The results suggest that this approach may overcome the reliance on busulfan or other myeloablative conditioning regimens with their associated morbidities, and by enabling toxin-free conditioning and in vivo selection of edited cells, may facilitate clinical implementation of these highly valuable genetic therapies.
Abstract
Clinical evidence demonstrates that ex vivo gene therapy and genome engineering of hematopoietic stem and progenitor cells (HSPCs) could represent one-time cures. However, while genome editing itself has become increasingly efficient and precise, the toxic conditioning required for hematopoietic stem cell transplantation remains a major barrier to broad clinical implementation of these otherwise curative therapies. In particular, the use of busulfan for myeloablative conditioning constitutes a major safety concern. While preclinical studies established CD117 as a promising target for antigen-specific therapy, clinical translation faced setbacks balancing efficacy and safety. To overcome current limitations, we generated a new CD117-blocking monoclonal antibody (CIM058) and demonstrate its potency to block wild-type HSPCs. To enable long-term blockade of host HSPCs even after transplantation, we used prime editing to engineer CIM058-resistant human CD34+ HSPCs. When combined, CIM058 and the epitope engineered CD34+ HSPCs ameliorated disease phenotype in a β-thalassemia model. Our results suggest that this approach may overcome the reliance on busulfan or other myeloablative conditioning regimens with their associated morbidities, and by enabling toxin-free conditioning and in vivo selection of edited cells, may facilitate clinical implementation of these highly valuable genetic therapies.
Epitope editing of KIT enables antibody-based, non-genotoxic conditioning that selectively enriches therapeutic BCL11A-edited haematopoietic stem/progenitor cells, supports durable engraftment, preserves clonal diversity and enhances induction of fetal haemoglobin, a therapeutic approach for conditions such as sickle cell disease and β-thalassemia.
G. Casirati, Andrea Cosentino, Marta Freschi et al.· Nature· 0 citations
Gene therapy achieved through genetic manipulation and transfer of hematopoietic stem and progenitor cells (HSPC) is becoming an increasingly attractive option for personalized medicine. In the current clinical scenarios, use is restricted to overcoming genetic disorders, but it is envisioned that more diverse applications will be developed in the future. Immunotherapy of malignant disease already employs non-HSPC-based gene therapies, and there is a body of evidence that HSPC-mediated gene therapy has potential as a powerful immunotherapeutic for some diseases of immune dysregulation such as autoimmune disease and allergies. Administration of HSPC gene-engineered to encode antigen(s) induces antigen-specific immune tolerance in animal models. To translate this technology, we sought to identify whether human dendritic cells (DC) and other antigen-presenting cell populations derived from lentivirally transduced HSPC would express, process, and present antigens of interest. Lentiviral vectors were generated that encoded preproinsulin, a relevant autoantigen implicated in type 1 diabetes, or a control protein carrying a viral epitope along with reporter genes under transcriptional control of ubiquitous or antigen-presenting cell-directed promoters. In vitro, DC were differentiated from transduced HSPC and tested in antigen presentation assays using Jurkat lines carrying relevant type 1 diabetes-associated T cell receptors. In vivo, transduced HSPC were used to generate humanized mice, and the development of a range of antigen-presenting cells and their expression of lentivirus-encoded genes were determined. Antigen-presenting cell progeny of transduced HSPC expressed antigens and reporter genes both in vitro and in vivo, and in vitro-generated DC presented lentivirally encoded antigens. The studies characterize human chimerism and therapeutic gene expression in a new model and provide support for the use of HSPC-based gene therapies for immune dysregulation in humans.
