N-terminal amine identified as key to NTS2-mediated spinal pain relief in macrocyclic neurotensin analogs
- A set of macrocyclic neurotensin analogs combining earlier favorable substitutions kept strong NTS2 binding and very high selectivity over NTS1, although the combined changes did not act additively.
- Two lead analogs produced spinal pain relief in rat tail-flick and formalin assays.
- Deleting the N-terminal amine preserved receptor binding but eliminated analgesia, and simulations showed altered extracellular loop contacts and dynamics, offering a design framework for non-opioid analgesics.
💡 Points
Binding retained, analgesia gone: deleting the N-terminal amine decouples affinity from function, so Ki alone will mislead your SAR here. That amine likely anchors an extracellular-loop contact needed for the active state, so treat it as untouchable in the pharmacophore. The non-additive combinations also warn that stacking 'good' substitutions in a macrocycle needs re-validation, not assumption.
Chemical Determinants of Spinal Analgesia in NTS2-Selective Macrocycles ↗