Dual inhibition of the epidermal growth factor receptor with cetuximab, an IgG1 monoclonal antibody, and gefitinib, a tyrosine kinase inhibitor, in patients with refractory non-small cell lung cancer (NSCLC): a phase I study

"Sandwich" Strategy to Intensify EGFR Blockade by Concurrent Tyrosine Kinase Inhibitor and Monoclonal Antibody Treatment in Highly Selected Patients

EGFR TKIs are not curative, and targeted resistance inevitably results in therapeutic failure. Additionally, there are numerous uncommon EGFR mutations that are insensitive to EGFR TKIs, and there is a lack of clinical strategies to overcome these limitations. EGFR TKI and mAbs target EGFR at different sites, and a combination regimen for delaying/preventing resistance to targeted therapy or obtaining more intensive inhibition for uncommon mutations at cellular, animal and human levels has been explored. This review critically focuses on a combination strategy for uncommon EGFR mutation-positive NSCLC, and discuss the preclinical data, clinical implications, limitations and future prospects of the combination strategy.

The Right Partner in Crime: Unlocking the Potential of the Anti-EGFR Antibody Cetuximab via Combination With Natural Killer Cell Chartering Immunotherapeutic Strategies

Cetuximab has an established role in the treatment of patients with recurrent/metastatic colorectal cancer and head and neck squamous cell cancer (HNSCC). However, the long-term effectiveness of cetuximab has been limited by the development of acquired resistance, leading to tumor relapse. By contrast, immunotherapies can elicit long-term tumor regression, but the overall response rates are much more limited. In addition to epidermal growth factor (EGFR) inhibition, cetuximab can activate natural killer (NK) cells to induce antibody-dependent cellular cytotoxicity (ADCC). In view of the above, there is an unmet need for the majority of patients that are treated with both monotherapy cetuximab and immunotherapy. Accumulated evidence from (pre-)clinical studies suggests that targeted therapies can have synergistic antitumor effects through combination with immunotherapy. However, further optimizations, aimed towards illuminating the multifaceted interplay, are required to avoid toxicity and to achieve better therapeutic effectiveness. The current review summarizes existing (pre-)clinical evidence to provide a rationale supporting the use of combined cetuximab and immunotherapy approaches in patients with different types of cancer.

Structure-function analysis of oncogenic EGFR Kinase Domain Duplication reveals insights into activation and a potential approach for therapeutic targeting

Mechanistic understanding of oncogenic variants facilitates the development and optimization of treatment strategies. We recently identified in-frame, tandem duplication of EGFR exons 18 - 25, which causes EGFR Kinase Domain Duplication (EGFR-KDD). Here, we characterize the prevalence of ERBB family KDDs across multiple human cancers and evaluate the functional biochemistry of EGFR-KDD as it relates to pathogenesis and potential therapeutic intervention. We provide computational and experimental evidence that EGFR-KDD functions by forming asymmetric EGF-independent intra-molecular and EGF-dependent inter-molecular dimers. Time-resolved fluorescence microscopy and co-immunoprecipitation reveals EGFR-KDD can form ligand-dependent inter-molecular homo- and hetero-dimers/multimers. Furthermore, we show that inhibition of EGFR-KDD activity is maximally achieved by blocking both intra- and inter-molecular dimerization. Collectively, our findings define a previously unrecognized model of EGFR dimerization, providing important insights for the understanding of EGFR activation mechanisms and informing personalized treatment of patients with tumors harboring EGFR-KDD. Finally, we establish ERBB KDDs as recurrent oncogenic events in multiple cancers.

An EGFR mutant with kinase domain duplication (EGFR-KDD) was previously identified in an index patient, but the functional and therapeutic implications remain unclear. Here, the authors show that KDD occurs in other ErbB receptors in multiple cancers, and characterize the mechanism and inhibition of EGFR-KDD.

Antitumor Activity of Amivantamab (JNJ-61186372), an EGFR-MET Bispecific Antibody, in Diverse Models of EGFR Exon 20 Insertion-Driven NSCLC

EGFR exon 20 insertion driver mutations (Exon20ins) in non-small cell lung cancer (NSCLC) are insensitive to EGFR tyrosine kinase inhibitors (TKI). Amivantamab (JNJ-61186372), a bispecific antibody targeting EGFR-MET, has shown preclinical activity in TKI-sensitive EGFR-mutated NSCLC models and in an ongoing first-in-human study in patients with advanced NSCLC. However, the activity of amivantamab in Exon20ins-driven tumors has not yet been described. Ba/F3 cells and patient-derived cells/organoids/xenograft models harboring diverse Exon20ins were used to characterize the antitumor mechanism of amivantamab. Amivantamab inhibited proliferation by effectively downmodulating EGFR-MET levels and inducing immune-directed antitumor activity with increased IFNγ secretion in various models. Importantly, in vivo efficacy of amivantamab was superior to cetuximab or poziotinib, an experimental Exon20ins-targeted TKI. Amivantamab produced robust tumor responses in two Exon20ins patients, highlighting the important translational nature of this preclinical work. These findings provide mechanistic insight into the activity of amivantamab and support its continued clinical development in Exon20ins patients, an area of high unmet medical need. SIGNIFICANCE: Currently, there are no approved targeted therapies for EGFR Exon20ins-driven NSCLC. Preclinical data shown here, together with promising clinical activity in an ongoing phase I study, strongly support further clinical investigation of amivantamab in EGFR Exon20ins-driven NSCLC.This article is highlighted in the In This Issue feature, p. 1079.

A phase 1b study of afatinib in combination with standard-dose cetuximab in patients with advanced solid tumours

This phase 1b, open-label trial assessed the combination of afatinib, an ErbB family blocker, with cetuximab, an epidermal growth factor receptor (EGFR) monoclonal antibody, in heavily pretreated patients with unselected/EGFR wild-type, advanced solid tumours. In Part A, the maximum tolerated dose (MTD) of afatinib + cetuximab was evaluated using a 3 + 3 dose-escalation design; the starting dose was afatinib 30 mg/day plus cetuximab 250 mg/m²/week (after cetuximab 400 mg/m² loading dose), escalating to afatinib 40 mg/day. Part B further evaluated safety and tolerability at the MTD and preliminary anti-tumour activity in three patient cohorts with squamous non-small cell lung cancer (NSCLC), head and neck squamous cell carcinoma (HNSCC) and other solid tumours. Nine patients were treated in Part A; the MTD and recommended dose was determined as afatinib 40 mg/day plus cetuximab 250 mg/m²/week. In Part B, 49 patients were treated at the recommended dose (12 with squamous NSCLC, 15 with HNSCC and 22 with other tumours). The most common treatment-related adverse events (AEs) across all 58 patients were diarrhoea (63.8%) and acneiform dermatitis (43.1%). Overall, the best confirmed response was stable disease (SD; 53.4%); mean duration of disease control was 4.5 months; median progression-free survival was 2.6 months. In Part B, 55.1% of patients had SD (squamous NSCLC, 75.0%; HNSCC, 66.7%; other tumours; 36.4%). In conclusion, the recommended phase 2 dose was determined as afatinib 40 mg/day plus cetuximab 250 mg/m²/week. AEs were predictable and manageable, and anti-tumour activity was observed in some patients, particularly in those with squamous NSCLC and HNSCC. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov NCT02020577.

