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
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."