PROTAC IDO1 Degrader-1 is the first potent IDO1 (indoleamine 2,3-dioxygenase 1) degrader that hijacks IDO1 to Cereblon E3 ligase to introduce IDO1 into UPS and eventually achieve ubiquitination and degradation (DC50=2.84 μM). PROTAC IDO1 Degrader-1 moderately improves the tumor-killing activity of H ER2 CAR-T cells.