Author(s)

Richard L. Momparler

Département de Pharmacologie-Physiologie, Université de Montréal and Service de Hématologie/Oncologie, Centre de Recherche, CHU Sainte-Justine, Montréal, Québec, Canada.

Background: Molnupiravir, N4-hydroxycytidine-5’-isopropyl ester, is an oral prodrug of N4-deoxycytidine (NHC), a nucleoside analog, which has in vitro activity against SARS-CoV-2. NHC is phosphorylated in cells to NHC triphosphate (NHC-TP), which is incorporated into viral RNA, leading to epigenetic catastrophe of the viral genome and inhibition of viral replication. The antiviral activity against SARS-CoV-2 is dependent on the number of molecules of NHC-TP incorporated into viral RNA. Clinical studies in patients with COVID-19 showed that treatment with molnupiravir for 5 days decreases the risk of hospitalization and death as compared with placebo. Objective: It should be possible to enhance the antiviral activity of NHC-TP against SARS-CoV-2 by the use of the biochemical modulator, 3-deazauridine (3DU). 3DU is an inhibitor of CTP synthetase. Inhibition of this enzyme results in a reduction in the intracellular pool size of CTP. Since NHC-TP competes with CTP for incorporation into viral RNA in the reaction catalyzed by the SARS-CoV-2 viral RNA-dependent RNA polymerase, the reduction in the level of CTP should result in a significant enhancement of the incorporation of NHC-TP into viral RNA and an enhancement of its antiviral activity. Methods: Analysis of the publications of 3DU and cytosine nucleoside analogues support the hypothesis that 3DU enhances the pharmacological action of the analogues. Results: 3-DU increased the incorporation of 5-azacytidine into RNA and 5-aza-deoxycytidine into DNA of leukemic cells with an enhancement of their antineoplastic action. 3-DU potentiated the antiviral activity against HIV-1 activity by the cytosine nucleoside analogues: 2’-deoxy-3’-thiacytidine (3TC; lamivudine) and 2’,3’-dideoxycytidine (ddC). This anti-HIV-1 activity of 3DU was associated with a reduction in the intracellular pool size of dCTP and increased incorporation of triphosphates of 3TC and ddC into DNA by the HIV-1 reverse transcriptase. The reduction of CTP levels in cells by 3-DU also leads to a reduction in dCTP since CTP is its precursor. Conclusion: The preclinical studies on 3-DU indicate that it can enhance the pharmacological activity of both ribo- and deoxyribonucleoside analogues against neoplastic cells and viral infected cells. These observations suggest that 3-DU also has the potential to enhance the antiviral activity of molnupiravir and arrest the progression of the disease in patients with COVID-19.

Molnupiravir, N4-Hydroxycytidine-5’-Triphosphate, 3-Deazauridine, COVID-16, Antiviral Therapy

Momparler, R. (2023) Commentary Potential Enhancement by 3-Deazauridine of the Antiviral Activity of Molnupiravir in Patients with COVID-19. Advances in Infectious Diseases, 13, 210-215. doi: 10.4236/aid.2023.132019.