Clara Heider, Meg L. Donovan, C. Walpole et al.· Human Gene Therapy· 0 citations
Hematopoietic stem and progenitor cells (HSPCs) gene therapy may transform the therapeutic landscape for inherited hematological disorders and already offers potentially curative options for some diseases, including inborn errors of immunity and β-hemoglobinopathies. Its continued success relies on further refinement of gene transfer technologies, gene editing tools such as CRISPR-Cas, and optimized ex vivo HSPC manipulation protocols that ensure robust, long-term engraftment and clonal diversity with reduced-toxicity, non-genotoxic conditioning strategies. Here, we review recent developments and refinements in gene transfer and editing technologies for HSPCs, while also discussing the critical limitations and hurdles to clinical translation, as recently presented at the New Investigator Committee Gene Therapy webinar. Future directions must prioritize integrating technological innovation with the development of equitable and simplified models to reduce costs and ensure that these life-saving cellular therapies reach patients worldwide. Teaser abstract Hematopoietic stem and progenitor cells (HSPCs) gene therapy is advancing rapidly, with lentiviral gene transfer, genome editing, and emerging in vivo delivery approaches expanding the therapeutic landscape for inherited hematologic disorders. Recent clinical successes have demonstrated the potential for durable correction, while ongoing refinements continue to improve safety, efficacy, and feasibility. Key challenges remain in genotoxicity, conditioning toxicity, manufacturing scalability, and equitable global access.
Kohei Shiroshita, A. Stolz, C. Malouf et al.· Experimental Hematology· 0 citations
It is concluded from preliminary data that gene therapy using BE HSPCs appear very promising for achieving an earlier and more robust multi-lineage immune reconstitution in adult patients using BE HSPCs.
S. S. de Ravin, Michelle Ma, Yuzhi Yin et al.· Journal of Human Immunity· 0 citations
The clinical successes of chimeric antigen receptor (CAR) T cells represent a major shift in immunotherapy. However, there is also increasing emphasis on potential long-term effects of CAR T cell therapy, especially using preclinical xenogeneic models. It has been previously demonstrated that only naïve, and not memory, peripheral blood human T cells can mediate a rapid and acute xenogeneic graft-versus-host disease (xenoGVHD). Here, we demonstrate that simply by altering the donor T cells in the process of generating CAR T cells, in which they are all memory phenotype, that the xenoGVHD outcome was markedly altered. Following tumor clearance with CAR T cell administration, we observed a significantly delayed (up to 200 days post-transfer with some donors) occurrence of lethal xenoGVHD, marked by profound scleroderma and multi-organ pathology consistent with chronic, not acute, GVHD. Notably, this novel chronic xenoGVHD occurred in the absence of B cells, which are classically associated with mediating chronic GVHD pathology. TCR-repertoire constriction during disease and the lack of disease using MHCI/II double-knockout NSG recipient mice confirmed the observed pathology was xenoGVHD and mediated by human-TCR:murine-MHC interactions. Interestingly, despite the consistent expansion of CAR-positive T cells during early tumor-clearance, a later emergence of CAR-negative populations during xenoGVHD also resulted. Our findings highlight xenoGVHD as a problem that makes long-term assessment of CAR T efficacy or toxicity highly problematic in xenograft models due to the artefact of xenoreactivity which is not representative of autologous clinical usage, and the profound effect that T cell alterations have in GVHD pathophysiology.
Wahed A. Firoz, Michael K. Sheng, Pedro Ruivo et al.· Blood Advances· 0 citations
Gene therapy for sickle cell disease and transfusion-dependent thalassemia is now widely available, yet its broader application is constrained by the need for effective and tolerable conditioning. This review examines the central role of conditioning in enabling durable engraftment of gene-modified hematopoietic stem cells, emphasizing the narrow therapeutic window between insufficient niche clearance and excessive toxicity. Busulfan remains the standard, supported by consistent engraftment and clinical efficacy, but is limited by acute and long-term toxicities, including infertility and potential genotoxicity. Emerging strategies aim to mitigate these risks. Reduced-intensity melphalan shows early promise but raises concerns regarding durability, while treosulfan offers a potentially safer profile, though data in the autologous setting are lacking. Antibody-based, nongenotoxic approaches represent a transformative direction but remain investigational. Refining conditioning through comparative trials and long-term follow-up will be critical to fully realizing the curative potential of gene therapy.
Akshay Sharma, S. Corbacioglu· Blood Advances· 0 citations