Monoclonal Antibodies Panitumumab Research Articles

In vivo photoacoustic imaging of cancer using indocyanine green-labeled monoclonal antibody targeting the epidermal growth factor receptor

Photoacoustic (PA) imaging is an attractive imaging modality for sensitive and depth imaging of biomolecules with high resolution in vivo. The aim of this study was to evaluate the effectiveness of an anti-epidermal growth factor receptor (EGFR) monoclonal antibody (panitumumab; Pan) labeled with indocyanine green derivative (ICG-EG4-Sulfo-OSu), Pan-EG4-ICG, as a PA imaging probe to target cancer-associated EGFR. In vitro PA imaging studies demonstrated that Pan-EG4-ICG yielded high EGFR-specific PA signals in EGFR-positive cells. To determine the optimal injection dose and scan timing, we investigated the biodistribution of radiolabeled Pan-EG4-ICG (200–400 μg) in A431 tumor (EGFR++)-bearing mice. The highest tumor accumulation (29.4% injected dose/g) and high tumor-to-blood ratio (2.1) was observed 7 days after injection of Pan-EG4-ICG (400 μg). In in vivo PA imaging studies using Pan-EG4-ICG (400 μg), the increase in PA signal (114%) was observed in A431 tumors inoculated in the mammary glands 7 days post-injection. Co-injection of excess Pan resulted in a 35% inhibition of this PA signal, indicating the EGFR-specific accumulation. In conclusion, the ICG-labeled monoclonal antibody (i.e., panitumumab) has the potential to enhance target-specific PA signal, leading to the discrimination of aggressiveness and metastatic potential of tumors and the selection of effective therapeutic strategies.

Extended RAS analysis for anti-epidermal growth factor therapy in patients with metastatic colorectal cancer.

RAS family proteins (including KRAS and NRAS) play important roles in the epidermal growth factor receptor (EGFR) signaling pathway. Mutations in RAS genes (occurring at loci in exons 2, 3, and 4) often result in constitutive activation of RAS proteins and persistent downstream signaling. Mutations in KRAS exon 2 (codon 12/13) are an established predictor of lack of response to the anti-EGFR monoclonal antibodies cetuximab and panitumumab in patients with metastatic colorectal cancer (mCRC), and have been used routinely in clinical practice to identify patients unlikely to derive benefit from these therapies. However, a meaningful proportion of patients with mCRC have tumors bearing other mutations in RAS genes. Recent studies have demonstrated that evaluation of an extended panel of RAS mutations—including mutations in KRAS exon 2, 3, and 4 and NRAS exons 2, 3, and 4—can better define the patient population that is unlikely to benefit from anti-EGFR therapy, with concomitant improvements in outcomes in the more highly selected RAS wild-type group. This discovery has changed the practice of oncology and has the potential to spare patients from exposure to ineffective therapy. In the near future, it is important for the oncology community to validate extended RAS analysis assays and make certain that patients who are candidates for anti-EGFR therapy undergo appropriate testing and treatment.

Pharmacogenomics of intrinsic and acquired pharmacoresistance in colorectal cancer: Toward targeted personalized therapy

Colorectal cancer (CRC) represents one of the most common malignancies and is major cause of cancer-related deaths worldwide. A great improvement in response rate and patient's survival was recently achieved through the introduction of new targeted agents including the anti-EGFR monoclonal antibodies cetuximab and panitumumab, the anti-angiogenic drugs bevacizumab and aflibercept, as well as the multi-kinase inhibitor regorafenib, in combination with standard fluoropyrimidines-based chemotherapeutic regimens. Intrinsic and acquired chemoresistance continue to be a major hindrance toward curative therapy. To overcome the obstacle of the currently unpredictable inter-individual variability in the therapy outcome, concentrated research efforts have been focused on elucidating the contribution of genetic variants predictive of pharmacoresistance in CRC. The occurrence of tumor somatic mutations in the RAS/RAF/MAPK and PI3K/PTEN/AKT pathways remains the main challenge for CRC treatment with the new biological agents. It has been recently proposed to consider a quadruple negative profile for CRC, based on the status of KRAS exon 2, BRAF-p.V600E, PI3KCA-exon 9 and PTEN, as tumor markers of sensitivity to anti-EGFR treatment. However, in the last years, great efforts have been devoted to address germline genetic profiles of pharmacoresistance. Heritable genetic variants in the ABC and SLC transport pathways; in the CYP450, GST, and UGT-mediated phase I and II metabolism; in the folate metabolic pathway; as well as in the EGF and VEGF signaling pathways, have been associated with a distinct tumor sensitivity phenotype in CRC patients treated with fluoropyrimidines combined with either irinotecan, oxaliplatin or targeted biological agents. More recently, computation of clinical-pharmacogenetic algorithms, combining multiple host polymorphisms with clinico-demographic features, appeared to be a more reliable strategy to test a complex phenomenon as tumor response to therapy. The final goal of the pharmacogenomics research in the domain of pharmacoresistance in CRC should be the definition of integrated somatic and germline genetic profiles of both intrinsic and acquired resistance. The aim of the present review is to provide a comprehensive update on the most important findings regarding the research of pharmacogenomics markers in the field of CRC treatment that could be integrated in clinical practice in order to accomplish an efficacious personalized treatment.

