1
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Youssry I, Ayad N. Sickle cell disease: combination new therapies vs. CRISPR-Cas9 potential and challenges - review article. Ann Hematol 2024; 103:2613-2619. [PMID: 37867187 DOI: 10.1007/s00277-023-05510-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 10/12/2023] [Indexed: 10/24/2023]
Abstract
In 2022, sickle cell disease (SCD) continues to affect the lives of millions of people, being one of the most frequently inherited blood disorders worldwide. Recently, several new therapies have been FDA approved for the treatment of SCD. The complexity of the pathophysiology of sickling has given opportunity to the evolution of several modalities of therapies. Nonetheless, the potential for complementary targeting of HbS polymerization, vasocclusion, and other inflammatory pathways remains controversial. None of these drugs can be considered a single curative line of treatment. With the advancement of CRISPR/Cas9 technology, autologous transplant of gene-edited hematopoietic stem cells could possibly provide a cure for most patients with SCD. The advantage of this approach over the conventional stem cell transplantation is that it decreases the need for immuno-suppressive drugs and the risk of graft-versus-host disease. In addition, recent technological advances can reduce the off-target effects, but long-term monitoring is needed to ensure the reliability of these methods in the clinical setting. This review explores the efficacy and safety of combination therapies and contrasting this alternative with the challenges that exist with sickle cell gene therapy using CRISPR.
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Affiliation(s)
- Ilham Youssry
- Pediatric Hematology and BMT Unit, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Nardeen Ayad
- Pediatric Hematology and BMT Unit, Faculty of Medicine, Cairo University, Cairo, Egypt.
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2
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Wood JC. Oxygen tug-of-war, voxelotor, and the brain. Blood 2024; 143:2113-2114. [PMID: 38780920 DOI: 10.1182/blood.2024024190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2024] Open
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3
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Xu JZ. Pyruvate kinase activators: targeting red cell metabolism in sickle cell disease. HEMATOLOGY. AMERICAN SOCIETY OF HEMATOLOGY. EDUCATION PROGRAM 2023; 2023:107-113. [PMID: 38066891 PMCID: PMC10727103 DOI: 10.1182/hematology.2023000467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Hemoglobin S (HbS) polymerization, red blood cell (RBC) sickling, chronic anemia, and vaso-occlusion are core to sickle cell disease (SCD) pathophysiology. Pyruvate kinase (PK) activators are a novel class of drugs that target RBC metabolism by reducing the buildup of the glycolytic intermediate 2,3-diphosphoglycerate (2,3-DPG) and increasing production of adenosine triphosphate (ATP). Lower 2,3-DPG level is associated with an increase in oxygen affinity and reduction in HbS polymerization, while increased RBC ATP may improve RBC membrane integrity and survival. There are currently 3 PK activators in clinical development for SCD: mitapivat (AG-348), etavopivat (FT-4202), and the second-generation molecule AG-946. Preclinical and clinical data from these 3 molecules demonstrate the ability of PK activators to lower 2,3-DPG levels and increase ATP levels in animal models and patients with SCD, as well as influence a number of potential pathways in SCD, including hemoglobin oxygen affinity, RBC sickling, RBC deformability, RBC hydration, inflammation, oxidative stress, hypercoagulability, and adhesion. Furthermore, early-phase clinical trials of mitapivat and etavopivat have demonstrated the safety and tolerability of PK activators in patients with SCD, and phase 2/3 trials for both drugs are ongoing. Additional considerations for this novel therapeutic approach include the balance between increasing hemoglobin oxygen affinity and tissue oxygen delivery, the cost and accessibility of these drugs, and the potential of multimodal therapy with existing and novel therapies targeting different disease mechanisms in SCD.
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Affiliation(s)
- Julia Z. Xu
- Division of Hematology/Oncology, Department of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
- Heart, Lung and Blood Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA, USA
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4
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Chowdhury FA, Colussi N, Sharma M, Wood KC, Xu JZ, Freeman BA, Schopfer FJ, Straub AC. Fatty acid nitroalkenes - Multi-target agents for the treatment of sickle cell disease. Redox Biol 2023; 68:102941. [PMID: 37907055 PMCID: PMC10632539 DOI: 10.1016/j.redox.2023.102941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 09/27/2023] [Accepted: 10/18/2023] [Indexed: 11/02/2023] Open
Abstract
Sickle cell disease (SCD) is a hereditary hematological disease with high morbidity and mortality rates worldwide. Despite being monogenic, SCD patients display a plethora of disease-associated complications including anemia, oxidative stress, sterile inflammation, vaso-occlusive crisis-related pain, and vasculopathy, all of which contribute to multiorgan dysfunction and failure. Over the past decade, numerous small molecule drugs, biologics, and gene-based interventions have been evaluated; however, only four disease-modifying drug therapies are presently FDA approved. Barriers regarding effectiveness, accessibility, affordability, tolerance, and compliance of the current polypharmacy-based disease-management approaches are challenging. As such, there is an unmet pharmacological need for safer, more efficacious, and logistically accessible treatment options for SCD patients. Herein, we evaluate the potential of small molecule nitroalkenes such as nitro-fatty acid (NO2-FA) as a therapy for SCD. These agents are electrophilic and exert anti-inflammatory and tissue repair effects through an ability to transiently post-translationally bind to and modify transcription factors, pro-inflammatory enzymes and cell signaling mediators. Preclinical and clinical studies affirm safety of the drug class and a murine model of SCD reveals protection against inflammation, fibrosis, and vascular dysfunction. Despite protective cardiac, renal, pulmonary, and central nervous system effects of nitroalkenes, they have not previously been considered as therapy for SCD. We highlight the pathways targeted by this drug class, which can potentially prevent the end-organ damage associated with SCD and contrast their prospective therapeutic benefits for SCD as opposed to current polypharmacy approaches.
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Affiliation(s)
- Fabliha A Chowdhury
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA; Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA, USA
| | - Nicole Colussi
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Malini Sharma
- University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Katherine C Wood
- Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA, USA
| | - Julia Z Xu
- Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA, USA; Division of Hematology and Oncology, Department of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Bruce A Freeman
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Francisco J Schopfer
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA; Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA, USA; Pittsburgh Liver Research Center (PLRC), University of Pittsburgh, Pittsburgh, PA, USA.
| | - Adam C Straub
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA; Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA, USA; Center for Microvascular Research, University of Pittsburgh, Pittsburgh, PA, USA.
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5
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Silva M, Faustino P. From Stress to Sick(le) and Back Again-Oxidative/Antioxidant Mechanisms, Genetic Modulation, and Cerebrovascular Disease in Children with Sickle Cell Anemia. Antioxidants (Basel) 2023; 12:1977. [PMID: 38001830 PMCID: PMC10669666 DOI: 10.3390/antiox12111977] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 10/30/2023] [Accepted: 11/02/2023] [Indexed: 11/26/2023] Open
Abstract
Sickle cell anemia (SCA) is a genetic disease caused by the homozygosity of the HBB:c.20A>T mutation, which results in the production of hemoglobin S (HbS). In hypoxic conditions, HbS suffers autoxidation and polymerizes inside red blood cells, altering their morphology into a sickle shape, with increased rigidity and fragility. This triggers complex pathophysiological mechanisms, including inflammation, cell adhesion, oxidative stress, and vaso-occlusion, along with metabolic alterations and endocrine complications. SCA is phenotypically heterogeneous due to the modulation of both environmental and genetic factors. Pediatric cerebrovascular disease (CVD), namely ischemic stroke and silent cerebral infarctions, is one of the most impactful manifestations. In this review, we highlight the role of oxidative stress in the pathophysiology of pediatric CVD. Since oxidative stress is an interdependent mechanism in vasculopathy, occurring alongside (or as result of) endothelial dysfunction, cell adhesion, inflammation, chronic hemolysis, ischemia-reperfusion injury, and vaso-occlusion, a brief overview of the main mechanisms involved is included. Moreover, the genetic modulation of CVD in SCA is discussed. The knowledge of the intricate network of altered mechanisms in SCA, and how it is affected by different genetic factors, is fundamental for the identification of potential therapeutic targets, drug development, and patient-specific treatment alternatives.
