Aeterna Zentaris Presents Positive Preclinical Data in Breast Cancer on AEZS-131, a Highly Selective Erk 1/2 Inhibitor, at San Antonio Breast Cancer Symposium

QUEBEC CITY, Dec. 9, 2011 /PRNewswire/ - Aeterna Zentaris Inc. (NASDAQ: AEZS) (TSX: AEZ) (the "Company") today announced positive preclinical data in triple-negative breast cancer (TNBC) for its highly selective Erk 1/2 inhibitor anticancer compound, AEZS-131. Data showed that AEZS-131 selectively inhibits Erk at low nanomolar (nM) concentrations and induces G1 arrest. Accordingly, the cytotoxic effect of AEZS-131 was most pronounced in TNBC cell lines with mutations in the MAPK pathway. Data were presented yesterday by Dr. Jörg B. Engel, Medical University of Regensburg, Department of Gynaecology and Obstetrics, Germany, during a poster session at the CTRC - AACR San Antonio Breast Cancer Symposium, in San Antonio, Texas.

The Study

AEZS-131 was tested to check for selectivity, inhibition of Rsk-phosphorylation (cellular substrate of Erk), mode of action and cleavage of PARP. Cytotoxic efficacy was evaluated in a selection of TNBC cell lines, with or without mutations in the MAPK signal transduction pathway, by MTT assay.

Results

The study showed that AEZS-131 selectively inhibited ERK with an IC₅₀<4nM. Phosphorylation of Rsk-1, the cellular substrate of Erk, was inhibited with an IC₅₀ of 158 nM. AEZS-131 induced cell cycle arrest in G1 dose-dependently and cleavage of PARP. EC₅₀ values were below 1µM for cell lines with mutations in the MAPK pathway. TNBC cell lines without mutations in the MAPK pathway were less responsive.

Dr. Jörg B. Engel, of the Medical University of Regensburg, commented, "Over-expression of MAPK has been detected in 34% of triple-negative breast cancer and has been found to be associated with an increased risk for recurrence in patients with this type of breast cancer. Since preclinical data suggest that AEZS-131's cytotoxic effect was most pronounced in triple-negative breast cancer cell lines with mutations in the MAPK pathway, we, therefore, believe this compound should be further explored in triple-negative breast cancer with over activation of MAPK or mutations in the MAPK-pathway."

The poster is available at the following link.

About Erk 1/2 Inhibitor Compound

Extracellular signal-regulated kinases ("Erks") act in the Ras-Raf-Mek-Erk signaling cascade and regulate various cellular processes such as cell growth, proliferation and survival in response to a variety of extracellular or intrinsically mutated upstream signals. Aeterna Zentaris has identified small molecular compounds that selectively inhibit Erk 1/2, among them AEZS-131, which has been shown to significantly inhibit tumor growth in in vivo studies. Early development of the Erk inhibitor AEZS-131 is an integral part of Aeterna Zentaris' kinase research program comprising the investigation of different compounds for single Erk inhibition, single PI3K inhibition and dual Erk/PI3K kinase inhibition.

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 risk that safety and efficacy data from any of our Phase 3 trials may not coincide with the data analyses from previously reported Phase 1 and/or Phase 2 clinical trials, 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.

SOURCE AETERNA ZENTARIS INC.