Search

Abstract: Serial cardiovascular magnetic resonance evaluation of children and young adults with SCD who underwent hematopoietic cell transplantation showed mean ECV, representing diffuse myocardial fibrosis, decreased 3.4% from baseline to 12 months posttransplantation. This trial was registered at www.clinicaltrials.gov as #NCT04362293., (© 2024 American Society of Hematology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.)

Competing Interests: AS has received consultant fees from Spotlight Therapeutics, Medexus, Vertex Pharmaceuticals, Sangamo Therapeutics, and Editas Medicine. He is a medical monitor for a Resource for Clinical Investigations in Blood and Marrow Transplantation Conditioning SCID Infants Diagnosed Early clinical trial for which he receives financial compensation. He has also received research funding from CRISPR Therapeutics and honoraria from Vindico Medical Education. AS is the St Jude Children's Research Hospital site principal investigator of clinical trials for genome editing of sickle cell disease sponsored by Vertex Pharmaceuticals/CRISPR Therapeutics (NCT03745287), Novartis Pharmaceuticals (NCT04443907), and Beam Therapeutics (NCT05456880). The industry sponsors provide funding for the clinical trial, which includes salary support paid to AS's institution. AS has no direct financial interest in these therapies. AS is supported by a grant (1U01HL163983) from the National Institutes of Health/National Heart, Lung, and Blood Institute. The content of this Comment is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. TDJ has participated as an advisory board member and received consulting fees from Bluebird Bio and Vertex Pharmaceuticals. She is a medical monitor for BMT CTN 2001 GRASP study for which she receives compensation. TDJ is the Stanford site principal investigator of clinical trials for genome editing sponsored by Beam Therapeutics (NCT04443907). TDJ has no direct financial interest in this therapy. We thank Keith A Laycock for scientific editing of the Comment. We also thank Jennifer Adair, Fred Hutch Cancer Center, Jane Hankins, St Jude Children's Research Hospital, and Zainab Garba-Sani, Stanford University and NHS England, for offering critical insights on the topic and reviewing an early draft of the manuscript.

Sickle cell disease (SCD) decreases the oxygen-carrying capacity of red blood cells. Children with SCD have reduced/restricted cerebral blood flow, resulting in neurocognitive deficits. Hydroxyurea is the standard treatment for SCD; however, whether hydroxyurea influences such effects is unclear. A key area of SCD-associated neurocognitive impairment is working memory, which is implicated in other cognitive and academic skills. The neural correlates of working memory can be tested using n-back tasks. We analyzed functional magnetic resonance imaging (fMRI) data of patients with SCD (20 hydroxyurea-treated patients and 11 controls, aged 7-18 years) while they performed n-back tasks. Blood-oxygenation level-dependent (BOLD) signals were assessed during working memory processing at 2 time points: before hydroxyurea treatment and ~1 year after treatment was initiated. Neurocognitive measures were also assessed at both time points. Our results suggested that working memory was stable in the treated group. We observed a treatment-by-time interaction in the right cuneus and angular gyrus for the 2- >0-back contrast. Searchlight-pattern classification of the 2 time points of the 2-back tasks identified greater changes in the pattern and magnitude of BOLD signals, especially in the posterior regions of the brain, in the control group than in the treated group. In the control group at 1-year follow-up, 2-back BOLD signals increased across time points in several clusters (e.g., right inferior temporal lobe, right angular gyrus). We hypothesize that these changes resulted from increased cognitive effort during working memory processing in the absence of hydroxyurea. In the treated group, 0- to 2-back BOLD signals in the right angular gyrus and left cuneus increased continuously with increasing working memory load, potentially related to a broader dynamic range in response to task difficulty and cognitive effort. These findings suggest that hydroxyurea treatment helps maintain working memory function in SCD., Competing Interests: Dr. Akshay Sharma has received consultant fees from Spotlight Therapeutics, Medexus Inc., Vertex Pharmaceuticals, Sangamo Therapeutics, and Editas Medicine. He has also received research funding from CRISPR Therapeutics and honoraria from Vindico Medical Education. Dr. Sharma is the St. Jude site principal investigator of clinical trials for genome editing for SCD sponsored by Vertex Pharmaceuticals/CRISPR Therapeutics (NCT03745287), Novartis Pharmaceuticals (NCT04443907), and Beam Therapeutics (NCT05456880). The industry sponsors provide funding for the clinical trial, which includes salary support paid to our institution. Dr. Sharma has no direct financial interest in these therapies. Dr. Andrew M. Heitzer has received consulting fees from Global Blood Therapeutics. Neither Dr. Sharma nor Dr. Heitzer is an employee of any commercial entity. All other authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. This does not alter our adherence to PLoS ONE policies on sharing data and materials., (Copyright: © 2024 Lai et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Exagamglogene autotemcel (exa-cel) is a nonviral cell therapy designed to reactivate fetal hemoglobin synthesis by means of ex vivo clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 gene editing of autologous CD34+ hematopoietic stem and progenitor cells (HSPCs) at the erythroid-specific enhancer region of BCL11A ., Methods: We conducted a phase 3, single-group, open-label study of exa-cel in patients 12 to 35 years of age with sickle cell disease who had had at least two severe vaso-occlusive crises in each of the 2 years before screening. CD34+ HSPCs were edited with the use of CRISPR-Cas9. Before the exa-cel infusion, patients underwent myeloablative conditioning with pharmacokinetically dose-adjusted busulfan. The primary end point was freedom from severe vaso-occlusive crises for at least 12 consecutive months. A key secondary end point was freedom from inpatient hospitalization for severe vaso-occlusive crises for at least 12 consecutive months. The safety of exa-cel was also assessed., Results: A total of 44 patients received exa-cel, and the median follow-up was 19.3 months (range, 0.8 to 48.1). Neutrophils and platelets engrafted in each patient. Of the 30 patients who had sufficient follow-up to be evaluated, 29 (97%; 95% confidence interval [CI], 83 to 100) were free from vaso-occlusive crises for at least 12 consecutive months, and all 30 (100%; 95% CI, 88 to 100) were free from hospitalizations for vaso-occlusive crises for at least 12 consecutive months (P<0.001 for both comparisons against the null hypothesis of a 50% response). The safety profile of exa-cel was generally consistent with that of myeloablative busulfan conditioning and autologous HSPC transplantation. No cancers occurred., Conclusions: Treatment with exa-cel eliminated vaso-occlusive crises in 97% of patients with sickle cell disease for a period of 12 months or more. (CLIMB SCD-121; ClinicalTrials.gov number, NCT03745287.)., (Copyright © 2024 Massachusetts Medical Society.)