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Affiliation(s)
- Marisa Silva
- Departamento de Genética Humana, Instituto Nacional de Saúde Doutor Ricardo Jorge (INSA), Av. Padre Cruz, 1649-016 Lisboa, Portugal;
| | - Paula Faustino
- Departamento de Genética Humana, Instituto Nacional de Saúde Doutor Ricardo Jorge (INSA), Av. Padre Cruz, 1649-016 Lisboa, Portugal;
- Grupo Ecogenética e Saúde Humana, Instituto de Saúde Ambiental (ISAMB), Faculdade de Medicina, Universidade de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisboa, Portugal
- Laboratório Associado TERRA, Faculdade de Medicina, Universidade de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisboa, Portugal
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6
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Light J, Boucher M, Baskin-Miller J, Winstead M. Managing the Cerebrovascular Complications of Sickle Cell Disease: Current Perspectives. J Blood Med 2023; 14:279-293. [PMID: 37082003 PMCID: PMC10112470 DOI: 10.2147/jbm.s383472] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 03/31/2023] [Indexed: 04/22/2023] Open
Abstract
The importance of protecting brain function for people with sickle cell disease (SCD) cannot be overstated. SCD is associated with multiple cerebrovascular complications that threaten neurocognitive function and life. Without screening and preventive management, 11% of children at 24% of adults with SCD have ischemic or hemorrhagic strokes. Stroke screening in children with SCD is well-established using transcranial Doppler ultrasound (TCD). TCD velocities above 200 cm/s significantly increase the risk of stroke, which can be prevented using chronic red blood cell (RBC) transfusion. RBC transfusion is also the cornerstone of acute stroke management and secondary stroke prevention. Chronic transfusion requires long-term management of complications like iron overload. Hydroxyurea can replace chronic transfusions for primary stroke prevention in a select group of patients or in populations where chronic transfusions are not feasible. Silent cerebral infarction (SCI) is even more common than stroke, affecting 39% of children and more than 50% of adults with SCD; management of SCI is individualized and includes careful neurocognitive evaluation. Hematopoietic stem cell transplant prevents cerebrovascular complications, despite the short- and long-term risks. Newer disease-modifying agents like voxelotor and crizanlizumab, as well as gene therapy, may treat cerebrovascular complications, but these approaches are investigational.
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Affiliation(s)
- Jennifer Light
- Pediatric Hematology-Oncology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Maria Boucher
- Pediatric Hematology-Oncology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Jacquelyn Baskin-Miller
- Pediatric Hematology-Oncology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Mike Winstead
- Pediatric Hematology-Oncology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Correspondence: Mike Winstead, Division of Pediatric Hematology-Oncology, University of North Carolina at Chapel Hill, 101 Manning Drive, Chapel Hill, NC, USA, Tel +1 919-966-1178, Fax +1 919-966-7629, Email
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7
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Affiliation(s)
- H Franklin Bunn
- From the Division of Hematology, Brigham and Women's Hospital, Harvard Medical School, Boston
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8
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Barriteau CM, Badawy SM. Practical Guidance for the Use of Voxelotor in the Management of Sickle Cell Disease. J Blood Med 2022; 13:739-745. [PMID: 36471678 PMCID: PMC9719266 DOI: 10.2147/jbm.s362222] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 11/18/2022] [Indexed: 09/10/2024] Open
Abstract
Sickle cell disease (SCD) is one of the most common inherited blood disorders. Deoxygenated hemoglobin S (HbS) polymerizes and causes anemia and various end organ effects. Voxelotor acts by increasing HbS oxygen affinity, decreasing anemia and hemolysis. Voxelotor is approved for use in individuals with SCD age 4 years and older. Phase 3 trials demonstrated an increase in hemoglobin levels and a decrease in markers of hemolysis; however, data or benefits related to clinical and quality of life outcomes are relatively limited and varied across different studies. This review summarizes the published clinical trials and research studies focused on the use of voxelotor in SCD to provide an evidence-based practical guide for hematology providers on its utilization in clinical settings, including physicians and independent licensed practitioners.
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Affiliation(s)
- Christina M Barriteau
- Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
- Division of Hematology, Oncology and Stem Cell Transplant, Ann & Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL, USA
| | - Sherif M Badawy
- Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
- Division of Hematology, Oncology and Stem Cell Transplant, Ann & Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL, USA
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9
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Osunkwo I, Anderson A, Brown RC, Shah N, Estepp JH. A clinician's view of voxelotor. Br J Haematol 2022; 199:616-618. [PMID: 36113859 DOI: 10.1111/bjh.18455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 08/17/2022] [Accepted: 08/30/2022] [Indexed: 11/30/2022]
Affiliation(s)
- Ifeyinwa Osunkwo
- Non-Malignant Hematology Section, The Levine Cancer Institute and Atrium Health, Charlotte, North Carolina, USA
| | - Alan Anderson
- Prisma Health Comprehensive SCD Program, University of South Carolina School of Medicine, Greenville, South Carolina, USA
| | - R Clark Brown
- Aflac Cancer and Blood Disorders Center, Children's Healthcare of Atlanta, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Nirmish Shah
- Department of Medicine, Duke University, Durham, North Carolina, USA
| | - Jeremie H Estepp
- Departments of Global Pediatric Medicine and Hematology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
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10
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Hansen S, Wood DK. Simultaneous quantification of blood rheology and oxygen saturation to evaluate affinity-modifying therapies in sickle cell disease. LAB ON A CHIP 2022; 22:4141-4150. [PMID: 36134535 PMCID: PMC10165883 DOI: 10.1039/d2lc00623e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Sickle cell blood demonstrates oxygen-dependent flow behavior as a result of HbS polymerization during hypoxia, and these rheological changes provide a biophysical metric that can be used to quantify the pathological behavior of the blood. Relating these rheological changes directly to hemoglobin oxygen saturation would improve our understanding of SCD pathogenesis and the potential effects of therapeutic drugs. Towards this end, we have developed a microfluidic platform capable of spectrophotometric quantification of Hb-O2 saturation and simultaneous evaluation of the accompanying rheological changes in SCD blood flow. We demonstrated the ability to measure changes in Hb-O2 affinity and a restoration of oxygen-independent blood flow behavior after incubation with voxelotor, an oxygen affinity modifying drug approved for use in SCD. We also identified regimes in Hb-O2 saturation where the effects of HbS polymerization begin to take effect in contributing to pathological flow behavior, independent of voxelotor treatment. In contrast, incubation with voxelotor recovered oxygen-dependent blood flow over a range of PO2, providing a framework for understanding voxelotor's therapeutic effect in lowering the PO2 at which the requisite Hb-O2 saturation is reached to observe pathological blood flow. These results help explain the mechanistic effects of voxelotor and show the potential of this platform to identify affinity-modifying compounds and evaluate their therapeutic effect on blood flow.
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Affiliation(s)
- Scott Hansen
- Department of Biomedical Engineering, University of Minnesota, Minneapolis 55409, USA.
| | - David K Wood
- Department of Biomedical Engineering, University of Minnesota, Minneapolis 55409, USA.
