Proteostasis Therapeutics Inc. (NASDAQ: PTI) shares were absolutely crushed on Tuesday after the firm announced midstage data from its cystic fibrosis (CF) study. Ultimately, the results from the study were mixed, and considering this stock was valued less than $1 only two months ago, investors quickly sent shares lower.

The company announced positive topline results from its Phase 2 study evaluating its proprietary cystic fibrosis transmembrane conductance regulator (CFTR) modulator combinations in F508del homozygous and heterozygous CF subjects.

The compounds were generally well tolerated, and the majority of reported adverse events were mild to moderate in severity. Most subjects enrolled in the Phase 2 study carried a high disease burden, with over 80% of subjects trying and failing to enroll into trials of currently approved modulators due to ineligibility.

Based on the results, Proteostasis is planning to launch a global, Phase 3 More trial in CF subjects with the common F508del homozygous mutation, beginning in 2020. The More trial complements the Choices trial. Choices, which is also expected to initiate in 2020, will be the first-ever personalized medicine-based study in CF.

Geoffrey Gilmartin, M.D., MMSc, chief medical officer of Proteostasis, commented:

We look forward to advancing our triple combination into a pivotal study next year, while simultaneously pursuing a personalized medicine clinical and regulatory pathway together with the HIT-CF funded through the European Commission Horizon 2020 program. We are very grateful to the patients, their families and healthcare providers who have supported PTI in our pursuit of delivering more choices to people with CF and to providing the benefit of CFTR modulators to all, regardless of mutation status.

Shares of Proteostasis were last seen down 57% at $1.84, in a 52-week range of $0.61 to $4.72. The consensus price target is $7.00.

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