Likewise employing the primary endpoint of “reduction of L-Dopa induced dyskinesia”, the results of clinical phase III trials with the metabotropic-glutamate-receptor-5-antagonist (mavoglurant)45–48 and the nicotine-alpha-7-partial agonist AQW05149 were negative and thus their development stopped, whereas the clinical testing of glutamate-receptor-4-antagonists and allosteric modulators of the metabotropic-glutamate-receptor-5—employing the same endpoint (reduction of dyskinesia)—are ongoing. Here, GRIA4 is linked to drug-induced dyskinesia.