Targeted immunotherapies have transformed the treatment of hematologic malignancies, yet their clinical utility is often constrained by on-target, off-tumor toxicity arising from shared antigen expression between malignant cells and essential healthy tissues. An early approach to mitigate this limitation involved the knockout (KO) of the target antigen in donor hematopoietic stem and progenitor cells (HSPCs). However, this strategy is restricted to markers that are dispensable for normal hematopoietic function. Epitope engineering has emerged as an alternative paradigm to decouple therapeutic susceptibility from physiological function by modifying the target antigen on healthy cells while preserving biological activity. In this review, we discuss recent advances in base and prime editing approaches used for epitope editing. We examine recent preclinical and emerging translational studies of this strategy in both malignant and non-malignant contexts. Finally, we discuss challenges related to editing efficiency, off-target effects, delivery strategies, and long-term safety in hematopoietic stem cells. Collectively, epitope engineering of hematopoietic stem cells represents a versatile platform to expand the therapeutic window of precision immunotherapies and may enable safer, more effective combinatorial treatment strategies for both non-malignant and malignant hematologic conditions.
Joanne Baek, G. Casirati, Pietro Genovese et al.· Blood Advances· 0 citations
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
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