Oral L-glutamine therapy for sickle cell anemia: I. Subjective clinical improvement and favorable change in red cell NAD redox potential

Endari treatment ameliorates sickle cell-related disruption in intestinal barrier functions and is associated with prolonged survival in sickle cell mice

BACKGROUND

Endari (L-glutamine) is a conditional amino acid that reduces the frequency of vaso-occlusive crisis (VOC) in sickle cell disease (SCD).

AIM

To investigate whether Endari could ameliorate intestinal barrier function and improve survival outcomes in SCD.

METHODS

We treated female Townes SCD mice with Endari and evaluated their intestinal barrier functions by measuring the recovery of orally administered fluorescein isothiocyanate (FITC)-conjugated dextran 4 kDa in serum, and serum intestinal fatty acid binding proteins (iFABP) and lipopolysaccharide (LPS) concentrations by ELISA. We also explored the impact the Endari has on the survival of the SCD mice that underwent repeated experimentally-induced VOC.

RESULTS

Compared to SCD mice treated with water only, Endari-treated mice showed improved intestinal barrier functions, with decrease in the barrier permeability and reduction in the translocation of lipopolysaccharides from the intestinal lumen into the circulation. These changes occurred after only 4 weeks of Endari treatment. Improved intestinal barrier function was also associated with prolonged survival in Endari-treated SCD mice after repeated experimentally-induced VOC.

CONCLUSION

Our findings provide the evidence supporting the beneficial effects of Enadri in improving intestinal barrier function and associated survival outcomes in SCD.

Endothelial dysfunction in Sickle Cell Disease: Strategies for the treatment

Sickle Cell Anemia (SCA), is an inherited hemoglobinopathy characterized by the presence of an abnormal hemoglobin (HbS), being the most prevalent sickle cell disease (SCD). SCA is characterized by vascular endothelial dysfunction, which contributes significantly to various clinical conditions, including but not limited to pulmonary hypertension, priapism, cutaneous leg ulceration, and stroke. The pathophysiology of endothelial dysfunction (ED) in SCA is a multifaceted process involving a chronic inflammatory and hypercoagulable state. Key factors include hemolysis-associated elements like reduced arginine and nitric oxide (NO) availability, elevated levels of vascular adhesion molecules, the uncoupling effect of NO synthase, heightened arginase activity, an environment characterized by oxidative stress with the production of reactive oxygen and nitrogen species, and occurrences of ischemia-reperfusion injury, along with apolipoprotein A-1 depletion. The urgency for novel interventions addressing ED is evident. Presently, there is a focus on investigating small molecules that disrupt the arginine-nitric oxide pathway, exhibiting anti-inflammatory and antioxidant properties while diminishing levels of cellular and vascular adhesion molecules. In this mini-review article, we delve into the progress made in strategies for treating ED in SCD with the aim of cultivating insights for drug design.

Advances in pharmacotherapy for sickle cell disease: what is the current state of play?

INTRODUCTION

Despite over 100 years of neglect and insufficient funding, sickle cell disease has risen to the top of the discussions due to the recent approval of two new genetic therapies. Prior to these approvals, there were only four prior approved medications for sickle cell disease in spite of being the most common inherited blood disorder. The advent and expense of these new genetic therapies have finally brought the trials and tribulations associated with SCD including the suffering and early mortality of affected individuals to the much-needed limelight. Presently, questions about how these therapies will be used and what that means for ongoing pharmaceutical development remain.

AREAS COVERED

Here, we wish to highlight the current medications and treatments for SCD using already published literature as well as scrutinize the tedious process of implementation for these newly approved commercial genetic therapies.

EXPERT OPINION

In our expert opinion, despite the progress we have made, significant challenges remain and the most important requirement for any of these treatments is ensuring all affected individuals have access to a sickle cell specialist who can provide comprehensive care.

Current and Future Therapeutics for Treating Patients with Sickle Cell Disease

Sickle cell disease (SCD) is the most common genetic blood disorder in the United States, with over 100,000 people suffering from this debilitating disease. SCD is caused by abnormal hemoglobin (Hb) variants that interfere with normal red blood cell (RBC) function. Research on SCD has led to the development and approval of several new SCD therapies in recent years. The recent FDA-approved novel gene therapies are potentially curative, giving patients an additional option besides a hematopoietic bone marrow transplant. Despite the promise of existing therapies, questions remain regarding their long-term pharmacological effects on adults and children. These questions, along with the exorbitant cost of the new gene therapies, justify additional research into more effective therapeutic options. Continual research in this field focuses on not only developing cheaper, more effective cures/treatments but also investigating the physiological effects of the current therapies on SCD patients, particularly on the brain and kidneys. In this article, we undertake a comprehensive review of ongoing clinical trials with completion dates in 2024 or later. Our exploration provides insights into the landscape of current therapeutics and emerging novel therapies designed to combat and potentially eradicate SCD, including the latest FDA-approved gene therapies.

Roles of Pharmacists in the Management of Sickle Cell Disease in Adults: A Narrative Review

Background: Sickle cell disease (SCD) is an autosomal, recessive, genetic condition of the sickle cell genes. It affects about 100 000 people in the United States where an estimated 1 out of every 365 black children and 1 out of every 13 black children will be born with SCD and sickle cell trait, respectively. Severe and unpredictable pain crisis are the leading cause of emergency department visit for adult patients with SCD and account for 90% of inpatient hospitalizations and 85% of all acute medical care, as well as high usage of medical resources. The care of patients with SCD is complex and requires a multidisciplinary approach. With a few pharmacotherapeutic options to reduce SCD complications and pain episodes, the role of pharmacists in the medication management is unclear. This article aims to outline the potential role of pharmacists in SCD management. Data sources: The authors searched Medline, PubMed, EMBASE, and Scopus from January 1, 1990 to August 31, 2022, for primary literature that assessed the role of pharmacists in managing patients with SCD. Results: The authors identified relevant studies and summarized the role of pharmacists in SCD management. Conclusions: Access to comprehensive health care is essential to ensure that patients with SCD have decreased hospitalizations and good health-related quality of life. Pharmacists are an integral part of the multidisciplinary health-care team and can help patients with SCD navigate the complexities of health care. Pharmacists are medication experts who are positioned to ensure comprehensive care in the acute and chronic SCD management.

Simvastatin-Mediated Nrf2 Activation Induces Fetal Hemoglobin and Antioxidant Enzyme Expression to Ameliorate the Phenotype of Sickle Cell Disease

Sickle cell disease (SCD) is a pathophysiological condition of chronic hemolysis, oxidative stress, and elevated inflammation. The transcription factor Nrf2 is a master regulator of oxidative stress. Here, we report that the FDA-approved oral agent simvastatin, an inhibitor of hydroxymethyl-glutaryl coenzyme A reductase, significantly activates the expression of Nrf2 and antioxidant enzymes. Simvastatin also induces fetal hemoglobin expression in SCD patient primary erythroid progenitors and a transgenic mouse model. Simvastatin alleviates SCD symptoms by decreasing hemoglobin S sickling, oxidative stress, and inflammatory stress in erythroblasts. Particularly, simvastatin increases cellular levels of cystine, the precursor for the biosynthesis of the antioxidant reduced glutathione, and decreases the iron content in SCD mouse spleen and liver tissues. Mechanistic studies suggest that simvastatin suppresses the expression of the critical histone methyltransferase enhancer of zeste homolog 2 to reduce both global and gene-specific histone H3 lysine 27 trimethylation. These chromatin structural changes promote the assembly of transcription complexes to fetal γ-globin and antioxidant gene regulatory regions in an antioxidant response element-dependent manner. In summary, our findings suggest that simvastatin activates fetal hemoglobin and antioxidant protein expression, modulates iron and cystine/reduced glutathione levels to improve the phenotype of SCD, and represents a therapeutic strategy for further development.

