The Promise and Challenges of mRNA Vaccine Development

Robert Dream - HDR Company LLC

Decades of research led to the development of the first mRNA vaccine that has changed the course of the Coronavirus Disease 2019 (COVID-19) Pandemic. Looking ahead to the potential of mRNA whether that is starting or building out capacity for producing mRNA vaccines or other mRNA-based therapeutics, the possibilities are endless.

Current trends and perspectives of the applications, potential, and benefits of mRNA therapies for infectious diseases, oncology, and other therapeutics indicates a promise of entering into a new era of patient hope and resolve.

The COVID pandemic brought mRNA vaccines to the forefront of innovation and progress in therapeutical medicine with the rapid release of highly efficacious (93–95%) vaccines by BioNTech/Pfizer and Moderna. Once the sequence of SARS-CoV-2 was published, Moderna had its first candidates available in only 28 days.⁶ Full phase 1–3 trials and release of millions of doses were completed in months, much shorter than the years typically required for vaccines discovery, development and commercial launch.⁷

In addition to the shortened development time and high efficacy, there are other advantages in the use of mRNA for both prophylactic and therapeutic vaccines.⁸ One is the safety profile, which includes that the antigen is typically expressed for only a matter of days and can be modulated by the design of the mRNA. mRNA vaccines are also much more controllable than attenuated and vector vaccines. Unlike DNA-based approaches, mRNA vaccines do not require nuclear entry, so there is less risk of genomic integration and mutagenesis. mRNA vaccines enable robust development of cellular and antibody responses, these can be targeted to some degree by the design of the mRNA, the choice of delivery method, or other approaches.

The core principle behind mRNA as a technology for vaccination is to deliver the transcript of interest, encoding one or more immunogen(s), into the host cell cytoplasm where expression generates translated protein(s) to be within the membrane, secreted or intracellularly located. Two categories of mRNA constructs are being actively evaluated; non-replicating mRNA (NRM) and self-amplifying mRNA (SAM) constructs. See Figure 1.

There are also advantages in the production method, as synthesis is based on well-established in vitro transcription processes in a cell-free system. The cell-free system helps reduce cost, time, and manufacturing footprint. The plasmid DNA (pDNA) template for mRNA vaccines requires a cell-based fermentation step, but this is not a highly costly or time-consuming step. mRNA offers flexibility, as vaccines for variants or multivalent vaccines can typically be manufactured without a significant change of production process.

mRNA is transcribed from a linearized pDNA template then captured, concentrated, encapsulated, and purified for delivery to patients.

mRNA therapeutics is an exciting emerging therapeutic modality. There are opportunities for improvement and maturation, especially in the areas of manufacturing, administration, and supply chain.

Due to its negative charge, mRNA does not easily enter the cells. It can be rapidly degraded by nucleases such as the enzyme RNase. Lipid nanoparticle (LNP) encapsulation, which is used in the current mRNA based COVID vaccines, helps mitigate this problem, as do other methods involving substitution of modified bases or design of the mRNA. Alternatively, physical methods such as electroporation can be employed. This approach has gained traction in ex-vivo–administered therapeutic cancer vaccines but is not highly efficient.

Distribution of vaccine is another issue, as current mRNA vaccines require frozen storage. Alternative methods, such as lyophilization, are under study.⁹ Manufacturing also presents issues, one of the main challenges in mRNA processing is the lack of dedicated equipment and consumables fit for the relatively small volumes and large size of mRNA molecules, compared to traditional recombinant proteins. There is also room in technology development to improve scalability and process consistency.

mRNA Industry Perspectives

With the quick spread of the COVID pandemic, mRNA for prophylactic vaccines took the public spotlight due to an urgent need. These vaccines demonstrated the promise of mRNA therapeutics through their quick developmental timeline and high efficacy.

While COVID vaccines are notable, most mRNA vaccines investigated to date have been focused on cancer therapy (e.g.; iNeST, BioNTech-Genentech/Roche), and dozens of clinical trials have been completed or are ongoing. Many of the ongoing trials are for personalized therapeutic cancer vaccines and should be completed in the next one to four years. Promising results in this area could further advance the mRNA industry.

Many therapeutics are in early development, across diverse areas that will have high impact if successful. Success in mRNA therapies could potentially displace less effective therapeutic approaches, such as vaccines for influenza, tuberculosis, or other applications.

