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Hepatitis C Drug Rocks Virus in Early Test

Dramatic Impact in 2 Weeks; Long-Term Effect, Safety Unknown
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VX-950: Protease Inhibitor Targets Hepatitis C Virus

VX-950 is a designer drug discovered only after huge effort. It targets a key hepatitis C protein. That protein is called protease, an enzyme the virus needs to reproduce.

It's not the first time a hepatitis C protease inhibitor has been tested in humans. Recently, an experimental hepatitis C protease inhibitor called BILN 2061 showed promising results in short-term human trials. But that drug had to be put on hold when monkey studies suggested it was toxic to the heart.

Schiff says that "seven or eight" pharmaceutical companies are nearing clinical trials of their own protease inhibitors against hepatitis C virus. He estimates that more than 20 companies are developing new "small molecule" drugs designed as oral hepatitis C treatments.

The term "protease inhibitor" may sound familiar. Drugs targeting HIV protease were a huge breakthrough for AIDS therapy. However, HIV rapidly develops resistance to these drugs. That's why AIDS drugs have to be taken in powerful combinations.

Whether hepatitis C virus will develop resistance to VX-950 or other protease inhibitors isn't known. Schiff notes that unlike HIV, the hepatitis virus doesn't hide inside cells where drugs can't reach it. So if the drug keeps viral levels low, there's a good chance the virus won't become resistant. It's even possible, Schiff says, that hepatitis C protease inhibitors will work all by themselves, without the need for combination therapy.

Shorter, Easier Hepatitis C Treatment?

In the Reesink study, the most effective dose of VX-950 was a three-times a day treatment. Four of eight patients receiving this dose for 14 days had about a 25,000-fold drop in hepatitis C virus levels. The virus became undetectable in two patients. Larger doses given twice a day didn't work as well, nor did lower doses given three times a day.

In this short study, no serious side effects seemed to happen. Possible side effects included headache, diarrhea, nausea, frequent urination, and sleepiness/drowsiness. All these side effects were mild.

It's not at all clear whether VX-950 really will work all by itself or whether it will work best in combination with other drugs. Unlike current hepatitis C treatments, it's an oral drug. That raises hopes for a much easier-to-take -- and, perhaps, shorter -- treatment regimen.

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