Substituted 2‑Acylamino­cycloalkyl­thiophene-3-carboxylic Acid Arylamides as Inhibitors of the Calcium-Activated Chloride Channel Transmembrane Protein 16A (TMEM16A)

Transmembrane
protein 16A (TMEM16A), also called anoctamin 1 (ANO1),
is a calcium-activated chloride channel expressed widely mammalian
cells, including epithelia, vascular smooth muscle tissue, electrically
excitable cells, and some tumors. TMEM16A inhibitors have been proposed
for treatment of disorders of epithelial fluid and mucus secretion,
hypertension, asthma, and possibly cancer. Herein we report, by screening,
the discovery of 2-acylamino­cycloalkyl­thiophene-3-carboxylic
acid arylamides (AACTs) as inhibitors of TMEM16A and analysis of 48
synthesized analogs (10ab–10bw) of
the original AACT compound (10aa). Structure–activity
studies indicated the importance of benzene substituted as 2- or 4-methyl,
or 4-fluoro, and defined the significance of thiophene substituents
and size of the cycloalkylthiophene core. The most potent compound
(10bm), which contains an unusual bromodifluoro­acetamide
at the thiophene 2-position, had IC50 of ∼30 nM,
∼3.6-fold more potent than the most potent previously reported
TMEM16A inhibitor 4 (Ani9), and >10-fold improved
metabolic
stability. Direct and reversible inhibition of TMEM16A by 10bm was demonstrated by patch-clamp analysis. AACTs may be useful as
pharmacological tools to study TMEM16A function and as potential drug
development candidates.