HuMax-CD20 Binds to Site Not Recognized By Other CD20 Antibodies

Copenhagen, Denmark; December 8, 2003 – Genmab A/S (CSE: GEN) announced today that HuMax-CD20 binds to a unique site on CD20 target cells when compared to other known CD20 antibodies.  This is a distinguishing characteristic of HuMax-CD20 and may help explain why HuMax-CD20 has outperformed other CD20 antibodies in a variety of pre-clinical studies. Furthermore, in a novel cancer disease model in immuno-compromised mice using sensitive bioluminescence imaging, new data show that HuMax-CD20 appears to stop growth of B-cell tumors grown from a laboratory cell line far more effectively than either placebo, or a marketed treatment, rituximab. 

Dr. Jan van de Winkel, Chief Scientific Officer of Genmab, presented this new pre-clinical data on HuMax-CD20 today at the 45th Annual Meeting of the American Society of Hematology in San Diego, California.

“We have observed the unusually good performance of HuMax-CD20 in a large number of pre-clinical tests, and have been conducting research to help explain why the antibody binds to and kills the disease target cells so effectively,” said Lisa N. Drakeman, Ph.D., Chief Executive Officer of Genmab. “We are excited by the discovery that HuMax-CD20 uses a unique site to attach to disease cells. We are also pleased to add to the growing body of positive pre-clinical data for this antibody.”

Conference call

Genmab’s Management will discuss the news on the already planned conference call today, December 8, 2003 at:

4:00 pm CET

3:00 pm BST

10:00 am US Eastern Time

The dial in numbers are as follows:

+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 the Animal Disease Model

HuMax-CD20 was evaluated in a mouse model in which disseminated outgrowth of human B-cell tumor cells is followed using optical imaging. Tumors were induced by inoculating Daudi cells, a CD20-expressing human lymphoma cell line, which readily grows in immuno deficient (SCID) mice. For this model Daudi cells were transfected with luciferase which makes them bioluminescent after administration of luciferin, thus permitting detection using a sensitive camera. This technique is suitable for establishing growth curves of small tumor metastases in mice. In this model we compared the therapeutic efficacy of different CD20 antibodies, given as a single low dose in an early stage of tumor development (8 days after inoculation).

About HuMax-CD20

HuMax-CD20 is a human antibody which is effective at binding to the disease target, and releases only very slowly from the target over time. In February 2003, Genmab presented data from pre-clinical laboratory tests showing HuMax-CD20 appeared to kill tumor cells that were resistant to rituximab, a marketed cancer therapy. The data showed the antibody  highly effective in inducing complement mediated cytotoxicity (cell destruction) of B-cell tumors. Subsequently, Genmab has collected data that appears to show HuMax-CD20 is also effective in inducing Natural Killer cell-mediated cytotoxicity of B-cell tumors.  Further, in a 92 day primate study, HuMax-CD20 effectively depleted B-cells from blood and lymph nodes.  In this study, HuMax-CD20 appeared to deplete B-cells for a period of time that was four times longer than rituximab.

About CD20

The CD20 antigen is a transmembrane protein on pre-B and mature B lymphocytes. CD20 appears to act as a calcium ion channel, and to regulate early steps in B lymphocyte activation. The molecule is not shed from the cell surface, and is not internalized upon antibody binding. CD20 is found on over 90% of B-cell lymphomas, as well as other lymphoid tumors of B-cell origin.