A Phase 2 Study to Evaluate the Safety, Tolerability, PK and PD of ELX-02 in Cystic Fibrosis Patients With G542X Allele

This is a Phase 2 open-label, dose-escalation study to evaluate the safety, tolerability, PK, and PD of multiple dose levels of SC administered ELX-02 with and without ivacaftor in patients with CF with at least one G542X allele. In total, up to 16 patients will be enrolled in the trial; up to 4 patients will be homozygotes for G542X, and the remaining patients will be compound heterozygotes with one G542X or phenotypically similar nonsense allele and any Class 1 or Class 2 mutation. Each patient will receive up to 5 escalating doses as follows: * ELX-02 0.3 mg/kg per day SC * ELX-02 0.75 mg/kg per day SC * ELX-02 1.5 mg/kg per day SC * An individualized dose of ELX-02, as high as 3.0 mg/kg per day SC, based on the patients observed safety and tolerability, PK at previous doses and the results of laboratory tests. * ELX-02 1.5 mg/kg per day SC plus 150 mg ivacaftor every 12 bid