Discovery of naldemedine: A potent and orally available opioid receptor antagonist for treatment of opioid-induced adverse effects.

Structure-activity relationship studies of several morphinan derivatives were conducted to obtain dual antagonists for μ- and δ-opioid receptors. We discovered peripherally restricted dual antagonists for μ/δ-opioid receptors as a new chemotype with a morphinan scaffold, which are orally available and do not easily pass the blood-brain barrier. As we expected, some of these compounds inhibit opioid-induced constipation and emesis/vomiting with limited potential to interfere the analgesic effects of morphine. Among them, naldemedine was selected as a potential drug candidate.