Tag: mRNA

Preparing Drugs Ahead of Viral Disease Outbreak

Last month’s announcement[1] from the National Institute of Allergy and Infectious Disease that it was funding 9 research consortia – called “Antiviral Drug Discovery Centers for Pathogens of Pandemic Concern”, was welcome news. The idea that a concerted effort will be made to create COVID-19 antivirals, as well as ones targeting a range of (viral) families in anticipation of the next outbreak, is inspired. Bringing together academic researchers with pharmaceutical/industrial partners focused on multidisciplinary approaches is a real strength of the envisioned program. Congratulations to Dr. David Perlin (from the Hackensack Meridian Health Research Institute’s Center for Discovery and Innovation) and his collaborators for being selected as part of the program’s drug development initiative.[2]

Complementing the power of antivirals and their ability to alter the course of disease and/or reduce and prevent viral spread, are vaccines – designed to prevent infection altogether. The following discussion focuses on steps to accelerate development of just such antiviral vaccines.

Viruses
Image Source: Innovative Genomics Institute

Let us be clear – viruses have long been, and will continue to be, a plague on human health and well-being. Whether they be extant (e.g., SARS-CoV2, Ebola, West Nile), newly mutated variants, or recently developed from zoonotic (i.e., animal to human) transmission – infectious viruses will continue to do what they have done for thousands of years – copy and spread their genomes and compromise human health. How do we get out in front of this incoming and indeed ever-present onslaught? The answer is to prepare now.

Dr. Florian Krammer at the Icahn School of Medicine at Mount Sinai suggests that some 50-100 viruses should be identified and targeted for vaccine development.[3] Choice of which viruses to pursue would be based on infective potential, transmissibility, and accompanying symptoms/pathology. Such a curated list of potentially dangerous pathogens could be informed by recently developed approaches involving machine learning/artificial intelligence. Georgetown University researcher Dr. Colin Carlson and team have been working on just such approaches and have launched VIRION, a database (still in alpha testing) that is designed to help with the curation process. Powerful algorithms coupled with predictive modeling and detailed analytics allow, for the first time, an ability to predictably identify viruses with enhanced potential to infect humans.

Vaccine development in response to the COVID-19 pandemic proceeded at a pace unseen in modern medicine. Vaccine platforms are now in place such that even tighter timelines between virus identification and vaccine production may be realized. But every day – especially early in an outbreak – is critical and could mean the difference between life and death; so how can the program be maximally accelerated? Perhaps, as Dr. Krammer suggests, once viruses (and viral families) are identified, the process of vaccine development could commence. Not waiting for an actual viral outbreak across human populations is crucial.

Vaccine
Image Source: Flickr

mRNA-based vaccine development, which worked so well in the context of SARS-CoV2, could once again be brought to bear. Moderna’s mRNA Access program[4] would be particularly helpful here – assisting in the identification of appropriate antigen(s), the design of relevant mRNA coding sequences, and other stability, expression, and production parameters associated with its (mRNA) vaccine platform. Once candidate vaccines were developed and tested pre-clinically, they could be evaluated in FDA-approved phase 1 and 2 (drug) testing protocols. Having the results of such clinical trials would position the vaccines for rapid deployment in phase 3 testing when circumstances warranted. Once it is clear a (related) virus has been identified and an outbreak is imminent, scaled up production, distribution, and inoculation efforts would be rapidly initiated. What might have taken years in the past and took roughly a year for the COVID-19 vaccine, could now be accelerated to, Dr. Krammer predicts, 3-4 months (after identification of the relevant viral strain). The value of such preparedness in terms of reducing and/or eliminating the disease burden is incalculable. There are many hurdles (e.g., regulatory, monetary, coordination) that would need to be overcome to effect such a strategy – but the impact could truly be life-saving on a world-wide scale.

