Copenhagen, Denmark; December 16, 2003 – Genmab A/S (CSE: GEN) announced today that it has entered into a research collaboration with the Dutch not-for-profit organization Sanquin Blood Supply Foundation to develop a potential improvement in the treatment for hemophilia patients who are not able to respond adequately to standard therapy with factor VIII.

Hemophiliacs suffer from excessive bleeding because their blood does not clot properly.  They are generally treated with factor VIII that replaces the missing clotting product. However, approximately 38% of patients with hemophilia who have been treated with factor VIII, develop antibodies against it that make the treatment less effective.  This is a serious complication that can be life threatening and risk of death in these patients has been identified as five times greater than in patients who do not develop  antibodies.

Sanquin has discovered a method of preventing these inhibitory antibodies from binding to factor VIII.  This method involves using new antibodies to block the sites where the inhibitory antibodies bind and thus allow factor VIII to continue working.  Under the terms of the agreement, Genmab will support a limited research program at Sanquin to further validate this approach.  The agreement includes an option for Genmab to license Sanquin’s technology on specified terms. This agreement will not affect Genmab’s financial guidance for 2003.

“We are happy to expand our pipeline with this novel approach to treating hemophilia,” said Lisa N. Drakeman, Ph.D., Chief Executive Officer of Genmab. “This agreement underlines our efforts to build a broad based antibody business.”

About the program

Sanquin has identified locations on factor VIII where the inhibitory antibodies bind.  To prevent these antibodies from attaching to factor VIII, researchers cover these locations with antibody fragments to provide a blockade around factor VIII.  Genmab may use the antibodies developed by Sanquin or create novel antibodies from the HuMAb-Mouse® for future product development.

There are an estimated 60,000 hemophilia patients in the US, Europe, Canada, and Japan.  Some patients already have developed inhibitory antibodies and would be candidates for a therapeutic product to maintain factor VIII activity.  Patients receiving blood derived and recombinant factor VIII can develop inhibitory antibodies.  Patients with hemophilia who are treated with factor VIII have approximately a 38% risk of developing inhibitory antibodies against it. Initially, scientists believed that treatment with recombinant factor VIII resulted in a higher frequency of inhibitory antibodies but more recent studies suggest that a similar frequency of inhibitor formation is observed in hemophilia patients receiving either blood derived or recombinant factor VIII. Inhibitor formation may be transient but can also persist for longer periods of time. Clinically, inhibitory antibodies directed against factor VIII result in an increased bleeding tendency that can not be corrected by factor VIII replacement therapy. A treatment that blocks the activity of these antibodies could be used prophylactically for patients who continue to need factor VIII therapy.

Conference Call

Genmab’s Management will hold a conference call to discuss the pipeline expansion news today, December 16, 2003 at

4.00 pm CET

3.00 pm BST

10.00 am US Eastern Time

+1-800-915-4836 (in the US) and ask for the Genmab conference call

+1-973-317-5319 (outside the US) and ask for the Genmab conference call

The conference call will be held in English

About Sanquin Blood Supply Foundation

Sanquin, a Dutch not for profit organisation, comprises the divisions Sanquin Research, Sanquin Plasma Products, Sanquin Diagnostic Services (at the ‘CLB location’ Amsterdam) and four blood banks. The organisation was founded 60 years ago and currently employs 2,800 people.

Sanquin Research is involved in basic and applied scientific research, training and education. The research departments support the Sanquin objectives regarding a safe and sufficient blood supply of the highest quality. Accordingly, Sanquin Research provides a scientific foundation for the products and services of Sanquins divisions and the business units Sanquin Pharmaceutical Services and Sanquin Reagents.

The research department of Plasma Proteins headed by professor Koen Mertens is involved in the collaboration with Genmab for a potential improvement in the treatment for hemophilia patients not responding adequately to standard therapy with factor VIII.

The research of this department addresses a variety of blood plasma proteins, in particular constituents of the coagulation system, the clotting mechanism of the blood. The programme is closely related to the production by Sanquin of pharmaceutical plasma proteins from human plasma. For more information about Sanquin, visit www.sanquin.nl