Orsay, 25 April 2005 Immutep S.A. announced today that its lead product ImmuFact IMP321 has moved into Phase I/II clinical trials. ImmuFact(R) IMP321 is a potent natural human T cell immunostimulatory factor designed to amplify the T cell immune response in therapeutic vaccines.

The two randomised single-blind escalating-dose Phase I/II studies are designed to show first, safety and tolerability, and second, to assess the T cell immune response. Studies are being conducted in healthy individuals with ImmuFact(R) IMP321 alone and combined with antigens. Two well-defined standard types of antigens are being used: soluble influenza virus antigens and the particulate hepatitis B surface antigen. Immutep and its partners will use the resulting data in the development of therapeutic vaccines against cancer and infectious diseases. The Company has set up a state-of-the-art immunomonitoring facility to measure a wide range of immune response parameters. Recruitment of 108 healthy volunteers started in April and the trials will be completed in Q4 2005.

"We are delighted with the rapid progress of our lead product into a major clinical study which will demonstrate the clinical potential of our approach," said Frédéric Triebel, Scientific & Medical Director of Immutep. "Fast and successful production development, problem-free toxicology and a smooth regulatory path enabled us to go from first financing to the clinic in 15 months."

The clinical study is being carried out at Aster-Cephac, a leading European contract research organisation in Paris, specialised in early-stage drug development.

The cGMP batch of IMP321 was produced by Henogen S.A. (Gosselies, Belgium) in Chinese hamster ovary (CHO) cells. As IMP321 is used at low dose levels (<100 µg/injection), the batch will be sufficient for a number of clinical trials by Immutep and its partners.

Immutep S.A. is a biopharmaceutical company primarily focussed on the discovery and development of novel therapeutic vaccines for the treatment of cancer and chronic infectious diseases. The Company's technologies are based on the properties of LAG-3, a key mediator of the T cell immune response. One of LAG-3's major roles is to stimulate dendritic cells leading to the T cell immune response required to kill tumours and infected cells. Immutep is developing therapeutic vaccines both in-house and in partnership with pharmaceutical and biotech companies.

For further information please visit the web-site www.immutep.com or e-mail John Hawken, CEO, at JBHawken@immutep.com.

Immutep S.A.
The Company was formed in 2001 by Frédéric Triebel, the scientific founder, and John B. Hawken, a specialist in the management of biotech start-ups, and has its headquarters and research facilities near Paris, France. Immutep is backed by the Paris-based venture capital firm Innoven Partenaires and the venture capital fund H2I, a specialist Biotech fund managed by Unicorn Biotutors/Equitis (Paris). Further support for the Company's development came from grants from the French Ministry of Research and Anvar Ile de France Ouest.

The Technology
Immutep S.A. is developing a range of products derived from LAG-3 (CD223), an immunomodulatory protein expressed on the surface of T cells. LAG-3 was discovered by Professor Triebel in his Inserm laboratory at Institut Gustave Roussy (IGR, Villejuif, France) and his laboratory at the Faculty of Pharmacy in Châtenay-Malabry (University Paris 11). The Company has three unique proprietary product platforms making use of the key roles played by this natural human protein in the regulation of the immune system. The first two technologies (ImmuFact and ImmuCcine) take advantage of the immunostimulatory properties of the free molecule to create potent therapeutic vaccines. The principal difficulty in designing effective therapeutic vaccines is that the antigens displayed on the surface of a tumour or an infected cell are insufficiently immunogenic. Dendritic cells (DC) are key mediators in determining the strength of the immune response to an antigen. Immutep's first two technologies provide solutions to the problem of insufficient immunogenicity by dramatically increasing the efficiency of DC as antigen presenting cells. Immutep's third technology exploits LAG-3-specific antibodies to modulate signalling of the membrane-bound molecule into activated T cells or regulatory T cells (Treg cells) to control the T cell response.

ImmuFact - T cell Immunostimulatory Factors for amplifying the T cell response to any antigen
The Company's lead product, IMP321, is a highly potent T cell immunostimulatory factor derived from the soluble form of LAG-3 that binds, with high affinity, to MHC class II molecules expressed by DC. This binding leads to DC maturation, migration to the lymph nodes and enhanced presentation of antigens to T cells. As a result, strong and sustained anti-tumour or anti-viral cytotoxic T cell responses are obtained when IMP321 is coinjected with either tumour cells or protein or DNA antigens.

ImmuCcine - Immunostimulatory Vaccines
The Company is developing a second patented technology that will make it possible to design novel therapeutic vaccines with even greater potency and efficacy. Covalently linking an antigen to IMP321 in a fusion protein results in both vectorisation of the antigen to the DC as well as the immunostimulatory effect described above. These dual action vaccines will be particularly useful in very difficult cases like HIV.

Therapeutic vaccines
Therapeutic vaccines, also known as "Specific Active Immunotherapies", are a new therapeutic approach to diseases like cancer and chronic infection. Therapeutic vaccines harness the patient's immune system to attack the tumour or infected cell. A long period of trial and error has taught the industry that the assembly of a therapeutic vaccine is critical and necessitates combining several key components. Typically these include validated antigens with or without a vectorisation system and a powerful immune potentiator. The first therapeutic vaccines approved for marketing are cell-based vaccines and several more may be registered in the next 12-18 months marking the beginning of the most significant therapeutic innovation in the field of immunotherapy since the registration of the first therapeutic monoclonal antibodies in the late 90's for "passive immunotherapy".

aster.cephac
aster.cephac is a full service provider of clinical pharmacology trials and bioanalytical services. Since 1975, aster.cephac has served the pharmaceutical and biotechnology industries with expertise and innovation as an early phase clinical trial specialist with strong cardiovascular expertise (QT/QTc) and has become the largest bioanalytical unit in Europe. (www.aster-cephac.com)

Henogen S.A.
Henogen is a biotech company addressing biomanufacturing issues under the general umbrella "from gene to clinical product". The Company has extensive knowledge in performing and/or accompanying partners through the R&D, process development, cGMP production and Phase I to III clinical trials. Among the products previously developed and produced are recombinant proteins, gene therapy viral vectors, vaccines and monoclonal antibodies. ( www.henogen.com )

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