Study Designed to Assess the Safety, Tolerability and PK of PTI-808 in Healthy Volunteers and in Adults With Cystic Fibrosis

Part 1 of this trial will enroll healthy volunteers into a single ascending dose (SAD), multiple ascending dose (MAD), and Food Effect (FE) treatment groups. The SAD treatment group is comprised of at least 3 ascending dose level cohorts where healthy adult subjects will be randomized to receive a single dose of either PTI-808 or placebo and will be followed for 7 days post dose. The MAD treatment group is comprised of 3 ascending dose level cohorts where subjects will be randomized to receive either PTI-808 or placebo daily for 7 days and will be followed for 7 days after receiving the last dose. Following the conclusion of the respective SAD level dose groups the food effect portion of the study will be initiated and subjects will be randomized to receive an initial single dose of PTI-808 either after an overnight fast of at least 10 hours (fasted group) or after an overnight fast of at least 10 hours followed the consumption of a high fat high calorie meal (fed group). After a 10 day washout period, subjects will cross over to the opposite group and receive a second dose of PTI-808. Subjects will be followed for up to 7 days following dosing. Part 2 of this will enroll healthy volunteers to assess the safety, tolerability, and PK of PTI 808 co administered with PTI 801 and PTI 428 to HVs with daily dosing for 7 consecutive days. Part 3 - Part 3 will enroll adult subjects with CF to assess the safety, tolerability, and PK of multiple ascending doses of PTI-808 co-administered with PTI-801 and PTI-428. Subjects will receive 7 days of PTI-808 or placebo followed by 14 days of PTI-808 or placebo co-administered with PTI-801+PTI-428 or matching placebos. Part 4 - Part 4 will assess the safety, tolerability, PK, and the effects of PTI-808 co-administered with PTI-801 with or without PTI-428 over a 28-day treatment period in CF subjects who are either homozygous for the F508del CFTR genotype or are heterozygous for the F508del CFTR genotype. Subjects will be randomized to receive treatment with PTI-808 co-administered with PTI-801 with or without PTI-428 versus matching placebo.