Types of mRNA-Based Therapies

The COVID vaccines are prophylactic vaccines for infectious disease. Other prophylactic vaccines are in development against influenza, Zika, dengue, rabies, and Venezuelan equine encephalitis viruses, as well as bacterial infections such as Staphylococcus and tuberculosis. ^9,11 Unique approaches include expression of a neutralizing monoclonal antibody for chikungunya virus.⁹

mRNA vaccines have gained traction as a therapeutic approach for cancer. mRNA can elicit immune responses to mutated oncogenes or regulatory cancer genes such as TP53, which are shared across many cancers, in a therapeutic pan-cancer approach.

Other approaches for cancer include personalized therapy, where vaccines are developed for a person’s individual mutations. In this regard, a patient’s mutanome would be identified by next generation sequencing, and a handful of custom mRNA vaccines would be developed targeting the individual’s particular neoantigens.¹

Therapeutic cancer vaccines are advancing quickly in development, with over 70 clinical trials completed and more results expected in the next two to three years.¹⁰ Techniques under evaluation include the direct stimulation of antigen-presenting cells (APCs) via ex vivo electroporation of mRNA. Other approaches include direct intra-tumor injection, whole body approaches, and targeted organ approaches. Currently large number of clinical trials using mRNA focuses on the treatment of melanomas, prostate and brain cancer.¹⁰ While numerous applications of mRNA vaccines are in various stages of development, targeting specific organs, tissues, and cells with LNPs is still under research.

mRNA Technologies

The structural elements of the mRNA have an impact on its performance. This includes potential immunogenicity, efficacy of translation and stability of the molecule. Developers/manufacturers leverage experience to design, synthesize, manufacture and formulate therapeutics mRNA, and adapt its composition to suit the desired application. Examples of commercial applications and/or in clinical stage are as follows:

Infectious Disease

1. Covid (Coronavirus)
2. Influenza (mod mRNA)
3. Influenza (as mRNA)
4. Shingles
5. Malaria
6. Tuberculosis
7. HSV - herpes simplex virus
8. HIV - human immunodefi ciency virus
9. VZV - Varicella-Zoster Virus
10. EBV - Epstein–Barr virus
11. CMV - Cytomegalovirus

Oncology

1. Fixed combination of shared cancer antigen
2. iNeST - patient specific cancer antigen therapy
3. Intratumoral immunotherapy
4. mRNA-encoded antibodies
5. mRNA-encoded cytokines

to name a few and others as well.

It’s all about proteins - An mRNA can teach the body how to make a specific protein that can help the immune system to prevent or treat certain diseases.

The use of mRNA could grow new blood vessels after a heart attack. Or fight off an aggressive cancer.

What is mRNA? Messenger RNA–or mRNA–exists in all of the cells in the body. It is an essential component of all living organisms.

A mRNA drug product needs to be appropriately formulated in order to be protected from degradation by extracellular RNAses. The right formulation is critical to ensure the appropriate delivery of the RNA to the intended site of action.

To employ multiple mRNA delivery formulations, each should be designed for different functions and optimized for therapeutic product needs based on the intended application and route of delivery. An optimized mRNA provides superior immunogenicity.

Encapsulation and Delivery Technologies

The use of nanostructures, such as LNPs, is common in mRNA therapeutics. These generally deliver higher efficiency than naked mRNA and allow for a broad variety of administration routes. A challenge with nanostructure technology is that, it is complex by nature, and involves many potential ingredients with many possible clinical outcomes. There is incomplete understanding in this regard. Nanostructure properties are critically important to clinical outcomes and include protection of nucleic acids, controlled release of RNA inside the cell, cell and tissue selectivity, translation efficiency, toxicity, and long-term stability.⁷

Nanostructures are sophisticated and may be composed of several components, such as common lipids, polymers, proteins, cholesterol, or custom proprietary components such as ionizable lipids.^8,9 Often, conjugates such as polyethylene glycol–lipids are used. Each of these components influences the structural properties. For example, polymer content can control particle size and affect efficiency and cell tropism. Structural lipids, such as cholesterol, can affect particle stability. Empty nanoparticles without payload can form if not mixed correctly. Thus, nanostructure composition and formation are critical for desired clinical effect.⁷ LNPs are the leading non-viral delivery system for many systems, including gene therapy.⁷

There are other delivery methods under study and development. Exosomes are thought to use a receptor, and may offer more efficient uptake, greater specificity, and fewer side effects.² This is a promising early area of research.

Naked mRNA has been evaluated for cancer therapy by approaches including direct injection to the tumor. Generally, naked RNA is considered less efficient than other methods, but it is easy to prepare, as it requires only a buffer.^5,9 In some applications, the intrinsic high immunogenicity of naked mRNA may provide benefit via boosted adjuvant activity.⁵

Trends in mRNA-Based Therapeutics

The potential of mRNA vaccines gained scientific attention in 1990 after the in-vivo expression of a protein was observed after injection of naked mRNA into the skeletal muscle of a mouse.¹⁰ Since then, the industry has seen rapid development and expansion. Today, more than 140 clinical trials have looked at mRNA to address infectious disease, cancer, and a variety of other application areas.

