Researchers are arguing that the certain drugs, including the erectile dysfunction drug Viagra, could be used as cancer treatments, reports MedicalXpress. This theory is based on a range of pre-clinical and clinical data that show how the drugs function.

The publication, which can be found here, comes from the Repurposing Drugs in Oncology project, which is set up to investigate how existing drugs could be re-purposed to become anti-cancer drugs. The project is a collaboration between Belgium, the Anticancer Fund, and GlobalCures. It is designed to overcome current funding issues involved in developing extremely expensive new cancer drugs by investigating which existing treatments could potentially also be used on cancers.

A range of drugs that includes Viagra, Cialis, and Levitra, has been identified as possible anti-cancer treatments. These drugs are all selective phosphodiesterase 5 (PDE5) inhibitors. They work by relaxing the smooth muscles in blood vessels to encourage blood flow. Viagra has already been re-purposed from its original function of treating male erectile dysfunction to being used on patients with pulmonary hypertension (high blood pressure). This is possible because the same process of improving blood flow can treat both conditions. It is now thought that this drug could again be successfully re-purposed for a second time in patients with some forms of cancer, such as glioblastoma multiforme, which is a brain cancer with few treatment options available.

The researchers hypothesise that the PDE5 inhibitors could be used in conjunction with existing anti-cancer drugs called checkpoint inhibitors. Checkpoint inhibitors help to regulate the body’s immune response to improve cancer symptoms, but currently face issues due to their high cost and the limited effect they can sometimes have. By combining checkpoint inhibitors with PDE5 inhibitors it is hoped that the treatment’s effectiveness will be improved.

PDE5 inhibitors may also be helpful for treating brain tumours. This is because current tumour treatments struggle to cross the barrier between the blood and brain. However, there is some evidence that PDE5 can increase the permeability of this barrier and help drugs to cross over into the brain to reach the site of the tumour.

In these two ways, PDE5 inhibitors may be helpful in cancer treatments. These drugs are particularly good possible treatment options because they are widely used, cheap to produce, and have low-toxicity. Some small studies are currently being carried out to assess their suitability for re-purposing into a cancer treatment, but larger studies should be carried out to confirm the researcher’s hypotheses. Other common and cheap drugs that are being investigated as possible re-purposed anti-cancer drugs include anti-fungal medications and beta-blockers.

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