Hydroxyurea In Sickle Cell Anemia Research Articles

Towards genomic medicine: a tailored next-generation sequencing panel for hydroxyurea pharmacogenomics in Tanzania

BackgroundPharmacogenomics of hydroxyurea is an important aspect in the management of sickle cell disease (SCD), especially in the era of genomic medicine. Genetic variations in loci associated with HbF induction and drug metabolism are prime targets for hydroxyurea (HU) pharmacogenomics, as these can significantly impact the therapeutic efficacy and safety of HU in SCD patients.MethodsThis study involved designing of a custom panel targeting BCL11A, ARG2, HBB, HBG1, WAC, HBG2, HAO2, MYB, SAR1A, KLF10, CYP2C9, CYP2E1 and NOS1 as potential HU pharmacogenomics targets. These genes were selected based on their known roles in HbF induction and HU metabolism. The panel was designed using the Illumina Design Studio (Illumina, San Diego, CA, USA) and achieved a total coverage of 96% of all genomic targets over a span of 51.6 kilobases (kb). This custom panel was then sequenced using the Illumina MiSeq platform to ensure high coverage and accuracy.ResultsWe are reporting a successfully designed Illumina (MiSeq) HU pharmacogenomics custom panel encompassing 51.6 kilobases. The designed panel achieved greater than 1000x amplicon coverage which is sufficient for genomic analysis.ConclusionsThis study provides a valuable tool for research in HU pharmacogenomics, especially in Africa where SCD is highly prevalent, and personalized medicine approaches are crucial for improving patient outcomes. The custom-designed Illumina (MiSeq) panel, with its extensive coverage and high sequencing depth, provides a robust platform for studying genetic variations associated with HU response. This panel can contribute to the development of tailored therapeutic strategies, ultimately enhancing the management of SCD through more effective and safer use of hydroxyurea.

Hydroxyurea in Sickle Cell Disease and Invasive Bacterial Infections: A Case-Control Study.

Hydroxyurea decreases painful events among children with sickle cell disease (SCD) but could increase the risk of infections in treated patients through leucopenia. We performed a case-control study, comparing hydroxyurea treatment for SCD in cases with an invasive bacterial infection and in controls without infection. No difference was found.

Knowledge and Perceptions about Curative Therapies for Sickle Cell Disease and Hydroxyurea Among Caregivers and Patients at a Large Tertiary Care Center: A Survey Study

Background: Sickle Cell Disease (SCD) affects approximately 100,000 individuals in the United States. Patients require regular follow-up and monitoring to prevent serious complications. Even with rigorous monitoring, health outcomes can be poor due to pain-seeking stigma and other social determinants of health, namely racial, social, and economic disparities. According to the National Assessment of Health Literacy published in 2006, 36% of adults have limited health literacy in the United States. Among SCD populations, disease-specific knowledge can play a vital role in improving pain control and access to appropriate maintenance therapies. Aims:The purpose of this study is to investigate the knowledge and perceptions of patients with SCD and their caregivers attending The Valerie Fund Pediatric Hematology-Oncology Center at the Children's Hospital of New Jersey in Newark, NJ regarding their disease, complications, genetic impact, general anticipated course of treatment or natural history of disease. Hydroxyurea (HU) and curative therapies include bone marrow transplant (BMT) and gene therapy (GT). Methods: We surveyed 85 participants, accounting for 79 patients as some surveys were completed by each the patient and caregiver. Sixty-six (83.5%) participants were caregivers and 13 (16.5%) were children with sickle cell disease between 12- and 20-years-old. Most patients identified as black, African, or African American (76; 96.2%) with 2 (2.5%) Hispanic patients, and 1 (1.3%) white patient. Forty-three patients (54.4%) were female and 36 (45.6%) were male. The average age of the patients was 10.9 years with a standard deviation of 5.7 years. More than half of patients were HbSS genotype (51; 64.6%). Remaining genotypes were HbSC (21; 26.6%), HbS-β 0-thalassemia (5; 6.3%), and HbS-β +-thalassemia (2; 2.5%). Forty-six (58.2%) of patients had received HU and 33 (41.8%) had not. Results: When assessing background knowledge of sickle cell and heritable risk, most participants could correctly identify the patient's sickle cell genotype (74; 87.1%) and most caregivers could correctly identify their own genotype (49; 74.2%). However, many caregivers exhibited limited understanding of genetic risk with only 18 (27.2%) correctly identifying the one in four chance of having a subsequent child with SCD when both parents are carriers. The results revealed participants could not distinguish between treatment for SCD and sickle cell trait; few participants correctly identified that sickle cell trait is not an indication for treatment with HU (8; 10.1%), BMT (4; 5.1%) or GT (6; 7.6%). Baseline knowledge about BMT and GT was limited. Only 27 (34.1%) participants correctly identified that BMT is indicated for treating patients with HbSS or HbS-b 0-thalassemia, and only 9 (11.4%) participants correctly identified this treatment population for GT. BMT knowledge was slightly greater than GT knowledge, namely that 60.1% (48) correctly identified the benefits of BMT for SCD patients, including decreased pain, decreased need for pain medication, decreased length of hospital stay, and cure, and that either bone marrow, stem cells, or blood could be transplanted materials. Most patients did not correctly identify these benefits of GT (55; 70%), nor could they identify the source of blood or stem cells for GT (65; 82.3%). The ability to correctly identify the benefits of HU for sickle cell disease (48; 60.8%) was positively associated with the ability to correctly identify the benefits of BMT (p-value 0.0091) and GT (p-value 0.0438) using Fisher's exact test with 95% confidence interval. Conclusion: These results suggest that dedicated teaching about HU, a common treatment for SCD, can result in greater patient knowledge about newer and curative treatment options of bone marrow transplant and gene therapy. These findings underscore the necessity of implementation of comprehensive patient teaching that is inclusive of population education levels, literacy rates, health literacy rates, and other cultural and societal factors.

