Peripheral GALR2 activation by the metabolically stabilized spexin analog LIT-01-144 produces potent opioid‑independent antinociception

Chronic pain constitutes a major global health burden, and current management remains largely dependent on opioid analgesics, which are associated with opioid use disorder. Accordingly, there is a pressing need to identify non-opioid therapeutic strategies. Galanin receptors (GALR1-3) have been implicated in pain modulation, but their individual roles remain insufficiently defined because of the absence of subtype-selective ligands. Recently, spexin has been identified as an endogenous peptide that selectively activates GALR2 and GALR3, offering a new scaffold for developing pharmacological tools targeting these receptor subtypes. In this study, we designed and characterized LIT-01-144, a modified spexin analog incorporating N-terminal fluorocarbon functionalization to improve metabolic stability while preserving receptor selectivity. In vitro pharmacological profiling demonstrated high potency at GALR2 and GALR3, with negligible activity at GALR1. Pharmacokinetic analyses showed a substantially prolonged plasma half-life relative to native spexin and no evidence of central nervous system penetration. In vivo, intracerebroventricular administration of LIT-01-144 produced robust antinociception at doses tenfold lower than those required for spexin. Although systemic administration had no detectable effect in naïve mice, it significantly attenuated pain-related behaviors in a model of persistent inflammatory pain. This effect was mediated specifically by GALR2 and was independent of opioid receptor signaling. In situ hybridization further showed an increase in Galr2 + neurons in dorsal root ganglia of inflamed mice. Collectively, these findings highlight GALR2 as a promising peripheral target for developing non-opioid analgesics and demonstrate the potential of LIT-01-144 as a valuable tool for understanding GALR2-mediated mechanisms of pain modulation.