mRNA Technology: The 2021 Dr. Paul Janssen Award Symposium

Messenger RNA was discovered in 1961 and it took 60 years until the first mRNA became FDA-approved product in the form of COVID-19 mRNA vaccine. During those years a lot of progress has been made by hundreds of scientists. It was 1978 when the first-time isolated mRNA delivered into mammalian cells produced the encoded protein. In vitro transcription introduced in 1984 made it possible to generate any desired mRNA from the encoding plasmid using phage RNA polymerases. In the early 90s mRNA was used for therapy as well as vaccine against infectious diseases and cancer. Inflammatory nature of the mRNA limited its in vivo use. Replacing uridine with pseudouridine made the mRNA non-immunogenic and highly translatable. Delivery of the lipid nanoparticle-formulated nucleoside-modified mRNA encoding viral antigens became a platform for effective vaccine. Labile nature of the mRNA is ideal for transient production of the viral antigen, to generate effective antibody and cellular immune response.

Vaccines prevent 4-5 million deaths a year making them the principal tool of medical intervention worldwide. Nucleoside-modified mRNA was developed over 15 years ago and has become the darling of the COVID-19 pandemic with the first 2 FDA approved vaccines based on it. These vaccines show greater than 90% efficacy and outstanding safety in clinical use. The mechanism for the outstanding immune response induction are the prolonged production of antigen leading to continuous loading of germinal centers and the adjuvant effect of the LNPs, which selectively stimulate T follicular helper cells that drive germinal center responses. Vaccine against many pathogens, including HIV, HCV, HSV2, CMV, universal influenza, coronavirus variants, pancoronavirus, nipah, norovirus, malaria, TB, and many others are currently in development. Nucleoside-modified mRNA is also being developed for therapeutic protein delivery. Finally, nucleoside-modified mRNA-LNPs are being developed and used for gene therapy. Cas9 knockout to treat transthyretin amyloidosis has shown success in phase 1 trials. We have developed the ability to target specific cells and organs, including lung, brain, heart, CD4+ cells, all T cells, and bone marrow stem cells, with LNPs allowing specific delivery of gene editing and insertion systems to treat diseases such as sickle cell anemia. Nucleoside-modified mRNA will have an enormous potential in the development of new medical therapies.

Adult mammalian heart has a limited regeneration capacity after myocardial infraction (MI). The fundamental problem in is that after MI most of the dead cardiac muscle is replaced by fibrosis and scar tissue. This scarring reduces the ability of the heart to supply and sustain sufficient blood flow to the body, and leads to chronic heart failure. Chronic Heart failure is the leading cause of morbidity and mortality worldwide. Current heart failure treatments address the consequences of MI, but are not effective in enhancing myocardial repair. One possible treatment is via controlling injured tissue gene expression in the first phases of MI (first few hours - days). To do so, a safe transient and immediate expression approach, is needed.

Since 2013 we have shown that by using the modified mRNA (modRNA) technology we can drive a transient, safe and high transfection level gene expression in the heart. Exogenous unmodified mRNA that enters the cell via the cell membrane is recognized by endosomal Toll-like receptors 7/8. This process inhibits protein translation and activates the innate immune response, ultimately leading to apoptosis of the hosting cell. ModRNA is synthesized by substituting ribonucleotides with naturally modified ribonucleotides. The use of these modified ribonucleotides results in reduction of Toll-like receptor recognition of the modRNA and therefore permitting its translation to a functional protein by the ribosomal machinery without eliciting immune response or compromising the genome. ModRNA transfect different cell types in the heart including cardiomyocytes in high efficiency, leading to immediate and high levels of protein expression in a pulse like kinetic. Our goal is to use modRNA as a tool to control cardiac tissue gene expression to transiently allow cardiac regeneration post ischemic injury.