Cost-Effectiveness of Hydroxyurea for Sickle Cell Anemia in a Low-Income African Setting: A Model-Based Evaluation of Two Dosing Regimens.

The disease burden of sickle cell anemia (SCA) in sub-Saharan African (SSA) countries is substantial, with many children dying without an established diagnosis or proper treatment. The global burden of SCA is increasing each year, making therapeutic intervention a high priority. Hydroxyurea is the only disease-modifying therapy with proven feasibility and efficacy suitable for SSA; however, no one has quantified the health economic implications of its use. Therefore, from the perspective of the health care provider, we estimated the incremental cost-effectiveness of hydroxyurea as a fixed-dose regimen or maximumtolerated dose (MTD) regimen, versus SCA care without hydroxyurea. We estimated the cost of providing outpatient treatment at a pediatric sickle cell clinic in Kampala, Uganda. These estimates were used in a discrete-event simulation model to project mean costs (2021 US$), disability-adjusted life years (DALYs), and consumption of blood products per patient (450mL units), for patients between 9months and 18years of age. We calculated cost-effectiveness as the ratio of incremental costs over incremental DALYs averted, discounted at 3% annually. To test the robustness of our findings, and the impact of uncertainty, we conducted probabilistic and one-way sensitivity analyses, scenario analysis, and price threshold analyses. Hydroxyurea treatment averted an expected 1.37 DALYs and saved US$ 191 per patient if administered at the MTD, compared with SCA care without hydroxyurea. In comparison, hydroxyurea at a fixed dose averted 0.80 DALYs per patient at an incremental cost of US$ 2. The MTD strategy saved 11.2 (95% CI 11.1-11.4) units of blood per patient, compared with 9.1 (95% CI 9.0-9.2) units of blood per patient at the fixed-dose alternative. Hydroxyurea at MTD is likely to improve quality of life and reduce the consumption of blood products for children with SCA living in Uganda. Compared with a fixed dose regimen, treatment dosing at MTD is likely to be a cost-effective treatment for SCA, using realistic ranges of hydroxyurea costs that are relevant across SSA. Compared with no use of the drug, hydroxyurea could lead to substantial net savings per patient, while reducing the disease morbidity and mortality and increasing quality of life.

Simultaneous adjunctive treatment of malaria and its coevolved genetic disorder sickle cell anemia

AbstractEffective treatments for genetic disorders that coevolved with pathogens require simultaneous betterment of both conditions. Hydroxyurea (HU) offers safe and efficacious treatment for sickle cell anemia (SCA) by reducing clinical complications, transfusions, and death rates. Despite concerns that the HU treatment for SCA would increase infection risk by the human malaria Plasmodium falciparum, (the genetic driver of the sickle mutation), HU instead reduced clinical malaria. We used physiologically relevant drug exposures that mimic in vivo pharmacokinetics in humans. Under these conditions, we showed that HU and other ribonucleotide reductase (RNR) inhibitors have significant, intrinsic killing activity in vitro against schizont stages of P falciparum in both normal and sickle red blood cells. Long-term in vitro selection with HU increased the expression of Pfrnr genes but showed a low risk of eliciting stably resistant parasites or compromising the potency of current antimalarial drugs. Additive activity devoid of antagonism by HU was observed with a wide spectrum of commonly used antimalarial treatments. These data endorse broad, safe, and long-term use of HU for SCA in malaria-endemic countries and provide a novel biological model for the treatment of a genetic disorder with simultaneous, adjunct therapy of a life-threatening infection needed in a global health setting.

Loss of Cyb5R3 Function Silences Fetal Hemoglobin and Hematocrit Responses to Hydroxyurea in Patients with Sickle Cell Anemia

