Discovery of a Novel Series of Orally Active Nociceptin/Orphanin FQ (NOP) Receptor Antagonists Based on a Dihydrospiro(piperidine-4,7′-thieno[2,3‑c]pyran) Scaffold

Nociceptin/OFQ (N/OFQ) is a 17 amino acid peptide that is the endogenous ligand for the ORL1/NOP receptor. Nociceptin appears to regulate a host of physiological functions such as biological reactions to stress, anxiety, mood, and drug abuse, in addition to feeding behaviors. To develop tools to study the function of nociceptin and NOP receptor, our research effort sought to identify orally available NOP antagonists. Our effort led to the discovery of a novel chemical series based on the dihydrospiro(piperidine-4,7′-thieno[2,3-c]pyran) scaffold. Herein we show that dihydrospiro(piperidine-4,7′-thieno[2,3-c]pyran)-derived compounds are potent NOP antagonists with high selectivity versus classical opioid receptors (μ, δ, and κ). Moreover, these compounds exhibit sufficient bioavailability to produce a high level of NOP receptor occupancy in the brain following oral administration in rats.