GR 103691 is a potent, selective dopamine D3 receptor antagonist with a Ki value of 0.4 nM. GR 103691 shows more than 100-fold selectivity for human dopamine human (h)D3 over hD4 and hD1 sites[1].
GR 103691 shows marked affinity for serotonin1A (5-HT1A) receptors (Ki of 5.8 nM) and α-1 adrenoceptors (Ki of 12.6 nM)[1].
[1]. Audinot V, et al. A comparative in vitro and in vivo pharmacological characterization of the novel dopamine D3 receptor antagonists (+)-S 14297, nafadotride, GR 103,691 and U 99194. J Pharmacol Exp Ther. 1998 Oct;287(1):187-97.