BACKGROUND: Hydroxyurea (HU) is the first FDA-approved and most widely prescribed drug for sickle cell (SS) patients due to its beneficial effects (decreased Hb polymerization, pain crises and hospitalization) and relative safety profile. While the clinical benefits of HU have been found to associate with increased nitric oxide (NO) and fetal hemoglobin (HbF) in most SS patients, there has been considerable interpatient variability in HbF response to the drug. From this standpoint, HU is imperfectly understood mechanistically. Cytochrome b5 reductase 3 (Cyb5R3), also known as methemoglobin reductase, is an enzyme known to modulate redox signaling in erythrocytes and vascular cells by catalyzing one electron transfer reactions using reduced nicotinamide adenine dinucleotide (NADH) as an electron donor. Functionally, membrane-associated CYB5R3 exerts antioxidant properties by modulating heme iron reduction, plasma membrane coenzyme Q reduction, elongation and unsaturation of fatty acids, cholesterol biosynthesis and drug metabolism, while the soluble form of CYB5R3 reduces red blood cell methemoglobin. Unremitting oxidation of the soluble guanylate cyclase (sGC) heme iron in the absence of sufficient Cyb5R3 activity in vascular smooth muscle has been shown to explain some NO resistance that characterizes pulmonary arterial hypertension and other vasculopathy associated with SCD. More than 40 variants of Cyb5R3 have been identified. Of particular interest is a Cyb5R3 variant (T117S) that contains a threonine to serine substitution in the flavoprotein, which lessens the reductase's activity by roughly 50% compared to wild-type. This variant occurs with high frequency (0.23 minor allele) in persons of African ancestry but is rare (<1%) in all other races. Nothing is known about the role of Cyb5R3 in the anemia of sickle cell disease. We hypothesized that Cyb5R3 may act as a modifier of HbF induction by HU in sickle cell anemia. METHODS: Male and female SS patients (n=633, 12-70 years of age) from the Treatment of Pulmonary Hypertension and Sickle Cell Disease with Sildenafil Therapy (walk-PHaSST) trial were recruited for genetic analysis (University of Pittsburgh IRB Protocol Study 19060255). Genotyping of rs1800457 (T117S SNP) was performed using Taqman genotyping assay. One-way ANOVA and Holms Sidak were used for multiple comparisons of HbF levels by Cyb5R3 genotype and HU treatment status. Intrapatient correlation analyses of HbF and hematocrit (HCT) were conducted using Pearsons r. RESULTS: Comparisons of HbF levels by Cyb5R3 genotype (CC, wild-type; CG, heterozygous wild-type and T117S; GG, homozygous T117S) and HU treatment status (treated vs. untreated) at time of study enrollment (baseline) show that HU is a less potent HbF inducer in the GG group (4.32 mean diff, P=0.344) versus the CC and CG patient groups (CC: 6.027 mean diff, P<0.0001 and CG: 6.914 mean diff, P<0.0001). Correlation analyses showed that as HbF levels increased among HU-untreated patients, the trend was for HCT to decrease. This was true for all SS patients, irrespective of Cyb5R3 genotype (CC: r = -0.336, P<0.0001, n=320; CG: r = -0.437 P<0.0001, n=120; GG: r = -0.253, P=0.136, n=36). However, with HU therapy, the inverse relationship between HbF and HCT was less negative in SS patients carrying at least one copy of the wild-type Cyb5R3 gene (CC or CG). In these individuals, increasing levels of HbF (up to 10%) correlated with positive gains in HCT at HbF greater than 5-6% (CC: r = -0.161, P=0.097, n=107) and 6-7% (CG: r = -0.186, P=0.25, n=40). In patients homozygous for T117S, HCT continued trending downward as HbF increased (GG: r = -0.419, P=0.228, n=10). These data indicate that the positive relationship between HbF and HCT is subject to uncoupling by loss of Cyb5R3 function. In vitro studies with human erythroleukemic K562 cells reveal loss of gamma globin induction by HU treatment when wild-type Cyb5R3 is knocked down by siRNA, indicating a requirement for Cyb5R3 in HU-stimulated HbF induction. SUMMARY andCONCLUSION: Loss of Cyb5R3 activity negatively impacts HbF and HCT in HU treated SS patients. We conclude that the T117S variant may be a useful marker for predicting which SS patients will incur beneficial HbF and HCT responses to HU, thereby improving clinical decision-making about best drug choices for preventing HbS polymerization and treating anemia in SS patients.

Patients with Sickle Cell Disease Treated with Hidroxiurea Have Higher Expression of PD-L1 in Monocytes

