Delineating the functional map of the interaction between nimotuzumab and the epidermal growth factor receptor

Targeting lung cancer with clinically relevant EGFR mutations using anti-EGFR RNA aptamer

A significant fraction of non-small cell lung cancer (NSCLC) cases are due to oncogenic mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR). Anti-EGFR antibodies have shown limited clinical benefit for NSCLC, whereas tyrosine kinase inhibitors (TKIs) are effective, but resistance ultimately occurs. The current landscape suggests that alternative ligands that target wild-type and mutant EGFRs are desirable for targeted therapy or drug delivery development. Here we evaluate NSCLC targeting using an anti-EGFR aptamer (MinE07). We demonstrate that interaction sites of MinE07 overlap with clinically relevant antibodies targeting extracellular domain III and that MinE07 retains binding to EGFR harboring the most common oncogenic and resistance mutations. When MinE07 was linked to an anti-c-Met aptamer, the EGFR/c-Met bispecific aptamer (bsApt) showed superior labeling of NSCLC cells in vitro relative to monospecific aptamers. However, dual targeting in vivo did not improve the recognition of NSCLC xenografts compared to MinE07. Interestingly, biodistribution of Cy7-labeled bsApt differed significantly from Alexa Fluor 750-labeled bsApt. Overall, our findings demonstrate that aptamer formulations containing MinE07 can target ectopic lung cancer without additional stabilization or PEGylation and highlights the potential of MinE07 as a targeting reagent for the recognition of NSCLC harboring clinically relevant EGFRs.

Nimotuzumab in the Treatment of Inoperable Esophageal Tumors of Epithelial Origin

Background

Nimotuzumab is a humanized monoclonal antibody that targets the epidermal growth factor receptor. It was approved in Cuba for the indication of inoperable malignant tumors of the esophagus of epithelial origin. The purpose of this study was to evaluate the safety, overall and progression-free survival, clinical response, and quality of life, in adult patients with inoperable esophageal tumors of epithelial origin treated with nimotuzumab in a practical context. Material and Methods. The number of patients who developed adverse events was determined, and the frequency, seriousness, causality, and severity of these adverse events were determined. It also determined the median of survival and progression-free survival and rates at 12 and 24 months and the quality of life.

Results

A total of 111 patients were included. The proportion of serious and related AE with the use of nimotuzumab was 1.3%. Most of the related AEs were mild and moderate, and the most frequent AEs were diarrhea, chills, and tremors. New diagnosed patients who received nimotuzumab concurrent with chemotherapy and radiotherapy reached a median OS of 12.2 months (95% CI, 6.9–17.5) and 12- and 24-month survival rates of 51.0% and 17.0%, respectively. Median PFS was 7.8 months (95% CI, 6.2–9.5), and 12- and 24-month PFS rates were 39.3% and 11.2%, respectively. A favorable evolution of the general state of health (p=0.03) was obtained from the beginning of treatment until month 12, with a significant reduction in the appearance of nausea (p=0.009), insomnia (p=0.04), constipation (p=0.04), eating difficulties (p=0.0006), and choking when swallowing (p=0.0001), but increased in dysphagia (p=0.02).

Conclusions

The administration of nimotuzumab was safe in the real-world setting. New diagnosed patients that received nimotuzumab concurrent with chemotherapy and radiotherapy reached a higher overall and progression-free survival and better quality of life than the rest of the patients. Trial registration is RPCEC00000215 (Cuban Registry of Clinical Trials; https://registroclinico.sld.cu/en/home). It is registered prospectively on June 30, 2016.