Circulating tumor cells as a longitudinal biomarker in patients with advanced chemorefractory, RAS-BRAF wild-type colorectal cancer receiving cetuximab or panitumumab.

A still relevant number of patients with RAS-BRAF wild-type colorectal cancer (CRC) do not respond to treatment with antiepidermal growth factor receptor (EGFR) monoclonal antibodies cetuximab and panitumumab, suggesting that additional biomarkers to guide patient selection are urgently needed. Circulating tumor cells (CTCs) may represent such a biomarker. In this prospective study, 38 patients with advanced RAS-BRAF-wild-type CRC received third-line therapy with cetuximab-irinotecan or panitumumab. Peripheral blood samples for CTC status determination were collected at baseline, during treatment at early (2-4 weeks) and at later (8-10 weeks) times. CTC enrichment was done with the AdnaTest ColonCancerSelect kit, whereas CTC detection was done with the AdnaTest ColonCancerDetect kit. CTC status positivity was defined according to the kit manufacturer's thresholds. Fifty percent of patients were defined as CTC positive at baseline and the overall RECIST response rate was 26%. CTC baseline status was not associated with treatment response, whereas early CTC status and CTC status changes during treatment were significantly associated with tumor response. Kaplan-Meier analysis showed a significantly shorter progression-free survival (median, 2.0 versus 4.0 months, p = 0.004) and overall survival (4.7 versus11.4, p = 0.039) in patients with early CTC + status compared with CTC - ones. In multivariable analysis including classical prognostic factors, the CTC status changes profile during treatment was an independent predictor of both progression-free survival (p < 0.001) and overall-survival (p = 0.001). CTC status assessed early during treatment with anti-EGFR monoclonal antibodies may predict treatment failure in advance compared to imaging-based tools.

Targeting EGFR in Metastatic Colorectal Cancer Beyond the Limitations of KRAS Status: Alternative Biomarkers and Therapeutic Strategies

Patients with metastatic colorectal cancer have a very poor prognosis. Incorporation of targeted molecular therapies, such as the anti-EGFR receptor monoclonal antibodies cetuximab and panitumumab, into treatment regimens has improved outcomes for patients with wild-type RAS tumors. Yet, response rates remain low and overall survival times are short. Increased understanding of oncogenic signaling pathways within the tumor, and how these are regulated by the inflammatory tumor microenvironment, is a priority to facilitate the development of biomarkers to better guide the use of existing therapies and to develop new ones. Here, we review recent preclinical and clinical progress in the development of biomarkers for predicting response to anti-EGFR therapy in metastatic colorectal cancer.

Irreversible multitargeted ErbB family inhibitors for therapy of lung and breast cancer.

Overactivation of the ErbB protein family, which is comprised of 4 receptor tyrosine kinase members (ErbB1/epidermal growth factor receptor [EGFR]/HER1, ErbB2/HER2, ErbB3/HER3, and ErbB4/HER4), can drive the development and progression of a wide variety of malignancies, including colorectal, head and neck, and certain non-small cell lung cancers (NSCLCs). As a result, agents that target a specific member of the ErbB family have been developed for the treatment of cancer. These agents include the reversible EGFR tyrosine kinase inhibitors (TKIs) erlotinib and gefitinib; the EGFR-targeting monoclonal antibodies cetuximab and panitumumab; and the HER2-targeting monoclonal antibody trastuzumab. Lapatinib is a dual TKI that targets both EGFR and HER2. In addition, TKIs that inhibit multiple members of the ErbB family and also bind their targets irreversibly are under evaluation for the treatment of cancer. Three such compounds have progressed into clinical studies: the EGFR, HER2, and HER4 inhibitors afatinib, dacomitinib, and neratinib. Phase I studies of these agents have shown clinical activity in NSCLC, breast cancer, and other malignancies. Currently, afatinib is approved for EGFR mutation-positive NSCLC and is in development for squamous NSCLC, and dacomitinib is in phase III of clinical development for NSCLC, neratinib is in phase III of clinical development for the treatment of breast cancer, and afatinib is also in phase III development in head and neck cancer. Final results from clinical trials may lead to the potential approval of these agents in a variety of solid tumor malignancies.

