DIATOS AND MEDAREX SIGN CANCER PRODUCT LICENSING AGREEMENT.

Diatos SA, a Paris-based privately held biopharmaceutical company, and Medarex, Inc. (Nasdaq: MEDX) have announced that Diatos has licensed from Medarex the exclusive European rights to develop and commercialize Super-Leu-Dox, a potential new cancer treatment.

Under the terms of the agreement, Diatos expects to develop and commercialize Super-Leu-Dox, which is currently in late pre-clinical development, in Europe. In return, Medarex has an option, exercisable before Super-Leu-Dox reaches Phase III development, to co-develop and co-commercialize the product with Diatos in Europe. If Medarex exercises its option, the parties will share equally all development and commercialization costs and future potential revenues from sales and sublicensing of Super-Leu-Dox in Europe. If Medarex elects not to co-develop and co-commercialize the product in Europe, Diatos will have the right to develop and commercialize Super-Leu-Dox in Europe and will be responsible for all development activities and costs. In that event, Medarex will receive royalties on any commercial sales of the product. Under the terms of the agreement, Medarex retains all rights to Super-Leu-Dox in non-European countries. Each party has the right to use pre-clinical and clinical data generated by the other party for developing Super-Leu-Dox in their respective territories.

"Obtaining the European development and commercialization rights to Super-Leu-Dox is a significant step for Diatos, demonstrating our commitment to building a pipeline of cancer therapeutic products, and positions Diatos as a key player in the emerging field of prodrug-based therapeutics," said Dr. John Tchelingerian, president and CEO of Diatos. "...We are pursuing the discovery and development of high value proprietary therapeutic products through the use of our TSP and DPV core technologies."

"We are impressed with Diatos's commitment to develop prodrug-based therapeutic products and believe that Diatos has the development capabilities to lead a successful Super-Leu-Dox development program," said Dr. Donald L. Drakeman, president and CEO of Medarex.

About Super-Leu-Dox

Medarex received its rights to Super-Leu-Dox (CPI-0004) through the acquisition of Corixa Corporation's Tumor Activated Prodrug (TAP) program. Super-Leu-Dox consists of doxorubicin (a marketed cytotoxic compound used in treating cancer) conjugated to a proprietary prodrug peptide. Super-Leu-Dox incorporates the TAP technology, comprising a four-amino acid peptide conjugated to a cytotoxic agent whose activity is inhibited when it is conjugated to the peptide. Preclinical studies have indicated that when prodrug molecules reach the vicinity of a tumor, the peptide is cleaved off by endopeptidase enzymes that are released by the cancer cells, freeing the cytotoxic compound. The unconjugated compound then acts as an anti-cancer agent, exerting its cytotoxic effects locally on the cancer cells. The ability to selectively deliver anti-cancer agents, such as doxorubicin, in this manner is expected to result in better clinical outcomes both in terms of improved response rates and lower toxicity.

The structure and tumor-selectivity of Super-Leu-Dox is based on a tumor-activated prodrug approach that is similar in concept to Diatos's TSP technology platform. Both Super-Leu-Dox and the TSP technology were co-invented by Prof. Trouet of the University Catholique de Louvain in Louvain-la- Neuve, Belgium. Trouet has served as the acting chief scientific officer of Diatos for the past year and is currently a scientific advisor and a member of Diatos's scientific advisory board.

About Prodrugs

Prodrugs may improve the properties of drug therapies by increasing their efficacy, optimizing their dosage, and reducing adverse effects. Prodrugs have the potential to offer a significant benefit to the treatment of cancer because the administration of therapeutic agents is often associated with significant toxicity and lack of tumor selectivity. Diatos believes that its tumor-targeting and intracellular drug delivery technologies will enable it to build an attractive portfolio of highly effective anti-cancer therapeutics.

About Diatos

Diatos is a privately held biopharmaceutical company that uses its proprietary drug-targeting and intracellular-delivery technologies to develop innovative therapies for cancer and other serious diseases. Diatos has two core technology platforms:

* Diatos Peptide Vector (DPV) technology enables or significantly enhances selective cellular or nuclear uptake of a broad range of therapeutic compounds, including small molecules, peptides and proteins, antibodies and antibody fragments, oligonucleotides, and nanospheres.

* Tumor Selective Prodrug (TSP) technology enables the release of anti-cancer agents selectively at the sites of tumor cells.

In addition to using these technologies to develop its own product pipeline, Diatos is offering these technologies to pharmaceutical and biotechnology companies, under licensing or partnering relationships, for the development of a broad range of therapeutic products in various therapeutic fields and also for target validation and drug screening.

Founded in 1999 (a spin-off from Institut Pasteur), Diatos has raised to date 23.5 million Euros. Diatos has a total of 40 employees at its headquarters in Paris, France, and at the campus of Louvain-la-Neuve University in Louvain, Belgium.

For more information, visit http://www.diatos.com.

About Medarex

Medarex is a biopharmaceutical company focused on the discovery and development of therapeutics to treat life-threatening and debilitating diseases. Medarex's UltiMAb Human Antibody Development SystemSM is a unique combination of human antibody technologies that Medarex believes enables the rapid creation and development of fully human antibodies for a wide range of potential disease targets for therapeutic antibody products, including products for the treatment of cancer, inflammation, autoimmune and infectious diseases. Medarex's product pipeline is based on a variety of therapeutic antibody products developed through the use of its UltiMAb(tm) technology. Medarex creates and develops fully human antibodies for itself and others, offering a full range of antibody related capabilities, including pre-clinical and clinical development supported by cGMP manufacturing services.

For more information, visit http://www.medarex.com.