&NA;MK 869 (L 754030, MK 0869) is a substance P antagonist selective for neurokinin NK1receptors that is undergoing phase II clinical trials with Merck & Co. in the US as a potential treatment for acute and delayed chemotherapy-induced emesis. Phase II trials for anxiety and schizophrenia are also in progress. The drug was in development as an antidepressant but studies in this indication were suspended in early 1999 as a result of an inconclusive phase II dose-finding study.