged from 1 to 8 years with a mean of 3.6 years. Mean TCD velocities showed a significant decline from 198.2 (standard deviation [SD] = 15.6) cm/sec to 169.3 (SD = 21.4) cm/sec (P < 0.001). One stroke event occurred in the cohort, giving a stroke incidence of 0.27/100 person years.

CONCLUSION

HU significantly reduces TCD velocities in Nigerian children with SCD and elevated TCD velocities, with a corresponding reduction in the incidence of primary stroke. HU may represent a potential alternative for primary stroke prevention in low and middle income countries where the burden of SCD resides.

Sickle Cell Anemia: A review on the most severe form of Sickle Cell Disease

Sickle cell disease (SCD) is a group of hereditary disorders caused by a single point mutation in the β-globin gene. This mutation results in the formation of a mutated hemoglobin S (HbS) and the consequent sickle phenotype of erythrocytes. SCD is common in regions of malaria endemicity. However, changes in population dynamics enabled the movement of the mutated gene to other areas such as North America and Europe. Sickle cell anemia (SCA) is the most severe form of SCD and affects millions of people around the globe. The clinical manifestations of SCA arise primarily from the polymerization of deoxygenated hemoglobin S (deoxyHbS) leading to vascular occlusion and hemolytic anemia. Clinical complications of the disease are derived from deoxyHbS polymerization, but there are several therapeutic strategies to reduce the severity of the symptoms. Gene therapy has arisen as a new therapeutic approach aimed to cure rather than to treat the symptomatology of SCA by targeting the altered β-globin gene for gene correction.

Therapeutic strategies for sickle cell disease: towards a multi-agent approach

For over 100 years, clinicians and scientists have been unravelling the consequences of the A to T substitution in the β-globin gene that produces haemoglobin S, which leads to the systemic manifestations of sickle cell disease (SCD), including vaso-occlusion, anaemia, haemolysis, organ injury and pain. However, despite growing understanding of the mechanisms of haemoglobin S polymerization and its effects on red blood cells, only two therapies for SCD - hydroxyurea and L-glutamine - are approved by the US Food and Drug Administration. Moreover, these treatment options do not fully address the manifestations of SCD, which arise from a complex network of interdependent pathophysiological processes. In this article, we review efforts to develop new drugs targeting these processes, including agents that reactivate fetal haemoglobin, anti-sickling agents, anti-adhesion agents, modulators of ischaemia-reperfusion and oxidative stress, agents that counteract free haemoglobin and haem, anti-inflammatory agents, anti-thrombotic agents and anti-platelet agents. We also discuss gene therapy, which holds promise of a cure, although its widespread application is currently limited by technical challenges and the expense of treatment. We thus propose that developing systems-oriented multi-agent strategies on the basis of SCD pathophysiology is needed to improve the quality of life and survival of people with SCD.

Development of a Hydroxyurea Decision Aid for Parents of Children With Sickle Cell Anemia

National evidence-based guidelines recommend offering hydroxyurea to patients with sickle cell anemia 9 months of age and older using shared decision making, but offer no strategies to aid implementation. We developed a hydroxyurea multicomponent decision aid via a needs assessment, clinic observations, and iterative feedback to address parent decision needs and promote a discussion between clinicians and parents. A total of 75 parents and 28 clinicians participated across all phases. The decision aid was rated as useful. Hydroxyurea knowledge improved and decisional conflict decreased supporting the potential for use to facilitate shared decision making in pediatric sickle cell anemia.

