Prevention of corneal transplant rejection using AAV-HLA-G combination therapy

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Contact PD/PI: GILGER, BRIAN C Abstract Corneal blindness is a leading cause of global blindness, with allogeneic corneal transplantation (CT) being the most common form of tissue transplantation worldwide. Though approximately 180,000 CT surgeries are carried out each year, around 12.7 million are currently awaiting a donor cornea to undergo the operation. Still, CT surgery is accompanied by a high failure rate: as many as 20–30% of corneal grafts are rejected within the first 5 years in the general population, and in high-risk cases, which represent over 20% of the population, almost all grafts are rejected within 3 years. CT failure puts a strain on the already-limited supply of donor corneas, for which there is approximately only one cornea available for every 70 needed. Whether by lack of access or unsuccessful intervention, the vast majority of cases of corneal blindness go untreated, leaving patients with limited mobility, an increased risk of falls, emotional distress, and an increase in mortality. Current approaches to mitigate corneal graft rejection involve topical and systemic corticosteroids and immunosuppressive agents, but these methods are all burdened with acute disadvantages; corticosteroids have been known to induce vision loss, and immunosuppressive agents, besides incurring serious potential side effects, also come at a high price. To address the critical need for methods to reduce graft failure and improve the long-term success of allogeneic human CT, Bedrock Therapeutics proposes to use adeno-associated virus (AAV)-mediated transduction to deliver HLA-G isoforms to donor corneal grafts to ultimately modulate the immunologic response of a human recipient and prevent rejection following CT. This Phase I proposal focuses on the ex vivo optimization of identified variables that affect AAV vector transduction of corneal explants. Treatment efficacy and feasibility will be targeted through the pursuit of two specific aims: 1) optimization of AAV-HLA- Gcombo ex vivo transduction variables (i.e., vector production, dose, and incubation time), and 2) evaluation of AAV-HLA-Gcombo ex vivo transduction efficacy in a high-risk rabbit allogenic CT model. Bedrock Therapeutics' previous studies have demonstrated the feasibility of using AAV8G9 to transduce HLA-G isoforms into donor corneas and the resulting successful prevention of graft rejection in animal models of allogeneic CT. Transduction of HLA-G into rabbit corneas prior to transplantation resulted in complete prevention of allogeneic graft rejection over an 80-day period vs. rejection at 10 days in control corneas. Successful application of this method will provide a platform for obtaining immune-tolerant corneas, addressing the high rate of corneal graft rejection and ameliorating current tissue shortage problems. Completion of the proposed work will pave the way for additional preclinical and clinical studies with an eventual goal of applying our platform to human CT in order to improve the quality of life of the thousands of patients that experience corneal rejection each year. Project Summary/Abstract Page 6