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Reuters Health Information (2008-11-03): Therapeutic hepatitis C vaccine shows benefit in phase 2 trial

Drug & Device Development

Therapeutic hepatitis C vaccine shows benefit in phase 2 trial

Last Updated: 2008-11-03 11:44:45 -0400 (Reuters Health)

SAN FRANCISCO (Reuters Health) - In patients with chronic hepatitis C (HCV), an investigational HCV vaccine, GI5005, improves response to pegylated interferon plus ribavirin, researchers report.

Interim phase 2 results of a study of GI5005 were presented by principal investigator Dr. John F. McHutchison of the Duke Clinical Research Institute in Durham, North Carolina, here at The Liver Meeting 2008, the annual meeting of the American Association for the Study of Liver Diseases (AASLD).

"GI5005 is a whole heat-killed S. cerevisiae immunotherapy expressing high levels of HCV NS3 and Core antigens," Dr. McHutchison and colleagues explained. "GI5005 has been designed to elicit antigen-specific host CD4 and CD8 T-cell responses with the goal of improving the rate of immune clearance of HCV."

The investigators have randomized 140 patients with HCV genotype 1 who are either treatment-naive (74% of patients) or treatment-resistant (26% of patients) to treatment with GI5005 and peg-interferon and ribavirin, or to the current standard of care with peg-interferon and ribavirin.

In the vaccine arm, patients received GI5005 monotherapy, consisting of five weekly followed by 2 monthly subcutaneous doses of 40 YU (Yeast Unit = 10,000,000 yeast) GI5005 followed by triple therapy consisting of monthly 40 YU GI5005 doses plus peg-interferon and ribavirin for 48 wks in treatment-naive patients and for 72 wks in non-responders.

Dr. McHutchison presented an interim analysis of the first 4 weeks of triple therapy.

"Treatment-naive patients with high viral loads at baseline (greater than 600,000 IU/mL) saw a 2.6-fold improvement in RVR (rapid viral response) by four weeks," Dr. McHutchison announced. RVR was a defined as an HCV RNA level less than 25 IU/mL by week 4.

"Treatment-naive patients with a high viral load at baseline are particularly difficult to treat to an RVR," he commented. "RVR is highly predictive of whether a patient will achieve a sustained virologic response, or 'cure,' which is defined as undetectable HCV RNA at 6 months post-treatment."

"A significant improvement was also noted in the rate of viral reduction ... with a two-fold improved slope (0.32 log10/month difference) for patients receiving GI5005 plus standard of care," Dr. McHutchison added. The magnitude of increased viral clearance with GI5005 treatment was comparable in all patient subgroups, including prior non-responders and patients with high viral load at baseline.

"These data represent early but important evidence that a patient's natural immune response can be harnessed to positively influence important virologic endpoints with the potential to impact the course of chronic HCV infection," said Dr. McHutchison concluded.

"This provides proof of concept," AASLD President Dr. Arthur J. McCullough told Reuters Health. "It shows that the vaccine stimulates the innate immune system and that viral load dropped in both groups -- in treatment-naive patients and in nonresponders -- with a peak trough at 12 weeks. (Viral) levels started to come back up a bit after that."

Dr. McCullough pointed out that the GI5005 "has the potential to be given to prevent HCV infection, but that raises the question, 'Who should you vaccinate?'."

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