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11
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Brewin JN, Nardo-Marino A, Stuart-Smith S, El Hoss S, Hanneman A, Strouboulis J, Menzel S, Gibson JS, Rees DC. The pleiotropic effects of α-thalassemia on HbSS and HbSC sickle cell disease: Reduced erythrocyte cation co-transport activity, serum erythropoietin, and transfusion burden, do not translate into increased survival. Am J Hematol 2022; 97:1275-1285. [PMID: 35802781 PMCID: PMC9543574 DOI: 10.1002/ajh.26652] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2022] [Revised: 06/30/2022] [Accepted: 07/05/2022] [Indexed: 01/24/2023]
Abstract
α-Thalassemia is one of the most important genetic modulators of sickle cell disease (SCD). Both beneficial and detrimental effects have been described previously. We use a 12-year data set on a large cohort of patients with HbSS (n = 411) and HbSC (n = 146) to examine a wide range of these clinical and laboratory associations. Our novel findings are that α-thalassemia strongly reduces erythrocyte potassium chloride co-transporter (KCC) activity in both HbSS and HbSC (p = .035 and p = .00045 respectively), suggesting a novel mechanism through which α-thalassemia induces a milder phenotype by reducing red cell cation loss. This may be particularly important in HbSC where reduction in mean cell hemoglobin concentration is not seen and where KCC activity has previously been found to correlate with disease severity. Additionally, we show that α-thalassemia not only increases hemoglobin in patients with HbSS (p = .0009) but also reduces erythropoietin values (p = .0005), demonstrating a measurable response to improved tissue oxygenation. We confirm the reno-protective effect of α-thalassemia in patients with HbSS, with reduced proteinuria (p = .003) and demonstrate a novel association with increased serum sodium (p = .0004) and reduced serum potassium values (p = 5.74 × 10-10 ). We found patients with α-thalassemia had a reduced annualized transfusion burden in both HbSS and HbSC, but α-thalassemia had no impact on annualized admission rates in either group. Finally, in a larger cohort, we report a median survival of 62 years in patients with HbSS (n = 899) and 80 years in those with HbSC (n = 240). α-thalassemia did not influence survival in HbSS, but a nonsignificant trend was seen in those with HbSC.
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Affiliation(s)
- John N Brewin
- Department of Haematological Medicine, King's College Hospital, London, UK.,Comprehensive Cancer Centre, School of Cancer and Pharmaceutical Sciences, King's College London, London, UK
| | - Amina Nardo-Marino
- Department of Haematological Medicine, King's College Hospital, London, UK.,Comprehensive Cancer Centre, School of Cancer and Pharmaceutical Sciences, King's College London, London, UK.,Centre for Haemoglobinopathies, Department of Haematology, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Sara Stuart-Smith
- Department of Haematological Medicine, King's College Hospital, London, UK
| | - Sara El Hoss
- Comprehensive Cancer Centre, School of Cancer and Pharmaceutical Sciences, King's College London, London, UK
| | - Anke Hanneman
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - John Strouboulis
- Comprehensive Cancer Centre, School of Cancer and Pharmaceutical Sciences, King's College London, London, UK
| | - Stephan Menzel
- Comprehensive Cancer Centre, School of Cancer and Pharmaceutical Sciences, King's College London, London, UK
| | - John S Gibson
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - David C Rees
- Department of Haematological Medicine, King's College Hospital, London, UK.,Comprehensive Cancer Centre, School of Cancer and Pharmaceutical Sciences, King's College London, London, UK
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12
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Vunnam N, Hansen S, Williams DC, Been M, Lo CH, Pandey AK, Paulson CN, Rohde JA, Thomas DD, Sachs JN, Wood DK. Fluorescence Lifetime Measurement of Prefibrillar Sickle Hemoglobin Oligomers as a Platform for Drug Discovery in Sickle Cell Disease. Biomacromolecules 2022; 23:3822-3830. [PMID: 35944154 PMCID: PMC9472799 DOI: 10.1021/acs.biomac.2c00671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 07/22/2022] [Indexed: 11/30/2022]
Abstract
The molecular origin of sickle cell disease (SCD) has been known since 1949, but treatments remain limited. We present the first high-throughput screening (HTS) platform for discovering small molecules that directly inhibit sickle hemoglobin (HbS) oligomerization and improve blood flow, potentially overcoming a long-standing bottleneck in SCD drug discovery. We show that at concentrations far below the threshold for nucleation and rapid polymerization, deoxygenated HbS forms small assemblies of multiple α2β2 tetramers. Our HTS platform leverages high-sensitivity fluorescence lifetime measurements that monitor these temporally stable prefibrillar HbS oligomers. We show that this approach is sensitive to compounds that inhibit HbS polymerization with or without modulating hemoglobin oxygen binding affinity. We also report the results of a pilot small-molecule screen in which we discovered and validated several novel inhibitors of HbS oligomerization.
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Affiliation(s)
- Nagamani Vunnam
- Department
of Biomedical Engineering, University of
Minnesota, Minneapolis, Minnesota 55455, United States
| | - Scott Hansen
- Department
of Biomedical Engineering, University of
Minnesota, Minneapolis, Minnesota 55455, United States
| | - Dillon C. Williams
- Department
of Biomedical Engineering, University of
Minnesota, Minneapolis, Minnesota 55455, United States
| | - MaryJane
Olivia Been
- Department
of Biomedical Engineering, University of
Minnesota, Minneapolis, Minnesota 55455, United States
| | - Chih Hung Lo
- Department
of Biomedical Engineering, University of
Minnesota, Minneapolis, Minnesota 55455, United States
| | - Anil K. Pandey
- Department
of Biomedical Engineering, University of
Minnesota, Minneapolis, Minnesota 55455, United States
| | - Carolyn N. Paulson
- Department
of Biomedical Engineering, University of
Minnesota, Minneapolis, Minnesota 55455, United States
| | - John A. Rohde
- Department
of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - David D. Thomas
- Department
of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Jonathan N. Sachs
- Department
of Biomedical Engineering, University of
Minnesota, Minneapolis, Minnesota 55455, United States
| | - David K. Wood
- Department
of Biomedical Engineering, University of
Minnesota, Minneapolis, Minnesota 55455, United States
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13
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Quinn CT, Ware RE. New therapeutics for children with sickle cell disease: A time for celebration, caution, or both? Pediatr Blood Cancer 2022; 69:e29805. [PMID: 35686738 DOI: 10.1002/pbc.29805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 05/14/2022] [Indexed: 11/06/2022]
Affiliation(s)
- Charles T Quinn
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.,Division of Hematology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Russell E Ware
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.,Division of Hematology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Global Health Center, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
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14
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Torres LS, Asada N, Weiss MJ, Trumpp A, Suda T, Scadden DT, Ito K. Recent advances in "sickle and niche" research - Tribute to Dr. Paul S Frenette. Stem Cell Reports 2022; 17:1509-1535. [PMID: 35830837 PMCID: PMC9287685 DOI: 10.1016/j.stemcr.2022.06.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Revised: 06/08/2022] [Accepted: 06/09/2022] [Indexed: 10/27/2022] Open
Abstract
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.
