ON123300 is a potent small molecule inhibitor primarily investigated for its antitumor activity. It functions by targeting key cell cycle regulators, specifically cyclin-dependent kinases (CDKs) and dual-specificity tyrosine-regulated kinases (DYRKs), which play critical roles in cancer cell proliferation. Due to its ability to cross the blood-brain barrier, ON123300 shows promise in treating central nervous system (CNS) malignancies, including glioblastoma and other brain tumors. It has demonstrated efficacy in preclinical models against tumor cells with dysregulated cell cycle pathways, especially those resistant to conventional chemotherapy. Additionally, ON123300 is being explored for its potential in neurodegenerative conditions, where DYRK1A inhibition may offer neuroprotective benefits. Its dual mechanism of action makes it a candidate for both oncology and neurological disorder research.