Yuanyue Zhou

A foundation for universal T-cell based immunotherapy: T cells engineered to express a CD19-specific chimeric-antigen-receptor and eliminate expression of endogenous TCR.

Clinical-grade T cells are genetically modified ex vivo to express a chimeric antigen receptor (CAR) to redirect specificity to a tumor associated antigen (TAA) thereby conferring antitumor activity in vivo. T cells expressing a CD19-specific CAR recognize B-cell malignancies in multiple recipients independent of major histocompatibility complex (MHC) because the specificity domains are cloned from the variable chains of a CD19 monoclonal antibody. We now report a major step toward eliminating the need to generate patient-specific T cells by generating universal allogeneic TAA-specific T cells from one donor that might be administered to multiple recipients. This was achieved by genetically editing CD19-specific CAR(+) T cells to eliminate expression of the endogenous αβ T-cell receptor (TCR) to prevent a graft-versus-host response without compromising CAR-dependent effector functions. Genetically modified T cells were generated using the Sleeping Beauty system to stably introduce the CD19-specific CAR with subsequent permanent deletion of α or β TCR chains with designer zinc finger nucleases. We show that these engineered T cells display the expected property of having redirected specificity for CD19 without responding to TCR stimulation. CAR(+)TCR(neg) T cells of this type may potentially have efficacy as an off-the-shelf therapy for investigational treatment of B-lineage malignancies.

Functional footprinting of regulatory DNA

Regulatory regions harbor multiple transcription factor (TF) recognition sites; however, the contribution of individual sites to regulatory function remains challenging to define. We describe an approach that exploits the error-prone nature of genome editing–induced double-strand break repair to map functional elements within regulatory DNA at nucleotide resolution. We demonstrate the approach on a human erythroid enhancer, revealing single TF recognition sites that gate the majority of downstream regulatory function.

53. From GWAS To the Clinic: Genome-Editing the Human BCL11A Erythroid Enhancer for Fetal Globin Elevation in the Hemoglobinopathies

We describe here a fundamentally novel way to approach the development of a therapeutic: use of data from genome-wide association studies (GWAS) as a guide to create, in a targeted fashion, a disease-ameliorating genotype in the patients own cells. We exemplify this by focusing on the hemoglobinopathies, β-thalassemia and sickle cell disease (SCD): in both cases elevated levels of fetal hemoglobin (HbF) have been shown to lessen or eliminate disease symptoms. Thus, reversing HbF silencing in patients is an attractive strategy for the development of therapies. To this end, GWAS data pointed to loss-of-function variants in the erythroid-specific enhancer of the fetal globin repressor, BCL11A, as causative for HbF elevation. While such regulatory elements are challenging to affect in a clinical setting via a conventional small molecule approach, the development of genome editing with engineered nucleases allows, in principle, a targeted intervention at the DNA level to disable enhancer function. Here, we reduce this notion to practice.The BCL11A enhancer consists of three separate cis-regulatory elements spanning a total of~1,500 bp that together drive erythroid-specific expression of BCL11A and lead to a silencing of fetal hemoglobin post-birth. Guided in part by fine-scale in vivo protein-DNA interaction data, we performed a reverse-genetic analysis of the enhancer at its endogenous location in the physiologically relevant cell type, primary human erythroid cells, using zinc finger nucleases (ZFNs). We developed highly optimized ZFNs that yield 60-80% target locus editing in human mobilized peripheral blood CD34 cells. Remarkably, we find that the ZFN-driven ablation of a single 5 bp element, GATAA, resident in the enhancer reproducibly elevates fetal globin in erythroid progeny of these CD34 cells to levels indistinguishable from those resulting from an essentially complete ZFN-driven coding knockout of BCL11A itself. We demonstrate high-efficiency ZFN-driven marking at the enhancer in peripheral blood mobilized CD34 cells at clinical scale production in a GMP-compliant setting, observe the successful engraftment and differentiation of genome-edited cells in an immunodeficient mouse model, and use an unbiased deep-sequencing based assay to comprehensively characterize the nucleus-wide specificity profile of ZFN action.Together these data illustrate the feasibility of using findings from genome-wide association studies to pursue novel therapeutic approaches in monogenic disease. In particular, our work supports the further development of fetal globin elevation via the targeted genome editing of the BCL11A erythroid-specific enhancer in both peripheral blood- and bone marrow-derived CD34 cells as a potential treatment for the hemoglobinopathies.

Disruption of the BCL11A Erythroid Enhancer Reactivates Fetal Hemoglobin in Erythroid Cells of Patients with β-Thalassemia Major

In the present report, we carried out clinical-scale editing in adult mobilized CD34+ hematopoietic stem and progenitor cells (HSPCs) using zinc-finger nuclease-mediated disruption of BCL11a to upregulate the expression of γ-globin (fetal hemoglobin). In these cells, disruption of the erythroid-specific enhancer of the BCL11A gene increased endogenous γ-globin expression to levels that reached or exceeded those observed following knockout of the BCL11A coding region without negatively affecting survival or in vivo long-term proliferation of edited HSPCs and other lineages. In addition, BCL11A enhancer modification in mobilized CD34+ cells from patients with β-thalassemia major resulted in a readily detectable γ-globin increase with a preferential increase in G-gamma, leading to an improved phenotype and, likely, a survival advantage for maturing erythroid cells after editing. Furthermore, we documented that both normal and β-thalassemia HSPCs not only can be efficiently expanded ex vivo after editing but can also be successfully edited post-expansion, resulting in enhanced early in vivo engraftment compared with unexpanded cells. Overall, this work highlights a novel and effective treatment strategy for correcting the β-thalassemia phenotype by genome editing.