Iloperidone (HP-873) is a 5-HT2 antagonist from Hoechst Marion Roussel Inc in clinical trials for the treatment of schizophrenia and psychosis. In May 1996, the company announced that it had discontinued further development of the compound. This announcement, however, was followed in January 1997 by the news that Hoechst had licensed the compound to Titan Pharmaceuticals, on a worldwide exclusive basis. Subsequently, Titan granted Novartis worldwide development, manufacturing and marketing rights, excluding Japan. In August 1998, Novartis commenced phase III trials for iloperidone to treat schizophrenia. The trial will include 3000 patients in 20 countries. In receptor binding assays it has moderate affinity for the D2 receptor and greater affinity for the 5-HT2 receptor. This is thought to be an important factor for atypical antipsychotic activity and reduction of extrapyramidal side-effects.