Genetic Modification and Novel Cell Therapies in Non-Human Primate Hematopoietic Cells

National Heart, Lung, And Blood Institute

Investigators

Linked publications, trials & patents

Abstract

For successful gene transfer to target cells including primitive hematopoietic cells and other therapeutic blood cell types, several requirements need to be achieved. These include identification of the desired target cell population, optimizing the delivery system to be used, and achieving desired levels of gene expression. To date, successful gene transfer in human subjects remains a significant challenge. Nonhuman primates (NHPs) provide a critical bridge to clinical application by enabling the evaluation of novel gene and cell therapies under conditions that closely mimic human hematopoiesis, immunity, cardiopulmonary physiology, and stem cell biology. Their physiological similarity to humans supports comprehensive assessments of pharmacology, biodistribution, immunogenicity, and long-term safety via longitudinal clonal tracking methods. Vectors tested in this model include self-inactivating retroviral vectors and lentiviral vectors specifically designed to transduce rhesus hematopoietic stem cells (HSCs) and immune cells. These constructs have been engineered to express reporter genes such as enhanced green fluorescent protein (eGFP) and the sodium/iodide symporter (NIS), as well as therapeutic genes such as hemoglobin. In addition, innovative gene-editing approaches, including CRISPR/Cas9, are being explored in rhesus HSC transplantation studies. Beyond gene therapy, regenerative applications—such as the use of pluripotent stem cell–derived cardiomyocytes for cardiac repair—have also been evaluated in this preclinical model. In the past year, we completed five major studies published in highly regarded journals, including Cell Stem Cell and Blood. First, we evaluated two highly promising antibody-based conditioning regimens: anti-cMPL–mediated non-genotoxic conditioning and a CD45 antibody–drug conjugate conditioning strategy, with a goal to advance HSC gene therapies for patients with severe hematologic disorders. In addition, we optimized lentiviral delivery of barcoded anti-CD20 chimeric antigen receptors into rhesus macaque and human natural killer cells, an essential step toward enabling preclinical studies that will support eventual clinical translation. We also reported a study involving long-term tracking of hematopoietic clonal dynamics and mutations in a preclinical transplant model, providing important insights into long-term HSPC behavior in vivo following transplantation and gene therapy interventions. Finally, we completed in vivo tracking of 89Zr-oxine–labeled plasma cells using PET imaging, demonstrating the value of NHP as a model to evaluate B cell–based therapeutics for the treatment of human diseases. Ongoing studies aim to further optimize and advance novel antibody conditioning–mediated HSC gene therapies, as well as to develop efficient in vivo gene therapies using targeted lipid nanoparticles. Collaborative efforts across intramural and extramural programs are actively underway to validate these technologies and assess their safety and efficacy in the NHP model system. In addition, New Approach Methodologies (NAMs)—including the use of primary human cells, organoids, and microphysiological systems—are being leveraged to accelerate candidate screening and reduce reliance on animal models.