Defining curative endpoints for sickle cell disease in the era of gene therapy and gene editing

A growing number of gene therapy- and gene editing-based treatments for patients with sickle cell disease (SCD) are entering clinical trials. These treatments, designed to target the underlying cause of SCD, have the potential to provide functional cures, which until now were possible only through allogeneic hematopoietic stem cell transplant. However, as these novel approaches advance from early- to late-stage clinical trials, it is essential to identify physiologically and clinically relevant endpoints that can demonstrate the achievement of a functional cure for SCD. Here, we present an overview of the pathophysiology of SCD and current treatment options, review ongoing SCD clinical trials using gene therapy or gene editing approaches, and identify the most relevant endpoints for demonstrating the attainment of a functional cure for SCD.

Cyclic Peptides as Aggregation Inhibitors for Sickle Cell Disease

Sickle cell disease is a missense genetic disorder characterized by the aggregation of deoxy-HbS into helical fibers that distort erythrocytes into a sickle-like shape. Herein, we investigate, through molecular dynamics, the effect of nine 5-mer cyclic peptides (CPs), tailor-designed to block key lateral contacts of the fibers. Our results show that the CPs bind orthogonally to the main HbS pocket involved in the latter contacts, with some revealing exceedingly long residence times. These CPs display moderate to high specificity, exhibiting molecular recognition events even at a HbS/CP (1:1) ratio. A much lower HbS-CP binding free energy, longer residence times, and higher specificity are also found relative to a previously reported CP with modest in vitro antisickling activity. These results indicate that some of these CPs have the potential to reduce the concentration of aggregation-competent deoxy-HbS, precluding or delaying the formation of lateral contact at the homogeneous nucleation stage.

The evolving treatment landscape for children with sickle cell disease

Sickle cell disease is the most common inherited pathological haemoglobinopathy. Over the past 30 years, disease-related morbidity and mortality have improved in high-income countries due to advances in preventive care and treatments. Established disease-modifying therapies, such as hydroxyurea (hydrocarbamide), are continuing to have an important role in the treatment of sickle cell disease, and newer agents also show promise. In the past 5 years, the US Food and Drug Administration approved three additional sickle cell disease-modifying medications, and new gene therapies have been developed as an alternative curative treatment to haematopoietic stem-cell transplantation. In this Review, we discuss the current treatment landscape for paediatric sickle cell disease and emerging innovations in care. We also review the need for close, long-term management for children receiving newer therapies and the importance of ongoing investment in people with sickle cell disease in low-income and middle-income countries.

Long-Term L-Glutamine Treatment Reduces Hemolysis without Ameliorating Hepatic Vaso-Occlusion and Liver Fibrosis in a Mouse Model of Sickle Cell Disease

Sickle cell disease (SCD) is an autosomal recessive monogenic disorder caused by a homozygous mutation in the β-globin gene, which leads to erythrocyte sickling, hemolysis, vaso-occlusion, and sterile inflammation. The administration of oral L-glutamine has been shown to reduce the frequency of pain in SCD patients; however, the long-term effect of L-glutamine in SCD remains to be determined. To understand the long-term effect of L-glutamine administration in the liver we used quantitative liver intravital microscopy and biochemical analysis in humanized SCD mice. We here show that chronic L-glutamine administration reduces hepatic hemoglobin-heme-iron levels but fails to ameliorate ischemic liver injury. Remarkably, we found that this failure in the resolution of hepatobiliary injury and persistent liver fibrosis is associated with the reduced expression of hepatic Kupffer cells post-L-glutamine treatment. These findings establish the importance of investigating the long-term effects of L-glutamine therapy on liver pathophysiology in SCD patients.

Combination L-Glutamine with Gemcitabine and Nab-Paclitaxel in Treatment-Naïve Advanced Pancreatic Cancer: The Phase I GlutaPanc Study Protocol

Advanced pancreatic cancer is underscored by progressive therapeutic resistance and a dismal 5-year survival rate of 3%. Preclinical data demonstrated glutamine supplementation, not deprivation, elicited antitumor effects against pancreatic ductal adenocarcinoma (PDAC) alone and in combination with gemcitabine in a dose-dependent manner. The GlutaPanc phase I trial is a single-arm, open-label clinical trial investigating the safety of combination L-glutamine, gemcitabine, and nab-paclitaxel in subjects (n = 16) with untreated, locally advanced unresectable or metastatic pancreatic cancer. Following a 7-day lead-in phase with L-glutamine, the dose-finding phase via Bayesian design begins with treatment cycles lasting 28 days until disease progression, intolerance, or withdrawal. The primary objective is to establish the recommended phase II dose (RP2D) of combination L-glutamine, gemcitabine, and nab-paclitaxel. Secondary objectives include safety of the combination across all dose levels and preliminary evidence of antitumor activity. Exploratory objectives include evaluating changes in plasma metabolites across multiple time points and changes in the stool microbiome pre and post L-glutamine supplementation. If this phase I clinical trial demonstrates the feasibility of L-glutamine in combination with nab-paclitaxel and gemcitabine, we would advance the development of this combination as a first-line systemic option in subjects with metastatic pancreatic cancer, a high-risk subgroup desperately in need of additional therapies.

Metabolic signatures of cardiorenal dysfunction in plasma from sickle cell patients, as a function of therapeutic transfusion and hydroxyurea treatment

Metabolomics studies in sickle cell disease (SCD) have been so far limited to tens of samples, owing to technical and experimental limitations. To overcome these limitations, we performed plasma metabolomics analyses on 596 samples from patients with sickle cell sickle cell disease (SCD) enrolled in the WALK-PHaSST study. Clinical covariates informed the biological interpretation of metabolomics data, including genotypes (hemoglobin SS, hemoglobin SC), history of recent transfusion (HbA%), response to hydroxyurea treatment (HbF%). We investigated metabolic correlates to the degree of hemolysis, cardiorenal function, as determined by tricuspid regurgitation velocity (TRV), estimated glomerular filtration rate (eGFR), and overall hazard ratio (unadjusted or adjusted by age). Recent transfusion events or hydroxyurea treatment were associated with elevation in plasma free fatty acids and decreases in acyl-carnitines, urate, kynurenine, indoles, carboxylic acids, and glycine- or taurine-conjugated bile acids. High levels of these metabolites, along with low levels of plasma S1P and L-arginine were identified as top markers of hemolysis, cardiorenal function (TRV, eGFR), and overall hazard ratio. We thus uploaded all omics and clinical data on a novel online portal that we used to identify a potential mechanism of dysregulated red cell S1P synthesis and export as a contributor to the more severe clinical manifestations in patients with the SS genotype compared to SC. In conclusion, plasma metabolic signatures - including low S1P, arginine and elevated kynurenine, acyl-carnitines and bile acids - are associated with clinical manifestation and therapeutic efficacy in SCD patients, suggesting new avenues for metabolic interventions in this patient population.

