ABSTRACT
A high throughput screening campaign identified 5-(2-chlorophenyl)indazole compound 4 as an antagonist of the transient receptor potential A1 (TRPA1) ion channel with IC50 = 1.23 µM. Hit to lead medicinal chemistry optimization established the SAR around the indazole ring system, demonstrating that a trifluoromethyl group at the 2-position of the phenyl ring in combination with various substituents at the 6-position of the indazole ring greatly contributed to improvements in vitro activity. Further lead optimization resulted in the identification of compound 31, a potent and selective antagonist of TRPA1 in vitro (IC50 = 0.015 µM), which has moderate oral bioavailability in rodents and demonstrates robust activity in vivo in several rodent models of inflammatory pain.
Subject(s)
Indazoles/chemistry , Nerve Tissue Proteins/antagonists & inhibitors , Transient Receptor Potential Channels/antagonists & inhibitors , Administration, Oral , Analgesics/chemistry , Analgesics/pharmacokinetics , Analgesics/pharmacology , Animals , Anti-Inflammatory Agents/chemistry , Anti-Inflammatory Agents/pharmacokinetics , Anti-Inflammatory Agents/pharmacology , Biological Availability , CHO Cells , Calcium Channels , Cricetulus , Freund's Adjuvant , Humans , Hyperalgesia/chemically induced , Hyperalgesia/drug therapy , Indazoles/pharmacokinetics , Indazoles/pharmacology , Male , Mice, Inbred C57BL , Mustard Plant , Plant Oils , Rats, Wistar , Species Specificity , Structure-Activity Relationship , TRPA1 Cation Channel , TRPC Cation Channels/antagonists & inhibitorsABSTRACT
We report the identification of a novel series of human epithelial sodium channel (ENaC) blockers that are structurally distinct from the pyrazinoyl guanidine chemotype found in prototypical ENaC blockers such as amiloride. Following a rational design hypothesis a series of quaternary amines were prepared and evaluated for their ability to block ion transport via ENaC in human bronchial epithelial cells (HBECs). Compound 11 has an IC(50) of 200nM and is efficacious in the Guinea-pig tracheal potential difference (TPD) model of ENaC blockade with an ED(50) of 44µgkg(-1) at 1h. As such, pyrazinoyl quaternary amines represent the first examples of a promising new class of human ENaC blockers.