Overview of Experimental Therapies for ED
Scientists continue to search for new therapies to prevent and treat erectile dysfunction. Pharmaceutical companies are hot on the trail of several drugs, some of which may be improvements on those already available; others which will attack the challenge of erectile dysfunction from new directions. Researchers are also pursuing more innovative approaches, including gene therapy and stem cell therapy. Together with current treatment methods and other therapist not yet dreamed of, experts are putting together new strategies and options for men who face erectile dysfunction and other sexual health issues.
Experimental Drugs for ED
Avanafil
Several new drugs are in the pipeline for treatment of erectile dysfunction. One is called Avanafil, and it is still in phase III clinical trials. Thus far Avanafil has met the Food and Drug Administration’s (FDA’s) requirements for improvement in sexual function based on trial results. In one clinical trial that involved 646 men with erectile dysfunction, nearly 80 percent of the men who took Avanafil at the highest dose (200 mg) were able to achieve an erection sufficient for intercourse within 30 minutes or less.
The data, which have not yet been published in a peer-reviewed journal, also showed that the Avanafil is effective for six hours or longer. The most common side effect was headache, experienced by 7 percent of the men, followed by flushing (4.6%) and nasal congestion (2.3%). Avanafil works the same way as the other three erectile dysfunction drugs on the market: Cialis, Levitra, and Viagra. The makers of Avanafil, Vivus, report that this drug not only works faster but also may have fewer side effects. Vivus expects to submit the drug to the FDA for approval in late 2010 or early 2011. (WebMD)
Udenafil (Zydena®)
Udenafil (Zydena®) is yet another erectile dysfunction drug in the pipeline. It also works similarly to the other available drugs, although it reportedly is effective for up to 12 hours. The drug has been approved in Korea and Russia but not the United States. Studies by udenafil’s manufacturer, Dong-A Pharm Tech Co., Ltd., report that compared with placebo, 88 percent of men who took 75 mg of udenafil daily for 12 weeks achieved an erection sufficient for intercourse. In a secondary test, udenafil also improved urinary tract symptoms associated with benign prostatic hyperplasia in 65 percent of men who took the drug.(Health Reserve)
In a randomized, double-blind, placebo-controlled study published in the Journal of Sexual Medicine, 103 men with erectile dysfunction were given either udenafil (50 men) or placebo (53 men) for four weeks. The researchers reported that udenafil significantly improved the maintenance of erection in 54.7 percent of men compared with 28.3 percent who took placebo, and that the drug was effective for 12 hours after dosing. (Park 2010)
In November 2009, Warner Chilcott partnered with Dong-A Pharm Tech Co. to conduct phase III trials of udenafil in the United States. More than 1,100 men will reportedly participate in the trials, and if the results are positive, it will likely be 2012 or 2013 before the drug becomes available in the United States.
Immunophilins
Another type of drug being investigated to recover erectile function is called an immunophilin ligand. Immunophilins are proteins present in immune and nerve tissues, and they are receptors for medications that have immunosuppressant properties. Some of those drugs include tacrolimus, cyclosporine, and rapamycin. Although these drugs suppress the immune system and thus increase the risk of infection, they also protect nerves, which makes them a possible candidate for preventing nerve damage associated with prostatectomy. Thus far a study in rats at Johns Hopkins has suggested that use of tacrolimus resulted in greater recovery of erectile function after trauma than rats that did not receive the drug. (Sezen)
Gene Therapy for ED
Gene therapy is an experimental technique that uses genes to prevent or cure disease or a medical condition. Basically, it involves inserting a gene into a person’s cells rather than use a drug or surgery to address the problem. The genetic material is used to compensate for abnormal genes.
Genes are delivered to the cells via a carrier called a vector. Certain viruses, such as retroviruses, are usually used as vector because they can infect the cell and be modified before they are injected so they do not cause disease. Gene therapy must overcome many technical challenges before it will be ready to use to treat erectile dysfunction.
Thus far, gene therapy has been tested in animal models to restore normal function to the penis, and only one human trial has been published in the peer-reviewed literature. (Harraz 2010)
Stem Cells for ED Treatment
Although the work in this area is still in its infancy, preliminary studies indicate that stem cells may help improve erectile function. In animal studies, fat-derived stem cells placed near blood vessels became smooth muscle, which is important because this is a muscle type that often fails to function properly. In a study of type 2 diabetic rats, the researchers found that injection of these stem cells improved blood pressure in the intracavernosal tissue (the spongy tissue in the penis).
At the annual meeting of the American Urological Association in May 2008, Tom F. Lue, MD, presented results of a pilot experiment in which he injected umbilical cord blood stem cells into men who had not responded to standard erectile dysfunction medications, the PDE5 inhibitors such as sildenafil. Once the stem cells are injected into the affected area, they help produce new blood vessels in the de-oxygenated tissues, which can lead to improved erectile function. (AUA meeting) Synthetic cord blood stem cells also are under investigation for treatment of erectile dysfunction. In clinics outside the United States, some clinics use autologous adult stem cells (cells collected from your own bone marrow) to treat erectile dysfunction.
Combination Therapies for ED Treatment
Erectile dysfunction is a challenge to treat, and one reason is that there are three main structures that must operate optimally for an erection to occur: the erection nerves, smooth muscles, and endothelium. Right now, erectile dysfunction is, for the most part, treated with one therapy at a time. Penile rehabilitation ventures into using two treatments, pills and penile injections, but for the most part erectile dysfunction is treated with one strategy at a time.
That could change in the near future. As more and more potential treatment options are uncovered, including new drugs in the pipeline, gene therapy, and stem cell therapy, physicians may soon be treating erectile dysfunction with combination therapy. Another area of possible merit is the use of erectile dysfunction pills (PDE5s) and statins, which are drugs used to lower cholesterol. Scientists have begun exploring the close relationship between erectile dysfunction and high cholesterol and the impact of the use of both statins and PDE5 inhibitors in men who have both of these conditions. (Miner)
Treatment for erectile dysfunction in the near future may include combination therapies.
See also
Shockwave Treatment for Erectile Dysfunction
References
Health Reserve for udenafil:
http://www.healthreserve.com/erectile_dysfunction/udenafil-zydena.htm
Park HJ et al. Efficacy of udenafil for the treatment of erectile dysfunction up to 12 hours after dosing: randomized placebo-controlled trial. J Sex Med 2010 Jun; 7(6): 2209-16
Sezen SF et al. Role of immunophilins in recovery of erectile function after cavernous nerve injury. J Sex Med 2009 Mar; 6 Suppl 3:340-46
WebMD Avanadil:
http://www.webmd.com/erectile-dysfunction/news/20091123/new-erection-drug-faster-safer
Harraz A et al. Emerging gene and stem cell therapies for the treatment of erectile dysfunction. Nature Reviews Urology 2010 Mar; 7:143-52
Presentation at the Annual Meeting of the American Urological Association, May 17-22, 2008, Orange County Convention Center, Orlando, FL, by Tom F. Lue, MD
Miner M, Billups KL. Erectile dysfunction and dyslipidemia
