If not before, then certainly since the first messenger RNA (mRNA) vaccines to fight the SARS CoV2 virus were approved in Germany, mRNA has become a term recognized even outside scientific circles. What is less known is that mRNA can be used to produce much more than just vaccines. About 50 different procedures for the treatment of diseases, including cancer, are already being studied in clinical trials. Scientists at the pharmaceutical company AstraZeneca, with the support of neutron researchers at Forschungszentrum Jülich, have now discovered how the subcutaneous delivery of mRNA can be improved. The goal is for patients with chronic illnesses to be able to self-administer the drug on a regular basis.
MRNA serves as a template in our cells for the production of protein molecules. The mRNA drugs could therefore create proteins directly in the patient’s body, targeted at the site where they are needed. Besides cancer, many other diseases are potentially treatable: hemophilia, for example, when the formation of a coagulation factor is disturbed, can be treated by administering the model for that factor itself. After a heart attack or stroke, injecting mRNA could allow proteins to form, which allow new blood vessels to grow.
Compared to current therapies, mRNA production is faster and more flexible because mRNA can be easily made and the process is independent of mRNA sequence. In addition, the technology allows for the rapid development of personalized drugs and proteins can be produced in the body over an extended period of time and with modifications otherwise difficult to achieve.
MRNA is rapidly broken down in the body by ubiquitous enzymes. It is important to prevent this from happening before the mRNA reaches the cells where protein synthesis takes place. In addition, it is necessary to ensure that the messenger reaches the right cells and in sufficient quantity. Even though there are procedures in which “naked” mRNA is administered, the use of secure packaging and some sort of “address label” is much more efficient.
An advanced packaging system is exemplified by so-called lipid nanoparticles (LNP), tiny vesicles made up of a mixture of fat-like substances. Each of them performs a specific task, such as stabilizing the construct or delivering it to the cell.
When given intravenously or intramuscularly, LNPs already sufficiently serve their purposes, but when given subcutaneously, LNPs trigger significant inflammation. Subcutaneous application would be essential to allow patients to inject the drug on their own, just as diabetic patients do with insulin. Particularly in chronic diseases which require regular doses of a drug, this would be of great benefit.
So far, only small insufficient amounts can be safely injected subcutaneously. Current studies by researchers at AstraZeneca and the Jülich Center for Neutron Science (JCNS) show how this problem can be solved. Scientists supplemented mRNA packaging with precursors of anti-inflammatory substances from the steroid class. The body’s own enzymes can convert these precursors into effective steroids at the injection site.
Steroids have a strong anti-inflammatory effect, but can still have considerable side effects, especially if taken regularly. These side effects can be minimized by incorporating a steroid precursor into the LNP so that it is delivered and activated only at the site where it is needed, i.e. the site where the LNPs are injected.
However, it is important to make sure that the steroid precursors are accessible to the enzymes. Therefore, they must be localized outside the lipid nanoparticles.
Researchers have tried to ensure this by adding longer or shorter “fat-loving” extensions to the active substances. The idea is that the fat-loving areas would be inserted between the fatty bodies of the LNP envelope so that the steroid precursors would end up positioned on the outside. Scientists were able to prove this to be the case using neutron scattering studies on the KWS-2 small-angle scattering instrument, operated by the JCNS at its outpost at the Heinz Maier-Leibnitz Zentrum in Garching.
“The KWS-2 instrument allows us to study fine structures, up to nanostructures, using the contrast variation method,” explains Dr. Aurel Radulescu, a scientist specializing in JCNS instruments. “In this process, the hydrogen atoms of the individual components are exchanged for heavy hydrogen. It does not change the physical chemistry of the sample, but it does change the visibility of the neutrons. Neutrons can differentiate between the two isotopes and thus recognize which hydrogen atoms belong to which molecule. “In this way, the different components of the lipid nanoparticles can be selectively labeled and differentiated from each other. And of course, the researchers found the steroid precursors outside the particles, at least in the longer stretches.
“Understanding what the surface of LNP looks like is fundamental to the other challenges that affect the development of LNP,” adds Dr. Marianna Yanez Arteta, Senior Associate Scientist in Advanced Drug Delivery at AstraZeneca. “Neutron scattering combined with selective isotope contrast is, to my knowledge, the only technique available that allows us to probe lipid distribution and resolve the surface.”
Other studies carried out in AstraZeneca’s laboratory have confirmed the anti-inflammatory effect of the new LNP variants. Scientists also studied the length of the fat-loving rod to ensure an optimal balance between efficient mRNA delivery and the inflammatory response. “Incorporating an anti-inflammatory component into LNP greatly simplifies therapy and may open it up to other treatments,” predicts Dr. Yanez Arteta. If anti-inflammatory LNPs now also prove their value when used in humans, they could indeed open up new treatment options for a wide range of diseases.