Phase I study data suggest that the treatment is safe and can improve erectile function in some men



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ORLANDO—Injections of the Maxi-K gene into the penis of men with erectile dysfunction (ED) appears to be safe and shows potential for improving erectile function, data from a phase I study suggest.


Unlike conventional oral therapies for men with ED, Maxi-K therapy does not require prior planning and thus fosters sexual spontaneity, and it can be used by men taking heart medication.


The first phase of the gene transfer trial ended in June 2006. The trial design was a single-dose escalation study in men aged 18-80 years with moderate to severe ED. All men either were not successful or did not wish to continue other forms of ED therapy. A total of 11 men completed the trial at two New York sites (Mount Sinai School of Medicine and New York University School of Medicine). Three men received 500 µg Maxi-K, three received 1,000 µg Maxi-K, three received 5,000 µg Maxi-K, and two received 7,500 µg Maxi-K. The gene was delivered via naked DNA plasmid transfer.


The researchers now have two year follow-up data for nine men.  One subject, who had no adverse events during the trial, did not return for the one year visit.  Another subject who had a previous radical prostatectomy who did not respond to therapy had penile prosthetic implant. The researchers observed no reports of abnormalities in any of the disease parameters examined in the study. The treatment was associated with no treatment-related adverse events or onset of any hematological, autoimmune, or neoplastic disease, or CVD.


Although results are promising, they are not adequate to determine overall efficacy. “The point is that gene transfer using naked DNA plasmid as a vector is totally safe,” Dr. Melman said. “So in addition to showing some early efficacy in our preliminary reports, we can now report that, over two years, that the gene transfer is safe and people don’t have to worry. “We are now doing a Phase I-b trial at three higher doses in 12 men.”


In this trial, men will receive doses ranging from 8,000 to 16,000 µg of the gene. The injections are given into the shaft of the penis.


“We think the market for this is anyone with erectile dysfunction,” Dr. Melman said. “In animal models we have seen that this can reverse the effect of aging on erectile function.  Since the principle cause of erectile dysfunction is aging, we think we can use it as a way of restoring the age-related decline in erectile ability.”


Dr. Melman and his colleagues also explored whether increased erectile function enhances other areas of sexual behavior. At the AUA meeting, they presented data on a study looking at male cynomolgus monkeys with ED who were treated with four, weekly instillations of  the Maxi-K gene transfer. The researchers observed the monkeys in the presence of estrogen-implanted females. The male monkeys showed “dramatic changes” after gene transfer, including an increase in the number of partial and full erections and a twofold increase in erection duration.