The Next Hepatitis C Blockbuster?

On Friday, the annual meeting of the American Association for the Study of Liver Diseases (AASLD) convenes, and several drug developers -- from Roche to smaller development-stage participants such as Pharmasset (Nasdaq: VRUS  ) -- will present data on their lead compounds for treating hepatitis C.

It's an exciting time to follow the hepatitis C treatment space, since there have never before been so many new compounds in development for the disease. With so many compounds to sift through, we can look at the leading drug candidates that may play a role in changing how the hepatitis C virus (HCV) will be attacked.

The leaders
Right now, most patients infected with the genotype 1 HCV -- the most common subtype of HCV in North America and Europe -- are treated with an interferon-based therapy consisting of either Schering-Plough's (NYSE: SGP  ) PEGINTRON or Roche's Pegasys.

Only about half of the genotype 1-infected patients who are treated with these standards of care, in combination with ribavirin, achieve a sustained virologic response, meaning they show no signs of HCV in their blood six months following treatment.

Having no signs of HCV at any time during a course of treatment means a patient has undetectable viral loads. When patients achieve undetectable viral loads, it could indicate the possibility of a sustained virologic response and, perhaps, ultimately being cured of the disease.

The future of HCV treatment will almost assuredly consist of a combination of an interferon and an oral antiviral drug. More than a dozen oral antivirals are in various development stages, ranging from Abbott Labs' (NYSE: ABT  ) preclinical-stage protease inhibitor to Vertex Pharmaceuticals' (Nasdaq: VRTX  ) phase 2 candidate, telaprevir.

Here are the leaders in efficacy and stage of clinical development in the race to become the first oral antiviral hepatitis C treatment on the market.

Drug

 Developer

Select Study Results*

Development Phase

HCV Target

R1626

Roche

81% of patients with undetectable viral loads after 4 weeks at optimal dose, in combination with Pegasys in treatment-naive patients.

Completed phase 2a testing.

Nucleoside polymerase inhibitor

R7128

Pharmasset

Up to a mean 2.7 log reduction in viral loads after 14 days of treatment as monotherapy in treatment-experienced patients.

Phase 1 combination therapy testing.

Nucleoside polymerase inhibitor

Telaprevir

Vertex  

79% of patients with undetectable viral loads after 12 weeks at optimal doses, in combination with Pegasys in treatment-naive patients in most recent study.

Multiple ongoing phase 2 studies.

Protease inhibitor

HCV-796

ViroPharma (NASDAQ:VPHM)

73% of patients with undetectable viral loads after 12 weeks in combination with PEGINTRON in treatment-naive patients.

Dosing in phase 2 study halted because of adverse events. Patient follow-up continues.

Non-nucleoside polymerase inhibitor

Boceprevir

Schering-Plough

79% of patients with undetectable viral loads at optimal dose after 12 weeks, in combination with PEGINTRON in treatment-naive patients.

Multiple ongoing phase 2 studies.

Protease inhibitor

*Study results in genotype 1 HCV patients and all combination study results include the use of ribavirin.

All the compounds above that have enough data to date show incredible improvements in undetectable viral loads (if the data holds up over longer testing), versus about half of the patients who achieve a sustained virologic response from PEGINTRON or Pegasys therapy alone.

Still, it's not all gravy for the anti-HCV drugs in the table: Every single compound except the Pharmasset drug (which has not been tested in patients very long) has shown side effects, such as a rash with telaprevir, gastrointestinal problems with boceprevir, neutropenia with R1626, and high liver enzyme levels with HCV-796.

Innovations everywhere
The advent of antiviral compounds isn't the only innovation under way for treating HCV. There are also drugmakers, including Flamel Technologies and Human Genome Sciences, attempting to develop improved versions of the interferons. Flamel's drug is in phase 1 testing, and Human Genome Sciences expects phase 3 results from its compound, dubbed albuferon, in 2009.

A more distant future in combating hepatitis C could see the disappearance of the interferons from treatment altogether and the combination use of only antiviral drugs. Roche, Schering-Plough, Abbott, and Gilead Sciences (Nasdaq: GILD  ) all have the resources to develop antiviral-only combination therapies, similar to what is used to treat HIV. At the AASLD meeting, Schering, Novartis, and Idenix Pharmaceuticals (Nasdaq: IDIX  ) will present preclinical data on in vitro testing of a polymerase and protease inhibitor in combination treatment without an interferon therapy.  

Participants in the upcoming AASLD meeting know that, even though there have been stumbles in 2007 with Idenix's lead HCV drug valopicitabine, Achillion Pharmaceuticals' GS 9132, and ViroPharma's HCV-796, it's still an unprecedented time in the development of HCV therapies.


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