An example of a drug in this class is aprepitant. Chemotherapy-induced emesis appears to consist of acute and delayed phases. So far, the acute phase emesis responds to 5-HT3 antagonists while the delayed phase remains difficult to control. The discovery and development of NK1 receptor antagonists have elicited antiemetic effect in both acute and especially in delayed phases of emesis. Casopitant, netupitant and rolapitant are some newer additions in this group. Rolapitant has a significantly longer half-life of 160 hours and was approved by the US FDA in 2015.