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Affiliation(s)
- Lidiane S Torres
- Ruth L. and David S. Gottesman Institute for Stem Cell and Regenerative Medicine Research, Albert Einstein College of Medicine, Bronx, New York, NY 10461, USA; Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, NY 10461, USA; Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, NY 10461, USA
| | - Noboru Asada
- Department of Hematology and Oncology, Okayama University Hospital, Okayama 700-8558, Japan
| | - Mitchell J Weiss
- Department of Hematology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Andreas Trumpp
- Division of Stem Cells and Cancer, German Cancer Research Center (DKFZ) and DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany; Heidelberg Institute for Stem Cell Technology and Experimental Medicine (HI-STEM gGmbH), 69120 Heidelberg, Germany; Faculty of Biosciences, Heidelberg University, 69117 Heidelberg, Germany; German Cancer Consortium (DKTK), 69120 Heidelberg, Germany
| | - Toshio Suda
- Cancer Science Institute of Singapore, National University of Singapore, Singapore, Singapore; International Research Center for Medical Sciences, Kumamoto University, Kumamoto, Japan
| | - David T Scadden
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA, USA; Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA; Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Keisuke Ito
- Ruth L. and David S. Gottesman Institute for Stem Cell and Regenerative Medicine Research, Albert Einstein College of Medicine, Bronx, New York, NY 10461, USA; Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, NY 10461, USA; Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, NY 10461, USA; Montefiore Einstein Cancer Center, Albert Einstein College of Medicine, Bronx, New York, NY 10461, USA; Einstein Diabetes Research Center, Albert Einstein College of Medicine, Bronx, NY, USA.
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15
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Nagalapuram V, Kanter J. Multi-organ dysfunction secondary to abrupt discontinuation of voxelotor in a patient with severe sickle cell disease. Am J Hematol 2022; 97:E318-E320. [PMID: 35702869 DOI: 10.1002/ajh.26631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 05/20/2022] [Accepted: 05/26/2022] [Indexed: 01/20/2023]
Affiliation(s)
- Vishnu Nagalapuram
- Department of Internal Medicine, The University of Alabama at Birmingham, Montgomery, Alabama, USA
| | - Julie Kanter
- Division of Hematology and Oncology, The University of Alabama at Birmingham, Birmingham, Alabama, USA
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16
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Steinberg MH. Fetal hemoglobin in β hemoglobinopathies: Is enough too much? Am J Hematol 2022; 97:676-678. [PMID: 35253929 DOI: 10.1002/ajh.26518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Accepted: 03/01/2022] [Indexed: 11/10/2022]
Affiliation(s)
- Martin H Steinberg
- Department of Medicine, Division of Hematology and Medical Oncology Boston University School of Medicine Boston Massachusetts 02118 USA
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17
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Revisiting anemia in sickle cell disease and finding the balance with therapeutic approaches. Blood 2022; 139:3030-3039. [PMID: 35587865 DOI: 10.1182/blood.2021013873] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 12/05/2021] [Indexed: 11/20/2022] Open
Abstract
Chronic hemolytic anemia and intermittent acute pain episodes are the 2 hallmark characteristics of sickle cell disease (SCD). Anemia in SCD not only signals a reduction of red cell mass and oxygen delivery, but also ongoing red cell breakdown and release of cell-free hemoglobin, which together contribute to a number of pathophysiological responses and play a key role in the pathogenesis of cumulative multiorgan damage. However, although anemia is clearly associated with many detrimental outcomes, it may also have an advantage in SCD in lowering risks of potential viscosity-related complications. Until recently, clinical drug development for SCD has predominantly targeted a reduction in the frequency of vaso-occlusive crises as an endpoint, but increasingly, more attention is being directed toward addressing the contribution of chronic anemia to poor outcomes in SCD. This article aims to explore the complex pathophysiology and mechanisms of anemia in SCD, as well as the need to balance the benefits of raising hemoglobin levels with the potential risks of increasing blood viscosity, in the context of the current therapeutic landscape for anemia in SCD.
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18
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Schroeder P, Fulzele K, Forsyth S, Ribadeneira MD, Guichard S, Wilker E, Marshall CG, Drake A, Fessler R, Konstantinidis DG, Seu KG, Kalfa TA. Etavopivat, a Pyruvate Kinase Activator in Red Blood Cells, for the Treatment of Sickle Cell Disease. J Pharmacol Exp Ther 2022; 380:210-219. [PMID: 35031585 DOI: 10.1124/jpet.121.000743] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 12/21/2021] [Indexed: 11/22/2022] Open
Abstract
Etavopivat is an investigational, oral, small molecule activator of erythrocyte pyruvate kinase (PKR) in development for the treatment of sickle cell disease (SCD) and other hemoglobinopathies. PKR activation is proposed to ameliorate the sickling of SCD red blood cells (RBC) through multiple mechanisms, including reduction of 2,3-diphosphoglycerate (2,3-DPG), which consequently increases hemoglobin (Hb)-oxygen affinity; increased binding of oxygen reduces HbS polymerization and sickling. In addition, PKR activation increases adenosine triphosphate (ATP) produced via glycolytic flux, which helps preserve membrane integrity and RBC deformability. We evaluated the pharmacodynamic response to etavopivat in non-human primates (NHP) and in healthy human subjects, and the effects in RBC from patients with SCD after ex vivo treatment with etavopivat. A single dose of etavopivat decreased 2,3-DPG in NHP and healthy subjects. Hb-oxygen affinity was significantly increased in healthy subjects after 24 hours. Following daily dosing of etavopivat over 5 consecutive days in NHP, ATP was increased by 38% from baseline. Etavopivat increased Hb-oxygen affinity and reduced sickling in RBC collected from SCD patients with either HbSS or HbSC disease. Collectively, these results demonstrate the ability of etavopivat to decrease 2,3-DPG and increase ATP, resulting in increased Hb-oxygen affinity and improved sickle RBC function. Etavopivat is currently being evaluated in clinical trials for the treatment of SCD. ClinicalTrials.gov identifier: NCT03815695 Significance Statement Etavopivat-a small molecule activator of the glycolytic enzyme erythrocyte pyruvate kinase -decreased 2,3-diphosphoglycerate in red blood cells (RBC) from non-human primates and healthy subjects and significantly increased hemoglobin (Hb)-oxygen affinity in healthy subjects. Using ex vivo RBC from donors with sickle cell disease (SCD) (HbSS or HbSC genotype), etavopivat increased Hb-oxygen affinity and reduced sickling under deoxygenation. Etavopivat shows promise as a treatment for SCD, that potentially might reduce vaso-occlusion and improve anemia.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Rose Fessler
- Cincinnati Children's Hospital Medical Center, United States
| | | | - Katie G Seu
- Cincinnati Children's Hospital Medical Center, United States
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19
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Quercetin Completely Ameliorates Hypoxia-Reoxygenation-Induced Pathophysiology Severity in NY1DD Transgenic Sickle Mice: Intrinsic Mild Steady State Pathophysiology of the Disease in NY1DD Is Also Reversed. Biomolecules 2021; 11:biom11101473. [PMID: 34680105 PMCID: PMC8533533 DOI: 10.3390/biom11101473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 10/01/2021] [Accepted: 10/02/2021] [Indexed: 11/29/2022] Open
Abstract
The vaso-occlusive crisis (VOC) is a major complication of sickle cell disease (SCD); thus, strategies to ameliorate vaso-occlusive episodes are greatly needed. We evaluated the therapeutic benefits of quercetin in a SCD transgenic sickle mouse model. This disease model exhibited very mild disease pathophysiology in the steady state. The severity of the disease in the NY1DD mouse was amplified by subjecting mice to 18 h of hypoxia followed by 3 h of reoxygenation. Quercetin (200 mg/kg body weight) administered to hypoxia challenged NY1DD mice in a single intraperitoneal (i.p.) dose at the onset of reoxygenation completely ameliorated all hypoxia reoxygenation (H/R)-induced pathophysiology. Additionally, it ameliorated the mild intrinsic steady state pathophysiology. These results are comparable with those seen with semisynthetic supra plasma expanders. In control mice, C57BL/6J, hypoxia reoxygenation-induced vaso-occlusion was at significantly lower levels than in NY1DD mice, reflecting the role of sickle hemoglobin (HbS) in inducing vaso-occlusion; however, the therapeutic benefits from quercetin were significantly muted. We suggest that these findings represent a unique genotype of the NY1DD mice, i.e., the presence of high oxygen affinity red blood cells (RBCs) with chimeric HbS, composed of mouse α-chain and human βS-chain, as well as human α-chain and mouse β-chain (besides HbS). The anti-anemia therapeutic benefits from high oxygen affinity RBCs in these mice exert disease severity modifications that synergize with the therapeutic benefits of quercetin. Combining the therapeutic benefits of high oxygen affinity RBCs generated in situ by chemical or genetic manipulation with the therapeutic benefits of antiadhesive therapies is a novel approach to treat sickle cell patients with severe pathophysiology.
