GC801-enabled AAV gene therapy in a neonate with Pompe disease

We report a neonate with IOPD who had high pre-existing anti-AAV9 antibody titers, which precluded eligibility for AAV9-mediated gene therapy (GC301). Preconditioning with a single dose of the IgG-degrading enzyme GC801 (0.2 mg/kg) safely reduced serum IgG from 6.25 g/L to a nadir of 0.72 g/L within 5 days. This pharmacological window facilitated successful GC301 vector transduction, driving a robust increase in GAA activity to 19.38 mmol/L/16h by day 84. Crucially, no adverse events beyond the underlying IOPD were observed. Our findings support the potential utility of GC801 as an agent to overcome pre-existing humoral barriers in neonatal gene therapy candidates.