There are a number of new medications and treatments that are being researched or hypothesised, to treat erectile dysfunction. Although we do not offer these treatments, given that they are still at an experimental level, we are nonetheless following closely the developments and we discuss these treatments with patients to the best of our doctor’s knowledge.

Non-PDE5-I oral agents

Newer pharmacological treatments are focused on targeting alternative pathways in the erectile process, both centrally and peripherally. Drug categories currently being investigated to treat ED include the following:

• Dopaminergic agents

• Melanocortin receptor agonists

• Soluble guanylate cyclase stimulators and activators

• Rho-kinase inhibitors

Stem cell transplant

Stem cell therapy is a new treatment option that offers the potential to reverse the underlying causes of ED and reduce patient reliance on the transitory effects of PDE5-I medications. It has been researched in several animal studies in subjects who poorly respond to PDE5-Is (cavernous nerve injury and DM). Stem cell regenerative therapy is based on the rationale that stem cells can differentiate into a wide variety of cells including endothelial cells, Schwann cells, smooth muscle cells, and neurons. Moreover, it is hypothesized that stem cells have beneficial effects on damaged or diseased tissues by releasing various molecular mediators, which lead the host tissue to initiate a regenerative or healing response to diseased or injured tissue responsible for ED.

The majority of published studies are based on animal tests but there has been one reported case series of seven men from Korea. In this study, all diabetic patients, with ages ranging from 57 to 87, were treated with an intracavernosal injection of umbilical cord blood stem cells. Morning erection was regained in six out of the seven men at 6 months from time of injection. With concomitant use of sildenafil, all of these men were able to obtain vaginal penetration. No adverse events were reported.

A more recent study reported on A phase I/II clinical trial of intracavernosal injection of stem cells in patients with post-prostatectomy erectile dysfunction. In the authors’ sample size of 12 patients, they used escalating doses of stem cells and no serious side effects were noted. At 6 months, significant improvements in intercourse satisfaction and erectile function were noted in these patients. These results were preliminary and need to be confirmed in phase II trials.

Stem cell transplant therapy is a new frontier in medicine. Larger controlled studies are needed to show any potential benefit at the human level, and further investigation is paramount.

Gene therapy

Gene therapy is a potential therapeutic option that is another area of investigation for the treatment of ED. Genetic material can be easily injected into the penis, which is advantageous as this direct injection avoids potential systemic complications.

In the first human trial, patients were administered a single-dose cavernosal injection of hMaxi-K, a ‘naked’ DNA plasmid carrying the human cDNA encoding the gene for the alpha subunit of the human smooth muscle Maxi-K channel. No adverse events were noted in the 11 patients who received this therapy. Patients given the two highest doses of hMaxi-K had apparently sustained improvements in erectile function as indicated by improved IIEF domain scores over the length of the study.

This was a small study, but the encouraging safety profiles and effectiveness provide evidence that gene therapy is a viable option for the future. The role of stem cell regenerative therapy, in conjunction with gene therapy, will be heavily researched for the treatment of ED in the coming years.

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