PART 1 The SAD treatment group is comprised of three cohorts where HV will be randomized to either PTI-801 or placebo. The MAD treatment group is comprised of three cohorts where subjects will be randomized to receive either PTI-801 or placebo once daily (QD) for a total of 7 days. HV will participate in a FE treatment group ,the FE treatment group is comprised of one cohort where subjects will be randomized to receive an initial single dose of PTI-801 either after an overnight fast of at least 10 hours (fasted group) or after an overnight fast of at least 10 hours followed by the consumption of a high fat high and high calorie meal (fed group). A set of HV will participate in a DDI treatment group. The DDI treatment group is comprised of one cohort where subjects will receive a 3-drug cocktail consisting of caffeine, bupropion, and midazolam on Day 1. On Day 4, subjects will be randomized to receive either PTI-801 or placebo QD for a total of 12 days. On Day 17, subjects will receive the 3-drug cocktail in combination with PTI-801 or placebo.~PART 2 Part 2 is comprised of a MAD treatment group with three cohorts, a co-administration group with two cohorts and a treatment group with one cohort.~Following the conclusion of the complementary HV MAD Cohort in Part 1, a set of adult subjects diagnosed with CF currently on a stable ivacaftor/lumacaftor background therapy for a minimum of three months will participate in the Part 2 complementary CF MAD cohort. Subjects will be randomized to receive either PTI-801 or placebo QD for a total of 14 days.~Following the conclusion of CF MAD Cohort 1 in Part 2, a set of adult subjects diagnosed with CF not currently receiving or have received background CFTR modulator therapy for a minimum of 30 days prior to Day 1 will participate in the Part 2 CF PTI-801 and PTI-808 co-administration cohort. Subjects will be randomized to receive either PTI-801 co-administered with PTI-808 or placebos QD for a total of 14 days.~Following the conclusion of the CF MAD Cohort 1 in Part 2, a set of adult subjects diagnosed with CF currently on a stable tezacaftor/ivacaftor background therapy for a minimum of one month will participate in the Part 2 complementary CF cohort. Subjects will be randomized to receive either PTI-801 or placebo QD for a total of 14 days.
This trial will consist of two parts: Part 1 and Part 2. Part 1 will enroll adult healthy volunteers (HV) into four treatment groups. The first group will enroll HV into a single ascending dose (SAD) treatment group consisting of three cohorts. The second group will enroll HV into a multiple ascending dose (MAD) treatment group consisting of three cohorts. The third group will enroll HV into a food effect (FE) treatment group consisting of one cohort. The fourth group will enroll HV into a drug-drug interactions (DDI) treatment group consisting of one cohort. Approximately 76 subjects will be enrolled in Part 1.~Part 2 Cohorts 1 through 3 will enroll adult subjects with cystic fibrosis (CF) currently on stable ivacaftor/lumacaftor background therapy for a minimum of three months. Part 2 Cohorts 4 and Cohort 5 will enroll adult subjects with CF not currently receiving cystic fibrosis conductance regulator (CFTR) modulator therapy within 30 days prior to Day 1. Part 2 Cohort 6 will enroll adult subjects with cystic fibrosis on stable tezacaftor/ivacaftor background therapy. Approximately 104 subjects will be enrolled in Part 2.