Researchers at Cedars-Sinai Medical Center's Maxine Dunitz Neurosurgical Institute have found that drugs commonly prescribed for erectile dysfunction open up a mechanism called the blood-brain tumour barrier. The study on mice also found that this method increased delivery of cancer-fighting drugs to malignant brain tumours.
Viagra (sildenafil) and Levitra (vardenafil) are known as PDE5 inhibitors because they block an enzyme, phosphodiesterase5, which interrupts a series of biochemical events that cause the decreased blood flow of erectile dysfunction.
The new study found that similar biochemical interactions in the small vessels of the brain play a significant role in the blood-brain tumour barrier, which impedes delivery of anti-tumour drugs into brain tumours.
PDE5 inhibitors were found to open the barrier and increase drug transport in this early animal study.
Although the normal blood-brain barrier, which regulates access to the brain from the bloodstream, shares many characteristics with the blood-brain tumour barrier, the signalling mechanism blocked by PDE5 inhibitors is unique to the blood-brain tumour barrier.
This allows the PDE5 inhibitors to selectively increase drug transport to malignant brain tumours without affecting normal brain tissue.
According to the researchers, these findings may have significant implications in improving drug delivery to brain tumours in patients.
"This is the first study to show that oral administration of PDE5 inhibitors increases the rate of transport of compounds across the blood-brain tumour barrier and improves the effectiveness of the anti-tumour drug adriamycin in the treatment of brain tumours in a rat model," said neurosurgeon Keith L. Black, M.D., chairman of the Department of Neurosurgery at Cedars-Sinai Medical Center and director of the Maxine Dunitz Neurosurgical Institute.
"We chose adriamycin for this study because it is one of the most effective drugs against brain tumour cell lines in the laboratory but it has very little effect in animals and humans because it is unable to cross the blood-brain tumour barrier.
"The combination of vardenafil and adriamycin resulted in longer survival and smaller tumour size," he added.
The study has been published online ahead of print in the journal Brain Research.