Efficacy Shown With GlaxoSmithKline's Phase 3 Malaria Vaccine Candidate, Which Contains Agenus' Qs-21 Stimulon(R) ADJUVANT

Efficacy Shown With GlaxoSmithKline's Phase 3 Malaria Vaccine Candidate, Which
Contains Agenus' Qs-21 Stimulon(R) ADJUVANT

  *Phase 3 study met its primary endpoint and demonstrates statistically
    significant protection against clinical and severe malaria in infants
  *Contains Agenus' QS-21 Stimulon^1 adjuvant currently being studied in 17
    clinical programs, including four Phase 3 studies by GlaxoSmithKline (GSK)

LEXINGTON, Mass., Nov. 9, 2012 (GLOBE NEWSWIRE) -- Agenus Inc. (Nasdaq:AGEN),
a developer of therapeutic vaccines for cancer and infectious diseases, today
announced the second complete set of results from the Phase 3 trial of
GlaxoSmithKline's (NYSE:GSK) RTS,S malaria vaccine candidate (also known as
Mosquirix^™), which contains Agenus' QS-21 Stimulon adjuvant, were published
online in the New England Journal of Medicine and announced at the
International Vaccines for Africa Conference in Cape Town, South Africa. QS-21
Stimulon is a component of AS01, one of GSK's proprietary adjuvant systems
used in RTS,S.

In this trial, infants (aged 6-12 weeks at first vaccination) receiving the
RTS,S vaccine candidate experienced one-third fewer episodes of both clinical
and severe malaria and experienced similar reactions to the injection when
compared to those who received the control meningococcal C conjugate vaccine.
Insecticide-treated bed nets were used by 86% of the trial participants
demonstrating that RTS,S provided protection beyond existing malaria control
interventions.

The results of this trial are part of the largest malaria vaccine efficacy and
safety study ever conducted in Africa to date and included 15,460 children.
The trial includes 11 African research centers in seven African countries^2
with GSK and its partners.

Malaria is responsible for approximately 655,000 deaths each year, most of
whom are children under the age of five in sub-Saharan Africa. If approved by
regulatory authorities, the World Health Organization (WHO) has indicated that
a policy recommendation for the RTS,S malaria vaccine candidate is possible as
early as 2015.

"We are very pleased to be a part of this important breakthrough, which has
the potential to prevent millions of malaria cases," said Garo H. Armen,
Ph.D., Chairman and CEO of Agenus Inc. "QS-21 Stimulon has become a key
component of many vaccines in clinical development; over the next year we
expect additional, pivotal data from multiple important clinical programs that
are being developed by us and our corporate partners."

Agenus' QS-21 adjuvant is an important component contained in a substantial
number of GSK's vaccines currently in clinical development, including four GSK
programs that are in Phase 3 studies. Agenus is entitled to receive milestone
payments as QS-21-containing programs advance, as well as royalties for 10
years after commercial launch, with some exceptions.

About GSK's RTS,S Program

When administered with standard childhood vaccines in the Phase 3 study^3,
efficacy of the RTS,S vaccine candidate against clinical and severe malaria in
infants aged 6 to 12 weeks was 31% (clinical) and 37% (severe)^4 over 12
months of follow-up after the third vaccine dose.^5 Results published inthe
New England Journal of Medicine in November 2011 showed that efficacy against
clinical and severe disease in children 5-17 months of age at the time of
first vaccination was higher and demonstrated that clinical and severe malaria
cases were reduced by approximately half. Both co-primary endpoints in the
large ongoing efficacy trial were met.

Follow-up for this trial will continue and should provide more data for
analyses to better understand the different findings between the age
categories and insights into RTS,S' efficacy in areas with differences in
malaria prevalence. Longer-term efficacy data of the vaccine during 30 months
of follow-up after the third dose, and the impact of a booster dose, are
expected to be available at the end of 2014.

RTS,S is a scientific name given to this malaria vaccine candidate and
represents its composition. RTS,S aims to trigger the immune system to defend
against Plasmodium falciparum malaria parasite when it first enters the human
host's bloodstream and/or when the parasite infects liver cells. It is
designed to prevent the parasite from infecting, maturing and multiplying in
the liver, after which the parasite would re-enter the bloodstream, infect red
blood cells, and start causing symptoms of the disease.

RTS,S Safety Profile

There was no increase in overall reporting of serious adverse events^6 (SAEs)
between the infants vaccinated with the RTS,S malaria vaccine candidate and
infants in the control group, which received a comparator vaccine. Side
effects following vaccination primarily included local injection site
reactions, which were less frequent in RTS,S vaccinations compared to the
DTP-HepB/Hib vaccine; and fever, which was more frequent in RTS,S than the
control vaccine group (following 30.6% versus 21.1% of vaccine doses,
respectively).

