Xanthus Pharmaceuticals, Inc., a privately-held oncology and autoimmune disease drug development company, announced that its New Drug Application (NDA) for fludarabine phosphate oral tablets (oral fludarabine) was accepted for filing by the U.S. Food and Drug Administration (FDA) for the treatment of relapsed B-cell chronic lymphocytic leukemia (CLL). Filing of the NDA indicates that the registration package is sufficiently complete to allow for a thorough review of the data supporting the safety profile and effectiveness of oral fludarabine. Earlier this month Xanthus announced that the FDA granted Orphan Drug Designation for oral fludarabine for B-cell CLL. Xanthus licensed the exclusive right to develop and commercialize oral fludarabine in the United States from Schering AG (now Bayer Schering Pharma AG) in October of 2006.

"Currently patients with chronic CLL undergoing fludarabine treatment in the United States receive the drug intravenously. Acceptance of the NDA application is a critical next step in our effort to provide these individuals with a more patient-friendly delivery option," said Richard Dean, Ph.D., CEO of Xanthus. "With the convenience of oral dosing and a strong body of clinical efficacy and tolerability data already behind it, we believe oral fludarabine represents an exciting opportunity for Xanthus."

About CLL and Oral Fludarabine

Chronic lymphocytic leukemia (CLL) is a cancer of the white blood cells and bone marrow which arises predominantly in older age groups. CLL is the most prevalent leukemia and according to the American Cancer Society, approximately 15,300 new CLL cases were diagnosed in the United States in 2007. Oral fludarabine is currently marketed by Bayer Schering Pharma AG in the European Union and Canada for the treatment of relapsed B-cell chronic lymphocytic leukemia. Intravenous (IV) fludarabine has been widely available for a number of years in the United States and other countries as a treatment for patients with CLL. The approval for the oral formulation was extended to first-line treatment in Europe in November 2004. Bayer Schering Pharma AG studied oral fludarabine in several clinical trials as a first- and second-line therapy, where it exhibited an efficacy and tolerability profile similar to that of the IV formulation.

About Xanthus Pharmaceuticals, Inc.

Xanthus Pharmaceuticals, Inc. is developing a portfolio of novel, clinical-stage, small-molecule oncology candidates through a management team whose accomplished track record encompasses all aspects of drug development, from discovery through regulatory approval and commercialization. The Company is applying its expertise both to advance its current pipeline and expand it into indications of unmet medical need beyond oncology.

Xanthus is headquartered in Cambridge, Massachusetts with an additional facility in Montreal, Quebec. More information is available at xanthus.

This press release contains forward-looking statements concerning Xanthus that involve a number of risks and uncertainties. For this purpose, any statements contained herein that are not statements of historical fact may be deemed to be forward-looking statements. Without limiting the foregoing, the words, "believes," "anticipates," "plans," "expects," "estimates," "intends," "should," "could," "will," "may," and similar expressions are intended to identify forward-looking statements. There are a number of important factors that could cause Xanthus' actual results to differ materially from those indicated by such forward-looking statements, including risks as to whether results obtained in early clinical studies or in preclinical studies will be indicative of results obtained in future clinical trials or warrant additional trials; whether products based on Xanthus' technology will advance through the clinical trial process and receive approval from the United States Food and Drug Administration or equivalent foreign regulatory agencies; whether the company will have the cash resources to develop and commercialize its products; and whether the patent and patent applications owned or licensed by Xanthus will protect the Company's technology and prevent others from infringing it. Xanthus disclaims any intention or obligation to update any forward-looking statements.

Xanthus Pharmaceuticals