Phase I/II clinical trial of the humanized anti-EGF-r monoclonal antibody h-R3 labelled with 99mTc in patients with tumour of epithelial origin

Advances and challenges in immunoPET methodology

Immuno-positron emission tomography (immunoPET) enables imaging of specific targets that play a role in targeted therapy and immunotherapy, such as antigens on cell membranes, targets in the disease microenvironment, or immune cells. The most common immunoPET applications use a monoclonal antibody labeled with a relatively long-lived positron emitter such as 89Zr (T 1/2 = 78.4 h), but smaller antibody-based constructs labeled with various other positron emitting radionuclides are also being investigated. This molecular imaging technique can thus guide the development of new drugs and may have a pivotal role in selecting patients for a particular therapy. In early phase immunoPET trials, multiple imaging time points are used to examine the time-dependent biodistribution and to determine the optimal imaging time point, which may be several days after tracer injection due to the slow kinetics of larger molecules. Once this has been established, usually only one static scan is performed and semi-quantitative values are reported. However, total PET uptake of a tracer is the sum of specific and nonspecific uptake. In addition, uptake may be affected by other factors such as perfusion, pre-/co-administration of the unlabeled molecule, and the treatment schedule. This article reviews imaging methodologies used in immunoPET studies and is divided into two parts. The first part summarizes the vast majority of clinical immunoPET studies applying semi-quantitative methodologies. The second part focuses on a handful of studies applying pharmacokinetic models and includes preclinical and simulation studies. Finally, the potential and challenges of immunoPET quantification methodologies are discussed within the context of the recent technological advancements provided by long axial field of view PET/CT scanners.

Single domain Camelid antibody fragments for molecular imaging and therapy of cancer

Despite innovations in cancer therapeutics, cancer remains associated with high mortality and is one of biggest health challenges worldwide. Therefore, developing precise cancer imaging and effective treatments is an unmet clinical need. A relatively novel type of therapeutics are heavy chain variable domain antibody fragments (VHHs) derived from llamas. Here, we explored the suitability of VHHs for cancer imaging and therapy through reviewing the existing literature. We searched the MEDLINE, EMBASE and Cochrane databases and identified 32 papers on molecular imaging and 41 papers on therapy that were suitable for comprehensive reviewing. We found that VHHs harbor a higher specificity and affinity compared to mAbs, which contributes to high-quality imaging and less side-effects on healthy cells. The employment of VHHs in cancer imaging showed remarkably shorter times between administration and imaging. Studies showed that 18F and 99mTc are two optimal radionuclides for imaging with VHHs and that site-specific labelling is the optimal conjugation modality for VHHs with radionuclide or fluorescent molecules. We found different solutions for reducing kidney retention and immunogenicity of VHHs. VHHs as anticancer therapeutics have been tested in photodynamic therapy, targeted radionuclide therapy, immunotherapy and molecular targeted therapy. These studies showed that VHHs target unique antigen epitopes, which are distinct from the ones recognized by mAbs. This advantage means that VHHs may be more effective for targeted anticancer therapy and can be combined with mAbs. We found that high cellular internalization and specificity of VHHs contributes to the effectiveness and safety of VHHs as anticancer therapeutics. Two clinical trials have confirmed that VHHs are effective and safe for cancer imaging and therapy. Together, VHHs seem to harbor several advantages compared to mAbs and show potential for application in personalized treatment for cancer patients. VHH-based imaging and therapy are promising options for improving outcomes of cancer patients.

Synthesis of 111In-p-SCN-Bn-DTPA-nimotuzumab and its preclinical evaluation in EGFR positive NSCLC animal model

