Cetuximab: an IgG(1) monoclonal antibody for the treatment of epidermal growth factor receptor-expressing tumours

The epidermal growth factor receptor (EGFR) plays an essential role in normal cell growth and differentiation and in the survival of healthy and cancerous cells. EGFR expression is a common feature of non-haematological malignancies and is associated with poor clinical prognosis. Cetuximab is an IgG(1) monoclonal antibody that blocks EGFR activation. It has efficacy alone, and in combination with irinotecan, in the treatment of metastatic colorectal cancer that has progressed on irinotecan-containing therapy. It has been approved for use in combination with irinotecan in both Switzerland and the US and as monotherapy in the US. Cetuximab also has efficacy in cancers of the head and neck and non-small cell lung cancer. Cetuximab is well-tolerated and does not exacerbate the side effects of co-administered cytotoxic chemotherapy.     

Epidermal growth factor receptor monoclonal antibodies for the treatment of metastatic colorectal cancer

Treatment of metastatic colorectal disease has evolved over the last decade. Two epidermal growth factor receptor (EGFR) monoclonal antibodies--cetuximab and panitumumab--have been developed in an effort to provide yet another therapeutic option. The EGFR is a transmembrane glycoprotein, expressed constitutively throughout the body and found on many epithelial tissues. The monoclonal antibodies bind to and inhibit the activation of the receptor in the body. This inhibition prevents tumor cell growth, angiogenesis, invasion, and metastasis, and induces apoptosis. Cetuximab and panitumumab exhibit nonlinear pharmacokinetics. Both monoclonal antibodies are approved for the treatment of refractory metastatic colorectal cancer. Cetuximab in combination with irinotecan has significantly better response rates and progression-free survival compared with those of cetuximab or irinotecan alone. Cetuximab and panitumumab as monotherapy have shown significantly better response rates and progression-free survival compared with best supportive care in patients refractory to irinotecan and oxaliplatin. In the Cetuximab Combined with Irinotecan in First Line Therapy for Metastatic Colorectal Cancer (CRYSTAL) trial, treatment-na?ve patients received cetuximab in combination with the chemotherapy regimen infusional leucovorin, fluorouracil, and irinotecan (FOLFIRI) or FOLFIRI alone; the difference in progression-free survival was statistically significant but suggested only a modest benefit over FOLFIRI alone (8.9 vs 8 mo, p=0.036). Results of a preplanned analysis of the first 231 events in the Panitumumab Advanced Colorectal Cancer Evaluation (PACCE) trial favored the control group (chemotherapy regimen with folinic acid [leucovorin], fluorouracil, and oxaliplatin [FOLFOX] plus bevacizumab) instead of the control group plus panitumumab. For clinical consideration, many trials have shown that the intensity or absence of EGFR expression is not a clinically significant predictor of outcomes. Development and intensity of a rash are suggested to be a positive predictor of outcomes in patients. The most common adverse events of EGFR monoclonal antibody therapy are rash, diarrhea, and hypomagnesemia. Other serious but not common adverse events include hypersensitivity reactions and pulmonary toxicity. The availability of EGFR monoclonal antibodies has provided another weapon in the arsenal to treat refractory metastatic colorectal cancer. They have shown safety and efficacy in combination with other chemotherapy regimens and as monotherapy; however, their use as metastatic colorectal cancer therapy needs to be further explored.     

