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'Sponge' Drug Shows Promise For Treating Hepatitis C

With an estimated 2 million baby boomers infected with hepatitis C, the disease has reached epidemic levels among Americans age 48 to 68.

Doctors can now cure about 70 percent of hepatitis C cases, but the drugs' side effects can be severe. And many Americans are still left with a disease that can cause liver failure and cancer.

So doctors have been desperate for better treatment options.

One of the drugs in the pipeline, called miravirsen, may be able to stop the virus with little side effects, doctors from University Health Network in Toronto, Canada, reported Wednesday.

Their findings, published in The New England Journal of Medicine, are preliminary — the doctors gave the drug to just 27 patients for about a month. (Another 9 patients in the study were given a placebo.) But the study is still drawing attention because it offers proof-of-concept for a whole new class of drugs, called RNA interference drugs.

RNAi drugs work differently than traditional antivirals and antibiotics. And some scientists think they may have the potential to treat many illnesses, including the big killers, cancer and heart disease.

Traditional drugs are small chemicals that bind directly to the pathogen's machinery. In contrast, RNAi drugs are little fragments of RNA (or DNA) that act like "sponges" inside the cell. They mop up other RNA molecules that a virus or cancer cell needs to survive.

The pharmaceutical industry has been working for decades to get RNAi drugs to work, says Dr. Judy Lieberman of Harvard Medical School, who wasn't involved in the current study.

"At first there was wild enthusiasm – and billions of dollars," she tells Shots. "Hundreds of companies became involved because these drugs could be a whole new class of therapeutics for all kinds of diseases."

But enthusiasm and money waned over time, as companies realized it wasn't going to be easy to get these drugs to work.

Pharmaceutical giants, like Roche and Novartis, pulled the plug on million-dollar programs back in 2010, the journal Nature reported. But a few companies stayed the course. And, recently, there have been hints of success.

In January, the Food and Drug Administration approved the first RNAi drug, Kynamro (brand name mipomersen sodium), to help people with an extreme type of high cholesterol.

Now the current study on miravirsen offers hope for hepatitis C. "It's the first example of really strong clinical evidence" that the RNAi therapies are going to work in people, Lieberman says.

It's too soon to say how effective miravirsen is compared to current hepatitis C treatments, says Dr. Harry Janssen, who led the study. The goal of the current trial was to figure out how much miravirsen is needed to stop the virus temporarily — not it's overall effectiveness. That will require a bigger study.

Four of the nine patients who got the highest dose of miravirsen temporarily cleared the virus after five injections. "That compares very well to current treatments," Janssen says.

But unlike many medications available now, the RNAi drug works on all types of hepatitis C, even those that are tough to treat. And the short-term side effects are minimal — a rash and pain at the injection site.

Still, Janssen and his team don't know what the long-term effects could be and exactly how to combine miravirsen with other medications. And, he says, there are other hepatitis C drugs in the pipeline that are closer to getting approval.

"So I think our study is a big step forward for hepatitis C, but a bigger step forward for medicine in general," he says. "It opens big avenues for using this concept [RNAi drugs] in humans."

Copyright 2013 NPR. To see more, visit http://www.npr.org/.

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