For months, doctors have relied on monoclonal antibody treatments to help keep patients at high risk for severe COVID-19 out of the hospital. But the rapid rise of the Omicron variant is making that tricky.
Data suggests that two common monoclonal antibody treatments—Eli Lilly’s bamlanivimab plus etesevimab and Regeneron’s REGEN-COV (casirivimab and imdevimab)—are not effective against the Omicron variant of COVID-19. However, preclinical findings have shown that GlaxoSmithKline’s Vir (sotrovimab) works well against Omicron in a lab setting.
“We are confident that sotrovimab will continue to provide significant benefit for the early treatment of patients hoping to avoid the most severe consequences of COVID-19,” George Scangos, Ph.D., chief executive officer of Vir, said in a statement.
Omicron is now the dominant strain of SARS-CoV-2, the virus that causes COVID-19, in the U.S.: It’s responsible for 73.2% of COVID-19 cases in the country, according to data from the Centers for Disease Control and Prevention (CDC).
Federal health officials plan to meet at the end of this week to discuss whether to pause shipments of the Eli Lilly and Regeneron monoclonal antibodies, based on how dominant Omicron becomes in certain areas, according to The New York Times, and some hospitals have already suspended their use.
It wouldn’t be the first time this has happened: Government officials stopped the rollout of bamlanivimab plus etesevimab in the summer after it was found to be ineffective against the dominant COVID-19 variants circulating at the time.
But why are some monoclonal antibody treatments effective against Omicron, while others aren’t? Infectious disease experts break it down.
What are monoclonal antibody treatments, again?
Monoclonal antibodies act in a similar way to the antibodies your body makes—these are just generated in a lab. This treatment works as “substitute antibodies that can restore, enhance, or mimic” the way your immune system tackles invading pathogens, the Food and Drug Administration (FDA) explains.
In the case of COVID-19, monoclonal antibodies can help your body block SARS-CoV-2 from latching onto your cells. That makes it harder for the virus to reproduce and make you sick, per the FDA. Monoclonal antibodies can also lessen the symptoms you experience or neutralize SARS-CoV-2.
Currently, there are three monoclonal antibody treatments authorized for use in the U.S. by the FDA:
- Eli Lilly’s bamlanivimab plus etesevimab
- Regeneron’s REGEN-COV (casirivimab and imdevimab)
- GlaxoSmithKline’s Vir (sotrovimab)
Why don’t some monoclonal antibody treatments work well against Omicron?
A lot of it comes down to the way that these monoclonal antibody treatments were designed, says Thomas Russo, M.D., professor and chief of infectious disease at the University at Buffalo in New York. “The Eli Lilly and Regeneron monoclonal antibody treatments are directed against the spike protein of SARS-CoV-2, and Omicron has 32 mutations and a deletion in the spike protein,” he says. “Because of this, those treatments no longer bind with the virus.”
As a result, “it is not expected that these products will have any meaningful effect on those with the Omicron variant,” says infectious disease expert Amesh A. Adalja, M.D., a senior scholar at the Johns Hopkins Center for Health Security.
But GlaxoSmithKline’s Vir is slightly different. The monoclonal antibody was originally identified from a 2003 survivor of SARS-CoV, and it targets a shared molecule in the spike protein between SARS-CoV and SARS-CoV-2, per the CDC. “The GlaxoSmithKline Vir monoclonal antibody targets an area of the spike protein that isn’t impacted by the mutations that the omicron variant has acquired,” Dr. Adalja says.
“The company felt that binding site was less likely to be altered [during mutations of the virus] and apparently they were right,” Dr. Russo says.
What should you do if you can’t access a more effective treatment?
This is a little tricky. If you qualify for monoclonal antibody treatment and you know that you have the Omicron variant of COVID-19, the Eli Lilly and Regeneron treatments are unlikely to do anything. In fact, it’s likely that they “are not even really going to be available anymore” very shortly, Dr. Adalja says, given that they’re not thought to be effective against Omicron.
But the reality is a little hazier, given that it can be difficult to know exactly which strain of COVID-19 you’re infected with. “There is some of the Delta variant still circulating,” Dr. Russo points out. “If someone is very vulnerable and high risk, and there’s a chance they could have Delta, doctors may give them the Eli Lilly or Regeneron treatments.”
“A lot depends on exactly where in the country you are and how much information the local doctors have about the local prevalence of Omicron vs. Delta,” says William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine. “In Tennessee, for example, cases are still mostly fueled by Delta but obviously Omicron is coming on strong.” He points out that his local monoclonal antibody center is still using Regeneron treatments as of now, although he expects that to change in the future.
What does this mean for the future of the pandemic?
Given the sudden uptick in demand, GlaxoSmithKline’s Vir is in short supply in hospitals across the country, Dr. Adalja says. “The supply of the GlaxoSmithKline Vir antibody must be greatly augmented,” he says. (GlaxoSmithKline has vowed to increase production ASAP.)
It’s also important to note, though, that antiviral pills from Pfizer and Merck that target COVID-19 are expected to be authorized by the FDA for use soon, even as early as this week. “If these pills come on the scene, they will compete with monoclonal antibodies in this very space and give more options,” Dr. Schaffner says.
Both medications can help prevent severe disease in people who are at high risk for COVID-19, with Pfizer’s Paxlovid having particularly strong data to support its use. (Research shows it reduces the risk of hospitalization or death by 89% when it is taken within three days of someone developing symptoms and 88% when it’s taken within five days.)
“We need the Pfizer antiviral as soon as possible,” Dr. Adalja says. Dr. Russo agrees. “As the virus evolves, we need to evolve as well with our treatments,” he says.
This article is accurate as of press time. However, as the COVID-19 pandemic rapidly evolves and the scientific community’s understanding of the novel coronavirus develops, some of the information may have changed since it was last updated. While we aim to keep all of our stories up to date, please visit online resources provided by the CDC, WHO, and your local public health department to stay informed on the latest news. Always talk to your doctor for professional medical advice.
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