Background: Sickle cell disease is caused by a defect in the β-globin subunit of adult hemoglobin. Sickle hemoglobin polymerizes under hypoxic conditions, producing deformed red cells that hemolyze and cause vaso-occlusion that results in progressive organ damage and early death. Elevated fetal hemoglobin levels in red cells protect against complications of sickle cell disease. OTQ923, a clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9-edited CD34+ hematopoietic stem- and progenitor-cell (HSPC) product, has a targeted disruption of the HBG1 and HBG2 (γ-globin) gene promoters that increases fetal hemoglobin expression in red-cell progeny., Methods: We performed a tiling CRISPR-Cas9 screen of the HBG1 and HBG2 promoters by electroporating CD34+ cells obtained from healthy donors with Cas9 complexed with one of 72 guide RNAs, and we assessed the fraction of fetal hemoglobin-immunostaining erythroblasts (F cells) in erythroid-differentiated progeny. The gRNA resulting in the highest level of F cells (gRNA-68) was selected for clinical development. We enrolled participants with severe sickle cell disease in a multicenter, phase 1-2 clinical study to assess the safety and adverse-effect profile of OTQ923., Results: In preclinical experiments, CD34+ HSPCs (obtained from healthy donors and persons with sickle cell disease) edited with CRISPR-Cas9 and gRNA-68 had sustained on-target editing with no off-target mutations and produced high levels of fetal hemoglobin after in vitro differentiation or xenotransplantation into immunodeficient mice. In the study, three participants received autologous OTQ923 after myeloablative conditioning and were followed for 6 to 18 months. At the end of the follow-up period, all the participants had engraftment and stable induction of fetal hemoglobin (fetal hemoglobin as a percentage of total hemoglobin, 19.0 to 26.8%), with fetal hemoglobin broadly distributed in red cells (F cells as a percentage of red cells, 69.7 to 87.8%). Manifestations of sickle cell disease decreased during the follow-up period., Conclusions: CRISPR-Cas9 disruption of the HBG1 and HBG2 gene promoters was an effective strategy for induction of fetal hemoglobin. Infusion of autologous OTQ923 into three participants with severe sickle cell disease resulted in sustained induction of red-cell fetal hemoglobin and clinical improvement in disease severity. (Funded by Novartis Pharmaceuticals; ClinicalTrials.gov number, NCT04443907.)., (Copyright © 2023 Massachusetts Medical Society.)

