@article {DE CLERCQ422, author = {ERIK DE CLERCQ and JOHAN DESCAMPS and GUANG-FU HUANG and PAUL F. TORRENCE}, title = {5-Nitro-2{\textquoteright}-deoxyuridine and 5-Nitro-2{\textquoteright}-deoxyuridine 5{\textquoteright}-Monophosphate: Antiviral Activity and Inhibition of Thymidylate Synthetase in Vivo}, volume = {14}, number = {3}, pages = {422--430}, year = {1978}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {The antiviral activity of a series of nitrated uracil derivatives, including 5-nitrouracil, 1-methyl-5-nitrouracil, 1,3-dimethyl-5-nitrouracil, 5-nitro-2{\textquoteright}-deoxyuridine (5-nitro-dU), 3{\textquoteright}-O,5-dinitro-2{\textquoteright}-deoxyuridine, 5-nitro-2{\textquoteright}-deoxyuridine 5{\textquoteright}-monophosphate (5-nitro-dUMP), and 3{\textquoteright}-O,5-dinitro-2{\textquoteright}-deoxyuridine 5{\textquoteright}-monophosphate, was evaluated in primary rabbit kidney or human skin fibroblast cultures challenged with vaccinia, herpes simplex, or vesicular stomatitis virus. The most remarkable antiviral activity was shown by 5-nitro-dU and 5-nitro-dUMP, which inhibited the replication of vaccinia virus at concentrations as low as 0.1-0.4 {\textmu}g/ml. Somewhat higher concentrations were required to inhibit the replication of herpes simplex virus (1-4 {\textmu}g/ml for 5-nitro-dU and 40-100 {\textmu}g/ml for 5-nitro-dUMP). Neither 5-nitro-dU nor its 5{\textquoteright}-monophosphate was inhibitory to vesicular stomatitis virus at concentrations up to 100 {\textmu}g/ml. Combination of 5-nitro-dU with 5-iodo-2{\textquoteright}-deoxyuridine (5-iodo-dU) resulted in an increased antiviral activity over the activity of the compounds used individually, suggesting that 5-nitro-dU and 5-iodo-dU act at different steps in DNA biosynthesis. In fact, 5-nitro-dU and its 5{\textquoteright}-monophosphate effectively blocked the incorporation of [14C]2{\textquoteright}-deoxyuridine into host cell DNA, but neither compound inhibited the incorporation of [3H]2{\textquoteright}-deoxythymidine, pointing to thymidylate synthetase as a specific target for the action of 5-nitro-dU (or 5-nitro-dUMP). Inhibition of thymidylate synthetase would account for the antiviral activity of 5-nitro-dU, since the inhibitory effect of 5-nitro-dU on vacciia virus replication could be readily reversed by 2{\textquoteright}-deoxythymidine, but not by 2{\textquoteright}-deoxyuridine or 2{\textquoteright}-deoxycytidine. Other deoxythymidine analogues that were found to inhibit deoxyuridine incorporation, but not deoxythymidine incorporation, and could therefore be assumed to block thymidylate synthetase selectively in vivo, include 5-fluoro-, 5-trifluoromethyl-, 5-cyamo-, and 5-thiocyamato-2{\textquoteright}-deoxyuridine.}, issn = {0026-895X}, URL = {https://molpharm.aspetjournals.org/content/14/3/422}, eprint = {https://molpharm.aspetjournals.org/content/14/3/422.full.pdf}, journal = {Molecular Pharmacology} }