Discovery of MK-5661, a Once-Daily Oral Na V 1.8 Inhibitor for the Treatment of Pain

NaV1.8 is a key mediator of peripheral nociceptive signaling and an attractive nonopioid target for pain therapeutics. We report the discovery of MK 5661, a potent, selective, and orally bioavailable NaV1.8 inhibitor amenable to once-daily dosing. Optimization of an initial lead, guided by reduction of PXR activation, and dose optimization focusing on half-life and volume ligand efficiency are described. MK-5661 demonstrates a favorable pharmacokinetic profile in preclinical species, as well as efficacy in preclinical models for pain.