What is Monoclonal Antibody Therapy? Eli Lilly Says Treatment Prevents COVID Infection

American pharmaceutical company Eli Lilly has said its monoclonal antibody therapy helped to prevent COVID-19 infections in a clinical trial.

But what does monoclonal antibody therapy involve?

Antibodies are proteins that the immune system produces to fight viruses, like SARS-CoV-2—which causes COVID-19. Monoclonal antibodies are produced in a lab but they function in much the same way as the ones found in the body naturally.

Therapies have now been developed that use the lab-made antibodies to treat people who have tested positive for COVID-19 and have mild to moderate symptoms.

To date, the Food and Drug Administration (FDA) has authorized two such treatments for emergency use: casirivimab and imdevimab given together, and bamlanivimab administered on its own.

These monoclonal antibodies target the "spike" protein of the SARS-CoV-2 virus, which it uses to bind to and enter human cells. By attaching to the spike protein, the antibodies block the entry of the virus into these cells.

The safety and effectiveness of therapy with bamlanivimab is still being investigated, but previous clinical trials have shown that it reduces COVID-19-related hospitalization or emergency room visits in patients who are at high-risk of the disease progressing.

But bamlanivimab is not authorized for the treatment of patients who are already hospitalized due to COVID-19 or require oxygen therapy as a result of the disease, according to the FDA.

The latest announcement from Eli Lilly refers to a study the firm conducted examining the bamlanivimab therapy that it was responsible for developing.

In the Phase III trial, the company said bamlanivimab "significantly reduced" the risk of contracting symptomatic COVID-19 among residents and staff of long-term care facilities. This is the first time that a monoclonal antibody therapy has been shown to prevent COVID-19 infection rather than simply treat the disease.

Lilly released a statement on Thursday detailing the results of the study, although the company has yet to publish them in a peer-reviewed clinical journal. The firm said it plans to submit the results of the trial, which was overseen by an independent data and safety monitoring board, to a journal soon.

"We are exceptionally pleased with these positive results, which showed bamlanivimab was able to help prevent COVID-19, substantially reducing symptomatic disease among nursing home residents, some of the most vulnerable members of our society," Daniel Skovronsky, Lilly's chief scientific officer and president of Lilly Research Laboratories, said in a statement.

"These data provide important additional clinical evidence regarding the use of bamlanivimab to fight COVID-19 and strengthen our conviction that monoclonal antibodies such as bamlanivimab can play a critical role in turning the tide of this pandemic."

Skovronsky said the firm looked forward to discussing with regulators the expansion of bamlanivimab's emergency use authorization, so that the treatment can be used to prevent the spread of COVID-19 in nursing homes.

For the study, which was conducted in partnership with the National Institute of Allergy and Infectious Diseases, Lilly enrolled 1,097 participants working and living in nursing homes. At the beginning of the study, 132 of these individuals tested positive for SARS-CoV-2—including 41 residents and 91 staff.

Of the 965 participants who had tested negative for the virus at the start of the study, 299 were residents and 666 were staff.

All of the participants were randomized to receive either 4,200 milligrams of bamlanivimab intravenously—six times higher than the previously authorized dose—or a placebo.

After eight weeks, researchers found that there was a significantly lower frequency of symptomatic COVID-19 in the people who had received bamlanivimab compared to those who were given a placebo.

In addition, Eli Lilly said individuals among the 299 nursing home residents who tested negative at the start of the study and received bamlanivimab had an 80 percent lower risk of contracting COVID-19 versus the residents who were given a placebo.

Over the course of the study, four people among these 299 residents died due to COVID—all of whom were in the placebo group. Of the 41 residents who tested positive for COVID-19 at the start of the study, there were also four deaths—again, all in the placebo group.

Myron Cohen, co-principal investigator of the study and director of the Institute for Global Health and Infectious Diseases at the University of North Carolina at Chapel Hill, said in a statement: "The antiviral activity seen with bamlanivimab treatment emphasizes the importance of early intervention to help counter the devastating impact the virus has had in this vulnerable population and other high-risk patients."

Skovronsky told STAT the treatment should not be seen as an alternative to vaccines, which are "more effective" and likely provide "longer lasting" protection.

"It should be for when it's too late, when there's an outbreak and people are getting exposed and there's not going to be time for a vaccine to work," he said.