Miriam Merad, MD, PhD, the Mount Sinai Professor in Cancer Immunology (left), and Nina Bhardwaj, MD, PhD, Ward-Coleman Chair in Cancer Research (right), lead some of the most cutting edge research in mRNA technology at the Icahn School of Medicine at Mount Sinai.
The 2023 Nobel Prize in Medicine was awarded jointly to two researchers, Katalin Karikó, PhD, and Drew Weissman, MD, PhD, for their decades-long work on messenger RNA (mRNA), which ultimately led to the successful development of COVID-19 vaccines that made a huge difference during the pandemic.
The concept of using mRNA to deliver genetic instructions was met with a lot of skepticism in the beginning, says Nina Bhardwaj, MD, PhD, Ward-Coleman Chair in Cancer Research at the Icahn School of Medicine at Mount Sinai. Because these molecules were rapidly degraded by the immune system, they were thought to be too transient to be used to express anything therapeutic, such as antigens or other molecules in immune cells, she added.
“It’s really through the two researchers’ sheer hard work and determination and validation, both in the lab and in the clinic, that this became a technology that can be harnessed for patient benefit,” says Dr. Bhardwaj, who is also Director of Immunotherapy and Medical Director of the Vaccine and Cell Therapy Laboratory.
The validation of mRNA as a delivery mechanism has opened the doors to vaccines in many other diseases, including cancer, says Miriam Merad, MD, PhD, the Mount Sinai Professor in Cancer Immunology, and Director of the Marc and Jennifer Lipschultz Precision Immunology Institute (PrIISM) at Icahn Mount Sinai.
“We’ve been quite interested in the mRNA for some time—not only this type but also another called the micro RNA,” says Dr. Merad. Even prior to COVID-19, Mount Sinai researchers have recognized the potential of various RNA for use in vaccines, such as for cancer, she adds.
Read more from Drs. Bhardwaj and Merad on their thoughts on mRNA technology, and learn how Mount Sinai is leading this field with its research.
Katalin Karikó, PhD (left), and Drew Weissman, MD, PhD, were the joint winners of the 2023 Nobel Prize in Medicine. Dr. Karikó, a Hungarian-American biochemist who worked at the University of Pennsylvania, continues her research as a professor at the University of Szeged in Hungary. Dr. Weissman, an immunologist, advances vaccine work at his laboratory at the Perelman School of Medicine at UPenn.
What’s the history of mRNA technology development been like?
Dr. Bhardwaj: There was a lot of skepticism in the beginning about how exogenously-delivered RNA—which we usually think of as these transient molecules that are rapidly degraded—can be utilized to express antigens and other molecules in immune cells. So the concept that could happen was not well accepted initially.
Dr. Merad: Also, much of the early focus was on cancer, and researchers were not obtaining fantastic results. Cancer vaccines are still yielding anecdotal responses, and it might not have anything to do with the technology.
What do you feel was a turning point for that skepticism?
Dr. Bhardwaj: I think, in especially the last decade, this technology was being used a good deal at the National Institutes of Health’s Vaccine Research Center as a platform for developing vaccines against other infectious agents, not COVID-19 at the time. What had been generated from the platform showed promise, in preclinical models.
When the COVID-19 pandemic came along, there were highly immunogenic modified “cassettes” generated wherein one could just plug in antigens—such as the spike protein of the COVID-19 virus—which could be rapidly formulated into vaccines and tested.
But even prior to that, there were ongoing efforts to use this technology as platforms for cancer vaccines, which are now being tested in the clinic with encouraging preliminary results in randomized studies in melanoma.
Dr. Merad: I think the big two were the lipid nanoparticle (LNP) as a delivery mechanism, and of course, a disease that somehow was the perfect case to try this new therapeutic strategy.
Drs. Karikó and Weissman were able to change up the RNA prior to the injections so that the molecules persisted longer. They were making clear advances in the way the proteins were being made. But, still, the real fixes started when they learned to encapsulate the mRNA in nanoparticles.