An Animal Model for Assessing the Effects of Hydroxyurea Exposure Suggests That the Administration of This Agent to Pregnant Women and Young Infants May Not Be as Safe as We Thought

The cytostatic agent hydroxyurea (HU) has proven to be beneficial for a variety of conditions in the disciplines of oncology, hematology, infectious disease and dermatology. It disrupts the S phase of the cell cycle by inhibiting the ribonucleotide reductase enzyme, thus blocking the transformation of ribonucleotides into deoxyribonucleotides, a rate limiting step in DNA synthesis. HU is listed as an essential medicine by the World Health Organization. Several studies have indicated that HU is well tolerated and safe in pregnant women and very young pediatric patients. To our knowledge, only a few controlled studies on the adverse effects of HU therapy have been done in humans. Despite this, the prevalence of central nervous system abnormalities, including ischemic lesions and stenosis have been reported. This review will summarize and present the effects of HU exposure on the prenatal and perinatal development of the rat cerebellar cortex and deep cerebellar nuclei neurons. Our results call for the necessity to better understand HU effects and define the administration of this drug to gestating women and young pediatric patients.

Development and Characterization of a Model for Inducing Fetal Hemoglobin Production in Cynomolgus Macaques (Macaca fasicularis)

Hydroxyurea induces production of fetal hemoglobin (HbF), a tetramer of α and γ globin proteins and corresponding heme molecules, normally found in less than 1% of adult RBC. Increases in circulating HbF are correlated with clinical improvement of patients with hemoglobinopathies, and hydroxyurea, as a daily medication, is the standard treatment for sickle cell anemia. Although olive baboons (Papio anubis) are considered a key model species for HbF induction, cynomolgus macaques (Macaca fasicularis) are another species that conserves the ability to produce HbF into maturity. In this study, moderate anemia was experimentally induced in cynomolgus macaques by phlebotomy, to stimulate accelerated erythropoiesis and HbF production. In contrast to previous studies, vascular access ports were implanted for phlebotomy of conscious monkeys, followed by fluid replacement. As total Hgb levels dropped, reticulocyte counts and the percentage of HbF-expressing cells increased. Once total Hgb levels declined to less than 8 g/dL, 2 courses of oral hydroxyurea (once daily for 5 d) were completed, with a 9-d interval between courses. After hydroxyurea dosing, the percentage of HbF-expressing cells and total HbF were increased significantly. In addition, a significant but transient decrease in reticulocyte count and a transient increase in MCV occurred, replicating the characteristic response of patients receiving hydroxyurea. Daily clinical observations revealed no serious health issues or decreases in food consumption or activity levels. Methods were established for assessing the patency of vascular access ports. This study details a new protocol for the safe and routine induction of moderate anemia in cynomolgus macaques and validates its use in the investigation of novel pharmacologic entities to induce the production of HbF.

Treatment Options for Sickle Cell Disease

Sickle cell disease (SCD) complications begin with the polymerization of sickle hemoglobin (HbS). Thus, SCD therapies are focused on preventing HbS production or reducing the circulating amount of HbS. Hydroxyurea treatment has become more widespread, whereas the number of evidence-based indications for erythrocyte transfusion is small. Hematopoietic stem cell transplant is a curative option for SCD but less than 25% of patients have a suitable donor. This article focuses on supportive and preventive care improvements and the benefits of hydroxyurea. Indications for erythrocyte transfusion, hematopoietic stem cell transplant, and gene therapy trials are also summarized.

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.

Sickle cell disease

Sickle cell disease (SCD) is a group of inherited disorders caused by mutations in HBB, which encodes haemoglobin subunit β. The incidence is estimated to be between 300,000 and 400,000 neonates globally each year, the majority in sub-Saharan Africa. Haemoglobin molecules that include mutant sickle β-globin subunits can polymerize; erythrocytes that contain mostly haemoglobin polymers assume a sickled form and are prone to haemolysis. Other pathophysiological mechanisms that contribute to the SCD phenotype are vaso-occlusion and activation of the immune system. SCD is characterized by a remarkable phenotypic complexity. Common acute complications are acute pain events, acute chest syndrome and stroke; chronic complications (including chronic kidney disease) can damage all organs. Hydroxycarbamide, blood transfusions and haematopoietic stem cell transplantation can reduce the severity of the disease. Early diagnosis is crucial to improve survival, and universal newborn screening programmes have been implemented in some countries but are challenging in low-income, high-burden settings.

