However, available antibody therapies – often given intravenously in a hospital – are fundamentally less effective against Omicron than earlier variants of the virus, the researchers said.
Lab tests have also shown that some antibodies have completely lost their ability to neutralize Omicron at actual doses, they said.
“The bottom line is that we have countermeasures to treat Omicron. That’s good news,” said the study’s lead author. Yoshihiro Kawaokaare from University of Wisconsin-Madison United States.
“However, this is all in lab studies. Whether this translates to humans, we don’t know yet,” Kawaoka said.
The findings, published in the New England Journal of Medicine on Wednesday, corroborate other studies that have found most existing antibody treatments are less effective against Omicron.
Clinically available pills and antibodies were designed and tested before the researchers identified the Omicron variant, which is significantly different from previous versions of the virus.
When Omicron was identified, scientists were concerned that these differences, caused by mutations in the virus’s genome, could reduce the effectiveness of drugs designed to treat the original version of the virus.
In laboratory experiments using non-human primate cells, Kawaoka and colleagues at the National Institute of Infectious Diseases in Japan tested a suite of antibody therapies and antiviral resistance against the original COVID-19 virus strain and its prominent variants.
They found that Merck’s oral molnupiravir and intravenous drug Remdesivir were as effective against Omicron as against earlier strains of the virus.
Instead of testing PfizerThe Paxlovid pill, which is designed to be taken orally, the team tested a related drug from the company that is injected intravenously.
The two drugs disrupt the same part of the viral structure.
The researchers found that the intravenous form remained effective against Omicron, and the version is currently undergoing clinical trials.
All four antibody treatments the researchers tested were less effective against Omicron than previous strains of the virus.
Two methods of treatment, Sotrovimab via GlaxoSmithKline and AstraZeneca’s Evusheld, retains some virus-neutralizing abilities, according to the researchers.
However, they require 3 to 100 times more drug to neutralize Omicron than previous versions.
The study also showed that the two antibody treatments with Lilly and Regeneron could not neutralize Omicron at usual doses.
These findings are expected given how the Omicron variant differs from previous strains of the SARS-CoV-2 virus, the researchers say.
Omicron has dozens of mutations in the mutant protein that viruses use to enter and infect cells.
Most antibodies are designed to bind to and neutralize the original mutant protein, and large changes to the protein can make antibodies less likely to attach to it.
In contrast, the antiviral pills target the molecular machinery that the virus uses to make copies of itself inside the cell, the researchers said.
They add that the Omicron variant has only a few changes to this machinery, which makes it more likely that the drug retains its ability to disrupt this replication process.