Company to further advance the clinical development of ozarelix in this indication QUEBEC CITY, Aug. 2 /PRNewswire-FirstCall/ -- AEterna Zentaris Inc. (TSX: AEZ; NASDAQ: AEZS) today disclosed positive headline data from its Phase 2 trial with ozarelix for patients suffering from hormone-dependent inoperable prostate cancer. This open-label, randomized-controlled Phase 2 dose-finding trial originally designed for 48 patients was extended to 64 patients where 4 groups of 16 patients received different intramuscular dosage regimens of the luteinizing hormone releasing hormone (LHRH) antagonist, ozarelix, to assess its safety and efficacy. The study achieved its primary end-point of defining a tolerable dosage regimen of ozarelix that would ensure continuous suppression of testosterone at castration level (< 0.5 ng/ml) for a three-month test period. An important secondary efficacy end-point of the study aimed at assessing tumour response as determined by a 50% or greater reduction of serum PSA levels, compared to baseline, was also achieved. The trial was conducted in Europe in collaboration with AEterna Zentaris' partner Spectrum Pharmaceuticals Inc. (NASDAQ:SPPI). In this study, ozarelix IM 65 mg, 100 mg or 130 mg was administered according to different dosing schedules and repeated for 3 cycles of 28 days. The total dose by patient during the study ranged from 230 mg to 390 mg. The best results regarding the primary end-point of continuous suppression of testosterone were obtained at the upper limit of that range and especially with a dose of 130 mg per cycle where all patients remained suppressed to castration until at least day 85. Furthermore, in patients with continuous testosterone suppression below castration level, tumour response as measured by PSA levels was 97%. Ozarelix was well tolerated at all dosages. The detailed results from the study will be presented at the upcoming SIU (Societe internationale d'urologie) meeting in Cape Town, South Africa, on November 12, 2006. The Company has initiated, in collaboration with its partner Spectrum Pharmaceuticals, an additional study which will enroll 32 patients at other European clinical sites to verify and optimize the findings derived from the cohort of patients having received 130 mg of ozarelix per cycle. "We are very excited with these results which confirm the mechanism of action of our LHRH antagonist approach and the potential effectiveness of ozarelix to achieve sustained suppression of sexual hormones at castration levels and, consequently, could allow for the treatment of hormone-dependent cancers. Now that we have a suitable dosage regimen of ozarelix for the potential treatment of prostate cancer, we are pleased to further advance the clinical development of ozarelix in this indication with a Phase 2b program," commented Dr. Jurgen Engel, Executive Vice President, Global R&D and Chief Operating Officer at AEterna Zentaris. "These positive results further validate the potential of our LHRH antagonist approach and strengthen ozarelix's position as a lead compound in our portfolio," stated Gilles Gagnon, President and Chief Executive Officer at AEterna Zentaris. "We are now in an even better position to execute our strategy in building a strong oncology franchise." About Ozarelix (D-63153) and Development Alliance with Spectrum Pharmaceuticals Ozarelix (D-63153) is a fourth generation luteinizing hormone releasing hormone (LHRH) antagonist administered as a depot formulation for the treatment of hormone-dependent prostate cancer. In August 2004, AEterna Zentaris granted Spectrum Pharmaceuticals an exclusive license to develop and market ozarelix (D-63153) for all potential indications in North America and India while AEterna Zentaris retains exclusive rights to the rest of the world. About Prostate Cancer According to Decision Resource, 395,000 new cases of prostate cancer were diagnosed in 2005 in the 7 major markets around the world. Treatment costs in these markets for this indication in 2005 were estimated at some US$3.3 billion. About AEterna Zentaris Inc. AEterna Zentaris Inc. is a growing global biopharmaceutical company focused on oncology and endocrine therapy with proven expertise in drug discovery, development and commercialization. AEterna Zentaris also owns 48.26% of the equity of Atrium Biotechnologies Inc. (TSX: ATB) and 64.69% of its voting rights. Atrium is a developer, manufacturer and marketer of science-based products for the cosmetics, pharmaceutical, chemical and nutritional industries. News releases and additional information are available at http://www.aeternazentaris.com/. Forward-Looking Statements This press release contains forward-looking statements made pursuant to the safe harbor provisions of the U.S. Securities Litigation Reform Act of 1995. Forward-looking statements involve known and unknown risks and uncertainties, which 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 the 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. DATASOURCE: AETERNA ZENTARIS INC. (FORMERLY/ANCIENNEMENT - LES LABORATOIRES AETERNA LABORATORIES INC.) CONTACT: Media Relations: Paul Burroughs, (418) 652-8525 ext. 406, ; Investor Relations: Jenene Thomas, (418) 655-6420 or (908) 996-3154,

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