rAAV9 vector biodistribution in nonhuman primate brain and spinal cord following lumbar intrathecal infusion

Delivery of recombinant adeno-associated virus serotype 9 (rAAV9) into cerebrospinal fluid bypasses the blood-brain barrier and can permit efficient brain tissue transduction. Whereas intracisterna magna injection (ICM) and other routes have been considered, lumbar intrathecal (IT) delivery offers a minimally invasive approach for treating genetic disorders of the central nervous system. To evaluate central nervous system biodistribution, we quantified vector genome (vg) copies of five rAAV9 vectors in cynomolgus macaques following ICM or lumbar IT delivery.

A total of 48 animals were followed across five studies: four lumbar IT infusion studies with four recombinant adeno-associated virus serotype 9 vectors (TSHA-101, -102, -105, and -120); and one ICM infusion study (TSHA-102 only). Stock vectors were diluted to dosing concentrations and 2.5 mL were administered to each animal. After animals were sacrificed, tissue samples were harvested and biodistribution was assessed via qPCR.

Despite protocol differences specifying different doses (human effective dose range, 2.6 × 10¹³ to 2.0 × 10¹⁵ vg), necropsy times (1 month to 1 year), and central nervous system tissues harvested, rAAV9 DNA levels in the brain and spinal cord were generally dose-dependent and consistent across tissues. At comparable doses and times, IT and ICM delivery led to widespread and consistent distribution of vector genomes, approximating 1 vg/diploid host genome throughout the brain at the higher doses tested.

These findings support IT administration as an effective, minimally invasive approach to central nervous system-directed gene therapy.