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While news about the COVID-19 vaccine — which prevents infection — is getting most of our attention these days, we cannot ignore the importance of developing effective treatments for those who are sick with the virus. You may be aware of some of the medications that have become standard care for treating people who are hospitalized with COVID-19, such as the antiviral drug remdesivir or the steroid dexamethasone.

However, you may not be as familiar with a type of treatment that can be used to prevent hospitalization in high-risk patients, and which medical experts hope more patients and providers will start using: monoclonal antibody treatment.

Also known as “antibody cocktails,” these treatments are given as intravenous infusions in people who already have a known COVID-19 infection and are at risk for becoming severely ill from it because of underlying health issues — but who are still early on in their infection. Research has shown that these monoclonal antibodies can help reduce the risk of hospitalization and death by up to nearly 90 percent.

Here’s everything you need to know about monoclonal antibody treatments, particularly if you have chronic illness or are immunocompromised.

How Do Monoclonal Antibody Treatments Work to Treat COVID-19?

When your body encounters a viral infection, it creates a variety of antibodies in response. Some of these antibodies reduce the virus’ ability to replicate. Early in the COVID-19 pandemic, experts started studying which antibodies were most effective at stopping the virus. Next, they began producing them in bulk in the lab.

The result: monoclonal antibodies — antibodies created by cloning a unique white blood cell (this is where it gets the name “monoclonal”). Since then, these monoclonal antibodies have been tested as COVID-19 treatments.

These molecules act as substitute antibodies that can restore, enhance, or mimic how your immune system would normally ward off the virus, according to the U.S. Food & Drug Administration (FDA). Monoclonal antibodies may block the SARS-CoV-2 virus from attaching to human cells and help neutralize the virus (meaning they stop the virus from replicating).

Think of them as reinforcements from someone who had more time to build up defenses against COVID-19 — which your immune system can benefit from earlier on. As STAT describes it, the extra immune support is akin to a third-grader getting help from a sixth-grade friend on a math problem.

In this way, monoclonal antibodies can help stop a COVID-19 infection from developing into severe illness. However, it’s important that the treatment be administered early on in the COVID-19 infection — within 10 days of symptoms onset.

“The monoclonal antibodies are a way to slow down the virus’s replication, so really, time is of the essence when somebody is infected,” says Howard Huang, MD, an expert in monoclonal antibody treatments for COVID-19 and Medical Director of the Lung Transplant Program at Houston Methodist Hospital in Texas.

“Early on in the infection, the virus’s objective is to replicate as quickly as possible, and we know that people who develop very high viral loads and are unable to clear that tend to be the ones who become severely ill or hospitalized,” adds Dr. Huang.

In other words, timing matters: Monoclonal antibodies are helpful early on when you’re infected, but may not be useful for patients who are already severely sick. In fact, monoclonal antibodies may be associated with worse clinical outcomes in patients already hospitalized with COVID-19 who require high-flow oxygen or mechanical ventilation, per the FDA.

After receiving monoclonal antibody treatment, patients tend to see improvements quickly.

“We’ve treated about 4,000 patients in our metropolitan area with monoclonal antibodies, and it really depends on the patient,” says Dr. Huang. “There are some patients who are immediately better — within hours or by the next day, they’re feeling fantastic. And then there are ones who take days or maybe a week or two before they really feel back to normal.”

How Are Monoclonal Antibodies Different From Other Types of Antibodies?

A COVID-19 infection triggers an immune response that generates a mix of polyclonal antibodies (meaning they are produced by several different immune cells), some of which can neutralize the SARS-CoV-2 virus. However, this process takes days to weeks in most people, says Dr. Huang.

The current COVID-19 vaccines stimulate an immune response against parts of the SARS-CoV-2 virus, which also produces antibodies. Although vaccines are designed to produce mostly neutralizing antibodies, they are not considered monoclonal. It typically takes two weeks after you’re fully vaccinated for your body to build full protection against the SARS-CoV-2 virus, per the U.S. Centers for Disease Control and Prevention (CDC).

When a hospitalized COVID-19 patient receives convalescent plasma therapy, they get neutralizing polyclonal antibodies from recovered donors. This is considered passive immunity — meaning an infected individual is given an immune response that’s not necessarily their own. Not all antibodies in convalescent plasma have neutralizing activity, which is why the potency of the plasma can vary widely depending on the donor.

Monoclonal antibodies are unique in that unlike polyclonal antibodies found in convalescent plasma, there isn’t variability in their ability to neutralize the virus. That’s because they are clones of one parent cell.

