Cetuximab

ERBITUX ® is an epidermal growth factor receptor (EGFR) antagonist indicated for treatment of: Head and Neck Cancer Locally or regionally advanced squamous cell carcinoma of the head and neck in combination with radiation therapy. ( 1.1 , 14.1 ) Recurrent locoregional disease or metastatic squamous cell carcinoma of the head and neck in combination with platinum-based therapy with fluorouracil. ( 1.1 , 14.1 ) Recurrent or metastatic squamous cell carcinoma of the head and neck progressing after platinum-based therapy. ( 1.1 , 14.1 ) Colorectal Cancer K-Ras wild-type, EGFR-expressing, metastatic colorectal cancer as determined by an FDA-approved test in combination with FOLFIRI for first-line treatment, in combination with irinotecan in patients who are refractory to irinotecan-based chemotherapy, as a single-agent in patients who have failed oxaliplatin- and irinotecan-based chemotherapy or who are intolerant to irinotecan. ( 1.2 , 5.7 , 12.1 , 14.2 ) Limitations of Use: ERBITUX is not indicated for treatment of Ras-mutant colorectal cancer or when the results of the Ras mutation tests are unknown. ( 5.7 ) BRAF V600E Mutation-Positive Metastatic Colorectal Cancer (CRC) in combination with encorafenib, for the treatment of adult patients with metastatic colorectal cancer (CRC) with a BRAF V600E mutation, as detected by an FDA-approved test, after prior therapy. ( 1.3 )

1.1 Squamous Cell Carcinoma of the Head and Neck (SCCHN) ERBITUX ® is indicated: in combination with radiation therapy for the initial treatment of locally or regionally advanced squamous cell carcinoma of the head and neck (SCCHN). in combination with platinum-based therapy with fluorouracil for the first-line treatment of patients with recurrent locoregional disease or metastatic SCCHN. as a single-agent for the treatment of patients with recurrent or metastatic SCCHN for whom prior platinum-based therapy has failed. 1.2 K-Ras Wild-type, EGFR-expressing Colorectal Cancer (CRC) ERBITUX is indicated for the treatment of K-Ras wild-type, epidermal growth factor receptor (EGFR)-expressing, metastatic colorectal cancer (mCRC) as determined by an FDA-approved test [see Dosage and Administration ( 2.2 )] : in combination with FOLFIRI (irinotecan, fluorouracil, leucovorin) for first-line treatment, in combination with irinotecan in patients who are refractory to irinotecan-based chemotherapy, as a single-agent in patients who have failed oxaliplatin- and irinotecan-based chemotherapy or who are intolerant to irinotecan. Limitations of Use: ERBITUX is not indicated for treatment of Ras-mutant colorectal cancer or when the results of the Ras mutation tests are unknown [see Warnings and Precautions ( 5.7 )] . 1.3 BRAF V600E Mutation-Positive Metastatic Colorectal Cancer (CRC) ERBITUX is indicated, in combination with encorafenib, for the treatment of adult patients with metastatic colorectal cancer (CRC) with a BRAF V600E mutation, as detected by an FDA-approved test, after prior therapy [see Dosage and Administration ( 2.3 )] .

Injection: 100 mg/50 mL (2 mg/mL) or 200 mg/100 mL (2 mg/mL) as a clear, colorless solution in a single-dose vial. Injection: 100 mg/50 mL (2 mg/mL) or 200 mg/100 mL (2 mg/mL) in a single-dose vial. ( 3 )

None. None. ( 4 )

Infusion Reactions: Monitor patients following infusion. Immediately stop and permanently discontinue ERBITUX for serious infusion reactions. ( 2.5 , 5.1 ) Cardiopulmonary Arrest: Monitor serum electrolytes during and after ERBITUX. ( 5.2 , 5.6 ) Pulmonary Toxicity: Interrupt or permanently discontinue for acute onset or worsening of pulmonary symptoms. ( 2.5 , 5.3 ) Dermatologic Toxicity: Monitor for dermatologic toxicities or infectious sequelae. Limit sun exposure. ( 2.5 , 5.4 ) Hypomagnesemia and Accompanying Electrolyte Abnormalities: Monitor during treatment and for at least 8 weeks following the completion. Replete electrolytes as necessary. ( 5.6 ) Increased tumor progression, increased mortality, or lack of benefit observed in patients with Ras-mutant mCRC. ( 5.7 ) Embryo-Fetal Toxicity: Can cause fetal harm. Advise females of potential risk to the fetus and to use effective contraception. ( 5.8 , 8.1 , 8.3 )

