Cancer therapy causes 'avalanche of cell death'

Antibody drugs that stop new vessels forming in tumours have already been developed and marketed — but generally tumours can adapt and rely on back-up mechanisms to get blood flowing again.

A team from Hull University and ETH Zurich have now joined these antibodies to a photosensitive molecule.

The drug is administered intravenously as normal and is localised to the tumour site by the antibody, which attaches to a protein specific to the blood vessels there. The antibody stops the growth of new vessels — but, in addition, light is applied to the tumour, which activates the photosensitive molecule and leads to a cascade that damages existing vessels.

‘The photosensitiser absorbs red wavelength light and it goes into an excited state, so it’s got to get rid of that energy somehow and the way it does that is to interact with oxygen, converting it to something much more cytotoxic — which is bad for any cells in the immediate environment,’ Dr Ross Boyle of Hull told The Engineer.

Because this new method has two levels of targeted action — the immune one and the photodynamic one — they witnessed a total shutdown of blood supply, rapidly followed by complete ablation of the tumour in mice.

This also means that the photo-immune approach should be more effective, even at smaller doses, improving outcomes and reducing potential side effects to patients.

‘With normal PDT [photodynamic therapy] approaches, without the targeting, they will make the patients photosensitive for anything up to a couple of weeks,’ Boyle said.

The team delivered the phototherapy using bundles of fibre optics, but it is currently only effective to a certain depth and so is suitable for skin tumours, as well as those in body cavities. In fact, Boyle said it could be used to treat lung cancer in conjunction with an endoscope.

The technology is now being referred to the transitional division of Cancer Research UK for funding, with clinical trials hopefully following later in the year.