Liver injury in cynomolgus monkeys following intravenous and intrathecal scAAV9 gene therapy delivery.

Hepatotoxicity associated with intravenous/intrathecal adeno-associated virus (AAV) gene therapy has been observed in preclinical species and patients. In nonhuman primates, hepatotoxicity following self-complementary AAV9 administration varies from asymptomatic transaminase elevation with minimal to mild microscopic changes to symptomatic elevations of liver function and thromboinflammatory markers with microscopic changes consistent with marked hepatocellular necrosis and deteriorating clinical condition. These transient acute liver injury marker elevations occur from 3-4 days post intravenous administration to ∼2 weeks post intrathecal administration. No transaminase elevation or microscopic changes were observed with intrathecal administration of empty capsids or a "promoterless genome" vector, suggesting that liver injury after cerebrospinal fluid dosing in nonhuman primates is driven by viral transduction and transgene expression. Co-administration of prednisolone after intravenous or intrathecal dosing did not prevent liver enzyme or microscopic changes despite a reduction of T lymphocyte infiltration in liver tissue. Similarly, co-administration of rituximab/everolimus with intrathecal dosing failed to block AAV-driven hepatotoxicity. Self-complementary AAV-induced acute liver injury appears to correlate with high hepatocellular vector load, macrophage activation, and type 1 interferon innate virus-sensing pathway responses. The current work characterizes key aspects pertaining to early AAV-driven hepatotoxicity in cynomolgus macaques, highlighting the usefulness of this nonclinical species in that context.