SRT – June 2022

[1] https://www.nih.gov/news-events/news-releases/nih-announces-antiviral-drug-development-awards
[2] https://njbiz.com/65m-grant-funds-joint-academic-pharma-drug-accelerator/
[3] Krammer, F. (2020). Pandemic vaccines: how are we going to be better prepared next time? Med, 1(1), 28-32.
[4] https://mrna-access.modernatx.com

mRNA Technology: A Shot in the Arm for Development of New Drug Therapies

As millions the world over receive mRNA-based vaccinations for COVID-19, there is hope that the virus and its attendant wanton destruction may soon be in our collective rear view mirrors. Other vaccine approaches, for example employing viral vectors, are making their way into the armamentarium of anti COVID-19 treatment options – the news just keeps getting better. The focus here is on mRNA technology – how did we get to this point, and what does it mean for the future?

mRNA vaccine COVID
Image Source: MIT News

The central dogma of molecular biology – loosely defined – states that DNA instructs mRNA creation, which directs protein synthesis. Ultimately, of course, it is the protein or enzyme created that is the molecule missing or defective in disease or needed to create immunity. DNA/gene-based therapies have existed for some time and recent advances have begun to overcome early technical problems encountered. The use of protein biologics – molecules produced in living cell “factories,” have also emerged as a viable option to treat protein/enzyme deficiencies or to introduce specifically designed functional antibodies. However, as a protein biochemist who has developed protocols for purifying enzymatically active protein biologics, I can assure you the process is exquisitely complex, time consuming, and costly. The approach can and has worked – it is simply a matter of committing the time and resources to empirically determining/optimizing the purification protocols.

Another option has emerged – specifically, the development of mRNA technologies as a mechanism to induce protein/enzyme expression. Again, as pointed out above – it is not that the role of mRNA in protein synthesis was unclear, rather, there were technical problems attendant to the approach. Let’s consider some of these previous limitations and how they were overcome to allow mRNA to be an efficient messenger of protein synthesis in humans.

mRNA is exquisitely unstable. RNAases – enzymes which break down mRNAs, are very efficient and ever present. mRNA will not enter cells, and if they could be transported, their mere presence often elicits an immune response. Couple this with relatively low protein yields from the cell’s translation processes – and the need for repeated dosing is manifest. So, what has changed?

First, Karikó and coauthors showed that employing specifically modified nucleosides in the design and synthesis of an mRNA molecule would render it far less immunogenic.1 A great first step! Next, the sequence of the mRNA coding region (the area that encodes the information for the protein itself) would take advantage of what was known about (protein) translation. That is, some codons (~mRNA sequences that encode specific amino acids) are expressed more efficiently than others – resulting in greater overall protein yields. Recall that most amino acids are encoded by more than one codon, that is, the genetic code is degenerate. Detailed structural analyses of mRNAs also yielded new information about the importance of 5’ and 3’ untranslated regions in terms of the molecule’s overall stability and translational efficiency. A more complete understanding of mRNAs’ 5’ cap and 3’ poly (A) tail served to further extend the ability to preserve the molecule’s integrity.

Next, it was necessary to design a delivery system – a mechanism that would both protect the mRNA molecule, as well as assure its entry into cells. Many approaches were tested – lipid nanoparticles emerged as an efficient option. Once encapsulated and introduced into tissues, the mRNAs are internalized into cells by endocytosis – basically an engulfment of the lipid vesicle by the cell’s plasma membrane. Once inside the cell – the nascent endosome degranulates and the mRNA molecule is able to emerge into the cytoplasm and begin directing protein synthesis. The cell itself thus makes the protein.

Where does the technology go from here? The answer – quite simply, is that mRNA therapy could potentially be a suitable approach to treat many human diseases. Single enzyme deficiencies constitute a large class of lysosomal storage diseases (e.g., Tay-Sachs or Inclusion-cell (I-cell)), inherited metabolic diseases (e.g., Gaucher or Hunter syndrome), and peroxisomal diseases (e.g., acyl-CoA oxidase or D-bifunctional protein deficiency). Arginase deficiency and cystic fibrosis (caused by the dysfunctional cystic fibrosis transmembrane conductance regulator molecule) are two additional proteins whose missing or defective activities are associated with disease and whose replacement is being sought through mRNA therapies. Designing and synthesizing appropriate mRNAs is relatively straightforward, as is lipid nanoparticle encapsulation. Cold chain handling of the resultant therapeutic remains a requirement – but what a small price to pay for what could be life-changing medicines. It would not be inappropriate to say “the sky is the limit” with respect to the potential of mRNA-based protein/enzyme replacement therapeutics.

SRT – February 2021

Reference:

[1] K. Karikó, M. Buckstein, H. Ni, and D. Weissman, Immunity (2005) doi: 10.1016/j.immuni.2005.06.008. PMID: 16111635