ARL67156 trisodium salt is an inhibitor of ecto-ATPase. ARL 67156 is a weak competitive inhibitor of NTPDase1 (CD39), NTPDase3 and NPP1, with K_is of 11, 18 and 12 μM, respectively^[1]. IC50 & Target: Ki: 11 μM (NTPDase1), 18 μM (NTPDase3), 12 μM (NPP1)^[1] In Vitro: ARL67156 trisodium salt is also an effective inhibitor of UTP breakdown by superior cervical ganglion cells and to potentiate contractions elicited by this nucleotide in isolated tail artery of rat. ARL67156 is not an effective inhibitor of NTPDase2, NTPDase8, NPP3 and ecto-5′-nucleotidase (CD73), although it also reduces the activity of these enzymes^[1].