Two forms of mRNA structure are currently being developed: conventional non-replicating mRNA and self-amplifying mRNA. Non-replicating mRNA vaccines have the conventional mRNA form, and do not have replication capability built into the mRNA sequence. The sequence of the antigen is flanked by untranslated (UTR) regions, a 3’ poly (6) tail, and a 5’ cap. The cap, UTR, Open Reading Frame (ORF), and tail can be designed to up- or down-regulate expression, or to modulate immune response.⁹

Modified nucleotides such as pseudouridine and 5-methylcytidine can be used to lessen undesirable innate immune system responses and to increase translation efficiency.^7,9 Thus, there are many aspects of the clinical response that can be modulated simply by the design of the mRNA.

Non-replicating mRNA vaccines are transient by nature and typically express antigen for a few hours or days (the cellular half-life of the BioNTech/Pfizer and Moderna vaccines is estimated to be eight to ten hours). For some applications this can be beneficial, however for others such as systemic protein therapies, extended expression of a protein would be beneficial.

Self-amplifying mRNA (saRNA) approaches, which enable the mRNA to replicate, are under development. This, in turn, can extend the expression window to weeks (four to six weeks). Typically, saRNA is based on the addition of viral replicase genes, in cis or trans configuration, from alphavirus, flavivirus, or picornavirus. These strategies can either increase expression level or lower mRNA dose requirements 10 to 100-fold. saRNA could potentially expand mRNA technology across many applications while lowering manufacturing demand. There are many areas of mRNA technology that are under development, optimization and mRNA design are important aspects of current efforts.

Other RNA therapies outside of mRNA are being developed or have been approved. Among these are antisense oligonucleotides, which modify gene expression; small interfering RNA (siRNA), which also modifies gene expression via a different mechanism; aptamers, which can bind other ligands, including RNA; and guide RNAs, used for CRISPR targeting. Many of these RNA therapeutics share overlapping technology with mRNA vaccines. An example is Alnylam’s approved siRNA therapeutic Onpattro©, which uses LNP technology.^7,8 Thus, RNA therapeutics overall is advancing rapidly in addition to mRNA vaccines.

What is the Difference Between an mRNA and a Viral Vector Vaccine?

Both mRNA and viral vector vaccines contain instructions that teach our cells how to create “spike proteins”, which is the protein found on the surface of the virus that causes COVID-19. Once your cells produce COVID-19 spike proteins, your immune system recognizes that those proteins don’t belong in your body and creates antibodies to stop the virus from spreading and causing damage when you are exposed to it. Neither vaccine contains the virus that causes COVID-19.

The instructions in the mRNA vaccines are messenger RNA (mRNA), the genetic material that tells your cells how to make proteins. The mRNA is surrounded by tiny lipids (fatty molecules) which help mRNA enter directly into your cells. Once your cells create the spike proteins, your body breaks down the mRNA.

In viral vector vaccines, spike protein DNA is placed inside a modified version of a different virus that doesn’t cause illness. This non-harmful virus delivers the DNA instructions to your cells. This virus is called the vector.

Transformation

It is a credit to decades of research and innovation that led to the mRNA vaccine through technology and science to come to fruition. With the disruption of the COVID pandemic, this technology got its moment and has proven to be extremely safe and effective. Pfizer’s COVID-19 vaccine is the first mRNA product to achieve full FDA approval in the U.S. Vaccine manufacturers are progressing in developing mRNA vaccines to protect against other respiratory viruses such as the flu. Moderna is exploring applications of the technology to protect against HIV. It’s a new era for vaccine technology and production, and a testament to scientific progress and decades of research. mRNA research was under study and development for decades, the global pandemic has redefined “business as usual” across countless industries, creating an array of opportunities and roadblocks for today’s professionals and organizations. Scientist and others are tackling some of the biggest challenges anticipated by post-pandemic world from transformational trends in bioprocessing to the technologies that are reimagining biomanufacturing for the digital age.

The convergence of science, technology, regulatory, relevant equipment manufactured to suit and facility design will be a paradigm shift that is required to accelerate drug substance and product manufacture and delivery to the patient. By localizing the operation site in an optimized closed system, units can be implemented in a local setting eliminating the complicated and costly supply chain. This is a key to business success and reaching the patient. Emphasizing the employee experience, innovation experts know that the most successful, cutting-edge products are designed around the end-user/ patient experience. Human-centered design strategies can also benefit the workplace. With a deep understanding of employees’ functional and emotional needs, business leaders can design a workplace that not only enables productivity, but also recognizes workers’ humanity, and brings balance to the forefront/operation.