Leukemoid Reaction in Infant Pertussis: Is There a Place for Hydroxyurea? A Case Report

A 73-days old infant of 34 weeks' gestation was hospitalized with a co-infection of respiratory syncytial virus (RSV) and Bordetella pertussis (BP). She required invasive ventilation for 9 days in the context of malignant pertussis with persistent hypoxemia and hypercapnia secondary to a leukemoid reaction. Despite an increase of white blood cell (WBC) count up to 70 G/L and ensuing pulmonary hypertension, no hemodynamic compromise occurred. Without clear indication for leukapheresis nor exchange transfusion, an off-label treatment with hydroxyurea was given for 5 days with gradual decrease of WBC count, without any complication and hospital discharge on day 29. To our knowledge, no effective therapy for malignant pertussis has been described in the literature and complications are frequent with leukoreduction procedures. We discuss an alternative to invasive procedures in young infants to fulfill the need to decrease rapidly leukocyte counts in a leukemoid reaction associated with Bordetella pertussis infection. To our knowledge, hydroxyurea has never been used in malignant pertussis but is a well-known medication for oncologic and hematologic diseases such as acute myeloid leukemia or sickle cell anemia. Its effects in this setting are not well understood but the positive outcome in our patient supports the need for further studies.

Real-life experience with hydroxyurea in sickle cell disease: A multicenter study in a cohort of patients with heterogeneous descent

We conducted the first nation-wide cohort study of sickle cell disease (SCD) in Italy, a Southern European country exposed to intense recent flux migration from endemic areas for SCD. We evaluate the impact of hydroxyurea on a total of 652 pediatric and adult patients from 33 Reference Centers for SCD (mean age 24.5±15years, 51.4% males). Hydroxyurea median treatment duration was 7years (range: <1year to 29years) at a mean therapeutic dose of 18±4.7mg/kg/day. Hydroxyurea was associated with a significant increase in mean total and fetal hemoglobin and a significant decrease in mean hemoglobin S, white blood and platelet counts, and lactate dehydrogenase levels. Hydroxyurea was associated with a significant reduction in the incidence of acute chest syndrome (-29.3%, p<0.001), vaso-occlusive crisis (-34.1%, p<0.001), hospitalization (-53.2%, p<0.001), and bone necrosis (-6.9%, p<0.001). New silent cerebral infarction (SCI) occurred during treatment (+42.4%, p<0.001) but not stroke (+0.5%, p=0.572). These observations were generally consistent upon stratification for age, descent (Caucasian or African), genotype (βS/βS, βS/β⁰ or βS/β⁺) and duration of treatment (< or ≥10years). There were no new safety concerns observed compared to those commonly reported in the literature. Our study, conducted on a large population of patients with different descent and compound state supports the benefits of hydroxyurea therapy as a treatment option. Registered at clinical trials.gov (NCT02709681).

Skeletal and myocardial microvascular blood flow in hydroxycarbamide-treated patients with sickle cell disease

In sickle cell disease (SCD), abnormal microvascular function combined with chronic anaemia predisposes patients to perfusion-demand mismatch. We hypothesized that skeletal muscle and myocardial perfusion, normalized to the degree of anaemia, is reduced at basal-state compared to controls, and that this defect is ameliorated by hydroxycarbamide (HC; also termed hydroxyurea) therapy. Twenty-one SCD patients, of whom 15 were treated with HC, and 27 controls underwent contrast-enhanced ultrasound (CEU) perfusion imaging of the forearm as well as the myocardium. HC treatment was associated with lower white cell and reticulocyte counts, and higher fetal haemoglobin and total haemoglobin levels. When corrected for the degree of anaemia in SCD patients, skeletal flow in HC-treated patients was significantly higher than in untreated SCD patients (217·7 ± 125·4 vs. 85·9 ± 40·2, P = 0·018). Similarly, when normalized for both anaemia and increased myocardial work, resting myocardial perfusion was also significantly higher in HC-treated patients compared with untreated SCD patients (0·53 ± 0·47 vs. 0·13 ± 0·07, P = 0·028). Haemoglobin F (HbF) levels correlated with skeletal muscle microvascular flow (r = 0·55, P = 0·01). In conclusion, patients with SCD not on HC therapy have resting flow deficits in both skeletal muscle and myocardial flow. HC therapy normalizes flow and there is a direct correlation with HbF levels. Clinical trial registration ClinicalTrials.gov Identifier: NCT01602809; https://clinicaltrials.gov/ct2/show/NCT01602809?term=sACHDEV&rank=9.

