Gene therapy won’t replace Viagra—yet

Older men who want to revive flagging sexual function have turned in large numbers to Viagra. For a few hours, the pills restore the vascular system’s sensitivity to nitric oxide, a compound that facilitates erections. However, Viagra doesn’t work in all men, and it also can aggravate heart conditions in some people. That’s why several university teams have been investigating gene therapy as a different way to cure impotence.