mRNA Lipid Nanoparticle Delivery of Monoclonal Antibodies: Redefining Passive Immunotherapy

mRNA lipid nanoparticle (LNP) technology has significantly changed the field of immunotherapy. It first became widely known for helping develop COVID-19 vaccines بسرعة and effectively. However, its potential goes far beyond vaccines. This technology can also be used for passive immunotherapy by allowing the body to produce monoclonal antibodies (mAbs) directly inside its own cells. Instead of manufacturing antibodies outside the body in complex and expensive facilities, mRNA delivers genetic instructions so that the patient’s cells can temporarily produce the antibodies themselves. This new approach may help solve major challenges in antibody therapy, such as high production costs, manufacturing delays, and formulation limitations.

A key study by Vu and colleagues (2026) provides a detailed preclinical evaluation of this strategy. The researchers tested mRNA/LNP delivery systems that produce neutralizing antibodies against SARS-CoV-2 and influenza viruses. Their work carefully examined how mRNA design, LNP formulation, pharmacokinetics, and protective effects influence overall performance. Importantly, the study establishes guiding principles that support the broader use of this technology in future immunotherapy applications.

Technological Foundations: From Vaccine to Antibody Factory

The adaptation of mRNA/LNP technology from vaccine delivery to antibody production represents a logical but technically demanding extension. Vaccines require transient, localized antigen expression sufficient to prime adaptive immunity, whereas therapeutic antibodies necessitate sustained, high-level production of complex multi-chain proteins with precise post-translational modifications. The Vu et al. study demonstrates that these requirements can be met through careful engineering of both the genetic payload and delivery vehicle.

Optimizing mRNA Design for Efficient Antibody Production

To produce a working antibody, the body must make two parts: a heavy chain and a light chain. These two parts must be produced in the right amounts so they can correctly assemble into a functional antibody.

Vu and colleagues tested two different design strategies. In the first approach, they delivered two separate mRNAs, one for the heavy chain (HC) and one for the light chain (LC), at equal amounts. In the second approach, they used a single mRNA that contained instructions for both chains linked together with a short sequence called P2A (HC-P2A-LC), which allows the cell to separate the two proteins during production.

In cell culture experiments (in vitro), both strategies produced similar levels of antibody. However, when tested in animals (in vivo), the single mRNA design worked much better. The HC-P2A-LC construct produced significantly higher antibody levels in the blood (p = 0.0079) and showed stronger virus-neutralizing activity.

This result highlights an important principle for immunotherapy: when both antibody chains are produced together inside the same cell from a single mRNA, the antibody assembles more efficiently. The P2A sequence ensures that equal amounts of heavy and light chains are made from one genetic message, reducing the variability that can happen when two separate mRNAs are delivered. For drug development, this single-construct strategy also simplifies manufacturing and improves performance in the body, making it more suitable for clinical use.

The study also used a modified building block called N1-methylpseudouridine in the mRNA. This modification, originally developed for mRNA vaccines, helps reduce unwanted immune reactions and increases protein production. It improves mRNA stability and translation efficiency, allowing higher and longer-lasting antibody expression. Together with optimized regulatory regions at the beginning and end of the mRNA, these improvements help achieve the sustained antibody levels needed for therapeutic benefit.

LNP Formulation: Solving the Delivery Problem

Lipid nanoparticles (LNPs) play two important roles. First, they protect the mRNA from being broken down in the body. Second, they help the mRNA enter cells and escape from cellular compartments so it can be translated into protein.

In the Vu et al. study, the researchers used an LNP formulation similar to the Pfizer/BioNTech COVID-19 vaccine (Comirnaty). It contained the ionizable lipid ALC-0315, helper lipid DSPC, cholesterol, and a PEG-lipid called ALC-0159. This formulation worked very well: about 90% of the mRNA was successfully packaged inside the particles. The particles were small (about 64 nanometers in size) and had a slightly negative surface charge (-8 mV).

The researchers also compared this formulation with another one that used a cationic (positively charged) lipid called MC3-DOTAP. Even though some previous studies suggested that positively charged lipids may improve lung delivery, this formulation did not work well for producing antibodies in the bloodstream. It resulted in very low antibody levels, no matter how it was administered. Only when given through the nose did it show limited expression in the lungs. This result shows that simply changing the surface charge does not reliably control where the mRNA will work in the body.

