Improving mRNA Therapeutics and Vaccines

The Future of mRNA Vaccines

COVID-19 mRNA vaccines were produced as rapidly as possible in response to the pandemic health emergency. Now that the peak demand has been met, manufacturers can turn their focus to addressing bottlenecks in production pipelines, with the view to increase yields and shorten production time. Such optimizations present many opportunities given that mRNA vaccines are being expanded to targets beyond COVID-19 and are poised to be a dominant vaccine methodology of the future. More diseases will be addressed with mRNA technology and multivalent vaccines (combinations of several mRNAs against a range of pathogens/variants administered in one shot) are under development.^{I, II}

One of the key issues currently encountered with mRNA vaccines is their propensity to activate Toll like receptor 7 (TLR7) responses and result in strong adverse reactions in patients, resulting in fever-like symptoms. Such side-effects can lead to having to reduce the amount of mRNA used, which limits the vaccine activity on the immune system. This effect of mRNA vaccines on TLR7 is therefore central to their efficacy, and failure to address TLR7 activation recently led certain mRNA vaccine developers to abort their programs due to poor protective efficacy against COVID-19 in phase III clinical trials.

Our proprietary TLR7 inhibitors are being developed to reduce the side-effects of mRNA vaccines and to improve the efficiency of vaccine production. It is proposed that they will help dampen the inflammatory effects of mRNA vaccines, while increasing their protective efficacy, and provide an alternative strategy to that of direct mRNA modification currently patented until 2027, with a capacity to help increase the yields of mRNA vaccines produced.

Pharm-RNA to tailor innate immune responses to mRNA therapeutics

mRNA vaccines are now being developed to target other diseases and are clearly here to stay. They have applications beyond coronavirus vaccination and the need to better understand, modulate and fine-tune activation of innate immune sensors which underpins their efficacy is greater than ever.

One of the key discoveries which underpinned the success of mRNA vaccines was the discovery made by Kariko and Weissman in 2005. The pair discovered that chemical modification of therapeutic mRNA was essential to be able to bypass innate immune sensors, including TLR 7 and 8, and allow for protein production from the mRNAs. Limiting innate immune detection turned out to be essential as it otherwise activates a broad antiviral response that elicits flu-like symptoms and can block protein production from the therapeutic mRNA.

How important mRNA modification and innate immune evasion is to the success of mRNA vaccines was recently highlighted with the failure of CureVac to produce an approved COVID-19 mRNA vaccine. In the CureVac phase III clinical trials the vaccine failed to protect over 50% of the patients treated. Unlike Pfizer and Moderna, CureVac opted to use non-modified mRNA for its trial. This approach led to stronger engagement of innate immune sensors, leading to dose limiting flu-like symptoms. As a result, the maximum dose in the CureVac vaccine was limited to a maximum 12 ug of mRNA– versus 30ug and 100 ug for Pfizer and Moderna, respectively.

The Pfizer-BioNTech and Moderna vaccines reduce TLR7 recognition by relying on pseudo-uridine modification of the mRNA, but this approach has its own limitations as it is directly impacted by the mRNA sequence used in the vaccine. Indeed, while pseudo-uridine modification of therapeutic mRNAs clearly works, it may be less effective in mRNA vaccines containing fewer uridines and more guanosine, the direct ligand of TLR7. As such, the strategy of relying on modified mRNA to evade immune recognition can be constrained by the sequence used, which varies for each protein encoded.

Pharmorage and its collaborators have discovered a range of oligonucleotides able to modulate and tailor innate immune responses. This is the basis of our expertise and associated intellectual property.

Pharm-RNA to optimize mRNA therapeutics production

mRNA vaccines are constituted of two main ingredients: a specific mRNA sequence, encoding the protein one wants to prime our immune system with, such as the spike protein of SARS-CoV-2, and a lipid nanoparticle, which is used to deliver this mRNA into cells. While this can seem trivial, the current manufacturing process developed during the pandemic to produce billions of vaccine doses is very complex, and largely open to improvements that could vastly reduce the cost and speed of production.

In addition to sometimes reducing protein expression from the mRNA in a sequence-dependent manner ^III, the use of base modifications such as pseudo-uridine significantly decreases the yield of mRNA obtained (by approximately 20% to 40%); this has a direct impact on the number of doses of vaccine produced.

Pseudo-uridine is currently used during synthesis of the mRNA to reduce engagement by TLR7. Pharmorage has developed a new group of oligonucleotides that specifically inhibit TLR7 activity based on ground-breaking research defining how TLR7 sensing of RNA works.

Pharmorage proposes to rely on these novel TLR7 inhibitors as mRNA adjuvants. This will prevent engagement of adverse TLR7 activation while avoiding the need to rely on pseudo-uridine modification of therapeutic mRNAs.

^I mRNA flu shots move into trials. Elie Dolgin. Nature Oct 21.
^II Moderna’s mRNA Vaccine for Seasonal Flu Enters Clinical Trials. Jennifer Abbasi. JAMA. 2021;326(14):1365. doi:10.1001/jama.2021.17499
^III Modifications in an Emergency: The Role of N1-Methylpseudouridine in COVID-19 Vaccines. Kellie D. Nance and Jordan L. Meier. ACS Central Science 2021 7 (5), 748-756. DOI: 10.1021/acscentsci.1c00197