PNU-142633 is a high affinity, selective and orally active 5-HT_1D receptor agonist with K_is of 6 nM and > 18 000 nM for human 5-HT_1D receptor and human 5-HT_1B receptor, respectively. PNU-142633 has anti-migraine efficacy^[1][2]. In Vitro: The intrinsic activity of PNU-142633 at the human 5-HT1D receptor is determined to be 70% that of 5-HT in a cytosensor cell-based assay compared with 84% for that of Sumatriptan^[1]. In Vivo: PNU-142633 (0.03-1 mg/kg; intravenous injection; male Hartley guinea pigs) treatment blocks neurogenic plasma protein extravasation. And PNU-142633 fails to alter resistance in these vascular beds^[1].