Exploring the trends transforming bioprocessing, fueled in part by challenges resulting from the pandemic, a new work paradigm is emerging in the field of biopharmaceutical manufacturing. To stay ahead in this “new normal,” industry players must embrace a range of trends, from building flexibility in supply chains to incorporating AI and machine learning strategies to prioritizing employee health and safety.

Building a more equitable world and understanding the potential of participatory design and collaborative approaches to global challenges are informed by participatory design, a groundbreaking concept in which end users are actively involved in the innovation process. Through participatory design, we learn how to connect more meaningfully with people of diverse perspectives, and to make decisions with them collectively and quickly. This can lead to more desirable and sustainable solutions.

How will cities transform in a post-pandemic world? The built environment is constantly evolving, but every so often, major changes redefine the trajectory of city development. The global pandemic and rapid development of new technologies has brought us to the cusp of another transformative moment in the history of urban landscapes.

The built environment is constantly evolving, but every so often, major changes redefine the trajectory of development. The global pandemic and rapid development of new technologies has brought us to the cusp of another transformative moment in the history of urban landscapes.

References

1. Vormehr M, Schrörs B, Boegel S, Löwer M, Türeci Ö, Sahin U. Mutanome engineered RNA immunotherapy: towards patient-centered tumor vaccination. J Immunol Res. 2015(2015);595363. doi: 10.1155/2015/595363.
2. Tsai S-J et al. Exosome-mediated mRNA delivery for SARS-CoV-2 vaccination. Preprint at bioRxiv 2020 (Nov 6). doi: 10.1101/2020.11.06.371419
3. Springer AD, Dowdy SF. GalNAc-siRNA conjugates: leading the way for delivery of RNAi therapeutics. Nucleic Acid Ther. 2018 Jun;28(3):109-118. doi: 10.1089/nat.2018.0736.
4. Lou B, De Koker S, Lau CYJ, Hennink WE, Mastrobattista E. mRNA polyplexes with post-conjugated GALA peptides efficiently target, transfect, and activate antigen presenting cells. Bioconjug Chem. 2019 Feb 20;30(2):461-475. doi: 10.1021/acs. bioconjchem.8b00524.
5. Zeng C, Zhang C, Walker PG, Dong Y. Formulation and delivery technologies for mRNA vaccines. Curr Top Microbiol Immunol. 2020 (Jun 2); 10.1007/82_2020_217. doi: 10.1007/82_2020_217.
6. Teo SP. Review of COVID-19 mRNA vaccines: BNT162b2 and mRNA-1273. J Pharm Pract. 2021(Apr 12);8971900211009650. doi:10.1177/08971900211009650.
7. Kim J, Eygeris Y, Gupta M, Sahay G. Self-assembled mRNA vaccines. Adv Drug Deliv Rev. 2021 (Mar); 170:83-112. doi: 10.1016/j.addr.2020.12.014.
8. Schoenmaker L et al. mRNA-lipid nanoparticle COVID-19 vaccines: structure and stability. Int J Pharm. 2021 (May 15);601: 120586. doi: 10.1016/j.ijpharm.2021.120586.
9. Xu S, Yang K, Li R, Zhang L. mRNA vaccine era-mechanisms, drug platform and clinical prospection. Int J Mol Sci. 2020 (Sep 9);21(18):6582. doi: 10.3390/ijms21186582.
10. Rosa SS, Prazeres DMF, Azevedo AM, Marques MPC. mRNA vaccines manufacturing: challenges and bottlenecks. Vaccine. 2021 (Apr 15);39(16):2190-2200. doi: 10.1016/j. vaccine.2021.03.038.
11. Maruggi G, Zhang C, Li J, Ulmer JB, Yu D. mRNA as a transformative technology for vaccine development to control infectious diseases. Mol Ther. 2019 (Apr 10);27(4):757-772. doi: 10.1016/j.ymthe.2019.01.020
12. Nicholas A. C. Jackson, Kent E. Kester, Danilo Casimiro, Sanjay Gurunathan and Frank DeRosa; “The promise of mRNA vaccines: a biotech and industrial perspective”, Published: 04 February 2020. https://www.nature.com/articles/s41541-020-0159-8
13. BioNTech - https://biontech.de/

Subscribe to our e-Newsletters
Stay up to date with the latest news, articles, and events. Plus, get special
offers from American Pharmaceutical Review – all delivered right to your inbox!
Sign up now!