The drugmaker said further analyzes are ongoing to confirm and quantify this potential impact using the actual Omicron variant sequence.
Regeneron’s shares were down 2.8 per cent at $636 before the bell.
Global markets fell on Tuesday following comments from Moderna Inc’s chief executive officer, who said COVID-19 vaccines are unlikely to be as effective against Omicron as they have been previously.
Regeneron said analysis shows the individual mutations present in Omicron indicate “there may be reduced neutralization activity of both vaccine-induced and monoclonal antibody conveyed immunity.”
The analysis included Regeneron’s COVID-19 antibody cocktail REGEN-COV, according to the company.
Rivals Eli Lilly and Co and Vir Biotechnology Inc, who have also developed COVID-19 antibody drugs, did not immediately respond to Reuters requests for comment.
The World Health Organization and scientists have said it could take weeks to understand whether Omicron is likely to cause severe illness or escape protection against immunity induced by vaccines.
Vaccine makers are already preparing for a situation where their current vaccines are less effective against the new variant, with several companies announcing on Monday that they had begun work on vaccines tailored for Omicron.
Sign up for the Coronavirus Update newsletter to read the day’s essential coronavirus news, features and explainers written by Globe reporters and editors.