Novel CFTR modulator combinations maximise rescue of G85E and N1303K in rectal organoids.

Introduction: Cystic fibrosis (CF) is a severe monogenic disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator ( CFTR ) gene. Several types of CFTR modulators (correctors/potentiators) have been developed to overcome protein dysfunction associated with these mutations. CFTR modulator therapy is now available for the major CF-causing mutations; however, 10% of people with CF remain without causal treatments. By combining investigational and market-approved CFTR modulators, we aimed to maximise functional rescue of iva-, luma- and tezacaftor refractory mutants G85E and N1303K.
Methods: We used the well-established forskolin-induced swelling (FIS) in primary rectal organoids to assess responses to different CFTR corrector and potentiator types. The FIS analysis was performed with brightfield microscopy, allowing both 1-h and 24-h follow-up. Corrector and potentiator activity of elexacaftor was investigated.
Results: For G85E, maximal rescue was observed by a combination of elexacaftor and corr4a. For N1303K, the quadruple combination teza-elexa-ivacaftor with apigenin was required to obtain a rescue similar to that of luma-ivacaftor rescued F508del. Elexacaftor rescued G85E and N1303K by different mechanisms, with chronic corrector effects on G85E and acute potentiation of N1303K only in the presence of ivacaftor. Synergy in N1303K rescue for iva-elexacaftor and apigenin suggests at least three potentiator mechanisms for this mutant. 24-h FIS identified ivacaftor as the main CFTR modulator for N1303K and elexacaftor and apigenin as co-potentiators.
Conclusions: Novel combinations of CFTR modulators can further improve functional rescue of G85E and N1303K in rectal organoids, although for N1303K, more effective CFTR modulators are still needed.
Competing Interests: Conflict of interest: M.M. Ensinck has nothing to disclose. Conflict of interest: L. De Keersmaecker has nothing to disclose. Conflict of interest: A.S. Ramalho has nothing to disclose. Conflict of interest: S. Cuyx reports receiving research grants (funds paid to institution) from Belgische Vereniging Kindergeneeskunde, Mucovereniging/Association Muco and Fonds Forton, outside the submitted work. Conflict of interest: S. Van Biervliet has nothing to disclose. Conflict of interest: L. Dupont has nothing to disclose. Conflict of interest: F. Christ reports receiving grants or contracts (funds paid to institution) from FWO Flanders (SBO: S001221N) outside the submitted work. Conflict of interest: Z. Debyser reports receiving grants or contracts (funds paid to institution) from FWO Flanders (SBO: S001221N) outside the submitted work. Conflict of interest: F. Vermeulen reports receiving grants or contracts (funds paid to institution) from the HIT-CF consortium, Vertex Pharmaceuticals, Fonds Wetenschappelijk Onderzoek, Association Muco and the Cystic Fibrosis Foundation; and participation on a data safety monitoring or advisory board for Vertex Pharmaceuticals. All disclosures made outside the submitted work. Conflict of interest: M.S. Carlon reports receiving grants or contracts (funds paid to institution) from Koning Boudewijnstichting and the Belgian CF patient association (2017-J1810150-207746), and FWO Flanders (SBO: S001221N), outside the submitted work.
(Copyright ©The authors 2022.)