Epidermal growth factor receptor peptide vaccination induces cross-reactive immunity to human EGFR, HER2, and HER3

Current treatments for tumors expressing epidermal growth factor receptor (EGFR) include anti-EGFR monoclonal antibodies, often used in conjunction with the standard chemotherapy, radiation therapy, or other EGFR inhibitors. While monoclonal antibody treatment is efficacious in many patients, drawbacks include its high cost of treatment and side effects associated with multiple drug infusions. As an alternative to monoclonal antibody treatments, we have focused on peptide-based vaccination to trigger natural anti-tumor antibodies. Here, we demonstrate that peptides based on a region of the EGFR extracellular domain IV break immune tolerance to EGFR and elicit anti-tumor immunity. Mice immunized with isoforms of EGFR peptide p580-598 generated anti-EGFR antibody and T-cell responses. Iso-aspartyl (iso-Asp)-modified EGFR p580 immune sera inhibit in vitro growth of EGFR overexpressing human A431 tumor cells, as well as promote antibody-dependent cell-mediated cytotoxicity (ADCC). Antibodies induced by Asp and iso-Asp p580 bound homologous regions of the EGFR family members HER2 and HER3. EGFR p580 immune sera also inhibited the growth of the human tumor cell line MDA-MB-453 that expresses HER2 but not EGFR. Asp and iso-Asp EGFR p580 induced antibodies were also able to inhibit the in vivo growth of EGFR-expressing tumors. These data demonstrate that EGFR peptides from a region of the EGFR extracellular domain IV promote anti-tumor immunity, tumor cell killing, and antibodies that are cross reactive with ErbB family members.

Combination Strategies Using EGFR-TKi in NSCLC Therapy: Learning from the Gap between Pre-Clinical Results and Clinical Outcomes

Although epidermal growth factor receptor (EGFR) inhibitors have been used to treat non-small cell lung cancer (NSCLC) for decades with great success in patients with EGFR mutations, acquired resistance inevitably occurs after long-term exposure. More recently, combination therapy has emerged as a promising strategy to overcome this issue. Several experiments have been carried out to evaluate the synergism of combination therapy both in vitro and in vivo. Additionally, many clinical studies have been carried out to investigate the feasibility of treatment with EGFR-tyrosine kinase inhibitors (TKi) combined with other NSCLC treatments, including radiotherapy, cytotoxic chemotherapies, targeted therapies, and emerging immunotherapies. However, a significant gap still exists when applying pre-clinical results to clinical scenarios, which hinders the development and use of these strategies. This article is a literature review analysing the rationalities and controversies in the transition from pre-clinical investigation to clinical practice associated with various combination strategies. It also highlights clues and challenges regarding future combination therapeutic options in NSCLC treatment.

The resistance mechanisms and treatment strategies for EGFR-mutant advanced non-small-cell lung cancer

Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKI) have been established as the standard therapy for EGFR-sensitizing mutant advanced non-small-cell lung cancer (NSCLC). However, patients ultimately develop resistance to these drugs. There are several mechanisms of both primary and secondary resistance to EGFR-TKIs. The primary resistance mechanisms include point mutations in exon 18, deletions or insertions in exon 19, insertions, duplications and point mutations in exon 20 and point mutation in exon 21 of EGFR gene. Secondary resistance to EGFR-TKIs is due to emergence of T790M mutation, activation of alternative signaling pathways, bypassing downstream signaling pathways and histological transformation. Strategies to overcome these intrinsic and acquired resistance mechanisms are complex. With the development of the precision medicine for advanced NSCLC, available systemic and local treatment options have expanded, requiring new clinical algorithms that take into account resistance mechanism. Though combination therapy is emerging as the standard of to overcome resistance mechanisms. Personalized treatment modalities based on molecular diagnosis and monitoring is essential for disease management. Emerging data from the ongoing clinical trials on combination therapy of third generation TKIs and antibodies in EGFR mutant NSCLC are promising for better survival outcomes.

Molecular Targeting of Growth Factor Receptor Signaling in Radiation Oncology

Ionizing radiation has been shown to activate and interact with multiple growth factor receptor pathways that can influence tumor response to therapy. Among these receptor interactions, the epidermal growth factor receptor (EGFR) has been the most extensively studied with mature clinical applications during the last decade. The combination of radiation and EGFR-targeting agents using either monoclonal antibody (mAb) or small-molecule tyrosine kinase inhibitor (TKI) offers a promising approach to improve tumor control compared to radiation alone. Several underlying mechanisms have been identified that contribute to improved anti-tumor capacity after combined treatment. These include effects on cell cycle distribution, apoptosis, tumor cell repopulation, DNA damage/repair, and impact on tumor vasculature. However, as with virtually all cancer drugs, patients who initially respond to EGFR-targeted agents may eventually develop resistance and manifest cancer progression. Several potential mechanisms of resistance have been identified including mutations in EGFR and downstream signaling molecules, and activation of alternative member-bound tyrosine kinase receptors that bypass the inhibition of EGFR signaling. Several strategies to overcome the resistance are currently being explored in preclinical and clinical models, including agents that target the EGFR T790 M resistance mutation or target multiple EGFR family members, as well as agents that target other receptor tyrosine kinase and downstream signaling sites. In this chapter, we focus primarily on the interaction of radiation with anti-EGFR therapies to summarize this promising approach and highlight newly developing opportunities.

Afatinib-based combination regimens for the treatment of solid tumors: rationale, emerging strategies and recent progress

In oncology, there is a clinical need for novel combination therapy regimens that maximize efficacy and delay resistance to individual treatment modalities. Given the role of aberrant ErbB receptor signaling in the pathogenesis of many human cancers, there is rationale for incorporating afatinib, an irreversible pan-ErbB tyrosine kinase inhibitor, into such combinations. This review focuses on: pharmacological properties of afatinib that facilitate its use in combination; preclinical rationale for the combination of afatinib with other agents; and recently completed, and ongoing, clinical trials of afatinib-based combinations across tumor types. Based on these data, we emphasize a number of areas of high unmet medical need that could benefit from afatinib-based combinations, including patients with relapsed/refractory non-small-cell lung cancer.

A phase 1 study of cetuximab and lapatinib in patients with advanced solid tumor malignancies

BACKGROUND

Acquired resistance to antiepidermal growth factor receptor (anti-EGFR) therapy may be caused by EGFR-v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 2 (ErbB2) heterodimerization and pathway reactivation. In preclinical studies, inhibiting ErbB2 blocked this resistance mechanism and resensitized cells to anti-EGFR therapy. Cetuximab targets EGFR, whereas lapatinib inhibits both EGFR and ErbB2. The objective of this phase 1 trial was to assess the safety, dose-limiting toxicities (DLTs), and maximum tolerated doses (MTDs) of cetuximab and lapatinib in patients with solid tumors.

