Development and characterisation of novel oxytocin analogues for PET imaging

The oxytocin/oxytocin receptor (OT/OTR) signalling system is involved in socioemotional behaviours, garnering interest as a therapeutic target across multiple clinical conditions. Despite its potential, our limited understanding of how to optimally target it and the scarcity of molecular tools for in vivo studies hinder therapeutic development. Molecular imaging techniques, such as Positron Emission Tomography (PET), can bridge this gap by furnishing direct insights into ligand biodistribution, receptor visualisation and ligand-receptor engagement. Here, we report the design, synthesis and biochemical and pharmacological characterisation of five OT-like peptides as novel PET tracers for investigating the OT/OTR signalling system. dOTK⁸[SFB] emerged as the most promising OT-like lead. The radioactive version [¹⁸F]dOTK⁸[SFB] was produced using a microfluidic reaction approach and validated by preclinical PET imaging of healthy rats after intravenous ligand administration. [¹⁸F]dOTK⁸[SFB] exhibited specific accumulation in OTR-rich tissues, affirming OTR-specificity and suitability as a new OT-like PET radiotracer for investigating OT/OTR biodistribution in humans.