Casopitant (INN,:208 tentative trade names Rezonic (U.S.), Zunrisa (Europe)) is a neurokinin 1 receptor (NK1R) antagonist undergoing research for the treatment of chemotherapy-induced nausea and vomiting (CINV). It is currently under development by GlaxoSmithKline (GSK). Casopitant (INN,:208 tentative trade names Rezonic (U.S.), Zunrisa (Europe)) is a neurokinin 1 receptor (NK1R) antagonist undergoing research for the treatment of chemotherapy-induced nausea and vomiting (CINV). It is currently under development by GlaxoSmithKline (GSK). In July 2008, the company filed a marketing authorisation application with the European Medicines Agency. The application was withdrawn in September 2009 because GSK decided that further safety assessment was necessary.