Proteostasis Therapeutics Inc. (NASDAQ: PTI) saw its shares skyrocket going into Tuesday’s session following a pivotal decision from the U.S. Food and Drug Administration (FDA) for the firm’s cystic fibrosis (CF) therapy. Essentially, the agency granted a Breakthrough Therapy Designation for PTI-428, the company’s cystic fibrosis transmembrane conductance regulator (CFTR) amplifier.

Ultimately, the FDA Breakthrough Therapy Designation is intended to expedite the development and review of a drug aimed at treating a serious or life-threatening disease when there is a significant unmet need and preliminary clinical evidence indicates that the drug may offer substantial improvement over existing therapies.

As for Proteostasis, this designation was based on the results from a recent Phase 2 study. The study results showed that treatment with PTI-428 led to mean absolute improvement in percent predicted forced expiratory volume in 1 second (ppFEV1) of 5.2 percentage points from the baseline.

At the same time, consistent with the CFTR amplifier mechanism of action, a positive increase in nasal mucosal CFTR protein was observed in PTI-428 treated subjects and the magnitude of change compared to baseline was consistent with the changes in CFTR protein levels observed in the in vitro human bronchial cell model, whereas the placebo subjects had no significant increase in CFTR protein during the treatment period.

Meenu Chhabra, president and CEO of Proteostasis, added:

We believe the Breakthrough Therapy Designation for PTI-428 reflects the strength of the recent Phase 2 study results for our amplifier, a novel and proprietary class of CFTR modulators. PTI-428 can potentially be added to current and future standards of care, offering the potential for improvement in pulmonary function for patients with cystic fibrosis. We look forward to working closely with the FDA as we advance our clinical programs for PTI-428, including as part of our proprietary triple combination with PTI-801 and PTI-808, our third generation corrector and potentiator, respectively.

Shares of Proteostasis closed Monday at $4.14, with a consensus analyst price target of $16.00 and a 52-week trading range of $1.41 to $13.16. Following the announcement, the stock was up about 54% at $6.31 in early trading indications Tuesday.

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