Cetrorelix showed good safety and tolerability profile Reduction of testosterone concentration was maintained above castration level Japanese partner Shionogi initiates Phase 2b trial QUEBEC CITY, March 22 /PRNewswire-FirstCall/ -- AEterna Zentaris Inc. (TSX: AEZ; NASDAQ: AEZS) along with its Japanese partner Shionogi & Co., Ltd. today announced positive results for a Phase 2a trial with cetrorelix in benign prostatic hyperplasia (BPH) initiated in 2005 in Japan. Results showed that cetrorelix, the Company's lead luteinizing hormone-releasing hormone (LHRH) antagonist, was safe and well tolerated at all dosage regimens. Furthermore, Japanese patients responded to cetrorelix with a transient reduction of testosterone concentration in blood, which did not reach or remain at the castration level. Additionally, none of the dosage regimens tested caused a suppression of PSA levels. Finally, data generated with Japanese patients showed that the bioavailability of cetrorelix was similar to that observed in non-Japanese patients. On the basis of this study, Shionogi initiated a 300-patient phase 2b study to assess primarily the efficacy of cetrorelix in BPH in Japanese patients. "We are very pleased with these results which further confirm the positive data observed in prior clinical trials in BPH with cetrorelix in non-Asian patients", said Gilles Gagnon, President and CEO of AEterna Zentaris. "Shionogi's decision to initiate a Phase 2b trial in BPH combined with our own ongoing Phase 3 program with cetrorelix in this same indication, allows us to pursue the development of cetrorelix at an international level and represents an opportunity to potentially gain access to large markets worldwide." Nippon Kayaku, the Company's other Japanese partner, has terminated its agreement with respect to their collaboration with the development of cetrorelix pamoate to focus solely in oncology. About the Phase 2a trial The completed Phase 2a trial with cetrorelix in BPH was designed to evaluate primarily pharmacokinetics and safety (systemic and local tolerability) in Japanese subjects, whereas evaluation of efficacy was only exploratory. In this multicenter, placebo-controlled and randomized trial, the sustained release formulation cetrorelix pamoate was administered intramuscularly as single or multiple dosing schedules. A total of 50 patients were included in 5 dosing groups corresponding to single administration of 30 mg, 60 mg or 90 mg cetrorelix and multiple administration of 60 mg and 90 mg, 3 times 8 weeks apart. The observation period was up to 32 weeks in the multiple administration dosing groups. Results The pharmacokinetic data generated with Japanese patients showed that the bioavailability of cetrorelix after intramuscular cetrorelix pamoate injection is similar to that observed in non-Japanese patients. Similarly, the Japanese patients responded to cetrorelix with a transient reduction of testosterone concentration in blood, which did not reach or remain at the castration level. Intramuscular injection of cetrorelix pamoate was safe and well tolerated at all dosages tested, both locally and systemically. None of the dosage regimens tested caused a suppression of PSA levels which is important considering that a treatment-related suppression would prevent the use of this marker for the routine monitoring of BPH patients for the potential development of prostate cancer. The sizes per dosage group were too small to evaluate efficacy trends for statistical significance. About Benign Prostatic Hyperplasia BPH is characterized by an abnormal benign growth of the prostatic tissues caused by testosterone. Symptoms linked to BPH include pain while urinating and frequent urges to urinate during the night and sometimes, kidney problems. In some cases, if left untreated, BPH may develop into prostate cancer. BPH affects more than 50% of men 60 years and over, with approximately 56 million cases in the U.S., Europe and Japan. In 2004, BPH treatment represented a market size of over US$4 billion. Contrary to most of the present treatments for BPH, cetrorelix is not associated with side-effects such as erectile dysfunction, loss of libido and chemical castration. According to Decision Resource, cetrorelix is currently the most advanced LHRH antagonist in development for the treatment of BPH. About Cetrorelix Cetrorelix is part of AEterna Zentaris' LHRH antagonist therapeutic approach. This peptide-based active substance was developed by the Company in cooperation with Nobel-Prize winner Professor Andrew Schally of the U.S. Veterans Administration in Miami and the University of Miami. Cetrorelix is marketed under the brand name Cetrotide(R), the first LHRH antagonist approved for therapeutic use as part of in vitro fertilization programs (controlled ovulation stimulation/assisted reproductive technologies) in Europe, the USA and Japan. It was launched on the market through Merck Serono in the USA, Europe and in several other countries, as well as in Japan through Shionogi. AEterna Zentaris is currently conducting a large Phase 3 program with cetrorelix in BPH while the Company's partner, Solvay is sponsoring a pivotal clinical program for endometriosis with this same compound. About AEterna Zentaris Inc. AEterna Zentaris Inc. is a late-stage global biopharmaceutical company focused on endocrine therapy and oncology, with proven expertise in drug discovery, development and commercialization. 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. CONTACT: Jenene Thomas, Senior Director, Investor Relations & Corporate Communications, (418) 655-6420, ; Paul Burroughs, Media Relations, (418) 652-8525 ext. 406,

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