– MK-3207 is a potent and orally bioavailable CGRP receptor antagonist (IC 50 = 0.12 nM; K i = 0.024 nM); highly selective versus human AM1, AM2, CTR, and AMY3. IC50 Value: 0.024 nM (Ki, Human CGRP) [1] As other CGRP receptor antagonists, MK-3207 shows a lower affinity for human CGRP receptors from other species, including canine and rodent. in vitro: MK-3207 is a potent antagonist of the human and rhesus monkey CGRP receptors (K(i) = 0.024 nM). in vivo: MK-3207 produced a concentration-dependent inhibition of dermal vasodilation, with plasma concentrations of 0.8 and 7 nM required to block 50 and 90% of the blood flow increase, respectively. The tritiated analog [3H]MK-3207 was used to study the binding characteristics on the human CGRP receptor. [3H]MK-3207 displayed reversible and saturable binding (K(D) = 0.06 nM), and the off-rate was determined to be 0.012 min(-1), with a t(1/2) value of 59 min [1]. After the first interim analysis, the two lowest MK-3207 doses (2.5, 5 mg) were identified as showing insufficient efficacy. Per the pre-specified adaptive design decision rule, only the 2.5-mg group was discontinued and the five highest doses (5, 10, 20, 50, 100 mg) were continued into the second stage [2]. Clinical trial: MK-3207 for the treatment of acute migraines. Phase 2b