Importantly, in PDX-derived T-ALL cells with activating Notch1 mutations (TET2 mut, U2AF1 mut, WT1 mut), ARV-825 inhibited proliferation and induced apoptosis in bulk as well as in the CD34+ CD7+ LIC subset (Supplementary Fig. 2I). The gene discussed is TET2; the disease is acute lymphoblastic leukemia.