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Magic Bullet For Hepatitis C?

The Editors at Hepatitis Central
January 24, 2005

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The following article from the Forbes magazine website is very informative.

The fact that Vertex is so far along with their protease inhibtor is very exciting. As is the sheer number of companies working on their own Hepatitis C treatment.

Given the potential size of this market (pegged at $4 billion by 2009) it is no wonder that pharmaceutical companies are falling all over themselves (and each other) to develop a more viable treatment than currently exists.

I have felt for quite a while that the protease inhibitors were a development to watch. This article gives more more information to illustrate why that is so.

Magic Bullet For Hepatitis C

Scott Gottlieb, M.D., Forbes/Gottlieb Medical Technology Investor, 01.24.05, 10:23 AM ET

When I was a resident in medicine, there was a virus that frightened doctors who had to handle needles and scalpels. Doctors were afraid that in the hurried delivery of emergency care, a hand would slip or a scalpel would fall, and a doctor would accidentally stick herself. If a patient had the virus, chances were good that a doctor could soon have it, too.

But I’m not talking about HIV, the virus that causes AIDS. I’m talking about hepatitis C.

There are about 200 million people in the world who are infected with the hepatitis C virus (HCV)–almost five million in the U.S. alone. The virus causes your liver to swell and stops it from working. Eventually, the liver can become incapable of functioning because constant inflammation kills the organ. HCV is spread by contact with the blood of an infected person, and it is extremely contagious, even more contagious than AIDS.

In industrialized countries, hepatitis C causes 40% of all of the advanced liver disease and 60% of liver cancers. When patients reach these advanced stages, there are not many cures. Short of a liver transplant, many patients with advanced liver disease soon die.

Today, the standard treatment for hepatitis C is the combination of an antiviral medicine that targets the virus and an immune system-boosting drug that helps the body fight the infection. This elixir works for about half of all patients, but many patients can’t tolerate the regimen or their bodies don’t respond to it.

But there is new hope in the development of a class of drugs known as protease inhibitors. This isn’t the same kind of protease inhibitor that has been used to successfully treat AIDS. In the case of HCV, the drug is targeted at a unique kind of protease enzyme only used by the hepatitis C virus.

The most advanced and most promising protease inhibitor for hepatitis C belongs to the Cambridge, Mass.-based biotechnology company Vertex Pharmaceuticals (nasdaq: VRTX – news – people ).

Scientists at Vertex used structure-based drug design to create the drug, known as VX-950. Structure-based design means that scientists use special equipment to make computer models of a three-dimensional structure of the enzyme they are targeting. This enables more rational attempts to design drugs to stick inside the enzyme’s active site, by building the ideal drug one atom at a time, like a microscopic Lego set.

The small trial is going to compare the safety and effectiveness of VX-950 to a sugar pill in about 60 healthy volunteers and patients with hepatitis C. The study is expected to finish up this year. It should give Vertex a good look at just how potent the new drug is, as well as a peek at whether it is safe.

If VX-950 works, it will be a big advance for patients with hepatitis C. It could also be a blockbuster medicine–a first-in-class, broad-spectrum antiviral drug that could work for many, if not most, patients infected with hepatitis C. The market for drugs that treat hepatitis C was worth $1.6 billion last year and is expected to grow to $4 billion by 2009.

Doctors have high expectations for this drug class. But there is plenty of caution. At least one other protease inhibitor that was targeted against hepatitis C has failed in development, largely because it had too many side effects.

Keep in mind how protease inhibitors all work. They block an enzyme that belongs exclusively to the hepatitis C virus. There isn’t a human protein that is closely related to hepatitis C protease, so the drug should not be interfering with any human cellular processes at all.

That means that the only way these drugs could cause side effects in people is if the liver doesn’t break them down very well. This seems to be precisely the problem with older, early formulations of protease inhibitors that were developed by another company, Boehringer Ingelheim. These kinds of problems with metabolism are most often related to the way the drug is designed, not the underlying mechanism of the drug itself.

Schering-Plough (nyse: SGP – news – people ) is also believed to be in early clinical testing with a protease inhibitor of its own that targets hepatitis C. Several other companies have research programs focused on HCV protease inhibitors, including Gilead Sciences (nasdaq: GILD – news – people ), Merck (nyse: MRK – news – people ), Pfizer (nyse: PFE – news – people ), GlaxoSmithKline (nyse: GSK – news – people ) and InterMune (nasdaq: ITMN – news – people ). By all accounts, however, Vertex is farthest along.

There are also some other promising drugs in development for hepatitis C. But the protease inhibitors alone hold out some of the best near-term promise to fulfill the holy grail of hepatitis C therapy–a single potent pill that can destroy the virus all on its own, or in a small cocktail where the drug is used in combination with older medicines.

Vertex thinks it might have found the magic bullet. A clinical trial expected to finish this year could provide doctors, patients and investors with the first sure sign of whether Vertex is right.

Dr. Gottlieb is a practicing physician and a fellow at the American Enterprise Institute. He recently left the FDA, where he was Director of Medical Policy Development and a senior adviser for medical technology to the FDA Commissioner.

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