Scientists have developed a new drug that can stop SARS-CoV-2, the virus that causes COVID-19, from infecting cells. And they did so by turning the virus's own great weapon against itself: its spike protein. This bit allows the virus to attach itself to cells and teaches our immune system to recognize it, and has been the focus of mRNA vaccine development. But now there is a new way to fight the virus.

In the final step to enter cells, SARS-CoV-2 uses the spike protein like a twist tie and forces the cell membrane to fuse with the virus. When this happens successfully, the virus's genetic material can get inside and then use the cell’s own machinery to make more copies of the virus.

An international team, led by Kailu Yang of Stanford University, developed a molecule based on the spike protein that can stick to the protein in a way that stops it from twisting. The molecule, called the longHR2_42 inhibitor, is a new approach to keeping the virus outside of our cells.

“In the virus, there's two parts of the spike protein that come together forming this bundle. So we simply took a short piece of one part of this bundle, and by synthesizing that small piece chemically, it can insert itself into the spike protein and prevent the virus from infecting cells,” senior author Axel Brunger from Stanford University said in a statement.

The importance of the spike protein was recognized from the beginning of the pandemic, and treatments and vaccination have often (but not exclusively) focused on that aspect of the virus. But the spike protein has changed with new variants of the virus, so preventative approaches and cures lose effectiveness as new variants spread.

This new drug affects a part of the spike protein that has not changed much from variant to variant, so the team believes that it could remain very effective against new variants. And, the team hopes to develop it as an inhaler, so people could take it at the earliest signs of infection to stop symptoms worsening.

“The moment people start developing sniffles will be the time to take it,” Brunger explained.

The work was published in the Proceedings of the National Academy of Sciences, and will be presented at the 67th Annual Biophysical Society Meeting in San Diego, California.