A functional comparison of vanzacaftor/tezacaftor/deutivacaftor and elexacaftor/tezacaftor/ivacaftor in patient-derived intestinal organoids with rare CFTR variants

BACKGROUND: Cystic fibrosis (CF) results from pathogenic CFTR variants that impair epithelial chloride and bicarbonate transport. CFTR modulators such as elexacaftor/tezacaftor/ivacaftor (ETI) have transformed CF care, and the next-generation regimen vanzacaftor/tezacaftor/deutivacaftor (VTD) has recently been introduced on the market. VTD offers once-daily dosing and expanded regulatory approval, yet its functional advantages remain not fully characterized across a broad set of genotypes. Consequently, we set out to compare CFTR functional rescue of ETI and VTD in primary patient-derived intestinal organoids (PDIOs) harbouring a broad range of CFTR variants. METHODS: We evaluated ETI and VTD efficacy in 62 PDIO lines representing 42 rare CFTR genotypes and reference groups (p.Phe508del/p.Phe508del, p.Phe508del/class I, class I/class I). CFTR rescue was assessed by CFTR function by steady-state lumen area quantification and forskolin-induced swelling assays and CFTR maturation via western blot. RESULTS: Across rare variants, CFTR functional rescue by ETI and VTD strongly correlated, with modest but consistent VTD advantages in a subset of folding-defective genotypes (e.g., p.Val520Phe). Three PDIOs showed disproportionately high responses to VTD. VTD increased CFTR maturation more effectively than ETI, yet demonstrated similar acute effects on CFTR function. CONCLUSIONS: VTD provides modest genotype-specific functional advantages and enhanced CFTR maturation but is largely comparable to ETI across rare variants. PDIO-based screenings performed in this study underline again their potential for theratyping, which is particularly critical for guiding decisions on accessibility for rare variants in an era with a variety of modulators, and combinations thereof.