Fig. 1: Dose-dependent activation of wildtype CFTR in FRT cells by two HDCF analogs (HDCF104 and uHTS159).

Ussing chamber analysis of Fischer rat thyroid (FRT) cells shows stimulation of WT CFTR. a, b Escalating doses of HDCF104 demonstrate strong WT CFTR activity with EC50 = 101 μM (95% CI 91.7 μM to 112.3 μM) as judged by dose-dependence profile. In similar fashion, (c, d) uHTS159 displays robust enhancement of WT CFTR with EC50 = 14.4 μM (95% CI 12.5 μM−17.2 μM). Data is representative of 3 biological replicates and expressed as mean ± SD. Maximal stimulation of wildtype CFTR by saturating concentrations of forskolin in this model is 300−500 μA/cm2. Amiloride (100 µM) was added to block epithelial sodium channels; forskolin (5 µM) augments cellular cAMP and activates CFTR by PKA-dependent phosphorylation of the regulatory domain; inh-172 (10 µM) is a CFTR inhibitor. e Structures of the compounds. Statistics were by use of GraphPad Prism 10 software with the function of Sigmoidal, 4PL, with X as concentration. “HDCF” denotes the medicinal chemistry laboratory in which new compounds were synthesized (directed by Dr. Huw Davies). Panels (a, c) plotted with Microsoft Excel; (b, d) plotted (and compound EC50 calculated) using GraphPad Prism 10 software; Panel (e) created with ChemDraw; panels arranged and presented using Affinity Designer software.