Osanetant is a neurokinin (NK3) receptor antagonist under development by Sanofi-Synthélabo (formerly Sanofi) as a potential treatment for schizophrenia [328910]. Sanofi was originally investigating its potential use as a treatment for psychosis and anxiety [169511]. Following phase IIa clinical trials [307656], [328910], [359231], osanetant entered phase IIb development in February 2001 [409432]. Osanetant was the first potent and selective non-peptide antagonist described for the NK3 tachykinin receptor [176305]. It has a higher affinity for human and guinea pig NK3 receptors than for rat NK3 receptors [176305]. In October 1999, Lehman Brothers predicted that the probability of the product reaching the market was 10%, with a possible launch in 2003 and potential peak sales of US $200 million in 2011 [346267].