YB-3-17 is a bifunctional molecule, that inhibits mTOR ( IC 50 =0.22 nM) or degrades G1 to S phase transition 1 gene ( GSPT1 , DC 50 =5 nM) in a PROTAC mechanism. YB-3-17 exhibits antiproliferative activity in multi glioblastoma cell lines with IC 50 of nanomolare levels. YB-3-17 exhibits antitumor efficacy in mouse models. (Pink: ligand for target protein ; Black: linker ; Blue: ligand for E3 ligase Cereblon )