All amounts are in U.S. dollars (unless otherwise noted)

QEBEC City, Canada I July 31, 2013 I Aeterna Zentaris Inc. (NASDAQ: AEZS, TSX: AEZ) (the “Company”) today announced that the first patient has been recruited and dosed for the Phase 3 ZoptEC (Zoptarelin doxorubicin in Endometrial Cancer) trial in women with endometrial cancer resistant to platinum/taxane-based chemotherapy.

“We have reached another important milestone in the final clinical development stage for zoptarelin doxorubicin (AEZS-108) in treating endometrial cancer. Efforts are now focused on pursuing patient recruitment as swiftly as possible”, stated David Dodd, President and CEO of Aeterna Zentaris. “This compound’s innovative targeted approach potentially offers a much needed novel treatment option for women with endometrial cancer and it provides the Company with a significant market opportunity.”

The Study

This is an open-label, randomized, multicenter Phase 3 trial to be conducted in over 120 sites in North America, Europe, Israel and other countries under a Special Protocol Assessment, comparing zoptarelin doxorubicin (AEZS 108) with doxorubicin as second line therapy for locally-advanced, recurrent or metastatic endometrial cancer. Lead investigators are David Scott Miller, MD, from the University of Texas Southwestern Medical Center, in Dallas, Texas, and Hani Gabra, MD, from the Imperial College London Hammersmith Campus in London, England. The trial will involve approximately 500 patients and the primary efficacy endpoint is improvement in median Overall Survival.

Selected as the contract clinical development organization, Ergomed will also assume 30% (up to $10 million) of the clinical and regulatory costs for this trial.

Details for this trial are available at www.clinicaltrials.gov (NCT01767155).

About Zoptarelin Doxorubicin (AEZS-108)

Zoptarelin doxorubicin (AEZS-108) represents a new targeting concept in oncology using a hybrid molecule composed of a synthetic peptide carrier and a well-known chemotherapy agent, doxorubicin. Zoptarelin doxorubicin (AEZS-108) is the first intravenous drug in advanced clinical development that directs the chemotherapy agent specifically to LHRH-receptor expressing tumors, resulting in a more targeted treatment with less damage to healthy tissue. The Company is currently conducting a Phase 3 trial in endometrial cancer under a Special Protocol Assessment, while zoptarelin doxorubicin (AEZS 108) is also in Phase 2 trials for triple-negative breast cancer, prostate cancer and bladder cancer. Aeterna Zentaris owns the worldwide rights to zoptarelin doxorubicin (AEZS-108).

About Endometrial Cancer

Endometrial cancer is the most common gynecologic malignancy and develops when abnormal cells amass to form a tumor in the lining of the uterus. It largely affects women over the age of 50 with a higher prevalence in Caucasians and a higher mortality rate among African Americans. Approximately one in 30 women is diagnosed with endometrial cancer every year. According to the American Cancer Society, an estimated 49,560 new cases of endometrial cancer in the U.S., and 35,600 in Europe, are expected during 2013, with about 20% of recurring disease.

About Aeterna Zentaris

Aeterna Zentaris is a specialty biopharmaceutical company engaged in developing novel treatments in oncology and endocrinology. The Company’s pipeline encompasses compounds from drug discovery to regulatory approval. For more information, visit www.aezsinc.com

SOURCE: Aeterna Zentaris