(E)-2'-Deoxy-2'-(fluoromethylene)cytidine, also known as Tezacitabine, is a synthetic nucleoside analogue with the CAS number 130306-02-4. Its structure features a unique (E)-fluoromethylene group replacing the 2'-deoxyribose moiety, which confers distinct biochemical properties. Tezacitabine is primarily an investigational antineoplastic agent. It functions as a potent inhibitor of ribonucleotide reductase (RR), a key enzyme responsible for the *de novo* synthesis of deoxyribonucleotides, which are essential for DNA replication and repair. By inhibiting RR, Tezacitabine depletes cellular dNTP pools, leading to DNA synthesis inhibition and ultimately inducing cell death, particularly in rapidly dividing cancer cells. It has been studied for its potential in treating various solid tumors and hematological malignancies. As a cytidine analogue, it also falls under the category of nucleoside derivatives used in biochemical and pharmacological research. Its development highlights the strategy of modifying nucleoside structures to create novel chemotherapeutic agents with targeted mechanisms of action.