In preclinical in vitro studies, the antiproliferation activity of TNG908 was 15 times more potent in MTAP-null cancer cell lines than in MTAP WT cells….TNG908 demonstrated dose-dependent antitumor activity in multiple hyper- and hypomethylated GBM subcutaneous models, including cell lines and patient-derived xenograft models....TNG908 is a potent, brain-penetrant small molecule PRMT5 inhibitor that is selective for MTAP-null tumor cells with good drug-like properties and strong antitumor activity in preclinical models of GBM.