5.1 Infusion Reactions ERBITUX can cause serious and fatal infusion reactions. Infusion reactions of any grade occurred in 8.4% of 1373 patients who received ERBITUX across clinical trials. Severe (Grades 3 and 4) infusion reactions occurred in 2.2% of patients [see Adverse Reactions ( 6.1 )] . Signs and symptoms included rapid onset of airway obstruction (bronchospasm, stridor, hoarseness), hypotension, shock, loss of consciousness, myocardial infarction, and/or cardiac arrest. The risk of anaphylactic reactions may be increased in patients with a history of tick bites, red meat allergy, or in the presence of IgE antibodies directed against galactose-α-1,3-galactose (alpha-gal). Consider testing patients for alpha-gal IgE antibodies using FDA-cleared methods prior to initiating ERBITUX. Negative results for alpha-gal antibodies do not rule out the risk of severe infusion reactions. Approximately 90% of severe infusion reactions occurred with the first infusion despite premedication with antihistamines. Infusion reactions may occur during or several hours following completion of the infusion. Premedicate with a histamine-1(H 1 ) receptor antagonist as recommended [see Dosage and Administration ( 2.4 )] . Monitor patients for at least 1 hour following each ERBITUX infusion, in a setting with resuscitation equipment and other agents necessary to treat anaphylaxis. In patients requiring treatment for infusion reactions, monitor for more than 1 hour to confirm resolution of the reaction. Interrupt the infusion and upon recovery, resume the infusion at a slower rate or permanently discontinue ERBITUX based on severity [see Dosage and Administration ( 2.5 )] .

5.2 Cardiopulmonary Arrest ERBITUX can cause cardiopulmonary arrest. Cardiopulmonary arrest or sudden death occurred in 2% of 208 patients treated with radiation therapy and ERBITUX in BONNER. Three patients with prior history of coronary artery disease died at home, with myocardial infarction as the presumed cause of death. One of these patients had arrhythmia and one had congestive heart failure. Death occurred 27, 32, and 43 days after the last dose of ERBITUX. One patient with no prior history of coronary artery disease died one day after the last dose of ERBITUX. In EXTREME, fatal cardiac disorders and/or sudden death occurred in 3% of 219 patients treated with a cetuximab product in combination with platinum-based therapy and fluorouracil. Carefully consider use of ERBITUX with radiation therapy or platinum-based therapy with fluorouracil in patients with SCCHN with a history of coronary artery disease, congestive heart failure, or arrhythmias. Monitor serum electrolytes, including serum magnesium, potassium, and calcium, during and after ERBITUX [see Warnings and Precautions ( 5.6 )] .

5.3 Pulmonary Toxicity ERBITUX can cause interstitial lung disease (ILD). ILD, including 1 fatality, occurred in <0.5% of 1570 patients receiving ERBITUX in clinical trials. Monitor patients for signs and symptoms of pulmonary toxicity. Interrupt or permanently discontinue ERBITUX for acute onset or worsening of pulmonary symptoms. Permanently discontinue ERBITUX for confirmed ILD [see Dosage and Administration ( 2.5 )] .

5.4 Dermatologic Toxicity ERBITUX can cause dermatologic toxicities, including acneiform rash, skin drying and fissuring, paronychial inflammation, infectious sequelae (for example, S. aureus sepsis, abscess formation, cellulitis, blepharitis, conjunctivitis, keratitis/ulcerative keratitis with decreased visual acuity, cheilitis), and hypertrichosis. Acneiform rash occurred in 82% of the 1373 patients who received ERBITUX across clinical trials. Severe (Grades 3 or 4) acneiform rash occurred in 10% of patients [see Adverse Reactions ( 6.1 )]. Acneiform rash usually developed within the first two weeks of therapy; the rash lasted more than 28 days after stopping ERBITUX in most patients. Life-threatening and fatal bullous mucocutaneous disease with blisters, erosions, and skin sloughing, has been observed in patients who received ERBITUX. It could not be determined whether these mucocutaneous adverse reactions were directly related to EGFR inhibition or to idiosyncratic immune-related effects (e.g., Stevens-Johnson syndrome or toxic epidermal necrolysis). Monitor patients receiving ERBITUX for dermatologic toxicities and infectious sequelae. Instruct patients to limit sun exposure during ERBITUX therapy. Withhold, reduce dose or permanently discontinue ERBITUX based on severity of acneiform rash or mucocutaneous disease [see Dosage and Administration ( 2.5 )] .

