A clinical trial of a messenger RNA vaccine against cancer is the latest study to highlight the potential of these drugs to combat disease.
The US biotechnology company Moderna and the US pharmaceutical business Merck announced this week that their mRNA vaccine resulted in significantly improved outcomes for patients with melanoma.
When combined with another anti-cancer drug, their personalised vaccine led to a 44 per cent reduction in the risk of recurrence or death, compared with using the drug alone.
The findings come in the wake of the coronavirus pandemic, when mRNA vaccines were, for the first time, used around the world and prevented millions of deaths from Covid-19.
While Covid-19 mRNA vaccines help to prevent disease, cancer mRNA vaccines, which represent a form of immunotherapy, are used to treat people who already have cancer.
In some forms of immunotherapy, the patient is given laboratory-made antibodies to combat the cancer, while with the mRNA vaccine, his or her cells receive genetic instructions in the form of mRNA to produce particular proteins called antigens that, in turn, activate the immune system to fight disease.
'Latest results are promising'
Christian Ottensmeier, a professor of immuno-oncology at the University of Liverpool in the UK, said that the range of new cancer vaccines and related treatments being developed made it an “amazing” time to be working in the field.
He indicated that the latest results from Moderna and Merck were especially promising.
“This is where we thought we should be and we are finally there,” he said. “This is proof of principle of this approach. It is not just scientists [making predictions], it makes people better or stops them from getting worse,” he said.
While mRNA vaccines became widely known during the Covid-19 pandemic, for many years before the coronavirus emerged work was taking place to develop them to combat other illnesses.
For example, before the pandemic, BioNTech, the German biotechnology company that became well known thanks to its successful mRNA Covid-19 vaccine, began clinical trials with an mRNA cancer vaccine that encodes cancer-specific antigens, the immune response to which can destroy a patient’s cancer.
Early results of an mRNA vaccine against melanoma proved promising, with the treatment shrinking or stabilising the melanoma in almost half of the trial participants.
This BioNTech trial involved an “off-the-shelf” vaccine while Moderna and Merck’s new results come from a “personalised” vaccine, which is specifically tailored to the genetic makeup of the patient’s cancer.
BioNTech too has developed personalised cancer vaccines.
In the Moderna and Merck study, the mRNA vaccine was used in conjunction with another type of immunotherapy drug called a checkpoint inhibitor and was found to significantly improve outcomes, compared with using the checkpoint inhibitor alone.
The findings are especially significant because they involved a randomised trial, which prevents biases from affecting the results.
“The recurrence rate was reduced significantly, so it is likely it is a true observation,” Prof Ottensmeier said.
“Moderna, they are the first, but I don’t think they will be the only ones. I believe it is almost certain vaccines will play a role in the management of cancer.”
These may not just be mRNA vaccines, with DNA vaccines having recently been described in a scientific paper by researchers in China and the US as “a promising immunotherapy strategy to activate the host immune system against lung cancer”.
Prof Ottensmeier said it was “the expectation” that vaccine platforms other than mRNA would also prove important in combating cancer.
Aside from being used to prevent Covid-19 and, it seems likely, to treat cancer, mRNA vaccines may be employed against a range of infectious diseases such as influenza, rabies and zika, which are all caused by viruses.
Prof Ian Jones, a professor of virology at the University of Reading in the UK, who has closely observed the development of mRNA vaccines against a wide variety of conditions, said such vaccines offered particular advantages.
Synthesising mRNA vaccines of any kind tends to be much simpler than making other types of vaccine, Prof Jones said.
He described mRNA vaccines as being “simply purified chemicals” that “can be made more or less anywhere”, including in developing nations where investments in manufacturing plants may be less significant.
Producing other types of vaccines often involves a biological process, such as growing microorganisms from which substances are purified, creating a risk of contamination.
“For a number of reasons, making any biological vaccine is fraught with difficulty,” Prof Jones said.
“There is cost, there is scale, there are many biological processes and a lot of safety requirements to ensure what you are using doesn’t contain anything [that should not be there] that has got through into the final product.”
The pandemic sped up the development of mRNA vaccines against a variety of conditions in part, Prof Jones said, because it showed such vaccines were fundamentally safe, so from now on, it may be easier for them to satisfy regulatory requirements.
“The safety issue of whether it’s safe to inject 0.1g of RNA into your arm, that has been proven since the pandemic,” he said.
“It is accepted all RNA vaccines will be safe at the point of delivery. There is nothing to stop them from rolling out for any number of targets and diseases.”