Here's Why Proteostasis Therapeutics Stock Plummeted Today

Shares of Proteostasis Therapeutics (NASDAQ: PTI) were down 56% at 12:07 p.m. EST on Tuesday after the company released what it called "positive" data from a phase 2 clinical trial testing its triple drug combination in patients with cystic fibrosis.

Investors rightfully didn't see the results as positive enough.

Proteostasis' headline is technically correct: Patients responded to the triple combination of dirocaftor, posenacaftor, and nesolicaftor. After 28 days, cystic fibrosis patients with two copies of the F508del mutation treated with the triple combination improved their percent predicted forced expiratory volume in one second (ppFEV1) -- a measure of lung function -- by 8 percentage points compared with placebo.

Source Fool.com