The first human trial of gene transfer therapy for erectile dysfunction (ED) indicates that gene therapy that lasts for months and eliminates the patient's need for on-demand drugs (such as Viagra and Cialis), could become the future treatment of choice for this common problem, according to a paper in the most recent issue of Human Gene Therapy.

Lead author Arnold Melman, MD, professor and chair of the Department of Urology at Albert Einstein College of Medicine and Montefiore Medical Center, says, "This is an exciting field of research because current treatments for men with erectile dysfunction, whether pills or minimally invasive therapies, must be used 'on demand', thereby reducing the spontaneity of the sexual act."

Erectile dysfunction affects more than 50 percent of men aged 40 to70 and 70 percent above age 70, according to the Massachusetts Male Aging Study.

Dr. Melman and two study centers worked with 11 men and administered various doses of a transfer gene called hMaxi-K. "While this phase 1 safety trial was not designed to provide efficacy answers, one patient in each of the higher dose groups (5000 and 7500 micrograms) reported clinically significant and sustained improvements in ED. And, there have been no adverse effects with the patients in the study, so it has been proven to be safe," he adds.

Because there has been widely publicized adverse results using viruses as agents to transfer genes into humans, Dr. Melman has chosen to transfer the hMaxi-K gene using "naked DNA," a form of circular DNA which remains independent and does not integrate with chromosomal DNA in the muscle cells.

"The hMaxi-K stimulates potassium ion transfer in the smooth muscle cells of the penis," says Dr. Melman. The hMaxi-K gene works by creating additional potassium channels (the chemical symbol for potassium is 'K') in the smooth muscle cell of the penis. This relaxes the muscle and allows blood flow required for an erection.

"Because this novel therapeutic approach of ion channel therapy works on smooth muscle, it is also promising for overactive bladder disease," adds Dr. Melman.