PF-6870961 hydrochloride is an inverse agonist of GHSR1a with K i values of 73.6 nM (human GHSR ), 239 nM (rat GHSR ), and 217 nM (dog GHSR ), respectively. PF-6870961 hydrochloride inhibits the constitutive GHSR1a-induced IP accumulation with an IC 50 value of 300 nM. PF-6870961 hydrochloride also inhibits constitutive GHSR1a β-arrestin mobilization with an IC 50 value of 1.10 nM.