Trending Clinical Topic: Antibodies

Ryan Syrek

Disclosures

June 11, 2021

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From a new tool to fight against COVID-19 disease progression in high-risk patients to studies examining vaccine longevity and efficacy, news about antibodies resulted in this week's top trending clinical topic.

The monoclonal antibody drug sotrovimab has been granted emergency use authorization by the US Food and Drug Administration (FDA) — in patients who are not hospitalized for COVID-19 and who do not require oxygen therapy — after a study showed that it was effective in protecting against disease progression in high-risk patients (see Infographic below). An interim report posted in advance of peer review showed that three of 291 patients (1%) in the sotrovimab group were hospitalized, compared with 21 of 292 patients (7%) in the placebo group. All five patients who needed to be admitted to the intensive care unit received placebo, according to the findings. The European Union's drug regulator has backed the use of sotrovimab for patients at risk for severe COVID-19 who do not need supplemental oxygen.

Antibody drugs and COVID-19 vaccines have both been shown to be less effective against the Delta variant (B.1.617.2), which was first detected in India. According to a report posted on bioRxiv ahead of peer review, antibodies in blood from unvaccinated COVID-19 survivors and from people who received two doses of the Pfizer/BioNTech vaccine were threefold to sixfold less potent against the Delta variant than against the Alpha variant (B.1.1.7), which was first identified in the United Kingdom, and the Beta variant (B.1.351), which was first identified in South Africa.

Predicting vaccine efficacy against viral variants may be possible using neutralizing antibodies, according to new research. A study published in Nature Medicine analyzed the relationship between in vitro neutralizing antibody levels and protection against severe COVID-19. Researchers estimated that the neutralization level needed for 50% protection against detectable coronavirus infection was 20.2% of the mean convalescent level; however, the level needed for 50% protection against severe infection was only 3% of the mean convalescent level. A significant loss of protection was indicated by modeling of the neutralization titer decay over the first 250 days after vaccine administration; however, the model indicated that severe disease protection is likely to be mostly retained. Compared with the vaccine strain, neutralization titers against some variants of concern were reduced, and the model was able to predict the relationship between efficacy against viral variants and neutralization.

Encouragingly, the duration of protection against COVID-19 after vaccination or infection may be as long as a year, and possibly longer, according to two new studies. A study published in Nature found that certain immune cells may survive in the bone marrow of people who were infected with coronavirus and later vaccinated. Those immune cells may create antibodies whenever needed. A separate study posted on bioRxiv found that these memory B cells can grow and strengthen for at least 12 months after initial infection.

When assessing immunity to or protection from COVID-19, the FDA recently came out against antibody testing for SARS-CoV-2. More a reminder than a new policy, the FDA recommended against using antibody test results for these indications in a recent Safety Communication. "The FDA is reminding the public of the limitations of COVID-19 antibody, or serology, testing and providing additional recommendations about the use of antibody tests in people who received a COVID-19 vaccination," Tim Stenzel, MD, PhD, director of the Office of In Vitro Diagnostics and Radiological Health in the FDA's Center for Devices and Radiological Health, said in a statement.

From drugs used to prevent COVID-19 disease progression to concerns about vaccine efficacy and duration, various news about antibodies resulted in this week's top trending clinical topic.

Read more about investigational drugs and other therapies for COVID-19.

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