METHODS

Patients received standard weekly cetuximab with escalating lapatinib doses of 750 mg, 1000 mg, or 1250 mg daily in 3-week cycles. DLTs were monitored through the end of cycle 2. Pretreatment and post-treatment tumor biopsies and germline DNA samples were obtained for correlative studies.

RESULTS

Twenty-two patients were enrolled, and 18 patients each were evaluable for toxicity and response. Fifty-nine percent of patients had received prior anti-EGFR therapy. Common toxicities included rash and diarrhea. No patient experienced a DLT at the highest dose level, and no grade 4 toxicity was observed. Response included no complete responses, 3 partial responses, 9 patients with stable disease, and 6 patients with disease progression, for an overall response rate of 17% and a clinical benefit rate of 67%. The clinical benefit rate in patients who had previously received anti-EGFR therapy was 70%. The mean treatment duration was 4.7 cycles (range, 1-14 cycles). Decreased expression of EGFR/ErbB2 pathway components after treatment was correlated with response, whereas increased expression in the PI3K, Jak/Stat, and MAPK pathways occurred in nonresponders.

CONCLUSIONS

The combination of cetuximab and lapatinib was well tolerated, had the expected toxicities, and exhibited notable clinical activity, including in patients who had received previous anti-EGFR therapy. Further clinical study of this combination is warranted.

Phase II study of afatinib, an irreversible ErbB family blocker, in demographically and genotypically defined lung adenocarcinoma

OBJECTIVES

Afatinib, an oral irreversible ErbB family blocker, has demonstrated efficacy in patients with epidermal growth factor receptor (EGFR) mutation-positive advanced lung adenocarcinoma. Other potential biomarkers predicting response to afatinib, such as human epidermal growth factor receptor-2 (HER2) mutations and EGFR gene amplification, have not been validated yet. This phase II study investigated whether afatinib conferred clinical benefit in cohorts of adenocarcinoma patients with: (1) EGFR mutation and failing on erlotinib/gefitinib; or (2) increased copy number of EGFR by fluorescence in situ hybridization (FISH); or (3) HER2 mutation.

MATERIALS AND METHODS

Patients started daily afatinib 50mg monotherapy. Upon disease progression, patients could continue, at the investigator's discretion, afatinib (40mg) with the addition of paclitaxel (80mg/m(2) weekly for 3 weeks/4-week cycle). Endpoints included confirmed objective response (OR), progression-free survival (PFS), disease control, and safety.

RESULTS

Of 41 patients treated (cohort 1: n=32; cohort 2: n=2; cohort 3: n=7), 33 received afatinib monotherapy; eight subsequently received afatinib plus paclitaxel. With afatinib monotherapy, one patient achieved a confirmed OR (partial response [PR]; cohort 2). Two further patients achieved unconfirmed PRs (one each in cohort 1 and cohort 3). Disease control was achieved by 17/32 (53%), 2/2 (100%) and 5/7 (71%) patients in cohorts 1, 2 and 3, respectively. In patients receiving combination therapy (median PFS: 6.7 weeks), one (cohort 3) had confirmed PR of 41.9 weeks. The most common afatinib-related adverse events were diarrhea (95%) and rash/acne (80%).

CONCLUSION

Afatinib demonstrated signs of clinical activity in heavily pretreated patients with activating HER2 or EGFR mutations or EGFR FISH-positive tumors.

Trials to Overcome Drug Resistance to EGFR and ALK Targeted Therapies - Past, Present, and Future

Molecularly targeted agents are changing the therapeutic landscape in advanced non-small cell lung cancer. Since the discovery of sensitizing mutations in the epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK) domain, clinical investigations have focused on optimizing the efficacy of EGFR and ALK tyrosine kinase inhibitors by addressing therapeutic resistance that commonly develops within a year of treatment initiation. Here, we review the clinical trials of novel therapies and combination regimens that have been undertaken in response to our evolving understanding of the mechanisms of resistance to targeted therapy. The aim of these trials was to enhance the therapeutic efficacy of targeted therapies by improving blockade and/or inhibiting parallel or compensatory signaling pathways. We have documented the sequential conduct of EGFR and ALK biomarker-driven trials in order to highlight particular pitfalls and successes, which should be considered in the design of future trials. Although there remain significant challenges, substantial gains have been made in our understanding of cellular resistance. This knowledge will drive the design of future trials to the benefit of lung cancer patients.

Dual inhibition of EGFR with afatinib and cetuximab in kinase inhibitor-resistant EGFR-mutant lung cancer with and without T790M mutations

EGFR-mutant lung cancers responsive to reversible EGFR inhibitors (gefitinib/erlotinib) develop acquired resistance, mediated by second-site EGFR T790M mutation in >50% of cases. Preclinically, afatinib (irreversible ErbB family blocker) plus cetuximab (anti-EGFR monoclonal antibody) overcomes T790M-mediated resistance. This phase Ib study combining afatinib and cetuximab enrolled heavily pretreated patients with advanced EGFR-mutant lung cancer and acquired resistance to erlotinib/gefitinib. Patients provided post-acquired-resistance tumor samples for profiling EGFR mutations. Among 126 patients, objective response rate (overall 29%) was comparable in T790M-positive and T790M-negative tumors (32% vs. 25%; P = 0.341). Median progression-free survival was 4.7 months (95% confidence interval, 4.3-6.4), and the median duration of confirmed objective response was 5.7 months (range, 1.8-24.4). Therapy-related grade 3/4 adverse events occurred in 44%/2% of patients. Afatinib-cetuximab demonstrated robust clinical activity and a manageable safety profile in EGFR-mutant lung cancers with acquired resistance to gefitinib or erlotinib, both with and without T790M mutations, warranting further investigation.

SIGNIFICANCE

This article reports the results of a trial combining afatinib and cetuximab in patients with acquired resistance and details the first clinical proof-of-concept for the preclinical hypothesis that a significant proportion of tumors in patients with acquired resistance to gefitinib/erlotinib remain dependent on EGFR signaling for survival.

