Personalized assessment of the effectiveness of targeted drugs for the treatment of cystic fibrosis in a patient with c.264_268delATATT and c.3139+1G>C rare variants of the <i>CFTR</i> gene

Abstract

BACKGROUND: When new, most often rare CFTR gene variants, are detected in patients with cystic fibrosis, intestinal organoids are used, which allows for the assessment of the residual functional activity of the CFTR channel and the effect of targeted drugs to determine the possibility of further pathogenetic therapy. Clinical trials of the effectiveness of the targeted drugs in patients with rare CFTR variants are expensive, and patient groups are extremely small. A forskolin-induced swelling assay on a patient’s intestinal organoids allows for a personalized approach when studying rare or even single CFTR variants. AIM: To examine the effect of the CFTR potentiator ivacaftor and the combination of ivacaftor with the CFTR correctors lumacaftor, tezacaftor, and elexacaftor on the restoration of CFTR channel functions on a culture of intestinal organoids obtained from a patient with two rare CFTR variants c.264_268delATATT and c.3139+1GC. MATERIALS AND METHODS: To assess the activity of the CFTR channel, the forskolin-induced swelling assay on organoids and intestinal current measurements on rectal biopsy samples method were used. The clinical picture of a patient with the c.264_268delATATT/c.3139+1GC genotype was described. RESULTS: In vitro, the genetic variants c.264_268delATATT and c.3139+1GC lead to a complete loss of the functional CFTR protein, whereas CFTR modulators do not positively affect and do not lead to the restoration of CFTR function, in contrast from F508del/F508del control. The disease severity in a child is consistent with the results of functional tests. CONCLUSION: Both CFTR variants are classified as “severe” and cause a complete loss of chloride channel activity. No effective CFTR modulators were found for the c.264_268delATATT and c.3139+1GC variants; thus, targeted therapy cannot be recommended to the patient.