Cetuximab, a chimeric human mouse anti-epidermal growth factor receptor monoclonal antibody, in the treatment of human colorectal cancer

Panitumumab monotherapy in patients with metastatic colorectal cancer and cetuximab infusion reactions: a series of four case reports

PURPOSE

Monoclonal antibodies against the epidermal growth factor receptor approved for treating metastatic colorectal cancer (mCRC) include cetuximab (a chimeric antibody) and panitumumab (a fully human antibody). Because these antibodies have differences in protein sequence, patients intolerant to one antibody might still tolerate the other. Four cases are presented from a US panitumumab compassionate-use program in which patients with mCRC who were intolerant to cetuximab received panitumumab.

PATIENTS AND METHODS

Eligible patients had failed previous fluoropyrimidine therapy with oxaliplatin- and irinotecan-containing chemotherapy, had cetuximab intolerance (ie, experienced an infusion reaction), and were unable to participate in a panitumumab clinical trial. For each patient, individual Federal Drug Administration-approved single-patient treatment use Investigational New Drug- and Institutional Review Board-approved protocols were used, informed consent was obtained, and data were collected independently by the investigator.

RESULTS

All 4 patients (2 men, 2 women) had received previous bevacizumab and premedications before cetuximab administration. In response to cetuximab, all 4 patients experienced Common Terminology Criteria for Adverse Events grade 3 or grade 4 infusion-reaction symptoms, which required acute therapy. Time from cetuximab discontinuation to panitumumab administration ranged from 8 days to 5 months. Panitumumab monotherapy was administered at approximately 6 mg/kg every 2 weeks. Two patients received premedications before panitumumab use. No physician reported any infusion reaction to panitumumab. One patient had stable disease, and 3 patients had disease progression.

CONCLUSION

Though this small case series provides evidence that patients with mCRC intolerant to cetuximab can receive subsequent panitumumab monotherapy without experiencing infusion reactions, additional clinical testing is needed to definitively examine this finding.

EGFR-targeted therapies in lung cancer: predictors of response and toxicity

The EGFR pathway has emerged as a key target in non-small-cell lung cancer. EGF receptor (EGFR) inhibition in non-small-cell lung cancer is achieved via small molecular tyrosine kinase inhibitors, such as erlotinib or gefitinib, or monoclonal antibodies such as cetuximab. A growing body of evidence is identifying potential molecular predictors of response and toxicity. This includes tumor-related molecular markers, such as EGFR mutation and copy number, as well as germline markers such as polymorphisms in EGFR or EGFR pathway-related genes. This review focuses on the current state of knowledge of predictors of response and toxicity to EGFR inhibitors in lung cancer.

Engineering therapeutic monoclonal antibodies

During last two decades, the chimerization and humanization of monoclonal antibodies (mAbs) have led to the approval of several for the treatment of cancer, autoimmune diseases, and transplant rejection. Additional approaches have been used to further improve their in vivo activity. These include combining them with other modalities such as chemotherapy and redesigning them for improved pharmacokinetics, effector function, and signaling activity. The latter has taken advantage of new insights emerging from an increased understanding of the cellular and molecular mechanisms that are involved in the interaction of immunoglobulin G with Fc receptors and complement as well as the negative signaling resulting from the hypercrosslinking of their target antigens. Hence, mAbs have been redesigned to include mutations in their Fc portions, thereby endowing them with enhanced or decreased effector functions and more desirable pharmacokinetic properties. Their valency has been increased to decrease their dissociation rate from cells and enhance their ability to induce apoptosis and cell cycle arrest. In this review we discuss these redesigned mAbs and current data concerning their evaluation both in vitro and in vivo.

