Proteostasis Therapeutics Provides Clinical Enrollment Update

BOSTON, Dec. 20, 2018 /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) and other diseases caused by dysfunctional protein processing, today provided a clinical enrollment update. The Company, while remaining blinded to data from the first cohort, now expects to report complete efficacy and safety data from the Phase 1, randomized, double-blind, placebo-controlled study of its proprietary combination therapy triplet (PTI-808, PTI-801, and PTI-428) and from the high-dose doublet study in subjects with CF in the first quarter of 2019. The Company previously planned to report preliminary results from the triplet study by dose cohort as each dose cohort was completed, beginning with a low-dose cohort.

Proteostasis' proprietary triplet is comprised of PTI-801, a third-generation cystic fibrosis transmembrane conductance regulator (CFTR) corrector, PTI-808, a novel CFTR potentiator, and PTI-428, a novel CFTR amplifier. As part of the endorsement by the Cystic Fibrosis Foundation (CFF), an independent Data Safety and Monitoring Board (DSMB) has been established to review safety data and approve progression onto higher dose cohorts. The CFF DSMB review has indicated that CF patients in the first, low-dose cohort, showed that the triple combination was generally well tolerated and dose escalation for the second cohort of the study was approved.

In addition to the proprietary triplet study, Proteostasis is conducting studies exploring a proprietary doublet (PTI-808 and PTI-801), and separate studies of PTI-801 and PTI-428 with background SYMDEKO(®) (tezacaftor/ivacaftor and ivacaftor) therapy, in CF subjects. All four studies are on track to read out in the first quarter of 2019.

"We believe a comprehensive data set from our proprietary doublet and triplet studies will provide evidence of the individual contribution of each drug candidate to the overall activity of the combinations, supporting Phase 3 dose selection rationale," said Meenu Chhabra, President and Chief Executive Officer of Proteostasis. "In addition to our proprietary combinations, we remain as excited about our add-on portfolio, with both strategies reinforcing our commitment to expanding treatment options for CF patients. Given that the anticipated timing of these study readouts across this portfolio of programs remains Q1 2019, assuming positive results, we expect to be in a position to initiate Phase 3 studies within the next 12-18 months."

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 www.proteostasis.com.

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 potential of our proprietary combination therapies for the treatment of CF, the potential benefit to patients of our proprietary combination therapies, expected presentations and expected timing of the initiation of, patient enrollment in, data from, and the completion of, our clinical studies and cohorts for our clinical programs. 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 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 comments delay, change or do not permit trial commencement, or intended label, or the FDA 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), and those set forth in our Quarterly Report on Form 10-Q for the quarter ended September 30, 2018 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.

CONTACTS:

Investors:
David Pitts / Claudia Styslinger
Argot Partners
212.600.1902
david@argotpartners.com / claudia@argotpartners.com

Media:
David Rosen
Argot Partners
212.600.1902
david.rosen@argotpartners.com

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SOURCE Proteostasis Therapeutics, Inc.