LJUBLJANA, SLOVENIA – Encouraging safety and immunogenicity results reported from phase 1 studies of the first mRNA vaccines against the potentially pandemic H10N8 avian influenza and H7N9 influenza viruses suggest a bright future for what appears to be a breakthrough technology in vaccine development.
“We have developed an mRNA platform that has the potential to be quite applicable to the vaccine space. It’s an agile platform with the potential for relatively rapid development of vaccine antigen without the use of dedicated facilities, or growth in eggs, or insects, or mammalian cells,”, said at the annual meeting of the European Society for Paediatric Infectious Diseases.
“We now have a platform that is relatively plug and play. If one has the mRNA sequence that you’re after to produce the protein that you’re after, it is a relatively repetitive process somewhat irrespective of the goal of the protein that you’re going to manufacture. We’re introducing an mRNA into our cellular machinery – the destination is the cellular ribosome – where it hopefully is able to be translated with fidelity into the target protein. Essentially it’s like the biological equivalent of a software hack for our own cells,” explained Dr. Panther, who is director of clinical development for infectious diseases at Moderna, in Cambridge, Mass.
Indeed, Moderna has numerous ongoing or recently completed phase 1 clinical trials of mRNA vaccines developed to protect against a raft of viral infections: respiratory syncytial virus, cytomegalovirus (), zika, chikungunya ( ), human metapneumovirus, and parainfluenza virus 3, as well as the aforementioned H10N8 and H7N9 influenza viruses. And an mRNA varicella zoster virus vaccine is in preclinical studies.
The mRNA vaccines closely mimic native viral infections, eliciting both B- and T-cell responses.
Moreover, the company also has ongoing phase 1 studies of mRNA-based cancer vaccines – therapies targeting solid tumors and lymphomas – as well as mRNA-directed increased production of relaxin as a treatment for heart failure and of vascular endothelial growth factor to treat myocardial ischemia.
“For the purposes of my company, the desired protein at this juncture could be an antibody, it could be a tumor antigen, it could be an enzyme that will replace an enzyme that’s lacking in somebody with an inborn error of metabolism. Or it could be a vaccine antigen target,” Dr. Panther said.
In addition to highlighting the results of the two phase 1 proof-of-concept studies of mRNA vaccines targeting the feared H10N8 and H7N9 influenza viruses, she presented interim results of an ongoing 1-year study of an mRNA vaccine that contains two antigens simultaneously targeting human metapneumovirus (hMPV) and parainfluenza virus 3 (PIV3).
“The rationale behind this study is that, taken together, these are two viruses that are responsible for a fair bit of disease burden in terms of lower respiratory tract infections and hospitalizations in children [younger] than 12 months of age, which will be the target population,” the infectious disease specialist noted.
The early positive results of the mRNA influenza vaccine studies were of particular interest to her audience of pediatric infectious disease specialists. Since the first human H7N9 infections were reported in China in 2013, five outbreaks have occurred involving more than 1,500 documented infections, resulting in more than 600 deaths. And ever since the virulent H10N8 avian influenza virus popped up on the radar in 2013, infectious disease physicians the world over have been waiting for the other shoe to drop.
There is obvious appeal to a novel, precise, and rapidly scalable technology such as that promised by intracellular delivery of mRNA in order to ramp up high-volume production of effective vaccines in the face of a looming pandemic threat. Elsewhere at the meeting, it was noted that, during the H1N1 pandemic of 2009, it took 6 months for the first vaccine doses to become available using current antiquated egg-based production methods. Another 2 months elapsed before the necessary millions of doses were produced.
The details of the two phase 1 studies of the mRNA vaccines against H7N9 and H10N8 influenza have recently been published (). The vaccines, delivered in the conventional manner via injection into the deltoid muscle, were well tolerated, with the most common adverse events being the familiar ones: injection site pain, erythema, headache, fatigue, and myalgia. The immune response was robust and durable.
In response to an audience question, Dr. Panther said the mRNA vaccines are amenable to development as intranasal formulations.
The ongoing 12-month, phase 1, dose-ranging study of the mRNA hMPV/PIV3 virus vaccine includes 124 healthy adults at three U.S. sites who received two vaccinations on days 1 and 28. One month after a single vaccination, hMPV neutralizing antibody titers were 6.2-6.4 times those in the placebo arm; PIV3 neutralization titers were increased 3.3-fold. The second injection didn’t further boost antibody titers, suggesting that, at least in this study population of preexposed adults, a single vaccination is sufficient.
The use of mRNA technology has been a long time in coming. Dr. Panther explained why: “It’s a big trick to take an mRNA that by its own nature is a pretty fragile molecule and to get it past the degrading enzymes, like RNAses, that are out to chew it up immediately, and then to sneak it across the cellular membrane and into the cytoplasm, all the while avoiding the innate immune responses that exist solely to recognize RNA that looks foreign and chew it up.”
Moderna has accomplished this using a proprietary lipid nanoparticle delivery system.
“Essentially it’s a lipid shield that surrounds the mRNAs and ushers them past those enzymes and past the innate immune response that would otherwise destroy them,” according to Dr. Panther.
She and her colleagues believe they may eventually be able to change the nucleotide sequence of their manufactured mRNAs in order to expand the immunogenicity epitope and achieve a stronger immune response than would result from natural infection.