Cedar Trial in Progress: A First in Human, Phase 1/2 Study of the Correction of a Single Nucleotide Mutation in Autologous HSCs (GPH101) to Convert HbS to HbA for Treating Severe SCD

Background Sickle cell disease (SCD) is a recessive monogenic disease caused by a single point mutation in which glutamic acid replaces valine in Codon 6 of the human beta-globin gene (HBB) leading to the production of abnormal globin chains (HbS) that polymerize and cause erythrocytes to sickle. This results in hemolytic anemia, vaso-occlusion and organ damage, which leads to lifelong complications and early mortality. Allogeneic hematopoietic stem cell transplant (allo-HSCT) is the only known cure for SCD, however, its use is limited by the lack of well-matched donors, need for immunosuppression, risk of graft versus host disease and graft rejection. GPH101 is an investigational, autologous, hematopoietic stem cell (HSC) drug product (DP) designed to correct the SCD mutation in the HBB gene ex vivo using a high fidelity Cas9 (CRISPR associated protein 9) paired with an AAV6 (adeno-associated virus type 6) delivery template, efficiently harnessing the natural homology directed repair (HDR) cellular pathway. This approach has the potential to restore normal adult hemoglobin (HbA) production while simultaneously reducing HbS levels. In preclinical studies, HBB gene correction in SCD donor HSCs resulted in ≥60% of gene-corrected alleles in vitro with minimal off-target effects. Gene corrected cells were successfully differentiated toward the erythroid lineage and produced ≥70% HbA in vitro. Long-term engraftment of gene-corrected HSCs was demonstrated in vivo, following transplant into immunodeficient mice, with multi-lineage allelic gene correction frequencies well above the predicted curative threshold of 20%, with potential of this approach to be equivalent or superior to allo-HSCT. In addition, HSC-based correction in an SCD mouse model led to stable adult hemoglobin production, increased erythrocyte lifespan and reduction in sickling morphology, demonstrating the therapeutic potential of this gene correction platform as a curative approach in SCD. Study Design and Methods CEDAR (NCT04819841) is a first-in-human, open-label, single-dose, multi-site Phase 1/2 clinical trial in participants with severe SCD designed to evaluate safety, efficacy and pharmacodynamics (PD) of GPH101. Approximately 15 adult (18-40 years) and adolescent (12-17 years) participants will be enrolled across 5 sites, with adolescent enrollment proceeding after a favorable assessment of adult safety data by a Safety Monitoring Committee. Participants must have a diagnosis of severe SCD (βS/βS), defined as ≥ 4 severe vaso-occlusive crises (VOCs) in the 2 years prior and/or ≥ 2 episodes of acute chest syndrome (ACS), in 2 years prior with at least 1 episode in the past year. Participants on chronic transfusion therapy may be eligible if required VOC and ACS criteria are met in the 2 years prior to the initiation of transfusions. Key exclusion criteria include availability of a 10/10 human leukocyte antigen-matched sibling donor, or prior receipt of HSCT or gene therapy. After eligibility confirmation including screening for pre-treatment cytogenetic abnormalities, participants will undergo plerixafor mobilization and apheresis, followed by CD34+ cell enrichment and cryopreservation, undertaken locally at each trial site before shipment to a centralized manufacturer for GPH101 production. After GPH101 release, participants will undergo eligibility reconfirmation prior to busulfan conditioning and DP infusion. Safety, efficacy and PD measurements will occur for 2 years post-infusion; a long-term follow up study will be offered to participants for an additional 13 years of monitoring. The primary endpoint for this study is safety, measured by the kinetics of HSC engraftment, transplant related mortality, overall survival and frequency and severity of adverse events. Secondary endpoints will explore efficacy and PD, including levels of globin expression as compared to baseline, gene correction rates, clinical manifestations of SCD (including VOC and ACS), laboratory parameters, complications and organ function. In addition, cerebral hemodynamics and oxygen delivery will be assessed by magnetic resonance techniques. Key exploratory endpoints include evaluation of patient-reported outcomes, erythrocyte function, on-target and off-target editing rates, and change from baseline in select SCD characteristics. Disclosures Kanter: Fulcrum Therapeutics, Inc.: Consultancy; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Forma: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Agios: Honoraria, Membership on an entity's Board of Directors or advisory committees; Beam: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; Graphite Bio: Consultancy; GuidePoint Global: Honoraria; Fulcrum Tx: Consultancy. Thompson: Agios Pharmaceuticals: Consultancy; Graphite Bio: Research Funding; Vertex: Research Funding; Beam Therapeutics: Consultancy; Celgene: Consultancy, Research Funding; Biomarin: Research Funding; Baxalta: Research Funding; CRISPR Therapeutics: Research Funding; Global Blood Therapeutics: Current equity holder in publicly-traded company; bluebird bio: Consultancy, Research Funding; Novartis: Research Funding. Porteus: Versant Ventures: Consultancy; CRISPR Therapeutics: Current equity holder in publicly-traded company; Allogene Therapeutics: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Ziopharm: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Graphite Bio: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees. Intondi: Graphite Bio: Current Employment, Current equity holder in publicly-traded company; Global Blood Therapeutics: Current equity holder in publicly-traded company, Ended employment in the past 24 months. Lahiri: Graphite Bio: Current Employment, Current equity holder in publicly-traded company. Dever: Graphite Bio: Current Employment, Current equity holder in publicly-traded company. Petrusich: bluebird bio: Current equity holder in publicly-traded company, Ended employment in the past 24 months; Graphite Bio: Current Employment, Current equity holder in publicly-traded company. Lehrer-Graiwer: Global Blood Therapeutics: Current equity holder in publicly-traded company, Ended employment in the past 24 months; Graphite Bio: Current Employment, Current equity holder in publicly-traded company.