Background: Inflammation plays a key role in pathophysiology of sickle cell disease (SCD). Monocytes are important mediator cells in the inflammation pathway. Despite some evidence that monocytes are more activated in SCD and can trigger vaso-occlusion, there is a remarkable lack of knowledge about how monocytes behave in patients with SCD and whether they are modulated by different treatments. Objective: To assess possible changes in monocyte maturation and protein expression among sickle cell disease patients in different treatment modalities and compare them to healthy subjects. Methods: 25 patients with SCD followed at the outpatient service of the Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo and 3 healthy controls were included. The inclusion criteria were: patients with sickle cell anemia (HbSS), over 18 years of age, without acute complications in the prior three months. Pregnancy was an exclusion criteria. Patients were divided in three groups: treatment with Hydroxyurea (HU) (n=10) using the same dose for at least three months; chronic exchange transfusion (n=9) (TP); and no specific treatment (NST) (n=6). We collected 3-5 ml of blood and performed peripheral blood mononuclear cells (PBMC) separation. Monocytes were analyzed by flow cytometry (Dx Flex, Beckman Coulter), using CD14 and CD16 as markers of subpopulations of monocytes as classical (CD14+/CD16-), intermediate (CD14+/CD16+) and non-classical (CD14-/CD16+). We also assessed the expression of CD 86 (a co-stimulation chemokine receptor), CD 163 (receptor for the conjugate hemoglobin-haptoglobin) and PD-L1 (an inhibitor receptor). Comparison between groups were made using ANOVA and Tukey test. Results: Gender distribution yielded no significant difference. Age varied as shown: HU 30 ± 8y, TP 37 ± 9y, NST 35 ± 11y and 42 ± 19y for the controls. The mean of total leukocytes and monocytes were, respectively: 8,816 ± 2,133/mm³ and 900 ± 563/mm³ (HU), 11,487 ± 3,813/mm³ and 1,343 ± 754/mm³ (TP), 9,081 ± 1879/mm³ and 1,373 ± 432/mm³ (NST), 7,080 ± 642/mm³ and 700 ± 0/mm³ (control).Among the total nucleated cells, the percentage of classical monocytes was lower in HU compared with. Controls (3.8 ± 2.1% vs. 7.7 ± 1.3%, p 0.008), lower in TP vs NST (2.4 ± 1.8% vs. 5.6 ± 2.8%, p 0.04) and in TP vs Controls (2.4 ± 1.8% vs. 7.7 ± 1.3%, p 0.001). No differences were shown in the intermediate monocytes population. In turn, nonclassical monocytes were higher in HU compared with TP (0.44 ± 0.3% vs. 0.22 ± 0.2%, p 0.013) and in controls vs TP ( 0.35 ± 0.07% vs 0.22 ± 0.2%, p 0.017). The expression of CD 86 and CD 163 was not significantly different between any of the subsets of monocytes. In classical monocytes, expression of PD-L1 was higher in HU compared with NST (86.1 ± 17.4% vs. 43.9 ± 31.0%, p 0.015 ) and HU vs Controls ( 86.1 ± 17.4% vs. 34.9 ± 8.9%, p 0.019). Expression of PD-L1 in intermediate monocytes and in non classical monocytes were also higher in HU compared with controls (88.9 ± 16.3% vs. 58.6 ± 8.6%, p 0.02 and 79.6 ± 30.2% vs. 37.1 ± 4.6% , p 0.02 respectively). These results are depicted in table and figure 1. Conclusion: Different treatments for sickle cell disease have affected the monocyte subsets distribution and PD-L1 expression in the population studied. HU and Transfusion Program induced a reduction in the Classical Monocyte subset, more pronounced in the latter. Classical monocytes are largely associated with a pro-inflammatory profile. The use of HU in SCD has been previously associated with less classical monocytes, and induction of monocyte maturation might help explain this finding; as for chronic transfusions, a migratory effect of monocytes to tissues has been proposed. The higher expression of PD-L1 in patients submitted to exchange transfusion and in use of HU indicate inhibition of inflammation, which is more pronounced in the HU group. Both treatments have immunomodulatory effects on SCD, however, to date, no inflammatory markers that assess response to treatment are available. Our findings might contribute to uncovering the role of PD-L1 in the chronic inflammation of SCD and to identify a potential biomarker. Nevertheless, further studies with larger cohorts are warranted in these settings. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Understanding Hydroxyurea Utilization in Sickle Cell Disease: Exploring Patient and Provider Attitudes and Beliefs

Introduction Hydroxyurea (HU), a first line sickle cell disease (SCD) modifying drug, has a 22%-48% utilization rate, according to national estimates (Lanzkron 2006, Stettler 2015, Knisely 2020). There are numerous factors identified as barriers to adherence of hydroxyurea such as access to care (Badawy 2017). Given the high frequency of SCD inpatient admissions at the University of Chicago Medical Center (UCMC) and thus the limited opportunity for outpatient care where disease modifying therapies can be initiated, we proposed a quality improvement project to monitor HU education and usage during inpatient encounters. Methods Our project was reviewed by the UCMC Institutional Review Board and approved to meet quality improvement (QI) determination. To address the question of HU initiation in SCD during inpatient encounters, we surveyed key stakeholders including patients with SCD and providers. We identified consecutive patients with SCD who were either established with primary care or hematology at UCMC (n=197) and distributed our deidentified survey through a REDCap secure link to patients with active email accounts (n=135). We designed a provider survey eliciting knowledge, beliefs, and perspectives on HU use in SCD and distributed this through REDCap to 182 frontline providers. We analyzed the data qualitatively, identifying patterns and common themes from aggregate responses and free text answers. Results The patient survey response rate was 31% (n=42/135). Forty-five percent (n=18) of patients agreed that they missed follow up appointments due to admissions. Approximately half of patient respondents indicated they were not taking HU (n=19). Additionally, of those patients, 72% (n=14) indicated they would be willing to deal with the side effects of HU if it improved their SCD symptoms and 32% (n=6) said they would consider initiation of HU during an inpatient encounter. Patient respondents cited the benefits of HU, including improving quality of life (33%; n=13), preventing pain episodes (43%; n=17), improving mortality (18%; n=7), and helping prevent hospitalizations (36%; n=14). In terms of further education, 35% (n=14) of patient respondents indicated they would like to learn more about HU. 88% (n=35) indicated they would like to learn more about other disease modifying therapies. The provider survey response rate was 73% (n=132/182), of whom, 40% (n=52) were IM or Med/Peds residents, 28% (n=37) were medicine attendings, and 11% (n=15) were Hematology/Oncology faculty or fellows. 98% (n=129) of respondents overall agreed that HU initiation should be offered to patients with SCD during inpatient encounters and that the benefits of HU in SCD outweighed the potential harms. Providers requested tools to facilitate prescribing HU during inpatient encounters, including bundled orders ("orderset") within the EMR (55%; n=73), an option for inpatient SCD consult services (28%; n=37), education sessions and materials (45%; n=59), and a linked outpatient hematology referral system (58%; n=77). Conclusion: Results from our patient survey demonstrate an unmet need for expanding access to HU into inpatient encounters and providing access to other disease modifying therapies and potential cures. Providers would be comfortable with initiation and monitoring of HU during inpatient SCD encounters. To facilitate this, providers request additional education and process resources. Results from both surveys inform a plan to address disparities in HU utilization rates among patients with SCD at UCMC, in addition to providing opportunities to enhance SCD care overall. The path forward will include building curricula for providers, educational handouts on disease modifying therapies for patients, generating a HU prescribing orderset embedded in the EMR, and innovating a SCD inpatient consult service at UCMC.

