The rescue of F508del-CFTR by elexacaftor/tezacaftor/ivacaftor (Trikafta) in human airway epithelial cells is underestimated due to the presence of ivacaftor

Abstract

Trikafta, currently the leading therapeutic in Cystic Fibrosis (CF), has demonstrated a real clinical benefit. This treatment is the triple combination therapy of two folding correctors elexacaftor/tezacaftor (VX445/VX661) plus the gating potentiator ivacaftor (VX770). In this study, our aim was to compare the properties of F508del-CFTR in cells treated with either lumacaftor (VX809), tezacaftor, elexacaftor, elexacaftor/tezacaftor with or without ivacaftor. We studied F508del-CFTR function, maturation and membrane localisation by Ussing chamber and whole-cell patch clamp recordings, Western blot and immunolocalization experiments. With human primary airway epithelial cells and the cell lines CFBE and BHK expressing F508del, we found that, whereas the combination elexacaftor/tezacaftor/ivacaftor was efficient in rescuing F508del-CFTR abnormal maturation, apical membrane location and function, the presence of ivacaftor limits these effects. The basal F508del-CFTR short-circuit current was significantly increased by elexacaftor/tezacaftor/ivacaftor and elexacaftor/tezacaftor compared to other correctors and non-treated cells, an effect dependent on ivacaftor and cAMP. These results suggest that the level of the basal F508del-CFTR current might be a marker for correction efficacy in CF cells. When cells were treated with ivacaftor combined to any correctors, the F508del-CFTR current was unresponsive to the subsequently acute addition of ivacaftor unlike the CFTR potentiators genistein and Cact-A1 which increased elexacaftor/tezacaftor/ivacaftor and elexacaftor/tezacaftor-corrected F508del-CFTR currents. These findings show that ivacaftor reduces the correction efficacy of Trikafta. Thus, combining elexacaftor/tezacaftor with a different potentiator might improve the therapeutic efficacy for treating CF patients.

The L467F-F508del Complex Allele Hampers Pharmacological Rescue of Mutant CFTR by Elexacaftor/Tezacaftor/Ivacaftor in Cystic Fibrosis Patients: The Value of the Ex Vivo Nasal Epithelial Model to Address Non-Responders to CFTR-Modulating Drugs

“…It has been proposed that this is due to a destabilization of the protein, increasing its turnover rate [ 26 , 27 ]. This effect has been demonstrated following rescue by lumacaftor [ 26 , 27 ] and, more recently, also by Elexa/Teza combination [ 28 ]. We thus postulated that the detrimental effect of ivacaftor could be particularly strong in the TT001 patient.…”

Targeting the E1 ubiquitin-activating enzyme (UBA1) improves elexacaftor/tezacaftor/ivacaftor efficacy towards F508del and rare misfolded CFTR mutants

“…The importance of this new therapy should be ascribed not only to the very promising pre-clinical and clinical results but also to its wide coverage, as this treatment can be administered in patients with at least one F508del allele (70–90% of the cystic fibrosis population according to specific geographic distribution) [ 4 ]. However, a further improvement in F508del-CFTR rescue is still possible [ 5 , 6 ]. Moreover, the therapeutic response varies between individuals and there is a significant group of CF patients in whom the response to the treatment is worse, and a minority that are forced to discontinue the therapy due to the side effects [ 7 ].…”

Measurements of spontaneous CFTR-mediated ion transport without acute channel activation in airway epithelial cultures after modulator exposure

“…The effects of exposure to TRIKAFTA ® (VX-445/VX-661/VX-770) or components thereof in F508del CFTR-expressing cells have previously been described 14 – 19 , including the demonstration of an increase in spontaneous CFTR activity as estimated in Fig. 1 e as well as an increase in post-amiloride basal currents 14 , 16 , 17 , 19 . In the present study, VX-445/VX-661/VX-770 treatment resulted in much greater increases in the spontaneous CFTR activity present in these epithelia and, in addition, significantly reduced the baseline V te , increased baseline G te (Fig.…”

“…When CFTR-activating compounds are employed, the response to subsequent inhibition of CFTR provides a measure of the maximum functional capacity of CFTR in the epithelia (i.e., response to CFTR activation + spontaneous CFTR activity = response to CFTR inhibition after activation = maximum functional capacity of CFTR). Estimation of spontaneous CFTR activity may be made by calculating the difference between electrical parameters before CFTR activation and after stabilization following CFTR inhibition 14 , 17 , although significant differences between changes obtained through this method and the analysis of spontaneous CFTR activity using CFTR(inh)-172 responses in the absence of F/I were observed (Figs. 1 e and S1 c).…”