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

The combination therapy of lumacaftor and ivacaftor (Orkambi) is approved for patients bearing the major cystic fibrosis (CF) mutation: 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  and biochemical studies confirmed that this mutation could be corrected and potentiated by lumacaftor and ivacaftor, respectively, this combination led to a minor 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.