Changes in Core Temperature Following Administration of FC5, a Blood–Brain Carrier Fused with Neurotensin in Mice, Rats and Non-Human Primates

Development of therapies and pharmacological management of central nervous system diseases is significantly hampered by the presence of the highly selective blood–brain barrier (BBB). Receptor-mediated transcytosis (RMT) has proven to be a robust mechanism for delivering a wide variety of therapeutic modalities across the BBB. The present study describes the use of a neurotensin-based pharmacodynamic model to evaluate the brain penetrating capacity of FC5, a well-characterized RMT shuttle. Here we produce fusion molecules of FC5 with human Fc and neurotensin and show that intact but not C-terminally clipped neurotensin proteins containing either FC5 (FC5Fc-neurotensin) or a non-BBB-crossing control (A20.1Fc-neurotensin) retain the ability to activate neurotensin receptor type 1. In in vivo studies, intravenous administration of FC5Fc-neurotensin, but not neurotensin alone or A20.1Fc-neurotensin, induced a drop in the core body temperature in both rats and mice. We further extended these findings to non-human primates, demonstrating the ability of FC5 to cross the BBB in this species. Collectively, our results further support the potential of FC5 in delivering payloads across the BBB. The neurotensin model of hypothermia is also validated as a pharmacodynamic approach for assessing brain delivery, albeit with some necessary considerations into the molecular characterization of fusion constructs before in vivo evaluation.