Exhibit 99.1

ImClone Systems Incorporated

Investors and Media Contact:

Tracy Henrikson

(908) 243-9945

MEDIA@IMCLONE.COM

FOR IMMEDIATE RELEASE

FDA APPROVES IMCLONE SYSTEMS’ NEW STATE-OF-THE-ART
MANUFACTURING FACILITY

—“BB50” Facility to Serve as Second Manufacturing Source for ERBITUX® —

NEW YORK, NY—August 20, 2007—ImClone Systems Incorporated (NASDAQ: IMCL), a leader in the development and commercialization of novel cancer therapeutics, today announced that it has received approval from the Food and Drug Administration for a second facility to manufacture ERBITUX®.  The approval to manufacture ERBITUX in this new 250,000-square-foot multi-suite manufacturing facility, referred to as “BB50”, more than doubles ImClone’s total available production volume capacity for ERBITUX.  This approval, in conjunction with ImClone’s existing “BB36” manufacturing facility, enhances the Company’s ability to meet increasing demand for ERBITUX in the worldwide market.

“The FDA approval of BB50 represents the culmination of ImClone’s efforts over the last several years to establish this state-of-the-art facility.  This now provides us with a great deal of strategic and operational flexibility in pursuing additional commercial opportunities going forward,” said Richard P. Crowley, Senior Vice President, Biopharmaceutical Operations of ImClone Systems.  “Together, our two manufacturing facilities provide us with the capacity to produce ERBITUX and future products for worldwide development and commercialization, and serve to support our initiatives for the long-term growth and success of ImClone.”

Construction of BB50 was completed in the fourth quarter of 2005.  This facility is designed to contain three distinct suites with a total future production volume capacity of up to 110,000 liters.  The commissioning and initial validation of one of the suites was completed during the second quarter of 2006 and the Company began producing ERBITUX in this suite in June 2006.  The other two suites at this facility will enable

ImClone in the future to produce ERBITUX, additional ImClone products, or third-party products under contract manufacturing agreements.  Both BB50 and BB36 are located on ImClone’s Branchburg, N.J. campus.

About ERBITUX® (Cetuximab)

ERBITUX is a monoclonal antibody (IgG1 Mab) designed to inhibit the function of a molecular structure expressed on the surface of normal and tumor cells called the epidermal growth factor receptor (EGFR, HER1, c-ErbB-1). In vitro assays and in vivo animal studies have shown that binding of ERBITUX to the EGFR blocks phosphorylation and activation of receptor-associated kinases, resulting in inhibition of cell growth, induction of apoptosis, and decreased matrix metalloproteinase and vascular endothelial growth factor production. In vitro, ERBITUX can mediate antibody-dependent cellular cytotoxicity (ADCC) against certain human tumor types. While the mechanism of ERBITUX’s anti-tumor effect(s) in vivo is unknown, all of these processes may contribute to the overall therapeutic effect of ERBITUX. EGFR is part of a signaling pathway that is linked to the growth and development of many human cancers, including those of the head and neck, colon and rectum.

ERBITUX (Cetuximab), in combination with radiation therapy, is indicated for the treatment of locally or regionally advanced squamous cell carcinoma of the head and neck. ERBITUX as a single agent is indicated for the treatment of patients with recurrent or metastatic squamous cell carcinoma of the head and neck for whom prior platinum-based therapy has failed.

ERBITUX is indicated for the treatment of EGFR-expressing, metastatic colorectal carcinoma (mCRC) in combination with irinotecan for patients who are refractory to irinotecan-based chemotherapy, and as a single agent for patients who are intolerant to irinotecan-based therapy. The effectiveness of ERBITUX for the treatment of EGFR-expressing mCRC cancer is based on objective response rates.

For full prescribing information, including boxed WARNINGS regarding infusion reactions and cardiopulmonary arrest, visit http://www.ERBITUX.com.

Important Safety Information

Grade 3/4 infusion reactions, rarely with fatal outcome (less than 1 in 1000), occurred in approximately 3% (46/1485) of patients receiving ERBITUX (Cetuximab) therapy. These reactions are characterized by rapid onset of airway obstruction (bronchospasm, stridor, hoarseness), urticaria, hypotension, loss of consciousness, and/or cardiac arrest. Severe infusion reactions require immediate and permanent discontinuation of ERBITUX therapy.

Most reactions (90%) were associated with the first infusion of ERBITUX despite the use of prophylactic antihistamines. 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.