“Monoclonal antibodies are selected for high neutralizing capacity and are mass-produced,” says Dr. Huang. “Unlike immunity after recovery from COVID-19 infection or vaccination, which takes days to weeks to build up, the recipient immediately has a very high titer of neutralizing antibodies.” A titer is a measurement of antibodies in the blood.

Who Should Get Monoclonal Antibody Treatment for COVID-19?

Monoclonal antibody treatments are not FDA approved, but have received emergency use authorization (EUA). In an emergency like a pandemic, the FDA may not be able to gather all of the evidence it usually would before approving a drug, device, or test. However, if there’s data that strongly suggests patients benefit from a particular treatment and there’s a declared emergency, the FDA can issue an EUA to make it available without formal approval.

COVID-19 vaccines in the U.S. also have EUA rather than FDA approval.

The FDA has recommended that high-risk patients who meet the following EUA criteria for monoclonal antibody treatment discuss the potential benefits and risks with their doctor:

  • Body mass index (BMI) of 35 or greater
  • Chronic kidney disease
  • Diabetes
  • Immunocompromising condition
  • Currently receiving immunosuppressive treatment
  • Age 65 or older
  • Age 55 or older and
    • Cardiovascular disease or
    • Hypertension or
    • Chronic obstructive pulmonary disease or another chronic respiratory disease

“All of those groups are considered high-risk because we know that they are more likely to get admitted to the hospital if they develop COVID-19, and the purpose of the monoclonal antibody is to prevent that progression,” says Raymund Razonable, MD, Professor of Medicine and Infectious Disease Physician at the Mayo Clinic.

“We have observed reductions in the number of hospitalizations, mortality, and ICU admission in patients who are given monoclonal antibodies. All of those are good outcomes, and that’s why we are advocating the use of monoclonal antibodies against COVID-19 for high-risk patient populations,” Dr. Razonable continues.

Possible side effects of monoclonal antibodies include fever, chills, dizziness, lightheadedness, nausea, or vomiting. These symptoms are generally mild and can be easily managed with over-the-counter medications. “In our experience, those side effects happen in roughly less than 1 percent of patients who are infused,” says Dr. Razonable. “It’s very rare.”

Monoclonal antibodies have been studied in lower-risk populations and appear to produce the same effect in preventing progression to severe disease. However, the treatment hasn’t been approved for use in these populations.

What Chronic Illness and Immunocompromised Patients Should Know About Monoclonal Antibody Treatments

Monoclonal antibody treatments are an important tool for avoiding severe COVID-19 outcomes if you’re in a high-risk group.

“This is a tool that chronic illness or immunosuppressed patients should really seriously consider if they do become infected,” says Dr. Huang. “It’s a way to get around this problem of perhaps not having as vigorous of a response to vaccination. Having monoclonal antibody treatment available is going to be a useful backup.”

“The people who tend to benefit from these treatments the most are the ones that are early in their course where they have a high viral load and they have yet to mount an immune response of their own,” Dr. Huang continues. “We’re giving their immune system a leg up by giving those neutralizing antibodies at a high concentration.”

The COVID-19 Vaccine and Monoclonal Antibody Treatment

If you have had a COVID-19 infection and received monoclonal antibodies, you will still benefit from getting the COVID-19 vaccine to protect yourself from another infection.

However, it is recommended that you wait 90 days after receiving monoclonal antibody treatment for COVID-19 to get a vaccine. This is a precautionary measure to avoid potential inference of the antibody treatment with your body’s immune response to the vaccine, according to the CDC.

On the other hand, if you are already vaccinated and then get infected with COVID-19 afterward, you can receive monoclonal antibody treatment. However, monoclonal antibody treatment is less likely to have a significant difference for individuals who have already generated an immune response to vaccination and developed neutralizing antibodies, says Dr. Huang.

That said, this treatment may be particularly helpful if you are immunocompromised, if your doctor suspects you did not mount a full response to the COVID-19 vaccine, or you weren’t able to get the vaccine.

This is why you can think of monoclonal antibody treatment as a backup plan if you could have trouble fighting off COVID-19.

“People who have compromised immune systems may not respond as effectively to vaccination,” says Dr. Huang. “In those particular populations, being able to immediately confer a high level of neutralizing antibodies through monoclonal antibody infusion could potentially prevent the disease from becoming severe.”

Which Monoclonal Antibody Treatments Are Authorized for Use in COVID-19?

Two companies currently have treatments that have received EUA from the FDA: Regeneron and Eli Lilly and Company. The U.S. government recently purchased nearly 1 million doses of monoclonal antibodies from these companies and have made them available to 5,800 sites across the nation, per USA Today.

