According to new study results, an antibody combination from Regeneron reduces the risk of death from Covid-19 if it is administered to seriously ill patients who do not have their own antibody response.

A picture showing the drug REGN-COV

Regn-Cov2 consists of two monoclonal antibodies (casirivimab and imdevimab) that bind to the spike protein of Sars-CoV-2. It is evaluated as part of the independent study Randomized Evaluation of COVID-19 Therapy (Recovery) with 9785 hospitalized patients who were randomly allocated to normal care or normal care plus antibody therapy.

About a third of the patients included did not have their own antibody response to the virus. Results in a form medRxivconfirm that the drug reduced deaths by a fifth and hospital stay from 17 to 13 days in this group compared with usual treatment alone. Regn-Cov2 was of no benefit in patients with their own antibodies.

“It is good news that this is the first antiviral drug that works at a relatively late stage of disease,” says Stephen Evans of the London School of Hygiene & Tropical Medicine, UK. “But the advantages are not enormous. It reduced deaths from 30% to 24%. For a relatively small profit it could be a high price. ‘ Six fewer died out of 100 patients treated.

“We knew that early antibody therapy could stop the disease from progressing,” says Arturo Casadevall of Johns Hopkins University in Baltimore, USA. “The interesting thing is that they have identified a subset of people who will benefit from a delayed dose.” Antibodies are the body’s main antiviral defense mechanism, he adds. So if someone doesn’t make them, they are prone to serious illness.

“One of the challenges is making assays for these antibodies readily available,” said Richard Haynes, clinical coordinator of the recovery study at Oxford University. There are assays on the market, but they are not widely used.

Regeneron noted in its press release that Regn-Cov2 will retain its effectiveness against the major virus variants of concern in the United States. “Regen-Cov has full activity against the Delta variant, although some other variants reduce the activity of their parts,” notes Haynes. “Even if one antibody binds less well, the other still works, so the overall effectiveness is not diminished.”

Also earlier this week, AstraZeneca’s Covid Antibody Therapy (AZD7442) failed in a study aimed at preventing Covid-19 symptoms in unvaccinated people exposed to the virus. Meanwhile, Eli Lily continues to sell its Bamlanivimab / Etesevimab antibody cocktail under an emergency license in the United States. This applies to patients with mild to moderate Covid-19 who are at risk of developing a serious illness, but not to the seriously ill.

Regardless of this, CureVac’s mRNA vaccine candidate failed in a phase 2b / 3 study with a preliminary effectiveness of only 47% against Covid-19 of any severity. More than half of the cases among the study participants were worrying variants. “The multi-variant environment underscores the importance of developing next-generation vaccines as new virus variants keep emerging,” the company said in a press release.


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