Barriers and Facilitators of Availability of Hydroxyurea for Sickle Cell Disease in Tanzania; A Qualitative Study of Pharmaceutical Manufacturers, Importers, and Regulators.

Despite three decades of proven safety and effectiveness of hydroxyurea in modifying sickle cell disease (SCD), its accessibility is limited in Sub-Saharan Africa, which shares 75% of the world's SCD burden. Therefore, it is time to explore the barriers and facilitators for manufacturing and importation of hydroxyurea for SCD in Tanzania. This was qualitative research that employed a case study approach. Purposive sampling followed by an in-depth interview (IDI) using a semi-structured questionnaire aspired by data saturation enabled us to gather data from 10 participants. The study participants were people with more than three years of experience in pharmaceuticals importation, manufacturing, and regulation. The audio-recorded data were verbatim transcribed and analyzed using thematic analysis. Two themes were generated. The first comprised barriers for importation and manufacturing of hydroxyurea with sub-themes such as inadequate awareness of SCD and hydroxyurea, limited market, and investment viability. The second comprised opportunities for importation and manufacturing of hydroxyurea with sub-themes such as awareness of activities performed by medicines regulatory authority and basic knowledge on SCD and hydroxyurea. Inadequate understanding of SCD, hydroxyurea, and orphan drug regulation are major issues that aggravate the concern for limited market and investment viability. Existing opportunities are a starting point towards increasing the availability of hydroxyurea.

Evaluation of pharmacological efficacy and safety of hydroxyurea in sickle cell disease: Study of a pediatric cohort from Chhattisgarh, India

Sickle cell disease (SCD) is a disease of abnormal hemoglobin associated with severe clinical phenotype and recurrent complications. Hydroxyurea (HU) is one of the US-FDA approved and commonly used drug for the treatment of adult SCD patients with clinical ­severity. However, its use in the pediatric groups remains atypical. Despite a high prevalence of the disease in the state Chhattisgarh, there is a lack of evidence supporting its use in pediatric patients. This study aimed to evaluate the pharmacological and clinical efficacy and safety of HU in a large pediatric cohort with SCD from Central India. The study cohort consisted of 164 SCD (138 Hb SS and 26 Hb S beta-thalassemia) children (≤14 years of age) on HU therapy, who were monitored for toxicity, hematological and clinical efficacy at baseline (Pre-HU) and after 24 months (Post-HU). The results highlight the beneficial effects of HU at a mean dose of 18.7 ± 7.0 mg/kg/day. A significant improvement was observed, not only in physical and clinical parameters but also in hematological parameters which include fetal hemoglobin (Hb F), total hemoglobin, hematocrit, mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) levels, when evaluated against the baseline. We did not observe any significant adverse effects during the treatment period. Similar results were obtained on independent analysis of Hb SS and Hb Sβ patients. These findings strengthen the beneficial effect of hydroxyurea in pediatric population also without any serious adverse effects and builds up ground for expanding its use under regular monitoring.

Hydroxyurea (hydroxycarbamide) for sickle cell disease.

Hydroxyurea (hydroxycarbamide) for sickle cell disease.

Barriers to Therapeutic Use of Hydroxyurea for Sickle Cell Disease in Nigeria: A Cross-Sectional Survey.

