TUESDAY, May 20 (HealthDay News) -- Gene therapy may be a way to treat erectile dysfunction in men who do not respond to pills such as Viagra, researchers report.

Maxi-K gene therapy is a gene transfer that improves erectile dysfunction. Two studies using the gene were presented Tuesday at the American Urological Association's annual meeting, in Orlando, Fla.

"Gene transfer technology has the potential for long-term improvement for erectile function," lead researcher Dr. Arnold Melman, a professor of medicine at Albert Einstein College of Medicine in New York City, said during a morning teleconference Tuesday.

"The market for erectile dysfunction is quite large," Melman said. "And medications such as Viagra don't work very well in 40 percent of men."

Melman noted that a recent survey showed that 50 percent of urologists would consider switching their patients from their current medications to gene transfer treatment. "So, we think this will be well-accepted by physicians and patients," he said.

Results of a phase I trial testing gene transfer in 11 men with erectile dysfunction who had failed other therapy showed that gene transfer was safe and also had restorative effects. Four different doses were tried during the trial. Men receiving the highest dose showed improvement for up to six months, Melman said.

"These men had normal sexual function for six months and then went back to the way they were," Melman said. He added that two doses a year would be enough for most men to maintain their normal sexual function.

During two years of follow-up, none of the men reported any abnormalities after the gene transfer. The procedure was safe, and no adverse effects were seen, Melman said.

Based on these findings, Melman's group is moving on to new trials and hopes to have a product on the market within two years.

In another trial, four monkeys were fed a high-fat diet, which reduced their sex drive. After the monkeys received a Maxi-K gene transfer, they became friskier.

In addition, the number of partial and full erections increased about fivefold, the researchers found. Also, the frequency of ejaculations increased among the monkeys that received the gene transfer. Moreover, the gene transfer affected how the monkeys behaved with female monkeys.

"The most fascinating thing is there was the increased socialization," lead researcher George J. Christ, a professor of urology and head of the Program in Cell Tissue and Organ Physiology at the Wake Forest Institute for Regenerative Medicine, said during Tuesday's teleconference. "After receiving a gene transfer and regaining sexual function, they felt better about themselves."

More information

For more on erectile dysfunction, visit the National Institute of Diabetes and Digestive and Kidney Diseases.

SOURCES: May 20, 2008, teleconference with Arnold Melman, M.D., professor, medicine, Albert Einstein College of Medicine, New York City; George J. Christ, Ph.D., professor, urology, and head, Program in Cell, Tissue and Organ Physiology, Wake Forest Institute for Regenerative Medicine, Winston-Salem, N.C., May 20, 2008, presentations, American Urological Association annual meeting, Orlando, Fla.

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