Abstract 1843: Primary and acquired resistance to HERs inhibition in colorectal cancer cells: All HERs go to RAS

Abstract The monoclonal antibodies cetuximab and panitumumab are approved for the treatment of metastatic colorectal cancers (mCRC). When used as monotherapy, the anti-EGFR antibodies are effective in approximately 15% of patients. It is now well established that colorectal tumors carrying KRAS and BRAF mutations (40%) are refractory to EGFR targeted therapies (primary resistance). Virtually all-responsive patients eventually become insensitive to anti-EGFR antibodies (secondary resistance) within 3 to 12 months of initiating therapy. Primary and acquired resistance therefore limits the clinical benefit of EGFR blockade in CRC patients. We postulated that concomitant inhibition of multiple members of the HER (ErbB) receptors family might suppress the growth of CRC cells more effectively than selectively targeting only the EGFR with cetuximab or panitumumab. Accordingly, we assessed the pharmacological activity of momelotinib and afatinib- two pan-HER tyrosine kinase inhibitors- in a collection of 40 CRC cell lines, which recapitulate the genetic profiles commonly detected in CRC patients. We report that primary resistance to pan-HER inhibition is associated with KRAS and BRAF mutations thus suggesting that this patients' population will unlikely benefit from momelotinib and afatinib treatments. Notably, however, pan-HER blockade was effective in a subset of KRAS/BRAF wild type CRC cell lines refractory to cetuximab and panitumumab indicating that a subgroup of patients, which do not benefit from EGFR blockade, may profit from pan-HER inhibition. To define the molecular mechanisms of acquired resistance to ErbB inhibitors, three KRAS/BRAF/NRAS wild type CRC cell models were continuously treated with cetuximab, momelotinib and afatinib, until resistant derivatives emerged. Genetic characterization of such derivatives unveiled that, regardless of the drug used, the resistant populations were a mixture of clones carrying distinctive mutations in KRAS or NRAS. Detailed biochemical analyses of the ErbB signalling pathway revealed that resistant variants displayed high levels of MEK and ERK activation, which persisted upon ErbBs inhibition. Collectively, these results identify KRAS, BRAF and NRAS mutations as major drivers of primary and/or acquired resistance to HERs inhibition in colorectal cancer cells and suggest that a molecularly defined subset of CRC patients might benefit from pan-HER blockade. Citation Format: Mariangela Russo, Alessandra Riggio, Carlotta Cancelliere, Federica Di Nicolantonio, Alberto Bardelli. Primary and acquired resistance to HERs inhibition in colorectal cancer cells: All HERs go to RAS. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1843. doi:10.1158/1538-7445.AM2014-1843

Infectious complications in cancer patients treated with anti-EGFR monoclonal antibodies cetuximab and panitumumab: a systematic review and meta-analysis.

Clinical trials have reported a substantial variation in the risk of infection related to anti-EGFR monoclonal antibodies (mAbs) cetuximab and panitumumab. We performed a systematic review and meta-analysis to assess the infection risk in cancer patients treated with anti-EGFR mAbs. We searched PubMed and the ASCO online database of meeting abstracts up to January 2014 for relevant clinical trials. Eligible studies included randomized controlled trials (RCTs) of cetuximab and panitumumab that reported adequate safety data for grade 3-4 infection or febrile neutropenia (FN). The summary incidence, relative risk (RR) and 95% confidence intervals (CIs) were calculated. A total of 14,957 patients from 28 trials were included. Treatment with anti-EGFR mAbs was associated with an increased risk of high-grade infection (RR, 1.49; 95% CI, 1.33-1.66; P<0.001) and FN (RR, 1.27; 95% CI, 1.09-1.48; P=0.002). The incidence of high-grade infection and FN due to anti-EGFR mAbs was 9.3% (95% CI, 7.2-12.0%) and 5.3% (95% CI, 3.3-8.3%), respectively. A significantly increased risk of high-grade infection was observed in all subgroups analyses (type of anti-EGFR mAb, therapy of control arm and duration of treatment) except for tumor type (only colorectal cancer and non-small cell lung cancer (NSCLC) groups had the increased risk). Subgroup analyses revealed a significantly increased risk of FN in the following subgroups: cetuximab, NSCLC and treatment duration longer than the median of all trials (3.1months). The use of anti-EGFR mAbs is associated with a significantly higher risk of high-grade infection and febrile neutropenia.