Background: Sickle cell disease, the inherited blood disorder characterized by anemia, severe pain and other vaso-occlusive complications, acute chest syndrome, disproportionate hospitalization, and early mortality, has significant financial, social, and psychosocial impacts and drains individuals, families, and health systems globally. Hydroxyurea could improve the health of the 300,000 individuals born each year with sickle cell disease in sub-Saharan Africa; however, challenges to adoption and adherence persist. This study assessed the barriers to therapeutic use of hydroxyurea for sickle cell disease within the Nigerian healthcare system, specifically from the level of the patient, provider, and health system. Methods: We used purposive sampling to recruit participants from 13 regions in Nigeria. A cross-sectional survey was administered to physicians (n = 70), nurses or counselors (n = 17), and patients or their caregivers (n = 33) at 13 health centers. Findings were mapped onto the appropriate Consolidated Framework for Implementation Research (CFIR) domains. Results: This study was able to identify factors that mapped onto the inner setting, outer setting, and characteristics of individuals domains of CFIR. The majority of physicians (74.3%) prescribe hydroxyurea, and half stated hydroxyurea is the standard of care. Among clinicians, barriers included limited knowledge of the drug, as well as low self-efficacy to prescribe among physicians and to counsel among nurses; perceived side effects; perceived patient preference for traditional medicine; cost for patient and expense of accompanying laboratory monitoring; and limited availability of the drug and equipment for laboratory monitoring. Among patients and caregivers, barriers included lack of knowledge; perceived side effects; cost; religious beliefs of disease causation; and lack of pediatric formulation. Conclusions: Findings suggest that patient, provider, and health systems-level interventions are needed to improve hydroxyurea uptake among providers and adherence among patients with sickle cell disease in Nigeria. Interventions such as patient education, provider training, and policy change could address the disproportionate burden of sickle cell disease in sub-Saharan Africa and thus improve health equity.

An Immersive Virtual Reality Curriculum for Pediatric Hematology Clinicians on Shared Decision-making for Hydroxyurea in Sickle Cell Anemia.

Although hydroxyurea (HU) is an effective treatment for sickle cell anemia, uptake remains low. Shared decision-making (SDM) is a recommended strategy for HU initiation to elicit family preferences; however, clinicians lack SDM training. We implemented an immersive virtual reality (VR) curriculum at 8 pediatric institutions to train clinicians on SDM that included counseling virtual patients. Clinicians' self-reported confidence significantly improved following the VR simulations on all communication skills assessed, including asking open-ended questions, eliciting specific concerns, and confirming understanding (Ps≤0.01 for all). VR may be an effective method for educating clinicians to engage in SDM for HU.

The Influence of the Age of Adults with Sickle Cell Disease on the Uptake, Utilization and Efficacy of Hydroxyurea

BackgroundDespite the efficacy of Hydroxyurea (HU) in decreasing morbidity and mortality in adults with sickle cell disease (SCD) the uptake of and adherence with HU is poor, probably as the result of a combination of both physician and patient related factors. Lack of knowledge about HU, doubts regarding effectiveness, concerns over side effects and unrealistic expectations from HU treatment have been previously identified as barriers to the wider uptake of HU by the patient. Since approval of HU for SCD by the FDA in 1998, there has been a progressive increase of the use of HU in SCD. Changes in approach and practice over this time may have impacted the attitude towards HU of patients of different ages differently. The impact of patients' age on the uptake and utilization of HU has not been studied. We investigated the impact of age on the attitudes of adult patients towards the purpose, side effects, associated risks and benefits of taking HU.MethodsWe conducted qualitative interviews with adult SCD patients from a geographically diverse population recruited from national conferences and local SCD clinics. Data were gathered as part of a larger study of decision making regarding disease modifying therapies for SCD and development of a decision- aid tool for patients involving these disease-modifying therapies. We used a semi-structured open-ended interview guide to collect data. Audio recordings were transcribed verbatim. Transcripts were coded using qualitative content analysis with NVivo 11. We sought to understand attitudes of adult patients with SCD towards available treatment options. We then focused our analyses specifically on attitudes towards HU as a model for how SCD patients viewed their disease and treatment options. We also sought to interrogate differences in attitudes among patients who reached adulthood, before and after the general adoption of hydroxyurea as a treatment option for SCD.ResultsAge of the 95 participants ranged from 18 years to 67 years old. Female = 71. While approximately 50% of all participants reported that they were currently taking HU, younger participants were more likely to be currently taking HU than the older participants (p = .05). Seventy percent of the younger adults (Age 18-30) reported they were currently taking HU as compared to 41% of the older adults (Age 31-67) [table 1]. Younger participants were more likely to report that the decision to accept a physician recommendation to start HU was made by their parent, though some participants decided to start HU as a young adult. Younger participants understood the purpose of HU as intended to improve “blood counts” thereby decreasing crises and hospital stays. They were hopeful that HU would help and thus focused on the potential for successfully managing SCD complications rather than on the side effects from HU. For those who decided to start as young adults, they offered positive accounts in regards to the decision to start HU and maintain the treatment.In contrast, the older participants were not well informed about HU and reported a concern about taking a chemotherapy drug. Older adults currently taking HU were more likely to be skeptical about whether they were receiving any benefits from staying on the treatment. They were also less trusting than the younger participants, that all of the side effects from HU are known or that healthcare providers divulged them. Older participants were more likely than the younger participants to report advanced complications from SCD. They were also more likely to report an aversion to taking medications. Six older participants reported they tried HU past, but stopped taking the drug because of either bad side effects, lack of efficacy, or the belief that HU caused more crises.ConclusionThe younger adults with SCD are more likely to have started HU as children and are more likely to be taking HU and believe in its efficacy while older adults were more skeptical about the efficacy of HU and the information they are provided by their healthcare providers. That so many older adults are concerned about the efficacy of HU also raises the question whether it HU is effective in the face of multi-organ complications. These data provide the rationale for a larger prospective study of the impact of age on both the attitudes and efficacy of HU. We believe that the data from this study will help tailor healthcare provider approaches to HU amongst older adults. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

