SCGE Disease Models Studies Supplement: Evaluation of prime editing for the amelioration of alpha-1-antitrypsin deficiency in murine and porcine models.

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PARTICIPATING AWARDS, INVESTIGATORS & INSTITUTIONS 4UH3TR002668-04, “Enhancing CRISPR Gene Editing in Somatic Tissues by Chemical Modification of Guides and Donors”, Drs. Erik Sontheimer and Scot Wolfe, University of Massachusetts Chan Medical School 1U24OD026641-01, “Development of Swine Reporter Models for Testing Somatic Cell Genome Editing Tools.”, Drs. Daniel Carlson and Jarryd Campbell, Recombinetics ABSTRACT Alpha-1 antitrypsin deficiency (A1AT) is a hereditary disorder caused by point mutations in SERPINA1 (SERine Proteinase INhibitor A1) that is characterized by low serum and low lung levels of AAT. The most common mutation is the “Z” (Glu342Lys) allele that reduces AAT in circulation due to retention in the liver leading to overactive proteases in the lung, and accumulation of the mutant misfolded AAT protein in hepatocytes. This leads to tissue destruction in the lungs (loss-of-function), and liver disease (gain-of-toxic-function) in many A1AT patients. More than 95% of people with severe A1AT are homozygous for the Z allele (PI*ZZ). The ideal therapeutic would repair the PiZ allele. Unfortunately, A1AT gene therapy to treat even one target pathology (lung or liver) has not yet been effectively translated to patients despite promising data in early mouse models of A1AT. Our team brings together expertise in A1AT gene therapy, preclinical animal models, RNA delivery, and prime editing technology. We propose to develop optimized prime editing reagents to repair the PiZ allele. With these reagents, we will perform dosage escalation studies in two unique mouse models of A1AT to measure gene repair outcomes and the subsequent effect on lung and liver phenotypes. The optimal dose from mice will be evaluated in our novel, humanized swine model of the PiZ allele with the primary goal of evaluating safety and target engagement. We believe this stepwise paradigm for therapeutic evaluation in two animal models will improve the likelihood of a successful outcome in subsequent clinical studies.