(J-388) Site-specific Brain Therapeutics

The brain is comprised of multiple regions performing distinct functions. Within each of these regions, there are multiple cell types that can affect brain physiology. Finally, within each cell there are multiple signaling pathways, that, when activated or inhibited, control the cell’s activity, and consequently the physiology of the entire brain. For these reasons, methods that can control the brain with regional, cell-type, and molecular precision have been widely used in neuroscience. However, so far, these approaches relied either on gene delivery or placement of invasive devices. While gene therapy holds a great promise, the risks of genomic integration, vector toxicity, vector-directed immune response, and costs pose significant challenges. On the other hand, invasive devices enable site-specific delivery of drugs, but also surgically damage the modulated brain region, carrying risks of infection and hemorrhage. Here, we present a new approach that can provide multi-day, noninvasive, site-, cell-type, and molecularly specific control over cells in the brain without the need to use invasive devices or gene delivery.

We demonstrated the feasibility of RAID approach by localized delivery of a luciferase enzyme RLuc8.6 that was engineered to be retained in the brain, allowing us to preserve its activity for at least 7 days. Afterwards, we chose to modify aromatic-L-amino-acid decarboxylase (AADC), which can convert a prodrug, L-DOPA, to neurotransmitter dopamine. We fused AADC with a peptide (IKVAV) to attach it to the brain interstitial space and improve long-term retention in the brain. AADC delivery followed by L-DOPA administration reduced the counter-clockwise rotations in the open field test by 63±10% in mice with full RAID treatment (Fig. 1b, n = 14 mice, P = 0.0018, Two-way ANOVA test) but not in the control mice with FUS alone or no treatment at all (n = 11 mice for FUS alone group, n = 12 mice for wild-type group; P = 0.9992 and 0.6019 respectively, Two-way ANOVA test). We also found RAID-treated mice exhibited a 7.6(±2.2)-fold increase in ipsilateral c-Fos-positive cells (Fig. 1c, n = 14 mice, P = 0.0006, Two-way ANOVA test), whereas no significant changes were observed in untreated mice or mice treated with FUS alone (n = 12 mice for wild-type group, n = 11 mice for FUS alone group; P > 0.9999 and P = 0.6723 respectively, Two-way ANOVA test). Overall, the RAID paradigm enabled noninvasive, tunable, temporally-resolved, site-specific, non-genetic, neuromodulation over multiple days. RAID paradigm is versatile and can be applied to any enzyme and prodrug pair to control various aspects of central nervous system physiology.