5.5 Risks Associated with Use in Combination with Radiation and Cisplatin In a controlled study, 940 patients with locally advanced SCCHN were randomized 1:1 to receive either ERBITUX in combination with radiation therapy and cisplatin or radiation therapy and cisplatin alone. The addition of ERBITUX resulted in an increase in the incidence of Grade 3 and 4 mucositis, radiation recall syndrome, acneiform rash, cardiac events, and electrolyte disturbances compared to radiation and cisplatin alone. Adverse reactions with fatal outcome were reported in 4% of patients in the ERBITUX combination arm and 3% in the control arm. In the ERBITUX arm, 2% experienced myocardial ischemia compared to 0.9% in the control arm. The main efficacy outcome of the study was progression-free survival (PFS). The addition of ERBITUX to radiation and cisplatin did not improve PFS. ERBITUX is not indicated for the treatment of SCCHN in combination with radiation and cisplatin.

5.6 Hypomagnesemia and Accompanying Electrolyte Abnormalities ERBITUX can cause hypomagnesemia. Hypomagnesemia occurred in 55% of 365 patients receiving ERBITUX in Study CA225-025 and two other clinical trials in patients with colorectal cancer (CRC) or head and neck cancer, including Grades 3 and 4 in 6% to 17%. In EXTREME, where a cetuximab product was administered in combination with platinum-based therapy, the addition of cetuximab to cisplatin and fluorouracil resulted in an increased incidence of hypomagnesemia of any grade (14%) and of Grade 3 or 4 hypomagnesemia (7%). Hypomagnesemia of any grade occurred in 4% of patients who received cetuximab, carboplatin, and fluorouracil. No patient experienced Grade 3 or 4 hypomagnesemia [see Adverse Reactions ( 6.1 )]. Hypomagnesemia and accompanying electrolyte abnormalities can occur days to months after initiating ERBITUX. Monitor patients weekly during treatment for hypomagnesemia, hypocalcemia, and hypokalemia, and for at least 8 weeks following the completion of ERBITUX. Replete electrolytes as necessary.

5.7 Increased Tumor Progression, Increased Mortality, or Lack of Benefit in Patients with Ras-Mutant mCRC ERBITUX is not indicated for the treatment of patients with CRC that harbor somatic mutations in exon 2 (codons 12 and 13), exon 3 (codons 59 and 61), and exon 4 (codons 117 and 146) of either K-Ras or N-Ras and hereafter is referred to as “Ras” or when the Ras status is unknown. […]

The following adverse reactions are discussed in greater detail in other sections of the label: Infusion reactions [see Warnings and Precautions ( 5.1 )] . Cardiopulmonary arrest [see Warnings and Precautions ( 5.2 )] . Pulmonary toxicity [see Warnings and Precautions ( 5.3 )] . Dermatologic toxicity [see Warnings and Precautions ( 5.4 )] . Hypomagnesemia and Electrolyte Abnormalities [see Warnings and Precautions ( 5.6 )] . The most common adverse reactions (incidence ≥25%) with Erbitux as a single-agent or in combination with radiotherapy or chemotherapy (FOLFIRI, Irinotecan and 5-Fluorouracil/Platinum) are: cutaneous adverse reactions (including rash, pruritus, and nail changes), headache, diarrhea, and infection. ( 6 ) The most common adverse reactions (>25%) for ERBITUX, in combination with encorafenib, are fatigue, nausea, diarrhea, dermatitis acneiform, abdominal pain, decreased appetite, arthralgia, and rash. ( 6 ). To report SUSPECTED ADVERSE REACTIONS, contact Eli Lilly and Company at 1-800-LillyRx (1-800-545-5979) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The data described in Warnings and Precautions reflect exposure to ERBITUX in 1373 patients with SCCHN or CRC enrolled in clinical trials and treated at the recommended dosage for a median of 7 to 14 weeks [see Clinical Studies ( 14.1 , 14.2 )] . The most common adverse reactions in clinical trials with ERBITUX as a single-agent or in combination with radiotherapy or chemotherapy [FOLFIRI, irinotecan and 5-fluorouracil/platinum] (incidence ≥25%) include cutaneous adverse reactions (including rash, pruritus, and nail changes), headache, diarrhea, and infection. Squamous Cell Carcinoma of the Head and Neck (SCCHN) In Combination with Radiation Therapy The safety of ERBITUX in combination with radiation therapy compared to radiation therapy alone was evaluated in BONNER. The data described below reflect exposure to ERBITUX in 420 patients with locally or regionally advanced SCCHN. ERBITUX was administered at the recommended dosage (400 mg/m 2 initial dose, followed by 250 mg/m 2 weekly). Patients received a median of 8 infusions (range 1 to 11) [see Clinical Studies ( 14.1 )] . Table 2 provides the frequency and severity of adverse reactions in BONNER. Table 2: Selected Adverse Reactions in ≥10% of Patients with Locoregionally Advanced SCCHN (BONNER) a Adverse Reaction ERBITUX with Radiation (n=208) Radiation Therapy Alone (n=212) Grades 1–4 b Grades 3 and 4 Grades 1–4 Grades 3 and 4 a Adverse reactions occurring in ≥10% of patients in the ERBITUX combination arm and at a higher incidence (≥5%) compared to the radiation alone arm. b Adverse reactions were graded using the NCI CTC, version 2.0. c Includes cases also reported as infusion reaction. d Infusion reaction defined as any event described at any time during the clinical study as “allergic reaction” or “anaphylactoid reaction”, or any event occurring on the first day of dosing described as “allergic reaction”, “anaphylactoid reaction”, “fever”, “chills”, “chills and fever”, or “dyspnea”. e Based on laboratory measurements, not on reported adverse reactions, the number of subjects with tested samples varied from 205–206 for ERBITUX with Radiation arm; 209–210 for Radiation alone. f Acneiform rash defined as any event described as “acne”, “rash”, “maculopapular rash”, “pustular rash”, “dry skin”, or “exfoliative dermatitis”. General Asthenia 56 4 49 5 Fever c 29 1 13 1 Headache 19 <1 8 <1 Chills c 16 0 5 0 Infusion Reaction d 15 3 2 0 Infection 13 1 9 1 Gastrointestinal Nausea 49 2 37 2 Emesis 29 2 23 4 Diarrhea 19 2 13 1 Dyspepsia 14 0 9 1 Metabolism and Nutrition Weight Loss 84 11 72 7 Dehydration 25 6 19 8 Increased Alanine Transaminase e 43 2 21 1 Increased Aspartate Transaminase e 38 1 24 1 Increased Alkaline Phosphatase e 33 <1 24 0 Respiratory Pharyngitis 26 3 19 4 Dermatologic Acneiform Rash f 87 17 10 1 Radiation Dermatitis 86 23 90 18 Application Site Reaction 18 0 12 1 Pruritus 16 0 4 0 The overall incidence of late radiation toxicities (any grade) was higher for patients receiving ERBITUX in combination with radiation therapy compared with radiation therapy alone. The following sites were affected: salivary glands (65% versus 56%), larynx (52% versus 36%), subcutaneous tissue (49% versus 45%), mucous membrane (48% versus 39%), esophagus (44% versus 35%), skin (42% versus 33%). The incidence of Grade 3 or 4 late radiation toxicities was similar between the radiation therapy alone and the ERBITUX with radiation treatment groups. In Combination with Platinum-based Therapy and Fluorouracil The safety of a cetuximab product in combination with platinum-based therapy and fluorouracil or platinum-based therapy and fluorouracil alone was evaluated in EXTREME. The data described below reflect exposure to a cetuximab product in 434 patients with recurrent locoregional disease or metastatic SCCHN. Because ERBITUX provides approximately 22% higher exposure relative to the cetuximab product, the data provided below may underestimate the incidence and severity of adverse reactions anticipated with ERBITUX for this indication; however, the tolerability of the recommended dose is supported by safety data from additional studies of ERBITUX [see Clinical Pharmacology ( 12.3 )] . Cetuximab was administered intravenously at a dosage of 400 mg/m 2 for the initial dose, followed by 250 mg/m 2 weekly. Patients received a median of 17 infusions (range 1 to 89) [see Clinical Studies ( 14.1 )] . Table 3 provides the frequency and severity of adverse reactions in EXTREME. Table 3: Selected Adverse Reactions in ≥10% of Patients with Recurrent Locoregional Disease or Metastatic SCCHN (EXTREME) a Adverse Reaction Cetuximab with Platinum-based Therapy and fluorouracil (n=219) Platinum-based Therapy and fluorouracil Alone (n=215) Grades 1–4 b Grades 3 and 4 Grades 1–4 Grades 3 and 4 a Adverse reactions occurring in ≥10% of patients in the cetuximab combination arm and at a higher incidence (≥5%) compared to the platinum-based therapy and fluorouracil alone arm. b Adverse reactions were graded using the NCI CTC, version 2.0. c Infusion reaction defined as “anaphylactic reaction”, “hypersensitivity”, “fever and/or chills”, “dyspnea”, or “pyrexia” on the first day of dosing. d Infection excludes sepsis-related events which are presented separately. e Acneiform rash defined as “acne”, “dermatitis acneiform”, “dry skin”, “exfoliative rash”, “rash”, “rash erythematous”, “rash macular”, “rash papular”, or “rash pustular”. Chemotherapy = cisplatin and fluorouracil or carboplatin and fluorouracil Eye Conjunctivitis 10 0 0 0 Gastrointestinal Nausea 54 4 47 4 Diarrhea 26 5 16 1 General and Administration Site Pyrexia 22 0 13 1 Infusion Reaction c 10 2 <1 0 Infections Infection d 44 11 27 8 Metabolism and Nutrition Anorexia 25 5 14 1 Hypocalcemia 12 4 5 1 Hypokalemia 12 7 7 5 Hypomagnesemia 11 5 5 1 Dermatologic Acneiform Rash e 70 9 2 0 Rash 28 5 2 0 Acne 22 2 0 0 Dermatitis Acneiform 15 2 0 0 Dry Skin 14 0 <1 0 Alopecia 12 0 7 0 For cardiac disorders, approximately 9% of patients in both treatment arms in EXTREME experienced a cardiac event. The majority of these events occurred in patients who received cisplatin and fluorouracil with or without cetuximab. Cardiac disorders were observed in 11% and 12% of patients who received cisplatin and fluorouracil with or without cetuximab, respectively, and 6% and 4% in patients who received carboplatin and fluorouracil with or without cetuximab, respectively. In both arms, the incidence of cardiovascular events was higher in the cisplatin and fluorouracil containing subgroup. […]

Lactation: Advise not to breastfeed. ( 8.2 )

8.1 Pregnancy Risk Summary Based on findings from animal studies and its mechanism of action [see Clinical Pharmacology ( 12.1 )] , ERBITUX can cause fetal harm when administered to a pregnant woman. There are no available data for ERBITUX exposure in pregnant women. In an animal reproduction study, intravenous administration of cetuximab once weekly to pregnant cynomolgus monkeys during the period of organogenesis resulted in an increased incidence of embryolethality and abortion. Disruption or depletion of EGFR in animal models results in impairment of embryo-fetal development including effects on placental, lung, cardiac, skin, and neural development ( see Data ). Human IgG is known to cross the placental barrier; therefore, cetuximab may be transmitted from the mother to the developing fetus. Advise pregnant women of the potential risk to a fetus. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20% respectively. Data Animal Data Pregnant cynomolgus monkeys were administered cetuximab intravenously once weekly during the period of organogenesis (gestation day [GD] 20-48) at dose levels 0.4 to 4 times the recommended dose of ERBITUX based on body surface area (BSA). Cetuximab was detected in the amniotic fluid and in the serum of embryos from treated dams on GD 49. While no fetal malformations occurred in offspring, there was an increased incidence of embryolethality and abortions at doses approximately 1 to 4 times the recommended dose of ERBITUX based on BSA. In mice, EGFR is critically important in reproductive and developmental processes including blastocyst implantation, placental development, and embryo-fetal/postnatal survival and development. Reduction or elimination of embryo-fetal or maternal EGFR signaling can prevent implantation, can cause embryo-fetal loss during various stages of gestation (through effects on placental development), and can cause developmental anomalies and early death in surviving fetuses. Adverse developmental outcomes were observed in multiple organs in embryos/neonates of mice with disrupted EGFR signaling.

8.2 Lactation Risk Summary There is no information regarding the presence of ERBITUX in human milk, the effects on the breastfed infant, or the effects on milk production. Human IgG antibodies can be excreted in human milk. Due to the potential for serious adverse reactions in breastfed infants from ERBITUX, advise women not to breastfeed during treatment with ERBITUX and for 2 months after the last dose of ERBITUX.

