The discovery of a small molecule that neutralises the SARS-CoV-2 virus, which causes COVID-19, could provide a new basis for medication to shorten the course of the virus after exposure to it, according to a new study.

Researchers from the University of Houston (UH), US, said that the molecule could provide immediate protection against viral infection and thus, may be suitable for people across age groups, particularly for high-risk and immunocompromised individuals who typically do not generate sufficient antibodies after vaccination.

The molecule worked unlike Pfizer's antiviral treatment Paxlovid, which, they said, was only useful during the first three days of showing symptoms.

The discovery is described in the journal Biomedicines.

The molecule's discovery began at the height of the pandemic, according to the study, as the team of scientists screened 15,09,984 feature-rich compounds in the UH Research Computing Data Core.

"Our team is thrilled with the discovery of a small molecule therapeutic that inhibits the interaction between the spike protein of the COVID-19 virus and the ACE2 receptor of the infected individual," said Bradley McConnell, professor at the University of Houston College of Pharmacy and in whose lab the discovery took place.

In the experimentation phase, the team selected the top 15 molecules that disrupted the interaction between the spike protein and the ACE2 receptor.

Using molecular dynamic simulations, they found favourable interactions between some of the compounds from the libraries and the spike protein's ACE receptor binding domain interface, potentially neutralising the SARS-CoV-2 infection.

The molecule that formed the closest association was CD04872SC, the study said.

"We were able to experimentally observe that CD04872SC also inhibited the infection of the SARS-CoV-2 variants Delta and Omicron," said Reyes-Alcaraz, the study's first author.

"To demonstrate the binding between CD04872SC and the spike proteins of each variant, we performed a thermal shift assay which measures changes in the thermal denaturation temperature, serving as an indicator of the stability of a protein under varying conditions such as when bound by a drug, pH, ionic strength, or sequence mutation," said Craft, associate professor in the Department of Biology and Biochemistry.

The SARS-CoV-2 virus and its variants Delta and Omicron continue to be a major threat to patients of all ages.

The variants demonstrate how easily the virus can accommodate antigenic changes in its spike protein without the loss of fitness.

"The Omicron variant has particularly stressed health care systems around the world. Therefore, identifying effective antiviral agents to combat this infectious disease is urgently needed," said McConnell.

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