ECFS Clinical Meeting Liverpool TMEM16A potentiator
Objectives: TMEM16A (ANO1) is a Ca2+-activated, alternative chloride channel expressed in the human airway epithelium. A potentiator of TMEM16A is predicted to enhance the secretion of chloride and thereby increase mucus hydration and clearance in the CF lung. Our aim is to discover and test the efficacy of novel TMEM16A potentiator compounds as a new therapeutic option for the treatment of CF lung disease.
Methods: Four, parallel high-throughput screening approaches were used to identify novel TMEM16A potentiator compounds. Compounds were then optimised and tested in primary CF bronchial epithelial cells for effects on both ion transport and airway surface liquid secretion.
Results: Several classes of TMEM16A potentiators were identified from the high-throughput screens. Only compound series that potentiated TMEM16A activity in a patch-clamp electrophysiology assay and which had no effect on intra-cellular Ca2+, were progressed for lead optimization. Pre-treatment of CF-HBE with TMEM16A potentiators for between 5 min to 96h resulted in an enhancement of Ca2+-mediated anion-secretory responses that were sensitive to the TMEM16A blocker, Ani9. Measurements of [Ca2+]i confirmed that TMEM16A potentiators had no effect on calcium mobilization, consistent with a direct effect on the channel. A Series 1 TMEM16A potentiator, ETX001, increased the secretion of airway surface liquid (ASL) in CF-HBE. The ETX001-driven increase in ASL height was further enhanced in cells that had been pre-treated with IL-13 to boost TMEM16A expression. A close structural analogue of ETX001, ETX002, that is inactive on TMEM16A, did not increase ASL height.
Conclusions: Together, these data support the concept that potentiators of the alternative airway chloride conductance, TMEM16A, can restore anion conductance and fluid secretion in both primary CF cells. Enterprise Therapeutics are advancing TMEM16A potentiators into clinical development.