Proof-of-concept Study to Evaluate the Safety, Tolerability, Pharmacodynamics, and Pharmacokinetics of SION-719 When Added to Trikafta

The purpose of this study is to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of SION-719 when given to people with CF who are already taking Trikafta.

Inclusion Criteria: * Diagnosis of CF with F508del homozygous genotype based on documented CFTR genotype laboratory report. * Adherent to physician-prescribed Trikafta, as assessed by the Investigator, for at least 3 months prior to the Screening visit, taken at the recommended dose without modifications and on the regimen described in the current prescribing information. * Stable CF disease without pulmonary exacerbation within 28 days before Baseline or acute non-CF-related illness within 14 days before Baseline. Exclusion Criteria: * Participant has clinically significant current or recurrent illness, other than CF * Participant has a history of malignancy, except for basal cell or squamous epithelial carcinomas of the skin that have been resected with no evidence of recurrence for at least 1 year.