Global prevalence of CFTR variants with respect to their responsiveness to elexacaftor-tezacaftor-ivacaftor

Background: Elexacaftor-tezacaftor-ivacaftor (ETI) is mostly approved in people with cystic fibrosis (pwCF) with a p.Phe508del CFTR variant. The US Food and Drug Administration (FDA) approved ETI for an additional 177 rare CFTR variants and studies identified 7 non-FDA approved variants also responsive to ETI. The global impact of expanding the ETI label to rare responsive CFTR variants on the number of eligible pwCF is unknown. Methods: Data were obtained from CF registries and individual CF clinics in countries without registries. Individuals were classified according to five mutually-exclusive categories (1) at least one p.Phe508del variant (2) at least one of the 177 FDA-approved variants (3) at least one non-FDA-approved variant responsive to ETI (4) two variants resulting in no CFTR protein (5) all other variants. The first 3 groups were considered responsive to ETI, group 4 was nonresponsive and group 5 of undetermined responsiveness. Results: Data were obtained from 95,838 pwCF living in 69 countries: 78,566 (82.0 %) had at least one p.Phe508del, 6175 (6.4 %) at least one FDA-approved variants, and 2981 (3.1 %) at least one non-FDA-approved responsive variants. Two variants resulting in no CFTR protein were found in 3574 (3.7 %) and other variant combinations in 4490 (4.7 %). The prevalence of p.Phe508del ranged from 7 % to 98 % in individual countries and expanding the eligibility to responsive non-p.Phe508del variants resulted in greatest eligibility increase in countries with low p.Phe508del prevalence. Conclusion: Expanding the label of ETI to rare responsive CFTR variants will make at least 91.5 % of pwCF eligible to this disease-modifying therapy.