Domain-level epitope mapping of polyclonal antibodies against HER-1 and HER-2 receptors using phage display technology

HER-1 and HER-2 are tumor-associated antigens overexpressed in several epithelial tumors, and successfully targeted by therapeutic approaches against cancer. Vaccination with their recombinant extracellular domains has had encouraging results in the pre-clinical setting. As complex humoral responses targeting multiple epitopes within each antigen are the ultimate goal of such active immunotherapy strategies, molecular dissection of the mixture of antibody specificities is required. The current work exploits phage display of antigenic versions of HER-1 and HER-2 domains to accomplish domain-level epitope mapping. Recognition of domains I, III and IV of both antigens by antibodies of immunized mice was shown, indicating diverse responses covering a broad range of antigenic regions. The combination of phage display and site-directed mutagenesis allowed mutational screening of antigen surface, showing polyclonal antibodies' recognition of mutated receptor escape variants known to arise in patients under the selective pressure of the anti-HER-1 antibody cetuximab. Phage-displayed HER domains have thus the potential to contribute to fine specificity characterization of humoral responses during future development of anti-cancer vaccines.

Understanding and Modulating Antibody Fine Specificity: Lessons from Combinatorial Biology

Combinatorial biology methods such as phage and yeast display, suitable for the generation and screening of huge numbers of protein fragments and mutated variants, have been useful when dissecting the molecular details of the interactions between antibodies and their target antigens (mainly those of protein nature). The relevance of these studies goes far beyond the mere description of binding interfaces, as the information obtained has implications for the understanding of the chemistry of antibody–antigen binding reactions and the biological effects of antibodies. Further modification of the interactions through combinatorial methods to manipulate the key properties of antibodies (affinity and fine specificity) can result in the emergence of novel research tools and optimized therapeutics.

Is Tumor Cell Specificity Distinct from Tumor Selectivity In Vivo?: A Quantitative NIR Molecular Imaging Analysis of Nanoliposome Targeting

The significance and ability for receptor targeted nanoliposomes (tNLs) to bind to their molecular targets in solid tumors in vivo has been questioned, particularly as the efficiency of their tumor accumulation and selectivity is not always predictive of their efficacy or molecular specificity. This study presents, for the first time, in situ NIR molecular imaging-based quantitation of the in vivo specificity of tNLs for their target receptors, as opposed to tumor selectivity, which includes influences of enhanced tumor permeability and retention. Results show that neither tumor delivery nor selectivity (tumor-to-normal ratio) of cetuximab and IRDye conjugated tNLs correlate with EGFR expression in U251, U87 and 9L tumors, and in fact underrepresent their imaging-derived molecular specificity by up to 94.2%. Conversely, their in vivo specificity, which we quantify as the concentration of tNL-reported tumor EGFR provided by NIR molecular imaging, correlates positively with EGFR expression levels in vitro and ex vivo (Pearson's r= 0.92 and 0.96, respectively). This study provides a unique opportunity to address the problematic disconnect between tNL synthesis and in vivo specificity. The findings encourage their continued adoption as platforms for precision medicine, and facilitates intelligent synthesis and patient customization in order to improve safety profiles and therapeutic outcomes.

A monoclonal antibody recognizing a new epitope on CD81 inhibits T-cell migration without inducing cytokine production

CD81 is involved in leukocyte migration and cytokine induction. Previous work found that anti-CD81 monoclonal antibodies (mAbs) showed therapeutic potential for several immune diseases via inhibiting leukocyte migration. Although the suppression of cell migration is a promising approach for treating immune diseases, some anti-CD81 mAbs can induce cytokine production, which may exacerbate disease. To obtain new anti-human CD81 mAbs that inhibited migration in the absence of cytokine production enhancement activity, we screened a human single chain variable fragment by phage library. One of the new anti-CD81 mAbs isolated, DSP-8250, had equivalent inhibitory cell migration activity with the established anti-CD81 mAb 5A6, but it lacked cytokine induction activity. These mAbs recognized different epitopes on CD81. mAb 5A6, which had inhibitory activity on T-cell migration and increased cytokine production, bound to three residues, Ser179, Asn180 and Phe186 of CD81. In contrast, DSP-8250, which had inhibitory activity on T-cell migration but no cytokine enhancement activity, bound to four residues, His151, Ala164, Ser168 and Asn172 of CD81 as a unique epitope. These results indicate that the set of His151, Ala164, Ser168 and Asn172 forms a novel epitope that might make the application of anti-CD81 mAb therapeutically useful.