CRISPR-Cas9 Gene Editing for Sickle Cell Disease and β-Thalassemia

(Abstracted from N Engl J Med 2021;384:252–260) Transfusion-dependent β-thalassemia (TDT) and sickle cell disease (SCD) are the most common inherited hematologic disorders, affecting approximately 60,000 and 300,000 patients worldwide, respectively. Current therapies, including red blood cell (RBC) transfusion and iron chelation in TDT and transfusion, pain management, and hydroxyurea in SCD, help to manage the disorders but do not address the underlying cause.

Fixed vs. Escalated Dosing of Hydroxyurea for Sickle Cell Anemia in Sub-Saharan Africa

Hydroxyurea (HU) modifies the natural history of sickle cell anemia in adults and children. Unfortunately, this agent is not routinely available for

Effective use of hydroxyurea for sickle cell anemia in low-resource countries.

Over the past several decades, hydroxyurea has emerged as a well tolerated and potent disease-modifying therapy for children and adults with sickle cell anemia (SCA). Strong, evidence-based recommendations from the National Institutes of Health, American Society of Hematology, and British Society of Haematology document that hydroxyurea is now standard of care treatment for SCA. In low-resource settings, however, hydroxyurea is rarely utilized due to lack of availability, inadequate treatment guidance, and excessive costs. Research trials conducted within the Caribbean and sub-Saharan Africa confirm the efficacy of hydroxyurea as a well tolerated, feasible, and beneficial treatment in low-resource countries. Hydroxyurea is therefore vital to reaching the targets for control of SCA outlined by the WHO. To maximize its utilization toward real-world effectiveness, specific attention must be given to healthcare provider education and training, public and institutional awareness, and medication access and affordability. Efforts to introduce hydroxyurea effectively into low-resource countries should urgently address the lack of treatment guidelines, gaps in knowledge and clinical infrastructure, and medication inaccessibility. Partnerships among governmental, academic, pharmaceutical, and charitable organizations must tackle these barriers so that all individuals living with SCA worldwide can benefit from hydroxyurea.

Neutrophils remain detrimentally active in hydroxyurea-treated patients with sickle cell disease.

Neutrophilia is a feature of sickle cell disease (SCD) that has been consistently correlated with clinical severity and has been shown to remain highly activated even at steady state. In addition to induction of fetal hemoglobin (HbF), hydroxyurea (HU) leads to reduction in neutrophil count and their adhesion properties, which contributes to the clinical efficacy of HU in SCD. Although HU reduces the frequency and severity of acute vaso-occlusive crises (VOCs) and chest syndrome, HU therapy does not abolish these acute clinical events. In this study we investigated whether neutrophils in SCD patients whilst on HU therapy retained features of detrimental pro-inflammatory activity. Freshly isolated neutrophils from SCD patients on HU therapy at steady state and from ethnic-matched healthy controls were evaluated ex vivo for their degranulation response and production of neutrophil extracellular traps (NETs). Unstimulated SCD patient neutrophils already produced NETs within 30 minutes, compared to none for healthy neutrophils, and by 4 hours, these neutrophils produced significantly more NETs than the control neutrophils (P = 0.0079**). Higher numbers of neutrophils from SCD patients also showed higher degree of degranulation-related intracellular features compared to healthy neutrophils, including rough-textured cellular membranes (P = 0.03*), double-positivity for F-Actin and CD63 (P = 0.02*) and re-located CD63 within cytoplasm more efficiently than their healthy counterparts (P = 0.02*). The neutrophils from SCD donors released more myeloperoxidase (P = 0.02*) in the absence of any trigger. Our data showed that neutrophils from patients with SCD at steady state remained active during hydroxyurea treatment and are likely to be able to contribute to the SCD pro-inflammatory environment.

The use of hydroxyurea in sickle cell disease: A single tertiary centre experience at the National Hospital, Abuja, Nigeria

Background. Hydroxyurea (HU) has been found to be beneficial in sickle cell disease (SCD), reducing the occurrence of severe manifestations of the disease such as painful crises and blood transfusions. Although a standard of care for SCD in the developed countries of the world, limited data are available on its use in Africa. Objectives. To review indications of the use of HU, laboratory monitoring and outcome in children with SCD. Methods. A retrospective review of 74 patients treated with HU (15 - 30 mg/kg/day) for a minimum of 6 months. The main outcome measures were indications for use of HU, haemoglobin level (Hb), packed cell volume (PCV), white cell count (WBC), absolute neutrophil count (ANC), serum alanine aminotransferase (ALT) and creatinine. Descriptive statistics were expressed as means ±2 standard deviations. Data were compared pre and post HU therapy, using the chi-square and Student’s t -test as appropriate. Results. The 74 patients constituted 7.26% of the SCD clinic population and were aged 2.25 - 16 years (mean (SD) 8.48 (3.67)) and were on HU therapy for 0.5 - 4.8 years (mean (SD) 1.72 (1.12)). The haemoglobin genotypes were Hb SS 72 (98.7%); Hb SC and Hb SS+F 1 (1.35%) each. Indications for HU use were abnormalities of transcranial Doppler ultrasound (TCD) 39 (52.7%), multiple vaso-occlusive crises (VOC) 18 (24.3%), strokes 14 (18.9%), as well as repeated blood transfusions 9 (12.2%) and hospital admissions 7 (9.5%). Some patients had more than one indication. There were significantly fewer TCD abnormalities, VOC, strokes, splenic sequestrations, blood transfusions and hospital admissions following use of HU. The mean Hb and PCV increased while WBC and ANC decreased. Occurrence of acute chest syndrome, priapism, serum creatinine, ALT and platelet levels were not affected. Conclusions. Hydroxyurea therapy reduces the occurrence of severe manifestations and improves laboratory parameters in children with SCD.

