TITLE: Safety, Tolerability and Immunogenicity of GS-4774, an HBV-specific Therapeutic Vaccine, in Healthy Volunteers
AUTHORS (FIRST NAME, LAST NAME): Anuj Gaggar1, Claire Coeshott2, Mani Subramanian1, John G. McHutchison1, David Apelian2
Institutional Author(s):
INSTITUTIONS (ALL): 1. Gilead Sciences, Foster City CA, CA, United States.
2. Globeimmune, Louisville, CO, United States.
ABSTRACT BODY: Background: Chronic HBV (CHB) infection is in part characterized by diminished T cell responses to viral antigens. A therapeutic vaccine enhancing the adaptive immune response to HBV may provide a strategy to improve the rate of HBsAg loss and seroconversion in CHB patients compared to nucleos(t)ide HBV polymerase inhibitors alone. GS-4774 is a yeast-based vaccine (Tarmogen) expressing a chimeric protein comprising of 60 amino acids of HBV X protein, the full 399 amino acids of HBV surface protein, and 182 amino acids of the HBV core protein.. The aim of this study was to evaluate the safety and immunogenicity of GS-4774 in healthy volunteers.
Methods: A Phase 1 study was conducted in healthy volunteers (n=60) to determine the safety and immunogenicity of GS-4774 using different doses and schedules. Doses of 10 yeast units (YU), 40 YU or 80 YU/dose were evaluated as either a) weekly dosing for 5 doses then a single monthly dose, or b) monthly doses for 3 consecutive months. The immune response to GS-4774 was assessed on Days 15, 29, 36, 57 and 85 by lymphocyte proliferation assays (LPA), IFN-γ ELISpot assays, and antibody response to specific HBV antigens.
Results: GS-4774 was well tolerated with no serious adverse events, no grade 3 or 4 adverse events, and no laboratory abnormalities observed in the study. Adverse events were more frequent with weekly dosing compared with monthly dosing and at the 80YU dose compared to the 10YU and 40YU group. There was one treatment discontinuation due to adverse event (skin reaction) in the 80 YU cohort. Available immunogenicity data until day 36 are summarized in the table. The majority of subjects demonstrated evidence of an HBV-specific immune response as assessed by LPA. No dose response in HBV-specific immunogenicity of GS-4774 was observed by LPA, and monthly dosing was similar to weekly dosing. An early HBV-specific T-cell response by IFN-γ ELISpot was observed in a greater number of subjects receiving the 10YU dose. As expected given the cellular immune targeting characteristics of the platform, no antibody response to core and surface antigens was observed at the early time points. Complete immunological and safety results of the study will be presented.
Conclusions: GS-4774 was well tolerated, and elicits HBV specific immune activation at the lowest monthly dose of 10 YU. Further evaluation of GS-4774 in patients with chronic hepatitis B is warranted.