Correlation of fetal hemoglobin in different cancer patients and sickle cell anaemia: A review

Fetal hemoglobin is the main hemoglobin during gestation period. But this globin chain is replaced and is taken over by adult hemoglobin. Sometimes this switch from fetal to adult fails to occur leading to production of fetal hemoglobin as in case of sickle cell anemia. It is also observed that fetal hemoglobin expression is also seen under malignant condition. In malignancy the spleen, liver as well as gut acquire its ability to produce fetal hemoglobin. Certain HbF cells inducing factor such as stem cell growth factor and interleukin -3 also promote HbF erythropoiesis. HbF cells are indicated as a biomarker of tumour cells implicated in many carcinomas observed by immunohisto chemical investigations.

BCL11A promotes myeloid leukemogenesis by repressing PU.1 target genes

The transcriptional repressor, BCL11A, is involved in hematological malignancies, B-cell development, and fetal-to-adult hemoglobin switching. However, the molecular mechanism by which it promotes the development of myeloid leukemia remains largely unknown. We find that Bcl11a cooperates with the pseudokinase, Trib1, in the development of acute myeloid leukemia (AML). Bcl11a promotes the proliferation and engraftment of Trib1-expressing AML cells both in vitro and in vivo. ChIP-seq analysis showed that upon DNA-binding, Bcl11a is significantly associated with PU.1, an inducer of myeloid differentiation, and that Bcl11a represses several PU.1 target genes, such as Asb2, Clec5a, and Fcgr3. Asb2, as a Bcl11a target gene that modulates cytoskeleton and cell-cell interaction, plays a key role in Bcl11a-induced malignant progression. The repression of PU.1 target genes by Bcl11a is achieved by both sequence-specific DNA-binding activity and recruitment of corepressors by Bcl11a. Suppression of the corepressor components, HDAC and LSD1, reverses the repressive activity. Moreover, treatment of AML cells with the HDAC inhibitor, pracinostat, and LSD1 inhibitor, GSK2879552, resulted in growth inhibition both in vitro and in vivo. High BCL11A expression is associated with worse prognosis in human AML patients. Blocking of BCL11A expression upregulates the expression of PU.1 target genes, and inhibits the growth of HL-60 cells and their engraftment to the bone marrow, suggesting that BCL11A is involved in human myeloid malignancies via the suppression of PU.1 transcriptional activity.

Rapid Separation of Human Hemoglobin on a Large Scale From Non-clarified Bacterial Cell Homogenates Using Molecularly Imprinted Composite Cryogels

The production of a macroporous hydrogel column, known as cryogel, has been scaled up (up to 150 mL) in this work for the purification of human hemoglobin from non-clarified bacterial homogenates. Composite cryogels were synthesized in the presence of adult hemoglobin (HbA) to form a molecularly imprinted polymer (MIP)network where the affinity sites for the targeted molecule were placed directly on an acrylamide cryogel by protein imprinting during the cryogelation. The MIP composite cryogel column was first evaluated in a well-defined protein mixture. It showed high selectivity toward HbA in spite of the presence of serum albumin. Also, when examined in complex non-clarified E. coli cell homogenates, the column showed excellent chromatographic behavior. The binding capacity of a 50 mL column was thus found to be 0.88 and 1.2 mg/g, from a protein mixture and non-clarified cell homogenate suspension, respectively. The recovery and purification of the 50 mL column for separation of HbA from cell suspension were evaluated to be 79 and 58%, respectively. The MIP affinity cryogel also displayed binding and selectivity toward fetal Hb (HbF) under the same operational conditions.

Distinct effects of V617F and exon12-mutated JAK2 expressions on erythropoiesis in a human induced pluripotent stem cell (iPSC)-based model

Activating mutations affecting the JAK-STAT signal transduction is the genetic driver of myeloproliferative neoplasms (MPNs) which comprise polycythemia vera (PV), essential thrombocythemia (ET) and myelofibrosis. The JAK2p.V617F mutation can produce both erythrocytosis in PV and thrombocytosis in ET, while JAK2 exon 12 mutations cause only erythrocytosis. We hypothesized that these two mutations activated different intracellular signals. In this study, the induced pluripotent stem cells (iPSCs) were used to model JAK2-mutated MPNs. Normal iPSCs underwent lentiviral transduction to overexpress JAK2p.V617F or JAK2p.N542_E543del (JAK2exon12) under a doxycycline-inducible system. The modified iPSCs were differentiated into erythroid cells. Compared with JAK2V617F-iPSCs, JAK2exon12-iPSCs yielded more total CD71+GlycophorinA+ erythroid cells, displayed more mature morphology and expressed more adult hemoglobin after doxycycline induction. Capillary Western immunoassay revealed significantly higher phospho-STAT1 but lower phospho-STAT3 and lower Phospho-AKT in JAK2exon12-iPSCs compared with those of JAK2V617F-iPSCs in response to erythropoietin. Furthermore, interferon alpha and arsenic trioxide were tested on these modified iPSCs to explore their potentials for MPN therapy. Both agents preferentially inhibited proliferation and promoted apoptosis of the iPSCs expressing mutant JAK2 compared with those without doxycycline induction. In conclusion, the modified iPSC model can be used to investigate the mechanisms and search for new therapy of MPNs.

