Telcagepant (INN) (code name MK-0974) is a calcitonin gene-related peptide receptor antagonist which was an investigational drug for the acute treatment and prevention of migraine, developed by Merck & Co.[1] In the acute treatment of migraine, it was found to have equal efficacy to rizatriptan[2] and zolmitriptan.

[3] A Phase IIa clinical trial studying telcagepant for the prophylaxis of episodic migraine was stopped on March 26, 2009, after the "identification of two patients with significant elevations in serum transaminases".

[4] A memo to study locations stated that telcagepant had preliminarily been reported to increase the hepatic liver enzyme alanine transaminase (ALT) levels in "11 out of 660 randomized (double-blinded) study participants."

All study participants were told to stop taking the medication.

[5] In July 2011, Merck announced that it had discontinued development of telcagepant.