Discovery of DS-1971a, a Potent, Selective Na1.7 Inhibitor.

A highly potent, selective Na1.7 inhibitor, DS-1971a, has been discovered. Exploration of the left-hand phenyl ring of sulfonamide derivatives ( and ) led to the discovery of novel series of cycloalkane derivatives with high Na1.7 inhibitory potency in vitro. As the right-hand heteroaromatic ring affected the mechanism-based inhibition liability of CYP3A4, replacement of this moiety resulted in the generation of 4-pyrimidyl derivatives. Additionally, GSH adducts formation, which can cause idiosyncratic drug toxicity, was successfully avoided by this modification. An additional optimization led to the discovery of DS-1971a. In preclinical studies, DS-1971a demonstrated highly potent selective in vitro profile with robust efficacy in vivo. DS-1971a exhibited a favorable toxicological profile, which enabled multiple-dose studies of up to 600 mg bid or 400 mg tid (1200 mg/day) administered for 14 days to healthy human males. DS-1971a is expected to exert potent efficacy in patients with peripheral neuropathic pain, with a favorable safety profile.