Competing Interests: Declaration of interests MRA has received grants or contracts with Novartis, Pfizer, Global Blood Therapeutics, and Forma Therapeutics; and participated in Data Safety Monitoring Boards or Advisory Boards for Vertex, GBT, Forma, Novartis, and Aggios. BA has participated in Data Safety Monitoring Boards or Advisory Boards for Agios, Aruvant, bluebird bio, CRISPR, Accordant (CVS), Emmaus, Forma Therapeutics, Fulcrum, Global Blood Therapeutics, Hemanext, Novartis, NovoNordisk, and Vertex. RF has received grants from the European Horizon 2020 and Horizon Europe schemes and a contract with Global Blood Therapeutics; received consulting fees from Novartis and Global Blood Therapeutics; received honoraria for a Physicians’ Education Resource and from Global Blood Therapeutics; participated in Data Safety Monitoring Boards or Advisory Boards for Vertex, Addmedica and Novonordisk; and a leadership or fiduciary role as a member of the Steering Committee and Coordinator of the Red Cell Disorder Working Group of the Italian Association of Pediatric Hematology Oncology. NC has received a research grant for Novartis Precision Medicine. MdM has received honoraria for presentations by Addmedica and Novartis and support from Addmedica for attending a conference; and participated in a Data Safety Monitoring Board or Advisory Board for Addmedica, Vertex, and Novartis. JE has received grants from the European Horizon 2020 scheme and participated in the Data Safety Monitoring Board or Advisory Board of the Fondation Pierre Fabre. EE has received consulting fees from bluebird bio. ALG has an honorary advisory role on the Australian Sickle Cell Advisory Board. IMI has received a grant from the American Society of Hematology; consulting fees from Agios Pharmaceuticals; and honoraria from the American Society of Hematology. LCJ received royalties for a book chapter. AAK has received support from the Health resources and Services Administration. MLP has received consulting fees from the American College of Medical Genetics and Genomics; and participated in a Data Safety Monitoring Board or Advisory Board for the American College of Medical Genetics and Genomics and the American Academy of Pediatrics. ON has received travel support from the American Society of Hematology to attend a conference. DCR has received consulting fees from Vertex, Forma, Agios, and Vifor; received honoraria from Vertex; and participated in a Data Safety Monitoring Board or Advisory Board for TauRx and Mitsubishi. AS has received a scholar award from the American Society of Hematology, an advancing cures research award from the Doris Duke Charitable Foundation, and a Working group award from the Center for ELSI Resources and Analysis; consulting fees from Spotlight Therapeutics, Medexus, Vertex, Editas Medicine, and Sangamo Therapeutics; has received honoraria from Vindico Medical Education; and has a leadership or fiduciary role in the American Society for Transplantation and Cellular Therapy Content Committee, the Scientific Executive Committee, Sickle Cell Transplant Advocacy & Research Alliance, and the Pediatric Transplantation and Cellular Therapy Consortium Supportive Care Committee; and has financial interests with CRISPR Therapeutics, Vertex Pharmaceuticals, Novartis Pharmaceuticals, Magenta Therapeutics, and Beam Therapeutics. AAT has received consulting fees from GlaxoSmithKline and Global Blood Therapeutics; and honoraria from Novartis. REW has received consulting fees from Nova Laboratories; participated in a Data Safety Monitoring Board for Novartis and Editas; and received donations and support for clinical trials from Bristol Myers Squib, Addmedica, and Hemex Health. DJW has received a grant or contract from the US National Institutes for Health; received payment for expert testimony from Fredslough Law Firm; participated in a Data Safety Monitoring Board or Advisory board for Northwestern University; and is the founder and chairman of eNursing.

Inducing fetal hemoglobin (HbF) in red blood cells can alleviate β-thalassemia and sickle cell disease. We compared five strategies in CD34 + hematopoietic stem and progenitor cells, using either Cas9 nuclease or adenine base editors. The most potent modification was adenine base editor generation of γ-globin -175A>G. Homozygous -175A>G edited erythroid colonies expressed 81 ± 7% HbF versus 17 ± 11% in unedited controls, whereas HbF levels were lower and more variable for two Cas9 strategies targeting a BCL11A binding motif in the γ-globin promoter or a BCL11A erythroid enhancer. The -175A>G base edit also induced HbF more potently than a Cas9 approach in red blood cells generated after transplantation of CD34 + hematopoietic stem and progenitor cells into mice. Our data suggest a strategy for potent, uniform induction of HbF and provide insights into γ-globin gene regulation. More generally, we demonstrate that diverse indels generated by Cas9 can cause unexpected phenotypic variation that can be circumvented by base editing., (© 2023. The Author(s), under exclusive licence to Springer Nature America, Inc.)

