TPST-8844

**TPST-8844** is an oral small molecule developed by Tempest Therapeutics as a potent inhibitor of indoleamine 2,3-dioxygenase 1 (IDO1), an enzyme overexpressed in tumor cells that catabolizes tryptophan, leading to immunosuppressive effects via kynurenine accumulation and suppression of T-cell activity in the tumor microenvironment. Preclinical data indicate superior potency and pharmacokinetics compared to other IDO inhibitors, including lower plasma protein binding for enhanced cellular penetration, with synergistic potential when combined with checkpoint inhibitors like anti-PD-1 for multiple malignancies. Originally the lead program funded by a $70M Series B in 2018 to enter clinic within 12 months, development has since shifted to other Tempest assets.[1][5][9]