&NA;MCI 225 is a thienopyrimidine analogue currently undergoing phase II clinical trials with Mitsubishi Chemical in Japan as an antidepressant. The mechanism of action of MCI 225 appears to involve inhibition of noradrenaline (norepinephrine) reuptake and turnover combined with antagonism at serotonin 5-HT3 receptors, which may contribute to its antidepressant effect and reduce its anticholinergic action. The compound has exhibited antidepressant activity at least as potent as tricyclic antidepressants in animal models. Mitsubishi Chemical has announced that itwill collaboratewith Taisho Pharmaceutical on phase III clinical testing of this compound in early 2000. In doing so, Mitsubishi Chemical hopes to accelerate development of MCI 225, and Taisho is looking to fortify its CNS drug operations.