Hypoxia-enhanced adhesion of red blood cells in microscale flow

OBJECTIVES

The advancement of microfluidic technology has facilitated the simulation of physiological conditions of the microcirculation, such as oxygen tension, fluid flow, and shear stress in these devices. Here, we present a micro-gas exchanger integrated with microfluidics to study RBC adhesion under hypoxic flow conditions mimicking postcapillary venules.

METHODS

We simulated a range of physiological conditions and explored RBC adhesion to endothelial or subendothelial components (FN or LN). Blood samples were injected into microchannels at normoxic or hypoxic physiological flow conditions. Quantitative evaluation of RBC adhesion was performed on 35 subjects with homozygous SCD.

RESULTS

Significant heterogeneity in RBC adherence response to hypoxia was seen among SCD patients. RBCs from a HEA population showed a significantly greater increase in adhesion compared to RBCs from a HNA population, for both FN and LN.

CONCLUSIONS

The approach presented here enabled the control of oxygen tension in blood during microscale flow and the quantification of RBC adhesion in a cost-efficient and patient-specific manner. We identified a unique patient population in which RBCs showed enhanced adhesion in hypoxia in vitro. Clinical correlates suggest a more severe clinical phenotype in this subgroup.

Clinical Course of Two Children with Unstable Hemoglobins: The Effect of Hydroxyurea Therapy

Case reports on the effect of hydroxyurea (HU) therapy for unstable hemoglobins (Hbs) are sparse; only three adult cases have been reported. We report for the first time on the effect of HU therapy in children carrying unstable Hbs. The first case concerns a female child with a familial history of chronic hemolytic anemia. She was diagnosed with Hb Volga (HBB: c.83C>A) at the age of 7 months. At age 6, treatment options were reconsidered due to increasing fatigue and decreasing Hb concentration. The second case also concerns a female child with chronic hemolytic anemia and icterus since the age of 5. She was diagnosed with Hb Köln (HBB: c.295G>A) at the age of 9. At age 10, treatment options were reconsidered due to decreased general condition and poor school performance. Both children were started on HU therapy. The child with Hb Volga showed reduced clinical symptoms and increased average Hb concentrations. She has been on HU therapy for over 7 years at preparation of this manuscript. The child with Hb Köln showed decreasing Hb concentrations upon start of therapy; clinical symptoms did not improve. Therapy was discontinued after 3½ months. The Hb Volga case report suggests that HU therapy could improve clinical symptoms in some patients with unstable Hbs. Based on these and previously published cases, it was speculated that response can be predicted by the percentage of Hb F and reticulocyte counts.

Developmental Injury to the Cerebellar Cortex Following Hydroxyurea Treatment in Early Postnatal Life: An Immunohistochemical and Electron Microscopic Study

