Gentner, B. | Search bioRxiv

bioRxiv2026

Ex Vivo Expansion of Hematopoietic Stem and Progenitor Cells from Human Mobilized Peripheral Blood for Gene Therapy Applications

Ex vivo expansion of mobilized peripheral blood (mPB) hematopoietic stem cells (HSCs) represents a promising approach to advance cell and gene therapy strategies yet is hampered by loss of stem cell function when applying commonly used culture protocols. We performed in-depth characterization of mPB expansion cultures by single cell RNA sequencing, which highlighted differentiation trajectories with preservation of lineage fidelity in committed progenitors. Defining a putative HSC cluster allowed an estimation of transduction efficiency in ex vivo cultures, which correlated with long-term gene marking in xenografts and patients enrolled in a gene therapy study. We then developed a clinically translatable, GMP-compliant process to expand lentivirus (LV)-transduced HSCs from mPB of pediatric patients and adult donors, by biologically informed protocol improvements of cytokine supplementation, media choice, timing of LV transduction and combinations of small molecules preventing the activation of differentiation programs. Our optimized process outperforms validated state-of-the-art cord blood expansion protocols when applied to mPB. LV integration site analysis and genomic barcode-based clonal tracking provided definitive proof for symmetric HSC self-renewal divisions occurring during ex vivo culture. These results warrant clinical testing of this HSC transduction/expansion process in an upcoming clinical gene therapy trial for autosomal recessive osteopetrosis (EU CT 2024-518972-30). One Sentence SummaryA mobilized peripheral blood HSC expansion protocol optimized for gene therapy allows robust polyclonal long-term engraftment of LV-transduced cells.

cell biology↗

bioRxiv2024

DNA-Dependent Protein Kinase Inhibitors PI-103 and Samotolisib Augment CRISPR/Cas9 Knockin Efficiency in Human T Cells

1.The adoptive cell transfer of ex vivo expanded tumor infiltrating lymphocytes (i.e., TIL therapy) is a promising clinical strategy and recently FDA approved for melanoma but has major limitations including that not all tumors are inflamed. Moreover, tumor-specific clones can be rare and in an exhausted state due to the suppressive tumor microenvironment. These obstacles can be overcome by engineering autologous peripheral blood T cells with pre-selected T cell receptors (TCRs) by viral vector-mediated gene insertion. While viral transduction is highly efficient, the insertional site is not specific and persistence of the T cells is oftentimes limited. In contrast, site-specific integration of the TCR into the TCR chain (TRAC) locus by CRISPR/Cas9 has been shown to enable more consistent and physiological levels of exogenous TCR expression coupled with superior persistence and tumor control in preclinical studies. Here, we sought to improve the efficiency of CRISPR/Cas9 mediated TCR knockin (KI) into the TRAC locus of primary human T cells. In addition to the previously reported DNA-dependent protein kinase inhibitor M3814, we demonstrate that PI-103 and samotolisib markedly increase KI efficiency in a process that is GMP-compatible, while CC-115 had a variable effect. Importantly, PI-103 and samotolisib do not negatively impact cell viability, fold-expansion nor T cell phenotype and we conclude that they are suitable for the generation of gene-modified T cells for clinical use.

bioengineering↗