CRISPR/Cas9-mediated KLKB1 Gene Editing and Serum Kallikrein Reduction by NTLA-2002 Remains Durable in Humanized Mice Following Liver Regeneration after Partial Hepatectomy

Hereditary angioedema (HAE) is a rare genetic disorder characterized by recurrent, debilitating, and potentially fatal swelling episodes requiring chronic treatment. NTLA-2002 is a CRISPR/Cas9-based therapeutic candidate targeting KLKB1 as a single-dose treatment for the life-long prevention of HAE attacks. Previous studies demonstrated KLKB1 editing is sustained for at least 24 months in non-clinical animal models, suggesting the edit is permanently maintained throughout regular cell turnover. To further demonstrate durability of effect in the context of exaggerated cellular proliferation, we developed a partial hepatectomy (PHx) model to force rapid and extensive tissue regeneration following NTLA-2002 treatment. Humanized KLKB1 mice (huKLKB1) were administered NTLA-2002 at 0.1 mg/kg and 0.3 mg/kg by single IV injection. After 14-months, a sham or PHx surgery was performed. Liver tissue and blood was collected during PHx and at necropsy for editing and serum kallikrein analysis. Animals treated with 0.1 mg/kg of NTLA-2002 showed 51% editing and 48% serum kallikrein knockdown prior to PHx and 49% editing and 44% serum kallikrein knockdown after liver regeneration. Animals treated with 0.3 mg/kg of NTLA-2002 showed 74% editing and 91% serum kallikrein knockdown prior to PHx and 71% editing and 94% serum kallikrein knockdown after liver regeneration. No differences were observed between the sham and PHx groups for all treatment groups. KLKB1 editing and serum kallikrein reduction is retained at both dose levels following PHx-induced liver regeneration, demonstrating the permanence of CRISPR-Cas9-induced genetic editing. These data further support the development of NTLA-2002 as a potential single-dose treatment for patients with HAE.