Postnatal development of the cerebellar cortex was studied in rats administered with a single dose (2 mg/g) of the cytotoxic agent hydroxyurea (HU) on postnatal day (P) 9 and collected at appropriate times ranging from 6 h to 45 days. Quantification of several parameters such as the density of pyknotic, mitotic, BrdU-positive, and vimentin-stained cells revealed that HU compromises the survival of the external granular layer (EGL) cells. Moreover, vimentin immunocytochemistry revealed overexpression and thicker immunoreactive glial processes in HU-treated rats. On the other hand, we also show that HU leads to the activation of apoptotic cellular events, resulting in a substantial number of dying EGL cells, as revealed by TUNEL staining and at the electron microscope level. Additionally, we quantified several features of the cerebellar cortex of rats exposed to HU in early postnatal life and collected in adulthood. Data analysis indicated that the analyzed parameters were less pronounced in rats administered with this agent. Moreover, we observed several alterations in the cerebellar cortex cytoarchitecture of rats injected with HU. Anomalies included ectopic placement of Purkinje cells and abnormities in the dendritic arbor of these macroneurons. Ectopic granule cells were also found in the molecular layer. These findings provide a clue for investigating the mechanisms of HU-induced toxicity during the development of the central nervous system. Our results also suggest that it is essential to avoid underestimating the adverse effects of this hydroxylated analog of urea when administered during early postnatal life.

Demands and challenges for patients with sickle-cell disease requiring hematopoietic stem cell transplantation in Saudi Arabia

Allogeneic HSCT is the only curative treatment for SCD. In this study, we estimated the number of Saudi patients with SCD who are candidates for HSCT. We used the presence of overt stroke, recurrent ACS, and frequent severe pain crisis as indications for HSCT. We calculated the frequencies of these complications among a Saudi SCD cohort of 376 patients with SCD, 250 from SW and 126 from Eastern (E) provinces. We found that 59 (23.6%) of SW patients were transplant candidates compared to 22 (17.4%) from E province. It is estimated that about 61 000 patients with SCD live in Saudi Arabia. Thus, the projected number of Saudi patients with SCD who are candidates for HSCT is 10 536 patients. Of those, 2148 are children. The burden of SCD on HSCT centers in Saudi Arabia is substantial and is difficult currently to meet the demand. We recommend recruiting/training more transplant physicians and nurses, expand current capacity of centers if feasible, and open new transplant centers to make HSCT a practical therapeutic option for patients with severe SCD in Saudi Arabia.

Endothelin receptor antagonists in sickle cell disease: A promising new therapeutic approach

Sickle cell disease (SCD) is a genetic hematologic disorder that is characterized by a variety of potentially life threatening acute and chronic complications. Currently, hydroxyurea is the only clinically approved pharmacological therapy for the treatment of SCD, and the continued prevalence of severe disease complications underscores the desperate need for the development of new therapeutic agents. Central features of the sickle cell disease milieu, including hypoxia, oxidative stress, and thrombosis, are established enhancers of endothelin-1 (ET-1) synthesis. This conceptual connection between ET-1 and SCD was confirmed by multiple studies that demonstrated markedly elevated plasma and urinary levels of ET-1 in SCD patients. Direct evidence for the involvement of ET-1 signaling in the development of SCD pathologies has come from studies using endothelin receptor antagonists in SCD mice. This review summarizes recent studies that have implicated ET-1 signaling as a mechanistic contributor to renal, vascular, pulmonary, and nociceptive complications of sickle cell disease and discusses the potential for the use of ET receptor antagonists in the treatment of SCD.

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).

Minireview: Multiomic candidate biomarkers for clinical manifestations of sickle cell severity: Early steps to precision medicine

In this review, we provide a description of those candidate biomarkers which have been demonstrated by multiple-omics approaches to vary in correlation with specific clinical manifestations of sickle cell severity. We believe that future clinical analyses of severity phenotype will require a multiomic analysis, or an omics stack approach, which includes integrated interactomics. It will also require the analysis of big data sets. These candidate biomarkers, whether they are individual or panels of functionally linked markers, will require future validation in large prospective and retrospective clinical studies. Once validated, the hope is that informative biomarkers will be used for the identification of individuals most likely to experience severe complications, and thereby be applied for the design of patient-specific therapeutic approaches and response to treatment. This would be the beginning of precision medicine for sickle cell disease.