Cetuximab: new drug. Metastatic colorectal cancer: an inappropriate evaluation

(1) In patients with metastatic colorectal cancer initially treated with irinotecan combination therapy, second-line therapy with a combination of fluorouracil, folinic acid and oxaliplatin resulted in a median survival time of 21 months after the start of first-line chemotherapy, in one clinical trial. (2) Cetuximab, an antibody directed against the epidermal growth factor receptor (EGFR), is indicated for patients with EGF-expressing metastatic colorectal cancer, after failure of irinotecan-based chemotherapy. (3) A comparative trial involving 329 patients showed that the cetuximab + irinotecan combination was more effective than cetuximab monotherapy in terms of progression-free survival time (4.1 versus 1.5 months). Three non comparative trials did not show that adding cetuximab to irinotecan improved the efficacy of irinotecan. (4) Nearly 90% of patients taking cetuximab developed cutaneous adverse effects (usually acne), which were severe in about 15% of cases. About 5% of cetuximab infusions were associated with occasionally severe hypersensitivity reactions. (5) More pertinent comparative trials are underway, but no detailed results were available on 29 April 2005. (6) The cetuximab packaging is somewhat impractical. (7) In practice, given its known toxicity and unproven efficacy, cetuximab currently has no place in the second-line treatment of colorectal cancer.     

Cetuximab: in the treatment of metastatic colorectal cancer

Cetuximab is a chimeric monoclonal antibody highly selective for the epidermal growth factor receptor (EGFR), which is over-expressed by 25-80% of colorectal cancer tumours and associated with advanced disease. Cetuximab induces a broad range of cellular responses in tumours expressing EGFR, enhancing sensitivity to radiotherapy and chemotherapeutic agents. In a large, randomised, open-label, multicentre study in adult patients with irinotecan-refractory, metastatic colorectal cancer expressing EGFR, cetuximab 400 mg/m2 initial dose followed by 250 mg/m2 weekly plus irinotecan (various doses) produced a greater rate of partial response and disease control (partial response plus stable disease), and increased time to disease progression, compared with cetuximab monotherapy; survival was similar in both groups. The same dosage of cetuximab combined with irinotecan, fluorouracil and folinic acid (various regimens) produced partial responses in 43-58% of patients, a complete response in 5% of patients (one study only) and stable disease in 32-52% of patients with treatment-naive metastatic colorectal cancer expressing EGFR in three small, open-label trials. The most common grade 3/4 adverse events associated with cetuximab monotherapy were acne-like rash, asthenia, abdominal pain and nausea/vomiting. In patients receiving cetuximab plus irinotecan, these were diarrhoea, asthenia, leucopenia and neutropenia.     

Cetuximab: a review of its use in squamous cell carcinoma of the head and neck and metastatic colorectal cancer

Cetuximab (Erbitux) is a human-mouse chimeric monoclonal antibody, which competitively binds to the accessible extracellular domain of the epidermal growth factor receptor (EGFR) to inhibit dimerisation and, subsequently, inhibit tumour growth and metastasis. In the EU and the US, cetuximab has been approved for use with concomitant radiotherapy in patients with locally advanced squamous cell carcinoma of the head and neck (SCCHN) and in combination with irinotecan for the treatment of metastatic colorectal cancer (mCRC) in patients with EGFR-expressing tumours who are refractory to irinotecan-based therapy. In the US, cetuximab has also been approved as monotherapy in patients with recurrent or metastatic SCCHN for whom platinum-based therapy has failed and in patients with mCRC who are intolerant of irinotecan-based regimens.In treatment-naive patients with locoregionally advanced SCCHN, cetuximab plus radiotherapy was more effective than radiation therapy alone in prolonging locoregional disease control. In addition, more limited noncomparative data from a large trial indicated a 13% overall objective response rate (ORR) in platinum-refractory patients with SCCHN. In patients with EGFR-expressing mCRC, cetuximab plus irinotecan improved ORR more than cetuximab monotherapy in a trial in irinotecan-refractory patients; however, there was no difference in overall survival (OS) between cetuximab plus irinotecan and cetuximab monotherapy in oxaliplatin-refractory recipients in another trial. In an ongoing trial, progression-free survival (PFS) exceeded 50% after 12 weeks in irinotecan-refractory patients receiving three different dosages of cetuximab plus irinotecan. In another large trial, cetuximab monotherapy prolonged OS compared with best supportive care (BSC) in heavily pretreated patients. Overall, cetuximab treatment had an acceptable tolerability profile, with the majority of adverse events being mild or moderate in severity and clinically manageable. In particular, cetuximab therapy did not exacerbate toxicities commonly associated with chemo- or radiotherapeutic regimens. Albeit occurring with high incidence, adverse cutaneous reactions appear to be a marker for response. Results of ongoing head-to-head comparative trials comparing cetuximab with other biological agents will help to establish definitively the role of cetuximab in the management of SCCHN and mCRC. In the meantime, cetuximab, with its highly targeted mechanism of action and synergistic activity with current treatment modalities, is a valuable treatment option in patients with SCCHN and mCRC.     

EGFR blockade by cetuximab alone or as combination therapy for growth control of hepatocellular cancer

Hepatocellular carcinoma (HCC) is one of the most common cancer-related causes of death worldwide. In light of the very poor 5 year survival new therapeutic approaches are mandatory. Several reports indicate that the epidermal growth factor receptor (EGFR) is expressed frequently in HCC, most likely contributing to the aggressive growth characteristics of these tumors. Cetuximab, a chimeric monoclonal IgG1 antibody directed against the EGFR, potently suppresses the growth of various cancers but its effect on HCC remains to be explored. We therefore studied the antineoplastic potency of cetuximab in human HCC cells alone and in combination with growth factor tyrosine-kinase inhibition (TKI) or HMG-CoA-reductase inhibiton or conventional cytostatics. Cetuximab inhibited growth of p53 wild-type HepG2 hepatocellular cancer cells in a time- and dose-dependent manner. Cetuximab treatment resulted in arresting the cell cycle in the G(1)/G(0)-phase due to an increase of expression of the cyclin-dependent kinase inhibitors p21(Waf1/CIP1) and p27(Kip1) and a decrease in cyclin D1 expression. Additionally, we observed a moderate increase in apoptosis as demonstrated by caspase-3 activation. Combining cetuximab with TKIs (erlotinib or AG1024) or the HMG-CoA-reductase inhibitor fluvastatin or doxorubicin resulted in synergistic antiproliferative effects. In contrast, p53 mutated Huh-7 hepatocellular cancer cells proved to be less sensitive towards cetuximab, but when combined with TKIs or fluvastatin or doxorubicin a pronounced reduction of cell growth was observed. To conclude, our study may provide a rationale for future clinical investigations of cetuximab combination therapy for growth control of hepatocellular cancer.     

A new nanoconstruct for epidermal growth factor receptor-targeted photo-immunotherapy of ovarian cancer

Targeted photodynamic therapy (TPDT) involves the administration of a photosensitizer (PS) conjugated with a targeting moiety followed by light activation. The systemic toxicity associated with conventional therapy may thus be significantly reduced in TPDT due to the dual selectivity provided by the spatial localization of the illumination as well as the target-localizing ability of the conjugate. Herein, a photo-immuno-conjugate-associating-liposome (PICAL) for TPDT has been developed in which the FDA approved benzoporphyrin derivative monoacid A (BPD) and the Cetuximab antibody for epidermal growth factor receptor (EGFR) were associated into a stable Preformed Plain Liposome (PPL) by passive physical adsorption. Results have shown that the BPD molecules adsorbed into PICAL have stable optical behavior and a higher fluorescence quantum yield than free-BPD. The Cetuximab adsorbed into PPL selectively binds to cells that overexpress EGFR. The inhibition of EGFR signaling by PICAL has enhanced PDT-mediated ovarian cancer cell death.From the Clinical EditorIn this basic science study, a photo-immuno-conjugate-associating-liposome for targeted photodynamic therapy is investigated. The FDA-approved benzoporphyrin derivative monoacid A and an epidermal growth factor receptor antibody were assembed into a stable Preformed Plain Liposome (PPL) by passive physical adsorption. The authors demonstrate therapeutic efficacy of the above construct in an ovarian tumor system.     

Modulation of cellular redox state underlies antagonism between oxaliplatin and cetuximab in human colorectal cancer cell lines

Background and purpose:

Oxaliplatin is the first platinum-based compound effective in the treatment of colorectal cancer. Oxaliplatin combined with cetuximab for metastatic colorectal cancer is under evaluation. The preliminary results seem controversial, particularly for the use of cetuximab in K-Ras mutated patients. K-Ras mutation is known to affect redox homeostasis. Here we evaluated how the efficacy of oxaliplatin alone or combined with cetuximab varied according to the Ras mutation and redox status in a panel of colorectal tumour cell lines.

Experimental approach:

Viability was evaluated by methylthiazoletetrazolium assay, reactive oxygen species production by DCFDA and lucigenin on HT29-D4, Caco-2, SW480 and SW620 cell lines.

Key results:

Combination of oxaliplatin and cetuximab was less cytotoxic than oxaliplatin alone in colorectal cells harbouring wild-type Ras and membrane expression of receptors for epidermal growth factor receptor (EGFR), such as HT29-D4 and Caco-2 cells. In contrast, cetuximab did not affect oxaliplatin efficiency in cells harbouring K-Ras^V12 mutation, irrespective of membrane EGFR expression (SW620 and SW480 cells). Transfection of HT29-D4 with K-Ras^V12 decreased oxaliplatin IC₅₀ and impaired cetuximab sensitivity, without affecting expression of membrane EGFR compared with HT29-D4 control. Oxaliplatin efficacy relies on endogenous production of H₂O₂. Cetuximab inhibits H₂O₂ production inhibiting the EGFR/Nox1 NADPH oxidase pathway. Oxaliplatin efficacy was impaired by short hairpin RNA for Nox1 and by catalase (H₂O₂ scavenger).

Conclusions and implications:

Cetuximab limited oxaliplatin efficiency by affecting the redox status of cancer cells through Nox1. Such combined therapy might be improved by controlling H₂O₂ elimination.     

西妥昔单抗联合化疗治疗转移性结直肠癌的观察

目的 观察西妥昔单抗联合化疗方案治疗转移性结直肠癌的近期疗效及不良反应.方法 11例经病理组织学确诊的转移性结直肠癌患者,给予西妥昔单抗联合FOLFOX方案治疗,西妥昔单抗首次给予负荷剂量400 mg/m2,每周给予维持剂量为250 mg/m2.结果 全组11例患者中,完全缓解1例,部分缓解5例,稳定2例,进展3例,有效率54.5％ (6/11),疾病控制率为72.7％ (8/11),中位肿瘤进展时间为8.4个月.主要不良反应为痤疮样皮疹(9例)和腹泻(6例).5例合并肝转移患者中经治疗后1例转化为可切除病灶.患者耐受良好,无治疗相关死亡.结论 西妥昔单抗联合FOLFOX方案治疗转移性结直肠癌疗效较好,不良反应多可耐受.     

Molecularly targeted therapy for gastrointestinal cancer

Receptor and non-receptor tyrosine kinases (TKs) have emerged as clinically useful drug target molecules for treating gastrointestinal cancer. Imatinib mesilate (STI-571, Gleevec(TM)), an inhibitior of bcr-abl TK, which was primarily designed to treat chronic myeloid leukemia is also an inhibitor of c-kit receptor TK, and is currently the drug of choice for the therapy of metastatic gastrointestinal stromal tumors (GISTs), which frequently express constitutively activated forms of the c-kit-receptor. The epidermal growth factor receptor (EGFR), which is involved in cell proliferation, metastasis and angiogenesis, is another important target. The two main classes of EGFR inhibitors are the TK inhibitors and monoclonal antibodies. Gefitinib (ZD1839, Iressa(TM)) has been on trial for esophageal and colorectal cancer (CRC) and erlotinib (OSI-774, Tarceva(TM)) on trial for esophageal, colorectal, hepatocellular, and biliary carcinoma. In addition, erlotinib has been evaluated in a Phase III study for the treatment of pancreatic cancer. Cetuximab (IMC-C225, Erbitux(TM)), a monoclonal EGFR antibody, has been FDA approved for the therapy of irinotecan resistant colorectal cancer and has been tested for pancreatic cancer. Vascular endothelial growth factor (VEGF) and its receptor (VEGFR) are critical regulators of tumor angiogenesis. Bevacizumab (Avastin(TM)), a monoclonal antibody against VEGF, was efficient in two randomized clinical trials investigating the treatment of metastatic colorectal cancer. It is also currently investigated for the therapy of pancreatic cancer in combination with gemcitabine. Other promising new drugs currently under preclinical and clinical evaluation, are VEGFR2 inhibitor PTK787/ZK 222584, thalidomide, farnesyl transferase inhibitor R115777 (tipifarnib, Zarnestra(TM)), matrix metalloproteinase inhibitors, proteasome inhibitor bortezomib (Velcade(TM)), mammalian target of rapamycin (mTOR) inhibitors, cyclooxygenase-2 (COX-2) inhibitors, platelet derived growth factor receptor (PDGF-R) inhibitors, protein kinase C (PKC) inhibitors, mitogen-activated protein kinase kinase (MEK) 1/2 inhibitors, Rous sarcoma virus transforming oncogene (SRC) kinase inhibitors, histondeacetylase (HDAC) inhibitors, small hypoxia-inducible factor (HIF) inhibitors, aurora kinase inhibitors, hedgehog inhibitors, and TGF-beta signalling inhibitors.     

The epidermal growth factor receptor tyrosine kinase inhibitor gefitinib sensitizes colon cancer cells to irinotecan

Epidermal growth factor receptor (EGFR) overactivity plays a significant role in colon cancer biology and has been associated with poor clinical prognosis. Early clinical trials reported efficacy of receptor-targeted compounds, including modulation of clinical irinotecan resistance. We investigated the effects of the EGFR tyrosine kinase inhibitor gefitinib on cellular determinants of irinotecan resistance in human colon cancer cells. At non-cytotoxic concentrations, gefitinib sensitized colon cancer cells to SN-38, the active metabolite of irinotecan. Gefitinib increased the SN-38-mediated induction of protein-linked DNA single-strand breaks in a dose-dependent manner, with no alteration of topoisomerase (Topo) I protein expression or enzymatic activity. Whereas Topo IIbeta protein expression was not affected by gefitinib, significant time- and concentration-dependent downregulation of Topo IIalpha protein and inhibition of its enzymatic function were observed, corresponding to a G1 phase cell cycle arrest. Gefitinib significantly inhibited EGFR-associated signaling molecules, including phospho-mitogen-activated protein kinase or protein kinase C, which may account for decreases in proliferation or topoisomerase activity, respectively. Although a dose-dependent decrease of the BCRP/MXR/ABCP half-transporter was observed under gefitinib, cellular pharmacokinetics revealed no significant differences in accumulation or retention of the active SN-38 lactone using reverse-phase HPLC analysis. This study delineates mechanisms that may contribute to the synergism observed between irinotecan and EGFR inhibitors.     

Antitumor effect and enhancement of cytotoxic drug activity by cetuximab in nasopharyngeal carcinoma cells

BACKGROUND: Nasopharyngeal carcinoma (NPC) is the most common head and neck cancer in southern China and South East Asia. Epidermal growth factor receptor (EGFR) has been proposed as a new target for anticancer therapy. EGFR was over-expressed in 85% of NPC tissues and was associated with poor prognosis. MATERIALS AND METHODS: EGFR protein expression in four NPC cell lines, CNE-2, HONE-1, HK1 and C666-1, was examined by Western immunoblotting. The antitumor effect of cetuximab was studied in the cell lines, either alone or in combination with cisplatin or paclitaxel. RESULTS: EGFR protein expression was highest in the HK1 cell line, moderate in CNE-2 and HONE-1, and lowest in C666-1. Single agent cetuximab demonstrated significant antitumor effect in the HK1 and HONE-1 cell lines, but minimal activity in CNE-2 and C666-1 cells. When cetuximab was combined with cisplatin or paclitaxel in the HK1 and HONE-1 cell lines, an additive enhancement of cytotoxic drug activity was demonstrated. CONCLUSION: Cetuximab demonstrated single agent activity selectively in NPC cell lines with moderate to high EGFR protein expression. Cetuximab could also additively enhance the antitumor effects of cisplatin or paclitaxel in these NPC cell lines. These results support the rationale of combining cetuximab with current standard chemotherapy to further improve the therapeutic ratio in the treatment of NPC. Future studies should aim at defining the predictive markers for response to cetuximab in order to select the responsive tumor for the correctly targeted agents.     

Advanced therapies on BRAF-mutated and KRAS-mutated metastatic colorectal cancer

Colorectal cancer(CRC) is one of the most-diagnosed cancer worldwide, and 30% of patients with CRC have showed a metastatic situation. Monoclonal antibodies(mAbs) that target vascular endothelial growth factor(VEGF) and the epidermal growth factor receptor(EGFR) can achieveantitumor efficacy via antivascular and anticellular effects respectively and have been added into first-line chemotherapy for patients with metastatic colorectal cancer(mCRC). Investigations found that unlike VEGF inhibitors, the efficacy of EGFR inhibitors,such as Cetuximab and panitumumab, is limited to patients with wild-type-KRAS tumors without BRAF mutant. Studies revealed that resistance to EGFR inhibitors result in the poor response to anti-EGFR therapiesthrough acquired mutations of KRAS and BRAF.Considering this situation, in this review, we will focus onresistance mechanism to anti-EGFR therapies and advanced therapies for BRAF-mutated and KRAS-mutated mCRC patients.     

Epidermal growth factor receptor tyrosine kinase inhibitors in late stage clinical trials

The epidermal growth factor receptor (EGFR) is a cell membrane receptor that plays a key role in cancer development and progression. Ligand-activated EGFR-dependent signalling is involved in cell proliferation, apoptosis, angiogenesis and metastatic spread. Targeting the EGFR, therefore, represents a promising molecular approach in cancer treatment. Several anti-EGFR agents are in clinical development. Three drugs are currently in Phase II and III development as single agents, or in combination with other anticancer modalities: IMC-225 (cetuximab/Erbitux?; ImClone), a chimaeric human–mouse monoclonal IgG₁ antibody, which blocks ligand binding and functional activation of the EGFR; OSI-774 (erlotinib/Tarceva?; Genentech/OSI/Roch) and ZD1839 (gefitinib/Iressa^®; AstraZeneca), two small molecule EGFR-selective inhibitors of tyrosine kinase enzymatic activity, which prevent EGFR autophosphorylation and activation. Iressa is the first EGFR-targeting agent to be registered as an anticancer drug in Japan, in Australia and in the US for the third-line treatment of chemoresistant non-small cell lung cancer (NSCLC) patients. This review will focus on the preclinical background and on the results from the first series of clinical trials with these drugs. Furthermore, continuing clinical trials and a series of open clinical issues for the development of optimal strategies of using EGFR-targeting agents will be discussed.     

西妥昔单抗联合化疗治疗消化系统肿瘤的临床研究

目的观察西妥昔单抗联合化疗治疗消化系统肿瘤的疗效及不良反应。方法回顾性分析17例接受西妥昔单抗联合化疗治疗的消化系统肿瘤患者的资料,对其进行疗效评价及安全性分析。合并的化疗方案主要有以奥沙利铂或伊立替康为主的联合化疗以及伊立替康单药化疗。结果全组可评价疗效者13例,有效率（RR）为46.2%,疾病控制率（DCR）为76.9%,中位疾病进展时间（TTP）4.0个月。一线治疗6例,RR为66.7%,DCR为83.3%,中位TTP 4.8个月。13例有8例为结直肠癌,RR为50%,DCR为87.5%,中位TTP 5.0个月,其中一线治疗3例全部获得PR。痤疮样皮疹发生率为52.9%,但未显示出皮疹与有效率的相关性。结论西妥昔单抗联合化疗治疗消化系统肿瘤安全有效,尤其一线治疗效果更佳,值得进一步扩大样本研究。     

