Sergolexole [LY 281067] is an ergoline ester similar in structure to amesergide [LY 237733], with potent and highly selective antagonist activity at serotonin 2. The preclinical pharmacologic activity of LY 281067 shows it to be a potent and highly selective serotonergic (5-HT2) receptor antagonist. Based upon binding studies with 5-HT2 receptors in brain cortical membranes and block of 5-HT-induced contractions in the rat jugular vein, LY 281067 showed high affinity at 5-HT2 receptors with a dissociation constant of approximately 1 nM. LY 281067 was a highly selective 5-HT2 receptor antagonist without appreciably binding to 5-HT1, D1 or D2 receptors or interacting with histamine (H1), cholinergic, beta adrenergic or alpha-1 adrenergic receptors in smooth muscle. LY 281067 had modest affinity at alpha-2 receptors with a dissociation constant of approximately 100 nM. Oral bioavailability of LY 281067 in spontaneously hypertensive rats was excellent with an oral to i.v. dose ratio approximating 4. Sergolexole was undergoing phase II clinical trials with Eli Lilly in the USA as a potential treatment for migraine and anxiety, but development of this compound, but development of this compound has been discontinued.