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Antibody therapy provides short-term protection for people exposed to COVID-19

Results from clinical trials partly conducted at U.Va. show the therapy is an important tool against COVID-19, especially for the immunocompromised


The School of Medicine was a main study site out of more than 100 locations across the world in 2020 that participated in phase three clinical trials for the COVID-19 antibody therapy REGEN-COV. Participants in the study were people who had been exposed to COVID-19 but hadn’t contracted the virus. 

Out of 2,000 study participants worldwide, 24 were at the University. Some included students whose roommates were sick. Results released on Nov. 8, 2021 indicate that REGEN-COV was shown to reduce risk of COVID-19 infection by 81.6 percent after eight months of study.

REGEN-COV is a monoclonal antibody cocktail developed by Regeneron Pharmaceuticals, and CEO Leonard Schleifer, a University alumnus. A monoclonal antibody cocktail is a mixture of two types of lab-made antibodies. 

Antibodies function beneficially by locking the virus out of human cells by binding to the spike glycoprotein of the virus, which is the means by which a virus infects human cells. A glycoprotein is a protein molecule containing a carbohydrate. A spike glycoprotein binds to a receptor on a human cell and fuses to the cell membrane, which encloses each human cell.  The virus’s genetic material can then enter the cell, which allows the virus to reproduce and the infection to spread throughout the body. 

In the body, antibodies are produced by white blood cells called B cells. In the lab, scientists can use sophisticated biotechnology to isolate DNA from the B cells that are most effective against the spike glycoprotein, place this DNA inside cells and grow them to produce new antibodies. 

Dr. William Petri Jr., , chief of the University’s Division of Infectious Diseases and International Health and the principal investigator of the REGEN-COV study, said an antibody cocktail is more effective than therapies with a single antibody. The two different antibodies in the cocktail have the benefit of being able to bind to different parts of the spike glycoprotein, thus making it more difficult for the virus to evade them.

The study concluded after eight months because half of the antibodies are cleared from the body every two to four weeks. The antibodies only provide protection when they are in the body and do not leave behind memory. As the number of antibodies available to fight a virus decreases, the effectiveness of the therapy also decreases. 

This was the first study of an antibody therapy against COVID-19 to even follow subjects out to eight months. Petri said he was “pleasantly surprised” by the results.

“I didn’t expect that there would be this much protection this far out,” Petri said.

Petri attributed the therapy’s long-lasting effectiveness to the large amount of antibodies administered. Four syringes, or 1.2 g of antibodies, were administered to each participant.

Petri, along with fourth-year Medicine student Rebecca Carpenter said that despite these hopeful results, antibody therapy isn’t a long-term solution for COVID-19 in the same way as vaccination. While the vaccine is an active immunization by helping the body produce its own antibodies, an antibody therapy is a passive immunization, as it introduces antibodies artificially.

However, this therapy can serve as a crucial substitute to the vaccine for people who are immunocompromised. The vaccine is meant to provoke the immune system’s natural antibody response, but for those with weakened immune systems, that natural response isn’t strong enough to make the vaccine effective.

“They’ve done everything right, but their immune system isn’t responding,” Petri said. 

He added that the  vaccine doesn’t give immunocompromised people the same sense of security.

Another goal of the therapy is to prevent household transmission -— to stop the spread of the virus in a nursing home, for example, or to allow people to care for a sick spouse or child without getting sick themselves.

Dr. Debbie-Ann Shirley, head of the U.Va. Division of Pediatric Infectious Disease and medical director of the University’s COVID-19 clinic,  was one of the investigators in the study.

“We still want to make sure that patients are being careful and taking all the precautions needed to prevent exposure to COVID or risk of transmission, but it's overall good news,” Shirley said of the study’s results.

REGEN-COV is one of three antibody therapies for COVID-19 currently authorized by the Food and Drug Administration for emergency use, and locations across the country are administering it, but only patients previously exposed to COVID-19 — as studied in this trial — are eligible. For immunocompromised people, Shirley indicated  receiving this protection before they are exposed could be vital to protect them from a higher risk of becoming dangerously ill in the first place.

Shirley said that next steps include getting the FDA to authorize the therapy for pre-exposure situations in order to help these immunocompromised patients. Regeneron is also applying for FDA approval of REGEN-COV.

The antibody cocktail has also been shown to neutralize the Delta variant. However, a recent statement from the National Institutes of Health COVID-19 Treatment Panel states that only one monoclonal antibody treatment — sotrovimab — has been active against the Omicron variant. This does not include the Regeneron antibody cocktail, which has been found to be not active against the Omicron variant. 

Omicron’s spike glycoprotein has been shown to contain numerous mutations, making it harder for antibodies to block infection. Regeneron is currently investigating new omicron-specific antibodies for use against COVID-19, Petri said. 

REGEN-COV is still an important new way to fight COVID-19.

“I had a rotation on the medical ICU and most of our patients had COVID,” Carpenter said. “It’s just really important that we have a number of different tools to be able to treat this.”

CORRECTION: This article previously stated that structural modeling and preliminary analyses of omicron mutations suggest that both the vaccine and monoclonal antibody therapies, including REGEN-COV, may be less effective against the omicron variant, according to a Nov. 30 press release from Regeneron. Since then, the Regeneron antibody cocktail has been found not to be active against the omicron variant, and the company is currently in the process of testing new antibodies that specifically work against the variant. The article has been updated to reflect this new information.


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