ENGINEERING BRAIN-PENETRANT NEUROTENSIN PEPTIDES FOR NON-OPIOID ANALGESIA

Neurotensin (NT) is a 13-amino-acid neuropeptide whose biologically active C-terminal fragment, NT(8–13), mediates diverse physiological effects, including antinociception. These effects are primarily driven by two G-protein-coupled receptors, NTS1 and NTS2. Importantly, NT-induced analgesia occurs independently of the opioid system, positioning the neurotensinergic pathway as a promising alternative for pain management in the context of the opioid crisis. However, clinical translation of NT-based analgesics has been hindered by their poor blood-brain barrier (BBB) permeability. To address this limitation, we implemented a structure-activity relationship (SAR) strategy aimed at enhancing brain delivery of NT(8-13). To this end, NT(8-13) was conjugated at its N-terminus to six distinct BBB transporter peptides using seven different linker chemistries, including ligands targeting the low-density lipoprotein receptor-related protein 1(LRP-1), which is highly expressed on BBB endothelial cells . Our findings demonstrate that N-terminal conjugation preserves high binding affinity for both NTS1 and NTS2 receptors, regardless of the transporter or linker employed. Moreover, subcutaneous injection of selected conjugates significantly reduced pain-related behaviors in adult male rats in the formalin-induced tonic pain model. Ongoing studies are focused on quantitatively assessing brain biodistribution and BBB penetration using ex vivo mass spectrometry imaging and in vivo PET-CT imaging to identify the most promising candidates. Together, these results provide a strong rationale for the development of brain-penetrant NT peptides as a safe and effective non-opioid approach for pain management.