Scientists have believed for several decades that adenovirus vector platforms would work as a new route for delivering vaccines. However, before coronavirus, they were mainly developed for infections that were very difficult to tackle, like HIV. This complexity means that, largely, they had not yet reached the point of being tested in humans to gauge their safety and effectiveness, although there had been a handful of Ebola trials using a different viral vector.
The advent of coronavirus, which saw the Oxford-AstraZeneca jab (as well as the Johnson & Johnson vaccine, which uses similar technology) developed, tested, and manufactured at scale and at record speed, has changed all that – raising hopes of other breakthroughs.
These breakthroughs could also bring riches to the team at Vaccitech, its backers, and its founders Oxford professors Sarah Gilbert and Adrian Hill, as the company retains the rights to the ChAdOx platform for the diseases it is working on. AstraZeneca has the rights to the Covid jab, and Oxford University the rights to the technology used for other diseases.
Scientists say that ChAdOx is so promising for a host of diseases because of how it is designed. Like the mRNA coronavirus vaccines, it is “plug and play” – the backbone of the vaccine remains the same, while the detail of the disease it is showing the immune system can be altered.
The way ChAdOx works is by using the chimp virus, modified so as not to infect humans, to deliver genetic instructions to the body’s own cells. These genetic instructions drive the body to make copies of an antigen – for example, coronavirus – prompting an immune response: a practice run, preparing it for the real deal.
The key thing is that these genetic instructions can be changed. As such, scientists have compared viral vector vaccines to a postman with a blank letter, waiting for the address – the targeted disease – or a cake waiting for personalised icing.
This is completely different to how most existing vaccines work. They introduce either a killed or weakened version of the virus, or fragments of it, to the body, to teach it how to respond, meaning that every vaccine is totally different.
For treating cancer, using ChAdOx is at an earlier stage than it is for preventing infectious disease, but it has clear potential, the researchers say. This week, the team showed positive results in mice, using ChAdOx and a booster jab using a different viral vector to tackle non-small cell lung cancer.
In combination with immunotherapy, which uses the body’s immune system to fight cancer, it decreased tumour size and improved survival.
The research, published by Oxford and the Ludwig Institute for Cancer Research in the Journal for ImmunoTherapy of Cancer, has paved the way for human trials to begin later this year.