Imclone Systems Commences Patient Treatment in U.S. Phase I Clinical Trial of IMC-3G3.

NEW YORK -- ImClone Systems Incorporated (NASDAQ: IMCL) today announced the commencement of patient treatment in a Phase I clinical trial of its fully human IgG1 monoclonal antibody targeting the platelet derived growth factor receptor alpha (PDGFR[eth]), IMC-3G3, in patients with solid tumors.

This study will be conducted at two clinical sites in the U.S., and is designed to establish the safety profile of IMC-3G3 and to evaluate the pharmacokinetics and pharmacodynamics of the new antibody administered weekly by intravenous infusion. The trial is expected to enroll approximately 30 to 40 patients.

"Platelet-derived growth factor is among the most important growth factors known to regulate cell growth and division," stated Eric K. Rowinsky, Chief Medical Officer and SVP of ImClone Systems. "One of the receptors for PDGF, PDGFR[eth], is expressed on a number of human cancers and on accessory cells in tumors that are important for sustaining tumor growth. Recent experimental evidence has shown that PDGFR[eth] plays an important role in regulating VEGF-driven tumor angiogenesis. Therapeutic intervention with a PDGFR[eth] antibody, such as IMC-3G3, may provide another means to blocking tumor growth and angiogenesis in human cancers, and possibly an approach to overcome resistance to current VEGF-targeted therapies.

IMC-3G3 is a fully human IgG1 monoclonal antibody that is designed to bind to PDGFR[eth], leading to inhibition of ligand-dependent signaling in PDGFR[eth]-expressing tumor cells, as well as stromal cells in the tumor microenviroment that are dependent on PDGFR[eth] signaling. Treatment with IMC-3G3 in preclinical models of human breast, hepatocellular, ovarian and prostate carcinoma has resulted in significant reduction of cancer cell proliferation and tumor growth.

About ImClone Systems Incorporated

ImClone Systems Incorporated is committed to advancing oncology care by developing and commercializing a portfolio of targeted biologic treatments designed to address the medical needs of patients with a variety of cancers. The Company's research and development programs include growth factor blockers and angiogenesis inhibitors. ImClone Systems' strategy is to become a fully integrated biopharmaceutical company, taking its development programs from the research stage to the market. ImClone Systems' headquarters and research operations are located in New York City, with additional administration and manufacturing facilities in Branchburg, New Jersey.

Certain matters discussed in this news release may constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 and the Federal securities laws. Although the company believes that the expectations reflected in such forward-looking statements are based upon reasonable assumptions it can give no assurance that its expectations will be achieved. Forward-looking information is subject to certain risks, trends and uncertainties that could cause actual results to differ materially from those projected. Many of these factors are beyond the company's ability to control or predict. Important factors that may cause actual results to differ materially and could impact the company and the statements contained in this news release can be found in the company's filings with the Securities and Exchange Commission including quarterly reports on Form 10-Q, current reports on Form 8-K and annual reports on Form 10-K. For forward-looking statements in this news release, the company claims the protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995. The company assumes no obligation to update or supplement any forward-looking statements whether as a result of new information, future events or otherwise.