Alternative signaling pathways as potential therapeutic targets for overcoming EGFR and c-Met inhibitor resistance in non-small cell lung cancer

The use of tyrosine kinase inhibitors (TKIs) against EGFR/c-Met in non-small cell lung cancer (NSCLC) has been shown to be effective in increasing patient progression free survival (PFS), but their efficacy is limited due to the development of resistance and tumor recurrence. Therefore, understanding the molecular mechanisms underlying development of drug resistance in NSCLC is necessary for developing novel and effective therapeutic approaches to improve patient outcome. This study aims to understand the mechanism of EGFR/c-Met tyrosine kinase inhibitor (TKI) resistance in NSCLC. H2170 and H358 cell lines were made resistant to SU11274, a c-Met inhibitor, and erlotinib, an EGFR inhibitor, through step-wise increases in TKI exposure. The IC₅₀ concentrations of resistant lines exhibited a 4–5 and 11–22-fold increase for SU11274 and erlotinib, respectively, when compared to parental lines. Furthermore, mTOR and Wnt signaling was studied in both cell lines to determine their roles in mediating TKI resistance. We observed a 2–4-fold upregulation of mTOR signaling proteins and a 2- to 8-fold upregulation of Wnt signaling proteins in H2170 erlotinib and SU11274 resistant cells. H2170 and H358 cells were further treated with the mTOR inhibitor everolimus and the Wnt inhibitor XAV939. H358 resistant cells were inhibited by 95% by a triple combination of everolimus, erlotinib and SU11274 in comparison to 34% by a double combination of these drugs. Parental H2170 cells displayed no sensitivity to XAV939, while resistant cells were significantly inhibited (39%) by XAV939 as a single agent, as well as in combination with SU11274 and erlotinib. Similar results were obtained with H358 resistant cells. This study suggests a novel molecular mechanism of drug resistance in lung cancer.

Targeting the ERBB family in cancer: couples therapy

The ERBB family of receptor tyrosine kinases has a central role in the tumorigenesis of many types of solid tumour. Various therapeutics targeting these receptors have been approved for the treatment of several cancers. Considerable preclinical data have shown that the administration of two inhibitors against an individual ERBB family member--particularly epidermal growth factor receptor (EGFR) or ERBB2--leads to markedly higher antitumour activity than the administration of single agents. This Opinion article describes the preclinical and clinical performance of these dual-targeting approaches, discusses the key mechanisms that mediate their increased efficacy and highlights areas for ongoing investigation.

Dual EGFR inhibition in combination with anti-VEGF treatment: a phase I clinical trial in non-small cell lung cancer

BACKGROUND

Preclinical data indicate EGFR signals through both kinase-dependent and independent pathways and that combining a small-molecule EGFR inhibitor, EGFR antibody, and/or anti-angiogenic agent is synergistic in animal models.

METHODS

We conducted a dose-escalation, phase I study combining erlotinib, cetuximab, and bevacizumab. The subset of patients with non-small cell lung cancer (NSCLC) was analyzed for safety and response.

RESULTS

Thirty-four patients with NSCLC (median four prior therapies) received treatment on a range of dose levels. The most common treatment-related grade ≥2 adverse events were rash (n=14, 41%), hypomagnesemia (n=9, 27%), and fatigue (n=5, 15%). Seven patients (21%) achieved stable disease (SD) ≥6 months, two achieved a partial response (PR) (6%), and two achieved an unconfirmed partial response (uPR) (6%) (total=32%). We observed SD≥6 months/PR/uPR in patients who had received prior erlotinib and/or bevacizumab, those with brain metastases, smokers, and patients treated at lower dose levels. Five of 16 patients (31%) with wild-type EGFR experienced SD≥6 months or uPR. Correlation between grade of rash and rate of SD≥6 months/PR was observed (p less than 0.01).

CONCLUSION

The combination of erlotinib, cetuximab, and bevacizumab was well-tolerated and demonstrated antitumor activity in heavily pretreated patients with NSCLC.

Combining erlotinib and cetuximab is associated with activity in patients with non-small cell lung cancer (including squamous cell carcinomas) and wild-type EGFR or resistant mutations

Preclinical data suggest that combined EGF receptor (EGFR) targeting with an EGFR tyrosine kinase inhibitor and an anti-EGFR monoclonal antibody may be superior over single-agent targeting. Therefore, as part of a phase I study, we analyzed the outcome of 20 patients with non-small cell lung cancer treated with the combination of erlotinib and cetuximab. EGFR mutation status was ascertained in a Clinical Laboratory Improvement Amendment-approved laboratory. There were 10 men; median number of prior therapies was five. Overall, two of 20 patients (10%) achieved partial response (PR), one of whom had a TKI-resistant EGFR insertion in exon 20, time to treatment failure (TTF) = 24+ months, and the other patient had squamous cell histology (EGFR wild-type), TTF = 7.4 months. In addition, three of 20 patients (15%) achieved stable disease (SD) ≥6 six months (one of whom had wild-type EGFR and squamous cell histology, and two patients had an EGFR TKI-sensitive mutation, one of whom had failed prior erlotinib therapy). Combination therapy with ertotinib plus cetuximab was well tolerated. The most common toxicities were rash, diarrhea, and hypomagnesemia. The recommended phase II dose was erlotinib 150 mg oral daily and cetuximab 250 mg/m(2) i.v. weekly. In summary, erlotinib and cetuximab treatment was associated with SD ≥ six months/PR in five of 20 patients with non-small cell lung cancer (25%), including individuals with squamous histology, TKI-resistant EGFR mutations, and wild-type EGFR, and those who had progressed on prior erlotinib after an initial response. This combination warrants further study in select populations of non-small cell lung cancer.

Revisiting clinical trials using EGFR inhibitor-based regimens in patients with advanced non-small cell lung cancer: a retrospective analysis of an MD Anderson Cancer Center phase I population

PURPOSE

Single-agent EGFR inhibitor therapy is effective mainly in patients with lung cancer and EGFR mutations. Treating patients who develop resistance, or who are insensitive from the outset, often because of resistant mutations, other aberrations or the lack of an EGFR mutation, probably requires rational combinations. We therefore investigated the outcome of EGFR inhibitor-based combination regimens in patients with heavily-pretreated non-small cell lung cancer (NSCLC) referred to a Phase I Clinic.

METHODS

We reviewed the electronic records of patients with NSCLC treated with an EGFR inhibitor-based combination regimen: erlotinib and cetuximab; erlotinib, cetuximab and bevacizumab; erlotinib and dasatinib; erlotinib and bortezomib; or cetuximab and sirolimus.

RESULTS

EGFR mutations were detected in 16% of patients (21/131). EGFR inhibitor-based combination regimens were administered to 15 patients with EGFR-mutant NSCLC and 24 with EGFR wild-type disease. Stable disease (SD) ≥6 months/partial remission (PR) was attained in 20% of EGFR-mutant patients (3/15; two with sensitive mutations and secondary resistance to prior erlotinib, and one with a resistant mutation), as well as 26% of evaluable patients (5/19) with wild-type disease. One of three evaluable patients with squamous cell histology achieved SD for 26.5 months (EGFR wild-type, TP53-mutant, regimen=erlotinib, cetuximab and bevacizumab).

CONCLUSIONS

Eight of 34 evaluable patients (24%) with advanced, refractory NSCLC evaluable for response achieved SD ≥6 months/PR (PR=3; SD ≥6 months=5) on EGFR inhibitor-based combination regimens (erlotinib, cetuximab; erlotinib, cetuximab and bevacizumab; and, erlotinib, bortezomib), including patients with secondary resistance to single-agent EGFR inhibitors, resistant mutations, wild-type disease, and, squamous histology.

A kinase-independent biological activity for insulin growth factor-1 receptor (IGF-1R) : implications for inhibition of the IGF-1R signal

It has been demonstrated that epidermal growth factor receptor (EGFR) can have kinase independent activity. EGFR kinase-independent function maintains intracellular glucose levels via sodium glucose transporter protein 1 (SGLT1) and supports cell survival. It is plausible that this phenomenon can apply to other receptor tyrosine kinases. We found that transfection of insulin-like growth factor receptor (IGF-1R) siRNA into HEK293 (human embryonic kidney) and MCF7 (metastatic breast cancer) cells result in decreased intracellular glucose levels, whereas treatment with an IGF-1R tyrosine kinase inhibitor OSI-906 did not affect intracellular glucose levels. In addition, IGF-1R interacted with SGLT1 in a manner similar to that previously reported with EGFR. The combination of IGF-1R siRNA and OSI-906 resulted in decreased viability of HEK293 and MCF7 cell lines compared to either agent alone. Collectively, these experiments suggest that IGF-1R, has kinase-independent biologic functions and provide a rationale for combining anti-IGF-1R antibodies or siRNA and IGF-1R small molecule inhibitors.

Safety and feasibility of targeted agent combinations in solid tumours

The plethora of novel molecular-targeted agents (MTAs) has provided an opportunity to selectively target pathways involved in carcinogenesis and tumour progression. Combination strategies of MTAs are being used to inhibit multiple aberrant pathways in the hope of optimizing antitumour efficacy and to prevent development of resistance. While the selection of specific agents in a given combination has been based on biological considerations (including the role of the putative targets in cancer) and the interactions of the agents used in combination, there has been little exploration of the possible enhanced toxicity of combinations resulting from alterations in multiple signalling pathways in normal cell biology. Owing to the complex networks and crosstalk that govern normal and tumour cell proliferation, inhibiting multiple pathways with MTA combinations can result in unpredictable disturbances in normal physiology. This Review focuses on the main toxicities and the lack of tolerability of some common MTA combinations, particularly where evidence of enhanced toxicity compared to either agent alone is documented or there is development of unexpected toxicity. Toxicities caused by MTA combinations highlight the need to introduce new preclinical testing paradigms early in the drug development process for the assessment of chronic toxicities resulting from such combinations.

Cetuximab in non-small-cell lung cancer

Cetuximab is a chimeric human-mouse anti-EGF receptor monoclonal antibody. In Phase I studies, no dose-limiting toxicities were observed with cetuximab as a single agent or combined with chemotherapy; pharmacokinetic and pharmacodynamic analyses supported 250 mg/m(2) weekly administration. Skin toxicity, diarrhea and fatigue were the most common toxicities. The positive results obtained in Phase II trials in patients with advanced non-small-cell lung cancer prompted two randomized Phase III trials evaluating cetuximab in addition to first-line chemotherapy. Both trials showed a small benefit in overall survival for the experimental treatment, which was considered insufficient by the EMA for marketing approval. However, a subgroup analysis of the FLEX Phase III trial recently demonstrated a larger survival benefit from the experimental treatment in patients with high immunohistochemical EGF receptor expression. This finding, if confirmed prospectively, could represent a new opportunity for positioning cetuximab into the standard treatment of advanced non-small-cell lung carcinoma.

Mechanism of EGER-related cancer drug resistance

Drug resistance in cancer arises from a complex range of biochemical and molecular events, which ultimately result in tumor cell survival. Identifying key genes and signal pathways involved in the molecular mechanisms of drug resistance is essential for establishment of new drug targets for preventing further resistance development and spreading. Epidermal growth factor receptor (EGFR) was the first growth factor receptor proposed as a target for cancer therapy. Significant progress in studying EGFR gene expression and mutation has been made in understanding the molecular events involved in EGFR-targeted agents. Recently, some individual chromosomal features such as EGFR copy number variation were demonstrated as new aspects related to drug sensitivity. Identifying these functional regulators of drug resistance will benefit therapeutic decision-making. In this study, we describe an extensive investigation of the published literature on mutation, amplification, and expression of EGFR and its downstream signaling that directly contribute to EGFR inhibitor resistance, including the gene status of KRAS, BRAF, PIK3CA, PTEN, MEK, and AKT on response to therapy. Analysis of these gene signatures identified reveals general modes of action of multicomponent therapies and the mechanisms of specific drug combinations, highlights the potential value of molecular interaction profiles in the discovery of novel therapies, and provides more information for personalized cancer medicine.

Targeting the epidermal growth factor receptor in non-small cell lung cancer cells: the effect of combining RNA interference with tyrosine kinase inhibitors or cetuximab

BACKGROUND

The epidermal growth factor receptor (EGFR) is a validated therapeutic target in non-small cell lung cancer (NSCLC). However, current single agent receptor targeting does not achieve a maximal therapeutic effect, and some mutations confer resistance to current available agents. In the current study we have examined, in different NSCLC cell lines, the combined effect of RNA interference targeting the EGFR mRNA, and inactivation of EGFR signaling using different receptor tyrosine kinase inhibitors (TKIs) or a monoclonal antibody cetuximab.

METHODS

NSCLC cells (cell lines HCC827, H292, H358, H1650, and H1975) were transfected with EGFR siRNA and/or treated with the TKIs gefitinib, erlotinib, and afatinib, and/or with the monoclonal antibody cetuximab. The reduction of EGFR mRNA expression was measured by real-time quantitative RT-PCR. The down-regulation of EGFR protein expression was measured by western blot, and the proliferation, viability, caspase3/7 activity, and apoptotic morphology were monitored by spectrophotometry, fluorimetry, and fluorescence microscopy. The combined effect of EGFR siRNA and different drugs was evaluated using a combination index.

RESULTS

EGFR-specific siRNA strongly inhibited EGFR protein expression almost equally in all cell lines and inhibited cell growth and induced cell apoptosis in all NSCLC cell lines studied, albeit with a different magnitude. The effects on growth obtained with siRNA was strikingly different from the effects obtained with TKIs. The effects of siRNA probably correlate with the overall oncogenic significance of the receptor, which is only partly inhibited by the TKIs. The cells which showed weak response to TKIs, such as the H1975 cell line containing the T790M resistance mutation, were found to be responsive to siRNA knockdown of EGFR, as were cell lines with downstream TKI resistance mutations. The cell line HCC827, harboring an exon 19 deletion mutation, was more than 10-fold more sensitive to TKI proliferation inhibition and apoptosis induction than any of the other cell lines. Cetuximab alone had no relevant in vitro activity at concentrations obtainable in the clinic. The addition of EGFR siRNA to either TKIs or cetuximab additively enhanced growth inhibition and induction of apoptosis in all five cell lines, independent of the EGFR mutation status (wild-type or sensitizing mutation or resistant mutation). The strongest biological effect was observed when afatinib was combined with an EGFR-specific siRNA.