Nimotuzumab for Patients With Inoperable Cancer of the Head and Neck

EGFR activation induces cell proliferation, neoformation of blood vessels, survival, and metastasis of the cancer cells. Nimotuzumab is an engineered, intermediate affinity anti-EGFR antibody, that apart from other drugs in its class, is very safe and does not cause hypomagnesemia or grade 3–4 cutaneous rash. The antibody inhibits cell proliferation and angiogenesis, activates natural killer cells, stimulates dendritic cell maturation, and induces cytotoxic T cells. Nimotuzumab restores MHC-I expression on tumor cells, hindering one of the EGFR immune-escape ways. The antibody has been extensively studied in 7 clinical trials, concurrently with irradiation or irradiation plus chemotherapy in subjects with inoperable head and neck tumors. Nimotuzumab was safe and efficacious in unfit patients receiving irradiation alone and in subjects treated with cisplatin and radiotherapy. In patients with locally advanced squamous cell carcinomas of the head and neck, nimotuzumab in combination with low dose cisplatin and radiotherapy was superior to cisplatin and radiotherapy in progression free survival, disease free survival, and locoregional tumor control.

Affinity-matured variants derived from nimotuzumab keep the original fine specificity and exhibit superior biological activity

Nimotuzumab is a humanized monoclonal antibody against the Epidermal Growth Factor Receptor with a long history of therapeutic use, recognizing an epitope different from the ones targeted by other antibodies against the same antigen. It is also distinguished by much less toxicity resulting in a better safety profile, which has been attributed to its lower affinity compared to these other antibodies. Nevertheless, the ideal affinity window for optimizing the balance between anti-tumor activity and toxic effects has not been determined. In the current work, the paratope of the phage-displayed nimotuzumab Fab fragment was evolved in vitro to obtain affinity-matured variants. Soft-randomization of heavy chain variable region CDRs and phage selection resulted in mutated variants with improved binding ability. Two recombinant antibodies were constructed using these variable regions, which kept the original fine epitope specificity and showed moderate affinity increases against the target (3-4-fold). Such differences were translated into a greatly enhanced inhibitory capacity upon ligand-induced receptor phosphorylation on tumor cells. The new antibodies, named K4 and K5, are valuable tools to explore the role of affinity in nimotuzumab biological properties, and could be used for applications requiring a fine-tuning of the balance between binding to tumor cells and healthy tissues.

Effectiveness and normal tissue toxicity of Auger electron (AE) radioimmunotherapy (RIT) with [111In]In-Bn-DTPA-nimotuzumab in mice with triple-negative or trastuzumab-resistant human breast cancer xenografts that overexpress EGFR

INTRODUCTION

Our objective was to evaluate the effectiveness and normal tissue toxicity of nimotuzumab labeled with the Auger electron (AE)-emitter, ¹¹¹In ([¹¹¹In]In-Bn-DTPA-nimotuzumab) for radioimmunotherapy (RIT) of human triple-negative breast cancer (TNBC) or trastuzumab-resistant HER2-positive BC tumors overexpressing epidermal growth factor receptors (EGFR) in athymic mice.

METHODS

Normal tissue toxicity was studied in non-tumor-bearing Balb/c mice i.v. administered 9.0 or 28.6 MBq (3 mg/kg) of [¹¹¹In]In-Bn-DTPA-nimotuzumab, unlabeled nimotuzumab (3 mg/kg) or normal saline. A complete blood cell count (CBC) and serum alanine aminotransferase (ALT) and creatinine (Cr) were measured at 14 days. Body weight was monitored. RIT studies were performed in CD-1 athymic mice engrafted s.c. with MDA-MB-468 human TNBC tumors or TrR1 HER2-positive but trastuzumab-resistant BC tumors. Mice were i.v. administered two amounts (15.5 MBq; 3 mg/kg) of [¹¹¹In]In-Bn-DTPA-nimotuzumab separated by 14 days. Control mice received unlabeled Bn-DTPA-nimotuzumab (3 mg/kg) or anti-HER2 [¹¹¹In]In-Bn-DTPA-trastuzumab or normal saline. Tumor growth and body weight were measured for 6 weeks. A tumor growth index (TGI) and body weight index (BWI) were calculated to compare the tumor size and body weight post-treatment with the pre-treatment values. A tumor doubling ratio (TDR) was calculated for each treatment group compared to control mice receiving normal saline.