Adaptation of International Guidelines for Metastatic Colorectal Cancer: An Asian Consensus

Colorectal cancer (CRC) is among the most common cancers worldwide, but marked epidemiological differences exist between Asian and non-Asian populations. Hence, a consensus meeting was held in Hong Kong in December 2012 to develop Asia-specific guidelines for the management of metastatic CRC (mCRC). A multidisciplinary expert panel, consisting of 23 participants from 10 Asian and 2 European countries, discussed current guidelines for colon or rectal cancer and developed recommendations for adapting these guidelines to Asian clinical practice. Participants agreed that mCRC management in Asia largely follows international guidelines, but they proposed a number of recommendations based on regional ‘real-world’ experience. In general, participants agreed that 5-fluorouracil (5-FU) infusion regimens in doublets can be substituted with UFT (capecitabine, tegafur-uracil) and S1 (tegafur, 5-chloro-2,4-dihydroxypyridine and oxonic acid), and that the monoclonal antibodies cetuximab and panitumumab are recommended for KRAS wild type tumors. For KRAS mutant tumors, bevacizumab is the preferred biological therapy. FOLFOX (folinic acid, 5-FU, and oxaliplatin) is preferred for initial therapy in Asian patients. The management of mCRC is evolving, and it must be emphasized that the recommendations presented here reflect current treatment practices and thus might change as more data become available.

PD-0011 - Circulating Tumor Cells (CTCS) as Prognostic Biomarker in Patients with Advanced Chemorefractory, Ras Wild-Type Colorectal Cancer (CRC) Treated with Cetuximab or Panitumumab

Introduction: Anti-EGFR monoclonal antibodies (MoAb) cetuximab and panitumumab improved outcome of patients with advanced RAS wild-type CRC in combination with chemotherapy or in chemorefractory disease. Even in molecularly enriched populations, additional biomarkers to drive “negative” selection of patients are urgently needed to identify the relevant subset of non responders. CTCs may represent useful real time liquid biopsy. A meta-analysis demonstrated that CTCs+ CRC patients treated with chemotherapy have 2-fold increased risk of progressive disease (PD) and 2.5-fold increased risk of death.

Panitumumab versus cetuximab in patients with chemotherapy-refractory wild-type KRAS exon 2 metastatic colorectal cancer (ASPECCT): a randomised, multicentre, open-label, non-inferiority phase 3 study

The anti-EGFR monoclonal antibodies panitumumab and cetuximab are effective in patients with chemotherapy-refractory wild-type KRAS exon 2 metastatic colorectal cancer. We assessed the efficacy and toxicity of panitumumab versus cetuximab in these patients. For this randomised, open-label, phase 3 head-to-head study, we enrolled patients (from centres in North America, South America, Europe, Asia, Africa, and Australia) aged 18 years or older with chemotherapy-refractory metastatic colorectal cancer, an Eastern Cooperative Oncology Group (ECOG) performance status of 2 or less, and wild-type KRAS exon 2 status. Using a computer-generated randomisation sequence, we assigned patients (1:1; stratified by geographical region and ECOG performance status, with a permuted block method) to receive panitumumab (6 mg/kg once every 2 weeks) or cetuximab (initial dose 400 mg/m(2); 250 mg/m(2) once a week thereafter). The primary endpoint was overall survival assessed for non-inferiority (retention of ≥ 50% of the cetuximab treatment effect; historical hazard ratio [HR] for cetuximab plus best supportive care vs best supportive care alone of 0.55). The primary analysis included patients who received one or more dose of panitumumab or cetuximab, analysed per allocated treatment. Recruitment for this trial is closed. The trial is registered with ClinicalTrials.gov, number NCT01001377. Between Feb 2, 2010, and July 19, 2012, we enrolled and randomly allocated 1010 patients, 999 of whom began study treatment: 499 received panitumumab and 500 received cetuximab. For the primary analysis of overall survival, panitumumab was non-inferior to cetuximab (Z score -3.19; p=0.0007). Median overall survival was 10.4 months (95% CI 9.4-11.6) with panitumumab and 10.0 months (9.3-11.0) with cetuximab (HR 0.97; 95% CI 0.84-1.11). Panitumumab retained 105.7% (81.9-129.5) of the effect of cetuximab on overall survival seen in this study. The incidence of adverse events of any grade and grade 3-4 was similar across treatment groups. Grade 3-4 skin toxicity occurred in 62 (13%) patients given panitumumab and 48 (10%) patients given cetuximab. The occurrence of grade 3-4 infusion reactions was lower with panitumumab than with cetuximab (one [<0.5%] patient vs nine [2%] patients), and the occurrence of grade 3-4 hypomagnesaemia was higher in the panitumumab group (35 [7%] vs 13 [3%]). We recorded one treatment-related fatal adverse event: a lung infection in a patient given cetuximab. Our findings show that panitumumab is non-inferior to cetuximab and that these agents provide similar overall survival benefit in this population of patients. Both agents had toxicity profiles that were to be expected. In view of the consistency in efficacy and toxicity seen, small but meaningful differences in the rate of grade 3-4 infusion reactions and differences in dose scheduling can guide physician choice of anti-EGFR treatment.