In fact, Dr. Karikó went to BioNTech (which partnered with Pfizer to produce the COVID-19 vaccine) and Moderna also licensed mRNA technology, and what happened was that two companies developed a way of delivering mRNA. This extra component—the delivery mechanism—was what made therapeutics possible.
Also, the pandemic is kind of a boost for mRNA technology. Because, first, of the number of patients available, and second, we are in a bit of a risk-taking mode. These vaccines were already developed against pathogens, so they just had to be pivoted to COVID-19.
One solution that companies like Pfizer/BioNTech and Moderna used to protect the mRNA instructions in their vaccines from being degraded by the immune system was loading them into tiny fat particles known as lipid nanoparticles (LNPs). These delivery vehicles are also able to find the targeted cells, which mRNA molecules alone cannot achieve. Icahn School of Medicine at Mount Sinai honored the efforts of the BioNTech executives during its 54th Commencement in May 2023, conferring upon them honorary Doctor of Science degrees.
Learn more about LNPs and mRNA technology in a Q&A with BioNTech executives
What research is Mount Sinai doing with mRNA?
Dr. Bhardwaj: One exciting line of research includes work from Yizhou Dong, PhD, Professor of Oncological Sciences at Icahn Mount Sinai, who works with the Icahn Genomics Institute and PrIISM. He is one of our newly recruited faculty members, who has been working in this space for quite a while. He has demonstrated that RNA can be used as a platform to introduce various kinds of immune modulators into cells, including dendritic cells, a key cellular potentiator of the immune system.
Dr. Dong uses RNA-LNPs to introduce various types of immune modulators into immune cells and even cancer cells to enhance antitumor immunity. My team is using RNA-LNPs to encode newly identified antigens, such as neoantigens, which arise from mutations in cancer cells, and then use those within vaccine constructs.
In preclinical models, we have shown that such RNA-lipid constructs, developed in-house in The Tisch Cancer Institute, are immunogenic and can have therapeutic benefit in treating cancers. Our goal is to take that to the next level: develop our own vaccine constructs and deliver them into humans.
Dr. Merad: We’ve been interested in exploiting mRNA to translate into specific proteins. We have been very much interested in using mRNA to change the immunosuppressive environment of tumors, where we use mRNA to go into the tumor and start making it look like an infection to induce an antitumor immune response. There is a lot of effort in using mRNA to transform cancer lesions—which can suppress and evade the immune system—into something very inflamed that can be recognized by the immune system and lead to tumor clearance.
One of my colleagues, Brian Brown, PhD, Director of the Icahn Genomics Institute, and Professor of Genetics and Genomic Sciences at Icahn Mount Sinai, is quite interested in using mRNA in different types of disease settings. My lab is mostly looking at inflaming regions in cancer, or reducing inflammation in inflammatory diseases—in this case we use mRNA as cargo to deliver proteins that will dampen inflammation and enable inflammatory lesions to heal.
What do you see as the future of mRNA technology?
Dr. Bhardwaj: I think the breadth is enormous. We can add many different types of immune-enhancing modulators into these particles—not just antigens—including homing receptors and cytokines. RNA platforms have been given intramuscularly and intravenously, and it’s possible you may be able to deliver it intranasally and into the skin, as well as directly into tumors.
The scope of what we can do, what we can encode and add, and the potential combinations with other immunomodulatory agents is vast. I think the field is moving really fast, especially with new companies coming into the field and startups accelerating rapidly.
Dr. Merad: Right now, the big conundrum that we have is: how can we raise an immune response against cancer that is beneficial, without inducing a harmful response against other tissue? I think the answer is delivery.
With mRNA, it provides all the instruction needed for therapeutic effect, but what we are still working on is enhancing that cell-specific delivery system. If we were allowed to bring that instruction to the right compartment, then we can afford to do so much more.