Contemporary Management and Prevention of Vaso-Occlusive Crises (VOCs) in Adults With Sickle Cell Disease

Sickle cell disease (SCD) is a hematological disorder that primarily affects individuals of African descent from sub-Saharan Africa and along the mediterranean. The main complications leading to hospitalizations include vaso-occlusive crises (VOCs) and acute chest syndrome (ACS). Therefore, the main objective of this paper was to identify and evaluate evidence-based management and prevention of VOCs in patients with SCD. A literature search of PubMed, Medline Cochrane and Google Scholar database (January 1985 to April 2020) was performed using the following search terms "vaso-occlusive crises", "sickle cell disease", "hydroxyurea", "L-glutamine", "voxelotor", "crizanlizumab", "treatment" and "prevention" as well as a combination of these terms. All English-language interventional studies assessing the efficacy and safety of VOC outcomes were evaluated. Literature was excluded if published in a language other than English or if it was a review article. A total of 69 articles were identified and there were 7 articles that met the search criteria. Majority of the studies focused on mean and median annual rates of VOCs as primary outcomes while median time to first sickle cell crises, median rates of hospitalizations etc were evaluated as secondary outcomes. After reviewing the literature, many patients with VOCs will still benefit from hydroxyurea therapy since long term efficacy data and cost is still a concern for the newer agents including L-glutamine, voxelotor and crizanlizumab. Other factors such as cost or compliance may also be taken into consideration when making recommendations for therapy.

Evaluation of Glutamine Utilization in Patients With Sickle Cell Disease

Glutamine (Gln) was FDA-approved in 2017 to reduce acute sickle cell disease (SCD) pain and acute chest syndrome. However, typical pediatric patients with SCD exhibit moderate adherence, measured by a medication possession ratio <80%. This study examined Gln utilization in a "real-world" clinical setting to determine factors influencing medication adherence and to characterize the impact of an interdisciplinary team approach at an institution with specialty pharmacy services. A retrospective chart review identified 40 patients prescribed Gln by sickle cell specialists over a 2-year period and met selection criteria. Gln medication possession ratio for pediatric (72%) and adult (76%) patients were higher than other SCD medications. Pediatric patients (74%) demonstrated significantly lower first-attempt insurance approval rate compared with adult patients (95%) ( P =0.0026), suggesting an initial access barrier for pediatric patients. Pediatric patients demonstrated significantly higher number of medication fills (9.11 fills) compared with adult patients (3.86 fills) ( P =0.007), which suggests interdisciplinary collaboration may facilitate sustainable management of a new therapy. The majority of pediatric (89%) and adult (90%) patients reported high satisfaction with Gln ("excellent") with minor or no side effects. Multidisciplinary health care provider collaborations and tracking medication adherence metrics can help address barriers to care for SCD patients.

Pharmacogenetics of Cardiovascular Prevention in Diabetes: From Precision Medicine to Identification of Novel Targets

Pharmacogenetics—a branch of precision medicine—holds the promise of becoming a novel tool to reduce the social and healthcare burdens of cardiovascular disease (CVD) and coronary artery disease (CAD) in diabetes. The improvement in cardiovascular risk stratification resulting from adding genetic characteristics to clinical data has moved from the modest results obtained with genetic risk scores based on few genetic variants, to the progressively better performances of polygenic risk scores based on hundreds to millions of variants (CAD-PGRS). Similarly, over the past few years, the number of studies investigating the use of CAD-PGRS to identify different responses to cardio-preventive treatment has progressively increased, yielding striking results for lipid-lowering drugs such as proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors and statins. The use of CAD-PGRS to stratify patients based on their likely response to diabetes-specific interventions has been less successful, but promising results have been obtained with regard to specific genetic variants modulating the effects of interventions such as intensive glycemic control and fenofibrate. The finding of diabetes-specific CAD-loci, such as GLUL, has also led to the identification of promising new targets that might hopefully result in the development of specific therapies to reduce CVD burden in patients with diabetes. As reported in consensus statements from international diabetes societies, some of these pharmacogenetic approaches are expected to be introduced in clinical practice over the next decade. For this to happen, in addition to continuing to improve and validate these tools, it will be necessary to educate physicians and patients about the opportunities and limits of pharmacogenetics, as summarized in this review.

Real-World data on efficacy of L-glutamine in preventing sickle cell disease-related complications in pediatric and adult patients

BACKGROUND

L-glutamine has been shown to play an important role in the regulation of oxidative stress which is one of the key contributors to the pathophysiology of sickle cell disease (SCD). In a Phase 3 clinical trial, L-glutamine demonstrated a significant reduction in SCD-related complications including vaso-occlusive crises (VOCs), hospitalizations, and acute chest syndrome (ACS) compared to placebo in patients with SCD.

OBJECTIVE

The primary objective was to confirm the efficacy of L-glutamine (Endari®) therapy in pediatric and adult patients with SCD at follow-up time points of 24, 48 and 72 weeks.

METHODS

In the observational study, nineteen patients with SCD were treated orally with L-glutamine twice daily for 72 weeks. Clinical and laboratory parameters were measured at baseline and follow-up time points. Patients with severe VOC and ACS were hospitalized. Blood transfusion was given in case of ACS and uncontrolled pain associated with VOC despite administration of the highest dose of intravenous (IV) narcotic.

RESULTS

Compared to baseline, patients had significantly fewer pain crises (median change from 3.0 to 0.0; P < 0.00001), hospitalizations (median change from 3.0 to 0.0; P < 0.00001), days of hospitalization (median change from 15.0 to 0.0; P < 0.00001), and blood transfusions (median change from 3.0 to 0.0; P < 0.00001) at 24, 48, and 72 weeks following L-glutamine therapy. Moreover, there was a drastic decrease in the number of ACS events during this time. A significant increase was observed in mean hemoglobin levels and hematocrit proportions from baseline to 72 weeks (P < 0.001). Conversely, compared to baseline, mean reticulocyte counts and lactate dehydrogenase (LDH) levels were considerably lower at follow-up time points (P = 0.003 and P < 0.001, respectively). No patient reported treatment-related adverse events.

CONCLUSION

Although the sample size was small, our data clearly demonstrated that L-glutamine therapy was safe and significantly improved clinical outcomes and hemolysis parameters in patients with SCD.

Recent advances in "sickle and niche" research - Tribute to Dr. Paul S Frenette

In this retrospective, we review the two research topics that formed the basis of the outstanding career of Dr. Paul S. Frenette. In the first part, we focus on sickle cell disease (SCD). The defining feature of SCD is polymerization of the deoxygenated mutant hemoglobin, which leads to a vicious cycle of hemolysis and vaso-occlusion. We survey important discoveries in SCD pathophysiology that have led to recent advances in treatment of SCD. The second part focuses on the hematopoietic stem cell (HSC) niche, the complex microenvironment within the bone marrow that controls HSC function and homeostasis. We detail the cells that constitute this niche, and the factors that these cells use to exert control over hematopoiesis. Here, we trace the scientific paths of Dr. Frenette, highlight key aspects of his research, and identify his most important scientific contributions in both fields.

Functional foods: promising therapeutics for Nigerian Children with sickle cell diseases

Sickle cell disease (SCD), also known as sickle cell anemia (SCA) is one of the structural hemoglobinopathies that occurs due to a single nucleotide mutation from GAG to GTG, which changes the amino acid of a β-globin chain of hemoglobin (Hb) from glutamate to valine. This singular mutation results to disorderliness in red blood cells (RBCs) with advent of changes in RBC morphology and other pathological conditions. In the 1980s, intermittent red blood cell transfusions, opioids, and penicillin prophylaxis were the only available therapy for SCA and were commonly reserved for acute, life threatening complications. So far, the US Food and Drug Administration (FDA) has granted a total of four drugs approval for the prophylaxis and treatment of the clinical complications of SCD. Due to limitations (adherence, safety, adverse effects) of existing therapies in the prophylaxis and treatment of SCD complications in Nigerian children and their inaccessibility to approved drugs, the present study discusses the therapeutic effects of readily available functional food as one of the therapies or an adjunct therapy to tackle the sickle cell crisis in Nigerian Children.