Regeneron offers a two-drug cocktail with these monoclonal antibodies:

  • Casirivimab
  • Imdevimab

Lilly provides a two-drug cocktail with these monoclonal antibodies:

  • Bamlanivimab
  • Etesevimab

“Although these two treatments have not been studied head-to-head by the manufacturers, our clinical experience suggests that they are both equally effective,” says Dr. Razonable.

That said, if the COVID-19 variant that originated in Brazil or South Africa is circulating in your community, your doctor may recommend Regeneron (more on that shortly).

Otherwise, the treatment you receive will largely depend on what is available at the facility where you are getting care. At his clinic, Dr. Razonable says both drugs are available. “We basically just randomly give them, without a preference of one over the other,” he says.

Another pharmaceutical company, GlaxoSmithKline (in collaboration with Vir Biotechnology) submitted a request to the FDA in March for its monoclonal antibody treatment. The companies are working on a formulation of the antibody that could be given via two shots rather than an infusion like the existing treatments are delivered.

Monoclonal antibody injections are also being studied in clinical trials by Eli Lilly and Regeneron in different settings (lower-risk populations, as a preventive measure for individuals who have been exposed to SARS-CoV-2, etc.).

However, IV infusion has the perk of delivering monoclonal antibodies at a high concentration immediately. “It will likely remain the best option for higher-risk populations,” says Dr. Huang.

Could Monoclonal Antibody Treatment Be Affected by Coronavirus Variants?

Certain monoclonal antibody treatments may be more effective against particular COVID-19 variants than others.

“There is the possibility that a variant may emerge that’s more resistant to the existing antibodies that are available, but the nice thing is that there is a battery of neutralizing antibodies that are being studied,” says Dr. Huang. “These companies are able to respond to emerging variants, hopefully by mixing and matching these various neutralizing antibodies.”

The authors of the federal guidelines for monoclonal antibody use noted that Lilly’s current combination may not be as effective against many viral variants, even though it still appears to work well against the B.1.1.7 variant that originated in the United Kingdom.

Data shows that variants containing the mutation E484K — such as the variants that originated in Brazil and South Africa — reduce the virus’s susceptibility to bamlanivimab and etesevimab (Lilly) in vitro. That said, the clinical impact of these mutations has yet to be seen — meaning we don’t know if patients with these variants who are treated with monoclonal antibodies don’t do as well. Although the E484K mutation may reduce casirivimab activity, the combination of casirivimab and imdevimab (Regeneron) appears to still be effective.

Clinicians may take this into consideration when choosing treatment for their patients.

“All of those now are part of our treatment algorithm,” says Dr. Razonable. “Generally, in patients who have the usual variant, there is no preference of one over the other. But in patients who have variants that are labeled as the South Africa variant or Brazil variant, then the preference will be the casirivimab and imdevimab monoclonal antibodies [Regeneron].”

That said, doctors are not generally able to test for which variant a patient has. Instead, they must rely on which variants public health authorities say are circulating in the local community.

Why Aren’t Monoclonal Antibody Treatments More Frequently Used?

Many of the monoclonal antibody doses distributed have gone unused and still sit in hospital refrigerators, the New York Times has reported. In other cases, some hospitals are unable to access enough doses.

“There’s a great degree of variation across the country in terms of how easily somebody can plug into a system that’s able to deliver these antibodies in a timely fashion,” says Dr. Huang. “I think the important thing is to try to make it as available to the general community as possible, and I know the government is working to try to drive that initiative across the country.”

Monoclonal antibody drugs for COVID-19 would normally cost $2,000 to $2,500 for a single-dose treatment but are currently provided for free by the government. (However, depending on your insurance coverage, you may need to pay for the administration of the drug from your health care provider.)

Still, they’re not frequently used when they are available. “The use of this product is not as much as we originally expected,” says Dr. Razonable.

Underuse may be due to several factors. Hospitals might be focused on distributing vaccines first and foremost. Centers that administer monoclonal antibodies must find space where they can infuse the treatment without causing the spread of the virus — since all the patients receiving it have COVID-19 infection. Some hospitals may hold back supplies because they’re afraid of running out. Patients may be reluctant to go to a clinic when they’re sick with COVID-19, according to USA Today.

“We’re having to figure out a way to bring people who are potentially highly infectious into the clinic early on in the course of their disease, so these treatments can be effective,” says Dr. Huang.

Distributing monoclonal antibody treatments can be challenging because they require an extended infusion and an hour of observation.

