Next Gen HSC GT for IEI: Developing the next generation of haematopoietic stem cell gene therapies for inborn errors of immunity
Lead Research Organisation:
UNIVERSITY COLLEGE LONDON
Abstract
Gene therapy (GT) can be used to cure genetic diseases through the correction (editing) of genetic mistakes (mutations) or by replacing them with a healthy copy of the gene. It offers huge potential to cure for certain diseases that have until recently been very difficult to treat. GT is particularly promising in blood disorders such as sickle cell anaemia, and rarer immune system disorders such as CTLA4 insufficiency, which is characterised by a dysregulated immune system resulting in severe autoimmunity, uncontrolled inflammation and a predisposition to infections. Until recently, allogeneic stem cell transplant has been the only cure available for these diseases, but transplant confers significant long-term toxicities for patients and results in death in up to one in five patients (PMID 39218359) .
In blood and immune system disorders, GT works by correcting faulty genes in blood and immune cell precursors known as haematopoietic stem cells (HSCs). HSCs reside in the bone marrow, self-renew and produce the mature cells of the blood and immune system, which are continuously released into the blood stream . For GT to be successful there must be enough successfully edited (genetically corrected) mature cells in the blood, and the genetically corrected HSCs must be capable of self-renewal to achieve a long-term cure. Current GT technology is promising but has various toxicities. Viral vector technologies use viruses to carry the edited/corrected gene and insert it into the genome of the patient’s target cells. However, the edited gene can be randomly inserted into patient’s genome (insertional mutagenesis), which may cause serious problems for the patient such as cancer. More precise gene editing tools such as CRISPR/Cas9 which uses genetic ‘scissors’ to insert the desired gene into a precise position in the patient’s genome have reduced this risk. However, as CRISPR/Cas9 causes a double stranded DNA (dsDNA) break there is a risk of large off-target effects in the genome. Both viral vector and CRISPR/Cas9 mediated GT require the removal of HSCs and ex vivo genetic modification prior to reinfusion into the patient. Before re-infusion patients require conditioning chemotherapy to kill off uncorrected stem cells and make space for the incoming, genetically corrected cells. This chemotherapy is intensive and toxic.
This project will use a combination of newer, more targeted and potentially safer techniques, currently in development, and will use CTLA4 insufficiency as a model disease to edit HSCs from patients and healthy donors. The project has three aims: (1) to use more precise technologies (base editing and prime editing) which allow gene editing without creating dsDNA breaks, thereby reducing the risk of off-target effects in the genome; (2) to assess the engraftment potential and functional correction of base and prime edited HSCs in murine models; and (3) to combine this precise gene editing method with epitope engineering, a technique that provides the gene-edited HSCs with a selective advantage in the presence of targeted antibodies (PMID: 37648862), thus permitting more efficient expansion of corrected HSCs. Such an approach could prevent the need for toxic conditioning chemotherapy. The proposed approach, if successful could be used in the future for patients with a wide range of genetic diseases of the blood and immune system, creating safer, less toxic curative therapies.
In blood and immune system disorders, GT works by correcting faulty genes in blood and immune cell precursors known as haematopoietic stem cells (HSCs). HSCs reside in the bone marrow, self-renew and produce the mature cells of the blood and immune system, which are continuously released into the blood stream . For GT to be successful there must be enough successfully edited (genetically corrected) mature cells in the blood, and the genetically corrected HSCs must be capable of self-renewal to achieve a long-term cure. Current GT technology is promising but has various toxicities. Viral vector technologies use viruses to carry the edited/corrected gene and insert it into the genome of the patient’s target cells. However, the edited gene can be randomly inserted into patient’s genome (insertional mutagenesis), which may cause serious problems for the patient such as cancer. More precise gene editing tools such as CRISPR/Cas9 which uses genetic ‘scissors’ to insert the desired gene into a precise position in the patient’s genome have reduced this risk. However, as CRISPR/Cas9 causes a double stranded DNA (dsDNA) break there is a risk of large off-target effects in the genome. Both viral vector and CRISPR/Cas9 mediated GT require the removal of HSCs and ex vivo genetic modification prior to reinfusion into the patient. Before re-infusion patients require conditioning chemotherapy to kill off uncorrected stem cells and make space for the incoming, genetically corrected cells. This chemotherapy is intensive and toxic.
This project will use a combination of newer, more targeted and potentially safer techniques, currently in development, and will use CTLA4 insufficiency as a model disease to edit HSCs from patients and healthy donors. The project has three aims: (1) to use more precise technologies (base editing and prime editing) which allow gene editing without creating dsDNA breaks, thereby reducing the risk of off-target effects in the genome; (2) to assess the engraftment potential and functional correction of base and prime edited HSCs in murine models; and (3) to combine this precise gene editing method with epitope engineering, a technique that provides the gene-edited HSCs with a selective advantage in the presence of targeted antibodies (PMID: 37648862), thus permitting more efficient expansion of corrected HSCs. Such an approach could prevent the need for toxic conditioning chemotherapy. The proposed approach, if successful could be used in the future for patients with a wide range of genetic diseases of the blood and immune system, creating safer, less toxic curative therapies.
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| Hannah Al Yousuf (Principal Investigator / Fellow) |