Advances in the Management of Sickle Cell Disease: New Concepts and Future Horizons

Sickle cell disease is a chronic and life-limiting disorder. Approximately 100,000 Americans are affected with sickle cell disease with most being African Americans. Newborn screening for sickle cell is available in the United States, leading to early detection and management of the disease beginning in infancy. According to the 2014 National Heart, Lung, and Blood Institute sickle cell disease guidelines, supportive care has been primary management of sickle cell disease, with hydroxyurea being the only FDA-approved, disease-modifying pharmacotherapy available and allogeneic hematopoietic stem cell transplant the only cure. Since 2017, three new disease-modifying therapies have been approved by the FDA: L-glutamine, crizanlizumab, and voxelotor. This review will discuss pertinent trials, dosing, interactions, side effects, access, cost, and their role in sickle cell management.

Renin-Angiotensin Blockade Reduces Readmission for Acute Chest Syndrome in Sickle Cell Disease

Rationale

Acute chest syndrome (ACS) is a life-threatening complication of sickle cell disease (SCD). Current treatment is supportive-supplemental oxygen, transfusions, and antibiotics. Prevention of ACS may reduce morbidity and mortality in patients with SCD.

Acute chest syndrome appears similar to pulmonary fat embolism (PFE), a complication of severe skeletal trauma or orthopedic procedures from pulmonary micro-vessel blockage by bone marrow fat. Vascular obstruction and bone marrow necrosis occur in PFE and ACS. 

Pulmonary fat embolism rat models have shown that angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II receptor blockers (ARB) mitigate damage in PFE. These medications could work similarly in ACS. We hypothesize that time to readmission after one hospitalization for ACS will be reduced in patients taking ACEI or ARB compared to patients who are not.

Methods

This is a retrospective cohort study. Inclusion criteria are adults (18 to 100 years) with sickle cell anaemia (HbSS), hemoglobin SC (HbSC) disease, sickle cell thalassemia (HbSβThal), hospitalized with ACS over 16 years (January 1, 2000, to March 31, 2016); patients who take and don’t take ACEI or ARB. Children (<18 years old), elderly adults (>100 years old), pregnant patients, and patients with sickle cell trait were excluded.

Data was collected from the Health Facts database, which contains de-identified information from the electronic medical records of hospitals in which Cerner© has a data use agreement.

Kaplan-Meier estimates explored a time-to-event model of ACS readmission. Multivariable analysis (age, gender, smoking history) was conducted using Cox proportional hazards regression. Results were reported around a 95% confidence interval.

Results

There were 6972 patients in total. Of which, 9.6% (n = 667) reported taking ACEI or ARB. Results for the covariates were: average age of 38 years old; 63% female (n = 4366/6969); 16% smokers (n = 1132).

Readmission rates were higher for patients not taking ACEI/ARB than those who did: 0.44 (95% CI 0.43, 0.46) versus 0.28 (95% CI 0.24, 0.31) at one year, and 0.56 (95% CI 0.55, 0.58) versus 0.33 (95% CI 0.29, 0.37) at two years. Age had the strongest effect on readmission rates for patients taking ACEI/ARB (adjusted hazards ratio 0.78 [95% CI 0.68, 0.91]).

Conclusion

Patients with SCD who reported taking ACEI or ARB had lower readmission rates for ACS; age was the strongest covariate. Our results may have a significant impact on the prevention of ACS. Prospective studies comparing ACEI or ARB therapy versus placebo are needed to confirm this preventative effect.

Implications for the Metabolic Fate of Oral Glutamine Supplementation within Plasma and Erythrocytes of Patients with Sickle Cell Disease: A Pharmacokinetics Study

OBJECTIVES

L-Glutamine is FDA-approved for sickle cell disease (SCD), yet the mechanism(s)-of-action are poorly understood. We performed a pharmacokinetics (pK) study to determine the metabolic fate of glutamine supplementation on plasma and erythrocyte amino acids in patients with SCD.

DESIGN

A pK study was performed where patients with SCD fasting for >8hours received oral L-glutamine (10 grams). Blood was analyzed at baseline, 30/60/90minutes/2/3/4/8 hrs. A standardized diet was administered to all participants at 3 established time-points (after 2/5/7hrs). A subset of patients also had pK studies performed without glutamine supplementation to follow normal diurnal fluctuations in amino acids.

SETTING

Comprehensive SCD Center in Oakland, California RESULTS: Five patients with SCD were included, three of whom performed pK studies both with and without glutamine supplementation. Average age was 50.6 ± 5.6 years, 60% were female, 40% SS, 60% SC. Plasma glutamine levels increased significantly after oral glutamine supplementation, compared to minimal fluctuations with diet. Plasma glutamine concentration peaked within 30-minutes of ingestion (p=0.01) before decreasing to a plateau by 2-hours that remained higher than baseline by 8hours. Oral glutamine also increased plasma arginine concentration, which peaked by 4-hrs (p=0.03) and remained elevated through 8-hrs. Erythrocyte glutamine levels began to increase by 8-hours, while erythrocyte arginine concentration peaked at 4-hours.

CONCLUSIONS

Oral glutamine supplementation acutely improved glutamine and arginine bioavailability in both plasma and erythrocytes. This is the first study to demonstrate that glutamine therapy increases arginine bioavailability and may provide insight into shared mechanisms-of-action between these conditionally-essential amino acids.

Cost analysis of acute care resource utilization among individuals with sickle cell disease in a middle-income country

BACKGROUND

The costs associated with the treatment of sickle cell disease (SCD) are understudied in low and middle-income countries (LMIC). We evaluated the cost of treating SCD-related acute complications and the potential cost-savings of hydroxyurea in a specialized hematology center in Brazil.

METHODS

The costs (US dollars) of emergency department (ED) and hospitalizations from SCD-related complications between 01.01.2018 and 06.30.2018 were ascertained using absorption and micro-costing approaches. The reasons for acute hospital visits were grouped as: 1) vaso-occlusive (VOC) pain, 2) infection, 3) anemia exacerbation, and 4) chronic organ damage complications. Hydroxyurea adherence was estimated by medication possession ratio (MPR) during the study period.

RESULTS

In total, 1144 patients, median age 17 years (range 0-70), 903 (78.9%) with HbSS/HbSβ0-thalassemia, 441 (38.5%) prescribed hydroxyurea, visited the ED, of whom 381 (33%) were admitted. VOC accounted for 64% of all ED visits and 60% of all admissions. Anemia exacerbation was the most expensive reason for ED visit ($321.87/visit), while chronic organ damage carried the highest admission cost ($2176.40/visit). Compared with other genotypes, individuals with HbSS/HbSβ0-thalassemia were admitted more often (79% versus 21%, p < 0.0001), and their admission costs were higher ($1677.18 versus $1224.47/visit, p = 0.0001). Antibiotics and analgesics accounted for 43% and 42% of the total ED costs, respectively, while housing accounted for 46% of the total admission costs. Costs of ED visits not resulting in admissions were lower among HbSS/HbSβ0-thalassemia individuals with hydroxyurea MPR ≥65% compared with visits by patients with MPR <65% ($98.16/visit versus $182.46/visit, p = 0.0007). No difference in admission costs were observed relative to hydroxyurea use.

DISCUSSION

In a LMIC hematology-specialized center, VOCs accounted for most acute visits from patients with SCD, but costs were highest due to anemia exacerbation. Analgesics, antibiotics, and housing drove most expenses. Hydroxyurea may reduce ED costs among individuals with HbSS/HbSβ0-thalassemia but is dependent on adherence level.

