Quadramet update

Preclinical data presented at AACR indicate that exposure to radiation from QUADRAMET increases the expression of surface molecules involved in the identification and killing of cancer cells by the immune system

Cytogen Corporation reported results of a preclinical study indicating that exposure to ionizing radiation with QUADRAMET(R) (samarium Sm-153 lexidronam injection) increases the expression of surface molecules on cancer cells, potentially improving the ability of the body's immune system to recognize and kill tumor cells. QUADRAMET is currently marketed for the relief of pain associated with cancer progression to bone in a variety of tumor types. The findings were presented today by researchers from the National Cancer Institute (NCI) at the 97th Annual Meeting of the American Association for Cancer Research (AACR) in Washington, D.C.

"Recent research has provided new insights showing how dying tumor cells, such as those killed by exposure to radiation or chemotherapy, engage with antitumor immune responses," stated Michael D. Becker, president and chief executive officer of Cytogen. "Building on this research, these new preclinical findings presented by researchers at the NCI further support ongoing efforts to investigate therapeutic options that combine QUADRAMET with synergistic agents for the treatment of a wide range of cancer types."

In the study, 10 human tumor cell lines, including four prostate, two breast, and four lung, were treated with increasing doses of QUADRAMET. Ninety-six hours following exposure, fluorescence activated cell sorting (FACS) analysis was performed for five surface molecules. Ten out of 10 tumor cell lines (100%) upregulated Fas (CD95) and carcinoembryonic antigen (CEA), while 70% upregulated MUC-1, 40% upregulated MHC class I and 30% upregulated ICAM-1. In addition, the HLA-A2 prostate cell line, LNCaP, was analyzed to determine whether treatment with QUADRAMET rendered the tumor cells more susceptible to killing by CTLs. This line demonstrated enhanced killing by tumor-specific CTL following exposure to QUADRAMET.

Based on these positive preclinical results, a clinical trial evaluating the effect of combining QUADRAMET with immunotherapy in patients with solid tumors is now in the NCI review process.

"In addition to the direct cytotoxic effects normally associated with ionizing radiation, these data suggest that it also increases the expression of surface molecules on certain cancer cells known to be important in the recognition and destruction of these cells by the body's immune system," said William Goeckeler, Ph.D., senior vice president of operations at Cytogen. "The ability to enhance the anti-cancer effects of various immunotherapy approaches could be of great benefit to patients with many different forms of cancer that have spread to bone."

About QUADRAMET

QUADRAMET is indicated for the relief of pain in patients with confirmed osteoblastic metastatic bone lesions that enhance on radionuclide bone scan. This press release describes clinical applications that differ from that reported in the QUADRAMET package insert.

QUADRAMET is an oncology product indicated for pain relief that pairs the targeting ability of a small molecule, bone-seeking phosphonate (EDTMP) with the therapeutic potential of radiation (samarium Sm-153). Skeletal invasion by prostate, breast, multiple myeloma, and other cancers often creates an imbalance between the normal process of bone destruction and formation. QUADRAMET selectively targets such sites of imbalance, thereby delivering radioactivity to areas of the skeleton that have been invaded by metastatic tumor.

QUADRAMET has demonstrated a range of characteristics that may be advantageous for the treatment of pain arising from metastatic bone disease, including early onset of pain relief (patients may experience pain relief within the first week with maximal relief generally occurring at three to four weeks after injection), predictable and reversible bone marrow toxicity or myelosuppression that tends to return to pretreatment levels after eight weeks, ease of administration, and length of pain relief, lasting an average of four months in responding patients. QUADRAMET is administered as a single intravenous injection, usually on an outpatient basis, and exhibits selective uptake in areas of bone formation with little or no detectable accumulation in soft tissue.

QUADRAMET Safety Profile

QUADRAMET causes bone marrow suppression. In clinical trials, white blood cell counts and platelet counts decreased to a nadir of approximately 40% to 50% of baseline in 123 (95%) patients within 3 to 5 weeks after QUADRAMET, and tended to return to pretreatment levels by 8 weeks. Because of the unknown potential for additive effects on bone marrow, QUADRAMET should not be given concurrently with chemotherapy or external beam radiation therapy unless the clinical benefits outweigh the risks. Blood counts should be monitored weekly for at least 8 weeks, or until recovery of adequate bone marrow function. Non-hematologic adverse events that occurred in 5% or more of patients and greater than placebo were plain flare (7%), diarrhea (6%), infection (7%), spinal cord compression (6.5%), arrhythmias (5%), and hematuria (5%). Patients who receive QUADRAMET should be advised that for several hours following administration, radioactivity will be present in excreted urine. To help protect themselves and others in their environment, precautions need to be taken for 12 hours following administration.

A copy of the full prescribing information for QUADRAMET, including warnings, precautions, adverse events and other safety information, may be obtained in the U.S. from Cytogen Corporation by calling toll-free 800-833- 3533 or by visiting the Web site at http://www.cytogen.com, which is not part of this press release.

About Cytogen Corporation

This press release contains certain "forward-looking" statements within the meaning of the Private Securities Litigation Reform Act of 1995 and Section 21E of the Securities Exchange Act of 1934, as amended. All statements, other than statements of historical facts, included in this press release regarding our strategy, future operations, financial position, future revenues, projected costs, prospects, plans and objectives of management are forward-looking statements. Such forward-looking statements involve a number of risks and uncertainties and investors are cautioned not to put any undue reliance on any forward-looking statement. There are a number of important factors that could cause Cytogen's results to differ materially from those indicated by such forward-looking statements. In particular, Cytogen's business is subject to a number of significant risks, which include, but are not limited to: the risk of obtaining additional capital; the risk of obtaining the necessary regulatory approvals; the risk of whether products result from development activities; the risk of shifts in the regulatory environment affecting sales of Cytogen's products such as third-party payor reimbursement issues; the risk associated with Cytogen's dependence on its partners for development of certain projects, as well as other factors expressed from time to time in Cytogen's periodic filings with the Securities and Exchange Commission (the "SEC"). As a result, this press release should be read in conjunction with Cytogen's periodic filings with the SEC. The forward-looking statements contained herein are made only as of the date of this press release, and Cytogen undertakes no obligation to publicly update such forward-looking statements to reflect subsequent events or circumstances.

Web site: http://www.cytogen.com/