Injected gene regulates ion channel activity and affects smooth muscle function.

A single injection directly into the penis of men with erectile dysfunction of a gene that regulates ion channel activity and affects smooth muscle function was shown to be safe and promising for treating erectile dysfunction.

Researchers report that, “the promising primary safety outcomes of the study and preliminary indications of effectiveness provide evidence that hMaxi-K gene transfer is a viable approach to the treatment of ED, and that further studies investigating the efficacy of hMaxi-K in patients with ED should be performed.”

The trial included 11 patients who received a single injection of different doses of hMaxi-K , which contains the human gene hSlo packaged in a naked DNA plasmid delivery vector. hSlo encodes a subunit of the Maxi-K potassium channel, which plays a role in regulating pressure in the corpus cavernosum of the penis.

The authors describe the penis as “an organ uniquely suitable for gene transfer,” mainly because it is an accessible external organ and it has internal structural features that enhance distribution and prolonged presence of the replacement gene and minimize the potential for spread of the gene to other organs or tissues.

The primary endpoint of the trial was safety and tolerability of the treatment, and no serious adverse effects were observed at any dose. Patients who received the two highest doses of hMaxi-K gene therapy demonstrated clinically significant improvement in erectile function that lasted throughout the 24-week study period. The authors emphasized, however, that secondary efficacy outcomes must be confirmed in additional, placebo-controlled studies. Despite the promising clinical findings, “one needs to be very cautious about speculation regarding the potential of this approach for treating ED,” he cautions.

The study is published in the December 2006 issue of Human Gene Therapy. “The rationale for gene replacement of hSlo for treatment of ED was based on many years of basic research studying the role of K channels in erectile dysfunction,” explains James M. Wilson, M.D., Ph.D., head of the Gene Therapy Program, Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine.


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