July 20, 2011

Aeterna Zentaris Successfully Reached a Key Milestone in the Non-Clinical Development of its Oral Prostate Cancer Vaccine Candidate, AEZS-120

All amounts are in US dollars

QUEBEC CITY, July 20, 2011 /PRNewswire/ - Aeterna Zentaris Inc. (NASDAQ:
AEZS) (TSX: AEZ) (the "Company") today announced that it has
successfully reached a key milestone in the non-clinical development of
its live recombinant prostate cancer vaccine candidate, AEZS-120, for
oral administration. The program, partially funded through a grant from
the German government, encompassed the full development of a GMP
process, including GMP production and quality testing of a clinical
batch, as well as a non-clinical safety and toxicology package, as
previously agreed with regulatory authorities. Subject to a positive
review by German regulatory authorities, the Company aims to start
Phase I clinical development in 2012.

The principle of AEZS-120 is based on the recombinant expression and
secretion of the prostate specific antigen (PSA) in the approved
attenuated vaccine strain Salmonella typhi Ty21a using a proprietary technology. The technology allows for the
expression and secretion of an antigen genetically coupled to the
non-toxic B subunit of cholera toxin to enhance immunogenicity. In
principle, this platform technology is suitable for any prophylactic or
therapeutic vaccine indication by varying the antigen.

AEZS-120 has been developed through a research collaboration with the
Department of Medical Radiation Biology and Cell Research, and the
Department of Microbiology of the University of Wrzburg, Germany. The
collaboration was funded with a total of $890,000 for Aeterna Zentaris
and $870,000 for the university partner by the German Ministry of
Education and Research (BMBF) for a period of three years. As part of
the collaboration, a melanoma vaccine based on the recombinant
expression of a modified B-Raf protein has been generated.

Juergen Engel, Ph.D., President and CEO of Aeterna Zentaris stated, "We
are very enthusiastic about the potential of AEZS-120 which represents
the first off-the shelf oral tumor vaccine in development and offers a
favorable cost profile compared to individualized tumor vaccines. We
believe that this successful key non-clinical milestone for AEZS-120
validates our strategy of employing public grants for the early
development of highly innovative therapies."

Joachim Fensterle, Ph.D., Director, Head of Vaccine Development at
Aeterna Zentaris and spokesperson for the research consortium added,
"We now plan to fully complete the non-clinical package and discuss the
data with regulatory authorities. Following a positive outcome of these
discussions, we aim to file a clinical trial application at the
beginning of 2012."

About AEZS-120

AEZS-120 is a live recombinant oral tumor vaccine candidate based on Salmonella typhi Ty21a as a carrier strain. Salmonella typhi Ty21a is an approved oral typhoid vaccine which has been safely applied
in more than 350 million doses. The principle of AEZS-120 is based on
the recombinant expression of prostate specific antigen fused to the B
subunit of cholera toxin and a secretion signal in the presence of the Escherichia coli type I hemolysin secretion system. The proprietary system allows the
secretion of the antigen together with an immunological adjuvant which
has been demonstrated to be required for optimal induction of CD8
T-cell responses by recombinant Salmonella based bacterial vaccines. The proof-of-concept was already demonstrated
for the mouse homologue of AEZS-120 in a mouse tumor challenge model.

In general, by varying the antigen and/or the carrier, this proprietary
platform technology is suitable for virtually any therapeutic or
prophylactic vaccine indication with a relatively favorable cost of
goods expectation in large scale.

About Aeterna Zentaris Inc.

Aeterna Zentaris is a late-stage oncology drug development company
currently investigating potential treatments for various cancers
including colorectal, multiple myeloma, endometrial, ovarian, prostate
and bladder cancer. The Company's innovative approach of "personalized
medicine" means tailoring treatments to a patient's specific condition
and to unmet medical needs. Aeterna Zentaris' deep pipeline is drawn
from its proprietary discovery unit providing the Company with constant
and long-term access to state-of-the-art therapeutic options. For more
information please visit www.aezsinc.com.

Forward-Looking Statements

This press release contains forward-looking statements made pursuant to
the safe harbour provisions of the U.S. Securities Litigation Reform
Act of 1995. Forward-looking statements involve known and unknown risks
and uncertainties that could cause the Company's actual results to
differ materially from those in the forward-looking statements. Such
risks and uncertainties include, among others, the availability of
funds and resources to pursue R&D projects, the successful and timely
completion of clinical studies, the ability of the Company to take
advantage of business opportunities in the pharmaceutical industry,
uncertainties related to the regulatory process and general changes in
economic conditions. Investors should consult the Company's quarterly
and annual filings with the Canadian and U.S. securities commissions
for additional information on risks and uncertainties relating to
forward-looking statements. Investors are cautioned not to rely on
these forward-looking statements. The Company does not undertake to
update these forward-looking statements. We disclaim any obligation to
update any such factors or to publicly announce the result of any
revisions to any of the forward-looking statements contained herein to
reflect future results, events or developments, unless required to do
so by a governmental authority or by applicable law.