mRNA vaccines became 3 times more effective: breakthrough by Mt Sinai

Breakthrough in mRNA Vaccines: Mount Sinai Scientists Find Way to Triple Efficacy

A new study in Nature Biotechnology overturns established views on how mRNA vaccines work: suppressing expression in liver cells can boost anti-cancer immune response and reduce toxicity.

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Revolution in mRNA Therapy: How Suppressing Liver Expression Triples Vaccine Efficacy

Introduction

The COVID-19 pandemic made mRNA vaccines the number one technological breakthrough. But until recently, it was believed that their efficacy depended on mRNA reaching dendritic cells—the main "conductors" of the immune response. Researchers at the Icahn School of Medicine at Mount Sinai in New York have completely overturned this established view.

In April 2026, a paper published in Nature Biotechnology not only rewrites the fundamental biology of mRNA vaccines but also offers a specific technological method to triple their efficacy. The key to the breakthrough turned out to be the liver: suppressing expression in liver cells (hepatocytes) dramatically enhances the anti-cancer immune response.

This discovery changes the rules for designing mRNA drugs—from cancer vaccines to therapies for autoimmune diseases, where, conversely, immune suppression is required.

Event Details and Timeline

Overturning a 20-Year Dogma

For two decades, researchers believed that the key target of mRNA vaccines was dendritic cells. It was thought that these cells should capture mRNA, produce antigen, and present it to killer T cells. The team led by Brian D. Brown, director of the Icahn Genomics Institute, proved otherwise.

Using their own technology for suppressing expression (microRNA target sites), the scientists learned to "turn off" protein production in specific cell types. Experiments showed that even if mRNA is not expressed in dendritic cells, a strong T-cell response still forms. It turned out that non-immune cells (muscle and liver cells) can produce antigen and transfer it to the immune system through a mechanism called cross-presentation.

Mechanism: Muscles Enhance, Liver Suppresses

The most surprising finding was the difference in functions of non-immune cells:

• Muscle cells (myocytes): When researchers turned off expression in muscles, the T-cell response decreased. Thus, muscle tissue plays a positive role, enhancing vaccine immunity.
• Hepatocytes (liver cells): Turning off expression in the liver led to a threefold increase in T-cell response. Liver cells, it turned out, actively suppress the immune response to mRNA vaccines.

"Hepatocytes actively suppress the immune response to mRNA vaccines," explains Sophia Siu, co-lead of the study. "This is important because hepatocytes take up a lot of mRNA, especially with intravenous administration. For vaccines, we don't want expression in hepatocytes, but for therapeutic mRNAs, expression in the liver can be beneficial as it prevents immunity to the encoded protein."

Impact and Significance

For Oncology: 50% Reduction in Tumor Burden

The practical results were impressive. In mouse lymphoma models, a vaccine designed with suppressed expression in hepatocytes led to a reduction in tumor burden by more than 50%. This happened because "turning off" the liver allowed the body to generate significantly more killer T cells.

"These results show that we can make mRNA cancer vaccines more effective simply by controlling where the encoded antigen is expressed," comments Josh Brody, director of the lymphoma immunotherapy program at the Mount Sinai Cancer Center. "This is a new lever for improving immunotherapy."

For Safety: Reduced Toxicity

Beyond efficacy, the study revealed an important safety aspect. When mRNA is used to boost existing T cells (e.g., in CAR-T therapy or genome editing), its expression in hepatocytes causes the death of these cells. Suppressing expression in the liver prevents this unwanted toxicity.

Dr. Brody emphasizes: "mRNA vaccines are already very safe. Our work shows we can make them even safer and more effective by precisely controlling where they act."

Expanding the Boundaries of mRNA Therapy

The study has implications beyond vaccines. The developed microRNA-targeting technology opens doors for creating mRNA drugs with controlled expression. A related paper published by the same group in December 2025 in Molecular Therapy demonstrated the cSMRTS system, which allows therapeutic genes to be turned on exclusively in cancer cells using their unique microRNA profiles.

Reactions from Key Players

Scientific Community

The publication in Nature Biotechnology generated widespread resonance in academic circles. Researchers praised the methodological rigor of the work, especially the use of microRNA target site technology to dissect cellular mechanisms. Concurrent developments in the field were also noted.

For example, in December 2025, a group from MIT led by Zhang Feng published a paper in Nature on DFI therapy, which also uses hepatocyte-targeting of mRNA but for a completely different purpose—restoring immunity in old mice by reprogramming the liver into a "growth factor factory." This confirms that the liver is becoming a central organ in the new wave of mRNA applications.

Industry and Regulators

Although no commercial announcements from major pharma companies (Pfizer, Moderna) have followed yet, it is clear that Mount Sinai's technology has direct licensing implications. Patent applications for the system have been filed, and the team is working on commercialization and preclinical development.

At the national level, attention to mRNA technologies is growing. For example, in Russia, in August 2025, the Scientific and Technological Center for the Development of mRNA Technologies began operations at Kazan Federal University, with participation from the National Medical Research Center of Radiology and the Gamaleya Center. The center's priority is the development of mRNA vaccines for treating oncological diseases.

Forecast and Conclusions

The Mount Sinai study marks the transition of mRNA technology from the first generation ("deliver RNA into the body") to the second generation ("deliver RNA precisely to the right cells and exclude unwanted ones").

Key forecasts:

• New standard for cancer vaccines. In the next 3–5 years, we will see clinical trials of mRNA vaccines with suppressed liver expression. If the mouse results are confirmed in humans, a threefold increase in T-cell response strength could become the standard of care for resistant forms of cancer.

• Platform separation. Understanding that hepatocytes suppress immunity while muscle cells enhance it will allow the creation of drugs with opposing goals:

Immunosuppression (autoimmune diseases):* Intentional delivery of mRNA to the liver to induce tolerance.

Immunostimulation (cancer, infections):* Exclusion of liver expression + enhancement in muscles.

• Solving the toxicity problem. The technology is critical for the developing field of in vivo CAR-T and gene therapy, where hepatocyte death is a serious limitation.

Conclusions

The Mount Sinai breakthrough clearly demonstrates that the most important discoveries often lie in revisiting fundamental principles. For years, scientists tried to improve mRNA vaccines by perfecting lipid nanoparticles for delivery to dendritic cells. It turned out that the answer lay not in complicating the carrier, but in understanding how ordinary liver cells suppress our immune system.

"mRNA technology is transformative for medicine," concludes Brian Brown. "Our work provides a new set of design rules for mRNA vaccines and therapeutics."

By turning off the liver, science has ushered in a new era of personalized immunotherapy. We now await the transition of these "design rules" from Mount Sinai laboratories into clinical practice, where they could save thousands of lives of cancer patients.

— Editorial Team