Cardiopulmonary arrest and/or sudden death occurred in 2% (4/208) of patients with squamous cell carcinoma of the head and neck treated with radiation therapy and ERBITUX as compared to none of 212 patients treated with radiation therapy alone. Fatal events occurred within 1 to 43 days after the last ERBITUX treatment. ERBITUX in combination with radiation therapy should be used with caution in patients with known coronary artery disease, congestive heart failure and arrhythmias. Close monitoring of serum electrolytes, including serum magnesium, potassium, and calcium during and after ERBITUX therapy is recommended.

Severe cases of interstitial lung disease (ILD), which was fatal in one case, occurred in less than 0.5% of 774 patients with advanced colorectal cancer (mCRC) receiving ERBITUX. There was one case of ILD reported in 796 patients with head and neck cancer receiving ERBITUX in clinical studies.

In clinical studies of ERBITUX, dermatologic toxicities, including acneform rash, skin drying and fissuring, inflammatory and infectious sequelae (eg, blepharitis, cheilitis, cellulitis, cyst), and hypertrichosis were reported. In 208 patients receiving ERBITUX + RT, acneform rash was reported in 87% (17% severe) as compared to 10% in 212 patients treated with radiation therapy alone (1% severe). In patients receiving ERBITUX alone, 76% (N=103) experienced acneform rash (1% severe). In patients with mCRC, acneform rash was reported in 89% (686/774) of all treated patients, and was severe in 11% (84/774). Subsequent to the development of severe dermatologic toxicities, complications including S. aureus sepsis and abscesses requiring incision and drainage were reported. Sun exposure may exacerbate these effects. A related nail disorder, occurring in 12% (0.4% Grade 3) of patients, was characterized as a paronychial inflammation.

The safety of ERBITUX in combination with radiation therapy and cisplatin has not been established. Death and serious cardiotoxicity were observed in a single-am trial with ERBITUX, delayed, accelerated (concomitant boost) fractionation radiation therapy, and cisplatin (100 mg/m2) conducted in patients with locally advanced squamous cell carcinoma of the head and neck. Two of 21 patients died, one as a result of pneumonia and one of an unknown cause. Four patients discontinued treatment due to adverse events. Two of these discontinuations were due to cardiac events (myocardial infarction in one patient and arrhythmia, diminished cardiac output, and hypotension in the other patient).

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.

The most serious adverse reactions associated with ERBITUX in combination with radiation therapy in 208 patients with head and neck cancer were infusion reaction (3%), cardiopulmonary arrest (2%), dermatologic toxicity (2.5%), mucositis (6%), radiation dermatitis (3%), confusion (2%), and diarrhea (2%).

The most serious adverse reactions associated with ERBITUX in mCRC clinical trials (N=774) were infusion reaction (3%), dermatologic toxicity (1%), interstitial lung disease (0.4%), fever (5%), sepsis (3%), kidney failure (2%), pulmonary embolus (1%), dehydration (5% in patients receiving ERBITUX with irinotecan, 2% in patients receiving ERBITUX as a single agent) and diarrhea (6% in patients receiving ERBITUX with irinotecan, 0.2% in patients receiving ERBITUX as a single agent).

The overall incidence of late radiation toxicities (any grade) was higher with ERBITUX in combination with radiation therapy compared with radiation therapy alone. The following sites were affected: salivary glands (65%/56%), larynx (52%/36%), subcutaneous tissue (49%/45%), mucous membranes (48%/39%), esophagus (44%/35%), skin (42%/33%), brain (11%/9%), lung (11%/8%), spinal cord (4%/3%), and bone (4%/5%) in the ERBITUX and radiation versus radiation alone arms, respectively.

The incidence of Grade 3 or 4 late radiation toxicities were generally similar between the radiation therapy alone and the ERBITUX plus radiation therapy arms.

The most common adverse events seen in patients with carcinomas of the head and neck receiving ERBITUX in combination with radiation therapy (n=208) versus radiation alone (n=212) were mucositis-stomatitis (93%/94%), acneform rash (87%/10%), radiation dermatitis (86%/90%), weight loss (84%/72%), xerostomia (72%/71%), dysphagia (65%/63%), asthenia (56%/49%), nausea (49%/37%), constipation (35%/30%) and vomiting (29%/23%). The most common adverse events seen in patients with carcinomas of the head and neck receiving ERBITUX as a single agent (N=103) were acneform rash (76%), asthenia (45%), pain (28%), fever (27%) and weight loss (27%). The most common adverse events seen in patients with mCRC receiving ERBITUX with 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%).

About ImClone Systems

ImClone Systems Incorporated is a fully integrated biopharmaceutical company 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’ headquarters and research operations are located in New York City, with additional administration and manufacturing facilities in Branchburg, New Jersey.  For more information about ImClone Systems, please visit the Company’s web site at http://www.imclone.com.

ERBITUX is a registered trademark of ImClone Systems Incorporated.

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.

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