New ED Drugs on Horizon

Faster Acting, Longer Lasting Treatments for Erectile Dysfunction

Medically Reviewed by Louise Chang, MD on May 24, 2006
From the WebMD Archives

May 24, 2006 -- New treatments for erectile dysfunctionerectile dysfunction are on the way. One works fast. One lasts long. And another promises to be the next best thing to a cure.

The new drugs aren't here yet. They don't even have official brand names. But they promise to give men with erectile dysfunction even more options than they now get from Viagra, Cialis, and Levitra.

"We have a chance to glimpse the future of treatment in sexual dysfunction," says James Barada, MD, director of the Center for Sexual Health in Albany, N.Y. Barada moderated a news conference in which researchers discussed new findings reported at this week's annual meeting of the American Urological Association in Atlanta.

Nearly a Cure for ED?

For now, it is called hMaxi-K. Suitably enough for an erection treatment, it is a form of gene therapy called naked DNA. Its DNA carries a human genetic code into target cells. When the cell reads this code, it makes a protein. In the case of hMaxi-K, it is a protein that tells smooth muscles to relax.

That is why hMaxi-K is supposed to help erectile dysfunction, which happens when smooth muscle in the penis won't relax to let blood flow into the penis.

Arnold Melman, MD, chairs the department of urology at Albert Einstein College of Medicine. He's also co-founder of Ion Channel Innovations, the company that's developing hMaxi-K. At the urology meeting, Melman reported the results of the first human trial of hMaxi-K.

In this human study, 11 men with erectile dysfunction received injections of the gene therapy directly into the penis. Because this was the first human study, the doses used were smaller than those expected to have a true effect on erections.

The study was successful in two ways. First, it was safe. Second, two men who received higher doses of hMaxi-K had greatly improved erections -- which occurred only during sexual arousal -- for six months after a single treatment.

"Let me tell you what the patient who responded for six months said. He said he felt like a kid again," Melman said at the news conference. "With any current erectile dysfunction drug, you have to plan to have sex in order to give the drug time to work. With this, you don't have to plan sex. This lets you get normal erections whenever you are aroused. That is the big advantage."

Barada said the treatment borders on a cure.

"It is the interface between treatment and cure, because you affect the tissue itself so it responds in a normal fashion," he said.

There's even better news: hMaxi-K isn't just for getting erections. Melman says a wide range of diseases arise from the failure of smooth muscle to relax.

"These diseases don't get much respect," he said. "They include overactive bladder, asthmaasthma, irritable bowel syndrome, benign prostatic hyperplasia, premature labor, and premenstrual syndrome."

Melman said a clinical trial in overactive bladder patients is expected to begin this summer.

2-in-1 Erection Drug

Sexual dysfunction pioneer Irwin Goldstein, MD, now editor of The Journal of Sexual Medicine, reported findings from a human study of a long-acting erection drug called SLx-2101.

Like Viagra, Cialis, and Levitra, SLx-2101 works by inhibiting an enzyme that makes smooth muscles contract. Unlike the currently approved erection drugs, SLx-2101 is two drugs in one.

When first taken, SLx-2101 is a powerful erection drug. While it is still working, the body begins to process it into a second drug. The second drug, dubbed SLx-2101m1, is also a powerful erection drug.

"Existing erectile dysfunctionerectile dysfunction drugs either act quickly or act for a long time," Goldstein said, at the news conference. "What is so exciting is that for the first time we have a drug that has both clinical advantages. It is a fast-acting drug that acts well beyond 48 hours."

Interestingly, Goldstein said that SLx-2101 improves erections not only in men with erectile dysfunction, but also in men already able to have erections.

SLx-2101 is being developed by Surface Logix Inc. Goldstein serves as a consultant to the company.

Faster, Shorter-Acting Erection Drug

Not everyone wants or needs a long-lasting erection drug. For them, a new drug called avanafil may be helpful.

Avanafil reaches maximum blood concentrations 35 minutes after it is taken, reports Mayo Clinic researcher Ajay Nehra, MD. It has a half-life (the time it takes for the body to eliminate half the quantity of a drug) of 90 minutes, compared with four hours for Levitra and Viagra and 17.5 hours for Cialis.

Why would someone want an erection drug that doesn't last very long? Nehra said that aside from personal preferences, men who take nitrate-based heart drugs (such as Nitrostat, Isordil, and Imdur) are warned against using erection drugs at the same time.

In human tests, Nehra and colleagues found that men taking a nitrate-based drug while on avanafil had less of a drop in blood pressure and less of an increase in blood pressure than men who took the heart drug while on Viagra.

"Caution will continue with short-acting nitrate drugs," Nehra said. "But with avanafil, men may be able to continue this medication."

Avanafil is being developed by Vivus, Inc., in Mountain View, Calif. Avanafil is the generic name for the drug; it does not yet have a brand name.

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SOURCES: Annual meeting of the American Urological Association, Atlanta, May 20-25, 2006. Abstracts 923 and 925 (avanafil), 924 (SLx-2101), and (hMaxi-K). James Barada, MD, director, Center for Sexual Health, Albany, N.Y. Arnold Melman, MD, professor and chairman, department of urology, Albert Einstein College of Medicine, New York; directing member, Ion Channel Innovations, New York. Irwin Goldstein, MD, editor-in-chief, The Journal of Sexual Medicine. Ajay Nehra, MD, Mayo Clinic, Rochester, Minn.
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