8.3 Females and Males of Reproductive Potential Pregnancy Testing Verify pregnancy status in females of reproductive potential prior to initiating ERBITUX [see Use in Specific Population ( 8.1 )] . Contraception Based on its mechanism of action, ERBITUX can cause harm to the fetus when administered to a pregnant woman [see Use in Specific Populations ( 8.1 )] . Females Advise females of reproductive potential to use effective contraception during treatment with ERBITUX and for 2 months after the last dose of ERBITUX. Infertility Females Based on animal studies, ERBITUX may impair fertility in females of reproductive potential [see Nonclinical Toxicology ( 13.1 )] .

8.4 Pediatric Use The safety and effectiveness of ERBITUX in pediatric patients have not been established. The pharmacokinetics of cetuximab, in combination with irinotecan, were evaluated in pediatric patients with refractory solid tumors in an open-label, single-arm, dose-finding study. ERBITUX was administered once-weekly, at doses up to 250 mg/m 2 , to 27 patients ranging from 1 to 12 years old; and in 19 patients ranging from 13 to 18 years old. No new safety signals were identified in pediatric patients. The pharmacokinetics of cetuximab between the two age groups were similar following a single dose of 75 mg/m 2 and 150 mg/m 2 . The volume of the distribution appears to be independent of dose and approximates the vascular space of 2 L/m 2 to 3 L/m 2 . Following a single dose of 250 mg/m 2 , the mean AUC 0-inf (CV%) was 17.7 mg*h/mL (34%) in the younger age group (1–12 years, n=9) and 13.4 mg*h/mL (38%) in the adolescent group (13–18 years, n=6). The mean half-life of cetuximab was 110 hours (69 to 188 hours) in the younger group and 82 hours (55 to 117 hours) in the adolescent group.

8.5 Geriatric Use Of the 1662 patients with advanced colorectal cancer who received ERBITUX with irinotecan, with FOLFIRI or as single-agent in six studies (BOND, IMCL-CP02-9923, IMCL-CP02-0141, IMCL-CP02-0144, CA225-025 and CRYSTAL), 35% of patients were 65 years of age or older. No overall differences in safety or efficacy were observed between these patients and younger patients. Clinical studies of ERBITUX conducted in patients with head and neck cancer did not include sufficient number of subjects aged 65 and over to determine whether they respond differently from younger subjects. Of the 216 patients with BRAF V600E mutation positive metastatic CRC who received ERBITUX in combination with encorafenib 300 mg, once daily, 29% were 65 years of age to up to 75 years of age, while 20 (9%) were 75 years of age and over [see Clinical Studies ( 14.3 )] . No overall differences in the safety or effectiveness of ERBITUX plus encorafenib were observed in elderly patients as compared to younger patients.

The epidermal growth factor receptor (EGFR, HER1, c-ErbB-1) is a transmembrane glycoprotein that is a member of a subfamily of type I receptor tyrosine kinases including EGFR, HER2, HER3, and HER4. The EGFR is constitutively expressed in many normal epithelial tissues, including the skin and hair follicle. Expression of EGFR is also detected in many human cancers including those of the head and neck, colon, and rectum. Cetuximab binds specifically to the EGFR 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. In vitro assays and in vivo animal studies have shown that binding of cetuximab 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. Signal transduction through the EGFR results in activation of wild-type Ras proteins, but in cells with activating Ras somatic mutations, the resulting mutant Ras proteins are continuously active regardless of EGFR regulation. In vitro , cetuximab can mediate antibody-dependent cellular cytotoxicity (ADCC) against certain human tumor types. In vitro assays and in vivo animal studies have shown that cetuximab inhibits the growth and survival of tumor cells that express the EGFR. No anti-tumor effects of cetuximab were observed in human tumor xenografts lacking EGFR expression. The addition of cetuximab to radiation therapy or irinotecan in human tumor xenograft models in mice resulted in an increase in anti-tumor effects compared to radiation therapy or chemotherapy alone. In the setting of BRAF-mutant CRC, induction of EGFR-mediated MAPK pathway activation has been identified as a mechanism of resistance to BRAF inhibitors. Combinations of a BRAF inhibitor and agents targeting EGFR have been shown to overcome this resistance mechanism in nonclinical models. Coadministration of cetuximab and encorafenib had an anti-tumor effect greater than either drug alone, in a mouse model of colorectal cancer with mutated BRAF V600E.