Exploring AAV gene therapy for Alport syndrome using a dog model

About This Grant

PROJECT SUMMARY Alport Syndrome (AS) is a monogenic disease primarily caused by a deficiency of functional type IV collagen a chains (COL4A3/4/5), matrix proteins that play a crucial role in maintaining the structural integrity of basement membranes in the kidneys, ears, and eyes, leading to progressive chronic kidney disease (CKD), hearing loss and ocular impairment, respectively. Although all three manifestations in this triad are equally devastating and diminish the quality of life for affected individuals, kidney involvement is particularly severe and often life- threatening. Importantly, AS is the second most prevalent genetic kidney disease that leads to CKD and, ultimately, kidney failure (KF). Despite its relatively high prevalence among the rare genetic diseases, estimated to be 1 in 2,000 to 5,000 people, current clinical pharmacological therapy for AS-related CKD is limited to the treatment with angiotensin-converting enzyme inhibitors, which only partially delays the progression of CKD. Currently, there is no curative therapy for the disease. Therefore, there is an urgent, unmet need for innovative and more effective CKD therapies for AS. In recent years, significant progress has been made in the field of adeno-associated virus (AAV) vector-mediated gene therapy for monogenic diseases, leading to the approval of commercial products. Despite the immense potential of AAV vectors to treat genetic diseases and the compelling nature of genetic kidney diseases, including AS, as gene therapy targets, AAV vector-mediated gene therapy for genetic kidney diseases has remained underexplored. This is primarily due to the challenge in effectively delivering genes to the kidney even with AAV vectors. Moreover, AAV gene therapy for AS faces an additional challenge in that the size of the therapeutic gene payload encoding COL4A3, COL4A4, and COL4A5 chains exceeds the packaging capacity of AAV vectors. In this regard, notably, the Nakai (PD/PI) lab has recently achieved a breakthrough by devising a novel AAV vector approach that can mediate effective expression of the full-length COL4A5 protein in podocytes and allows its expression, secretion, and deposition in the glomerular basement membrane in the kidneys of AS mouse models. This breakthrough has warranted assessment of its efficacy using clinically relevant large animal models. While non-human primate models for AS do not exist, a well-established AS dog model is available, the X-linked AS (XLAS) dog model that has been extensively studied and maintained by the Nabity (MPI) lab. Given this background, this collaborative, exploratory multi-PI project between the Nakai and Nabity labs aims to demonstrate proof of concept of AAV vector-mediated gene therapy for AS in an XLAS dog model and investigate AAV vector biology, pharmacokinetics, biodistribution, off-target effects, and immune responses in this dog model. Success in the project will significantly spur the development of AAV gene therapy for AS and further our knowledge of AAV vector biology in the AS context, which is essential for successful clinical translation. Furthermore, the project outcomes will have substantial implications for the treatment of other CKDs, whether of genetic or non-genetic etiologies.