Innovative Treatments for Rare Anemias

Rare anemias (RA) are mostly hereditary disorders with low prevalence and a broad spectrum of clinical severity, affecting different stages of erythropoiesis or red blood cell components. RA often remains underdiagnosed or misdiagnosed, and treatment options have been limited to supportive care for many years. During the last decades, the elucidation of the molecular mechanisms underlying several RA paved the way for developing new treatments. Innovative treatments other than supportive care and allogeneic bone marrow transplantation are currently in clinical trials for β-thalassemias, sickle cell disease (SCD), and congenital hemolytic anemias. Recently, luspatercept, an activin receptor ligand trap targeting ineffective erythropoiesis, has been approved as the first pharmacological treatment for transfusion-dependent β-thalassemia. L-glutamine, voxelotor, and crizanlizumab are new drugs approved SCD, targeting different steps of the complex pathophysiological mechanism. Gene therapy represents an innovative and encouraging strategy currently under evaluation in several RA and recently approved for β-thalassemia. Moreover, the advent of gene-editing technologies represents an additional option, mainly focused on correcting the defective gene or editing the expression of genes that regulate fetal hemoglobin synthesis. In this review, we aim to update the status of innovative treatments and the ongoing trials and discuss RA treatments’ future directions. Interestingly, several molecules that showed promising results for treating one of these disorders are now under evaluation in the others. In the near future, the management of RA will probably consist of polypharmacotherapy tailored to patients’ characteristics.

Research in Sickle Cell Disease: From Bedside to Bench to Bedside

Sickle cell disease (SCD) is an exemplar of bidirectional translational research, starting with a remarkable astute observation of the abnormally shaped red blood cells that motivated decades of bench research that have now translated into new drugs and genetic therapies. Introduction of hydroxyurea (HU) therapy, the only SCD-modifying treatment for >30 years and now standard care, was initiated through another clinical observation by a pediatrician. While the clinical efficacy of HU is primarily due to its fetal hemoglobin (HbF) induction, the exact mechanism of how it increases HbF remains not fully understood. Unraveling of the molecular mechanism of how HU increases HbF has provided insights on the development of new HbF-reactivating agents in the pipeline. HU has other salutary effects, reduction of cellular adhesion to the vascular endothelium and inflammation, and dissecting these mechanisms has informed bench-both cellular and animal-research for development of the 3 recently approved agents: endari, voxelotor, and crizanlizumab; truly, a bidirectional bench to bedside translation. Decades of research to understand the mechanisms of fetal to adult hemoglobin have also culminated in promising anti-sickling genetic therapies and the first-in-human studies of reactivating an endogenous (γ-globin) gene HBG utilizing innovative genomic approaches.

Sickle cell vaso-occlusion: The dialectic between red cells and white cells

The pathophysiology of sickle cell anemia, a hereditary hemoglobinopathy, has fascinated clinicians and scientists alike since its description over 100 years ago. A single gene mutation in the HBB gene results in the production of abnormal hemoglobin (Hb) S, whose polymerization when deoxygenated alters the physiochemical properties of red blood cells, in turn triggering pan-cellular activation and pathological mechanisms that include hemolysis, vaso-occlusion, and ischemia-reperfusion to result in the varied and severe complications of the disease. Now widely regarded as an inflammatory disease, in recent years attention has included the role of leukocytes in vaso-occlusive processes in view of the part that these cells play in innate immune processes, their inherent ability to adhere to the endothelium when activated, and their sheer physical and potentially obstructive size. Here, we consider the role of sickle red blood cell populations in elucidating the importance of adhesion vis-a-vis polymerization in vaso-occlusion, review the direct adhesion of sickle red cells to the endothelium in vaso-occlusive processes, and discuss how red cell- and leukocyte-centered mechanisms are not mutually exclusive. Given the initial clinical success of crizanlizumab, a specific anti-P selectin therapy, we suggest that it is appropriate to take a holistic approach to understanding and exploring the complexity of vaso-occlusive mechanisms and the adhesive roles of the varied cell types, including endothelial cells, platelets, leukocytes, and red blood cells.

P-Selectin Blockade in the Treatment of Painful Vaso-Occlusive Crises in Sickle Cell Disease: A Spotlight on Crizanlizumab

Microvascular vaso-occlusion driven pain crisis is the hallmark of sickle cell disease with profound morbidity and increased mortality. Selectins, most notably P-selectins have an integral role in this phenomenon. P-selection was first identified in 1989. In 2019, after 3 decades of basic, translational, and clinical work with this pathway, the US Food and Drug Administration approved a P-selectin antibody, crizanlizumab to reduce frequency of pain crisis in patients more than 16 years with sickle cell disease. We review the fundamentals of P-selectin pathobiology, P-selectin blocking agents, clinical data with the use of crizanlizumab and prospects of this novel class of drugs in the context of other treatments for painful vaso-occlusive episodes.

A Proposed Concept for Defective Mitophagy Leading to Late Stage Ineffective Erythropoiesis in Pyruvate Kinase Deficiency

Pyruvate kinase deficiency (PKD) is a rare congenital hemolytic anemia caused by mutations in the PKLR gene. Here, we review pathophysiological aspects of PKD, focusing on the interplay between pyruvate kinase (PK)-activity and reticulocyte maturation in the light of ferroptosis, an iron-dependent process of regulated cell death, and in particular its key player glutathione peroxidase 4 (GPX4). GPX4 plays an important role in mitophagy, the key step of peripheral reticulocyte maturation and GPX4 deficiency in reticulocytes results in a failure to fully mature. Mitophagy depends on lipid oxidation, which is under physiological conditions controlled by GPX4. Lack of GPX4 leads to uncontrolled auto-oxidation, which will disrupt autophagosome maturation and thereby perturb mitophagy. Based on our review, we propose a model for disturbed red cell maturation in PKD. A relative GPX4 deficiency occurs due to glutathione (GSH) depletion, as cytosolic L-glutamine is preferentially used in the form of α-ketoglutarate as fuel for the tricarboxylic acid (TCA) cycle at the expense of GSH production. The relative GPX4 deficiency will perturb mitophagy and, subsequently, results in failure of reticulocyte maturation, which can be defined as late stage ineffective erythropoiesis. Our hypothesis provides a starting point for future research into new therapeutic possibilities, which have the ability to correct the oxidative imbalance due to lack of GPX4.

Exploration of Structure-Activity Relationship of Aromatic Aldehydes Bearing Pyridinylmethoxy-Methyl Esters as Novel Antisickling Agents

Aromatic aldehydes elicit their antisickling effects primarily by increasing the affinity of hemoglobin (Hb) for oxygen (O₂). However, challenges related to weak potency and poor pharmacokinetic properties have hampered their development to treat sickle cell disease (SCD). Herein, we report our efforts to enhance the pharmacological profile of our previously reported compounds. These compounds showed enhanced effects on Hb modification, Hb-O₂ affinity, and sickling inhibition, with sustained pharmacological effects in vitro. Importantly, some compounds exhibited unusually high antisickling activity despite moderate effects on the Hb-O₂ affinity, which we attribute to an O₂-independent antisickling activity, in addition to the O₂-dependent activity. Structural studies are consistent with our hypothesis, which revealed the compounds interacting strongly with the polymer-stabilizing αF-helix could potentially weaken the polymer. In vivo studies with wild-type mice demonstrated significant pharmacologic effects. Our structure-based efforts have identified promising leads to be developed as novel therapeutic agents for SCD.

