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Friday, October 12 • 4:45pm - 5:00pm
Genome Editing to Fix the Sickle Cell Disease Causing Variant in Sickle Cell Patient Hematopoietic Stem Cells

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Dr. Matthew Porteus- StandFord University, Dr. Daniel Dever- StandFord University, Dr. Annalisa Lattanzi- StandFord University, Mr. Joab Camarena- StandFord University,Mr. Carsten Charlesworth- StandFord University, Dr. Helen Segal- StandFord University, Dr. Neehar Bhatia- StandFord University, Dr. David Digiusto- StandFord University

Objective: The objective our research program is to complete the pre-clinical work demonstrating the safety and efficacy of genome editing of somatic hematopoietic stem cells to correct the sickle cell disease causing variant in order to develop a strategy to potentially cure sickle cell disease.
Methods: We have developed a genome editing approach that utilizes the CRISPR/As9 nuclease system that directly corrects the sickle cell disease causing mutation in hematopoietic stem cells using homologous recombination. We isolate both healthy donor and patient derived CD34+ hematopoietic stem and progenitor cells (HSPCs). We then genetically modify these cells ex vivo using a combination of CRISPR/Cas9 nuclease and AAV6 transduction. We evaluate the efficacy of the approach by measuring the percent hemoglobin A in red blood cells derived from genome edited sickle cell patient HSPCs. We evaluate the safety and efficacy by measuring the how well the edited HSPCs engraft and generate blood cells following transplantation of the human cells into immunodeficient (NSG) mice. We measure safety by determining the location of potential off-target INDELs created by the CRISPR/Cas9 nuclease the frequency that INDELs are created at these sites in CD34+ HSPCs.
Results: In CD34+ HSPCs from sickle cell patients, we are able to achieve 60-80% allele correction of the sickle cell mutation. These edited cells give rise to red blood cells that express ~92% Hgb A and 8% Hgb S. When transplanted into mice, the percent allele correction remains above 50% in the human cells thus demonstrating that the modified cells retain their key stem cell properties--the ability to give rise to long-term hematopoiesis in an animal model. After transplantation there is no evidence of abnormal hematopoiesis from the human cells thus providing evidence of safety. When we use a high-fidelity version of Cas9, we detect off-target mutations at only a single site and this site is 95 kb away from the nearest protein coding gene and of no known functional significance. We have submitted a pre-IND application to the FDA and based on FDA feedback are performing the key experiments to file a successful IND to initiate a phase I/II clinical trial testing the strategy in patients. These experiments including scaling up the process to a clinical scale and performing more complete testing of safety in an animal model. These studies are ongoing and we will present ongoing results at the meeting.
Conclusions: Genome editing provides a potentially precise mechanism to genetically correct the disease causing variant that causes sickle cell disease. Our preclinical results are very promising and if we are able to complete our IND enabling experiments we hope to launch a phase I/II clinical trial testing the strategy in 2019.

avatar for Matthew Porteus, MD

Matthew Porteus, MD

Clinical Trial Specialist, Stanford University
Dr. Porteus is physician-scientist trained in Pediatric Hematology/Oncology who is an Associate Professor at Stanford University. His research program has focused on genome editing of hematopoietic stem and progenitor cells to develop cell based autologous cures for patients with... Read More →

Friday October 12, 2018 4:45pm - 5:00pm EDT
Constellation C