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Proteostasis Therapeutics Announces Completion of Enrollment in Global Phase 2 Study in Cystic Fibrosis

November 6, 2019 at 7:00 AM EST
Company Now Expects Phase 2 Top-line Data Later in Q4 of 2019 Instead of Q1 2020 Due to Rapid Enrollment

BOSTON, Nov. 6, 2019 /PRNewswire/ -- Proteostasis Therapeutics, Inc. (NASDAQ: PTI), a clinical stage biopharmaceutical company dedicated to the discovery and development of groundbreaking therapies to treat cystic fibrosis (CF), today 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.

"We are working hard to introduce the power of choice to the CF community and the completion of enrollment in our global Phase 2 study is an important step forward to completing that mission. We heard loud and clear at our recently hosted Cystic Fibrosis Summit, as well as at the last week's North American CF Conference, that the community urgently demands options to address the inequity in access, variability in clinical response and genetic disparity amongst people with CF," said Geoffrey Gilmartin, M.D., M.M.Sc., Chief Medical Officer of Proteostasis. "Due to this strong demand for options and additional trials from the patient and medical community, we're pleased to announce that we now expect top-line data from the Phase 2 study later this quarter."

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.

About PTI-428, PTI-801, PTI-808
PTI-428 is an investigational CFTR amplifier in development for the treatment of CF in patients with at least one F508del mutation in the CFTR gene, as part of PTI's proprietary triple combination regimen that includes PTI-808, a novel potentiator, and PTI-801, a third-generation CFTR corrector. PTI-801 received Fast Track Designation from the U.S. Food and Drug Administration (FDA).  In May 2019, PTI-428 received Orphan Drug Designation (ODD) from the European Commission (EC).  In addition to ODD from the EC, PTI-428 has ODD, Breakthrough Therapy Designation and Fast Track Designation from the FDA. 

About Proteostasis Therapeutics, Inc.
Proteostasis Therapeutics, Inc. is a clinical stage biopharmaceutical company developing small molecule therapeutics to treat cystic fibrosis and other diseases caused by dysfunctional protein processing. Headquartered in Boston, MA, the Proteostasis Therapeutics team focuses on identifying therapies that restore protein function. For more information, visit

Safe Harbor
To the extent that statements in this release are not historical facts, they are forward-looking statements reflecting the current beliefs and expectations of management made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.  Words such as "aim," "may," "will," "expect," "anticipate," "estimate," "intend," and similar expressions (as well as other words or expressions referencing future events, conditions or circumstances) are intended to identify forward-looking statements. Examples of forward-looking statements made in this release include, without limitation, statements regarding the ongoing trials of our product candidates, the expected timing for completion and reporting of topline results of our Phase 2 clinical trial and our expectations regarding expanding available therapeutic options for CF patients. Forward-looking statements made in this release involve substantial risks and uncertainties that could cause actual results to differ materially from those expressed or implied by the forward-looking statements, and we, therefore cannot assure you that our plans, intentions, expectations or strategies will be attained or achieved.  Such risks and uncertainties include, without limitation, the potential of our proprietary combination therapies for the treatment of CF, the potential benefit of our proprietary combination therapies to patients, expected completion of our clinical studies and cohorts for our clinical programs, including our planned Phase 2 program and initiation of a pivotal study, the possibility final or future results from our drug candidate trials (including, without limitation, longer duration studies) do not achieve positive results or are materially and negatively different from or not indicative of the preliminary results reported by the Company (noting that these results are based on a small number of patients and small data set), uncertainties inherent in the execution and completion of clinical trials (including, without limitation, the possibility that FDA or other regulatory agency comments delay, change or do not permit trial commencement, or intended label, or the FDA or other regulatory agency requires us to run cohorts sequentially or conduct additional cohorts or pre-clinical or clinical studies), in the enrollment of CF patients in our clinical trials in a competitive clinical environment, in the timing of availability of trial data, in the results of the clinical trials, in possible adverse events from our trials, in the actions of regulatory agencies, in the endorsement, if any, by therapeutic development arms of CF patient advocacy groups (and the maintenance thereof), in the commercialization and acceptance of new therapies, and those set forth in our Annual Report on Form 10-K for the year ended December 31, 2018, our Quarterly Report on Form 10-Q for the quarter ended June 30, 2019 and our other SEC filings. We assume no obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.


David Pitts / Claudia Styslinger
Argot Partners
212.600.1902 /

David Rosen
Argot Partners

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SOURCE Proteostasis Therapeutics, Inc.