Orkambi® and amplifier co-therapy improves function from a rare CFTR mutation in gene-edited cells and patient tissue

The combination therapy of lumacaftor and ivacaftor (Orkambi (R)) is approved for patients bearing the major cystic fibrosis (CF) mutation: DF508. It has been predicted that Orkambi (R) 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 DF508-CFTR, are unlikely to yield a robust Orkambi (R) response. While in silico and biochemical studies confirmed that this mutation could be corrected and potentiated by lumacaftor and ivacaftor, respectively, this combination led to a minor in vitro 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 (R) response. Importantly, this amplifier effect was recapitulated in patient-derived nasal culturesproviding the first evidence for its efficacy in augmenting Orkambi (R) 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.