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.
Abstract
X-linked Severe Combined Immunodeficiency (XSCID) due to IL2RG loss-of-function mutations typically cause a severe combined cellular and humoral immunodeficiency that is diagnosed and transplanted in infancy. Hypomorphic IL2RG variants with milder phenotypes are generally diagnosed later in life. Early stem cell transplants (allogeneic or autologous gene therapy) performed without conditioning often results in partial immune reconstitution with limited donor engraftment in T cell lineage alone. Defective host B, natural killer (NK), and other cell lineages remain and can cause progressive multi-organ disease. Ex vivo gene therapy using lentivector-transduced autologous hematopoietic stem/progenitor cells (HSPCs) has provided clinical benefit for many previously transplanted older XSCID patients (NCT01306019) and transplant-naïve infants (NCT01512888, NCT03311503). Lentivector transduction functionally corrects XSCID stem cells by semi-random insertion of IL2RG cDNA under the regulation of an engineered promoter. A conversion to gene-corrected immune cells in their respective compartment can take years, particularly in older adult patients. The exact mechanism for this slow progression, whether this is attributable to a relatively weak promoter in the transgenes, is unclear. CRISPR/Cas9 base editing provides the potential for precise gene mutation correction that is devoid of random virus integrations and, critically, restores physiological gene regulation by endogenous promoter. We developed a highly efficient base editing strategy using adenine base editor and respective guide RNAs to repair respective IL2RG mutations (IL2RG p.289X, IL2RG p.Gln235X, IL2RG p.Q144X, and IL2RG p.R226H). Preclinical efficacy and safety data supported a Phase I/II clinical trial to treat XSCID patients with base-edited HSPCs (IND 31037; NCT 06851767). Three patients have been treated to date with base-edited (BE) HSPCs (25 million to 50 million cells per kg/weight). BE HSPC products were well tolerated, with early myeloid recovery within 3 weeks after cell infusion. Gene correction frequencies in the study cell products averaged >80%. Follow-up data at 6 months in the first patient showed robust levels of gene correction in myeloid (70%), B (94%), NK (100%), and, surprisingly, in his T cell compartment (65%) as well, with a corresponding decline in donor T cell chimerism (99% at baseline, 47% at 6 months). Monitoring of the other treated patients is ongoing. We conclude from our 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.
Autologous HSC transplantation does not have the previously mentioned problems associated with allogeneic transplantation, and gene editing involving ex vivo genetic modification of HSCs and subsequent reinfusion in a single patient has emerged.
Qiu Li, Hong-Xia Wang, Yu-Qin He et al.· International journal of hem...· 0 citations
INTRODUCTION
Inborn errors of immunity (IEI) are rare genetic defects that disrupt immune function, often resulting in life-threatening infections, malignancies, and immune dysregulation. Allogeneic hematopoietic stem cell transplantation (HSCT), a curative option for some diagnoses, is limited by donor availability and risks of graft-versus-host disease. This review explores the 30-year evolution of autologous gene therapy as a vital alternative to allogeneic hematopoietic stem cell transplantation for IEIs.
AREAS COVERED
Literature search using PubMed for gene therapy for IEI in the last 20 years. We trace the transition from early gamma-retroviral gene addition - which successfully restored immunity in severe combined immunodeficiency (SCID) but carried high risks of insertional mutagenesis and leukemogenesis - to the adoption of safer self-inactivating lentiviral vectors. The field is rapidly advancing beyond viral gene addition toward highly precise gene editing technologies, including CRISPR/Cas9, and base/prime editing, which offer targeted correction with minimized genotoxicity.
EXPERT OPINION
Recent milestones in diseases like Wiskott-Aldrich syndrome (WAS) and chronic granulomatous disease (CGD) highlight enormous scientific success, yet significant barriers to accessibility, manufacturing, and affordability remain. Overcoming this requires innovative regulatory frameworks and collaborative funding models. Streamlining development and ensuring equitable access are essential next steps to establishing gene therapy as a safe alternative.
Jasmeen Dara, Claire Booth· Expert Opinion on Biological...· 0 citations
Autologous HSC gene therapy is supported as an effective alternative to alloHSCT with a favorable risk-benefit profile for severe LAD-I, and markedly lower annualized incidences of prespecified serious infections, infection-related hospitalizations, and prolonged infection-related hospitalizations after RP-L201 treatment relative to pre-treatment incidences.
