Curing Sickle Cell Disease with CRISPR-Cas9 genome editing

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Sickle Cell Disease (SCD) is a devastating recessive genetic disorder, afflicting ~100,000 Americans (3), ~6000 Californians, and hundreds of thousands more worldwide (4). It typically shortens lifespan by decades even with optimal medical care. SCD is caused by a single mutation in the ß-globin gene; gene editing can directly correct the mutation. We have developed an autologous stem cell product that uses a CRISPR/Cas9 nuclease to stimulate repair of the sickle mutation in blood stem cells. Editing reproducibly yields levels of correction that, based on clinical experience, will be sufficient for a curative effect. We propose to complete preclinical development of this therapy, leading to an IND application for an early phase clinical trial in adults with severe SCD. We held a pre-IND meeting on October 30, 2018, and request CIRM funding for the following activities to support IND submission as discussed with the FDA: 1. Demonstrate the capacity to manufacture final cell product under GMP conditions at clinical scale. We will generate at least 3 clinical-scale lots under cGMP that meet all release criteria, in plerixaformobilized HSPCs. We will also complete a drug product stability study. These reports will complete the CMC section of the IND. 2. Complete a rigorous genotoxicity assessment. A murine xenograft model that supports human hematopoietic cells will be used to perform a toxicology study on final cell product manufactured under cGMP conditions. After long-term engraftment, mice will be assessed for evidence of malignant human cells using histopathology, flow cytometry, and genomic readouts. (pre-IND Question 8). 3. Complete additional preclinical studies to establish product safety and potency. An exhaustive interrogation for off-target genomic modifications with the final manufacturing reagents will address potential genotoxicity. We will also assess large deletions and translocations at the HBB on-target site, the nature and potential impact of HBB mutations induced by the editing procedure, and evidence of clonal expansion that could reflect early-stage neoplastic progression (pre-IND Questions 5,11). 4. Draft and file an IND with a final clinical trial design. We will generate a final clinical protocol, consent form, and data and safety management plan to support the IND for a Phase I clinical trial of safety and feasibility in adults with severe SCD. We will submit these for required regulatory (e.g. IRB, IBC, NIH RAC) review, pending final approval of IND. This therapy has the potential to transform the care of SCD by producing a curative treatment that is applicable to any SCD patient and safer than allogeneic hematopoietic stem cell transplantation (HSCT), thus making it possible to prevent complications of SCD before they have done irreversible damage.