RESULTS

There was no loss of body weight or decreased red blood cells (RBC) or platelets (PLT) or increased serum ALT or Cr in Balb/c mice administered 9.0 or 28.6 MBq (3 mg/kg) of [¹¹¹In]In-Bn-DTPA-nimotuzumab compared to mice treated with unlabeled Bn-DTPA-nimotuzumab (3 mg/kg) or normal saline. There was a significant decrease in white blood cell (WBC) counts in Balb/c mice receiving 28.6 MBq but not 9.0 MBq of [¹¹¹In]In-Bn-DTPA-nimotuzumab. Based on these results, an administered amount of 15.5 MBq (3 mg/kg) was selected for RIT studies. Administration of two amounts (15.5 MBq; 3 mg/kg) separated by 14 days to CD-1 athymic mice with s.c. MDA-MB-468 xenografts strongly inhibited tumor growth. The TDR for mice treated with [¹¹¹In]In-Bn-DTPA-nimotuzumab was 2.15 compared to control mice receiving normal saline. In contrast, treatment with unlabeled Bn-DTPA-nimotuzumab or [¹¹¹In]In-Bn-DTPA-trastuzumab had no significant effect on tumor growth (TDR = 0.96 and 1.08, respectively). RIT with [¹¹¹In]In-Bn-DTPA-nimotuzumab also strongly inhibited the growth of TrR1 tumors in athymic mice (TDR = 2.13) compared to unlabeled Bn-DTPA-nimotuzumab (TDR = 0.91). There were no losses in body weight over 6 weeks in tumor bearing mice receiving [¹¹¹In]In-Bn-DTPA-nimotuzumab, unlabeled Bn-DTPA-nimotuzumab, [¹¹¹In]In-Bn-DTPA-trastuzumab or normal saline.

CONCLUSIONS

[¹¹¹In]In-Bn-DTPA-nimotuzumab was effective for treatment of TNBC or trastuzumab-resistant HER2-positive human BC tumors in mice that overexpress EGFR at administered amounts that caused no decrease in body weight or normal tissue toxicity in non-tumor-bearing Balb/c mice.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

Our results suggest that Auger electron RIT with [¹¹¹In]In-Bn-DTPA-nimotuzumab may provide a novel therapeutic option for patients with TNBC or trastuzumab-resistant HER2-positive BC that overexpresses EGFR. The low normal tissue toxicity of this approach may allow combination with other targeted therapies such as antibody-drug conjugates (ADCs).

Near infrared imaging of epidermal growth factor receptor positive xenografts in mice with domain I/II specific antibody fragments

