Blood‐brain barrier transport using a high affinity, brain‐selective VNAR antibody targeting transferrin receptor 1

Authors:
Open Access
Publisher website
Google Scholar
Abstract
Transfer across the blood‐brain barrier (BBB) remains a significant hurdle for the development of biopharmaceuticals with therapeutic effects within the central nervous system. We established a functional selection method to identify high affinity single domain antibodies to the transferrin receptor 1 (TfR1) with efficient biotherapeutic delivery across the BBB. A synthetic phage display library based on the variable domain of new antigen receptor (VNAR) was used for in vitro selection against recombinant human TfR1 ectodomain (rh‐TfR1‐ECD) followed by in vivo selection in mouse for brain parenchyma penetrating antibodies. TXB2 VNAR was identified as a high affinity, species cross‐reactive VNAR antibody against TfR1‐ECD that does not compete with transferrin or ferritin for receptor binding. IV dosing of TXB2 when fused to human Fc domain (TXB2‐hFc) at 25 nmol/kg (1.875 mg/kg) in mice resulted in rapid binding to brain capillaries with subsequent transport into the brain parenchyma and specific uptake into TfR1‐positive neurons. Likewise, IV dosing of TXB2‐hFc fused with neurotensin (TXB2‐hFc‐NT) at 25 nmol/kg resulted in a rapid and reversible pharmacological response as measured by body temperature reduction. TXB2‐hFc did not elicit any acute adverse reactions, bind, or deplete circulating reticulocytes or reduce BBB‐expressed endogenous TfR1 in mice. There was no evidence of target‐mediated clearance or accumulation in peripheral organs except lung. In conclusion, TXB2 is a high affinity, species cross‐reactive, and brain‐selective VNAR antibody to TfR1 that rapidly crosses the BBB and exhibits a favorable pharmacokinetic and safety profile and can be readily adapted to carry a wide variety of biotherapeutics from blood to brain.
Funding Information
  • Lundbeck Foundation (R155‐2013‐14113)

This publication has 50 references indexed in Scilit: