Efficacy Results from a Randomized Phase II Study of Patients with Advanced Lung Cancer Support Continued Study of Concurrent Chemotherapy Plus ERBITUX(R) (Cetuximab); Abstract 7015

ImClone Systems Incorporated (NASDAQ: IMCL) todayannounced findings from a Southwest Oncology Group randomized clinicaltrial (SWOG-0342) of ERBITUX(R) (Cetuximab), an IgG1 monoclonalantibody, in non-small cell lung cancer. The large, randomized PhaseII trial was designed to select an ERBITUX-chemotherapy regimen forfuture evaluation and subsequent inclusion in a Phase III trial. Thisstudy was presented today in an oral session at the American Societyof Clinical Oncology (ASCO) 42nd Annual Meeting by Karen Kelly, M.D.,Clinical Director of the Thoracic Oncology Program, University ofColorado Cancer Center.

A total of 225 untreated patients with advanced stage non-smallcell lung cancer (NSCLC), both squamous and non-squamous cell, wereenrolled in the study and randomized to receive either chemotherapy(paclitaxel plus carboplatin) plus ERBITUX (n=106) or the same dosesof chemotherapy followed by ERBITUX (n=119). The primary endpoint ofthe study was overall survival. The regimen that produced a mediansurvival of at least 10 months would be declared a candidate forfurther evaluation. Median survival was 10 months in the concurrentERBITUX treatment arm and 9 months in the consecutive ERBITUXtreatment arm. The concurrent regimen of chemotherapy and ERBITUX metthe study's criteria for continued evaluation. Secondary endpointsincluded response rate, which were 37% and 25% in the concurrent andconsecutive treatment arms, respectively, and median progression freesurvival, which was the same in both treatment groups at 4 months.Response rate to concurrent chemotherapy and ERBITUX is among thehighest observed in this treatment setting in a multicentercooperative group study.

Investigators concluded that no significant differences inefficacy or toxicity were observed between the treatment arms. Theserious adverse events (Grade 3/4) observed in the concurrent ERBITUXtreatment arm and in the consecutive ERBITUX treatment arm wereneutropenia (41%/37%), rash (12%, 5%), febrile neutropenia (4%, 2%),and allergic reaction (5%, 0%) respectively.

ERBITUX's role in the treatment of NSCLC in combination withchemotherapy, other biologics and with radiation is currently underevaluation in different disease settings. The NCI-sponsored researchgroups involved, in addition to SWOG, include the Radiation TreatmentOncology Group (RTOG), Cancer and Leukemia Group B (CALGB) and EasternCooperative Oncology Group (ECOG).

About ERBITUX(R) (Cetuximab)

ERBITUX is an IgG1 monoclonal antibody (IgG1 MAb) designed toinhibit the function of a molecular structure expressed on the surfaceof normal and tumor cells called the epidermal growth factor receptor(EGFR, HER1, c-ErbB-1). EGFR is part of a signaling pathway that islinked to the growth, development, and survival of many human cancercells. In vitro assays and in vivo animal studies have shown thatbinding of ERBITUX to the EGFR blocks phosphorylation, resulting inmultiple EGFR-mediated anti-tumor effects. Additionally, as an IgG1MAb, ERBITUX has been shown in vitro to mediate the recruitment of thebody's immune system defenses to attack cancer cells(antibody-dependent cell-mediated cytotoxicity) in certain human tumortypes. While the specific mechanism of ERBITUX' anti-tumor effect(s)in vivo is unknown, the combination of these processes may contributeto the overall therapeutic effect of ERBITUX.

ERBITUX (Cetuximab), in combination with radiation therapy, isindicated for the treatment of locally or regionally advanced squamouscell carcinoma of the head and neck. ERBITUX as a single agent isindicated for the treatment of patients with recurrent or metastaticsquamous cell carcinoma of the head and neck for whom priorplatinum-based therapy has failed.

ERBITUX is indicated for the treatment of EGFR-expressing,metastatic colorectal carcinoma in combination with irinotecan forpatients who are refractory to irinotecan-based chemotherapy, and as asingle agent for patients who are intolerant to irinotecan-basedtherapy. The effectiveness of ERBITUX in EGFR-expressing mCRC canceris based on objective response rates. Currently, no data are availablein mCRC that demonstrate an improvement in disease-related symptoms orincreased survival with ERBITUX.

For full prescribing information, including boxed WARNINGSregarding infusion reactions and cardiopulmonary arrest, visithttp://www.ERBITUX.com.

Important Safety Information

Grade 3/4 infusion reactions, rarely with fatal outcome (<1 in1000), occurred in approximately 3% (46/1485) of patients receivingERBITUX (Cetuximab) therapy, characterized by rapid onset of airwayobstruction (bronchospasm, stridor, hoarseness), urticaria,hypotension, and/or cardiac arrest. Severe infusion reactions requireimmediate and permanent discontinuation of ERBITUX therapy.

Most reactions (90%) were associated with the first infusion ofERBITUX despite the use of prophylactic antihistamines. Caution mustbe exercised with every ERBITUX infusion as there were patients whoexperienced their first severe infusion reaction during laterinfusions. A 1-hour observation period is recommended following theERBITUX infusion. Longer observation periods may be required inpatients 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 treatedwith radiation therapy and ERBITUX as compared to none of 212 patientstreated with radiotherapy alone. Fatal events occurred within 1 to 43days after the last ERBITUX treatment. ERBITUX in combination withradiation therapy should be used with caution in patients with knowncoronary artery disease, congestive heart failure and arrhythmias.Close monitoring of serum electrolytes, including serum magnesium,potassium, and calcium during and after Cetuximab therapy isrecommended.

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

In clinical studies of ERBITUX, dermatologic toxicities, includingacneform rash, skin drying and fissuring, and inflammatory andinfectious sequelae (eg, blepharitis, cheilitis, cellulitis, cyst)were reported. In 208 patients receiving ERBITUX + RT, acneform rashwas reported in 87% (17% severe) as compared to 10% in 212 patientstreated with radiation therapy alone (1% severe). In patientsreceiving ERBITUX alone, 76% (N=103) experienced acneform rash (1%severe). Severe (Grade 3/4) acneform rash was reported in 11% of 774patients with metastatic colorectal cancer treated with ERBITUX. Sunexposure may exacerbate these effects. A related nail disorder,occurring in 12% (0.4% Grade 3) of patients, was characterized as aparonychial inflammation.

The safety of ERBITUX in combination with radiation therapy andcisplatin has not been established. Death and serious cardiotoxicitywere 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 cellcarcinoma of the head and neck. Two of 21 patients died, one as aresult of pneumonia and one of an unknown cause. Four patientsdiscontinued treatment due to adverse events. Two of thesediscontinuations were due to cardiac events (myocardial infarction inone patient and arrhythmia, diminished cardiac output, and hypotensionin the other patient).

The incidence of hypomagnesemia (both overall and severe (NCI CTCGrades 3 & 4)) was increased in patients receiving ERBITUX alone or incombination with chemotherapy as compared to those receiving bestsupportive care or chemotherapy alone based on ongoing, controlledclinical trials in 244 patients. Approximately one-half of thesepatients receiving ERBITUX experienced hypomagnesemia and 10-15%experienced severe hypomagnesemia. Electrolyte repletion was necessaryin some patients and in severe cases, intravenous replacement wasrequired. Patients receiving ERBITUX therapy should be periodicallymonitored for hypomagnesemia, and accompanying hypocalcemia andhypokalemia during, and up to 8 weeks following the completion of,ERBITUX therapy

The most serious adverse reactions associated with ERBITUX incombination with radiation therapy in 208 patients with head and neckcancer 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 mCRCclinical trials (N=774) were infusion reaction (3%), dermatologictoxicity (1%), interstitial lung disease (0.4%), fever (5%), sepsis(3%), kidney failure (2%), pulmonary embolus (1%), dehydration (5% inpatients receiving ERBITUX with irinotecan, 2% in patients receivingERBITUX as a single agent) and diarrhea (6% in patients receivingERBITUX with irinotecan, 0.2% in patients receiving ERBITUX as asingle agent).

The overall incidence of late radiation toxicities (any grade) washigher with ERBITUX in combination with radiation therapy comparedwith 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%), andbone (4%/5%) in the ERBITUX and radiation versus radiation alone arms,respectively.

The incidence of Grade 3 or 4 late radiation toxicities weregenerally similar between the radiation therapy alone and the ERBITUXplus radiation therapy arms.

The most common adverse events seen in patients with carcinomas ofthe head and neck receiving ERBITUX in combination with radiationtherapy (n=208) versus radiation alone (n=212) weremucositis-stomatitis (93%/94%), acneform rash (87%/10%), radiationdermatitis (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 adverseevents seen in patients receiving ERBITUX as a single agent (N=103)were acneform rash (76%), asthenia (45%), pain (28%), fever (27%) andweight loss (27%). The most common adverse events seen in patientsreceiving 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%), andheadache (14%/26%).

About Lung Cancer

According to the American Cancer Society, nearly 175,000 Americanswill be diagnosed with lung cancer this year, accounting for 12% ofcancer diagnoses. Additionally, more than 160,000 will die from lungcancer in 2006, and the disease is the most common cancer-relateddeath in men and women. There are two types of lung cancer, non-smallcell and small-cell lung cancer. Approximately 87% of all lung cancersare the non-small cell type.(1)

About ImClone Systems

ImClone Systems Incorporated is committed to advancing oncologycare by developing a portfolio of targeted biologic treatmentsdesigned to address the medical needs of patients with a variety ofcancers. The Company's research and development programs includegrowth 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 inNew York City, with additional administration and manufacturingfacilities in Branchburg, New Jersey.

Certain matters discussed in this news release may constituteforward-looking statements within the meaning of the PrivateSecurities Litigation Reform Act of 1995 and the Federal securitieslaws. Although the company believes that the expectations reflected insuch forward-looking statements are based upon reasonable assumptionsit can give no assurance that its expectations will be achieved.Forward-looking information is subject to certain risks, trends anduncertainties that could cause actual results to differ materiallyfrom those projected. Many of these factors are beyond the company'sability to control or predict. Important factors that may cause actualresults to differ materially and could impact the company and thestatements contained in this news release can be found in thecompany's filings with the Securities and Exchange Commission,including quarterly reports on Form 10-Q, current reports on Form 8-Kand annual reports on Form 10-K. For forward-looking statements inthis news release, the company claims the protection of the safeharbor for forward-looking statements contained in the PrivateSecurities Litigation Reform Act of 1995. The company assumes noobligation to update or supplement any forward-looking statementswhether as a result of new information, future events or otherwise.

(1) American Cancer Society: Cancer Facts and Figures 2006.http://www.cancer.org/downloads/STT/CAFF2006PWSecured.pdf. Accessed5/16/06.