Agenus Inc. (Nasdaq: AGEN), a developer of

therapeutic vaccines for cancer and infectious diseases, announced positive results

from a randomized, four-arm Phase 1 study of HerpV, a recombinant (off-the-shelf)

therapeutic vaccine for the treatment of genital herpes, which included the Company’s

proprietary QS-21 Stimulon adjuvant. The results were published in the peer-reviewed

journal Vaccine.

HerpV is the most advanced HSV-2 vaccine currently in clinical development for the

treatment of genital herpes.

“This is the first evidence that a therapeutic genital herpes vaccine has elicited both CD4+

and CD8+ T-cell responses in humans,” said Anna Wald, MD, MPH, Professor of

Medicine, Epidemiology and Laboratory Medicine, University of Washington, Member,

Fred Hutchinson Cancer Research Center, and lead author of the manuscript. “We are

very encouraged by these clinical results as published literature suggest that cellular

immunity needs to be stimulated for successful treatment of genital herpes – a physically

painful and emotionally debilitating disease that affects one in six adults in the US.”

In this four-arm Phase 1 study, 35 herpes simplex virus type 2 seropositive patients

received the vaccine plus QS-21 (HerpV), vaccine without QS-21, QS-21 alone, or

placebo. Patients received three treatments at two-week intervals.

All patients who were evaluable for immune response and received HerpV showed a

statistically significant CD4+ T cell response (100%; 7/7) to HSV-2 antigens as detected

by IFNγ Elispot, and the majority of those patients demonstrated a CD8+ T cell response

(75%; 6/8). The vaccine was well tolerated, with injection site pain as the most

commonly reported adverse event.

Agenus plans to advance HerpV into a Phase 2 study in 2012 that will measure the effect

of vaccination on viral shedding in individuals infected with HSV-2. Experts in HSV-2

clinical research believe that a reduction in viral shedding could translate into clinical

benefit.

“The publication of our herpes vaccine results marks the beginning of an exciting

period,” stated Garo Armen, Ph.D., chairman and CEO of Agenus. “Over the next 18

months, we expect pivotal data from multiple important clinical programs that

incorporate QS-21, which are being developed by our corporate partners.”

The HerpV study results appear in an article titled “Safety and immunogenicity of long

HSV-2 peptides complexed with rhHsc70 in HSV-2 seropositive persons,” which is

available online at http://www.sciencedirect.com/science/journal/aip/0264410X.

Earlier this year, the results of preclinical studies of HerpV were also published in

Vaccine in a separate manuscript titled, “A heat shock protein based polyvalent vaccine

targeting HSV-2: CD4(+) and CD8(+) cellular immunity and protective efficacy.”

About Herpes

According to the Centers for Disease Control, genital herpes affects more than 60 million

Americans—or 1 in 6 people between ages 14 and 49—with an additional 1.5 million

new cases each year.1 This disease often results in recurrent painful sores in the genital

area.2 The emotional consequences of genital herpes are quite significant, as 82 percent

of people in the study reported depression, 75 percent experienced fear of rejection, 69

percent cited feelings of isolation and 55 percent reported fear of discovery -- all due to

infection.3 Current therapies involve taking a daily medication that only partly

suppresses the virus.

About HerpV

HerpV is a recombinant therapeutic vaccine for the treatment of genital herpes, which is

caused by the herpes simplex virus-2 (HSV-2). The vaccine is based on Agenus' heat

shock protein (HSP) platform technology, and contains Agenus’ proprietary adjuvant QS-

21 Stimulon adjuvant. HSPs, also called stress proteins, are found in all cells (normal

cells, cancer cells and infected cells) and recent research has demonstrated that HSPs play

an essential role in the presentation of pieces of proteins (or peptides) on the cell surface

to help the immune system recognize diseased cells. While the initial focus of

development has been in HSV-2, the HSP technology platform can potentially be utilized

for off-the-shelf treatment of many types of infectious diseases such as HPV, HIV,

hepatitis, malaria and tuberculosis.

HerpV consists of recombinant human heat shock protein-70 complexed with 32 distinct

35-mer synthetic peptides from the HSV-2 proteome. This broad spectrum of herpes

antigens is intended to allow for more accurate immune targeting and surveillance,

reducing the likelihood of immune escape. Further, the diversity of antigens in HerpV

increases the chance of providing efficacy for a wide segment of the patient population.

About QS-21 Stimulon Adjuvant

QS-21 is a vaccine adjuvant designed to strengthen the body's immune response to a

vaccine's antigen, thus making it more effective. QS-21 has become a critical component

in the development of investigational preventive vaccine formulations across a wide

variety of infectious diseases, and appears to be essential for several investigational

therapeutic vaccines intended to treat cancer and degenerative disorders. Currently, QS-

21 is being studied in clinical trials in approximately 15 vaccine indications, of which four are in Phase 3 studies by Agenus' licensees, which include GlaxoSmithKline and

Janssen Alzheimer Immunotherapy, a wholly owned subsidiary of Johnson & Johnson

and Integrated Biotherapeutics. QS-21 represents the most advanced adjuvant currently in

clinical development.

About Agenus

Agenus Inc. is a biotechnology company working to develop treatments for cancers and

infectious diseases. The company is focused on immunotherapeutic products based on

strong platform technologies with multiple product candidates advancing through the

clinic, including several product candidates that have advanced into late-stage clinical

trials through corporate partners. For more information, please visit www.agenusbio.com.

Forward-Looking Statement

This press release contains forward-looking statements, including statements regarding

clinical trial activities, the publication of data, and the potential application of the

Company’s product candidates in the prevention and treatment of diseases. These

forward-looking statements are subject to risks and uncertainties that could cause actual

results to differ materially. These risks and uncertainties include, among others, the

factors described under the Risk Factors section of our Quarterly Report on Form 10-Q

filed with the Securities and Exchange Commission for the period ended June 30, 2011.

Agenus cautions investors not to place considerable reliance on the forward-looking

statements contained in this release. These statements speak only as of the date of this

document, and Agenus undertakes no obligation to update or revise the statements. All

forward-looking statements are expressly qualified in their entirety by this cautionary

statement. Agenus’ business is subject to substantial risks and uncertainties, including

those identified above. When evaluating Agenus’ business and securities, investors

should give careful consideration to these risks and uncertainties.

Stimulon is a registered trademark of Agenus Inc. and its subsidiaries.

 

1 Genital Herpes‐ CDC Fact Sheet; http://www.cdc.gov/std/herpes/stdfact-­‐herpes.htm#common;

accessed July 19,2010

2 Herpes Virus; http://www.herpesonline.org/articles/herpes_virus.html; accessed July 19,2010

3 ASHA survey of people infected with herpes. http://www.thefreelibrary.com/STUDY+SHOWS+GENITAL+HERPES+CAUSES+SIGNIFICANT+EMOTIONAL+STRESS+-­‐-­‐...-­‐a013131235

Contact:

Jonae R. Barnes

617-818-2985