“The amount of time it’s taken to infuse the product has gone down, so it can be as short as 20 or 30 minutes,” says Dr. Huang. “But the emergency use authorization requirement still states that these patients need to be observed for any reactions after the infusion for an hour.”

These logistics can be challenging for certain centers. Regeneron is currently studying the efficacy of delivering its antibodies through four near-simultaneous shots rather than an infusion, with promising results so far. If this treatment is approved, it could make the drug easier to administer.

Dr. Huang adds it’ll be important to target underserved communities when it comes to making monoclonal antibody treatments available. Last month, the Biden administration announced a $150 million plan to provide greater access to the drugs, especially for patients in vulnerable communities.

How Can You Get Monoclonal Antibody Treatment?

Monoclonal antibody treatments are proving to be a highly effective tool in preventing severe COVID-19 outcomes in at-risk patients, such as those who are immunocompromised. While getting vaccinated is critical, this treatment can arm you with one more tool to protect yourself if you happen to get infected with COVID-19.

Because monoclonal antibody treatments work best early on in infection, it’s important to get tested for COVID-19 as soon as you have symptoms and discuss next steps with your doctor. The treatments are authorized for mild to moderate COVID-19 in adults with a positive COVID-19 test result and a high risk for progressing to severe COVID-19 or hospitalization.

It may be helpful to research ahead of time which medical centers near you offer monoclonal antibody treatments. You can do so using this therapeutics distribution tool from the U.S. Department of Health & Human Services.

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COVID antibody treatments show promise for preventing severe disease. Nature. March 12, 2021. https://www.nature.com/articles/d41586-021-00650-7.

COVID-19 Frequently Asked Questions. U.S. Food & Drug Administration. April 16, 2021. https://www.fda.gov/emergency-preparedness-and-response/coronavirus-disease-2019-covid-19/covid-19-frequently-asked-questions.

Coronavirus (COVID-19) Update: FDA Authorizes Monoclonal Antibodies for Treatment of COVID-19. U.S. Food & Drug Administration. November 21, 2020. https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-monoclonal-antibodies-treatment-covid-19.

Interim Clinical Considerations for Use of COVID-19 Vaccines Currently Authorized in the United States. Vaccines & Immunizations. U.S. Centers for Disease Control and Prevention. March 5, 2021. https://www.cdc.gov/vaccines/covid-19/info-by-product/clinical-considerations.html.

Interview with Howard Huang, MD, an expert in monoclonal antibody treatments for COVID-19 and Medical Director of the lung transplant program at Houston Methodist Hospital in Texas

Interview with Raymund Razonable, MD, Professor of Medicine and Infectious Disease Physician at Mayo Clinic

Lilly’s bamlanivimab and etesevimab together reduced hospitalizations and death in Phase 3 trial for early COVID-19. Eli Lilly and Company. March 10, 2021. https://www.prnewswire.com/news-releases/lillys-bamlanivimab-and-etesevimab-together-reduced-hospitalizations-and-death-in-phase-3-trial-for-early-covid-19-301243984.html.

Phase 3 Trial Shows REGEN-COV™ (Casirivimab with Imdevimab) Antibody Cocktail Reduced Hospitalization or Death by 70% in Non-Hospitalized COVID-19 Patients. Regeneron. March 23, 2021. https://newsroom.regeneron.com/news-releases/news-release-details/phase-3-trial-shows-regen-covtm-casirivimab-imdevimab-antibody.

The COVID-19 Treatment Guidelines Panel’s Statement on the Emergency Use Authorization of Anti-SARS-CoV-2 Monoclonal Antibodies for the Treatment of COVID-19. COVID-19 Treatment Guidelines. National Institutes of Health. April 8, 2021. https://www.covid19treatmentguidelines.nih.gov/statement-on-anti-sars-cov-2-monoclonal-antibodies-eua/.

Therapeutics Distribution. HHS Protect Public Data Hub. Accessed April 21, 2021. https://protect-public.hhs.gov/pages/therapeutics-distribution#distribution-locations.

Things to Know About COVID-19 Vaccines. COVID-19. U.S. Centers for Disease Control and Prevention. April 22, 2021. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/keythingstoknow.html.

Thomas K, et al. What to Know About the Covid Antibody Drugs That Could Help Many. The New York Times. January 21, 2021. https://www.nytimes.com/2020/12/23/health/coronavirus-antibody-drugs.html.

Weintraub K. ‘Like somebody gave me a happy pill’: Monoclonal antibodies help Americans most at risk for COVID-19. USA Today. April 18, 2021. https://www.usatoday.com/in-depth/news/health/2021/04/17/covid-19-monoclonal-antibodies-fda-coronavirus/4813685001/.

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