Background: Sickle cell disease (SCD) is an inherited blood disorder that results in serious morbidity and early mortality. Novel therapies for SCD, most notably genetic therapies (GTs) and HLA-mismatched donor hematopoietic cell transplantation, are in clinical trials. While potentially curative, these interventions are some of the most intensive treatments for SCD and are associated with serious and life-altering side effects, which may manifest several years after treatment. Little is known about knowledge, beliefs, and attitudes of individuals with SCD, or their caregivers, toward existing and these emerging therapies., Methods: Patients with SCD at least 13 years of age (n = 66) and caregivers (n = 38) were surveyed about knowledge, attitudes, and beliefs surrounding treatments for SCD., Results: Only 4.8% felt "extremely knowledgeable" about GT for SCD while the majority (63.4%) reported little knowledge. Overall, health literacy was low among respondents. Most respondents had a neutral attitude regarding the safety of GT for SCD, and whether it was a good treatment for the disorder (56.7% and 58.6%, respectively). Only a few respondents endorsed the idea that GT was "unsafe" or "not a good treatment" (5.8% and 4.8%, respectively). There was an association between increasing knowledge about GT and agreement that it is safe (p = .012) and a good treatment for SCD (p = .031)., Conclusions: Given that very few patients with SCD feel knowledgeable about GT and a majority have neutral feelings about the safety and utility of this new approach, culturally appropriate patient-centered education is urgently needed as these treatments get regulatory approval and proceed to the clinic., (© 2023 Wiley Periodicals LLC.)

Objective: To evaluate attitudes toward vaccination and vaccine uptake regarding coronavirus disease 2019 (COVID-19) among pediatric patients with sickle cell disease (SCD) and their caregivers., Procedure: Adolescent patients and caregivers of children with SCD were surveyed during routine clinic visits; we then conducted a logistic regression analysis to understand differences in vaccine status, while qualitative responses were coded thematically., Results: Among respondents, the overall vaccination rate among adolescents and caregivers was 49% and 52%, respectively. Among the unvaccinated, 60% and 68% of adolescents and caregivers, respectively, preferred to remain unvaccinated, most commonly due to lack of perceived personal benefit from vaccination or mistrust in the vaccine. Multivariate logistic regression analysis showed that child's age (odds ratio [OR] = 1.1, 95% confidence interval [CI]: 1.0-1.2, p < .01) and caregiver education (measured by the Economic Hardship Index [EHI] score, OR = 0.76, 95% CI: 0.74-0.78, p < .05) were independent predictors of getting vaccinated., Conclusion: Despite the increased risk of severe illness due to COVID-19 in patients with SCD, vaccine hesitancy remains high in this population of families whose children have SCD. Fortunately, the reasons cited for deferring vaccination among those who are unvaccinated were largely due to barriers that may be overcome with quality communication around the utility of the vaccine and information about vaccine safety., (© 2023 Wiley Periodicals LLC.)

We adjusted haematopoietic stem and progenitor cell (HSPC) apheresis collection from patients with sickle cell disease (SCD) by targeting deep buffy coat collection using medium or low collection preference (CP), and by increasing anticoagulant-citrate-dextrose-solution A dosage. In 43 HSPC collections from plerixafor-mobilized adult patients with SCD, we increased the collection efficiency to 35.79% using medium CP and 82.23% using low CP. Deep buffy coat collection increased red blood cell contamination of the HSPC product, the product haematocrit was 4.7% with medium CP and 6.4% with low CP. These adjustments were well-tolerated and allowed efficient HSPC collection from SCD patients., (© 2022 British Society for Haematology and John Wiley & Sons Ltd.)