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20
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Increased oxygen affinity: to have and to hold. Blood 2021; 138:1094-1095. [PMID: 34591098 DOI: 10.1182/blood.2021013243] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 07/21/2021] [Indexed: 12/27/2022] Open
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21
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Treatment of sickle cell disease by increasing oxygen affinity of hemoglobin. Blood 2021; 138:1172-1181. [PMID: 34197597 DOI: 10.1182/blood.2021012070] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 06/30/2021] [Indexed: 11/20/2022] Open
Abstract
The issue of treating sickle cell disease with drugs that increase hemoglobin oxygen affinity has come to the fore with the FDA approval in 2019 of voxelotor, the only anti-sickling drug approved since hydroxyurea in 1998. Voxelotor reduces sickling by increasing the concentration of the non-polymerizing, high oxygen affinity R (oxy) conformation of HbS. Treatment of sickle cell patients with voxelotor increases Hb levels and decreases indicators of hemolysis, but with no indication as yet that it reduces the frequency of pain episodes. Here we use the allosteric model of Monod, Wyman, and Changeux to simulate whole blood oxygen dissociation curves and red cell sickling in the absence and presence of voxelotor under the in vivo conditions of rapid oxygen pressure decreases. Our modeling agrees with experiments using a new robust assay, which shows the very large, expected decrease in sickling from the drug. The modeling indicates, however, that the increase in oxygen delivery from reduced sickling is largely offset by the increase in oxygen affinity. The net result is that the drug increases overall oxygen delivery only at the very lowest oxygen pressures. Reduction of sickling does, however, mitigate against red cell damage and explains the observed decrease in hemolysis. More importantly, our modeling of in vivo oxygen dissociation, sickling, and oxygen delivery suggests that drugs that increase fetal hemoglobin or decrease MCHC, should be more therapeutically effective than drugs that increase oxygen affinity.
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22
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Salinas Cisneros G, Thein SL. Research in Sickle Cell Disease: From Bedside to Bench to Bedside. Hemasphere 2021; 5:e584. [PMID: 34095767 PMCID: PMC8171370 DOI: 10.1097/hs9.0000000000000584] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 04/17/2021] [Indexed: 01/25/2023] Open
Abstract
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.
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Affiliation(s)
- Gabriel Salinas Cisneros
- Sickle Cell Branch, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
- Division of Hematology and Oncology, Children’s National Medical Center, Washington, District of Columbia, USA
| | - Swee Lay Thein
- Sickle Cell Branch, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
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23
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Henry ER, Harper J, Glass KE, Metaferia B, Louis JM, Eaton WA. MWC allosteric model explains unusual hemoglobin-oxygen binding curves from sickle cell drug binding. Biophys J 2021; 120:2543-2551. [PMID: 33932439 PMCID: PMC8390878 DOI: 10.1016/j.bpj.2021.04.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2020] [Revised: 02/22/2021] [Accepted: 04/21/2021] [Indexed: 11/26/2022] Open
Abstract
An oxygen-affinity-modifying drug, voxelotor, has very recently been approved by the FDA for treatment of sickle cell disease. The proposed mechanism of action is by preferential binding of the drug to the R quaternary conformation, which cannot copolymerize with the T conformation to form sickle fibers. Here, we report widely different oxygen dissociation and oxygen association curves for normal blood in the presence of voxelotor and interpret the results in terms of the allosteric model of Monod, Wyman, and Changeux with the addition of drug binding. The model does remarkably well in quantitatively explaining a complex data set with just the addition of drug binding and dissociation rates for the R and T conformations. Whereas slow dissociation of the drug from R results in time-independent dissociation curves, the changing association curves result from slow dissociation of the drug from T, as well as extremely slow binding of the drug to T. By calculating true equilibrium curves from the model parameters, we show that there would be a smaller decrease in oxygen delivery from the left shift in the dissociation curve caused by drug binding if drug binding and dissociation for both R and T were rapid. Our application of the Monod, Wyman, and Changeux model demonstrates once more its enormous power in explaining many different kinds of experimental results for hemoglobin. It should also be helpful in analyzing oxygen binding and in vivo delivery in future investigations of oxygen-affinity-modifying drugs for sickle cell disease.
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Affiliation(s)
- Eric R Henry
- National Institutes of Health, Bethesda, Maryland
| | - Julia Harper
- National Institutes of Health, Bethesda, Maryland
| | | | | | - John M Louis
- National Institutes of Health, Bethesda, Maryland
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24
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Inusa BPD, Casale M, Campbell A, Archer N. Will the changing therapeutic landscape meet the needs of patients with sickle cell disease? LANCET HAEMATOLOGY 2021; 8:e306-e307. [PMID: 33838114 DOI: 10.1016/s2352-3026(21)00098-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 03/16/2021] [Indexed: 11/18/2022]
Affiliation(s)
- Baba Psalm Duniya Inusa
- Paediatric Haemotology, Evelina London Children's Hospital, Guy's and St Thomas' NHS Foundation Trust, London SE1 7EH, UK.
| | - Maddalena Casale
- Università degli Studi della Campania Luigi Vanvitelli, Dipartimento della Donna, del Bambino e di Chirurgia Generale e Specialistica Napoli, Naples, Italy
| | - Andrew Campbell
- Department of Hematology, Children's National Hospital, Washington, DC, USA; Children's National Hospital, George Washington University School of Medicine, Fredericksburg, VA, USA
| | - Natasha Archer
- Department of Pediatric Hematology and Oncology, Dana-Farber/Boston Children's Cancer and Blood Disorders Center, Harvard Medical School, Boston, MA, USA
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25
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Glaros AK, Razvi R, Shah N, Zaidi AU. Voxelotor: alteration of sickle cell disease pathophysiology by a first-in-class polymerization inhibitor. Ther Adv Hematol 2021; 12:20406207211001136. [PMID: 33796238 PMCID: PMC7983433 DOI: 10.1177/20406207211001136] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Accepted: 02/15/2021] [Indexed: 12/16/2022] Open
Abstract
Sickle cell disease, despite its recognition as a severely debilitating genetic condition affecting hundreds of thousands of neonates throughout the world each year, was not a target of pharmaceutical research focus for most of its 100-year existence in the medical consciousness. This has changed in recent years as many novel therapeutics are currently under investigation, with three new disease-modifying drugs achieving FDA approval in the last 4 years. One of these drugs, voxelotor, is especially encouraging as an inhibitor of sickling for its ability to safely improve the chronic hemolytic anemia of sickle cell disease. This was demonstrated during all clinical phases of investigation by an average improvement in hemoglobin of greater than 1 g/dL, as well as statistically significant improvements in established markers of hemolysis. While anemia itself represents a potential cause of morbidity, it is more importantly a marker of the hemolysis known to cause the long-term vascular and organ damage that makes sickle cell disease so debilitating and frequently fatal early in life. Given the recency of the approval, there has not been sufficient long-term follow-up to demonstrate improvement in the chronic sequelae of sickle cell disease as a result of voxelotor-induced improvements in hemolytic anemia. There is hope, however, based on the experience with hydroxyurea improving morbidity and mortality via reductions in sickling and improved rheology, that voxelotor may have similar long-term benefits by positively manipulating the kinetics of hemoglobin polymerization. This review aims to summarize the targeted pathobiology of sickle cell disease, the mechanism of action of voxelotor, and the safety and efficacy data from preclinical to late clinical stage investigations of this long-awaited medication, in the hopes of better informing the decision-making process behind prescribing or not prescribing it for patients in need of intervention.