Efficacy and safety of recently approved drugs for sickle cell disease: a review of clinical trials

Sickle cell disease is prevalent in several parts of the world. Most hospitalizations of these patients are related to pain crisis episodes. Moreover, levels of hemoglobin are lower in sickle cell disease patients as compared with the general population. Complications related to sickle cell disease are managed with blood transfusions, hydroxyurea, and opioids. Despite these therapies, patients with sickle cell disease experience multiple pain crisis episodes leading to hospitalizations and end-organ damage. The US Food and Drug Administration has approved three new drugs-L-glutamine, voxelotor, and crizanlizumab-for the prophylaxis and treatment of complications related to sickle cell disease. This review was aimed at assessing the efficacy and safety of recently approved drugs for the treatment of sickle cell disease. A comprehensive search was made on PubMed and clinicaltrials.gov to look for clinical trials reporting the efficacy and safety of recently approved drugs for sickle cell disease. Based on the results of clinical trials, L-glutamine, voxelotor, and crizanlizumab were well tolerated by sickle cell disease patients. L-Glutamine and crizanlizumab reduced the number of sickle cell crisis episodes, while voxelotor improved the level of hemoglobin in sickle cell disease patients. These drugs were effective alone and in combination with hydroxyurea.

The CYB5R3c .350C>G and G6PD A alleles modify severity of anemia in malaria and sickle cell disease

Genetic modifiers of anemia in Plasmodium falciparum infection and sickle cell disease (SCD) are not fully known. Both conditions are associated with oxidative stress, hemolysis and anemia. The CYB5R3 gene encodes cytochrome b5 reductase 3, which converts methemoglobin to hemoglobin through oxidation of NADH. CYB5R3c.350C > G encoding CYB5R3T117S , the most frequent recognized African-specific polymorphism, does not have known functional significance, but its high allele frequency (23% in African Americans) suggests a selection advantage. Glucose-6-phosphate dehydrogenase (G6PD) is essential for protection from oxidants; its African-polymorphic X-linked A+ and A- alleles, and other variants with reduced activity, coincide with endemic malaria distribution, suggesting protection from lethal infection. We examined the association of CYB5R3c.350C > G with severe anemia (hemoglobin <5 g/dL) in the context of G6PD A+ and A- status among 165 Zambian children with malaria. CYB5R3c.350C > G offered protection against severe malarial anemia in children without G6PD deficiency (G6PD wild type or A+/A- heterozygotes) (odds ratio 0.29, P = .022) but not in G6PD A+ or A- hemizygotes/homozygotes. We also examined the relationship of CYB5R3c.350C > G with hemoglobin concentration among 267 children and 321 adults and adolescents with SCD in the US and UK and found higher hemoglobin in SCD patients without G6PD deficiency (β = 0.29, P = .022 children; β = 0.33, P = .004 adults). Functional studies in SCD erythrocytes revealed mildly lower activity of native CYB5R3T117S compared to wildtype CYB5R3 and higher NADH/NAD+ ratios. In conclusion, CYB5R3c.350C > G appears to ameliorate anemia severity in malaria and SCD patients without G6PD deficiency, possibly accounting for CYB5R3c.350C > G selection and its high prevalence.

Association of the 1q25 Diabetes-Specific Coronary Heart Disease Locus With Alterations of the γ-Glutamyl Cycle and Increased Methylglyoxal Levels in Endothelial Cells

A chromosome 1q25 variant (rs10911021) has been associated with coronary heart disease (CHD) in type 2 diabetes. In human umbilical vein endothelial cells (HUVECs), the risk allele "C" is associated with lower expression of the adjacent gene GLUL encoding glutamine synthase, converting glutamic acid to glutamine. To further investigate the mechanisms through which this locus affects CHD risk, we measured 35 intracellular metabolites involved in glutamic acid metabolism and the γ-glutamyl cycle in 62 HUVEC strains carrying different rs10911021 genotypes. Eight metabolites were positively associated with the risk allele (17-58% increase/allele copy, P = 0.046-0.002), including five γ-glutamyl amino acids, β-citryl-glutamate, N-acetyl-aspartyl-glutamate, and ophthalmate-a marker of γ-glutamyl cycle malfunction. Consistent with these findings, the risk allele was also associated with decreased glutathione-to-glutamate ratio (-9%, P = 0.012), decreased S-lactoylglutathione (-41%, P = 0.019), and reduced detoxification of the atherogenic compound methylglyoxal (+54%, P = 0.008). GLUL downregulation by shRNA caused a 40% increase in the methylglyoxal level, which was completely prevented by glutamine supplementation. In summary, we have identified intracellular metabolic traits associated with the 1q25 risk allele in HUVECs, including impairments of the γ-glutamyl cycle and methylglyoxal detoxification. Glutamine supplementation abolishes the latter abnormality, suggesting that such treatment may prevent CHD in 1q25 risk allele carriers.

Current and novel therapies for the prevention of vaso-occlusive crisis in sickle cell disease

Individuals with sickle cell disease (SCD) are living further into adulthood in high-resource countries. However, despite increased quantity of life, recurrent, acute painful episodes cause significant morbidity for affected individuals. These SCD-related painful episodes, also referred to as vaso-occlusive crises (VOCs), have multifactorial causes, and they often occur as a result of multicellular aggregation and vascular adherence of red blood cells, neutrophils, and platelets, leading to recurrent and unpredictable occlusion of the microcirculation. In addition to severe pain, long-term complications of vaso-occlusion may include damage to muscle and/or bone, in addition to vital organs such as the liver, spleen, kidneys, and brain. Severe pain associated with VOCs also has a substantial detrimental impact on quality of life for individuals with SCD, and is associated with increased health care utilization, financial hardship, and impairments in education and vocation attainment. Previous treatments have targeted primarily SCD symptom management, or were broad nontargeted therapies, and include oral or parenteral hydration, analgesics (including opioids), nonsteroidal anti-inflammatory agents, and various other types of nonpharmacologic pain management strategies to treat the pain associated with VOC. With increased understanding of the pathophysiology of VOCs, there are several new potential therapies that specifically target the pathologic process of vaso-occlusion. These new therapies may reduce cell adhesion and inflammation, leading to decreased incidence of VOCs and prevention of end-organ damage. In this review, we consider the benefits and limitations of current treatments to reduce the occurrence of VOCs in individuals with SCD and the potential impact of emerging treatments on future disease management.

Potential causal role of l-glutamine in sickle cell disease painful crises: A Mendelian randomization analysis

In a recent clinical trial, the metabolite l-glutamine was shown to reduce painful crises in sickle cell disease (SCD) patients. To support this observation and identify other metabolites implicated in SCD clinical heterogeneity, we profiled 129 metabolites in the plasma of 705 SCD patients. We tested correlations between metabolite levels and six SCD-related complications (painful crises, cholecystectomy, retinopathy, leg ulcer, priapism, aseptic necrosis) or estimated glomerular filtration rate (eGFR), and used Mendelian randomization (MR) to assess causality. We found a potential causal relationship between l-glutamine levels and painful crises (N = 1278, odds ratio (OR) [95% confidence interval] = 0.68 [0.52-0.89], P = 0.0048). In two smaller SCD cohorts (N = 299 and 406), the protective effect of l-glutamine was observed (OR = 0.82 [0.50-1.34]), although the MR result was not significant (P = 0.44). We identified 66 significant correlations between the levels of other metabolites and SCD-related complications or eGFR. We tested these correlations for causality using MR analyses and found no significant causal relationship. The baseline levels of quinolinic acid were associated with prospectively ascertained survival in SCD patients, and this effect was dependent on eGFR. Metabolomics provide a promising approach to prioritize small molecules that may serve as biomarkers or drug targets in SCD.

