"Nature": After screening 18,000 drugs, anti-coronavirus therapy has finally been found

According to the latest statistics from the World Health Organization (WHO), as of February 8, 2022, the total number of global SARS-CoV-2 infections has approached 400 million, including more than 5.
74 million death cases
.

Among them, the cumulative number of confirmed cases in the United States ranks first, with a total of about 75.
89 million; India is second with about 42.
34 million
.

Although over the past two years, all countries have been working hard on the development of vaccines, but in the context of the continuous update and iteration of new crown variants, the lack of effective antiviral therapy is a great threat and loophole in this process
.

Figure 1.
WHO Coronavirus Dashboard (Source: WHO)[1] On February 7, 2021, the journal Nature published an article on anti-coronavirus drugs online in the form of "Accelerated Article Preview" The latest paper "Pyrimidine inhibitors synergize with nucleoside analogues to block SARS-CoV-2"
.

In this study, the researchers used human respiratory epithelial cells (respiratory epithelial cells) for live virus infection, screened about 18,000 different drugs with antiviral activity, and identified 122 that showed good antiviral activity against the new coronavirus.
Active and selective drug candidates, including a subset of nucleoside analogs approved for the treatment of COVID-19
.

In addition, the study also discovered a novel and highly effective "combination therapy" that combines pyrimidine biosynthesis inhibitors with antiviral nucleoside analogs to "synergistically" inhibit infection by SARS-CoV-2 strains in vitro and in vivo situation
.

Figure 2.
Pyrimidine inhibitors synergize with nucleoside analogues to block SARS-CoV-2 (Source: Nature) [2] SARS-CoV-2 is a single-stranded RNA virus that uses virally encoded RNA-dependent RNA polymerase (RNA -dependent RNA polymerase, RdRp) for RNA replication
.

Nucleoside analogs can interfere with this step - once "incorporated" into the growing viral RNA strand by RdRp, the RNA replication process is forced to terminate or mutate due to the presence of the nucleoside analog.
The replication of the virus is thus affected and inhibited
.

At present, nucleoside analogs have become a large class of approved drugs that can be directly used as antivirals
.

Since the structure of RdRp is relatively conserved in different viruses, the researchers believe that some existing nucleoside analogs may also have inhibitory effects on the new coronavirus
.

Human respiratory epithelial cells are the primary cellular target of SARS-CoV-2 in vivo
.

In order to quickly find potentially effective drugs, the scientists conducted a screening of a small molecule compound library using the human respiratory epithelial cell line Calu-3
.

The compound library includes approximately 18,000 drugs, most of which have been tested in humans: including approved drugs, drugs in clinical trials, and drugs with known targets with antiviral activity
.

The researchers used the original new coronavirus (WA1) to infect cells after pretreatment of Calu-3 with the above-mentioned drugs
.

After 48 hours, the severity of infection was quantitatively assessed using antibodies against dsRNA
.

After a comprehensive evaluation of the inhibitory ability and toxicity of the new coronavirus, 122 compound molecules stood out from nearly 20,000 "entrants"
.

They belong to different types, of which about 13% are nucleoside analogs, including anti-new coronavirus drugs that have been approved by many regulatory agencies around the world - remdesivir and molnupiravir
.

Figure 3.
From ~18,000 compounds, 122 show activity.
(Source: Nature) As mentioned earlier, during DNA or RNA replication, nucleoside analogs can play the role of "synthetic analogs" by cellular polymerases.
Actions slip into DNA or RNA to inhibit cell division; but in addition, they act as an antimetabolite by inhibiting nucleoside biosynthetic enzymes to deplete deoxynucleotides and nucleotides required for replication supply, so as to achieve the purpose of inhibiting nucleoside synthesis
.

The advantage of this approach is that the molecules are not toxic to the cells they act on at concentrations that can exert antiviral efficacy
.

Nucleoside analogs with functions to inhibit nucleoside synthesis were discovered through a previous large-scale screen.
To determine the breadth of antiviral activity of these nucleoside analogs, the researchers tested a panel of cell lines that allowed infection with SARS-CoV-2.
tested
.

It was found that different molecules exhibit their own cell-specific activity and toxicity: for example, tubercidin in Calu-3, Caco-2 (human intestinal epithelial cell line) and Huh7.
5 (human liver cell line) Has shown antiviral activity and was toxic in A549-Ace2 (human respiratory cell line) and Vero cell line (African green monkey kidney cells); in contrast, thioguanine and 6-Mercaptopurine were Active in Calu-3 and A549-Ace2 cell lines, but not in Caco-2 or Vero cell lines
.

The final results of RT-qPCR showed that remdesivir and monoprevir showed the best antiviral activity
.

Figure 4.
Simplified schematic of nucleoside metabolism.
(Source: Nature) This finding has important implications, because both are nucleoside analogs, but remdesivir and monoprevir are different nucleoside derivatives, the former being adenosine glycoside analogs, and the latter are cytosine analogs
.

Therefore, the researchers believe that, depending on the pathway of action, the antiviral synergistic effect of "one plus one is greater than two" may be exerted by means of a pairwise combination
.

As shown in the figure above, the biosynthesis of pyrimidine requires the participation of DHODH and UMPS
.

By monitoring the treated nucleoside pool, the researchers found that the combination of a DHODH inhibitor (BAY-2402234 and Brequinar)/UMPS inhibitor (pyrazofurin) with remdesivir/monoprevir could work surprisingly well On the contrary, if the combination of remdesivir and monoprevir is only used, although it can also show a good therapeutic effect, it is only a simple cumulative effect
.

In the follow-up, the researchers also tested different new crown variants, and it was clear that this "combination" antiviral therapy can show good efficacy in different variants
.

This result will undoubtedly bring a new idea of ​​new drug development for the clinical treatment of new crown infection
.

Reference:[1]World Health Organization: WHO Coronavirus (COVID-19) Dashboardhttps://covid19.
who.
int/[2]Nature: Pyrimidine inhibitors synergize with nucleoside analogues to block SARS-CoV-2.
https://doi .
org/10.
1038/s41586-022-04482-x Author | Xu Chuchu Disclaimer This article reprinted by "Yaodu" comes from the public account: Bio Valley, the main purpose is to share industry-related knowledge and transmit the latest information
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