Eli Lilly’s Cialis (tadalafil) is best known as an erectile dysfunction (ED) therapy. But University of Manchester scientists are interested in proving it can reverse heart failure, and they have promising evidence from a sheep study that they may be right.
Cialis slowed the progression of heart failure in sheep models of the disease and reversed breathlessness, one of the most troublesome symptoms, the researchers reported in the journal Scientific Reports.
The findings may not be a total surprise. This class of drugs, PDE5 inhibitors, which also includes Pfizer’s Viagra and Bayer’s Levitra, was originally developed for cardiac disease. Then the scientists developing Viagra discovered the drug relieved ED.
“We do have limited evidence from human trials and epidemiological studies that show Tadalafil can be effective in treating heart failure,” said the study’s lead author, Andrew Trafford, in a statement. “This study provides further confirmation, adds mechanistic details and demonstrates that Tadalafil could now be a possible therapy for heart failure.” It’s possible that patients taking Cialis for ED have already unknowingly benefited from the drug’s protective effect on the heart, he added.
Heart failure is characterized by the heart’s inability to pump enough blood to meet the body’s needs, which can lead to fluid accumulation in the lungs and cause the feeling of being short of breath. Trafford’s team used sheep to study the effects of PDE5 inhibition because their hearts are similar to human hearts.
After inducing heart failure in the animals, the team administered Cialis at a dose similar to what’s used to treat ED in people. They observed that Cialis restored the heart’s ability to respond to adrenaline—and that improved its ability to pump blood.
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Most heart failure medications can slow the progression of the disease and lower the probability of deadly cardiac events. But actually reversing heart failure is difficult, especially without surgery or the assistance of medical devices.
Various groups of scientists are exploring methods for reversing heart failure with drugs. A team at Imperial College London recently found that blocking the MAP4K4 protein could reduce heart damage. In a 2017 Nature study, Baylor College of Medicine researchers discovered that the Hippo signaling pathway can prevent damaged heart muscle from repairing itself, and by blocking it, they restored pumping ability in mouse hearts.
But the University of Manchester researchers believe the best strategy may be to return to the original goal in PDE5 inhibition.
“We seem to have gone full-circle, with findings from recent studies suggesting that [ED drugs] may be effective in the treatment of some forms of heart disease—in this case, heart failure,” said Metin Avkiran, associate medical director of the British Heart Foundation, which funded the study. "The evidence from this study, that a Viagra-like drug could reverse heart failure, should encourage further research in humans to determine if such drugs may help to save and improve lives.”