These findings demonstrate that LNPs designed for vaccines may not be ideal for antibody therapies. Vaccines often benefit from strong immune stimulation to enhance antigen presentation. However, for antibody therapy, too much immune activation can be harmful because it may speed up clearance of the treatment. Therefore, antibody delivery may require specially optimized LNP formulations that focus on stable protein production rather than immune stimulation.

Pharmacokinetics: Making Antibodies Inside the Body vs. Injecting Them

To use mRNA-delivered antibodies as a therapy, it is important to understand how they behave in the body compared to traditional injected antibody proteins. The study by Vu and colleagues provides a detailed comparison, following two antibodies (anti-SARS-CoV-2 PDI204 and anti-influenza HV-B10) for 70 days after treatment.

mRNA and protein delivery show different timing patterns in how antibodies appear and decline in the body.

When recombinant antibody protein is injected directly, the antibody level in the blood rises immediately to a high peak and then slowly decreases over time, following the natural half-life of IgG antibodies.

In contrast, when antibodies are delivered using mRNA, the peak level does not appear right away. Instead, it takes about 3–5 days to reach maximum levels. This delay happens because the mRNA must first enter cells, be translated into protein, and then the antibody must be secreted into the bloodstream. After about 7 days, antibody levels begin to decline more quickly.

This pattern has both advantages and disadvantages.

One advantage is that continuous antibody production inside the body can sometimes lead to even higher peak levels than injecting the protein itself. In the case of the HV-B10 antibody, mRNA delivery produced higher blood concentrations at all tested doses compared to protein injection. This ongoing production acts like a temporary “depot,” which may improve tissue penetration and increase antibody levels at disease sites.

However, there is also a limitation. The antibody levels dropped faster after mRNA delivery, usually becoming very low or undetectable by day 28.

mRNA/LNP Delivery Triggers Strong Anti-Drug Immune Responses Compared to Protein Injection Alone

The biggest challenge observed in the study was the development of anti-drug antibodies (ADA). All animals treated with mRNA/LNP developed strong immune responses against the human antibodies that were produced. In contrast, animals that received the antibody protein alone showed very little immune reaction.

This suggests that the LNP delivery system, especially certain ionizable lipids such as ALC-0315, may stimulate the immune system and act like an adjuvant, increasing the chance that the body recognizes the therapeutic antibody as foreign.

Part of this strong immune response is likely due to the fact that human antibodies were tested in mice, which increases the chance of immune rejection. In humans, this response may be weaker, but it may not disappear completely. Therefore, controlling immunogenicity will be a key challenge for mRNA-based antibody therapies. Future strategies may need to reduce immune activation or design systems that appear less foreign to the body.

Importantly, even though ADA developed, some antibody function remained. At day 28, about 50% of the neutralizing activity of the PDI204 antibody was still present. This suggests that the immune response did not completely block the antibody’s ability to bind its target. This partial activity could still be useful clinically and may influence how dosing schedules are designed.

Protective Effect Against SARS-CoV-2

Researchers tested whether mRNA/LNP-made PDI204 could prevent SARS-CoV-2 infection in special mice that can catch the virus. Mice received either mRNA/LNP or the regular antibody protein (1, 5, or 10 μg). Seven days later, they were exposed to the Omicron BA.1 virus. Viral levels in the lungs and nose were measured four days after infection.

The 10 μg dose of the recombinant protein gave strong protection. No virus was detected in the lungs (p = 0.0072). This strong effect is likely because the injected protein stayed at high levels in the blood.

In contrast, mice that received mRNA/LNP showed mixed results. Higher mRNA doses reduced viral levels, but none gave complete protection like the protein. The lower protection was likely due to anti-drug antibodies (ADA) that cleared the mRNA-produced antibody before virus exposure. Viral levels in the nose were similar in all groups.

These results show that protection from mRNA antibodies may be limited by immune clearance. Reducing immune reactions or improving RNA design may help extend protection.

Stronger Protection Against Influenza

Unlike the SARS-CoV-2 results, mRNA/LNP delivery of the influenza antibody HV-B10 showed much stronger protection than the same doses of injected protein. In this study, mice were infected with a lethal flu virus only 24 hours after receiving treatment.

