Focused ultrasound delivery of enzyme replacement therapy to the brain of Gaa-/- Pompe disease mice.

Clinically used enzyme replacements therapies (ERTs) have been successful in mitigating peripheral tissue pathology in patients with infantile onset (IOPD) and late onset (LOPD) Pompe disease (PD). However, none of the approved therapies are known to cross the blood brain barrier (BBB) and patients with PD have progressive central nervous system (CNS)-associated impairments due to lysosomal glycogen accumulation in the CNS. Here we investigate the use of focused ultrasound (FUS) to temporarily open the BBB as a treatment strategy for achieving delivery of intravenously administered recombinant human acid alpha glucosidase enzyme (rhGAA) into targeted regions of the mouse brain. We investigated GAA delivery and glycogen accumulation in 5-month-old Gaa-/- knockout mice following administration of two clinically available rhGAA ERTS (alglucosidase alfa and avalglucosidase alfa) at different dosages with and without FUS-BBB opening over four biweekly treatment sessions. BBB opening was targeted specifically to the striatum and cortex bilaterally in the FUS groups. Diphenhydramine was administered intraperitoneally 10 min before ERT to avoid anaphylactic response. Mice were sacrificed 24 h after the last treatment session. One hemisphere was used for histological analysis based on periodic acid Schiff (PAS) and H&E stained sections. The other hemisphere was used for biochemical assays to measure GAA enzyme activity and glycogen content. Contrast MRI showed consistent BBB opening over all mice treated with FUS with no significant differences in extent of BBB opening between hemispheres or treatment session. We observed significant reductions in the level of PAS staining for FUS + ERT treated mice compared to No FUS + ERT treated mice, indicative of successful ERT delivery across the BBB resulting in glycogen clearance. Biochemical analysis supported these results, showing an increase in GAA enzyme activity and reduction in glycogen content for FUS + ERT treated mice compared to No FUS + ERT groups. Future work will determine if this promising treatment paradigm can rescue disease phenotypes that are downstream of glycogen accumulation and work towards clinical translation.