CONCLUSIONS

EGFR knockdown by siRNA further decreases the cell growth of lung cancer cells that are treated with TKIs or cetuximab alone, confirming that single agent drug targeting does not achieve a maximal biological effect. The siRNA inhibits EGFR oncogenic activity that bypasses downstream "resistance" mutations such as KRAS and PTEN. The combined treatment of siRNA and EGFR inhibitory agents is additive. The combination of a potent, irreversible kinase inhibitor such as afatinib, with EGFR-specific siRNAs should be further investigated as a new strategy in the treatment of lung cancer and other EGFR dependent cancers, including those with downstream resistance mutations.

Inhibition of STAT-3 results in greater cetuximab sensitivity in head and neck squamous cell carcinoma

OBJECTIVE

The inhibition of epidermal growth factor receptor (EGFr) with the monoclonal antibody cetuximab reduces cell proliferation and survival which correlates with increased DNA damage. Since the signal transducer and activator of transcription-3 (STAT-3) is involved in the EGFr-induced signaling pathway, we hypothesized that depletion of STAT-3 may augment cetuximab-induced processes in human head and neck cancer cells.

MATERIALS AND METHODS

Human head and neck squamous carcinoma cells (UM-SCC-5) were transfected with short hairpin RNA (shRNA) against STAT-3 (STAT3-2.4 and 2.9 cells). A mutated form of this shRNA was transfected for a control (NEG4.17 cells). Radiosensitivity was assessed by a standard colony formation assay. Proliferation was assessed by daily cell counts following treatment and apoptosis was assessed by an annexin V-FITC assay. The alkaline comet assay was used to assess DNA damage.

RESULTS

The STAT-3 knockdown cells (STAT3-2.4 and STAT3-2.9 cells) demonstrated enhanced radiosensitivity compared to control NEG4.17 cells, which correlated with increased apoptosis. Also, the STAT-3 knockdown cells demonstrated decreased proliferation with cetuximab treatments compared to control cells (NEG4.17). The increased cetuximab sensitivity of the STAT-3 knockdown cells correlated with increased apoptosis and DNA damage compared to control cells (NEG4.17).

CONCLUSION

These studies revealed that the greater anti-proliferative effects and increased cytotoxicity of cetuximab in the STAT3-2.4 and STAT3-2.9 cells compared to control NEG4.17 cells, may be a result of STAT3-mediated effects on cellular apoptosis and DNA damage.

Erlotinib or gefitinib for the treatment of relapsed platinum pretreated non-small cell lung cancer and ovarian cancer: a systematic review

BACKGROUND

Platinum-based chemotherapy is the standard of care for ovarian cancer and non-small cell lung cancer (NSCLC). However, resistance to platinum agents invariably develops. Targeted therapies, such as tyrosine kinase inhibitors (TKIs), have great potential here as they exert their anti-tumour effect via alternative mechanisms to platinum-based drugs and as such may remain unaffected by emergent resistance to platinum.

METHODS

A systematic review was conducted to investigate whether two EGFR-TKIs, erlotinib and gefitinib, have efficacy in the platinum-resistance setting. Preclinical studies of platinum-resistant cancer cell lines, which had been subsequently treated with EGFR-TKIs, were sought to establish proof-of-concept. Clinical trials reporting administration of EGFR-TKIs to ovarian cancer and NSCLC patients relapsed after therapy with platinum drugs were investigated to determine sensitivity of these cohorts to EGFR-TKI treatment. The role of EGFR mutation, copy number and protein expression on response to EGFR-TKIs after failure of platinum chemotherapy were also investigated.

RESULTS

Preclinical models of platinum-resistant cancer were found which display a spectrum of cross-resistance profiles to EGFR-TKIs. Sensitivity to EGFR-TKIs is dependent on the activation of the EGFR pathway or EGFR interacting proteins such as HER-2. EGFR-TKIs show favourable response rates in platinum-pretreated NSCLC, 11.14% and 15.25% for 150mg/day erlotinib and 250mg/day gefitinib, respectively. These response rates significantly improve in patients of Asian descent (28.3% and 29.17%, respectively) and patients with EGFR activation mutations (41.6% and 63.89%, respectively) or increased copy number (33.3% and 45.45%, respectively). Gefitinib significantly outperformed erlotinib and should therefore be the EGFR-TKI of choice in platinum-pretreated relapsed NSCLC. In contrast, response rates are very poor to both erlotinib and gefitinib in platinum pretreated ovarian cancer, 0-5.9% and they should not be used in this cohort of patients. Preclinical models demonstrate that, while cross resistance can occur between platinums and EGFR-TKIs, there is not a generalised cross-resistance phenotype. Erlotinib and gefitinib are suitable for the treatment of platinum-pretreated NSCLC, particularly in patients with EGFR mutations or increases in copy number. Unfortunately, the high rates of EGFR protein overexpression in ovarian cancer are not translating to a clinically useful therapeutic target for EGFR-TKIs; EGFR mutations are rare in ovarian cancer. Newer TKIs may improve response rates in these cohorts and future clinical trials need to collect tumour biopsies from all patients to ensure the success of personalised chemotherapy.

Cetuximab monotherapy in patients with advanced non-small cell lung cancer after prior epidermal growth factor receptor tyrosine kinase inhibitor therapy

INTRODUCTION

Therapeutic agents directed against the epidermal growth factor receptor (EGFR) signaling pathway have been effective in the treatment of non-small cell lung cancer (NSCLC). Cetuximab is a monoclonal antibody against the EGFR receptor with antitumor activity in NSCLC. This study evaluated the efficacy of cetuximab monotherapy after prior treatment with an oral EGFR tyrosine kinase inhibitor (TKI).

METHODS

Eligible patients had stage IIIB, IV, or recurrent NSCLC with progression on the oral EGFR TKIs gefitinib or erlotinib. Cetuximab was administered intravenously at 400 mg/m on day 1 and then 250 mg/m weekly until disease progression or unacceptable toxicity. The primary end point was response rate.

RESULTS

Eighteen patients were enrolled. Patients were heavily pretreated with chemotherapy and TKIs (average number of treatments = 4.2). The response rate was 0/18 (0%), and 28% of patients had confirmed stable disease. Median progression-free survival was 1.8 months (95% confidence interval, 1.6-5.4 months), and median overall survival was 7.5 months (95% confidence interval, 2.2-19 months). Three patients harbored activating EGFR mutations, and one of them had stable disease for nearly 6 months on cetuximab. Common toxicities were mild and included fatigue, skin rash, and nausea/vomiting. Two patients developed interstitial lung disease, life threatening in one case.

CONCLUSIONS

Cetuximab monotherapy administered after prior EGFR TKI treatment in patients with advanced NSCLC does not yield clinical responses.

Phase I/II trial of cetuximab and erlotinib in patients with lung adenocarcinoma and acquired resistance to erlotinib

PURPOSE

In patients with epidermal growth factor receptor (EGFR) mutant lung adenocarcinoma, treatment with erlotinib or gefitinib is associated with a 75% radiographic response rate and progression-free survival of approximately 12 months. The most common mechanism of acquired resistance to erlotinib is development of a secondary mutation in EGFR, suggesting that these tumors continue to depend on EGFR signaling. We hypothesized that combined EGFR blockade would overcome acquired resistance to erlotinib in patients with lung adenocarcinoma. To evaluate the toxicity and efficacy of cetuximab and erlotinib in patients with acquired resistance to erlotinib, we conducted this phase I/II clinical trial.

EXPERIMENTAL DESIGN

Patients with lung adenocarcinoma and clinically defined acquired resistance to erlotinib were treated with erlotinib 100 mg daily, along with cetuximab every 2 weeks in three escalating dose cohorts (250 mg/m(2), 375 mg/m(2), and 500 mg/m(2)). The recommended phase II dose was then evaluated in a two-stage trial, with a primary end point of objective response rate.

RESULTS

A total of 19 patients were enrolled. The most common toxicities for the combination of cetuximab and erlotinib were rash, fatigue, and hypomagnesemia. The recommended phase II dose identified was cetuximab 500 mg/m(2) every 2 weeks and erlotinib 100 mg daily. At this dose and schedule, no radiographic responses were seen (0 of 13, 0%, 95% CI, 0-25).

CONCLUSIONS

Combined EGFR inhibition, with cetuximab 500 mg/m(2) every 2 weeks and erlotinib 100 mg daily, had no significant activity in patients with acquired resistance to erlotinib.

抗表皮生长因子受体和抗血管内皮生长因子药物在非小细胞肺癌治疗中的作用

采用以铂类药物为基础联合细胞毒性药物作为非小细胞肺癌（non-small-cell lung cancer, NSCLC）的标准化一线治疗的疗效已达到相应的平台。作用于特定通路的新型分子靶向药物逐渐成为治疗NSCLC的有效药物；某些药物的Ⅲ期试验已取得阳性结果。值得注意的是，有研究证实，采用抗血管内皮生长因子（vascular endothelial growth factor, VEGF）抗体贝伐珠单抗抑制VEGF通路，以及采用表皮生长因子受体（epidermal growth factor receptor, EGFR）的小分子酪氨酸激酶抑制剂厄洛替尼或单克隆抗体（西妥昔单抗）靶向作用于EGFR通路作为一线或二线治疗方案，均可延长晚期肺癌患者的生存期。可导致肿瘤细胞存活和增殖的信号处理过程不同，为靶向作用于多种信号通路为有效的抗癌治疗策略提供了依据。因此，分子靶向药物的合理联用可能达到更好的临床疗效，并可成为对标准化疗耐药或不能耐受标准化疗的患者的可替代的治疗选择。目前的挑战在于明确应探寻哪些分子实体，以及它们的最佳联合方案。本综述旨在探讨贝伐珠单抗联合厄洛替尼抑制血管生成和EGFR信号作为治疗NSCLC的有效的非化疗方案的潜在临床疗效。其它可阻滞EGFR和血管生成通路以及互补信号通路的新型药物的联合具有独特的作用机制和较轻的毒副作用，有可能为晚期NSCLC患者的个体化治疗选择提供更多的治疗方案。

Targeted therapies for non-small cell lung cancer: an evolving landscape

Over the past decade, a multitude of targeted agents have been explored in the treatment of advanced non-small cell lung cancer (NSCLC). Thus far, two broad classes of agents have been implemented in clinical practice: (a) vascular endothelial growth factor (VEGF)-directed therapies and (b) antagonists of the epidermal growth factor receptor (EGFR). In the former category, the agent bevacizumab (a monoclonal antibody) has shown landmark improvements in survival when added to cytotoxic therapy. Small molecule tyrosine kinase inhibitors (TKI) targeting the VEGF receptor (i.e., sunitinib, sorafenib, and vandetanib) show activity in phase II clinical studies. With respect to EGFR-directed therapies, the TKIs gefitinib and erlotinib have shown significant benefit, and have uncovered valuable information about the biology of lung cancer. Outside of therapies directed specifically at VEGF- and EGFR-mediated signaling, trials evaluating insulin-like growth factor-1 receptor (IGF-IR)-targeting agents, cyclooxygenase-2 (COX-2) inhibitors, c-met inhibitors, irreversible pan-HER inhibitors, mammalian target of rapamycin (mTOR) inhibitors, and histone deacetylase (HDAC) inhibitors are ongoing. Inhibitors of ALK show great promise in patients with the relevant gene translocation. Herein, the clinical development of novel therapies for NSCLC is described, including some discussion of relevant biomarkers and determination of synergy with both cytotoxic therapy and other targeted agents.

The role of anti-epidermal growth factor receptor and anti-vascular endothelial growth factor therapies in the treatment of non-small-cell lung cancer

Standard first-line therapy for non-small-cell lung cancer (NSCLC) with platinum-based agents, given in combination with cytotoxic compounds, has reached a relative plateau in its therapeutic efficacy. Novel molecular targeted agents acting on specific pathways have emerged as effective agents for treating NSCLC; some have already produced positive results in phase III trials. Notably, inhibition of the vascular endothelial growth factor (VEGF) pathway with an anti-VEGF antibody, bevacizumab, and targeting the epidermal growth factor receptor (EGFR) pathway with a small-molecule EGFR tyrosine kinase inhibitor erlotinib or a monoclonal antibody (cetuximab) have demonstrated prolonged survival in patients with advanced disease in both the first- and second-line settings. The heterogeneity of signaling processes leading to tumor cell survival and proliferation supports the targeting of multiple signaling pathways as an effective anticancer treatment strategy. Consequently, rational combinations of molecular targeted agents might offer superior clinical efficacy and an alternative treatment option to patients refractory to, or unable to tolerate, standard chemotherapy. The challenge lies in determining which molecular entities should be pursued and the best approach to combine them. This review discusses the potential clinical utility of combining bevacizumab and erlotinib to inhibit both angiogenesis and EGFR signaling as a valid nonchemotherapeutic approach for the treatment of NSCLC. Other combinations of novel therapies that block EGFR and angiogenic pathways, as well as complementary signaling pathways, with unique modes of action and low toxicity profiles could offer an increased repertoire of individualized treatment options for patients with advanced NSCLC.

Monoclonal antibodies: versatile platforms for cancer immunotherapy

Antibodies are important therapeutic agents for cancer. Recently, it has become clear that antibodies possess several clinically relevant mechanisms of action. Many clinically useful antibodies can manipulate tumour-related signalling. In addition, antibodies exhibit various immunomodulatory properties and, by directly activating or inhibiting molecules of the immune system, antibodies can promote the induction of antitumour immune responses. These immunomodulatory properties can form the basis for new cancer treatment strategies.

