GSK’s Vaccine Candidate Containing Agenus’ QS-21 Stimulon® Reduces Malaria Infection in Phase 3 Trials of Over 15,000

  GSK’s Vaccine Candidate Containing Agenus’ QS-21 Stimulon® Reduces Malaria
  Infection in Phase 3 Trials of Over 15,000 Children

  *Significant protection shown 18 months post vaccination
  *RTS,S vaccine could have a major public health impact on malaria in Africa
  *GSK plans regulatory submission in 2014
  *Agenus entitled to receive milestone payment and royalties upon launch

Business Wire

LEXINGTON, Mass. -- October 7, 2013

Agenus Inc. (NASDAQ: AGEN) today announced that new Phase 3 data for
GlaxoSmithKline’s (NYSE: GSK) RTS,S malaria vaccine candidate, which contains
Agenus’ QS-21 Stimulon^®1 adjuvant, were presented at a Multilateral
Initiative on Malaria Pan African Conference in Durban, South Africa. The
abstract and presentation titled, “Efficacy of RTS,S/AS01 vaccine candidate
against malaria in African infants and children 18 months post-primary
vaccination series: a Phase 3 randomized, double-blind controlled trial,”
shows that RTS,S helped protect young children and infants from clinical
malaria up to 18 months post vaccination. RTS,S is the most advanced malaria
vaccine candidate in the world and the first vaccine candidate to show in
clinical trials that it can help protect young children and infants living in
malaria-endemic areas against clinical disease and infection caused by
Plasmodium falciparum. Malaria claims over 600,000 lives a year, most of which
are children in Sub-Saharan Africa.^2

“These findings indicate that RTS,S has the potential to help prevent millions
of malaria cases. We are very pleased that our QS-21 Stimulon adjuvant is a
key component of AS01, a proprietary adjuvant system used in RTS,S,” said Garo
H. Armen, Ph.D., Chairman and CEO of Agenus Inc. “These results provide
further support that QS-21 Stimulon can help advance challenging development
programs targeting difficult diseases. Currently there are 21 development
programs underway involving vaccines that include QS-21 Stimulon for many
different types of cancer, infectious diseases and degenerative disorders.”

RTS,S Efficacy

For the first time, the efficacy of the vaccine candidate was assessed at each
trial site separately, which are in regions with different levels of malaria
disease. Efficacy was found to be statistically significant at all sites in
young children and at four sites in infants.

According to the results, children aged 5-17 months at first vaccination with
RTS,S experienced 46% fewer cases of clinical malaria, compared to children
immunized with a control vaccine. Recognizing that children can each be
affected by more than one case of malaria, this results in 941 cases of
clinical malaria prevented over 18 months of follow-up for every 1,000
children vaccinated. Severe malaria cases were reduced by 36%, resulting in 21
cases of severe malaria prevented over 18 months of follow-up for every 1,000
children vaccinated. Malaria hospitalizations were reduced by 42%. These
results in children 5-17 months were statistically significant.

Infants aged 6-12 weeks at first vaccination with RTS,S had 27% fewer cases of
clinical malaria, resulting in 444 cases of clinical malaria prevented over 18
months of follow-up for every 1,000 infants vaccinated. The reduction of
severe malaria cases and malaria hospitalizations by 15% and 17%,
respectively, were not statistically significant.

The reduction in number of malaria cases attributed to RTS,S was demonstrated
in addition to the effect of existing malaria control measures such as
insecticide treated bed nets that were used by 78% of children and 86% of
infants in the trial.

Previous results from one year follow-up of the Phase 3 trial showed that
efficacy of RTS,S was 56% against clinical malaria and 47% against severe
malaria for the 5-17 month-old age group and 31% against clinical malaria and
37% against severe malaria in the 6-12 week-old age group.

RTS,S continued to display an acceptable safety and tolerability profile
during the 18 month follow-up. No new safety signals were observed during this
longer follow-up period. The incidence of severe adverse events overall was
similar in participants in each group but the imbalance in reported cases of
meningitis, noted previously^3, has persisted.

Further data from 32 months follow-up and the impact of a ‘booster’ dose given
after 18 months are expected to become available in 2014.

About RTS,S

RTS,S is a scientific name given to this malaria vaccine candidate and
represents the composition of this vaccine candidate that also contains the
AS01 adjuvant system.^4 RTS,S aims to trigger the immune system to defend
against the 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 time the parasite would re-enter the bloodstream and
infect red blood cells, leading to disease symptoms.

These new data support GSK’s plans to submit a regulatory application in 2014
for a Scientific Opinion of the European Medicines Agency (EMA) on RTS,S
safety, efficacy and quality. If the EMA give a positive opinion, and there is
satisfactory public health information from the Phase 3 program, the World
Health Organization has indicated that a policy recommendation for the RTS,S
malaria vaccine candidate is possible in 2015, paving the way for potential
decisions by African nations for large-scale implementation of the vaccine
through their national immunization programs.

About GlaxoSmithKline

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

About Agenus’ QS-21 Stimulon^® Adjuvant

Agenus’ flagship adjuvant, QS-21 Stimulon adjuvant, 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’
GMP QS-21 Stimulon 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 has been widely studied and approximately 50,000 patients have
received vaccines containing the adjuvant. QS-21 Stimulon is being studied in
21 vaccine indications, which 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, and Agenus’ HerpV, a therapeutic vaccine for the
treatment of genital herpes, is in a Phase 2 trial. Agenus is generally
entitled to receive milestone payments as QS-21 Stimulon containing programs
advance, as well as royalties for 10 years after commercial launch, with some
exceptions.

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.
Between Agenus and its partners, 23 programs are in clinical development. For
more information, please visit www.agenusbio.com, or connect with the company
on Facebook, LinkedIn, Twitter and Google+.

1. QS-21 Stimulon^® adjuvant and the related agreements, and HerpV are assets
of Antigenics Inc., a wholly owned subsidiary of Agenus Inc.

2. http://www.who.int/malaria/world_malaria_report_2011/en/index.html

3. The RTS,S Clinical Trials Partnership. NEJM. 2011; DOI
10.1056/NEJMoa1102287; The RTS,S Clinical Trials Partnership. NEJM. 2012; DOI:
10.1056/NEJMoa1208394

4. The GSK proprietary AS01 adjuvant system contains QS-21 Stimulon^®
adjuvant, MPL and liposomes. Stimulon is a registered trademark of Agenus Inc.
and its subsidiaries.

Forward-Looking Statement

This press release contains forward-looking statements, including statements
regarding the potential application product candidates containing the
Company’s QS-21 Stimulon Adjuvant in the prevention and treatment of diseases,
and revenue streams to Agenus in connection therewith. 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, 2013. 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.

Contact:

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