We characterized the human β-like globin transgenes in two mouse models of sickle cell disease (SCD) and tested a genome-editing strategy to induce red blood cell fetal hemoglobin (HbF; α2γ2). Berkeley SCD mice contain four to 22 randomly arranged, fragmented copies of three human transgenes (HBA1, HBG2-HBG1-HBD-HBBS and a mini-locus control region) integrated into a single site of mouse chromosome 1. Cas9 disruption of the BCL11A repressor binding motif in the γ-globin gene (HBG1 and HBG2; HBG) promoters of Berkeley mouse hematopoietic stem cells (HSCs) caused extensive death from multiple double-strand DNA breaks. Long-range sequencing of Townes SCD mice verified that the endogenous Hbb genes were replaced by single-copy segments of human HBG1 and HBBS including proximal but not some distal gene-regulatory elements. Townes mouse HSCs were viable after Cas9 disruption of the HBG1 BCL11A binding motif but failed to induce HbF to therapeutic levels, contrasting with human HSCs. Our findings provide practical information on the genomic structures of two common mouse SCD models, illustrate their limitations for analyzing therapies to induce HbF and confirm the importance of distal DNA elements in human globin regulation. This article has an associated First Person interview with the first author of the paper., Competing Interests: Competing interests M.J.W. is on advisory boards for Cellarity Inc., Novartis, Graphite Bio and Forma Therapeutics. J.Y. is an equity owner of Beam Therapeutics. The other authors declare no competing financial interests. A.S. is the site principal investigator of clinical trials for genome editing of sickle cell disease sponsored by Vertex Pharmaceuticals/CRISPR Therapeutics (NCT03745287) and Novartis (NCT04443907). The industry sponsors provide funding for the clinical trial, which includes salary support. A.S. has received consultant fees from Spotlight Therapeutics, Medexus Inc. and Vertex Pharmaceuticals. He has also received research funding from CRISPR Therapeutics and honoraria from Vindico Medical Education., (© 2022. Published by The Company of Biologists Ltd.)

Individuals with monogenic disorders can experience variable phenotypes that are influenced by genetic variation. To investigate this in sickle cell disease (SCD), we performed whole-genome sequencing (WGS) of 722 individuals with hemoglobin HbSS or HbSβ0-thalassemia from Baylor College of Medicine and from the St. Jude Children's Research Hospital Sickle Cell Clinical Research and Intervention Program (SCCRIP) longitudinal cohort study. We developed pipelines to identify genetic variants that modulate sickle hemoglobin polymerization in red blood cells and combined these with pain-associated variants to build a polygenic score (PGS) for acute vaso-occlusive pain (VOP). Overall, we interrogated the α-thalassemia deletion -α3.7 and 133 candidate single-nucleotide polymorphisms (SNPs) across 66 genes for associations with VOP in 327 SCCRIP participants followed longitudinally over 6 years. Twenty-one SNPs in 9 loci were associated with VOP, including 3 (BCL11A, MYB, and the β-like globin gene cluster) that regulate erythrocyte fetal hemoglobin (HbF) levels and 6 (COMT, TBC1D1, KCNJ6, FAAH, NR3C1, and IL1A) that were associated previously with various pain syndromes. An unweighted PGS integrating all 21 SNPs was associated with the VOP event rate (estimate, 0.35; standard error, 0.04; P = 5.9 × 10-14) and VOP event occurrence (estimate, 0.42; standard error, 0.06; P = 4.1 × 10-13). These associations were stronger than those of any single locus. Our findings provide insights into the genetic modulation of VOP in children with SCD. More generally, we demonstrate the utility of WGS for investigating genetic contributions to the variable expression of SCD-associated morbidities., (© 2021 by The American Society of Hematology.)

Sickle cell disease (SCD) is caused by a mutation in the β-globin gene HBB 1 . We used a custom adenine base editor (ABE8e-NRCH) 2,3 to convert the SCD allele (HBB S ) into Makassar β-globin (HBB G ), a non-pathogenic variant 4,5 . Ex vivo delivery of mRNA encoding the base editor with a targeting guide RNA into haematopoietic stem and progenitor cells (HSPCs) from patients with SCD resulted in 80% conversion of HBB S to HBB G . Sixteen weeks after transplantation of edited human HSPCs into immunodeficient mice, the frequency of HBB G was 68% and hypoxia-induced sickling of bone marrow reticulocytes had decreased fivefold, indicating durable gene editing. To assess the physiological effects of HBB S base editing, we delivered ABE8e-NRCH and guide RNA into HSPCs from a humanized SCD mouse 6 and then transplanted these cells into irradiated mice. After sixteen weeks, Makassar β-globin represented 79% of β-globin protein in blood, and hypoxia-induced sickling was reduced threefold. Mice that received base-edited HSPCs showed near-normal haematological parameters and reduced splenic pathology compared to mice that received unedited cells. Secondary transplantation of edited bone marrow confirmed that the gene editing was durable in long-term haematopoietic stem cells and showed that HBB S -to-HBB G editing of 20% or more is sufficient for phenotypic rescue. Base editing of human HSPCs avoided the p53 activation and larger deletions that have been observed following Cas9 nuclease treatment. These findings point towards a one-time autologous treatment for SCD that eliminates pathogenic HBB S , generates benign HBB G , and minimizes the undesired consequences of double-strand DNA breaks.