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Affiliation(s)
- Alexander K. Glaros
- Central Michigan University, Mt. Pleasant, MI, USA
- Children’s Hospital of Michigan, Detroit, MI, USA
| | - Reza Razvi
- Children’s Hospital of Michigan, Detroit, MI, USA
| | | | - Ahmar U. Zaidi
- Central Michigan University, Mt. Pleasant, MI, USA
- Children’s Hospital of Michigan, Detroit, MI, USA
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26
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Abdulmalik O, Darwish NHE, Muralidharan-Chari V, Taleb MA, Mousa SA. Sulfated non-anticoagulant heparin derivative modifies intracellular hemoglobin, inhibits cell sickling in vitro, and prolongs survival of sickle cell mice under hypoxia. Haematologica 2021; 107:532-540. [PMID: 33567814 PMCID: PMC8804574 DOI: 10.3324/haematol.2020.272393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Indexed: 11/09/2022] Open
Abstract
Sickle cell disease (SCD) is an autosomal recessive genetic disease caused by a single point mutation, resulting in abnormal sickle hemoglobin (HbS). During hypoxia or dehydration, HbS polymerizes to form insoluble aggregates and induces sickling of red blood cells, which increases the adhesiveness of the cells, thereby altering the rheological properties of the blood, and triggers inflammatory responses, leading to hemolysis and vaso-occlusive crises. Unfractionated heparin and low-molecular weight heparins have been suggested as treatments to relieve coagulation complications in SCD. However, they are associated with bleeding complications after repeated dosing. An alternative sulfated non-anticoagulant heparin derivative (S-NACH) was previously reported to have no to low systemic anticoagulant activity and no bleeding side effects, and it interfered with P-selectin-dependent binding of sickle cells to endothelial cells, with concomitant decrease in the levels of adhesion biomarkers in SCD mice. S-NACH has been further engineered and structurally enhanced to bind with and modify HbS to inhibit sickling directly, thus employing a multimodal approach. Here, we show that S-NACH can: (i) directly engage in Schiff-base reactions with HbS to decrease red blood cell sickling under both normoxia and hypoxia in vitro, (ii) prolong the survival of SCD mice under hypoxia, and (iii) regulate the altered steady state levels of pro- and anti-inflammatory cytokines. Thus, our proof-of-concept, in vitro and in vivo preclinical studies demonstrate that the multimodal S-NACH is a highly promising candidate for development into an improved and optimized alternative to low-molecular weight heparins for the treatment of patients with SCD.
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Affiliation(s)
- Osheiza Abdulmalik
- Division of Hematology, the Children's Hospital of Philadelphia, Philadelphia, PA
| | - Noureldien H E Darwish
- The Pharmaceutical Research Institute, Albany College of Pharmacy and Health Sciences, Rensselaer, NY, USA; Clinical Pathology (Hematology Section), Faculty of Medicine, Mansoura University, Mansoura
| | | | - Maii Abu Taleb
- The Pharmaceutical Research Institute, Albany College of Pharmacy and Health Sciences, Rensselaer, NY
| | - Shaker A Mousa
- The Pharmaceutical Research Institute, Albany College of Pharmacy and Health Sciences, Rensselaer, NY, USA; Vascular Vison Pharmaceuticals Co., 7 University Place, Rensselaer, NY.
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27
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Pace BS, Starlard-Davenport A, Kutlar A. Sickle cell disease: progress towards combination drug therapy. Br J Haematol 2021; 194:240-251. [PMID: 33471938 DOI: 10.1111/bjh.17312] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 12/11/2020] [Accepted: 12/14/2020] [Indexed: 12/23/2022]
Abstract
Dr. John Herrick described the first clinical case of sickle cell anaemia (SCA) in the United States in 1910. Subsequently, four decades later, Ingram and colleagues characterized the A to T substitution in DNA producing the GAG to GTG codon and replacement of glutamic acid with valine in the sixth position of the βS -globin chain. The establishment of Comprehensive Sickle Cell Centers in the United States in the 1970s was an important milestone in the development of treatment strategies and describing the natural history of sickle cell disease (SCD) comprised of genotypes including homozygous haemoglobin SS (HbSS), HbSβ0 thalassaemia, HbSC and HbSβ+ thalassaemia, among others. Early drug studies demonstrating effective treatments of HbSS and HbSβ0 thalassaemia, stimulated clinical trials to develop disease-specific therapies to induce fetal haemoglobin due to its ability to block HbS polymerization. Subsequently, hydroxycarbamide proved efficacious in adults with SCA and was Food and Drug Administration (FDA)-approved in 1998. After two decades of hydroxycarbamide use for SCD, there continues to be limited clinical acceptance of this chemotherapy drug, providing the impetus for investigators and pharmaceutical companies to develop non-chemotherapy agents. Investigative efforts to determine the role of events downstream of deoxy-HbS polymerization, such as endothelial cell activation, cellular adhesion, chronic inflammation, intravascular haemolysis and nitric oxide scavenging, have expanded drug targets which reverse the pathophysiology of SCD. After two decades of slow progress in the field, since 2018 three new drugs were FDA-approved for SCA, but research efforts to develop treatments continue. Currently over 30 treatment intervention trials are in progress to investigate a wide range of agents acting by complementary mechanisms, providing the rationale for ushering in the age of effective and safe combination drug therapy for SCD. Parallel efforts to develop curative therapies using haematopoietic stem cell transplant and gene therapy provide individuals with SCD multiple treatment options. We will discuss progress made towards drug development and potential combination drug therapy for SCD with the standard of care hydroxycarbamide.
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Affiliation(s)
- Betty S Pace
- Department of Pediatrics, Augusta University, Augusta, GA, USA.,Department of Biochemistry and Molecular Biology, Augusta University, Augusta, GA, USA
| | - Athena Starlard-Davenport
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, 38163, USA
| | - Abdullah Kutlar
- Department of Medicine, Center for Blood Disorders, Augusta University, Augusta, GA, USA
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28
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VZHE-039, a novel antisickling agent that prevents erythrocyte sickling under both hypoxic and anoxic conditions. Sci Rep 2020; 10:20277. [PMID: 33219275 PMCID: PMC7679387 DOI: 10.1038/s41598-020-77171-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 11/06/2020] [Indexed: 12/20/2022] Open
Abstract
Sickle cell disease (SCD) results from a hemoglobin (Hb) mutation βGlu6 → βVal6 that changes normal Hb (HbA) into sickle Hb (HbS). Under hypoxia, HbS polymerizes into rigid fibers, causing red blood cells (RBCs) to sickle; leading to numerous adverse pathological effects. The RBC sickling is made worse by the low oxygen (O2) affinity of HbS, due to elevated intra-RBC concentrations of the natural Hb effector, 2,3-diphosphoglycerate. This has prompted the development of Hb modifiers, such as aromatic aldehydes, with the intent of increasing Hb affinity for O2 with subsequent prevention of RBC sickling. One such molecule, Voxelotor was recently approved by U.S. FDA to treat SCD. Here we report results of a novel aromatic aldehyde, VZHE-039, that mimics both the O2-dependent and O2-independent antisickling properties of fetal hemoglobin. The latter mechanism of action—as elucidated through crystallographic and biological studies—is likely due to disruption of key intermolecular contacts necessary for stable HbS polymer formation. This dual antisickling mechanism, in addition to VZHE-039 metabolic stability, has translated into significantly enhanced and sustained pharmacologic activities. Finally, VZHE-039 showed no significant inhibition of several CYPs, demonstrated efficient RBC partitioning and high membrane permeability, and is not an efflux transporter (P-gp) substrate.