Cetuximab: preclinical evaluation of a monoclonal antibody targeting EGFR for radioimmunodiagnostic and radioimmunotherapeutic applications

The monoclonal antibody, cetuximab, binds to epidermal growth-factor receptor and thus provides an opportunity to create both imaging and therapies that target this receptor. The potential of cetuximab as a radioimmunoconjugate, using the acyclic bifunctional chelator, CHX-A"-DTPA, was investigated. The pharmacokinetic behavior in the blood was determined in mice with and without tumors. Tumor targeting and scintigraphic imaging were evaluated in mice bearing xenografts of LS-174T (colorectal), SHAW (pancreatic), SKOV3 (ovarian), DU145 (prostate), and HT-29 (colorectal). Excellent tumor targeting was observed in each of the models with peak tumor uptakes of 59.8 +/- 18.1, 22.5 +/- 4.7, 33.3 +/- 5.7, 18.2 +/- 7.8, and 41.7 +/- 10.8 injected dose per gram (%ID/g) at 48-72 hours, respectively. In contrast, the highest tumor %ID/g obtained in mice bearing melanoma (A375) xenografts was 6.3 +/- 1.1 at 72 hours. The biodistribution of (111)In-cetuximab was also evaluated in nontumor-bearing mice. The highest %ID/g was observed in the liver (9.3 +/- 1.3 at 24 hours) and the salivary glands (8.1 +/- 2.8 at 72 hours). Scintigraphy showed excellent tumor targeting at 24 hours. Blood pool was evident, as expected, but cleared over time. At 168 hours, the tumor was clearly discernible with negligible background.

Binding of rituximab, trastuzumab, cetuximab, or mAb T101 to cancer cells promotes trogocytosis mediated by THP-1 cells and monocytes

More than 20 years ago clinical investigations in the immunotherapy of cancer revealed that infusion of certain immunotherapeutic mAbs directed to tumor cells induced loss of targeted epitopes. This phenomenon, called antigenic modulation, can compromise mAb-based therapies. Recently we reported that rituximab (RTX) treatment of chronic lymphocytic leukemia patients induced substantial loss of targeted CD20 on B cells found in the circulation after RTX infusion; this "shaving" of RTX-CD20 complexes from B cells is also promoted in vitro by THP-1 monocytes and by PBMC in a reaction mediated by Fcgamma receptors. The mechanism responsible for shaving appears to be trogocytosis, a process in which receptors on effector cells remove and internalize cognate ligands and cell membrane fragments from target cells. We now report that three therapeutic mAbs approved by the U.S. Food and Drug Administration for the treatment of cancer, RTX, cetuximab, and trastuzumab, as well as mAb T101, which has been shown to induce antigenic modulation in the clinic, promote trogocytosis in vitro upon binding to their respective target cells. Trogocytosis of the mAb-opsonized cells is mediated by THP-1 monocytes and by primary monocytes isolated from PBMC. In view of these results, it is likely that these mAbs and possibly other anticancer mAbs now used in the clinic may promote trogocytic removal of the therapeutic mAbs and their cognate Ags from tumor cells in vivo. Our findings may have important implications with respect to the use of mAbs in cancer immunotherapy.

Molecular targeted therapy of digestive system neoplasms

Malignancies in digestive system (MIDS) are most common and they are major causes of tumor death in the world. Despite recent advances, patients with MIDS still have very poor prognosis. With the development of tumor molecular biology, especially clarification of the mechanism underlying molecular signaling pathway for tumor cell proliferation and growth, researchers have started a new field and direction of clinical tumor therapy, i.e., molecular targeted therapy, which was essentially effective in tumor treatment. This article elucidates the current status, latest advances and developing trends of molecular targeted therapy for MIDS.

Recombinant antibodies for cancer therapy

BACKGROUND

Recombinant antibodies have evolved into successful therapeutics with 10 approved for cancer and more in the pipeline. Four of the top ten cancer therapy drugs are recombinant antibodies.

OBJECTIVES

To survey the current state-of-the-art highlighting the reasons for this success and looking ahead to the next generation of antibody therapy.

METHODS

An analysis was carried out to identify preclinical and clinical examples and the underlying concepts and mechanisms that have shown how to design better therapies.