Molecular imaging reveals trastuzumab-induced epidermal growth factor receptor downregulation in vivo.

Previous in vitro studies demonstrated that treating tumors expressing both epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 with trastuzumab resulted in increased EGFR homodimerization and subsequent rapid downregulation of EGFR. We investigated whether molecular imaging using near-infrared fluorescence (NIRF) imaging and PET probes could sensitively detect trastuzumab-induced EGFR downregulation in vivo. The F(ab')2 antibody fragment PaniF(ab')2 was generated by digesting the anti-EGFR monoclonal antibody panitumumab. PaniF(ab')2 was labeled with either a NIRF dye or (68)Ga, and optical imaging and small-animal PET imaging of Dye-PaniF(ab')2 and (68)Ga-PaniF(ab')2, respectively, were performed in HT-29 tumor-bearing nude mice treated with trastuzumab or untreated control. Longitudinal NIRF imaging studies revealed significantly reduced tumor uptake of Dye-PaniF(ab')2 on days 5 and 7 in trastuzumab-treated HT-29 tumors, compared with control. Western blotting confirmed the downregulation of EGFR after treatment with trastuzumab. Small-animal PET on day 5 after trastuzumab treatment also demonstrated decreased (68)Ga-PaniF(ab')2 uptake in trastuzumab-treated HT-29 tumors. The tumor uptake value of (68)Ga-PaniF(ab')2 obtained from PET imaging had an excellent linear correlation with the uptake value measured using biodistribution. The downregulation of EGFR induced by trastuzumab treatment could be detected noninvasively using optical and PET imaging. This molecular imaging strategy could provide a dynamic readout of changes in the tumor signaling and may facilitate the noninvasive monitoring of the early tumor response to drug treatment.

Moving Forward With Expanding to an “All-RASMutational Analysis” in Metastatic Colorectal Cancer: BeyondKRASMutations

The advent of biologic agents such as those that target the epidermal growth factor receptor (EGFR) has favorably impacted outcomes for patients with metastatic colorectal cancer (mCRC). An important downstream component of EGFR is the RAS signaling pathway. RAS proteins mainly include KRAS and NRAS. Activating KRAS mutations occur in 30% to 50% of colorectal tumors, most commonly in exon 2 as point mutations in codon 12 followed by mutations in codon 13. NRAS mutations occur in 3% to 5% of colorectal tumors. Since initial approval of the EGFR-directed monoclonal antibodies cetuximab (2004) and panitumumab (2006) for clinical use in mCRC, strategies to improve selection of the appropriate patients have constantly been refined. In 2005, the first confirmation that immunohistochemical analysis for EGFR expression has no predictive value in selecting or excluding patients allowed the use of these agents to be expanded to all eligible patients. In November 2008, the NCCN Colorectal Panel recommended routine KRAS (exon 2 codons 12/13) mutational testing based on consistent findings from multiple retrospective analyses of large clinical trials confirming that KRAS mutational status had predictive value for the use of antiEGFR monoclonal antibodies in mCRC. This move effectively restricted the use of these agents to approximately 60% of all patients with nonmutated KRAS mCRC, sparing the remainder of patients the risk of toxicities and the cost in the absence of a clear benefit. After this restriction, early reports suggested a possible clinical benefit for cetuximab in patients with mCRC with KRAS G13D mutations. However, another report from 3 randomized trials failed to suggest a similar benefit from panitumumab in the presence of a KRAS G13D mutation. These inconsistent results, the absence of a clear biology, and the overall poor outcome associated with the KRAS G13D mutation made this finding inconsequential to actual clinical practice pending further clinical validation. The NCCN Colorectal Cancer Panel continues to recommend against the use of anti-EGFR therapy in patients with codon 13 mutations. More recent data suggest that testing for additional RAS mutations (KRAS exons 3 or 4 and NRAS exon 1, 2, 3, or 4) present in 16% of tumors previously identified as KRAS (exon 2 codons 12/13) wild-type may allow for further refinement. A predefined retrospective analysis of the large prospective randomized trial PRIME (FOLFOX4 [leucovorin, 5-FU, and oxaliplatin] +/– panitumumab in first-line treatment of mCRC) suggests that the presence of these additional RAS mutations predict for lack of benefit. Data from the large phase II randomized study PEAK (FOLFOX plus panitumumab vs FOLFOX plus bevacizumab in first-line treatment of mCRC) confirmed the results from PRIME. This initiated a label change clarifying that panitumumab in combination with oxaliplatin-based chemotherapy is not indicated in the treatment of patients with RAS (KRAS or NRAS) mutation-positive mCRC. Despite these preliminary findings, there was very little uptake for incorporating an all-RAS mutational analysis before using EGFR inhibitors in mCRC. Why the initial reluctance? In addition to the lack of available standardized testing to include all RAS mutations, additional confirmatory data from studies, especially those incorporating cetuximab or irinotecan (which remains the preferred chemotherapeutic backbone Tanios Bekaii-Saab, MD

