Developing Genome-Edited Stem Cells for Therapy of Patients: Assessing Efficacy and Toxicology
Lecturer: Matthew H. Porteus, Stanford University,
Genome editing provides a mechanism to precisely
alter the DNA sequence of a cell. The most efficient
mechanism to achieve genome editing is to induce a
site-specific DNA double-strand break at the genomic target site to be modified, thereby activating the cell’s own repair machinery. The CRISPR-Cas9-gRNA system has accelerated the field of genome editing because of its ease of use, its high on-target activity, and its high specificity compared to other nuclease platforms. If a donor template is provided along with the nuclease, the cell will use that donor template to repair the break by homologous recombination and precise sequence changes can be introduced into the target gene. We have focused our efforts on developing a clinically compatible method of engineering human primary blood cells, including hematopoietic stem
cells, by homologous recombination. Using this system, we now achieve gene editing by homologous recombination frequencies of 40–80% in CD34+ hematopoietic stem and progenitor cells and 20–50% in primary human T cells. The translation of this process to the clinic for
genetic diseases of the blood and immune system, including sickle cell disease, and our ability to use homologous recombination to engineer complex phenotypes in primary human T cells will be discussed. As genome-edited primary human cells are a novel therapeutic, a careful assessment of the safety and toxicology of such products is critical.
Traditional methods of evaluating such toxicology using the paradigms of small molecules or biologics may not be appropriate for this different class of therapeutics. Genetically engineered cell based therapeutics have a different PK/PD profile, for example, that needs to be considered. I will
discuss some of the approaches we have taken to evaluate safety and toxicology in our genome-edited cell based products.