Study Designed to Assess a CFTR modulator in Adults with Cystic Fibrosis
In this study, the investigational CFTR modulator medicine PTI-808 will be given in combination with one or two other investigational modulator medicines, PTI-801 and PTI-428. PTI-428, PTI-801, and PTI-808 are considered cystic fibrosis transmembrane conductance regulator (CFTR) modulators being developed to treat the underlying cause of cystic fibrosis. PTI-428 is a CFTR amplifier that increases the amount of CFTR protein in the cell, PTI-801 is a CFTR corrector that improves the processing of CFTR protein in the cell, and PTI-808 is a CFTR potentiator to enhance the activity of CFTR at the cell surface. Modulators on their own have been shown to have limited activity, and it is predicted that combining modulators will be necessary to address CFTR defects. There is a screening visit up to 4 weeks before the active portion of the study, which lasts 4 weeks. In the active portion of the study, participants will take one of the following: PTI-808 by mouth in combination with PTI-801 and PTI-428, PTI-808 in combination with PTI-801 and placebo, or all placebos for 4 weeks. The study medication is taken once a day at breakfast. Two weeks after stopping the study medication, another visit will occur.