The Truth Behind Why Were Monoclonal Antibodies Banned for Some Uses

October 10, 2025 •

4 min read

Between 2021 and 2023, the U.S. Food and Drug Administration (FDA) revoked Emergency Use Authorizations for several specific COVID-19 treatments. While this led to public questions asking why were monoclonal antibodies banned, the reality is more nuanced, involving a complex interplay of viral evolution, therapeutic effectiveness, and evolving safety data.

Quick Summary

Regulatory agencies did not ban all monoclonal antibodies. Instead, specific therapeutics were withdrawn from use due to reduced efficacy against viral variants or the emergence of unacceptable safety risks.

Key Points

No Blanket Ban: Regulatory agencies have never issued a general ban on the entire class of monoclonal antibodies; only specific products have been withdrawn for precise reasons.
COVID-19 Efficacy Loss: Many COVID-19 monoclonal antibodies, like those from Regeneron and Eli Lilly, were withdrawn because viral mutations, particularly the Omicron variant, rendered them ineffective.
Serious Adverse Events: Some monoclonal antibodies, such as daclizumab for multiple sclerosis, were voluntarily withdrawn from the market due to reports of unexpected and severe side effects, like inflammatory brain disorders.
Risks Outweighed Benefits: In cases like certain Alzheimer's treatments (e.g., aducanumab), the drug was withdrawn because the serious risks, including brain bleeding and swelling, were deemed to outweigh the modest clinical benefits.
Early Trial Failures: Life-threatening adverse events like cytokine release syndrome have caused the cessation of development for some investigational monoclonal antibodies in early clinical trial stages.
The Regulatory Process: The withdrawal of specific monoclonal antibodies demonstrates that the regulatory system functions to protect public health by removing products when new evidence shows they are no longer safe or effective.

The idea that all monoclonal antibodies were banned is a widespread misconception, stemming primarily from regulatory decisions made concerning COVID-19 treatments during the pandemic. In reality, regulatory bodies like the U.S. Food and Drug Administration (FDA) continue to approve and oversee a wide array of monoclonal antibody therapies for conditions ranging from cancer to autoimmune diseases. The perceived "ban" was not a class-wide prohibition but a series of targeted withdrawals based on evolving scientific evidence regarding the efficacy and safety of specific drugs.

The Role of Viral Evolution in COVID-19 Treatment Withdrawals

For many, the most visible instance of monoclonal antibody withdrawals occurred during the COVID-19 pandemic. Several products, including bamlanivimab, etesevimab, casirivimab/imdevimab (REGEN-COV), and sotrovimab, initially received Emergency Use Authorization (EUA) for treating COVID-19. However, their effectiveness was short-lived as the SARS-CoV-2 virus mutated and new variants, particularly Omicron, emerged.

Viral Resistance and Decreased Efficacy

Monoclonal antibodies are highly specific, designed to target a particular part of a virus, such as the spike protein of SARS-CoV-2. When the virus mutates, the shape of this target can change, preventing the antibody from binding effectively. As the Omicron variant became dominant, it became clear that the first generation of COVID-19 monoclonal antibodies could no longer neutralize the virus effectively. The FDA concluded that the known and potential benefits of these treatments no longer outweighed the known and potential risks, leading to the revocation of their EUAs.

Reasons for COVID-19 Monoclonal Antibody Withdrawal:

Viral mutation: The evolution of the SARS-CoV-2 virus, particularly the emergence of the Omicron variant, rendered many antibody treatments ineffective.
Lack of neutralization: The antibodies were no longer capable of binding to the altered viral spike protein, making them useless for treatment.
Risk vs. benefit assessment: The FDA determined that administering an ineffective treatment unnecessarily exposed patients to potential side effects, thus shifting the risk-benefit analysis.
Availability of alternatives: The availability of effective oral antiviral medications, such as Paxlovid, also contributed to the decision to withdraw less-effective therapies.

Withdrawal of Monoclonal Antibodies Based on Safety Concerns

Regulatory action can also be driven by safety signals that emerge during or after clinical trials. While many monoclonal antibodies have excellent safety profiles, some have been associated with serious adverse events (SAEs) that necessitate their withdrawal from the market.

Examples of Safety-Related Withdrawals

One prominent example is daclizumab, a monoclonal antibody approved for treating multiple sclerosis. In 2018, it was voluntarily withdrawn by its manufacturer after being linked to serious inflammatory brain disorders, including encephalitis and meningoencephalitis, in some patients. Post-market surveillance and reporting of these events demonstrated that the drug posed an unacceptable level of risk for its intended use, despite having previously been considered safe for other autoimmune conditions.

