It was the last monoclonal antibody treatment standing. But less than 10 months after the U.S. Food and Drug Administration gave bebtelovimab its emergency use authorization (EUA) to fight COVID-19, it earlier this month de-authorized it, just as it had for other monoclonal antibody treatments, and for the same reason:
Bebtelovimab couldn’t neutralize the Omicron subvariants BQ.1 and BQ.1.1, the cause of nearly 60% of COVID cases nationally as of November 30.
Next on the chopping block, some predict, will be Evusheld, the combination of tixagevimab and cilgavimab given as a preventive monoclonal antibody to people who are immunocompromised and at high risk of contracting COVID and to those who can’t take the vaccine. In October, the FDA warned that Evusheld was not neutralizing circulating COVID variants.
As the options for treating and preventing COVID decline, will companies rally quickly to develop new ones, or cut their losses in developing treatments that may work for only a few months, given the speed of viral mutations?
But although monoclonal antibody treatments are off the table, at least for now, antiviral drugs – including Paxlovid – are still very much available, and some say underused.
Others suggest it’s time to resurrect interest in convalescent plasma, a treatment used early in the pandemic before drugs or vaccines were here and still authorized for use in those who are immunosuppressed or receiving immunosuppressive treatment.
And on the prevention front, staying up to date with booster vaccines, masking, and taking other precautions should be stressed more, others say, regardless of the number of treatment options, and especially now, as cases rise and people gather for the winter holidays.
‘A major setback’
The bebtelovimab de-authorization was “a major setback,” but an understandable one, said Arturo Casadevall, MD, PhD, professor and chair of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health in Baltimore. “Monoclonal antibodies are great drugs. We are in an unfortunate situation in that they are vulnerable to changes in the virus” and can’t offer long-lasting protection.
Supplies of bebtelovimab will be retained, according to the FDA, in case variants susceptible to it return.
“What happened to bebtelovimab is no surprise,” agreed Amesh Adalja, MD, senior scholar at Johns Hopkins Center for Health Security. “This is what is going to happen when you are targeting a virus that mutates a lot.”
Monoclonal antibodies work by binding to the spike protein on the virus surface to prevent it from entering cells.
However, Dr. Adalja doesn’t view the disappearance of monoclonal antibody treatments as a major setback. Monoclonal antibodies were not the primary way COVID was treated, he said.
While he does believe it’s important that more monoclonal antibody treatments be developed, “I think it’s important to remember we still have Paxlovid while everyone is lamenting the loss of bebtelovimab.’’
Antivirals: What’s here, what’s coming
Compared with monoclonal antibodies, “Paxlovid remains a much easier drug to give,” Dr. Adalja told this news organization, because it is taken orally, not intravenously.
And it’s effective. In a recent study, researchers found that adults diagnosed with COVID given Paxlovid within 5 days of diagnosis had a 51% lower hospitalization rate within the next 30 days than those not given it. Another study shows it could also reduce a person’s risk of developing long COVID by 26%.
Paxlovid is underused, Dr. Adalja said, partly because the rebound potential got more press than the effectiveness. When a celebrity got rebound from Paxlovid, he said, that would make the news, overshadowing the research on its effectiveness.
Besides Paxlovid, the antivirals remdesivir (Veklury), given intravenously for 3 days, and molnupiravir (Lagevrio), taken orally, are also still available. Antivirals work by targeting specific parts of the virus to prevent it from multiplying.
In the lab, remdesivir, molnupiravir, and another antiviral, nirmatrelvir, all appear to be effective against both BQ.1.1 (a BA.5 subvariant) and XBB (a BA.2 subvariant), both rapidly rising in the United States, according to a report last week in the New England Journal of Medicine.
The researchers also tested several monoclonal antibodies and found they did not neutralize either of the subvariants BQ.1.1 and XBB.
A new oral antiviral, Xocova (ensitrelvir fumaric acid), from Japanese manufacturer Shionogi, received emergency approval in Japan on November 22. It’s taken once a day for 5 days. The goal is to expand access to it globally, according to the company.
Pardes Biosciences launched a phase 2 trial in September for its oral antiviral drug (PBI-0451), under study as a treatment and preventive for COVID. It expects data by the first quarter of 2023.
Pfizer, which makes Paxlovid, has partnered with Clear Creek Bio to develop another oral antiviral COVID drug.
Other approaches
A receptor protein known as ACE2 (angiotensin-converting enzyme 2) is the main “doorway” that SARS-CoV-2 uses to enter and infect cells.
Dana-Farber Cancer Institute scientists are developing a “decoy” drug that works by mimicking the ACE2 receptor on the surface of cells; when the virus tries to bind to it, the spike protein is destroyed. Human trials have not yet started.
Other researchers are investigating whether an already-approved drug used to treat a liver disease, Actigall (UDCA/ursodeoxycholic acid), could protect against COVID infection by reducing ACE2.
So far, the researchers have found in early research that people taking UDCA for liver conditions were less likely than those not taking the drug to have severe COVID. They also found that UDCA reduced SARS-CoV-2 infection in human lungs maintained outside the body.
Monoclonal antibody treatments?
After the FDA decision to withdraw the bebtelovimab EUA, which Eli Lilly said it agreed with, the company issued a statement, promising it wasn’t giving up on monoclonal antibody treatments.
“Lilly will continue to search and evaluate monoclonal antibodies to identify potential candidates for clinical development against new variants,” it read in part.
AstraZeneca, which makes Evusheld, is also continuing to work on monoclonal antibody development. According to a spokesperson, “We are also developing a new long-acting antibody combination – AZD5156 – which has been shown in the lab to neutralize emerging new variants and all known variants to date. We are working to accelerate the development of AZD5156 to make it available at the end of 2023.”
The AstraZeneca spokesperson said he could share no more information about what the combination would include.