Development of U7snRNA Vectors for Dystrophinopathy
Above, virally-delivered U7snRNAs that target exons can induce significant exon skipping. In this example, the U7snRNA targets exon 2 within the mouse Dup2 model carrying a duplication of that exon. Complete skipping of exon 2 can still result in dystrophin expression via use of a downstream translational initiation site. Part of our project is directed toward harnessing this technology for other exons. Another part of our project is directed toward more detailed characterization of the Dup2 mouse, and comparison of it to another mouse model that makes no dystrophin whatsoever.
Principal Investigator
Kevin Flanigan, MD
Dr. Kevin M. Flanigan is a is a principal investigator in the Jerry R. Mendell Center for Gene Therapy at Nationwide Children’s Hospital, and a professor at The Ohio State University College of Medicine. He serves as director of the Paul D. Wellstone Muscular Dystrophy Specialized Research Center at Nationwide Children’s Hospital.
What Is the Goal of the Project?
Current therapeutic approaches in trials are directed toward expression of micro-dystrophin proteins. However, their success will likely ameliorate DMD into a BMD-like phenotype. We seek to develop a personalized medicine approach. Our long-term goal is to develop vectors that maximize RNA splice alteration efficiency to provide the best potential outcome for individual patients.
What Does This Project Entail?
Our central hypothesis is that vectorized exon skipping – packaging a non-coding U7 small nuclear RNA (U7snRNA) that alters splicing into an AAV vector – will provide a universally robust exon skipping response, leading to therapies with significant efficacy. For particularly rare mutations, such as single exon duplications within the rod domain of dystrophin, these may be considered personalized or bespoke therapies intended to alter the use of the existing exons within the DMD locus to express full-length dystrophin—the best potential therapeutic outcome. For other more common mutations, such as certain out-of-frame rod domain deletions, these will be applicable to broader patient populations; based upon both our published studies in mice and our publicly presented data in and infant patient with a duplication of exon 2, we can expect more robust exon skipping and protein expression than that seen with PMO therapies. We will test these extensively in myoblast cells derived from transdifferentiation of patient fibroblast cells.
We also propose to fully characterize two new mouse models of utility to the muscular dystrophy community. Our rationale for this project is that a systematic approach to vector design, efficacy assessment and evaluation of toxicity, along with early engagement with the FDA, will lead to a streamlined path toward vector development. The immediate impact of our work will be data to support our ongoing engagement with the FDA in developing rapid approaches to personalized gene therapies based upon programmatic (U7snRNA) vector development in cell-line models, obviating the need for large animal studies.