Anti-epidermal growth factor receptor strategies to enhance radiation action

The epidermal growth factor receptor (EGFR) has emerged as a central molecular target for modulation in cancer therapeutics, since EGFR signaling affects many factors that in turn promote tumor growth, progression and metastasis. In addition, radiobiological investigations have also defined a critical role for EGFR in mediating cytoprotective and pro-proliferative responses in human cancer cells after ionizing radiation, that contribute at least in part to accelerated tumor cell repopulation. This led to the additional development of EGFR as a target to enhance radiation efficacy. Several anti-EGFR strategies have been put forth demonstrating a favorable biological interaction between EGFR blockade and radiation. However, further preclinical investigations are necessary to better explore mechanisms of action and efficacy of combined treatment modalities. Although some of the anti-EGFR approaches have already reached clinical testing in combination with radiation, it is still too early to establish a clinical proof for the ultimate role of EGFR inhibition in combination with radiation. This article focuses primarily on anti-EGFR approaches to modulate radiation response.     

Orthogonal threading-through-β-sheet design of lung cancer EGFR extracellular domain-derived peptidic mimotopes binding to anti-EGFR antibody

Human epidermal growth factor receptor (EGFR) has been established as a therapeutic target of lung cancer and other diverse tumors. The antibody drug Cetuximab has been developed to target the third subdomain III (TSDIII) of EGFR extracellular domain (ECD) by competitively inhibiting epidermal growth factor binding. In this study, we performed systematic investigation on the crystal complex structure of EGFR ECD domain with Cetuximab to create a residue importance profile for the TSDIII subdomain, based on which a number of U-shaped, double-stranded linear peptides were derived and cyclized to orthogonally thread through most hotspot residues and many responsible residues within the TSDIII β-sheet plane; they represent mimotopes of the key antibody-recognition site of TSDIII subdomain. Computational analyses revealed that these linear peptides cannot spontaneously fold to the desired conformation in free state due to their intrinsic flexibility. Cell-free assays confirmed that the stapling can considerably improve the binding affinity of linear peptides to Cetuximab by up to 18-fold. The cOrt1 [3–18] cyclic peptide was measured to have the highest affinity in all designed linear and cyclic peptides.     

Phase II study of combination chemotherapy with biweekly cetuximab and irinotecan for wild-type KRAS metastatic colorectal cancer refractory to irinotecan, oxaliplatin, and fluoropyrimidines

The aim of this study is to prospectively evaluate the efficacy of combination chemotherapy with every second week cetuximab and irinotecan in patients with pretreated metastatic colorectal cancer harboring wild-type KRAS. Patients with wild-type KRAS metastatic colorectal cancer that had progressed after chemotherapy with irinotecan, oxaliplatin, and fluoropyrimidine were included. Cetuximab was administered at 500 mg/m(2) biweekly with irinotecan. The primary endpoint was response rate. The pharmacokinetics of cetuximab was also evaluated in 5 patients. From May 2009 to February 2010, a total of 31 patients were enrolled from five institutions. One patient was not eligible. Among the 30 patients who were treated with biweekly cetuximab plus irinotecan, partial response was observed in 9 patients. The objective response rate was 30.0% (95% confidence interval [CI], 14.7%-49.4%) and the disease control rate (complete response, partial response, or stable disease) was 76.7% (95% CI, 57.7%-90.0%). The median progression-free survival was 5.3 months and median overall survival was 10.8 months. Grade 3 skin toxicity was observed in 3 patients (10.0%) and one treatment related death due to pneumonia was observed. Combination chemotherapy with biweekly cetuximab and irinotecan was effective for pretreated metastatic colorectal cancer with wild-type KRAS.