Scientists at the Weizmann Institute of Science in Israel have discovered that sildenafil, the active ingredient in the erectile dysfunction drug Viagra, may help stop cancer from spreading.
Since its launch in 1998, Viagra has become one of the most recognizable drug brands in history, prescribed to millions of men, and some women, every year. In its first seven years alone, the medication was prescribed to over 23 million men.
In lab tests on human cells, researchers found that sildenafil interfered with the ability of cancer cells to access a key nutrient needed to survive and spread. Dr Ayelet Erez, a physician-scientist who led the study, said: "We have uncovered a new biological pathway that can be harnessed to interfere with cancer's ability to spread."
"Beyond their therapeutic promise, our findings highlight that cancer biology is shaped not only by mutations in tumor cells but also by the patient's metabolic state and by medications they are already taking for other conditions," Erez said.
While research remains in early stages and does not prove the drug can treat cancer, scientists say it could open an avenue to developing new treatments.
Laboratory testing on cells and mice
The study, published in Cancer Research, revealed that sildenafil interfered with the ability of cancer cells to absorb cholesterol, a vital ingredient for building cell walls. By blocking cholesterol from being released into the cell, sildenafil stopped cancer cells from constructing new membranes.
Researchers tested sildenafil on multiple types of human cancer cells in the laboratory, including breast, lung, and colon cancer. Sildenafil slowed their ability to move and multiply, with the strongest response seen in breast cancer cells.
When administered to mice with cancer, sildenafil dramatically reduced the number of tumors that spread to the lungs, cutting metastasis by more than half in some cases while having little effect on the original tumor itself.
In a separate laboratory experiment, researchers added statins to human cancer cells exposed to sildenafil. They found that statins also helped prevent cancer cells from building new cell walls, potentially helping to slow the spread of the disease.
Analysis of real world patient data
Researchers also analyzed 20 years of real-world health records from Clalit Health Services in Israel, covering nearly 5 million people. They compared cancer patients who took sildenafil to non-users, adjusting for factors such as age, socioeconomic status, and other medications.
When analyzing health records, researchers found that cancer patients who took sildenafil at least three times in the six months before diagnosis had a 26 percent lower risk of death within five years compared to non-users.
The survival benefit appeared dose-dependent. Patients with fewer than three sildenafil dispensations showed no significant survival advantage, but those with three or more did.
Patients taking sildenafil alongside statins fared even better, recording a 32 percent drop in risk of death. Among diabetic patients, who are more likely to have documented sildenafil use, the combination of sildenafil and statins was linked to a 41 percent reduced risk of death.
Additional health applications
Studies have also linked sildenafil to several other medical benefits beyond cancer research. In heart disease studies, research suggests sildenafil may aid recovery after heart attacks, improve blood flow to the brain in patients at risk of vascular dementia, and stimulate arteriogenesis, the growth of new collateral arteries to bypass blockages.
Brain health has also become a major focus area. A growing body of research is exploring sildenafil's potential in Alzheimer's disease to protect neurons and improve blood flow, though larger human trials are still needed.
Erez noted that the takeaway from the research extends beyond a single medication. "Our study underscores the importance of treating the whole patient, not just the cancer," Erez said.
