How Proteostasis Will Capitalize on Its Big Cystic Fibrosis Win

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Proteostasis Therapeutics Inc. (NASDAQ: PTI) shares pulled back on Tuesday after the company announced that it would conduct a secondary offering. This is all in response to the firm’s positive preliminary results from its early-stage cystic fibrosis trial announced last week.

The company intends to offer 9 million shares, with an overallotment option for an additional 1.35 million shares. Note that all the shares to be sold in the offering are to be sold by Proteostasis. No pricing details were mentioned in the release.

Leerink Partners, Piper Jaffray and Cantor Fitzgerald are acting as joint book-running managers for the offering. H.C. Wainwright is acting as lead manager for the offering.

The positive preliminary results come 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 cystic fibrosis.

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.

Shares of Proteostasis were last seen down 4% at $6.90, with a consensus analyst price target of $14.75 and a 52-week trading range of $1.41 to $10.38.

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