Sarizotan (also known as EMD-128,130), a chromane derivative that was developed as a selective 5-HT1A receptor agonist and D2 receptor antagonist. Experiments on animal models have shown that the drug effectively suppressed levodopa-induced dyskinesia in primate and rodent models of Parkinson's disease, and tardive dyskinesia in a rodent model. Sarizotan participated in phase II/III clinical trials in the treatment of dyskinesia associated with the dopaminergic treatment of Parkinson's disease. However, further development for this disease was discontinued by Merk, because phase III did not confirm earlier Phase II findings. On July 14, 2015, Newron Pharmaceuticals, research, and development company focused on the novel central nervous system (CNS) and pain therapies, announced that the U.S. Food and Drug Administration (FDA) has granted Orphan Drug Designation to sarizotan for treatment of Rett syndrome. Besides, the drug now is an ongoing clinical trial phase II/III to investigate its the tolerability and efficacy in reducing respiratory abnormalities in Rett Syndrome.