Melanoma immune system drug "extremely encouraging"
US researchers have managed to boost patients' immune systems to help them beat melanoma skin cancer.
In the first part of a phase II clinical trial to test a new drug, denileukin diftitox (also known as DAB(389)IL2 or ONTAK), five out of seven patients with advanced disease saw their cancers stop growing or shrink.
The two other patients in whom the disease progressed were on a lower dose of the drug. All the patients are still alive after 12 months.
Malignant melanoma is one of the most aggressive cancers and is notoriously hard to treat.
The study, conducted by the University of Kentucky in the US, altered the immune system's natural regulatory process to boost the levels of a certain type of disease-fighting white blood cell called a T-cell.
When healthy, the number of disease-fighting T-cells in the body is controlled by another type of T-cell, 'regulatory' T-cells or 'Treg' cells, to prevent the immune system from working too hard.
ONTAK is made by attaching part of the diphtheria toxin - the molecule secreted by the bacterium that causes diphtheria - to a human immune protein called interleukin 2 (Il-2).
The resulting molecule is able to bind to Treg cells and destroy them.
Using the drug, the researchers were able to reduce the number of Treg cells and so increase the number of disease-fighting T-cells in the bloodstream.
This was shown to either halt the cancer growth, or in some cases actually cause the cancer to shrink.
"To our knowledge, this is the only trial to study the effects of Treg depletion in human cancer patients," said lead researcher Dr Jason Chesney.
"From the results, we conclude that depleting Treg cells in patients with melanoma may allow the immune system to be activated successfully to kill cancer cells.
"We also believe that, in the future, immunotherapies that depend on depleting Treg cells may prove to be useful in all types of cancer," he added.
Henry Scowcroft, science information officer at Cancer Research UK, said: "This is very early work with very ill patients, but the results are extremely encouraging. There have been several similar findings in recent years.
"Taken together, these advances suggest that immunotherapy -? using the body?s own immune system to fight disease - is finally starting to live up to early expectations.
"Cancer Research UK hopes that larger trials will confirm these exciting results.
"We're looking forward to new developments in this field - both from our own scientists and other cancer researchers around the globe."
The study was presented at a European cancer research meeting in Prague.