Focused ultrasound-enhanced nose-to-brain delivery of a therapeutic antibody in a large-animal model

<b>Background:</b> The intranasal (IN) route offers a promising noninvasive strategy for central nervous system drug delivery bypassing the blood-brain barrier and reducing systemic exposure. However, its clinical translation is limited by low delivery efficiency and a lack of regional specificity in the brain. Here, we present the first demonstration of focused ultrasound-mediated intranasal delivery (FUSIN) in a large-animal model to address these limitations. <b>Methods:</b> Pigs were used to develop and characterize IN delivery, evaluate systemic exposure in major organs, and assess the feasibility and safety of FUSIN for delivering a therapeutic antibody, anti-programmed death-ligand 1 antibody (aPD-L1). The IN delivery was performed using a catheter-based approach, and successful delivery was confirmed with gadolinium-based contrast agents in combination with magnetic resonance imaging (MRI). Systemic exposure was assessed following IN administration of fluorescently labeled IRDye 800CW-aPD-L1, and its biodistribution was compared with intravenous (IV) injection of IRDye 700CW-aPD-L1. FUSIN delivery was performed by applying focused ultrasound (FUS) to predefined brain targets following IN administration to enhance local antibody accumulation. Delivery outcomes were assessed by <i>ex vivo</i> fluorescence imaging, followed by immunofluorescence staining, and safety was evaluated using susceptibility-weighted imaging (SWI). <b>Results:</b> IN delivery targeted the olfactory epithelium region and resulted in significant accumulation of 800CW-aPD-L1 in brain regions associated with the olfactory and trigeminal pathways, while markedly reducing off-target deposition in peripheral organs compared to IV administration. The application of FUS significantly increased local antibody accumulation at the targeted sites compared to contralateral non-sonicated controls. Immunofluorescence imaging revealed FUS-enhanced transport of the antibody from perivascular spaces into the brain interstitial space. SWI detected microhemorrhages under the current FUS parameters, highlighting the need for optimization to ensure safety. <b>Conclusion:</b> This study demonstrates the feasibility of FUSIN for noninvasive, region-specific brain drug delivery with minimized systemic exposure in a large-animal model.