Therapeutic HCV Vaccines May Lower Viral Load and Improve Response to Interferon-based Therapy

		SUMMARY: Two investigational therapeutic hepatitis C virus (HCV) vaccines may help control the virus in infected individuals, according to data presented last month at the 60th Annual Meeting of the American Association for the Study of Liver Diseases (AASLD 2009) in Boston. GI-5005 increased the likelihood of response to pegylated interferon plus ribavirin. Another vaccine candidate, IC41, was associated with a steady decrease in HCV viral load.

By Liz Highleyman

Unlike prophylactic vaccines, which are intended to prevent initial infection, therapeutic vaccines are designed to stimulate an immune response in people who are already infected.

GI-5005

In the first study (abstract LB15), John McHutchison from Duke Clinical Research Institute and colleagues evaluated GI-5005 in both treatment-naive chronic hepatitis C patients and those who were non-responders to previous interferon-based therapy.

GI-5005 is a Tarmogen, a vaccine containing whole, heat-killed Saccharomyces cerevisiae, a type of yeast, genetically engineered to express HCV NS3 and core antigens. Prior studies have shown that GI-5005 elicits antigen-specific T-cell responses. The goal of the vaccine is to promote elimination of liver cells carrying HCV.

In this open label Phase 2b trial, 140 HCV genotype 1 patients received standard-of-care therapy with pegylated interferon plus ribavirin. Half were randomly assigned to also receive injections of GI-5005, first as monotherapy for 12 weeks before starting standard therapy, then as triple therapy with pegylated interferon/ribavirin. Treatment-naive participants were treated for 48 weeks and prior non-responders for 72 weeks.

The researchers found that among treatment-naive patients, in a modified intent-to-treat analysis at the end of 48 weeks of treatment, 74% receiving triple therapy achieved HCV RNA < 25 IU/mL, compared with 59% receiving standard therapy. Furthermore, nearly twice as many triple therapy recipients experienced ALT normalization. Among non-responders, the end-of-treatment response rate was 32% in both the triple therapy and standard therapy arms.

Triple therapy including GI-5005 was well tolerated, with no significant new toxicities other than those normally associated with pegylated interferon/ribavirin. Similar proportions (7%-10%) discontinued treatment in the standard therapy and triple therapy groups. The most common adverse events associated with GI-5005 were injection site reactions, which were usually mild and transient.

"The efficacy and safety data generated thus far in this trial are encouraging and suggest a potentially important role for this compound in the treatment of HCV," said Dr. McHutchison in a press release issued by GI-5005 developer GlobeImmune.

Clinical Development and Regulatory Affairs, GlobeImmune, Louisville, CO; Duke Clinical Research Institute, Durham, NC; Weill Cornell Medical College, New York, NY; University of Arizona, Tucson, AZ; Center for Liver Diseases, University of Miami, Miami, FL; University of Colorado Denver, Aurora, CO; University of Texas Southwestern Medical Center, Dallas, TX; Scripps Clinical Research Center, La Jolla, CA; Maryland Digestive Disease Research, Laurel, MD; Baylor College of Medicine, Houston, TX; Alamo Medical Research, San Antonio, TX; South Denver Gastroenterology, PC, Englewood, CO; Center for Disease of the Liver and Pancreas, Swedish Medical Center, Englewood, CO; University of Hawaii, Honolulu, HI; QST Consultations, Allendale, MI.

IC41

In the second study (abstract 1558), C.S. Klade from Intercell in Vienna, Austria, evaluated IC41, a peptide vaccine containing HCV antigens as CD4 and CD8 T-cell epitopes, using poly-L-arginine as an adjuvant (an agent that promotes immune response).

This Phase 2 study included HCV genotype 1 patients naive to standard therapy. In the first group, 50 participants received an optimized IC41 dose schedule consisting of 8 intradermal injections at biweekly intervals with topical application of the TLR 7/8 agonist immune-modulator imiquimod (Aldara). In the second group, 21 patients received an intensified dose schedule consisting of 16 subcutaneous injections of IC41 at weekly intervals without imiquimod.

At week 16, in an intent to-treat analysis, patients who received the optimized schedule experienced a highly significant HCV viral load decline of 0.21 log. At week 38 (24 weeks after the last dose), HCV RNA decreased by 0.47 log. Patients with a high baseline viral load (> 2 million U/mL) had a more pronounced decline, of 0.61 log. Eight patients (24%) achieved virological response, defined as a decline of > 0.8 log. However, there was no apparent effect on HCV viral load in the group that received the intensified dosing schedule.

Overall, 40% to 60% of patients exhibited T-cell responses during therapy and up to 6 month after vaccination in both treatment groups, but there was no significant correlation between viral load decrease and T-cell response.

"This is the first report showing a significant antiviral effect of a peptide vaccine in HCV infected patients," the investigators concluded. "The time course with increased RNA decline 24 weeks after the last vaccination is encouraging and justifies further clinical studies potentially in combination with standard therapy or novel antiviral medications."

Intercell AG, Vienna, Austria; Hannover Medical School, Center for Internal Medicine, Hannover, Germany.

References

JG McHutchison, IM Jacobson, TD Boyer, and others. GI-5005 therapeutic vaccine plus PEG-IFN/ribavirin improves end of treatment response at 48 weeks versus PEG-IFN/ribavirin in naive genotype 1 chronic HCV patients. 60th Annual Meeting of the American Association for the Study of Liver Diseases (AASLD 2009). Boston. October 30-November 1, 2009. Abstract LB15.

CS Klade, A von Gabain, and MP Manns. Significant continuous viral load decline in treatment-naive HCV genotype 1 patients after therapeutic peptide vaccination with IC41. 60th Annual Meeting of the American Association for the Study of Liver Diseases (AASLD 2009). Boston. October 30-November 1, 2009. Abstract 1558.

Other source

GlobeImmune's Hepatitis C Therapeutic Vaccine Combined with Standard of Care Increases End of Treatment Response Rate by 15%. Press release. November 2, 2009.