Epidermal growth factor receptor (EGFR) is a transmembrane cell surface receptor that is frequently overexpressed and/or mutated in many cancers. Therapies targeting EGFR have poor outcomes due to the lack of reliable diagnostic tests to monitor EGFR. Current in vitro EGFR diagnostic methods are invasive, requiring biopsies, which limits tumor sampling and availability. EGFR molecular imaging provides non-invasive whole-body images capable of detecting primary tumors and metastases, which can be used to diagnose and monitor response to therapy. Methods: We evaluated properties of two anti-EGFR fragments, 8708 and 8709, as molecular-targeted imaging probes. 8708 and 8709 are anti-EGFR antigen binding fragments (Fabs) that recognize domain I/II of EGFR, which is distinct from epitopes recognized by current anti-EGFR therapeutic antibodies. We used complementarity determining region sequences from 8708 and 8709 Fabs to generate an anti-EGFR IgG and (scFv)2 and scFv-Fc antibody fragments. We expressed, purified, and labeled the IgG and fragments with IRDye800CW and used them to image EGFR-positive and -negative xenografts in CD-1 nude mice. 8709 scFv-Fc was also tested for competitive binding with the therapeutic anti-EGFR antibody nimotuzumab and for quantifying ratios of EGFR and EGFRvIII deletion mutant. Results: IRDye800CW-labeled 8708 (scFv)2 and 8709 scFv-Fc imaging probes showed high levels of accumulation and good retention in EGFR-positive xenografts, with peak accumulation occurring at 24 and 48 hours post injection, respectively. IRDye680RD-labeled 8709 scFv-Fc did not compete with IRDye800CW-labeled nimotuzumab for EGFR binding as assayed by flow cytometry using an EGFR-positive cell line. IRDye680RD-labeled 8709 scFv-Fc and IRDye800CW-labeled nimotuzumab used in combination were able to determine the ratio of cells expressing EGFR and a deletion mutant EGFRvIII. Conclusion: IRDye800CW-labeled 8708 (scFv)2 and 8709 scFv-Fc had desirable binding affinities, clearance times, and tumor accumulation to be used for imaging in combination with current EGFR targeted therapies. This study highlights the potential for using 8708 (scFv)2 and 8709 scFv-Fc as EGFR diagnostic and therapy monitoring tools.

High throughput functional epitope mapping: revisiting phage display platform to scan target antigen surface

Antibody engineering must be accompanied by mapping strategies focused on identifying the epitope recognized by each antibody to define its unique functional identity. High throughput fine specificity determination remains technically challenging. We review recent experiences aimed at revisiting the oldest and most extended display technology to develop a robust epitope mapping platform, based on the ability to manipulate target-derived molecules (ranging from the whole native antigen to antigen domains and smaller fragments) on filamentous phages. Single, multiple and combinatorial mutagenesis allowed comprehensive scanning of phage-displayed antigen surface that resulted in the identification of clusters of residues contributing to epitope formation. Functional pictures of the epitope(s) were thus delineated in the natural context. Successful mapping of antibodies against interleukin-2, epidermal growth factor and its receptor, and vascular endothelial growth factor showed the versatility of these procedures, which combine the accuracy of site-directed mutagenesis with the high throughput potential of phage display.

Roles of EGFR and KRAS and their downstream signaling pathways in pancreatic cancer and pancreatic cancer stem cells

Pancreatic cancer is currently the fourth most common cancer, is increasing in incidence and soon will be the second leading cause of cancer death in the USA. This is a deadly malignancy with an incidence that approximates the mortality with 44,000 new cases and 36,000 deaths each year. Surgery, although only modestly successful, is the only curative option. However, due the locally aggressive nature and early metastasis, surgery can be performed on less than 20% of patients. Cytotoxic chemotherapy is palliative, has significant toxicity and improves survival very little. Thus new treatment paradigms are needed desperately. Due to the extremely high frequency of KRAS gene mutations (>90%) detected in pancreatic cancer patients, the roles of the epidermal growth factor receptor (EGFR), Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTORC1/GSK-3 pathways have been investigated in pancreatic cancer for many years. Constitutively active Ras can activate both of these pathways and there is cross talk between Ras and EGFR which is believed to be important in driving metastasis. Mutant KRAS may also drive the expression of GSK-3 through Raf/MEK/ERK-mediated effects on GSK-3 transcription. GSK-3 can then regulate the expression of NF-kappaB which is important in modulating pancreatic cancer chemoresistance. While the receptors and many downstream signaling molecules have been identified and characterized, there is still much to learn about these pathways and how their deregulation can lead to cancer. Multiple inhibitors to EGFR, PI3K, mTOR, GSK-3, Raf, MEK and hedgehog (HH) have been developed and are being evaluated in various cancers. Current research often focuses on the role of these pathways in cancer stem cells (CSC), with the goal to identify sites where therapeutic resistance may develop. Relatively novel fields of investigation such as microRNAs and drugs used for other diseases e.g., diabetes, (metformin) and malaria (chloroquine) have provided new information about therapeutic resistance and CSCs. This review will focus on recent advances in the field and how they affect pancreatic cancer research and treatment.