HDAC9 and acute lymphoblastic leukemia: At this stage, investigational drugs targeting T-ALL are mainly classified into the following categories: (1) proteasome inhibitors (Bortezomib) [2]; (2) HDAC inhibitors (Vorinostat, Belinostat, Panobinostat Lactate, etc.)[3]; (3) Bcl-2 inhibitors (venetoclax) [4] and mitogen-activated protein kinase inhibitors, PARP inhibitors [5].