MicroRNAs as novel predictive biomarkers and therapeutic targets in colorectal cancer.

Colorectal cancer (CRC) is the third most common cancer in western countries. Despite significant improvement in available treatment options, CRC still remains the second leading cause of cancer-related death. Traditionally, 5-fluorouracil has been used as the main chemotherapy drug for treatment of metastatic CRC (mCRC). However, during the last two decades more effective chemotherapeutic agents such as oxaliplatin, irinotecan and the monoclonal antibodies cetuximab, panitumumab and bevacizumab have been used in clinical practice. More recently, the therapeutic armamentarium has been supplemented by the monoclonal antibodies bevacizumab, cetuximab and panitumumab as well as the protein-trap aflibercept and the small molecule multi-kinase inhibitor regorafenib. One of the major problems for the management of CRC is the inherent or acquired resistance to therapeutic approaches. The discovery of microRNAs (miRNAs), a class of small, endogenous, non-coding, single-stranded RNAs that play a role as post-transcriptional regulators, has added new dimensions to the diagnosis and treatment of cancer. Because miRNAs are important regulators of carcinogenesis, progression, invasion, angiogenesis and metastases in CRC, they might serve as potential predictive and prognostic factors and even as therapeutic targets themselves. Several miRNAs are already known to be dysregulated in CRCs and have been linked to biological processes involved in tumor progression and response to anti-cancer therapies. This review summarizes current therapeutic approaches for treating CRC and highlights the role of miRNAs as novel predictive biomarkers and potential drug targets in CRC patients.

Epidermal Growth Factor Receptor Inhibitors: Coming of Age

Agents targeting the epidermal growth factor (EGFR)-mediated signaling pathway are used in the treatment of various solid tumors, including lung, breast, pancreatic, colorectal, and head and neck cancers. Clinical evidence supporting the benefits of targeted agents directed against EGFR/HER1 in various solid tumors is discussed, as well as the survival end points used in the pivotal clinical trials, current applications, and future research directions. Agents reviewed include the monoclonal antibodies cetuximab and panitumumab, both of which block ligand binding to the extracellular domain, and the small-molecule tyrosine kinase inhibitors gefitinib, erlotinib, and afatinib that exert their effects at the intracellular portion of the receptor to prevent tyrosine kinase phosphorylation and the activation of signal transduction pathways. EGFR inhibitors have a mechanism of action distinct from traditional cytotoxic therapies, and combining these agents with chemotherapy produces synergistic anticancer activity without overlapping toxicity profiles. The level of EGFR expression does not correlate with agent response, and many tumors are resistant to treatment. Even if tumors are initially sensitive to these agents, they inevitably acquire resistance through complex, poorly understood molecular mechanisms. EGFR-directed therapies have changed the treatment paradigms in metastatic lung, colorectal, and head and neck cancers and improved outcomes. A better understanding of mechanisms of resistance to these agents is crucial for effective drug development. Predictive biomarkers are being developed to deliver personalized therapies.

Case Report: Long-Term Survival in Patient with Cirrhosis of the Liver and Colon Cancer K-ras Wild-Type

