Tagtociclib, also known as PF-07104091, is an orally bioavailable inhibitor of cyclin-dependent kinase 2 (CDK2), with potential antineoplastic activity. Upon administration, CDK2 inhibitor PF-07104091 selectively targets, binds to and inhibits the activity of CDK2. This may lead to cell cycle arrest, the induction of apoptosis, and the inhibition of tumor cell proliferation. CDKs are serine/threonine kinases that are important regulators of cell cycle progression and cellular proliferation and are frequently overexpressed in tumor cells. CDK2/cyclin E complex plays an important role in retinoblastoma (Rb) protein phosphorylation and the G1-S phase cell cycle transition. CDK2/cyclin A complex plays an important role in DNA synthesis in S phase and the activation of CDK1/cyclin B for the G2-M phase cell cycle transition.