Noninvasive Focal Gene Delivery into the Cerebellum of Non-Human Primates using Focused Ultrasound

Cerebellar degenerations are a heterogeneous group of disorders that pose significant clinical challenges, and no effective therapies are currently available to halt or slow their progression. Gene therapy offers important therapeutic potential for brain disorders; however, its clinical translation is hindered by critical obstacles, particularly the blood-brain barrier, which limits systemic delivery of therapeutic genes to the brain, an issue especially pronounced in primates. Here, we evaluated the use of low-intensity focused ultrasound combined with intravenously administered microbubbles to transiently open the blood-brain barrier in the cerebellum of macaque monkeys, thus enabling targeted delivery of adeno-associated virus-based gene therapy vectors. Two vector types (scAAV9-CBA-GFP and ssAAV9-CMV-mCherry) were administered systemically, and transgene expression was analyzed to assess delivery efficiency and cell-type distribution. We achieved successful, non-invasive delivery of both vector types to the cerebellum with high spatial precision. Administration of ssAAV9-CMV-mCherry vector resulted in robust transduction of virtually all neurons within the targeted deep cerebellar nuclei. These findings provide a promising and translationally relevant strategy for developing gene-delivery approaches for cerebellar and other neurodegenerative disorders and represent a step forward in advancing the use of focused ultrasound to achieve efficient and less invasive gene delivery to the brain.