Low doses (1 and 5 μg) of the recombinant protein did not protect the mice, and most died. Even at 10 μg, protection was only partial, with 60% survival and noticeable weight loss. The limited effect was likely due to low antibody levels in the blood and poor movement of the protein to the lungs within 24 hours.

In contrast, all mice that received HV-B10 mRNA/LNP survived, even at the lowest dose. Weight loss was also reduced in a dose-dependent way. mRNA delivery produced much higher antibody levels than protein injection, giving strong protection before anti-drug antibodies (ADA) began clearing the treatment.

When infection was delayed to 7 or 14 days after mRNA treatment, survival remained high, though protection weakened as antibody levels dropped and ADA increased. These results show that mRNA delivery can provide powerful but time-limited protection.

Expanding mRNA Antibody Therapy Beyond Infectious Disease

Beyond infectious diseases, mRNA/LNP delivery of antibodies has broad potential across cancer, autoimmune, metabolic, and genetic disorders. In oncology, antibodies against tumor-associated targets such as HER2, CD20, and EGFR could be produced directly in the body through mRNA delivery, potentially maintaining high therapeutic levels without repeated hospital infusions. The higher peak concentrations observed with mRNA compared to protein injection may improve antibody levels within tumor tissues, especially when combined with strategies that enhance LNP accumulation or tumor-specific targeting. Immune checkpoint inhibitors targeting PD-1, PD-L1, or CTLA-4 may particularly benefit from this approach, as periodic mRNA dosing could provide sustained immune activation while reducing treatment burden, although inflammation must be carefully controlled. The flexibility of mRNA also allows production of complex antibody formats such as bispecific T-cell engagers and antibody-drug conjugates, which are difficult to manufacture as recombinant proteins. In autoimmune and inflammatory diseases, mRNA delivery could support long-term cytokine neutralization or controlled B-cell depletion with adjustable dosing and the ability to stop expression if needed, potentially improving safety and adherence. Finally, in metabolic and genetic disorders, mRNA-encoded antibodies or fusion proteins could enhance enzyme replacement strategies, including delivery across the blood–brain barrier, and enable localized modulation of pathways involved in angiogenesis, tissue repair, and ischemic disease. Together, these applications illustrate the versatility of mRNA/LNP technology as a platform for in vivo antibody therapeutics across multiple disease areas.

Conclusion

The study by Vu and colleagues shows that mRNA/LNP delivery can successfully produce therapeutic antibodies inside the body. It proves the concept in different viral models and explains the key factors, such as antibody levels and immune responses, that are important for future clinical use. The research highlights both the strong potential and the current limits of this technology.

mRNA/LNP delivery offers major advantages, including faster manufacturing, lower cost, flexible dosing, and natural protein processing inside cells. This approach could support treatment of infections, cancer, and autoimmune diseases, and may even replace traditional protein antibody injections in some cases.

However, challenges remain, especially immune reactions and limited duration of protection. Improving LNP design and mRNA engineering will be important to make the therapy safer and longer lasting.

Just as mRNA vaccines changed the response to COVID-19, mRNA-made antibodies could allow rapid development of treatments against new diseases. This technology may lead to faster, more flexible, and on-demand immunotherapy in the future.

Reference:

Vu, M.N., Neil, J.A., Mackenzie-Kludas, C., Kelly, A., Tan, H.-X., Subbarao, K., Lee, W.S., & Wheatley, A.K. (2026). Delivery of monoclonal antibodies using mRNA lipid nanoparticles confers protection against SARS-CoV-2 and influenza. Molecular Therapy – Nucleic Acids. https://doi.org/10.1016/j.omtn.2026.102873

Image credit: Portions of the figure in this article were generated using ChatGPT (OpenAI) or Google Gemini.

Disclaimer: This blog post is intended solely for educational and scientific informational purposes. Any mention of therapeutic drug names, including FDA-approved medications, is for the purpose of accurate reporting and discussion of biomedical research and does not constitute medical advice, endorsement, or promotion. Readers should not interpret the content as a recommendation for any specific treatment. Always consult a qualified healthcare professional for medical advice or treatment decisions.

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