Preclinical Optimization and Design for Manufacturability of Immunoregulatory TEVGs

PROJECT SUMMARY/ABSTRACT Despite the emergence of a few companies in recent years based on the clinical translation of small diameter tissue-engineered vascular grafts (TEVGs), the gold standard for arterial bypass in the clinic continues to be autologous vein or artery grafts. Our team has developed, with previous NIH funding (including NHLBI Catalyze R61 funding), TEVGs based on the documented pro-regenerative immunoregulatory potency of mesenchymal stem/stromal cells (MSCs). MSCs are immunoregulatory in that they recruit host neutrophils and macrophages via secreted factors and modulate the recruited cells to a tolerant and pro-regenerative phenotype. We have also demonstrated that MSCs can stimulate the production of new functional vascular extracellular matrix both in vitro and in vivo and that MSCs play an acute antithrombogenic role in our TEVGs. We have also successfully tested in vivo cell-free TEVG strategies based on immunoregulatory factors secreted by MSCs via extracellular vesicles (EVs). Data generated during the previous R61 funding has led us to select one TEVG configuration that passed our R61 milestones with acceptable critical quality attributes (CQAs) – a silk scaffold seeded with EVs – to proceed on to testing in the R33 phase. Our proposed project is ideal for the R33 Catalyze grant mechanism and successful completion will lead to a pre-IDE meeting with the FDA toward the clinical translation of our TEVG device. We will perform final in vitro CQA analysis and in vivo validation of scaled-up, human-sized TEVGs through large animal testing for 8 weeks and 6 months. We will also address manufacturability of our TEVG device and develop regulatory and business connections. The objectives and stringent milestones for the project are summarized below: Objective R33.1: Evaluate our Silk+EV TEVG constructs in vitro using clinically-relevant and industry-standard measures of performance. Milestone R33.1: Silk+EV constructs demonstrate acceptable characteristics using in vitro CQA assessment. Objective R33.2: In vivo evaluation of human-sized Silk+EV TEVG constructs using a sheep carotid implantation model. Milestones R33.2a and R33.2b: At least (a) 90% of TEVGs remain patent after implantation for 8 weeks and (b) 80% for 6 months as carotid artery interposition grafts in a preclinical large animal model. Objective R33.3: Evaluate the manufacturability and regulatory aspects of the Silk+EV device configuration to prepare for pre-submission meeting with FDA. Milestone R33.3: IP protections secured, market analysis and business plan completed, data and paperwork in hand for pre-submission meeting with the FDA, and optimal, reproducible manufacturability of our TEVG.