Shares of Proteostasis Therapeutics Inc. (NASDAQ:PTI) roared Thursday, spiking to an 18-month high of $10.38, following an update on three cohorts covering 21 patients from the company's ongoing phase I study of combination doublet, PTI-801/PTI-808, in individuals with cystic fibrosis (CF). The stock closed at $10.35 for a gain of $8.46, or 447.6 percent. Volume of nearly 92.6 million shares was some 580 times the company's three-month moving average.