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
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
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.