Recent studies suggest that plerixafor mobilization and apheresis in patients with sickle cell disease (SCD) is safe and can allow collection of sufficient CD34+ hematopoietic stem cell (HSC) collection for clinical gene therapy applications. However, the quantities of plerixafor-mobilized CD34+ cells vary between different SCD patients for unknown reasons. Twenty-three participants with SCD underwent plerixafor mobilization followed by apheresis, processing, and HSC enrichment under a phase 1 safety and efficacy study conducted at 2 institutions. Linear regression or Spearman's correlation test was used to assess the relationships between various hematologic and clinical parameters with total CD34+ cells/kg collected. Median CD34+ cells/kg after 2 or fewer mobilization and apheresis cycles was 4.0 × 106 (range, 1.5-12.0). Similar to what is observed generally, CD34+ yield correlated negatively with age (P < .001) and positively with baseline (P = .003) and preapheresis blood CD34+ cells/µL (P < .001), and baseline white blood cell (P = .01) and platelet counts (P = .03). Uniquely for SCD, CD34+ cell yields correlated positively with the number of days hydroxyurea was held (for up to 5 weeks, P = .01) and negatively with markers of disease severity, including hospitalization frequency within the preceding year (P = .01) and the number of medications taken for chronic pain (P = .002). Unique SCD-specific technical challenges in apheresis were also associated with reduced CD34+ cell collection efficiency and purification. Here, we describe factors that impact plerixafor mobilization success in patients with SCD, confirming known factors as described in other populations in addition to reporting previously unknown disease specific factors in patients with SCD. This trial was registered at www.clinicaltrials.gov as #NCT03226691.

Sickle cell disease (SCD) is a monogenic disorder characterized by recurrent episodes of severe bone pain, multi-organ failure, and early mortality. Although medical progress over the past several decades has improved clinical outcomes and offered cures for many affected individuals living in high-income countries, most SCD patients still experience substantial morbidity and premature death. Emerging technologies to manipulate somatic cell genomes and insights into the mechanisms of developmental globin gene regulation are generating potentially transformative approaches to cure SCD by autologous hematopoietic stem cell (HSC) transplantation. Key components of current approaches include ethical informed consent, isolation of patient HSCs, in vitro genetic modification of HSCs to correct the SCD mutation or circumvent its damaging effects, and reinfusion of the modified HSCs following myelotoxic bone marrow conditioning. Successful integration of these components into effective therapies requires interdisciplinary collaborations between laboratory researchers, clinical caregivers, and patients. Here we summarize current knowledge and research challenges for each key component, emphasizing that the best approaches have yet to be developed.

Transfusion-dependent β-thalassemia (TDT) and sickle cell disease (SCD) are severe monogenic diseases with severe and potentially life-threatening manifestations. BCL11A is a transcription factor that represses γ-globin expression and fetal hemoglobin in erythroid cells. We performed electroporation of CD34+ hematopoietic stem and progenitor cells obtained from healthy donors, with CRISPR-Cas9 targeting the BCL11A erythroid-specific enhancer. Approximately 80% of the alleles at this locus were modified, with no evidence of off-target editing. After undergoing myeloablation, two patients - one with TDT and the other with SCD - received autologous CD34+ cells edited with CRISPR-Cas9 targeting the same BCL11A enhancer. More than a year later, both patients had high levels of allelic editing in bone marrow and blood, increases in fetal hemoglobin that were distributed pancellularly, transfusion independence, and (in the patient with SCD) elimination of vaso-occlusive episodes. (Funded by CRISPR Therapeutics and Vertex Pharmaceuticals; ClinicalTrials.gov numbers, NCT03655678 for CLIMB THAL-111 and NCT03745287 for CLIMB SCD-121.)., (Copyright © 2020 Massachusetts Medical Society.)