Erectile dysfunction drug could enhance delivery of herceptin to brain tumours

A drug currently approved to treat erectile dysfunction could significantly improve the delivery of the anti-cancer drug Herceptin to certain hard-to-treat brain tumours, according to a new study at Cedars-Sinai’s Maxine Dunitz Neurosurgical Institute.

The research could help doctors improve treatments for lung and breast cancers that have metastasized to the brain.

Even if a cancer is susceptible to drugs, these drugs must penetrate the “blood-brain barrier” if they’re to treat cancer that’s metastasised to the brain.

“Mother Nature created this barrier to protect our brains from dangerous substances, but here we need to get through the barrier to deliver the drugs, and that’s a problem,” says study author Dr. Julia Y. Ljubimova.

Dr. Keith Black, lead research scientist on this project, has studied the blood-brain barrier for about two decades.

Research conducted by his team found that the erectile dysfunction drugs sildenafil (Viagra) and vardenafil (Levitra), which inhibit the enzyme phosphodiesterase 5 (PDE5), could increase the permeability of the blood-brain tumour barrier and boost the effectiveness of the chemotherapy drug doxorubicin.

“No matter how effective against cancer a chemotherapeutic agent may be, it can have little impact on brain tumours if it cannot cross the blood-brain tumour barrier. As we find new drugs that are able to target these tumour cells, it is imperative that we develop better ways to enable the medications to reach their targets,” he said.

In the current study, the researchers examined whether PDE5 inhibitors might also increase the blood-brain tumour barrier’s permeability to Herceptin- a monoclonal antibody used to treat lung and breast tumours that are positive for HER2/neu.

Herceptin is a large molecule that does not easily cross the blood-brain tumour barrier, a limitation that severely reduces its effectiveness at treating brain metastases.

The researchers first measured vardenafil’s effects on the permeability of the blood-brain tumour barrier.

Using a mouse model, the scientists showed that vardenafil led to a two-fold increase in the amount of Herceptin that reached brain metastases of lung and breast cancers.

Next, they examined whether this increase in blood-brain barrier permeability improved Herceptin’s effectiveness at treating these brain metastases by giving mice vardenafil in tandem with Herceptin.

The results showed that the combination of vardenafil plus Herceptin boosted mean survival by 20 percent, compared to Herceptin alone (7218 days versus 599 days).

The study was published in the journal PLoS ONE.