Challenges ahead

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Despite the enthusiasm for this type of promising cancer treatment, it is important to remember: “We are only at the beginning and the results will be different from the immediate success of the covid-19 vaccines”, ponders Seder. First of all, mRNA cancer vaccines will not be made available at the same extraordinary speed as covid-19 vaccines authorized for emergency use; cancer vaccines will require years of trials and clinical trials.

One of the reasons for the difference in the time between the development of mRNA vaccines against covid-19 and their use in cancer treatment is the therapeutic objective of each one.

The goal of current mRNA vaccines is to prevent covid-19: they are designed to provide a sample of the spike protein characteristic of the coronavirus, so that if people come into contact with the virus, their immune system can fight it off. it. On the other hand, mRNA cancer vaccines are used as therapies: they teach patients’ immune systems to seek out and destroy existing tumor cells.

Another challenge in using mRNA vaccines is figuring out how to build a nanoparticle that effectively releases messenger RNA to the required location. “If it is unprotected, the messenger RNA will not enter cells and, when introduced into the body, it will be rapidly degraded,” explains Anderson. ”

We can protect it and insert it into cells, encapsulating it in a lipid-like nanoparticle.” In this way, nanoparticles can bypass the body’s clearance mechanisms and enter the correct cells. (Currently, lipid-based nanoparticles are the most common delivery system used in clinical trials of mRNA vaccines for the treatment of cancer.)

However, even using an ideal delivery system, mRNA vaccines are unlikely to be a definitive solution for all types of cancer. But they are another promising tool for treating advanced or incurable cancers. And researchers are already looking into the possibility of using mRNA vaccines in conjunction with other immunotherapies, such as checkpoint inhibitors (which release a natural brake on the immune system so that

T lymphocytes can recognize and attack tumors) or adaptive therapy with T lymphocytes (where T lymphocytes are taken from a patient’s blood or tumor, stimulated to grow in the laboratory, and then reinfused into the patient to help the body recognize and destroy the tumor cells).

So far, there are few published studies on trials of mRNA vaccines used to treat cancer in humans, but there are signs of optimism. In a phase one trial that looked at the use of mRNA vaccines in conjunction with immunological checkpoint inhibitors in the treatment of head and neck or colorectal cancer,

Bauman and his colleagues found notable differences: in five of 10 patients with cancer of the brain. head and neck, the combination therapy reduced the tumors and two patients showed no signs of cancer after the end of treatment; on the other hand, the 17 patients with colorectal cancer did not respond to the combination of treatments.

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