Proteostasis Therapeutics was a clinical-stage biopharmaceutical company focused on discovering and developing small-molecule therapeutics to treat cystic fibrosis and other diseases caused by dysfunctional protein processing. Founded in 2006 and based in Boston, Massachusetts, the company traded on Nasdaq under the ticker PTI. After its CF drug candidates underperformed against Vertex's pipeline, Proteostasis merged with Yumanity Therapeutics in 2020.