Decoding the role of SOD2 in sickle cell disease

Sickle cell disease (SCD) is an inherited hemoglobinopathy caused by a single point mutation in the β-globin gene. As a consequence, deoxygenated hemoglobin polymerizes triggering red blood cell sickling and hemolysis, vaso-occlusion, and ischemia/reperfusion. Allied to these pathologies is the overproduction of reactive oxygen species driven by hemoglobin Fenton chemistry and peroxidase reactions as well as by secondary activation of vascular oxidases, including NAD(P)H oxidase and xanthine oxidase. In addition, hypoxia, produced by sickle red blood cell occlusion, disrupts mitochondrial metabolism and generates excess superoxide through electron leak from the mitochondrial respiratory chain. Superoxide dismutase 2 (SOD2) is a mitochondrial-specific antioxidant enzyme that dismutates superoxide to hydrogen peroxide, which is then converted to water by catalase and glutathione peroxidase. In SCD, the antioxidant defense system is significantly diminished through decreased expression and activity levels of antioxidant enzymes, including superoxide dismutase, catalase, and glutathione peroxidase. From a translational perspective, genetic variants including a missense variant in SOD2 (valine to alanine at position 16) are present in 45% of people with African ancestry and are associated with increased sickle complications. While it is known that there is an imbalance between oxidative species and antioxidant defenses in SCD, much more investigation is warranted. This review summarizes our current understanding of antioxidant defense systems in SCD, particularly focused on SOD2, and provides insight into challenges and opportunities as the field moves forward.

NRF2 mediates γ-globin gene regulation through epigenetic modifications in a β-YAC transgenic mouse model

IMPACT STATEMENT

Sickle cell disease is an inherited hemoglobin disorder that affects over 100,000 people in the United States causing high morbidity and early mortality. Although new treatments were recently approved by the FDA, only one drug Hydroxyurea induces fetal hemoglobin expression to inhibit sickle hemoglobin polymerization in red blood cells. Our laboratory previously demonstrated the ability of the NRF2 activator, dimethyl fumarate to induce fetal hemoglobin in the sickle cell mouse model. In this study, we investigated molecular mechanisms of γ-globin gene activation by NRF2. We observed the ability of NRF2 to modulate chromatin structure in the human β-like globin gene locus of β-YAC transgenic mice during development. Furthermore, an NRF2/TET3 interaction regulates γ-globin gene DNA methylation. These findings provide potential new molecular targets for small molecule drug developed for treating sickle cell disease.

Systematic Review of Crizanlizumab: A New Parenteral Option to Reduce Vaso-occlusive Pain Crises in Patients with Sickle Cell Disease

Hydroxyurea, indicated for managing sickle cell anemia (SCA), and L-glutamine, indicated for treating sickle cell disease (SCD), were the only pharmacotherapeutic options in this patient population before the approval of crizanlizumab by the U.S. Food and Drug Administration in November 2019 to reduce vaso-occlusive crisis (VOC) frequency. This article reviews the evidence pertaining to crizanlizumab in SCD by searching records in Medline, Embase, and International Pharmaceutical Abstracts. Crizanlizumab, a P-selectin inhibitor, mitigates the microvascular vaso-occlusion in SCD. In the multicenter randomized double-blind SUSTAIN trial, a higher dose of crizanlizumab decreased the incidence of VOCs by 45% and prolonged the median time to the first and second VOC. A post hoc subgroup analysis demonstrated that the proportion of patients who had no VOC incidence during the study period was greater in the crizanlizumab group, and this benefit was consistent regardless of concomitant hydroxyurea use, prior categorized history of VOC frequency, or SCD genotype. Crizanlizumab had a safety profile comparable with placebo. Multiple ongoing clinical trials are trying to establish its roles in pediatric patients with SCD and its effects on alleviating other SCD-related complications. As the first parenteral option for SCD, providers need to formulate administration logistics to improve patients' access to crizanlizumab. Current available data suggest crizanlizumab is a promising agent to reduce VOC in patients with SCD.

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.

L-glutamine for sickle cell disease: Knight or pawn?

Oxidative stress is an important contributor to the pathophysiology of sickle cell disease. The pathways involved are complex and interlinked. L-glutamine is an amino acid with myriad roles in the body, including the synthesis of antioxidants, such as reduced glutathione and the cofactors NAD(H) and NADP(H), as well as nitric oxide—so it has therapeutic potential as an antioxidant. However, the relative impact of L-glutamine on the redox environment in red blood cells in sickle cell disease is not fully understood, and there are few therapeutic trials in sickle cell disease. Following the FDA approval of L-glutamine for sickle cell disease, more research is still needed to understand its clinical effects and role in therapy.

Ischemia-Reperfusion Injury in Sickle Cell Disease: From Basics to Therapeutics

Sickle cell disease (SCD) is one of the most common hereditary hemoglobinopathies worldwide, affecting almost 400,000 newborns globally each year. It is characterized by chronic hemolytic anemia and endothelial dysfunction, resulting in a constant state of disruption of the vascular system and leading to recurrent episodes of ischemia-reperfusion injury (I/RI) to multiple organ systems. I/RI is a fundamental vascular pathobiological paradigm and contributes to morbidity and mortality in a wide range of conditions, including myocardial infarction, stroke, acute kidney injury, and transplantation. I/RI is characterized by an initial restriction of blood supply to an organ, which can lead to ischemia, followed by the subsequent restoration of perfusion and concomitant reoxygenation. Recent advances in the pathophysiology of SCD have led to an understanding that many of the consequences of this disease can be explained by mechanisms associated with I/RI. The following review focuses on the evolving pathobiology of SCD, how various complications of SCD can be attributed to I/RI, and the role of timely therapeutic intervention(s) based on targeting mediators or pathways that influence I/R insult.

Emerging drugs in randomized controlled trials for sickle cell disease: are we on the brink of a new era in research and treatment?

Introduction: Sickle cell disease (SCD) is caused by a mutation in the HBB gene which is key for making a component of hemoglobin. The mutation leads to the formation of an abnormal hemoglobin molecule called sickle hemoglobin (HbS). SCD is a chronic, complex disease with a multiplicity of pathophysiological targets; it has high morbidity and mortality.Hydroxyurea has for many years been the only approved drug for SCD; hence, the development of new therapeutics is critical.Areas covered: This article offers an overview of the key studies of new therapeutic options for SCD. We searched the PubMed database and Cochrane Database of Systemic Reviews for agents in early phase clinic trials and preclinical development.Expert opinion: Although knowledge of SCD has progressed, patient survival and quality of life must be improved. Phase II and phase III clinical trials investigating pathophysiology-based novel agents show promising results in the clinical management of SCD acute events. The design of long-term clinical studies is necessary to fully understand the clinical impact of these new therapeutics on the natural history of the disease. Furthermore, the building of global collaborations will enhance the clinical management of SCD and the design of primary outcomes of future clinical trials.