Two new cases of meningitis were reported in the 6-12 week-old infant age
category in addition to the 9 reported last year; one in the RTS,S group and
one in the control vaccine group. Further analysis revealed a bacterial cause
of the meningitis in 7 of the 11 cases.

For additional information on RTS,S, please visit GSK's website at
www.gsk.com.

About Agenus' QS-21 Stimulon^® Adjuvant

Agenus' flagship adjuvant, QS-21 Stimulon, is a saponin extracted from the
bark of the Quillaja saponaria tree, also known as the soap bark tree or
Soapbark, an evergreen tree native to warm temperate central Chile. Agenus'
QS-21 has become a key 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. QS-21 Stimulon adjuvant
has been widely studied in clinical development and tens of thousands of
patients have received vaccines containing the adjuvant. QS-21 Stimulon
adjuvant is being studied in clinical trials for approximately 17 vaccine
programs and include GSK's Phase 3 vaccine programs for RTS,S for malaria,
MAGE-A3 cancer immunotherapeutic for non-small cell lung cancer and melanoma
and HZ/su for shingles. In addition, Janssen's QS-21 Stimulon
adjuvant-containing vaccine candidate is in Phase 2 trials for the treatment
of Alzheimer's disease. HerpV, Agenus' novel QS-21 containing therapeutic
vaccine candidate for the treatment of genital herpes, is in a Phase 2 trial.

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.

The Agenus logo is available at
http://www.globenewswire.com/newsroom/prs/?pkgid=8187

About GSK Vaccines

GlaxoSmithKline Vaccines is active in vaccine research and development.
Headquartered in Belgium, GSK Vaccines has 14 manufacturing sites
strategically positioned around the globe. Of the 1.1 billion doses of
vaccines GSK distributed in 2011, over 80% went to developing countries which
include the least developed, low and middle income countries.

GlaxoSmithKline – one of the world's leading research-based pharmaceutical and
healthcare companies – is committed to improving the quality of human life by
enabling people to do more, feel better and live longer.For further
information please visit www.gsk.com

Forward-Looking Statement 

This press release contains forward-looking statements, including statements
regarding clinical trial activities, the availability of data, the potential
application of the Company's technologies and product candidates in the
prevention and treatment of diseases, and the timelines and impact of such
product candidates being available to patients and associated revenue streams
to the Company. 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 September 30, 2012.
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.

^1QS-21 Stimulon^® adjuvant is an asset of Antigenics, Inc., a wholly owned
subsidiary of Agenus Inc.
^2Burkina Faso, Nanoro, Institut de Recherche en Science de la Santé (IRSS) /
Centre Muraz
Gabon, Lambaréné Albert Schweitzer Hospital, Medical Research Unit
Ghana – Agogo/Kumasi: School of Medical Sciences, Kwame Nkrumah University of
Science and Technology; Kumasi Centre for Collaborative Research, Agogo
Presbyterian Hospital
Ghana – Kintampo:Kintampo Health Research Centre, Ghana Health Service
Kenya – Kilifi,KEMRI-Wellcome TrustResearch Program
Kenya – Kombewa (Kisumu),KEMRI-Walter Reed Project Kenya Medical Research
Institute
Kenya – Siaya (Kisumu),KEMRI-CDCResearch and Public Health Collaboration
Malawi – Lilongwe,University of North Carolina Project at the Tidziwe Centre
Mozambique – Manhica, Centro de Investigação em Saúde de Manhiça
Tanzania – Bagamoyo,Ifakara Health Institute
Tanzania – Korogwe,National Institute for Medical Research, Tanzania,
Kilimanjaro Christian Medical Centre

^3Standard childhood vaccines used were the combined
diphtheria-tetanus-whole-cell-pertussis, hepatitis B, and Haemophilus
influenzae type b vaccine (DTPwHepB/Hib) and the oral polio virus vaccine
(OPV)

^4Based on According To Protocol (ATP) statistical methodology

^5Average risk for malaria in the control group was 0.9 clinical episodes per
child per year and 2.3% of the children experienced at least one episode of
severe malaria

^6A serious adverse event refers to any medical event that occurs during the
course of a clinical trial and results in death, is life threatening, requires
inpatient hospitalization, or results in a persistent or significant
disability or incapacity needs, regardless of whether the event is considered
by the investigator to be caused by the study vaccination. All SAEs are
reported to regulatory authorities.

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

CONTACT: Media and Investor Contact:
         Jonae R. Barnes
         Vice President
         Investor Relations and Corporate Communications
         jonae.barnes@agenusbio.com
         617-818-2985

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