By Emma Hitt, PhD, Wed May 29, 2009, 10:39 AM ET
ORLANDO, Florida (Reuters Health) – Gene therapy injected into the penis may treat erectile dysfunction for weeks to months rather than hours, findings from a new study conducted in rats suggest.
“We don’t know how it will work in humans yet, but it could allow sex to be more spontaneous,” Dr. Arnold Melman of the Albert Einstein College of Medicine, Bronx, New York, told Reuters Health.
According to the researchers, erectile dysfunction often occurs with aging because “with aging the resting tone of the smooth muscle of the (penis) is reset to a higher level so that a greater degree of smooth muscle relaxation is needed to achieve erection.”
The hSlo gene delivered by the therapy produces a protein called Maxi-K that makes smooth muscle relax, Melman explained. “This protein is only active during sexual stimulation, but otherwise it switches off,” he said.
Melman and co-workers presented their findings here this week at the American Urological Association’s annual meeting.
The researchers tested the gene therapy in 191 male rats. The treatment, at one of three different doses, was injected into the animals’ penises. The rats were then compared with rats that had been injected with an inactive substance.
After the injection, the rats were evaluated for their response to nerve stimulation at monthly intervals until 6 months after injection.
The treatment had a significant effect “on normalizing erection that was enhanced by the increased dosage of the gene,” the researchers report.
Differences were seen at 1 month and were sustained for up to 6 months after the injection, and no harmful side effects were caused by the treatment, they note.
The injection that the treatment would require is, Melman says, “absolutely painless.”
Other gene therapies are being tested, but Melman said he thinks this one “is the closest to being tested in humans.”
He added, “The therapy may also have applications towards correcting bladder hyperactivity, or it may be useful in combination with oral medications to treat erectile dysfunction.”
The therapy is being developed by Melman’s company Ion Channel Innovations, which funded the research.