Proteostasis Therapeutics, Inc. announced completion of enrollment in the Company's global, multicenter, randomized, placebo-controlled, 28-day, Phase 2 study evaluating its proprietary cystic fibrosis transmembrane conductance regulator (CFTR) modulator combinations in F508del homozygous and heterozygous CF subjects. The trial is designed to assess the efficacy, safety and tolerability of PTI's proprietary combinations over four weeks and with higher doses of proprietary CFTR corrector and potentiator. Dose selection (600 mg of PTI-801 and 300 mg of PTI-808, with or without 10 mg of PTI-428) was based on the totality of dose range finding data from approximately 250 CF subjects studied thus far. Study endpoints include safety, changes in sweat chloride concentration and changes in percent predicted FEV1 (ppFEV1). The study design targeted up to 30 F508del homozygous and up to 30 F508del heterozygous subjects. Due to rapid enrollment from centers in the United States, Canada, Western Europe, and New Zealand, data from the study are now expected in the fourth quarter of 2019 instead of the first quarter of 2020. The 28-day Phase 2 study follows the positive results of the 14-day Phase 1 clinical studies of PTI's proprietary doublet and triplet combinations in F508del homozygous patients, including those predisposed to rapid pulmonary decline based on their bacterial colonization status. The previous studies demonstrated a favorable safety and tolerability profile for the combinations, as well as a statistically significant improvement in ppFEV1 and sweat chloride concentration that was superior to the available dual CFTR modulator standard of care.