K-ras wild-type carcinoma is a tumour that is sensitive to treatment with anti-cancer and anti-EGFR drugs: the combination of Cetuximab and Panitumumab with chemotherapy (Cetuximab) or as a single therapy (Panitumumab). Case Report: The clinical case presented here refers to a 68-year-old patient who had been diagnosed with adenocarcinoma of the recto sigmoid with pelvic recurrence three years after surgery. The patient had a severe co-morbidity: correlated B-type liver cirrhosis. First-line chemotherapy was begun with Oxaliplatin plus Capecitabine (CAPOXI) following a relapse, and this continued for six months (six cycles), when the treatment was interrupted because of the disease’s progression and hematological and gastrointestinal toxicity. Following an assessment of the K-ras, diagnosed as wild type, the patient was excluded from second-line chemotherapy treatment because of decompensated cirrhosis and the persistence of thrombocytopenia and leukopenia. The patient was put forward for biological treatment with an anti-EGFR monoclonal antibody (Panitumumab). Panitumumab was administered at a dosage of 6 mg/kg every 2 weeks for 17 months; the treatment was well tolerated, despite the cirrhosis, and the main toxicity was the skin rash. Conclusion: In patients with severe comorbidities such as cirrhosis of the liver and K-ras wild-type carcinomas, therapy with a monoclonal antibody such as Panitumumab is a treatment that is well tolerated, with few serious toxic side-effects; it also offers advantages in terms of survival and clinical benefits.

Biomarker testing for treatment of metastatic colorectal cancer: role of the pathologist in community practice.

The past decade has been marked by significant advancements in the treatment of patients with metastatic colorectal cancer (mCRC), including the approval of novel biologic agents such as the angiogenesis inhibitors bevacizumab and afibercept and the epidermal growth factor receptor monoclonal antibodies (mAbs) cetuximab and panitumumab. Cetuximab was recently approved by the US Food and Drug Administration in combination with FOLFIRI (irinotecan, 5-fuorouracil, leucovorin) for the first-line treatment of patients with KRAS mutation-negative (wild-type) tumors as determined by an FDA-approved companion diagnostic. It was the first FDA approval in mCRC requiring use of a diagnostic test that is predictive of response prior to initiation of frontline therapy. The approval highlights the need for reflexive KRAS mutation testing at diagnosis to accurately determine all available treatment options. Although KRAS testing has been used by pathologists in mCRC for several years, accurate and timely reporting of test results and open communication with medical oncologists is even more essential to ensure appropriate first-line treatment selection and avoid any treatment delays. Consequently, it is critical that pathologists are highly trained and educated on KRAS testing methodology and the pros and cons of the various methods available. In this review, we discuss the development of KRAS as a biomarker in mCRC and key topics of concern to the pathologist who works with the oncologist in the community setting, including specimen preparation, KRAS testing methods, and reporting of test results. In this era of personalized medicine, pathologist education and communication with oncologists on biomarkers is paramount for optimal patient care.

Abstract P4-15-04: Synthesis and characterization of EGFR antibody-mediated tumor targeted “gold nanobombs” for treatment of locally advanced breast cancer

Abstract Purpose: Epidermal growth factor receptor (EGFR) represents an important target for treatment of locally advanced breast cancer (LABC), since about 30% of patients with LABC have triple negative breast tumor, and these tumors are often EGFR-positive. Our aim was to synthesize and characterize a novel form of “gold nanobomb” (GNB) for localized targeted radioimmunotherapy of LABC. GNB uses gold nanoparticles (AuNPs) as a carrier to conjugate both EGFR targeting monoclonal antibody (panitumumab) and the β-particle emitting radionuclide 177Lu. Ultimately, these GNB would be administered locally in LABC for tumor treatment while minimizing normal tissue exposure. Methods: The basic idea for construction of this new-targeted agent is to use different length of poly(ethylene glycol) (PEG) spacers to conjugate antibody and DOTA metal chelators for 177Lu. First, OPSS-PEG-NH2 was used to synthesize OPSS-PEG-DOTA for complexing 177Lu and OPSS-PEG-SVA was used to link antibody. Then these PEG spacers were linked to 30 nm AuNPs to form “GNB”. OPSS-PEG-antibody was analyzed by SDS-PAGE and trinitrobenzenesulfonic acid (TNBSA) assay to determine the degree of amine substitution after PEGylation. A radiometric assay was used to determine the number of PEGylated antibody and DOTA-PEG-OPSS per AuNPs. Specificity of GNB for EGFR and internalization into MBA-MD-468 (1×106 EGFR/cell), MBA-MD-231 (1×105 EGFR/cell) and MCF-7 (1×104 EGFR/cell) was confirmed by confocal and darkfield fluorescence microscopy. Binding assay and cell fractionation study were used to determine the binding affinity to EGFR and the total amount of GNB internalized. Results: Reacting panitumumab with increasing ratios of PEG resulted in an increase in molecular weight from 147 to 250 kDa. This result was in accordance with TNBSA assay where increasing ratio of PEG was associated with increasing lysine substitution (1.4 to 50.9 PEGylated lysine per antibody). PEGylation of 1.4 ± 1.7 lysine per antibody resulted in retention of immunoreactivity and when the immunoconjugates were linked to AuNPs, 8.09 ± 0.38 antibodies were attached to one AuNP. The total number of OPSS-PEG-DOTA per AuNP was estimated to be 812 ± 53. The total size of GNB was 67.3 ± 0.6 nm and there was no particle precipitation or aggregation after incubation in PBS. Competitive binding assay revealed that GNB was targeted strongly to EGFR (Kd antibody: 2.7 ± 0.3 nM; Kd GNB: 5.0 ± 4.9 nM) and darkfield microscopy showed that low PEG to antibody ratio increased the targeting efficiency when compared to high PEG to antibody ratio. Confocal microscopy revealed specific GNB uptake in MDA-MB-468 cells and cell fractionation study demonstrated receptor-mediated internalization of GNB, where the total amount of GNB internalized was about 3.1 and 22.2 fold higher in MDA-MB-468 cells than in MDA-MB-231 or MCF-7 cells. Conclusion: This GNB is very effective in targeting and in internalizing into EGFR, thus the GNB labeled with 177Lu emitting β-particles may be a promising new localized treatment for LABC. We plan to now examine the cytotoxicity of GNB both in vitro and in vivo will be explored for treatment of EGFR positive tumors. Supported by a grant from the Canadian Breast Cancer Foundation. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-15-04.