Systematic Review of l-glutamine for Prevention of Vaso-occlusive Pain Crisis in Patients with Sickle Cell Disease

l-glutamine was approved by the U.S. Food and Drug Administration (FDA) for sickle cell disease (SCD) in 2017. A vaso-occlusive crisis (VOC) occurs in persons with SCD and is associated with acute pain episodes. This systematic review summarizes the evidence for l-glutamine in the prevention of VOC and associated pain in patients with SCD. Medline, Embase, and International Pharmaceutical Abstracts were searched for records reporting on l-glutamine use in persons with SCD. Eligibility criteria identified primary reports of investigations conducted in humans who were administered l-glutamine, reported on outcomes related to VOC or associated pain, published in English, and were available as full text. All relevant efficacy, safety, participant demographic data, and study method characteristics were extracted and documented. Risk-of-bias assessments were conducted using the Risk of Bias in Non-Randomized Studies-of Interventions (ROBINS-I) tool and the revised Cochrane risk-of-bias tool for randomized studies. Three studies assessing the effect of exogenous l-glutamine administration in patients with SCD met eligibility criteria: one prospective nonrandomized controlled study and two prospective randomized controlled trials. Rate of VOC and related hospitalizations were reduced in patients receiving l-glutamine, although some conflicting results were noted between studies. l-glutamine was generally well tolerated. Limitations of one or more of the eligible studies included small sample size, nonblinding, and study groups that differed at baseline. l-glutamine has limited high-quality evidence supporting its use. Although l-glutamine is FDA approved for the prevention of frequent episodes of VOC pain, only one randomized controlled trial has strong evidence to support this indication. Based on the results of a systematic review, l-glutamine may be considered for patients unable to receive hydroxyurea or in addition to hydroxyurea for reduction in VOC and associated pain.

New and emerging treatments for vaso-occlusive pain in sickle cell disease

Introduction: Acute pain from episodic vaso-occlusion (VOC) spans the lifespan of almost everyone with sickle cell disease (SCD), while additional chronic pain develops in susceptible individuals in early adolescences. Frequent acute pain with chronic pain causes significant physical and psychological morbidity, and frequent health-care utilization. Available pharmacologic therapies reduce acute pain frequency but few evidence-based therapies are available for chronic pain. Areas covered: An extensive PubMed literature search was performed with appropriate search criteria. The pathophysiology of acute pain from VOC in SCD is very complex with many events subsequent to sickle polymer formation. Sensitization of pain pathways and alterations of brain networks contributes to the experience of chronic pain. Numerous therapies targeting putative VOC mechanisms are in clinical trials, and show considerable promise. Alternative analgesic treatments for acute and chronic pain have been examined in small patient cohorts, but formal clinical trials are lacking. Expert opinion: Childhood is likely a critical window for prevention of acute and later chronic pain. New multimodal analgesic therapies are needed, particularly for chronic pain, and should be examined in clinical trials. Given the multifactorial nature of both pain and VOC, simultaneously targeting multiple mechanisms may be the optimal approach for effective preventive therapies.

Update in Outpatient General Internal Medicine: Practice-Changing Evidence Published in 2018

The expansive scope of general internal medicine makes it difficult to identify practice-changing medical literature. Clinical updates can be facilitated by synthesizing relevant articles and implications for practice. Six internal medicine physicians reviewed the titles and abstracts in the 7 general internal medicine clinical outpatient journals with the highest impact factor and relevance to the internal medicine outpatient physician: New England Journal of Medicine (NEJM), Lancet, Annals of Internal Medicine, Journal of the American Medical Association (JAMA), JAMA-Internal Medicine, British Medical Journal (BMJ), and Public Library of Science (PLoS) Medicine. The following collections of article synopses and databases were also reviewed: American College of Physicians Journal Club, NEJM Journal Watch, BMJ Evidence-Based medicine, McMaster/DynaMed Evidence Alerts, and Cochrane Reviews. A modified Delphi method was used to gain consensus on articles based on clinical relevance to outpatient Internal Medicine, potential impact on practice, and strength of evidence. Article qualities and importance were debated until consensus was reached. Clusters of articles pertinent to the same topic were considered together. In total, 7 practice-changing articles were included.

Pharmacokinetics and pharmacodynamics of voxelotor (GBT440) in healthy adults and patients with sickle cell disease

Aims

Voxelotor (previously GBT440) is a haemoglobin (Hb) modulator that increases Hb‐oxygen affinity, thereby reducing Hb polymerization and sickling of red blood cells (RBCs), being developed as a once‐daily oral drug to treat sickle cell disease (SCD). This first‐in‐human study evaluated the safety, tolerability, pharmacokinetics and pharmacodynamics of voxelotor in healthy volunteers and SCD patients.

Methods

A total of 40 healthy volunteers (100, 400, 1000, 2000 or 2800 mg) and 8 SCD patients (1000 mg) were randomly assigned to a single dose of voxelotor once daily (n = 6 per group) or placebo (n = 2 per group). Twenty‐four healthy volunteers received multiple doses of voxelotor once daily for 15 days (300, 600 or 900 mg, n = 6 per group) or placebo (n = 2 per group).

Results

Voxelotor was well tolerated and exhibited a linear pharmacokinetic profile and a half‐life ranging from 61 ± 7 h to 85 ± 7 h. High partitioning into the RBC compartment provides evidence of highly specific binding to Hb. Voxelotor exhibited a concentration‐dependent left‐shift of oxygen equilibrium curves. Percent Hb modification following 900 mg voxelotor for 15 days was 38 ± 9%. Terminal half‐life of voxelotor in SCD patients (50 ± 3 h) was shorter than in healthy volunteers. Evaluation of erythropoietin, exercise testing, and haematologic parameters were consistent with normal oxygen delivery during both rest and exercise.

Conclusion

This first‐in‐human study demonstrates voxelotor was well tolerated in SCD patients and healthy volunteers and established proof of mechanism on increasing Hb‐oxygen affinity.

Combined hydroxyurea and ETA receptor blockade reduces renal injury in the humanized sickle cell mouse

AIM

The objective of this study is to determine if ambrisentan (ET_A selective antagonist) and hydroxyurea (HU) treatment has a synergistic effect on renal injury in sickle cell nephropathy when compared to HU treatment alone. The premise of the study is based on recent studies showing that endothelin-1 (ET-1) contributes to the pathophysiology of nephropathy in sickle cell disease (SCD) and that ET_A receptor blockade improves renal function and protects against renal injury. Hydroxyurea (HU) is commonly prescribed for the treatment of SCD and has been shown to reduce renal injury in patients with SCD.

METHODS

Male 12-week-old humanized sickle mice (HbSS) and their genetic controls (HbAA) were treated with vehicle, HU, ambrisentan, or HU with ambrisentan for 2 weeks and renal structure and function were assessed.

RESULTS

Vehicle treated HbSS mice exhibited significant proteinuria compared to vehicle treated HbAA mice. HbSS mice also displayed significantly elevated plasma ET-1 concentrations and decreased urine osmolality compared to HbAA controls. Proteinuria was significantly lower in both HU and ambrisentan treated animals compared to vehicle treated HbSS mice; however, there was no additional improvement in HbSS mice treated with combined ambrisentan and HU. The combination of HU and ambrisentan resulted in significantly lower KIM-1 excretion, glomerular injury, and interstitial inflammation than HU alone.

CONCLUSION

These findings indicate that HU and ET_A receptor blockade produce similar reductions in renal injury in the humanized sickle mouse suggesting that both treatments may converge on the same mechanistic pathway.

Mechanisms of NRF2 activation to mediate fetal hemoglobin induction and protection against oxidative stress in sickle cell disease

IMPACT STATEMENT

Sickle cell disease (SCD) is a group of inherited blood disorders caused by mutations in the human β-globin gene, leading to the synthesis of abnormal hemoglobin S, chronic hemolysis, and oxidative stress. Inhibition of hemoglobin S polymerization by fetal hemoglobin holds the greatest promise for treating SCD. The transcription factor NRF2, is the master regulator of the cellular oxidative stress response and activator of fetal hemoglobin expression. In animal models, various small chemical molecules activate NRF2 and ameliorate the pathophysiology of SCD. This review discusses the mechanisms of NRF2 regulation and therapeutic strategies of NRF2 activation to design the treatment options for individuals with SCD.