WS06.3 Evaluation of novel corrector–potentiator combinations for treating cystic fibrosis in various assays

Defects in CFTR that result in cystic fibrosis can be broadly categorized into three processes: translational, folding/maturation, and functional. To address the underlying causes affecting the folding/maturation and functional properties of CFTR, two biomolecular activities are required, namely correctors to increase CFTR levels at the cell surface, and potentiators to allow the effective opening of the CFTR channel. Combined, these activities allow chloride ion transport yielding improved hydration of the lung surface and subsequent restoration of mucociliary clearance. Previously, we reported the discovery of new corrector molecules via a HTS screen on CFBe41o-cells harboring HRP-tagged F508del CFTR and on U2OS cells ProLink-tagged F508del CFTR (NACFC 2014). Corrector compounds from two distinct series exhibited channel opening activity in primary cells derived from F508del CFTR homozygous patients as measured by trans-epithelial clamp circuit (TECC). Here, we report a series of assays developed to better understand the mechanism of action of the corrector molecules. More specifically, assays using differently tagged F508del CFTR were employed to evaluate the effect of correctors alone and in various combinations with a potentiator on the correction time-dependency and on the cell surface residence time of F508del CFTR. Other characterization endpoints will also be discussed. In summary, we developed several assays to evaluate the impact of corrector/potentiator combinations on the rescue of F508del CFTR, and to understand the contribution of each component in combination cocktails.