FDA authorizes bamlanivimab and etesevimab monoclonal antibody therapy for post-exposure prophylaxis (prevention) for COVID-19

A monoclonal antibody is a laboratory-made protein created by cloning a unique white blood cell that functions like antibodies made by the immune system in response to infection. All subsequent antibodies derived this way trace back to a unique parent cell. Monoclonal antibodies can have monovalent affinity, binding only to the same epitope. By binding to a specific molecule on an antigen these antibodies can help to enhance or restore the immune responses against pathogens. Monoclonal antibody therapy is typically given through intravenous (IV) infusion therapy but can also be administered via injection. Timing is most important with this therapy, the earlier they are administered the more effective they are at treating and prevention, being most effective within the first 4-5 days of symptoms. Infusions generally require about an hour to administer, which is followed by an hour of observation and monitoring, for most people. 

The U.S. Food and Drug Administration has just released a news briefing detailing the agency’s revision of the emergency use authorization (EUA) for bamlanivimab and etesevimab, administered together, to include emergency use as post-exposure prophylaxis (prevention) for COVID-19 in adults and pediatric patients (12 years of age and older weighing at least 40 kg) who are at high risk for progression to severe COVID-19, including hospitalization or death. Bamlanivimab and etesevimab are monoclonal antibodies. Monoclonal antibodies are laboratory-made proteins that mimic the immune system’s ability to fight off harmful pathogens, such as viruses like SARS-CoV-2.

In this revision of the EUA, bamlanivimab and etesevimab, administered together, are authorized for use after exposure to the virus and are not authorized for pre-exposure prophylaxis to prevent COVID-19 before being exposed to the SARS-CoV-2 virus. Health care providers should review the fact sheet for detailed information about use of this therapy for post-exposure prophylaxis.

Bamlanivimab and etesevimab, administered together, also remain authorized for the treatment of mild-to-moderate COVID-19 in adults and pediatric patients (12 years of age and older weighing at least 40 kg) with positive results of direct SARS-CoV-2 viral testing, and who are at high risk for progression to severe COVID-19, including hospitalization or death.

According to the FDA post-exposure prophylaxis as authorized with bamlanivimab and etesevimab, administered together, is not a substitute for vaccination against COVID-19. The agency says that it has approved one vaccine and given emergency use authorization to others in an attempt to help prevent COVID-19 and serious clinical outcomes caused by COVID-19, including hospitalization and death. The FDA urges you to get vaccinated if you are eligible. 

Bamlanivimab and etesevimab, administered together, may only be used as post-exposure prophylaxis for adults and pediatric patients (12 years of age and older weighing at least 40 kg) who are:

• at high risk for progression to severe COVID-19, including hospitalization or death, and
• not fully vaccinated or who are not expected to mount an adequate immune response to complete SARS-CoV-2 vaccination (for example, people with immunocompromising conditions, including those taking immunosuppressive medications), and
• have been exposed to an individual infected with SARS-CoV-2 consistent with close contact criteria per Centers for Disease Control and Prevention (CDC), or
• who are at high risk of exposure to an individual infected with SARS-CoV-2 because of occurrence of SARS-CoV-2 infection in other individuals in the same institutional setting (for example, nursing homes or prisons)

In general, people are considered fully vaccinated two weeks after their second dose in a two-dose series (the Pfizer or Moderna vaccines) or two weeks after a single-dose vaccine (the Janssen vaccine).

The CDC defines close contact as someone who has been within six feet of an infected person (laboratory-confirmed or a clinically compatible illness) for a cumulative total of 15 minutes or more over a 24-hour period.

The primary data supporting the EUA revision for post-exposure prophylaxis of COVID-19 are from Part 1 of a randomized, double-blind, placebo-controlled Phase 3 study (BLAZE-2), that evaluated bamlanivimab alone for the prevention of COVID-19 in residents and staff of skilled nursing facilities following a confirmed reported case of SARS-CoV-2 infection at the facility. All participants in Part 1 were randomized and treated with a single infusion of bamlanivimab or a placebo. Results of baseline testing for SARS-CoV-2 were not known until after the therapy was administered. Those with a positive baseline SARS-CoV-2 RT-PCR test were included in the treatment population (N=132) and those with a negative test were included in the prevention population (N=966). The primary endpoint (cases of symptomatic COVID-19 by Day 57) was assessed after all participants in the prevention population reached 8 weeks of follow-up. There were 114 cases of symptomatic COVID-19, with a lower frequency occurring in participants treated with bamlanivimab as compared to placebo reducing the risk of being infected with COVID-19 by up to 57%. For the pre-specified subgroup of nursing home residents, there were 45 cases of symptomatic COVID-19, with a lower frequency in those treated with bamlanivimab versus placebo, reducing the risk of being infected with COVID-19 by about 80%. For the post-hoc subgroup of patients who met the high-risk criteria (all residents and all high-risk staff), there were 75 cases of symptomatic COVID-19, with a lower frequency in those treated with bamlanivimab versus placebo, reducing the risk of being infected with COVID-19 by about 72%.

While the BLAZE-2 study only evaluated dosing with bamlanivimab alone, it is reasonable to expect that bamlanivimab and etesevimab together may be safe and effective for post-exposure prophylaxis as bamlanivimab and etesevimab administered together will provide an advantage over bamlanivimab alone against certain SARS-CoV-2 viral variants.

The most common side effects of bamlanivimab and etesevimab, administered together, are nausea, dizziness and pruritus (itching). Serious hypersensitivity reactions, including anaphylaxis, and infusion-related reactions were observed in clinical trials and have been reported in patients who have received bamlanivimab and etesevimab under the EUA. Other important information for these trials including other outcomes and side effect information is available in the health care provider fact sheet.

People should talk to their health care provider about whether the use of this therapy for post-exposure prophylaxis is appropriate for them.