AM-4668, a GPR40 (FFA1) agonist with oral availability, was optimized to reduce central nervous system (CNS) permeability, with a mouse brain/plasma ratio of only 0.02, and significantly reduced blood glucose levels in human GPR40 knock-in mice.

GPR40 (aequorin assay):2.6 nM (EC50), Insulin secretion (islets from GPR40 knock-in mice):55  nM (EC₅₀), GPR40 (IP₃ accumulation assay):8.4  nM (EC₅₀)

The in vitro activity of AM-4668 was evaluated in CHO and A9 cells stably expressing human GPR40, showing potent agonist activity with EC₅₀ values of 2.6 nM (aequorin assay) and 8.4 nM (IP₃ accumulation assay). In islets isolated from human GPR40 knock-in mice, AM-4668 stimulated insulin secretion with an EC₅₀ of 55 nM. AM-4668 also showed minimal toxicity in CYP inhibition and hERG channel assays and exhibited low CNS penetration (brain-to-plasma ratio of 0.02 at 3 h after oral dosing at 5 mg/kg in rats)[1].

The in vivo activity of AM-4668 was tested in human GPR40 knock-in mice. Mice were fasted for 6 hours and orally administered AM-4668 (10 mg/kg); one hour later, they underwent an oral glucose tolerance test (2 g/kg). AM-4668 reduced the glucose area under the curve (AUC) by 19% compared to vehicle controls. The compound also exhibited favorable pharmacokinetics in rats, dogs, and cynomolgus monkeys, with low clearance (0.04–0.15 L/h/kg), moderate to long half-life (5.3–14 h), and good oral bioavailability (65–100%) [1].