The smallest known biological molecule that neutralizes SARS-CoV-2 has been isolated to produce a drug that might be "highly effective in preventing and treating" the virus that causes COVID-19.

Scientists from the University of Pittsburgh School of Medicine reported this in a study published in the peer-reviewed journal Cell. University researchers reported they had developed a drug called "Ab8" for potential use as a therapeutic and prophylactic against SARS-CoV-2. They found Ab8 "highly effective" in preventing and treating SARS-CoV-2 in mice and hamsters.

The size of the molecule increases its potential for diffusion in tissue to better neutralize SARS-CoV-2. Its tiny size might allow Ab8 to be given as an inhaled drug or intradermally instead of intravenously through an IV drip - like most monoclonal antibodies in development.

It also makes it possible to administer the drug by alternative routes such as inhalation. An advantage is the biomolecule doesn't bind to human cells - which is a good sign it won't have negative side-effects.

"Ab8 not only has potential as therapy for COVID-19 but it might be used to keep people from getting SARS-CoV-2 infections," study joint author and chief of the Division of Infectious Diseases at the university and its medical school Dr. John Mellors said.

Another joint author and university faculty member Xianglei Liu said antibodies of larger sizes had worked against other infectious diseases and were well tolerated. This knowledge gives the university's researchers hope Ab8 might be an effective treatment for COVID-19 patients and for protection of those who have never had the infection but aren't immune.

Ab8 was also evaluated by scientists from the University of Texas Medical Branch at Galveston, the University of North Carolina at Chapel Hill, the University of British Columbia and the University of Saskatchewan.

Tests found that at very low concentrations Ab8 completely blocked SARS-CoV-2 from entering cells. Ab8 was then tested at varying concentrations in mice using a modified version of SARS-CoV-2.

The study said even at the lowest dose Ab8 decreased by tenfold the amount of iSARS-CoV-2 in mice compared with their untreated counterparts. Ab8 was also effective in treating and preventing SARS-CoV-2 in hamsters.

Abound Bio, a new company backed by UPMC, has licensed Ab8 for worldwide development.