Deoxyuridine triphosphate (dUTP) is a deoxynucleotide triphosphate (dNTP) that is chemically similar to uridine triphosphate (UTP) except that it has a deoxyribose sugar instead of a ribose sugar. DNA synthesis requires the availability of deoxynucleotide triphosphates (dTTP, dATP, dGTP, dCTP), whereas RNA synthesis requires the availability of nucleotide triphosphates (NTPs) such as TTP, ATP, GTP, and UTP. The conversion of nucleotide triphosphates (NTPs) into dNTPs can only be done in the diphosphate form. Typically, an NTP has one phosphate removed to become an NDP. This is then converted into a dNDP by an enzyme called ribonucleotide reductase and followed by the re-addition of phosphate to give a dNTP. dUTP is a substrate for several enzymes, including inosine triphosphate pyrophosphatase, deoxyuridine 5'-triphosphate nucleotidohydrolase (mitochondrial), uridine-cytidine kinase 1, nucleoside diphosphate kinase 3, nucleoside diphosphate kinase B, nucleoside diphosphate kinase 6, nucleoside diphosphate kinase (mitochondrial), nucleoside diphosphate kinase homolog 5, nucleoside diphosphate kinase A, and nucleoside diphosphate kinase 7. While UTP is routinely incorporated into RNA, dUTP is not normally incorporated into DNA. Instead, if dUTP is misincorporated into DNA, it can cause DNA damage. Therefore, dUTP can be considered as a teratogen or a mutagen. The extent of DNA damage caused by dUTP is highly dependent on the levels of the dUTP pyrophosphatase (dUTPase) and uracil-DNA glycosylase (UDG), which limits the intracellular accumulation of dUTP. Additionally, loss of viability following thymidylate synthase (TS) inhibition occurs as a consequence of the accumulation of dUTP in some cell lines and subsequent misincorporation of uracil into DNA.