Proteostasis Therapeutics Inc., of Cambridge, Mass., set terms for its IPO, filing with the SEC to raise $50 million by offering 3.9 million shares priced in a range of $12 to $14. The company said certain shareholders expressed interest in purchasing $30 million of shares in the offering. Proteostasis plans to list on the Nasdaq as PTI. Leerink Partners and RBC Capital Markets are joint bookrunners.