<scp>O</scp> rkambi® and amplifier co‐therapy improves function from a rare <i> <scp>CFTR</scp> </i> mutation in gene‐edited cells and patient tissue

Abstract

The combination therapy of lumacaftor and ivacaftor (Orkambi^®) is approved for patients bearing the major cystic fibrosis (CF) mutation: <i>ΔF508</i> It has been predicted that Orkambi^® could treat patients with rarer mutations of similar "theratype"; however, a standardized approach confirming efficacy in these cohorts has not been reported. Here, we demonstrate that patients bearing the rare mutation: c.3700 A>G, causing protein misprocessing and altered channel function-similar to ΔF508-CFTR, are unlikely to yield a robust Orkambi^® response. While <i>in silico</i> and biochemical studies confirmed that this mutation could be corrected and potentiated by lumacaftor and ivacaftor, respectively, this combination led to a minor <i>in vitro</i> response in patient-derived tissue. A CRISPR/Cas9-edited bronchial epithelial cell line bearing this mutation enabled studies showing that an "amplifier" compound, effective in increasing the levels of immature CFTR protein, augmented the Orkambi^® response. Importantly, this "amplifier" effect was recapitulated in patient-derived nasal cultures-providing the first evidence for its efficacy in augmenting Orkambi^® in tissues harboring a rare CF-causing mutation. We propose that this multi-disciplinary approach, including creation of CRISPR/Cas9-edited cells to profile modulators together with validation using primary tissue, will facilitate therapy development for patients with rare CF mutations.