A new targeted therapy against cancer has shown impressive results in animal experiments. By using a beam of ultraviolet light to activate antibodies inside the tumour, a team at Newcastle University has created “magic bullets” that can use the body’s immune system to destroy tumours while leaving healthy tissue unharmed.

They use antibodies – the body’s own natural defences – that are injected into the tumour. But before injection, the antibodies are “cloaked” by attaching them to an organic oil that renders them ineffective. Once in place, a beam of ultraviolet light breaks up the cloaking chemical, bringing the antibody back to life. The antibody then binds to T-cells, the body’s defence system, and triggers them to target the surrounding tissue.

Antibodies are the big growth area in cancer therapy. Drugs such as Avastin and Herceptin have shown good results in shrinking tumours, and 20 antibody drugs have so far been licensed, with many more in the pipeline. But targeting them precisely and avoiding damage to surrounding healthy tissue have proved stumbling blocks. The team, led by Colin Self, believes that its technique could reduce or eliminate these problems.

Two papers published today in the journal ChemMedChem report that in a small animal trial, the technique elimated ovarian cancers in five out of six mice, and greatly reduced the tumour’s size in the sixth mouse.

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The body is not very effective at using its own defences to fight cancer, possibly because it fails to recognise the tumours as a threat. The aim of the technique is to activate the killer T-cells to attack cancer cells and destroy them.

There are risks in activating T-cells, as the failed human trial last year at Northwick Park Hospital in Harrow proved. In that trial, an experimental antibody treatment called TGN1412 caused such a huge response that six healthy human volunteers suffered serious injuries as their activated T-cells attacked almost every organ in their bodies.

The trial showed just how powerful boosting the T-cell response can be. The Newcastle technique ought to avoid these dangers because the T-cell response will be local – inside the cancer – and not general.

However, the process will require extensive testing in animals and human trials before it has any chance of reaching a cancer clinic. David Glover, an expert in antibody technology and in drug trials, estimated yesterday that even if all went well it would be a decade before such a product could reach the market.

Light-activated therapies have achieved some success against cancers, particularly skin cancers, but have been used previously to activate chemotherapy drugs, not T-cells. There are some limitations, as light cannot always reach internal tumours very easily. But Professsor Self suggested yesterday that in an operation to cut out a prostate tumour, for example, the method could be used at the end of the operation to destroy any remaining tumour cells that the surgeon had been unable to remove, and hence prevent recurrence.

The method offers a further refinement, in which the cloaked antibody is linked to a second antibody directed against the tumour in a “double whammy”. When uncloaked, it recruits T-cells to attack the tumour at the same time as the antitumour antibody also attacks it.

Professor Self said yesterday that his team had “very exciting” new results that confirmed the findings and that he was raising money for a human trial. This will be aimed at treating secondary skin cancers in patients who are already suffering cancers of the internal organs. The aim will not be to cure them, but simply to see if the skin cancers can be controlled, as a proof that the technique works in human beings.

Professor Self said: “I would describe this development as the equivalent of ultra-specific magic bullets. This could mean that a patient coming in for treatment of bladder cancer would receive an injection of the cloaked antibodies. She would sit in the waiting room for an hour and then come back in for treatment by light. Just a few minutes of the light therapy directed at the region of the tumour would activate the T-cells causing her body’s own immune system to attack the tumour.

“While our work indicates that sunlight doesn’t activate these antibodies, patients may have to be advised to avoid direct sunlight for a short time.”

BioTransformations Ltd, the company set up by Professor Self to develop the technology, hopes to begin clinical trials on patients with secondary skin cancers early next year.

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