UPDATE: Agenus Vaccine Shows Significant Reduction in Viral Burden after HerpV Generated Immune Activation

Phase 2 trial in patients with genital herpes shows correlation between viral load reduction and CD8 T cell activation, an important clinical surrogate Trial shows booster shot demonstrates sustainable, long-term effect Agenus Inc.

, an immuno-oncology company developing a portfolio of checkpoint modulators (CPMs), heat shock protein peptide-based vaccines, and adjuvants, today announced promising Phase 2 results for HerpV, a synthetic vaccine candidate for the treatment of patients with genital Herpes Simplex Virus-2 (HSV-2). HerpV contains a defined mixture of peptides representing HSV-2 antigens plus Agenus' QS-21 Stimulon® adjuvant. In a randomized, Phase 2, double-blind, multi-center study, the majority of patients showed an immune response to the HSV antigens after a series of vaccinations and a booster dose at six months. More than half of those vaccinated developed a robust anti-HSV cytotoxic T-cell immune response, and in those patients there was a statistically significant 75% reduction in viral load (P<0.001; CI: 46.2 – 88.6%). This level of reduction in viral load has the potential to result in reduced incidence and severity of herpetic outbreaks and a reduction in viral transmission1. “We are pleased that the cellular immune response observed with HerpV vaccination is associated with a significant reduction in viral replication in the genital tract,” said Robert Stein, MD, PhD, Chief Scientific Officer of Agenus. “The fact that our vaccine contains multiple HSV-2 antigens may contribute to its desired effects. We look forward to advancing discussions with potential partners to take this program into the next phase of clinical research.” After the booster shot, HerpV demonstrated a durable reduction in viral shedding approximating 14% (RR=0.86 and CIs: 0.58-1.26) and remains consistent with the reduction in viral shedding observed during the initial treatment period. The protocol defined secondary analyses were viral load and viral shedding after the booster shot, the primary endpoint of the study was reported in November 2013. In this study, the booster shot was given six months after the first vaccination. Patients continue to be followed for safety and long-term immune response. HerpV reported adverse events have mostly been in line with expectations for a therapeutic vaccine and with effects commonly associated with QS-21 Stimulon® adjuvant. These adverse events are short-lived and include flu-like symptoms and injection-site reactions.