<unk>  is hydrophilic and must be transported into cells via molecular transporters for nucleosides (the most common transporters for<unk>  are SLC29A1 SLC28A1, and SLC28A3). After entering the cell,<unk>  is first modified by attaching a phosphate to it, and so it becomes<unk>  monophosphate <unk> MP). This is the rate-determining step that is catalyzed by the enzyme deoxycytidine kinase (DCK). Two more phosphates are added by other enzymes. After the attachment of the three phosphates<unk>  is finally pharmacologically active as<unk>  triphosphate <unk> TP). After being thrice phosphorylated,<unk>  can masquerade as deoxycytidine triphosphate and is incorporated into new DNA strands being synthesized as the cell replicates. When<unk>  is incorporated into DNA it allows a native, or normal, nucleoside base to be added next to it. This leads to "masked chain termination" because<unk>  is a "faulty" base, but due to its neighboring native nucleoside it eludes the cell's normal repair system (base-excision repair). Thus, incorporation of<unk>  into the cell's DNA creates an irreparable error that leads to inhibition of further DNA synthesis, and thereby leading to cell death. The form of<unk>  with two phosphates attached <unk> DP) also has activity; it inhibits the enzyme ribonucleotide reductase (RNR), which is needed to create new DNA nucleotides. The lack of nucleotides drives the cell to uptake more of the components it needs to make nucleotides from outside the cell, which also increases uptake of<unk> .
Gemcitabine
Ifosfamide
Doxorubicin
Normustine
Vincristine
Lipoplatin
Fluorouracil
Carboplatin