GenPharm Issued U.S. Patent; Brings Second Patent Suit Against Cell Genesys' Subsidiary, Abgenix.

PALO ALTO, Calif.--(BUSINESS WIRE)--Jan. 8, 1997--The United States Patent and Trademark Office (PTO) issued to GenPharm International, Inc. a further U.S. patent relating to transgenic mouse technology. This patent, U.S. Patent no. 5,591,669, covers transgenic mice whose antibody genes have been inactivated. For example, the patent claims cover disrupted expression of mouse antibody constant regions as well as covering targeted deletion of mouse J segments. These gene inactivations can be used in various types of transgenic mice including those which produce completely human antibodies. The patent has a priority date of December 1988.

"We intend to vigorously protect our patent rights where appropriate," commented Jonathan MacQuitty, Ph.D., Chief Executive Officer of GenPharm. "This patent is part of a strong existing proprietary base for GenPharm. Moreover, we anticipate several other patents on related transgenic animal technology being issued to GenPharm over the coming months."

In addition, GenPharm brought a patent infringement suit under the 5,591,669 patent against Abgenix, Inc., a wholly-owned subsidiary of Cell Genesys, Inc. This is the second patent infringement suit brought by GenPharm against Abgenix. The first patent infringement suit was filed in October, 1996 under U.S. Patents no. 5,545,806 and no. 5,569,825. These patents cover methods for producing human antibodies using transgenic mice as well as claims to such transgenic mice.

GenPharm International, Inc. is a world leader in the development of human monoclonal antibodies from transgenic mice for therapeutic and diagnostic uses.

Background

GenPharm's transgenic mice strain, HuMAb-Mouse, contains key gene sequences from unrearranged human antibody genes, as well as having inactivated mouse antibody genes. The human sequences code for both the human heavy and light chains of human antibodies. The human gene sequences function correctly in the mouse, undergoing rearrangement to provide a wide antibody repertoire similar to that in humans. Most importantly, the human antibodies in the transgenic mice undergo class switching and somatic mutation from low affinity IgM class antibodies to high affinity human IgG class antibodies.

GenPharm has now generated, using its transgenic mouse system, human IgG antibodies with affinities that exceed 10 to the tenth power. Antibodies for commercial therapeutic use need affinities in this range to have clinical utility. In addition, because these antibodies are generated from human sequences, they should avoid the rejection problems that have often afflicted mouse-based antibodies.

Another important feature of GenPharm's HuMAb-Mouse is its ability to generate high affinity human antibodies against human antigens. This allows for the possibility of choosing a high affinity human antibody to control a wide range of inflammatory conditions, autoimmune diseases and cancers. GenPharm has already generated human IgG antibodies to various human antigens, including IgE, CD4 and the cancer antigen CEA.

Because the human sequences in the HuMAb-Mouse can generate high affinity human IgG directly in the mice, it is unnecessary to modify the human antibodies generated any further, either to "humanize" the antibodies or to improve their affinity or specificity. Furthermore, because the antibodies have been matured in vivo, they naturally have the specificity and affinity necessary for proper binding to the target antigen.

CONTACT: GenPharm International

Jonathan MacQuitty, 415/842-6441