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Hepatitis C Drug Rocks Virus in Early Test

Dramatic Impact in 2 Weeks; Long-Term Effect, Safety Unknown

VX-950: Protease Inhibitor Targets Hepatitis C Virus continued...

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.

"It is difficult to say at this moment how long VX-950 treatment would take," Reesink says. "But from this first-phase trial, one can speculate -- and this is just speculation -- that the treatment duration may be substantially shorter than the current standard of therapy."

"You will see combination treatments with this drug," Schiff predicts. "But if you end up with a combination of oral agents, instead of the current medications with this big side-effect profile, that would still be much better for patients."

Message to Patients: Don't Stop or Delay Current Treatment

Reesink and Schiff both warn patients with chronic hepatitis C infection not to stop their current treatment or to delay starting current therapies. Even if everything goes perfectly -- and drug development rarely does -- it would be more than five years before VX-950 could be available to patients.

"It would be a mistake for people to stop their current treatment to wait for this stuff," Schiff says. "That would be a big mistake. What we heard today could represent a major advance in treatment. But I used to chair an FDA drug-approval committee, and I can tell you that when a new drug comes along everybody gets turned on -- and then they find side effects of something and the drug has to be withdrawn. I don't think that is going to happen here, but it's too soon to tell."

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