The data from early-stage studies, which has yet to be peer reviewed, shows that their treatment, called sotrovimab, is effective against all mutations in the spike protein of Omicron. Most of Omicron’s 37 mutations—the highest number in any variant to date—are concentrated on the spike protein, the part of the virus that binds to cells in our bodies.

The preclinical data demonstrates “the potential” of the monoclonal antibody’s effectiveness against the latest variant as well as all other variants of concern defined to date by the WHO, GSK chief scientific officer Hal Barron said in a statement.

Sotrovimab is an investigational SARS-CoV-2 neutralizing monoclonal antibody, or a clone of white blood cells from COVID-19 survivors or mice, which latches onto the spike protein on the surface of the coronavirus and prevents it from replicating in new cells. The treatment is given intravenously and is designed to linger in the lungs to fight the coronavirus as it enters the body.

As part of the study, GSK and Vir have been “pseudo-virus testing,” or engineering and testing any major coronavirus mutations that have emerged thus far against its sotrovimab treatment.

Most pharmaceutical companies have been working on their own monoclonal antibody or antiviral pill treatments and rushing to test how they fare against the new Omicron variant, which is proving to be highly contagious but mild in symptoms. Here are the others:

Regeneron Pharmaceuticals

Preliminary testing of U.S. drugmaker Regeneron Pharmaceuticals’ monoclonal antibody drug has shown it loses effectiveness against Omicron, the company said last week. At the time of the announcement, Regeneron said it would quantify the impact of the variant after further in vitro testing is performed in the coming weeks.

Regeneron’s drug, named REGEN-COV, was first authorized by the FDA in July 2021 after a study published in April of that year found that the drug reduced the risk of symptomatic infection by 81%. In October of last year, former U.S. President Donald Trump endorsed Regeneron’s antibody drug, crediting it with his fast recovery from COVID-19.

Eli Lilly & Co.

Regeneron rival Eli Lilly’s drug cocktail also isn’t as effective against Omicron, outside scientists found.

Eli Lilly has two monoclonal antibody drugs, bamlanivimab and etesevimab, the combination of which once offered a 70% reduced risk of hospitalization and death, according to its February study. The drug combo proved to be effective against the Delta variant and was reauthorized by the FDA in September 2021.

Both Regeneron’s and Lilly’s drugs fall short because individual mutations from Omicron reduced or eliminated the ability of each to attach to the virus, Allie Greaney, a Ph.D. candidate at Seattle’s Fred Hutchinson Cancer Research Center and the University of Washington, told the Wall Street Journal.

Adagio Therapeutics

Like GSK and Vir, U.S. biotech company Adagio Therapeutics found its COVID-19 antibody drug, called ADG20, was unaffected by the new variant and is currently doing further testing to confirm its resilience.

ADG20 was designed “to combine breadth, potency, and duration of protection” for up to a year after a single injection, said Tillman Gerngross, cofounder and chief executive officer of Adagio, who noted the treatment was designed as the company anticipated COVID-19 would evolve and “potentially render some early therapies and vaccines obsolete.”

Both Adagio and Vir officials have said the antibody treatments were designed to target spots on the virus that remained stable across multiple mutations.  

Gilead Sciences

Scientists have also been creating antiviral pills, which suppress the virus’s ability to infect and multiply in human cells by inhibiting the molecular interactions needed by the virus to produce copies of itself. A big advantage for the antiviral pill is that it can be taken orally, as opposed to intravenously.

Only one drug has been granted full approval by the FDA—remdesivir, made by Gilead Sciences under the brand name Veklury.

Gilead said last week that preliminary testing showed remdesivir would remain effective against the Omicron variant, and that it will continue laboratory testing to confirm this result.

However, remdesivir’s effectivity is still up for discussion. The drug was first approved by the FDA in October 2020 after it was part of the cocktail of drugs used to treat former President Trump. But since then, some experts have expressed skepticism over its benefits, and the WHO has issued guidelines against its use.

Pfizer

Pfizer CEO Albert Bourla told CNBC this week that he has a “very high level of confidence” that Pfizer’s antiviral pill “will not be affected by this [Omicron] virus.”

The pill, called Paxlovid, is currently under review by the FDA for emergency approval but showed signs it reduced deaths and hospitalizations by 89% in clinical trials.

Merck

Merck said it expects its antiviral pill, developed in partnership with U.S. biotech firm Ridgeback Biotherapeutics, will perform effectively against Omicron.

The drug, called molnupiravir, has been shown to reduce the risk of deaths and hospitalizations by 30% and is also under review by the FDA for approval.

The antiviral drugs produced by Merck and Pfizer appear to be unaffected by the new variant because they target a different site on the virus, Michel Nussenzweig, an immunologist at Rockefeller University, told the Wall Street Journal.