RESULTS/CONCLUSIONS

Greater understanding of the molecular basis of cancer has led to improved antibodies and a greater selection of targets. Fine tuning of successful antibodies through modification of glycosylation, affinity, size and other parameters are paying dividends. Fc-engineering is likely to be predominant in the near future but conjugates, fragments and fusion proteins will continue to be developed and find their place in the arsenal of antibody therapeutics.

Interleukin-2 potentiation of cetuximab antitumor activity for epidermal growth factor receptor-overexpressing gastric cancer xenografts through antibody-dependent cellular cytotoxicity

Cetuximab, a chimeric monoclonal antibody to epidermal growth factor receptor (EGFR), has been proved to have clinically significant antitumor activity against advanced colorectal cancers, but its therapeutic activity for gastric cancers remains unclear. In the present study, we investigated the antitumor effect and action mechanism of cetuximab using EGFR high-expressing (MKN-28) and EGFR low-expressing (GLM-1) gastric cancer cell lines without gene amplification. Cetuximab showed neither significant growth inhibition nor induction of apoptosis in either cell line in vitro, and only slightly inhibited ligand-induced phosphorylation of protein kinase B and extracellular signal-regulated kinase in MKN-28 cells. In contrast, cetuximab significantly inhibited subcutaneous and intraperitoneal tumor growth of MKN-28 cells, but not GLM-1 cells, in nude mice. This antitumor activity was significantly enhanced and diminished in nude mice by treatment with interleukin-2 (IL-2) and antiasialo GM1 antibody, which can expand and deplete natural killer (NK) cells, respectively. Antibody-dependent cellular cytotoxicity (ADCC) of cetuximab, as measured by (51)Cr release assay, was significantly higher in MKN-28 than in GLM-1 cells. This ADCC activity was enhanced by IL-2 and reduced by heat-aggregate of human immunoglobulin G, an inhibitor for FcR-III of NK cells. These results suggest that cetuximab in combination with IL-2 shows significant antitumor activity against EGFR high-expressing gastric cancer mainly through NK cell-mediated ADCC. Combination therapy with cetuximab and IL-2 would thus offer a new potential therapeutic approach for a subset of EGFR-overexpressing gastric cancers.

Paul Ehrlich's magic bullet concept: 100 years of progress

Exceptional advances in molecular biology and genetic research have expedited cancer drug development tremendously. The declared paradigm is the development of 'personalized and tailored drugs' that precisely target the specific molecular defects of a cancer patient. It is therefore appropriate to revisit the intellectual foundations of the development of such agents, as many have shown great clinical success. One hundred years ago, Paul Ehrlich, the founder of chemotherapy, received the Nobel Prize for Physiology or Medicine. His postulate of creating 'magic bullets' for use in the fight against human diseases inspired generations of scientists to devise powerful molecular cancer therapeutics.

Inhibition of JAK1, 2/STAT3 signaling induces apoptosis, cell cycle arrest, and reduces tumor cell invasion in colorectal cancer cells

Abnormalities in the STAT3 pathway are involved in the oncogenesis of several cancers. However, the mechanism by which dysregulated STAT3 signaling contributes to the progression of human colorectal cancer (CRC) has not been elucidated, nor has the role of JAK, the physiological activator of STAT3, been evaluated. To investigate the role of both JAK and STAT3 in CRC progression, we inhibited JAK with AG490 and depleted STAT3 with a SiRNA. Our results demonstrate that STAT3 and both JAK1 and 2 are involved in CRC cell growth, survival, invasion, and migration through regulation of gene expression, such as Bcl-2, p1(6ink4a), p21(waf1/cip1), p27(kip1), E-cadherin, VEGF, and MMPs. Importantly, the FAK is not required for STAT3-mediated regulation, but does function downstream of JAK. In addition, our data show that proteasome-mediated proteolysis promotes dephosphorylation of the JAK2, and consequently, negatively regulates STAT3 signaling in CRC. Moreover, immunohistochemical staining reveals that nuclear staining of phospho-STAT3 mostly presents in adenomas and adenocarcinomas, and a positive correlation is found between phospho-JAK2 immunoreactivity and the differentiation of colorectal adenocarcinomas. Therefore, our findings illustrate the biologic significance of JAK1, 2/STAT3 signaling in CRC progression and provide novel evidence that the JAK/STAT3 pathway may be a new potential target for therapy of CRC.

ErbB receptors, their ligands, and the consequences of their activation and inhibition in the myocardium

The epidermal growth factor (EGF) receptor (or ErbB1) and the related ErbB4 are transmembrane receptor protein tyrosine kinases which bind extracellular ligands of the EGF family. ErbB2 and ErbB3 are "co-receptors" structurally related to ErbB1/ErbB4, but ErbB2 is an "orphan" receptor and ErbB3 lacks tyrosine kinase activity. However, both are important in transmembrane signalling. All ErbB receptors/ligands are intimately involved in the regulation of cell growth, differentiation and survival, and their dysregulation contributes to some human malignancies. After extracellular ligand binding, receptor dimerisation and transautophosphorylation of intracellular C-terminal tyrosine residues, they bind signalling proteins which recognise specific tyrosine-phosphorylated motifs. This leads to activation of multiple signalling pathways, notably the extracellular signal-regulated kinase 1/2 (ERK1/2) cascade and the phosphoinositide 3-kinase (PI3K)/protein kinase B [PKB/(Akt)] pathway. In heart, targeted deletion of ErbB2, ErbB3, ErbB4 and some ErbB receptor extracellular ligands leads to embryonic lethality resulting from cardiovascular defects. ErbB receptor ligands improve cardiac myocyte viability and are hypertrophic, partly because of activation of ERK1/2 and/or PI3K/PKB(Akt). Furthermore, ErbB transactivation by Gq protein-coupled receptor (GqPCR) signalling may mediate the hypertrophic effects of GqPCR agonists. The utility of anthracyclines in cancer chemotherapy can be limited by their cardiotoxic side effects and these may be counteracted by ErbB receptor ligands. ErbB2 is the target of anti-cancer monoclonal antibody trastuzumab (Herceptin), and its myocardial downregulation may account for the occasional cardiotoxicity of this therapy. Here, we review the basic biochemistry of ErbB receptors/ligands, and emphasise their particular roles in the myocardium.

Current status of antivascular therapy and targeted treatment in the clinic

Antivascular and targeted therapy are now an integrated part of the treatment of myelogenous leukemias, GIST tumours, B-cell lymphomas and breast cancer. In various malignancies improved responses and prolongation of survival for several months is regularly reported. The progress in this field is relevant for hyperthermia. Heat has among other effects documented antivascular effects, and can be considered as one of the established methods in the field based on several randomised phase III studies. Hyperthermia should be considered for combination with other antiangiogenic agents.

Challenges and prospects of immunotherapy as cancer treatment

The concept of cancer immunotherapy stems from the proposed function of the immune system, called immunosurveillance, to protect against growing tumors. Due to genetic aberrations, tumor cells display an altered repertoire of MHC-associated peptides that can lead to the activation of immune cells able to eliminate the transformed cells. In some instances, under the pressure of the immune system, both the tumor and its microenvironment are shaped and immune-resistant tumor variants are selected initiating the process of cancer immunoediting. This can impair not only host-generated immunosurveillance, but also attempts to harness the immune response for therapeutic purposes, namely immunotherapy. Rather than being an exhaustive review of the different approaches of cancer immunotherapy, the focus of this review is to provide the reader with future challenges of the field by proposing 'second generation' immunotherapy approaches that take into account immunosubversive mechanisms adopted by tumor cells. After an introduction on the process of immunosurveillance and immunoescape we will analyze why current immunotherapy approaches have not fulfilled their promise and will finish by summarizing what are the challenges for future approaches.