CFTR and cystic fibrosis: In a heterologous expression system where Q1291H (c.3873G>C cDNA, i.e., isoform 2) was expressed in CF bronchial epithelial cells (CFBEs) lacking endogenous CFTR expression (CFBE41o-), CFTR-specific current measured at 80% of wild-type (WT) CFTR, which was increased by IVA (1.9-fold), LUM (1.4-fold), and LUM/IVA (2.2-fold) (Joynt et al., 2020).