Bcl-2 Antagonist shown to be therapeutically effective in a mouse model of Chronic Lymphocytic Leukaemia

Copenhagen, 18 April 2007, Santaris Pharma, the Danish biopharmaceutical company developing RNAi drugs, yesterday presented encouraging data at the American Association for Cancer Research Annual Meeting in Los Angeles, showing that SPC2996, the Company’s RNA Antagonist of Bcl-2, is therapeutically active in a preclinical model of human Chronic Lymphocytic Leukaemia (CLL).

In collaboration with scientists at the University of Duisberg-Essen in Germany, Santaris researchers reported that white blood cells obtained from CLL patient peripheral blood can be transplanted into immunodeficient mice and reliable engraftment of human CLL cells achieved in the spleen, resulting in focal aggregates of B-lymphocytes carrying surface markers characteristic of CLL cancer cells.

SPC2996 was tested for anti-leukaemic activity over two weeks in this model starting two weeks after transplantation and compared for efficacy with multiple doses of fludarabine, a standard chemotherapy for CLL, as well as a negative control oligonucleotide drug similar to but of different sequence from SPC2996. Therapy with SPC2996 resulted in a 54% reduction (p=0.043) in the number of CLL cells which could be recovered from the spleens of the treated transplanted animals compared to animals not receiving therapy. Fludarabine was also effective in the model whereas the negative control drug was not.

This is the first time that primary CLL cells taken from patient blood have been successfully transplanted and shown long term splenic engraftment in an animal model. The model appears to be validated by the efficacy of the fludarabine in clearing engrafted human CLL cells. The demonstration that single agent therapy with SPC2996,

a non-chemotoxic agent inhibiting Bcl-2 expression, also clears CLL cells from splenic engraftment sites is highly encouraging.

SPC2996 is currently in international human Phase I/II studies in CLL. Results of the first clinical study will be presented at the 2007 Annual Meeting of the American Society of Clinical Oncology, June 1-5.

For further information, please contact:
Dr. Keith McCullagh
President & CEO, Santaris Pharma,
Tel: +45 4517 9819, Cell:+44 7939 573548, km@santaris.com

Notes to editors

Chronic Lymphocytic Leukaemia

Chronic lymphocytic leukaemia (CLL) is the most common form of leukaemia in adults in western Europe and North America, new cases occurring at an annual incidence of 3 to 5 per 100,000 persons in the population. The condition occurs primarily in older people with a median age at diagnosis of 66 years. Men are twice as likely as women to develop the disease. The clinical course of the condition varies widely with some patients showing rapid disease progression and early death, despite intensive chemotherapy, and others surviving for decades without any treatment. CLL is characterised by excessive numbers of functionally incompetent long-lived B-lymphocytes (small white blood cells) circulating in the blood, sometimes also causing swelling of lymph nodes, spleen and other organs. The failure of these cancerous B-CLL cells to die is generally thought to be due at least in part to over expression of the Bcl-2 gene characteristic of the disease.

About Bcl-2
The protein Bcl-2, first identified in B-cell lymphoma/leukaemia cells from which its name derives, is one of a family of intracellular proteins regulating cell survival and cell death. Some types of cells in the body, for example blood cells, are programmed to die after a few weeks of life, in the case of blood cells to be replaced in the circulation by fresh cells produced in the bone marrow. This process of programmed cell death is known as apoptosis. Bcl-2 is an apoptosis suppressor protein, i.e. it extends the lifespan of the cell in the presence of normal apoptosis stimuli. The levels of Bcl-2 within the cell are frequently over-expressed in malignant cancers, and this is particularly the case in human chronic lymphocytic leukaemia and lymphoma where it acts to prolong the life of malignant white blood cells. Drugs which lower the concentration of Bcl-2 or inhibit its function may therefore have therapeutic benefit by inducing cancer cell death and removal without resorting to chemotherapy.

About SPC2966
SPC2996 is the first of a portfolio of novel experimental drugs blocking harmful gene expression being designed and developed by Santaris Pharma. The drug belongs to a new class of drugs called RNA Antagonists, proprietary to Santaris Pharma, based on the novel three-dimensional analogue of RNA known as Locked Nucleic Acid (LNA). The drug binds with high potency and specificity to the messenger RNA for Bcl-2 and destroys it within the cell, resulting in a reduction in Bcl-2 protein concentration. SPC2996 is an investigational product which has not yet been approved by any regulatory agency as effective or safe for patient use but the novel agent is currently being evaluated in international Phase I/II studies in human CLL in centres in Denmark, France, UK and the USA.

AACR Abstract
An Abstract of the work described in this release can be found on the American Association for Cancer Research (AACR) 2007 Annual Meeting database at the following location:

About Santaris Pharma
Santaris Pharma is a clinical-stage biopharmaceutical company focused on developing a new class of RNAi drugs intended to switch off the expression of harmful genes. Called RNA Antagonists, these new drugs are being developed by Santaris and its corporate partners for the treatment of cancer and metabolic disorders. Created in May 2003 and backed by a broad group of leading international life science venture capital investors, Santaris Pharma completed a Euro 40m second round of equity financing in May 2006. In July 2006, the Company entered into a global partnership with Enzon Pharmaceuticals of New Jersey to co-develop and commercialise a series of Santaris RNA Antagonists for improving the treatment of cancer.

Santaris Pharma’s RNA Antagonist drug pipeline is based on its unique Locked Nucleic Acid (LNA) technology. LNA drugs, with their high potency and biostability, have the potential to transform the field of RNAi medicines, making specific and effective gene silencing a reality in

human medicine. If this potential is realised, even in part, it may be possible to design new drugs to treat the underlying genetic causes of disease rather than just the physical symptoms. Santaris Pharma holds the world wide patent rights to the exploitation of LNA in pharmaceuticals and presently has three drugs in preclinical or clinical development. The lead drug candidate, SPC2996, is currently undergoing international, multicenter, phase I/II clinical studies in Chronic Lymphocytic Leukaemia.

For further company information see

www.santaris.com

Forward Looking Statements
There are forward-looking statements contained herein, which can be identified by the use of forward-looking terminology such as the words "believes," "expects," "may," "will," "should", "potential," "anticipates," "plans" or "intends" and similar expressions. Such forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause actual results, events or developments to be materially different from the future results, events or developments indicated in such forward-looking statements. Such factors include, but are not limited to the timing, success and cost of clinical studies; the ability to obtain regulatory approval of products, market acceptance of and future demand for Santaris products and the impact of competitive products and pricing. These factors should be considered carefully and readers are cautioned not to place undue reliance on such forward-looking statements. No assurance can be given that the future results covered by the forward-looking statements will be achieved. All information in this press release is as of the date of this press release and Santaris does not intend to update this information.