Discovery, asymmetric synthesis and biological evaluation of new bisbenzylisoquinoline-orexin receptor antagonists for insomnia treatment

The development of new orexin receptor (OXR) antagonists represents a crucial avenue for addressing the urgent need for safe and effective anti-insomnia drugs in clinical practice. Our group discovered neferine, a bisbenzylisoquinoline alkaloid isolated from Nelumbinis Plumula, exhibited a predicted binding affinity for OXR through virtual screening. Herein, we report the asymmetric synthesis of neferine and its isomers using a novel CuBr•Me₂S/picolinic acid-catalyzed arylation method. Biological assay results indicated that (R,S)-neferine demonstrated superior OXR antagonistic activity than suvorexant, with good binding affinities of KD (OX₁R) 0.68 and (OX₂R) 0.81 nM. In vivo pharmacodynamic studies showed that (R,S)-neferine reduced spontaneous activities in mice more effectively than daridorexant and significantly improved sleep in insomnia mice. Furthermore, (R,S)-neferine can restore the significant downregulation of PER1 and PER2, along with the upregulation of BMAL1 caused by insomnia, and decrease the expression of OX₁R and OX₂R, thereby improving core circadian rhythm disorders. (R,S)-neferine carried outstanding pharmacokinetic (F = 63.7 %) and safety profiles (LD50 > 500 mg/kg), no mortality or histopathological changes were observed during the acute toxicity test. Overall, this work highlights the therapeutic potential of the OXR antagonist (R,S)-neferine, providing candidates and viable drug development strategies for the treatment of insomnia.