A Small Key for a Heavy Door: Genetic Therapies for the Treatment of Hemoglobinopathies

Throughout the past decades, the search for a treatment for severe hemoglobinopathies has gained increased interest within the scientific community. The discovery that ɤ-globin expression from intact HBG alleles complements defective HBB alleles underlying β-thalassemia and sickle cell disease, has provided a promising opening for research directed at relieving ɤ-globin repression mechanisms and, thereby, improve clinical outcomes for patients. Various gene editing strategies aim to reverse the fetal-to-adult hemoglobin switch to up-regulate ɤ-globin expression through disabling either HBG repressor genes or repressor binding sites in the HBG promoter regions. In addition to these HBB mutation-independent strategies involving fetal hemoglobin (HbF) synthesis de-repression, the expanding genome editing toolkit is providing increased accuracy to HBB mutation-specific strategies encompassing adult hemoglobin (HbA) restoration for a personalized treatment of hemoglobinopathies. Moreover, besides genome editing, more conventional gene addition strategies continue under investigation to restore HbA expression. Together, this research makes hemoglobinopathies a fertile ground for testing various innovative genetic therapies with high translational potential. Indeed, the progressive understanding of the molecular clockwork underlying the hemoglobin switch together with the ongoing optimization of genome editing tools heightens the prospect for the development of effective and safe treatments for hemoglobinopathies. In this context, clinical genetics plays an equally crucial role by shedding light on the complexity of the disease and the role of ameliorating genetic modifiers. Here, we cover the most recent insights on the molecular mechanisms underlying hemoglobin biology and hemoglobinopathies while providing an overview of state-of-the-art gene editing platforms. Additionally, current genetic therapies under development, are equally discussed.

CD14+ monocytes repress gamma globin expression at early stages of erythropoiesis

In β-hemoglobinopathies, reactivation of gamma- at the expense of beta-globin is a prominent therapeutic option. Expression of the globin genes is not strictly intrinsically regulated during erythropoiesis, supported by the observation that fetal erythroid cells switch to adult hemoglobin expression when injected in mice. We show cultured erythroblasts are a mix of HbA restrictive and HbA/HbF expressing cells and that the proportion of cells in the latter population depends on the starting material. Cultures started from CD34+ cells contain more HbA/HbF expressing cells compared to erythroblasts cultured from total peripheral blood mononuclear cells (PBMC). Depletion of CD14+ cells from PBMC resulted in higher HbF/HbA percentages. Conversely, CD34+ co-culture with CD14+ cells reduced the HbF/HbA population through cell–cell proximity, indicating that CD14+ actively repressed HbF expression in adult erythroid cultures. RNA-sequencing showed that HbA and HbA/HbF populations contain a limited number of differentially expressed genes, aside from HBG1/2. Co-culture of CD14+ cells with sorted uncommitted hematopoietic progenitors and CD34-CD36+ erythroblasts showed that hematopoietic progenitors prior to the hemoglobinized erythroid stages are more readily influenced by CD14+ cells to downregulate expression of HBG1/2, suggesting temporal regulation of these genes. This possibly provides a novel therapeutic avenue to develop β-hemoglobinopathies treatments.

β-Hemoglobinopathies: The Test Bench for Genome Editing-Based Therapeutic Strategies

Hemoglobin is a tetrameric protein composed of two α and two β chains, each containing a heme group that reversibly binds oxygen. The composition of hemoglobin changes during development in order to fulfill the need of the growing organism, stably maintaining a balanced production of α-like and β-like chains in a 1:1 ratio. Adult hemoglobin (HbA) is composed of two α and two β subunits (α2β2 tetramer), whereas fetal hemoglobin (HbF) is composed of two γ and two α subunits (α2γ2 tetramer). Qualitative or quantitative defects in β-globin production cause two of the most common monogenic-inherited disorders: β-thalassemia and sickle cell disease. The high frequency of these diseases and the relative accessibility of hematopoietic stem cells make them an ideal candidate for therapeutic interventions based on genome editing. These strategies move in two directions: the correction of the disease-causing mutation and the reactivation of the expression of HbF in adult cells, in the attempt to recreate the effect of hereditary persistence of fetal hemoglobin (HPFH) natural mutations, which mitigate the severity of β-hemoglobinopathies. Both lines of research rely on the knowledge gained so far on the regulatory mechanisms controlling the differential expression of globin genes during development.