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29
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Allosteric control of hemoglobin S fiber formation by oxygen and its relation to the pathophysiology of sickle cell disease. Proc Natl Acad Sci U S A 2020; 117:15018-15027. [PMID: 32527859 PMCID: PMC7334536 DOI: 10.1073/pnas.1922004117] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The pathology of sickle cell disease is caused by polymerization of the abnormal hemoglobin S upon deoxygenation in the tissues to form fibers in red cells, causing them to deform and occlude the circulation. Drugs that allosterically shift the quaternary equilibrium from the polymerizing T quaternary structure to the nonpolymerizing R quaternary structure are now being developed. Here we update our understanding on the allosteric control of fiber formation at equilibrium by showing how the simplest extension of the classic quaternary two-state allosteric model of Monod, Wyman, and Changeux to include tertiary conformational changes provides a better quantitative description. We also show that if fiber formation is at equilibrium in vivo, the vast majority of cells in most tissues would contain fibers, indicating that it is unlikely that the disease would be survivable once the nonpolymerizing fetal hemoglobin has been replaced by adult hemoglobin S at about 1 y after birth. Calculations of sickling times, based on a recently discovered universal relation between the delay time prior to fiber formation and supersaturation, show that in vivo fiber formation is very far from equilibrium. Our analysis indicates that patients survive because the delay period allows the majority of cells to escape the small vessels of the tissues before fibers form. The enormous sensitivity of the duration of the delay period to intracellular hemoglobin composition also explains why sickle trait, the heterozygous condition, and the compound heterozygous condition of hemoglobin S with pancellular hereditary persistence of fetal hemoglobin are both relatively benign conditions.
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30
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Salinas Cisneros G, Thein SL. Recent Advances in the Treatment of Sickle Cell Disease. Front Physiol 2020; 11:435. [PMID: 32508672 PMCID: PMC7252227 DOI: 10.3389/fphys.2020.00435] [Citation(s) in RCA: 95] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 04/08/2020] [Indexed: 12/31/2022] Open
Abstract
Sickle cell anemia (SCA) was first described in the Western literature more than 100 years ago. Elucidation of its molecular basis prompted numerous biochemical and genetic studies that have contributed to a better understanding of its pathophysiology. Unfortunately, the translation of such knowledge into developing treatments has been disproportionately slow and elusive. In the last 10 years, discovery of BCL11A, a major γ-globin gene repressor, has led to a better understanding of the switch from fetal to adult hemoglobin and a resurgence of efforts on exploring pharmacological and genetic/genomic approaches for reactivating fetal hemoglobin as possible therapeutic options. Alongside therapeutic reactivation of fetal hemoglobin, further understanding of stem cell transplantation and mixed chimerism as well as gene editing, and genomics have yielded very encouraging outcomes. Other advances have contributed to the FDA approval of three new medications in 2017 and 2019 for management of sickle cell disease, with several other drugs currently under development. In this review, we will focus on the most important advances in the last decade.
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Affiliation(s)
- Gabriel Salinas Cisneros
- Sickle Cell Branch, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, United States.,Division of Hematology and Oncology, Children's National Medical Center, Washington, DC, United States
| | - Swee L Thein
- Sickle Cell Branch, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, United States
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31
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Han J, Saraf SL, Gordeuk VR. Systematic Review of Voxelotor: A First-in-Class Sickle Hemoglobin Polymerization Inhibitor for Management of Sickle Cell Disease. Pharmacotherapy 2020; 40:525-534. [PMID: 32343424 DOI: 10.1002/phar.2405] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 03/18/2020] [Accepted: 03/26/2020] [Indexed: 11/08/2022]
Abstract
Voxelotor, a sickle hemoglobin polymerization inhibitor, was approved by the U.S. Food and Drug Administration to treat sickle cell disease (SCD) in November 2019. This article reviews published data about voxelotor treatment of SCD based on a search of MEDLINE, Embase, and International Pharmaceutical Abstracts. In a phase I/II trial, voxelotor demonstrated a dose-dependent pharmacokinetic and pharmacodynamic response and was well tolerated in healthy volunteers and patients with SCD. In a multi-center, randomized, double-blind, phase III trial (HOPE trial), a significantly higher percentage of patients randomized to voxelotor had increased hemoglobin (> 1 g/dl from baseline) compared to placebo. A greater reduction of hemolytic markers was also observed in the voxelotor-treated group, whereas the incidence of adverse effects was comparable. Three case series or reports also demonstrated the efficacy and safety of voxelotor use in a limited number of SCD patients in the real-world situation, although one patient with SCD, severe anemia, and a history of autoantibody-mediated hemolysis failed to respond to voxelotor. An ongoing trial (HOPE-KIDS) is designed to establish the use of voxelotor in younger pediatric patients with SCD. There is a theoretical concern that voxelotor may impair oxygen delivery, due to modification of the oxygen affinity of hemoglobin, which needs to be further evaluated. As a first-in-class hemoglobin modulator, voxelotor offers a new treatment option targeting the root cause of SCD.
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Affiliation(s)
- Jin Han
- Department of Pharmacy Practice, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois, USA.,Comprehensive Sickle Cell Center, Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA.,Center for Pharmacoepidemiology and Pharmacoeconomic Research, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Santosh L Saraf
- Comprehensive Sickle Cell Center, Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Victor R Gordeuk
- Comprehensive Sickle Cell Center, Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA
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Hansen S, Wood DK, Higgins JM. 5-(Hydroxymethyl)furfural restores low-oxygen rheology of sickle trait blood in vitro. Br J Haematol 2019; 188:985-993. [PMID: 31889311 DOI: 10.1111/bjh.16251] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 08/16/2019] [Indexed: 12/27/2022]
Abstract
Sickle cell trait (SCT) is the benign heterozygous carrier state for the sickle variant of the HBB gene. Most of the ~300 million people with SCT worldwide will not experience any significant complications. However, accumulating evidence finds SCT associated with increased risk for the common conditions of chronic kidney disease and venous thromboembolism, and severe but rare renal medullary carcinoma and exercise-induced rhabdomyolysis. The mechanism is uncertain, but probably involves pathological rheology of SCT blood in regions of low oxygen tension, resulting from sickle haemoglobin polymerization in SCT red cells and leading to reduced blood flow and further tissue hypoxia and damage. Here, we used an in vitro microfluidic flow system to study the oxygen-dependent rheology of SCT blood and show that 5-(hydroxymethyl)furfural, a natural breakdown product of glucose and fructose-containing foods, such as fruit juices, can reduce the effects of hypoxia on SCT blood rheology in vitro, restoring near-normal flow velocities at very low oxygen. While opinions regarding the clinical significance of the risks associated with SCT are still evolving, these results suggest that a compound present in some food may provide a potential approach for managing risks that may be associated with SCT.
