RAAV-CFTRDR rescues the cystic fibrosis phenotype in human intestinal organoids and cystic fibrosis mice

Rationale: Gene therapy holds promise for a curative mutationindependent treatment applicable to all patients with cystic fibrosis (CF). The various viral vector-based clinical trials conducted in the past have demonstrated safety and tolerance of different vectors, but none have led to a clear and persistent clinical benefit. Recent clinical breakthroughs in recombinant adeno-associated viral vector (rAAV)-based gene therapy encouraged us to reexplore an rAAV approach for CF.
Objectives: We evaluated the preclinical potential of rAAV gene therapy for CF to restore chloride and fluid secretion in two complementary models: intestinal organoids derived from subjects with CF and a CF mouse model, an important milestone toward the development of a clinical rAAV candidate for CF gene therapy.
Methods: We engineered an rAAV vector containing a truncated CF transmembrane conductance regulator (CFTRDR) combined with a short promoter (CMV173) to ensure optimal gene expression. A rescue in chloride and fluid secretion after rAAV-CFTRDR treatment was assessed by forskolin-induced swelling in CF transmembrane conductance regulator (CFTR)-deficient organoids and by nasal potential differences in DF508 mice.
Measurements and Main Results: rAAV-CFTRDR transduction of human CFTR-deficient organoids resulted in forskolin-induced swelling, indicating a restoration of CFTR function. Nasal potential differences demonstrated a clear response to low chloride and forskolin perfusion in most rAAV-CFTRDR-treated CF mice.
Conclusions: Our study provides robust evidence that rAAVmediated gene transfer of a truncated CFTR functionally rescues the CF phenotype across the nasal mucosa of CF mice and in patientderived organoids. These results underscore the clinical potential of rAAV-CFTRDR in offering a cure for all patients with CF in the future.