Viagra could be medics’ secret weapon against breast cancer, Israeli research finds

Dr Yarden Ariav and Professor Ayelet Erez (Courtesy)[Missing Credit]

The researchers, led by Professor Ayelet Erez and Dr Yarden Ariav, say there are many benefits to repurposing a drug like Viagra, which has already been approved, although he cautions that there is still a long way to go.

"It's an amazing study, and it gives hope for the future," he told the JC. "But I don't want female patients to start taking Viagra, and I don't want male patients to go to their doctor and ask for Viagra against cancer. We're not doctors, we're scientists."

Experiments so far have involved mice rather than humans, and it could still take years before sildenafil is prescribed for cancer patients.

But establishing that Viagra starves cancer cells of the cholesterol they need is a significant breakthrough that could help not only patients with breast cancer, but also those with colon, lung and other cancers.

"No one ever showed this connection between Viagra and cholesterol in the context of cancer, so I think it is a breakthrough both clinically and especially metabolically because we discovered another mechanism that was not known before," said Ariav.

He and fellow researchers in Erez’s lab at the Weizmann Institute were looking for genes that might make cancer cells easier for the immune system to spot and more responsive to immune-checkpoint treatments.

One gene that stood out was phosphodiesterase type 5, or PDE5a, which also happens to be the gene that is targeted by Viagra.

Viagra blocks the PDE5a enzyme’s activity, allowing a build-up of a small messenger molecule called cGMP.

In the penis, cGMP relaxes blood vessels and lets more blood flow in, which helps produce an erection.

In cancer cells, the same cGMP signal can interfere with the availability of cholesterol and how the cells move and spread, making metastasis harder.

In both cases, taking a Viagra pill operates the same "biological switch".

Researchers established a connection between the cGMP messenger molecule and the way cancer cells use cholesterol, which could help explain why some cancer cells become less able to move and spread. 

Ariav said: "We showed in our research that sildenafil inside cancer cells causes cholesterol to become less available for the cancer cells to metastasise – to generate new energy and to move from one place to another. It means the cancer cells cannot utilise this cholesterol for their needs."

Cholesterol is particularly important for cancer cells seeking to break away from the primary tumour, migrate throughout the body and invade distant organs.

When their access to cholesterol is disrupted, these cells have a harder time forming metastases – new tumours that form when cancer spreads to other parts of the body.

The researchers also found that combining drugs from the Viagra family with statins, another widely used class of drugs which reduce cholesterol production in the body, may be even more effective at restricting metastasis.

Statistical analysis of more than five million members of Clalit, Israel's biggest health provider, revealed significantly improved survival among cancer patients who had taken sildenafil to treat erectile dysfunction, particularly when it was combined with statins.

Erez, who runs the lab where the research took place, said: “We have uncovered a new biological pathway that links a well-known signalling molecule to cholesterol regulation within cells, and shown how this pathway can be harnessed to interfere with the ability of cancer cells to form metastases.”

She said the findings showed cancer biology is shaped not only by mutations in tumour cells but also by the patient’s metabolic state and by medications they are already taking for other conditions.

“This is still a long way from clinical use," said Ariav. "We need much more research to figure out the right doses, timing, and whether it can be safely combined with chemotherapy or immunotherapy. Those combinations are not simple, even when we already know the drugs individually.

"But I am optimistic, because the mechanism we found is strong. We showed it in several systems, including cell models and mice, and we also saw a strong correlation in real patient data from Israel between Viagra use and better cancer survival.

"So the findings are exciting, but they are still far from routine clinical practice, and it is important to make that clear so patients do not go to their doctors and ask to use it on their own.”

The team have just published an article outlining how PDE5a inhibition restricts cancer metastasis in the journal Cancer Research.

However, their research was set back by months when their lab suffered severe damage in a direct hit by an Iranian ballistic missile in June 2025.

Valuable samples were lost, and the main instruments used to measure metabolic activity and protein activity had to be replaced.