Meganuclease targeting of PCSK9 in macaque liver leads to stable reduction in serum cholesterol.

Clinical translation of in vivo genome editing to treat human genetic diseases requires thorough preclinical studies in relevant animal models to assess safety and efficacy. A promising approach to treat hypercholesterolemia is inactivating the secreted protein PCSK9, an antagonist of the LDL receptor. Here we show that single infusions in six non-human primates of adeno-associated virus vector expressing an engineered meganuclease targeting PCSK9 results in dose-dependent disruption of PCSK9 in liver, as well as a stable reduction in circulating PCSK9 and serum cholesterol. Animals experienced transient, asymptomatic elevations of serum transaminases owing to the formation of T cells against the transgene product. Vector DNA and meganuclease expression declined rapidly, leaving stable populations of genome-edited hepatocytes. A second-generation PCSK9-specific meganuclease showed reduced off-target cleavage. These studies demonstrate efficient, physiologically relevant in vivo editing in non-human primates, and highlight safety considerations for clinical translation.