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Affiliation(s)
- Scott Hansen
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - David K Wood
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - John M Higgins
- Center for Systems Biology, Department of Pathology, Massachusetts General Hospital, Boston, MA, USA.,Department of Systems Biology, Harvard Medical School, Boston, MA, USA
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Saunthararajah Y. Targeting sickle cell disease root-cause pathophysiology with small molecules. Haematologica 2019; 104:1720-1730. [PMID: 31399526 PMCID: PMC6717594 DOI: 10.3324/haematol.2018.207530] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 07/09/2019] [Indexed: 12/28/2022] Open
Abstract
The complex, frequently devastating, multi-organ pathophysiology of sickle cell disease has a single root cause: polymerization of deoxygenated sickle hemoglobin. A logical approach to disease modification is, therefore, to interdict this root cause. Ideally, such interdiction would utilize small molecules that are practical and accessible for worldwide application. Two types of such small molecule strategies are actively being evaluated in the clinic. The first strategy intends to shift red blood cell precursor hemoglobin manufacturing away from sickle hemoglobin and towards fetal hemoglobin, which inhibits sickle hemoglobin polymerization by a number of mechanisms. The second strategy intends to chemically modify sickle hemoglobin directly in order to inhibit its polymerization. Important lessons have been learnt from the pre-clinical and clinical evaluations to date. Open questions remain, but this review summarizes the valuable experience and knowledge already gained, which can guide ongoing and future efforts for molecular mechanism-based, practical and accessible disease modification of sickle cell disease.
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Affiliation(s)
- Yogen Saunthararajah
- Department of Hematology and Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, OH, USA
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Chai Y, Bush AM, Coloigner J, Nederveen AJ, Tamrazi B, Vu C, Choi S, Coates TD, Lepore N, Wood JC. White matter has impaired resting oxygen delivery in sickle cell patients. Am J Hematol 2019; 94:467-474. [PMID: 30697803 PMCID: PMC6874897 DOI: 10.1002/ajh.25423] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 12/27/2018] [Accepted: 01/22/2019] [Indexed: 12/13/2022]
Abstract
Although modern medical management has lowered overt stroke occurrence in patients with sickle cell disease (SCD), progressive white matter (WM) damage remains common. It is known that cerebral blood flow (CBF) increases to compensate for anemia, but sufficiency of cerebral oxygen delivery, especially in the WM, has not been systematically investigated. Cerebral perfusion was measured by arterial spin labeling in 32 SCD patients (age range: 10-42 years old, 14 males, 7 with HbSC, 25 HbSS) and 25 age and race-matched healthy controls (age range: 15-45 years old, 10 males, 12 with HbAS, 13 HbAA); 8/24 SCD patients were receiving regular blood transfusions and 14/24 non-transfused SCD patients were taking hydroxyurea. Imaging data from control subjects were used to calculate maps for CBF and oxygen delivery in SCD patients and their T-score maps. Whole brain CBF was increased in SCD patients with a mean T-score of 0.5 and correlated with lactate dehydrogenase (r2 = 0.58, P < 0.0001). When corrected for oxygen content and arterial saturation, whole brain and gray matter (GM) oxygen delivery were normal in SCD, but WM oxygen delivery was 35% lower than in controls. Age and hematocrit were the strongest predictors for WM CBF and oxygen delivery in patients with SCD. There was spatial co-localization between regions of low oxygen delivery and WM hyperintensities on T2 FLAIR imaging. To conclude, oxygen delivery is preserved in the GM of SCD patients, but is decreased throughout the WM, particularly in areas prone to WM silent strokes.
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Affiliation(s)
- Yaqiong Chai
- Department of Biomedical Engineering, University of Southern California Engineering, School, Los Angeles, California
| | - Adam M. Bush
- Department of Radiology, Stanford, University, California
| | - Julie Coloigner
- Univ Rennes, CNRS, Inria, Inserm, IRISA UMR 6074, VISAGES - ERL U 1228, Rennes, France
| | - Aart J. Nederveen
- Department of Radiology and Nuclear Medicine, Academic Medical Center, Amsterdam, The Netherlands
| | - Benita Tamrazi
- Department of Radiology and Nuclear Medicine, Children’s Hospital Los Angeles,Los Angeles, California
| | - Chau Vu
- Department of Biomedical Engineering, University of Southern California Engineering, School, Los Angeles, California
| | - Soyoung Choi
- Neuroscience Graduate Program, University of Southern California, Los Angeles, California
- Division of Cardiology, Children’s Hospital Los Angeles, Los Angeles, California
| | - Thomas D. Coates
- Section of Hematology, Children’s Hospital Los Angeles, Los Angeles, California
| | - Natasha Lepore
- Department of Biomedical Engineering, University of Southern California Engineering, School, Los Angeles, California
- Department of Radiology and Nuclear Medicine, Children’s Hospital Los Angeles,Los Angeles, California
| | - John C. Wood
- Department of Biomedical Engineering, University of Southern California Engineering, School, Los Angeles, California
- Division of Cardiology, Children’s Hospital Los Angeles, Los Angeles, California
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Telen MJ, Malik P, Vercellotti GM. Therapeutic strategies for sickle cell disease: towards a multi-agent approach. Nat Rev Drug Discov 2019; 18:139-158. [PMID: 30514970 PMCID: PMC6645400 DOI: 10.1038/s41573-018-0003-2] [Citation(s) in RCA: 111] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
For over 100 years, clinicians and scientists have been unravelling the consequences of the A to T substitution in the β-globin gene that produces haemoglobin S, which leads to the systemic manifestations of sickle cell disease (SCD), including vaso-occlusion, anaemia, haemolysis, organ injury and pain. However, despite growing understanding of the mechanisms of haemoglobin S polymerization and its effects on red blood cells, only two therapies for SCD - hydroxyurea and L-glutamine - are approved by the US Food and Drug Administration. Moreover, these treatment options do not fully address the manifestations of SCD, which arise from a complex network of interdependent pathophysiological processes. In this article, we review efforts to develop new drugs targeting these processes, including agents that reactivate fetal haemoglobin, anti-sickling agents, anti-adhesion agents, modulators of ischaemia-reperfusion and oxidative stress, agents that counteract free haemoglobin and haem, anti-inflammatory agents, anti-thrombotic agents and anti-platelet agents. We also discuss gene therapy, which holds promise of a cure, although its widespread application is currently limited by technical challenges and the expense of treatment. We thus propose that developing systems-oriented multi-agent strategies on the basis of SCD pathophysiology is needed to improve the quality of life and survival of people with SCD.
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Affiliation(s)
- Marilyn J Telen
- Division of Hematology, Department of Medicine and Duke Comprehensive Sickle Cell Center, Duke University, Durham, NC, USA.
| | - Punam Malik
- Division of Experimental Hematology and Cancer Biology and the Division of Hematology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Gregory M Vercellotti
- Division of Hematology, Oncology and Transplantation, Department of Medicine, University of Minnesota, Minneapolis, MN, USA
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Estepp JH. Voxelotor (GBT440), a first-in-class hemoglobin oxygen-affinity modulator, has promising and reassuring preclinical and clinical data. Am J Hematol 2018; 93:326-329. [PMID: 29352729 DOI: 10.1002/ajh.25042] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 01/17/2018] [Indexed: 11/07/2022]
Affiliation(s)
- Jeremie H Estepp
- Department of Hematology, St. Jude Children's Research Hospital, Memphis, Tennessee
- Department of Pathology, St. Jude Children's Research Hospital, Memphis, Tennessee
- St. Jude Children's Research Hospital Graduate School of Biomedical Sciences, Clinical Research Instructor, Memphis, Tennessee
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