Proteostasis Therapeutics, Inc. announced positive, initial ex-vivo results of PTI's proprietary cystic fibrosis transmembrane conductance regulator (CFTR) modulators, PTI-801, PTI-808, and PTI-428, in individuals with CF who are ineligible for the current standard of care CFTR modulator therapies due to their genotype. The data are part of a pan-European strategic initiative, known as HIT-CF (Human Individualized Therapy of CF), which seeks to accelerate the development of, and access to, personalized therapies for CF patients, beginning with those for whom no currently approved CFTR modulator therapy is indicated. HIT-CF is sponsored by the European Commission Horizon 2020 program, in which CF-Europe, a patient organization representing more than 48,000 individuals with CF, collaborates and with the European Cystic Fibrosis Society Clinical Trial Network (ECFS-CTN), which is recruiting adult CF patients into the ex- vivo ­study through its 43 clinical trial centers. HIT-CF collects tissue samples from CF patients and develops organoids, or miniaturized organs, that are genetically identical to the patient donor, and share the same micro-anatomy as the organ from which they were derived. As of today, rectal organoids from over 300 subjects have been collected for functional profiling and of those, 65 have been tested for response to PTI's investigational drugs. Early results support the initiation of enrollment of responding subjects into HIT-CF's clinical trial known as "CHOICES" (Crossover trial based on Human Organoid Individual response in CF - Efficacy Study), which is designed to evaluate the translation of organoid ex-vivo response to potential clinical benefit, such as changes in FEV1 and sweat chloride. CHOICES, which is expected to initiate in mid-2020, will be the first ever personalized medicine-based study in CF, with initial data expected by the end of 2020. Fully funded by the HIT-CF, this trial is a placebo controlled, double blind, crossover study with an 8-week treatment period and 6 months of uninterrupted dosing. The results may serve as the basis for a potential Marketing Authorization Application with the European Medicines Agency (EMA) in 2021 through a novel regulatory pathway which is being pursued jointly by Proteostasis and HIT-CF. The CHOICES clinical study is part of PTI's broader clinical development strategy for its CFTR modulator candidates that is already separately funded for the common genotypes. Results from the HIT-CF project to date will be presented at the Keystone Symposia on Tissue Organoids titled "Tissue Organoids as Models of Host Physiology and Pathophysiology of Disease (J1)" taking place on January 19-23, 2020 in Vancouver, BC, Canada.