Incidence and Risk of Treatment-Related Mortality with Anti-Epidermal Growth Factor Receptor Monoclonal Antibody in Cancer Patients: A Meta-Analysis of 21 Randomized Controlled Trials

BackgroundAnti-epidermal growth factor receptor (EGFR) monoclonal antibodies (MoAbs) cetuximab and panitumumab have emerged as an effective targeted therapy in the treatment of cancer patients, but the overall incidence and risk of fatal adverse events (FAEs) associated with these agents is still unclear. MethodsDatabases from PubMed, Web of Science and abstracts presented at ASCO meeting up to May 31, 2013 were searched to identify relevant studies. Eligible studies included prospective randomized controlled trials evaluating MoAbs in cancer patients with adequate data on FAEs. Statistical analyses were conducted to calculate the summary incidence, odds ratio and 95% confidence intervals (CIs) by using either random effects or fixed effect models according to the heterogeneity of included studies.ResultsA total of 14,776 patients with a variety of solid tumors from 21 clinical trials were included in our analysis. The overall incidence of MoAbs associated FAEs was 1.7% (95%CI: 1.1–2.5%), and the incidence of cetuximab-related FAEs was higher than that of panitumumab (2.0% versus 0.9%). Compared with the controls, the use of MoAbs was associated with a significantly increased risk of FAEs, with an OR of 1.37 (95%CI: 1.04–1.81, p=0.024). Subgroup analysis based on EGFR-MoAbs drugs, phase of trials and tumor types demonstrated a tendency to increase the risk of FAEs, but the risk did not increase in breast cancer, esophagus cancer and phase II trials. ConclusionsWith present evidence, the use of EGFR-MoAbs is associated with an increased risk of FAEs in patients with advanced solid tumors.

Use of monoclonal antibody–IRDye800CW bioconjugates in the resection of breast cancer

BackgroundComplete surgical resection of breast cancer is a powerful determinant of patient outcome, and failure to achieve negative margins results in reoperation in between 30% and 60% of patients. We hypothesize that repurposing Food and Drug Administration–approved antibodies as tumor-targeting diagnostic molecules can function as optical contrast agents to identify the boundaries of malignant tissue intraoperatively. Materials and methodsThe monoclonal antibodies bevacizumab, cetuximab, panitumumab, trastuzumab, and tocilizumab were covalently linked to a near-infrared fluorescence probe (IRDye800CW) and in vitro binding assays were performed to confirm ligand-specific binding. Nude mice bearing human breast cancer flank tumors were intravenously injected with the antibody–IRDye800 bioconjugates and imaged over time. Tumor resections were performed using the SPY and Pearl Impulse systems, and the presence or absence of tumor was confirmed by conventional and fluorescence histology. ResultsTumor was distinguishable from normal tissue using both SPY and Pearl systems, with both platforms being able to detect tumor as small as 0.5 mg. Serial surgical resections demonstrated that real-time fluorescence can differentiate subclinical segments of disease. Pathologic examination of samples by conventional and optical histology using the Odyssey scanner confirmed that the bioconjugates were specific for tumor cells and allowed accurate differentiation of malignant areas from normal tissue. ConclusionsHuman breast cancer tumors can be imaged in vivo with multiple optical imaging platforms using near-infrared fluorescently labeled antibodies. These data support additional preclinical investigations for improving the surgical resection of malignancies with the goal of eventual clinical translation.