ILEX Announces CAMPATH Front-Line CLL Study Fully Enrolled; Trial Will Evaluate Prolonged Survival in Previously Untreated Patients.

SAN ANTONIO -- ILEX(TM) Oncology, Inc. (Nasdaq:ILXO) announced today that it has met the enrollment target of 284 patients for its randomized Phase III study to evaluate the efficacy of CAMPATH(R) (alemtuzumab) versus chlorambucil as front-line therapy in previously untreated patients with progressive B-cell chronic lymphocytic leukemia (B-CLL). CAMPATH was granted accelerated approval by the U.S. Food and Drug Administration (FDA) in May 2001.

"The acceleration in enrollment that we've seen over the past year underscores the need for additional front-line therapies for B-CLL patients," said ILEX CEO and President Jeff Buchalter. "We're pleased with the momentum we've been able to achieve in this trial, and we're looking forward to the presentation of additional safety and efficacy data at the American Society of Hematology annual meeting in December."

An interim safety update from this trial was recently presented by clinical investigators at the 2004 American Society of Clinical Oncology annual meeting. The data showed that the safety profiles of CAMPATH and chlorambucil were comparable in 174 patients on the trial. An independent data safety monitoring board recommended that the study continue.

CAMPATH is a humanized monoclonal antibody that binds to a specific target, CD52, on cell surfaces, leading the body's immune system to destroy malignant cells and deplete B- and T-cells that are instrumental in disease. CAMPATH is presently indicated for patients with B-cell chronic lymphocytic leukemia (B-CLL) who have been treated with alkylating agents and have failed fludarabine treatment.

The most commonly reported infusion-related adverse events were rigors, fever, nausea, vomiting, and hypotension. Hematologic toxicities included pancytopenia/marrow hypoplasia, anemia, thrombocytopenia, and neutropenia and should be monitored. Infections reported included sepsis, pneumonia, and opportunistic infections such as CMV, candidiasis, aspergillosis, and mucormycosis. CAMPATH is contraindicated in patients with active systemic infections, underlying immunodeficiency, or known Type 1 hypersensitivity or anaphylactic reactions to CAMPATH or any of its components.

Schering AG, Germany (FSE:SCH) (NYSE:SHR) holds exclusive worldwide marketing and distribution rights to CAMPATH. The product is marketed in the U.S. by Berlex Inc., a U.S. affiliate of the Schering AG Group. CAMPATH was launched in the U.S. in June 2001, and in Europe, where it is named MABCAMPATH, in August 2001.

About ILEX

Founded in 1994 as an oncology drug development company, ILEX has a marketed product, CAMPATH(R) in the United States and MABCAMPATH(R) in the European Union, and is advancing an innovative and diversified pipeline of compounds focused on the treatment of cancer. The ILEX pipeline comprises product candidates at various stages of clinical development, including monoclonal antibodies, novel cytotoxic agents, angiogenesis inhibitors and signal transduction inhibitors. Based in San Antonio, Texas, ILEX maintains a core competency in oncology drug development. ILEX also conducts research in angiogenesis inhibition, cell signaling, medicinal chemistry and nuclear receptor biology at its laboratories in Boston, Mass., and Geneva, Switzerland. In February 2004, ILEX announced its agreement to merge with Genzyme Corporation, a global biotechnology company. The merger, subject to ILEX stockholder approval and other customary conditions, is expected to close in mid-2004. Further information about ILEX can be found on the company's Web site at www.ilexonc.com.

Certain statements contained herein are "forward-looking" statements (as such term is defined in the Private Securities Litigation Reform Act of 1995). Because these statements include risks and uncertainties, actual results may differ materially from those expressed or implied by such forward-looking statements. Specifically, factors that could cause actual results to differ materially from those expressed or implied by such forward-looking statements include, but are not limited to: risks associated with preclinical and clinical developments in the biopharmaceutical industry in general and in ILEX's compounds under development in particular; market acceptance of CAMPATH(R); the ability to expand the number and scope of the indications for which CAMPATH(R) is approved; the potential failure of ILEX's compounds under development to prove safe and effective for treatment of disease; uncertainties inherent in the early stage of ILEX's compounds under development; failure to successfully implement or complete clinical trials; failure to receive marketing clearance from regulatory agencies for our compounds under development; acquisitions, divestitures, mergers, licenses or strategic initiatives that change ILEX's business, structure or projections; the ability of ILEX to predict its future expenses and capital needs; the development of competing products; uncertainties related to ILEX's dependence on third parties and partners; and those risks described in ILEX's report on Form 10-K filed on March 12, 2004, and in other filings made by ILEX with the SEC. ILEX disclaims any obligation to update these forward-looking statements.