ImClone Systems Announces Complete Enrollment of Several Studies Examining Potential Survival Benefit Of ERBITUX(R) In Three Major Cancer Types.

NEW YORK -- ImClone Systems Incorporated (NASDAQ: IMCL) today announced that full patient enrollment has been completed in three international, registrational Phase III clinical trials examining the use of ERBITUX(R) (cetuximab) in three major cancer types. The first of these studies, known as EPIC, examines the use of ERBITUX in metastatic colorectal cancer after failure of oxaliplatin-based chemotherapy. The second, EXTREME, sponsored by Merck KGaA, examines ERBITUX as a first-line treatment for patients with recurrent and/or metastatic squamous cell carcinoma of the head and neck. The third study, FLEX, also sponsored by Merck KGaA, explores the first-line use of ERBITUX in advanced non-small cell lung cancer. A combined total of more than 2,800 patients have been enrolled in these studies.

Colorectal Cancer

The EPIC study is being conducted to determine whether survival is prolonged in patients with metastatic colorectal cancer treated with ERBITUX in combination with irinotecan compared with irinotecan alone, after best available first-line chemotherapy has failed. The 1,300 patients enrolled in this study, which began enrollment in June 2003, were recruited from 250 centers worldwide. The study is being conducted jointly by Bristol-Myers Squibb, ImClone Systems and Merck KGaA.

EPIC is the third Phase III study of ERBITUX in metastatic colorectal cancer to complete accrual. Last year, Merck KGaA announced that it completed recruitment of 1,212 patients in a study known as CRYSTAL, examining first-line use of ERBITUX in combination with FOLFIRI (5-FU and FA plus irinotecan). The third study, a randomized Phase III study of best supportive care plus or minus ERBITUX in patients with metastatic colorectal cancer refractory to oxaliplatin, irinotecan, and 5-FU, also completed enrollment of 572 patients last year. This study seeks to determine if ERBITUX prolongs overall survival in these drug-refractory patients. Recruitment is ongoing in several other Phase III registrational studies of ERBITUX combined with various chemotherapies and/or biologic therapies in the treatment of colorectal cancer patients in the adjuvant, first-line, and second-line settings.

Head and Neck Cancer

The EXTREME study has enrolled 442 patients with recurrent and/or metastatic head and neck cancer who were randomized to receive cisplatin/carboplatin plus 5-FU with or without ERBITUX. The primary endpoint of the study is survival. The study started in December 2004 and is being conducted in 89 centers across Europe. Recruitment was completed ahead of schedule.

Lung Cancer

The FLEX study has recruited 1,124 patients with stage IIIb/IV lung cancer who had not received previous chemotherapy. Patients have been recruited from 173 centers worldwide and were randomized to receive either ERBITUX in combination with standard first-line chemotherapy or standard chemotherapy alone. The primary endpoint is survival. Enrollment started in November 2004. This study is the first among several first- and second-line, registrational studies of ERBITUX in lung cancer to complete enrollment.

"The full enrollment of these studies in three major tumor types is indicative of the breadth of the global ERBITUX clinical development program," said Eric K. Rowinsky, M.D., Chief Medical Officer of ImClone Systems. "The success of an oncology product is ultimately dictated by the quality of its data. The ERBITUX clinical development plan, of which these studies are the foundation, seeks to conclusively answer key questions about the drug's ability to prolong survival in a variety of settings and tumor types."

About ERBITUX(R) (Cetuximab)

On February 12, 2004, the FDA approved ERBITUX for use in the United States in combination with irinotecan in the treatment of patients with EGFR-expressing, metastatic colorectal cancer who are refractory to irinotecan-based chemotherapy and for use as a single agent in the treatment of patients with EGFR-expressing, metastatic colorectal cancer who are intolerant to irinotecan-based chemotherapy. The effectiveness of ERBITUX for the treatment of colorectal cancer is based on objective response rates. Currently, no data are available that demonstrate an improvement in disease-related symptoms or increased survival with ERBITUX in metastatic colorectal cancer patients.

ERBITUX binds specifically to the epidermal growth factor receptor (EGFR, HER1, c-ErbB-1) on both normal and tumor cells, and competitively inhibits the binding of epidermal growth factor (EGF) and other ligands, such as transforming growth factor-alpha. The EGFR is constitutively expressed in many normal epithelial tissues, including the skin and hair follicle. Over-expression of EGFR is also detected in many human cancers including those of the colon and rectum.

Important Safety Information

Severe infusion reactions, rarely fatal and characterized by rapid onset of airway obstruction (bronchospasm, stridor, hoarseness), urticaria, and hypotension, have occurred in approximately 3% (20/774) of patients with the administration of ERBITUX. Most reactions (90%) were associated with the first infusion of ERBITUX despite the use of prophylactic antihistamines. Severe infusion reactions require immediate and permanent discontinuation of ERBITUX therapy. Caution must be exercised with every ERBITUX infusion as there were patients who experienced their first severe infusion reaction during later infusions. A 1-hour observation period is recommended following the ERBITUX infusion. Longer observation periods may be required in patients who experience infusion reactions.

Severe cases of interstitial lung disease (ILD), which was fatal in one case, occurred in less than 0.5% of 774 patients receiving ERBITUX.

Dermatologic toxicities, including acneform rash (11% of 774 patients, grade 3/4), skin drying and fissuring, inflammatory or infectious sequelae (e.g., blepharitis, cheilitis, cellulitis, cyst) and paronychial inflammation (0.4% of 774 patients, grade 3) were reported. Sun exposure may exacerbate any skin reactions.

Hypomagnesemia has been reported with ERBITUX when administered as a single agent and in combination with multiple different chemotherapeutic regimens. The incidence of hypomagnesemia (both overall and severe (NCI CTC grades 3 & 4)) was increased in patients receiving ERBITUX alone or in combination with chemotherapy as compared to those receiving best supportive care or chemotherapy alone based on ongoing, controlled clinical trials in 244 patients. Approximately one-half of these patients receiving ERBITUX experienced hypomagnesemia and 10-15% experienced severe hypomagnesemia. Electrolyte repletion was necessary in some patients, and in severe cases, intravenous replacement was required. Patients receiving ERBITUX therapy should be periodically monitored for hypomagnesemia, and accompanying hypocalcemia and hypokalemia during, and up to 8 weeks following the completion of, ERBITUX therapy.

Other serious adverse events associated with ERBITUX in clinical trials (n=774) were fever (5%), sepsis (3%), kidney failure (2%), pulmonary embolus (1%), dehydration (5% in patients receiving ERBITUX plus irinotecan, 2% receiving ERBITUX as a single agent) and diarrhea (6% in patients receiving ERBITUX plus irinotecan, 0.2% with ERBITUX as a single agent).

Additional common adverse events seen in patients receiving ERBITUX plus irinotecan (n=354) or ERBITUX as a single agent (n=420) were acneform rash (88%/90%), asthenia/malaise (73%/48%), diarrhea (72%/25%), nausea (55%/29%), abdominal pain (45%/26%), vomiting (41%/25%), fever (34%/27%), constipation (30%/26%) and headache (14%/26%).

Full prescribing information, including boxed WARNING regarding infusion reactions, is available upon request or by visiting www.ERBITUX.com.

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.