Synthesis of ribavirin 2'-Me-C-nucleoside analogues

Developments in the chemistry and biology of 1,2,3-triazolyl-C-nucleosides

In the last 50 years, nucleoside analogs have been introduced to drug therapy as antivirals for different types of cancer due to their interference in cellular proliferation. Among the first line of nucleoside treatment drugs, ribavirin (RBV) is a synthetic N-nucleoside with a 1,2,4-triazole moiety that acts as a broad-spectrum antiviral. It is on the World Health Organization (WHO) list of essential medicines. However, this important drug therapy causes several side effects due to its nonspecific mechanism of action. There is thus a need for a continuous study of its scaffold. A particular approach consists of connecting  d-ribose to the nitrogen-containing base with a C-C bond. It provides more stability against enzymatic action and a better pharmacologic profile. The coronavirus disease (COVID) pandemic has increased the need for more solutions for the treatment of viral infections. Among these solutions, remdesivir, the first C-nucleoside, has been approved by the Food and Drug Administration (FDA) for clinical use against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It drew attention to the study of the C-nucleoside scaffold. Different C-nucleoside patterns have been synthesized over the years. They show many important activities against viruses and cancer cell lines. 1,2,3-Triazolyl-C-nucleoside derivatives are a prolific and efficient subclass of RBV analogs close to the already-known RBV with a C-C bond modification. These compounds are often prepared by alkynylation of the  d-ribose ring followed by azide-alkyne cycloaddition. They are reported to be active against the Crimean-Congo hemorrhagic fever virus and several tumoral cell lines, showing promising biological potential. In this review, we explore such approaches to 1,2,3-triazolyl-C-nucleosides and their evolution over the years.

New triazole-substituted triterpene derivatives exhibiting anti-RSV activity: synthesis, biological evaluation, and molecular modeling

Respiratory syncytial virus (RSV) is a major cause of acute lower respiratory tract infections in infants. Currently, ribavirin, a nucleoside analog containing a 1,2,4-triazole-3-carboxamide moiety, is a first-line drug for its treatment, however, its clinical use has been limited due to its side effects. Here, we designed two new nitroaryl-1,2,3-triazole triterpene derivatives as novel anti-RSV drugs. Their anti-RSV and cytotoxic activity were evaluated in vitro, RSV protein F gene effects by RT-PCR and molecular modeling with inosine monophosphate dehydrogenase (IMPDH) were performed. Compound 8 was the best performing compound, with an EC50 value of 0.053 μM, a TI of 11160.37 and it inhibited hRSV protein F gene expression by approximately 65%. Molecular docking showed a top-ranked solution located in the same region occupied by crystallographic ligands in their complex with IMPDH. The results obtained in this study suggest that compound 8 might be a new anti-RSV candidate.

Studies on the synthesis of 1'-CN-triazolyl-C-ribosides

The search for broad-spectrum antiviral compounds is a continuous mandatory effort. The recent approval of the first C-nucleoside carrying a nitrile as a substituent at the C1' position of the ribose ring has raised interest in this underexplored substitution pattern. We have previously reported the development of different 1,2,3-triazolyl-C-ribonucleosides with anticancer and antiviral activities. Herein we report our results on the incorporation of a C1'-CN group in 1,2,3-triazolyl-C-ribonucleosides.

Anti-HCV and Zika activities of ribavirin C-nucleosides analogues

Ribavirin is an unnatural nucleoside exhibiting broad spectrum of antiviral and antitumor activities, still very widely studied particularly in a repositioning approach. C-triazolyl nucleoside analogues of ribavirin have been synthesized, as well as prodrugs and glycosylated or peptide conjugates to allow a better activity by vectorization into the liver or by facilitating uptake into the cells. The antiviral properties of all synthesized compounds have been evaluated in vitro against two important human viral pathogens belonging to the Flaviviridae family: hepatitis C virus (HCV) and Zika virus (ZIKV). There are no therapeutic options for Zika virus, whereas those available for HCV can be still improved. Our results indicated that compound 2 carrying an N-hydroxy carboxamide function exhibits the most inhibitory activities against both viruses. This compound moderately inhibited the propagation of HCV with an IC₅₀ value of 49.1 μM and Zika virus with an IC₅₀ of 33.2 μM comparable to ribavirin in the Vero cell line. The results suggest that compound 2 and its new derivatives may be candidates for further development of new anti-HCV and anti-ZIKV antiviral drugs.

Synthesis and antitumor activities investigation of a C-nucleoside analogue of ribavirin

SRO-91 is a non-natural ribofuranosyl-1,2,3-triazole C-nucleoside obtained by a synthetic sequence involving a C-alkynyl glycosylation mediated by metallic indium and a Huisgen cycloaddition for the construction of the triazole. Its structure is close to the one of ribavirin, a drug presenting a broad-spectrum against viral infections. SRO-91 antitumor activities were investigated on 9 strains of tumor cells and IC₅₀ of the order of 1 μM were obtained on A431 epidermoid carcinoma cells and B16F10 skin melanoma cells. In addition, studies of ovarian tumor cell inhibitions show an interesting activity in regard to the need for new drugs for this pathology. Finally, cytotoxicity and mouse toxicity studies reveal a favorable therapeutic index for SRO-91.

Evaluation of the potential of a new ribavirin analog impairing the dissemination of ovarian cancer cells

Epithelial ovarian cancers are insidious pathologies that give a poor prognosis due to their late discovery and the increasing emergence of chemoresistance. Development of small pharmacological anticancer molecules remains a major challenge. Ribavirin, usually used in the treatment of hepatitis C virus infections and more recently few cancers, has been a suggestion. However, Ribavirin has many side-effects, suggesting that the synthesis of analogs might be more appropriate. We have investigated the effect of a Ribavirin analog, SRO-91, on cancer cell behavioral characteristics considered as some of the hallmarks of cancer. Two human ovarian adenocarcinoma cell lines (SKOV3 and IGROV1) and normal cells (mesothelial and fibroblasts) have been used to compare the effects of SRO-91 with those of Ribavirin on cell behavior underlying tumor cell dissemination. SRO-91, like Ribavirin, inhibits proliferation, migration, clonogenicity and spheroids formation of cancer cells. Unlike Ribavirin, SRO-91 is preferentially toxic to cancer compared with normal cells. An in vitro physiologically relevant model showed that SRO-91, like Ribavirin or cisplatin, inhibits cancer cell implantation onto peritoneal mesothelium. In conclusion, SRO-91 analog effects on tumor dissemination and its safety regarding non-cancerous (normal) cells are encouraging findings a promising drug for the treatment of ovarian cancer.