Proteostasis Therapeutics, Inc. announced results from in vitro studies evaluating the use of PTI-129 as a treatment for COVID-19. PTI-129 is a pre-clinical, once-daily, oral small molecule originally designed to treat protein misfolding disorders involving the unfolded protein response (UPR). Upon infection, coronaviruses hijack the host cell endoplasmic reticulum (ER) to quickly produce a larger quantity of misfolding-prone viral glycoproteins. The accumulation of misfolded and unfolded proteins in the ER causes ER stress and induces the UPR. in vitro studies conducted at Calibr, the drug discovery division of Scripps Research, PTI-129 demonstrated the potential to reduce viral protein production in host cells by activating the adaptive branches of the UPR pathway and reducing the levels of misfolded proteins.