Combining targeted therapies: practical issues to consider at the bench and bedside

Numerous practical issues must be considered when combining targeted therapies in early clinical drug development. These include tumor resistance mechanisms, the existence of multiple, redundant signaling pathways, and the failure of single-agent therapies to achieve cures. The strategies adopted to examine combinatorial therapy include the goal of hitting more than one target by specifically inhibiting signal transduction cascades and suppressing specific mechanisms of action with the use of multitargeted kinase inhibitors made possible by high-throughput screening techniques, combinatorial chemistry, and chemoinformatics. Two complex considerations are: which agents to combine given the heterogeneity of tumors and their various underlying perturbations, including secondary mutations and feedback loops, and how to translate findings from the bench to the bedside or directly from the bedside. Another consideration is: When is there enough information to provide a rationale for instituting a phase I trial? Various strategies have been used in combining molecules, including targeting diverse pathways, inhibiting upstream and downstream signals, and adopting a synthetic lethality paradigm. Other issues are: determining appropriate target populations for treatment, how to combine therapeutics with diagnostics, and the frequency of targets in patients referred to clinical trials. Here, we review these issues and we propose various novel trial designs that are logical for determining the efficacy of a drug or drug combination for personalized treatment. A difficult issue that must be answered is how many and which drugs to combine. Recent technologies, such as multiplexed assay platforms and bioinformatics, will shape the future of clinical trials and help answer these questions surrounding combinatorial treatment.

The role of cetuximab in the management of non-small-cell lung cancer

Inhibition of the epidermal growth factor receptor (EGFR) pathway has emerged as a proven strategy for the treatment of advanced-stage non-small-cell lung cancer (NSCLC). Cetuximab is a chimeric monoclonal antibody that inhibits EGFR by binding to the extracellular domain of the receptor. The relatively modest anticancer activity as monotherapy in NSCLC has prompted the evaluation of cetuximab as part of novel combination regimens. The safety of cetuximab in combination with the commonly used platinum-based 2-drug regimens in NSCLC has been established in several phase II studies. Recently, the addition of cetuximab to the regimen of cisplatin and vinorelbine resulted in improved overall survival in patients with advanced NSCLC with EGFR-expressing tumors. In contrast, a study in unselected advanced NSCLC patients failed to demonstrate a statistically significant improvement in overall survival with cetuximab in combination with a carboplatin and taxane regimen. It is hoped that identification of predictive biomarkers would lead to the optimal utilization of cetuximab in combination with chemotherapy. The combination of cetuximab with radiotherapy for patients with locally advanced NSCLC has demonstrated promising results in a phase II study and is now being evaluated in a confirmatory trial. This article reviews the clinical data with cetuximab in NSCLC.

Targeting the epidermal growth factor receptor in epithelial ovarian cancer: current knowledge and future challenges

The epidermal growth factor receptor is overexpressed in up to 60% of ovarian epithelial malignancies. EGFR regulates complex cellular events due to the large number of ligands, dimerization partners, and diverse signaling pathways engaged. In ovarian cancer, EGFR activation is associated with increased malignant tumor phenotype and poorer patient outcome. However, unlike some other EGFR-positive solid tumors, treatment of ovarian tumors with anti-EGFR agents has induced minimal response. While the amount of information regarding EGFR-mediated signaling is considerable, current data provides little insight for the lack of efficacy of anti-EGFR agents in ovarian cancer. More comprehensive, systematic, and well-defined approaches are needed to dissect the roles that EGFR plays in the complex signaling processes in ovarian cancer as well as to identify biomarkers that can accurately predict sensitivity toward EGFR-targeted therapeutic agents. This new knowledge could facilitate the development of rational combinatorial therapies to sensitize tumor cells toward EGFR-targeted therapies.

The role of EGFR inhibition in the treatment of non-small cell lung cancer

The identification of certain molecular mechanisms underlying lung carcinogenesis and progression has led to the development of targeted agents against different families of growth factors and receptors. The epidermal growth factor receptor (EGFR) is one such target for therapeutic exploitation. Inhibition of EGFR downstream signaling can be accomplished through two primary mechanisms: (a) the direct blocking of intracellular kinase activity with small-molecule tyrosine kinase inhibitors (TKIs) (e.g., gefitinib, erlotinib) and (b) the blocking of EGFR ligand binding using antibodies directed against the extracellular domain of the receptor (e.g., cetuximab). Resistance to available EGFR-targeted treatments has emerged as a substantial clinical issue in non-small cell lung cancer (NSCLC). Several novel agents with the potential to overcome such resistance are currently in clinical development, including irreversible EGFR TKIs, monoclonal antibodies, and TKIs directed against multiple signaling pathways. Here we discuss the clinical application of the currently available EGFR-targeted agents in NSCLC, the underlying mechanisms of resistance, and the novel agents in clinical development that may overcome resistance.

Cetuximab and other anti-epidermal growth factor receptor monoclonal antibodies in the treatment of non-small cell lung cancer

Non-small cell lung cancer (NSCLC) accounts for about 85% of all new diagnoses of lung cancer. Unfortunately, few NSCLC patients are suitable for radical treatment for curative intent. Because most patients with NSCLC have advanced disease at diagnosis, chemotherapy represents the standard of care, although, to date, a plateau has been reached with this approach. Improvements in the knowledge of tumor biology and mechanisms of oncogenesis have identified the epidermal growth factor receptor (EGFR), a member of the ErbB family, as a molecular target for NSCLC treatment. EGFR is commonly overexpressed in NSCLC and has been associated with impaired prognosis; therefore, its inhibition may lead, through the suppression of tumor proliferation, to improvement in clinical outcomes. Strategies to block EGFR include tyrosine kinase inhibitors, monoclonal antibodies, ligand-linked toxins, and antisense approaches. This article focuses on the treatment of NSCLC with the anti-EGFR monoclonal antibodies, including cetuximab, for which the largest amount of data in the literature exists. Recently, a phase III randomized trial performed in advanced NSCLC patients yielded a statistically significant survival advantage for patients treated with cetuximab plus chemotherapy versus chemotherapy alone. Other anti-EGFR monoclonal antibodies, such as panitumumab, matuzumab, nimotuzumab, and ch806, are in different stages of development for the treatment of advanced NSCLC.

Mechanisms of tumor resistance to EGFR-targeted therapies

BACKGROUND

Much effort has been devoted to development of cancer therapies targeting EGFR, based on its role in regulating cell growth. Small-molecule and antibody EGFR inhibitors have clinical roles based on their efficacy in a subset of cancers, generally as components of combination therapies. Many cancers are either initially resistant to EGFR inhibitors or become resistant during treatment, limiting the efficacy of these reagents.

OBJECTIVE/METHODS

To review cellular resistance mechanisms to EGFR-targeted therapies.

RESULTS/CONCLUSIONS

The best validated of these mechanisms include activation of classic ATP-binding casette (ABC) multidrug transporters; activation or mutation of EGFR; and overexpression or activation of signaling proteins operating in relation to EGFR. We discuss current efforts and potential strategies to override these sources of resistance. We describe emerging systems-biology-based concepts of alternative resistance to EGFR-targeted therapies, and discuss their implications for use of EGFR-targeted and other targeted therapies.