Proteostasis Therapeutics Inc. (NASDAQ: PTI) shares absolutely exploded on Thursday after the company announced positive preliminary results from its early-stage cystic fibrosis (CF) trial.

The positive preliminary results are coming from three doublet cohorts of the company’s ongoing Phase 1 studies of the company’s proprietary combination therapy doublet, PTI-808 and PTI-801, in subjects with CF.

These studies were designed to assess the safety, tolerability, and pharmacokinetics 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. Changes in sweat chloride concentration and in percent predicted FEV1 (ppFEV1) were assessed and evaluated as endpoints.

In terms of the preliminary results, the Proteostasis said:

A dose-dependent improvement in ppFEV1 and sweat chloride concentration was observed across cohorts. For ppFEV1, a maximum and statistically significant increase from baseline to day 7 of +6.3% and at day 14 of +5.9% was reported in the PTI-801 300 mg/PTI-808 300 mg dose cohort. A statistically significant increase from placebo was also noted from baseline to day 7 of +8.3% and at day 14 of +6.6% in this cohort.  A statistically significant decrease in sweat chloride concentration from baseline was also observed at day 7 and at day 14 of approximately 13 mmol/L in the PTI-801 300 mg/PTI-808 300 mg dose cohort.  The fourth and highest dose cohort, patients receiving PTI-801 (400 mg) and PTI-808 (300 mg), is ongoing, with data expected in the first quarter of 2019.

Carsten Schwarz, MD, head of the Adult Cystic Fibrosis Centre, Lung-Transplantation Program, and Endoscopy Unit, Department of Pediatric Pneumology and Immunology, Charité, Berlin University Medical Center, commented:

Doublet combinations, the current standard of care for many CF patients, are the benchmark for current treatment in cystic fibrosis.  These data are the first results seen using an entirely new CF doublet, compare favorably to standard of care, and demonstrate the potential of next-generation CFTR modulators to further improve outcomes in this disease. I look forward to results from the fourth dosing cohort and to understanding the potential of another novel combination, PTI-801, PTI-808 and PTI-428.

The company also confirmed today that the first dose cohort using its proprietary triplet combination of PTI-801, PTI-808 and PTI-428, a novel CFTR amplifier, is on track to deliver preliminary data in the fourth quarter of 2018, with complete data from the doublet and triplet cohorts expected in the first quarter of 2019.

Shares of Proteostasis were last seen up over 300% at $7.59, with a consensus analyst price target of $13.50 and a 52-week trading range of $1.41 to $8.61.

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