C. Booth, J. Sevilla, E. Almarza et al.· Journal of Human Immunity· 0 citations
Graft-versus-host disease (GVHD) remains a primary cause of morbidity and mortality post-allogeneic hematopoietic stem cell transplantation (allo-HSCT), driven by donor T cells’ dysregulated inflammation against host tissues. This limits survival and underscores the need for therapies that curb GVHD while preserving graft-versus-tumor (GVT) effects. Innate-like T cell subsets, including MAIT, NKT, and Vγ2 γδ T cells correlate with milder GVHD. These share the BTB-ZF transcription factor PLZF (Zbtb16), a master regulator of innate-like programming. Building on our finding that ectopic PLZF imparts innate-like traits to conventional αβ T cells, we tested if PLZF-overexpressing donor T cells suppress GVHD in vivo.
In a B6→BALB/c acute GVHD model, lethally irradiated BALB/c recipients received bone marrow plus purified CD4+/CD8+ T cells from C57BL/6 donors, transduced with retroviral PLZF or empty vector (EV) control (n = 15/group). Mice were monitored daily for survival, clinical scores, and weight loss.
In mouse models of acute GVHD (B6→BALB/c), adoptive transfer of retrovirally transduced, PLZF-overexpressing conventional T cells markedly delayed disease onset and enhanced survival relative to empty vector-transduced controls. Mechanistically, PLZF-overexpressing conventional T cell promoted expansion of regulatory T cell (Treg) populations, thereby driving a phenotypic shift toward innate-like suppression of alloimmunity.
These results affirm PLZF overexpression as a viable, programmable approach for GVHD prophylaxis, poised for clinical advancement. Through innate-like T cell reprogramming, this strategy holds promise for revolutionizing allo-HSCT by decoupling immune tolerance from antitumor immunity. Current investigations are evaluating PLZF-overexpressing conventional T cell preservation of graft versus tumor (GVT) activity against leukemia and extending these findings to humanized models.
NJ PHORCE
Transplantation Immunology (TRAN)
Jake Cox, Dhruti Patel, Steven Montecinos Montes et al.· Journal of Immunology· 0 citations
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.
Romina Marone, Rosalba Lepore, K. Paschoudi et al.· bioRxiv· 0 citations
Germline gain-of-function (GOF) mutations in the signal transducer and activator of transcription 1 (STAT1) gene cause a dominantly inherited inborn error of immunity (IEI) characterized by chronic mucocutaneous candidiasis, autoimmunity, severe opportunistic infections and an increased risk of malignancy. Allogeneic hematopoietic stem cell (HSC) transplantation (HSCT) is curative but is associated with increased risk of morbidity and mortality in STAT1 GOF patients compared to other IEI. To develop a curative, autologous alternative to HSCT, we evaluated gene editing strategies in STAT1 GOF model cell lines, primary T cells, and patient-derived HSCs. Universal and mutation-specific strategies using CRISPR/Cas-mediated homology-directed repair (HDR) were limited by low efficacy (<25%), poor viability, and a lack of allele-specificity. In contrast, adenine base editing corrected the recurrent and highly pathogenic p.T385M mutation with upwards of 90% efficiency in patient T cells and HSCs without significant unintended on- or off-target genomic aberrations. Gene editing functionally restored total STAT1 expression (p<0.0217), STAT1 phosphorylation (p<0.0056), interferon-stimulated gene expression (OAS1; p=0.0005) and improved IL-17 production (p<0.0001). Edited HSCs retained multilineage differentiation capacity and sustained engraftment with persistence of the corrected allele at 16 weeks in humanized immunodeficient mice. These data demonstrate efficient and precise correction of STAT1 GOF mutations by base editing, with maintenance of the correction through long-term engraftment in vivo. This represents the first application of gene editing to correct a dominant gain-of-function mutation causing immunodeficiency, with potential applicability to other genetic disorders associated with heterozygous and gain-of-function mutations.
Robert Torrance, K. Orf, Nathan White et al.· Blood· 0 citations