Common Myeloid Progenitors As Biomarkers of Hbf Response to Hydroxyurea in Sickle Cell Disease

Background Hydroxyurea (HU) is used to treat sickle cell disease (SCD) in part because of its ability to increase hemoglobin F (HbF) concentration, but the mechanism by which HU induces HbF, and the low or lack of HbF response in a fraction of the patient remains unclear. HU causes myelo-suppression and induces stress hematopoiesis, which is associated with increase production of HbF. Earlier research has shown that HbF levels in SCD patients are inversely correlated with reticulocytes, which can be secondary to: 1) HbF-induced decreased hemolysis with less needs for red blood cell (RBC) production, and 2) Myelo-suppression. It has also been shown that the number of CD34+ cells is generally lower in HU treated patients, but the overall response of the hematopoietic system in relationship to HbF has not been characterized. Here, we prospectively isolated hematopoietic stem and progenitor cells (HSPCs) from HU-treated SCD patients and characterize their hematopoietic and HbF responses. Methods Peripheral blood (PB) was collected from 19 HbSS who had been HU for &gt;3 years and from 12 healthy controls. Frozen mono-nuclear cells were analyzed by flow cytometry using CD49f, 90 45Ra, 123, 235a, 38, 34, 33 and lineage antibodies. The number of 49f+ long-term Hematopoietic Stem Cells (LT-HSC), Multipotent Progenitors (MPPs), Common Myeloid Progenitors (CMPs), Megakaryocyte-Erythroid Progenitors (MEPs), and Granulocyte-Monocyte Progenitors (GMPs) per uL of blood or per CD34+ cells was then quantified. Results The percentages of reticulocytes per uL of blood were found to correlate positively with the concentration per uL of blood of all stem and progenitor cell populations tested (CD34 (R2 = 0.6583), LT-HSC (R2 = 0.3532), MPP (R2 = 0.2603), CMP (R2 = 0.5889), MEP (R2 = 0.2411), and GMP (R2 = 0.6911)). Statistically significant (p&lt;0.05) inverse correlations were also observed between HbF levels and the number of CD34+/uL ( R2 = 0.2931), and the number of CMP/uL (R2 = 0.3732). Normalization of the data to the number of circulating CD34+ cells revealed that there was a strong inverse correlation between HbF levels and the percentage of circulating CMPs (R2 = 0.5424), and importantly, that this correlation was specific to the CMP population since Hb F did not correlates with any of the other HSPC populations analyzed . Analysis of the PB of 12 healthy individuals revealed that, as in SCD patients, the percentage of CMPs varied between &lt; 10% and &gt;60% of the total circulating CD34+ cells. Further analysis revealed that the CMP percentages in both SCD and healthy controls appeared characteristics of each individual tested since the measurements were remarkably correlated (R2 &gt;0.7) when they were repeated on blood samples collected at intervals of two-weeks or one-year. Discussion The positive correlation between the reticulocyte and HSPC populations that we observed was previously unreported and suggests that, in first approximation, the reticulocytes could serve as a proxy for the levels of circulating HSPCs which could help assess the degree of bone marrow suppression in compliant non-responding HU-treated patients. We identified an inverse correlation between percentages of HbF and circulating CMPs in HU-treated SCD patients that is specific to these progenitors. The specificity of the correlation suggests that the major mechanism for the correlation is unlikely to be differential mobilization of CMPs to the PB since inducing mobilization generally affect all HSPCs. A depletion of the CMPs in the bone marrow of high Hb F responders is therefore a more likely mechanism. A possible mechanism for the correlation is that HU acts directly on CMPs by accelerating their differentiation leading to the relative depletion of these progenitors in high F individuals, and initiating the reprogramming of gene expression that ultimately results in high level of gamma-globin expression. Alternatively, the similar range of variability in the percentage of CMPs in HU-treated SCD patients and in healthy individuals never exposed to HU, and the observation that the percentage of circulating CMP seem to be an intrinsic characteristic of each individual suggest that the percentage of circulating CMPs might be a genetically determined marker associated with the ability to produce HbF in response to HU therapy, rather than being a consequence of the treatment. Figure Disclosures Minniti: Doris Duke Foundation: Research Funding. Manwani:Novartis: Consultancy; Pfizer: Consultancy; GBT: Consultancy, Research Funding.