CRISPR-Cas Editing as a Genetic Cure for Autosomal Dominant Polycystic Kidney Disease

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PROJECT SUMMARY Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic disorder in the world and affects 650,000 Americans. ADPKD is caused by mutations in Pkd1 or Pkd2 that trigger proliferation and fluid secretion by renal tubular epithelial cells into cysts, which bilaterally enlarge the kidney and lead to progressive loss of kidney function. There is no cure for ADPKD with most patients requiring renal replacement therapy in the form of dialysis or transplantation by age 55 years to sustain life. Gene therapy to restore functional levels of the polycystin-1 (Pkd1) or polycystin-2 (Pkd2) gene products offers a promising, innovative therapeutic approach for ADPKD that could serve as an outright cure. However, the development of ADPKD gene therapy has been hindered by the lack of an efficient DNA delivery vehicle to renal tubular epithelial cells and by a one-size-fits-all gene editing solution. In collaboration with our academic partner, Stanford University, we developed several adeno-associated virus (AAV) capsid variants that efficiently transduce the kidney in vivo. The goal of this project is to perform lead optimization for these novel AAV capsids and use them to establish feasibility for a curative ADPKD gene therapy with CRISPR-Cas editing. Our studies will focus on Pkd1 as a proof-of-concept because Pkd1 accounts for 85% of all clinical ADPKD cases and Pkd1 mutations are associated with an earlier onset of kidney failure (more severe disease) than Pkd2. In Specific Aim #1, we will use base or prime editing to inactivate the miR-17 motif within the 3’ UTR of Pkd1 in both human and mouse ADPKD renal tubular epithelial cells in vitro. Preclinical studies have shown that removing or suppressing this miR-17 motif is a mutation-agnostic approach that reverses and attenuates ADPKD progression. We will evaluate several CRISPR editors, guide RNAs, and delivery vehicles to achieve optimal editing efficiency. We will use our published 3-D cell culture model of cystogenesis to evaluate the phenotypic and gene expression changes induced by CRISPR editing. In Specific Aim #2, we will further optimize in vivo delivery of our AAV capsid variants by testing various surgical modifications to the intra-renal artery injection method and testing new promoters. This delivery method is an attractive translational approach because the vessels can be accessed via conventional catheterization to allow for minimally invasive delivery in humans without requiring surgery. We will use the optimized delivery method identified from these studies to deliver the most efficient editing therapeutics from Aim #1 to ADPKD mouse models. At the conclusion of these studies, we expect to demonstrate feasibility for our ADPKD gene therapy approach and identify a lead candidate to advance for preclinical IND-enabling studies (Investigational New Drug application). Our Phase II STTR proposal will focus on completing these IND-enabling studies to enable us to file our IND application and initiate clinical trials. This potentially, curative therapeutic approach for ADPKD addresses a large unmet need given the lack of curative treatment options and has the potential to fundamentally alter the standard of care.