Risk-Benefit Reevaluation for Alzheimer's Treatment

The development of monoclonal antibodies for Alzheimer's disease has also highlighted the complex balance between risk and benefit. Drugs like aducanumab and lecanemab, designed to clear amyloid plaques from the brain, have shown only modest clinical benefits but are associated with significant risks, including amyloid-related imaging abnormalities (ARIA). ARIA can manifest as brain edema or hemorrhages. The serious, potentially life-threatening nature of these side effects has raised ethical and regulatory questions about whether the modest benefits justify the substantial risks, particularly in vulnerable patient populations.

Why Monoclonal Antibodies Are Not a Monolithic Drug Class

The term "monoclonal antibodies" covers a vast range of biologics, each with a unique target and mechanism of action. A problem with one monoclonal antibody does not imply a problem with all of them. The regulatory process is designed to evaluate each drug individually.

Understanding the Specificity of Monoclonal Antibodies

Unlike small-molecule drugs, which might have broader effects, monoclonal antibodies are highly selective. This specificity is a major advantage, but it also means their effectiveness can be compromised if the viral or cellular target evolves or changes. This is distinct from a problem with the drug class itself. For example, the regulatory issues with COVID-19 treatments and Alzheimer's treatments are unrelated to the effectiveness and safety of monoclonal antibodies used for cancer or autoimmune diseases, which remain valuable treatment options.

Comparison of Monoclonal Antibody Withdrawal Reasons


Reason for Withdrawal	Example Drugs	Therapeutic Area	Underlying Cause	Regulatory Action Basis
Efficacy Loss	Bamlanivimab, Regeneron's REGEN-COV, Bebtelovimab, Sotrovimab	COVID-19	Viral evolution led to resistance against dominant variants like Omicron.	Ineffectiveness; benefits no longer outweigh risks.
Serious Adverse Events	Daclizumab (Zenapax, Zinbryta)	Multiple Sclerosis	Reports of severe inflammatory brain disorders like encephalitis.	Unacceptable safety profile discovered through post-market surveillance.
Unacceptable Risk-Benefit	Aducanumab (Aduhelm), Lecanemab (Leqembi)	Alzheimer's Disease	Modest clinical benefit combined with significant risks like brain edema and hemorrhages (ARIA).	Risks judged to outweigh the minimal observed benefits.
Early Clinical Trial Failures	TGN1412 (TeGenero)	Immunomodulation	Life-threatening cytokine release syndrome in early-stage human trials.	Immediate cessation of trials due to extreme safety hazard.

Conclusion: The Nuance of Regulatory Scrutiny

The idea that monoclonal antibodies were banned is a misinterpretation of specific regulatory actions. In reality, the withdrawal of certain products—particularly those used for COVID-19 and certain autoimmune conditions—highlights the robust, evidence-based process by which drugs are evaluated and monitored. Regulatory agencies swiftly adapt to new scientific data, removing products that are no longer effective or carry an unacceptable risk profile. This continuous oversight is a crucial part of patient safety and explains why specific monoclonal antibodies are removed from use, while others continue to provide groundbreaking therapeutic benefits for millions of patients worldwide. The targeted nature of these withdrawals ensures that the broader field of monoclonal antibody therapy remains a cornerstone of modern medicine.

Visit the FDA website for detailed information on drug recalls and regulatory updates.

Frequently Asked Questions

No, all monoclonal antibodies were not banned. The FDA only revoked the Emergency Use Authorization for specific monoclonal antibody treatments for COVID-19 when they were no longer effective against new viral variants. Other monoclonal antibodies for different diseases remain in use.

Many COVID-19 monoclonal antibodies stopped being used because the SARS-CoV-2 virus mutated, and newer variants like Omicron became dominant. These mutations changed the virus's spike protein, making the original antibodies unable to bind and neutralize the virus effectively.

Yes, like all medications, monoclonal antibodies can have side effects. In rare cases, some have been associated with serious adverse events, such as inflammatory brain disorders with daclizumab for MS, or brain bleeding and swelling with some Alzheimer's treatments.

A drug recall typically involves removing a product from the market due to quality or safety defects. A product withdrawal, in this context, refers to a company or regulatory agency ceasing the authorization or marketing of a product based on new data concerning efficacy or a reevaluation of the risk-benefit profile.

The use of animals in antibody development raises ethical concerns, and research continues to find alternatives. However, the FDA recently announced a plan to phase out animal testing requirements for monoclonal antibodies and other drugs, allowing for new, non-animal testing methods.

Not all monoclonal antibodies become ineffective. The issue of ineffectiveness due to viral evolution is most prominent with infectious diseases like COVID-19. Monoclonal antibodies used for stable, non-evolving targets, such as those for cancer or autoimmune diseases, are not subject to the same kind of resistance and can remain effective long-term.

After approval, monoclonal antibodies are continuously monitored through post-market surveillance. This includes collecting data on reported adverse events, conducting phase IV clinical trials, and reassessing the risk-benefit balance based on real-world use, as was done for daclizumab.