Enhancing antibody exposure within the central nervous system (CNS) is critical for developing therapeutic monoclonal antibodies (Mabs) to treat CNS disorders. However, limited antibody penetration across the blood-brain barrier (BBB) and rapid efflux from the cerebrospinal fluid hinder effective CNS delivery. While most research efforts focus on enhancing the permeation of antibodies across the BBB, here we present an alternative strategy to enhance antibody retention by directly binding hyaluronic acid (HA) in the brain's extracellular space. To accomplish this, we fused the G1 domain of versican (VG1), a proteoglycan known for HA binding, with nontargeting Fab and Mab (IgG) antibodies. Using single-photon emission computed tomography/X-ray computed tomography imaging, we tracked the biodistribution of 125I-labeled Fab- and Mab-(VG1)2 fusion constructs, as well as their parent antibodies, after direct infusion into the lateral ventricles of cannulated mice. Over 96 h, both VG1 constructs significantly enhanced antibody exposure in the brain and spine compared to the parent antibodies. Fab-VG1 exhibited a more widespread brain distribution, while Mab-(VG1)2 was localized around the administration site. Fluorescence microscopy demonstrated periventricular distribution of antibody with a greater depth of infiltration for Fab-VG1 across all ventricles at 1 and 96 h time points compared to Mab-(VG1)2. Escalating the dose of Fab-VG1 enhanced tissue penetration distance. These findings demonstrate the feasibility of using HA-binding technology to enhance antibody exposure in the CNS, offering potential for the development of more effective antibody-based therapies for CNS disorders.
Schwinghamer et al. (Tue,) studied this question.