H-ferritin nanoparticle-mediated antibody delivery across the blood-brain barrier

Therapeutic monoclonal antibodies (mAbs) show great promise for treating neurological disorders thanks to their high selectivity and potency. However, their clinical potential is significantly limited by poor penetration across the blood-brain barrier (BBB). It has been shown that antibodies targeting transferrin receptor 1 (TfR1) can reach the brain after peripheral administration. In addition, human H-ferritin (HFn) naturally undergoes TfR1-mediated transcytosis, making it a compelling alternative candidate platform for brain-directed drug delivery. This study evaluates the feasibility of using HFn as a generic shuttle to transport therapeutic antibodies into the brain.

An anti-BACE1 monoclonal antibody (1A11) was chemically conjugated to HFn, and the resulting nanoparticles (1A11-HFn NPs) were assessed in vitro and in vivo for their structural integrity, target binding, BBB permeability, BACE1 inhibition, and pharmacological effects. Hereto, HFn and the mAb 1A11 were produced in Escherichia coli and CHO cells, respectively, followed by purification of each protein. Conjugation of 1A11 to HFn was achieved using the heterobifunctional linker NHS-PEG-Mal, after which 1A11-HFn NPs were isolated. Binding to human BACE1 and human TfR1 was confirmed. Structural characterization was performed via transmission electron microscopy (TEM). Pharmacokinetics (PK) and pharmacodynamics (PD) were examined in humanized apical domain TfR1 knock-in (hApiTfrc KI) mice after intravenous (IV) administration, with evaluation of both plasma and brain tissue.

1A11-HFn NPs were successfully generated with confirmed dual binding to hBACE1 and hTfR1. TEM imaging verified the structural integrity of the nanoparticles. In vivo studies demonstrated increased brain levels of 1A11-HFn NPs at days 1 and 3 post-administration, though levels declined below the limit of detection (LOD) by day 7. The amount reaching the brain at day 1 but not day 3 or 7 was sufficient to inhibit BACE1 activity, indicating a pharmacological meaningful dose could reach the brain after peripheral administration.

These findings demonstrate that HFn can serve as an effective shuttle to deliver mAbs across the BBB at pharmacologically relevant concentrations. This work provides foundational evidence supporting HFn-based nanoparticles as a promising platform for brain-targeted delivery of biological therapeutics.