The aim of this study was to investigate labeling of nimotuzumab (h-R3) with 111In using p-SCN-Bn-DTPA as bifunctional chelate, evaluate its targeting potential against SK-LU-1, H226, H650, H661, and HCC4006 non-small cell lung carcinoma (NSCLC) cell lines and correlate epidermal growth factor receptor (EGFR) expression level with internalization kinetics, biodistribution and imaging accuracy using Balb/c mice and New Zealand White rabbit (NZWR) animal model. The amount of p-SCN-Bn-DTPA attached to h-R3 was assessed by measuring relative absorbance at 652 nm with ultraviolet (UV) spectrophotometer. High-performance liquid chromatography (HPLC) was used to determine percent radiochemical purity (%RCP) and in vitro stability using excess amount of diethylenetriamine pentaacetate (DTPA). The in vitro stability in rat serum was estimated using iTLC-SG. EGFR expression level in each tumor was assessed by chemiluminescence. In vivo uptake in different organs of Balb/c mice and non-invasive imaging potential using NZWR bearing HCC4006 tumor, was evaluated with gamma camera. UV spectroscopy has confirmed the attachment of five p-SCN-Bn-DTPA (chelate) with one antibody. The HPLC indicated 98.85 ± 0.14% (n = 3) %RCP with high yield (>96%), specific activity 3.5 ± 0.0.25 mCi per mg and 94.25 ± 0.34% in vitro stability at 37 °C in mice serum. In excess DTPA no considerable transchelation was experiential from the 111In labeled p-SCN-Bn-DTPA-h-R3 to the challenger. The EGFR expression in HCC4006 was higher amongst all with band density of 23.53 relative to 1.00 of H226. Initially internalization was lower which went up 1.05 × 104 molecules per HCC4006 cell in 48 h. The optimal concentration of h-R3 for maximum uptake was 15 μg per animal. Higher uptake in target organ was observed in animal infected with HCC4006 cells. However, in excess pure h-R3 the uptake was significantly reduced indicating tumor specificity. HCC4006 target site was undistinguishable relative to background activity in the initial phase of imaging due to poor uptake. However, within 60 h the HCC4006 tumor was quite apparent. This experiment suggests that at optimal dosage of 111In labeled h-R3 can be used for localization and identification of EGFR positive NSCLC using gamma camera.

Trial Watch: Monoclonal antibodies in cancer therapy

Since the advent of hybridoma technology, dating back to 1975, monoclonal antibodies have become an irreplaceable diagnostic and therapeutic tool for a wide array of human diseases. During the last 15 years, several monoclonal antibodies (mAbs) have been approved by FDA for cancer therapy. These mAbs are designed to (1) activate the immune system against tumor cells, (2) inhibit cancer cell-intrinsic signaling pathways, (3) bring toxins in the close proximity of cancer cells, or (4) interfere with the tumor-stroma interaction. More recently, major efforts have been made for the development of immunostimulatory mAbs that either enhance cancer-directed immune responses or limit tumor- (or therapy-) driven immunosuppression. Some of these antibodies, which are thought to facilitate tumor eradication by initiating or sustaining a tumor-specific immune response, have already entered clinical trials. In this Trial Watch, we will review and discuss the clinical progress of the most important mAbs that are have entered clinical trials after January 2008.

Development of Antibody Immuno-PET/SPECT Radiopharmaceuticals for Imaging of Oncological Disorders-An Update

Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are molecular imaging strategies that typically use radioactively labeled ligands to selectively visualize molecular targets. The nanomolar sensitivity of PET and SPECT combined with the high specificity and affinity of monoclonal antibodies have shown great potential in oncology imaging. Over the past decades a wide range of radio-isotopes have been developed into immuno-SPECT/PET imaging agents, made possible by novel conjugation strategies (e.g., site-specific labeling, click chemistry) and optimization and development of novel radiochemistry procedures. In addition, new strategies such as pretargeting and the use of antibody fragments have entered the field of immuno-PET/SPECT expanding the range of imaging applications. Non-invasive imaging techniques revealing tumor antigen biodistribution, expression and heterogeneity have the potential to contribute to disease diagnosis, therapy selection, patient stratification and therapy response prediction achieving personalized treatments for each patient and therefore assisting in clinical decision making.

Biodistribution and Tumor Uptake of 67Ga-Nimotuzumab in a Malignant Pleural Mesothelioma Xenograft

Malignant pleural mesothelioma (MPM) is the most common tumor of the pulmonary pleura. It is a rare and aggressive malignancy, generally associated with continuous occupational exposure to asbestos. Only a multimodal-approach to treatment, based on surgical resection, chemotherapy and/or radiation, has shown some benefits. However, the survival rate remains low. Nimotuzumab (h-R3), an anti-EGFR (epidermal growth factor receptor) humanized antibody, is proposed as a promising agent for the treatment of MPM. The aim of this research was to implement a procedure for nimotuzumab radiolabeling to evaluate its biodistribution and affinity for EGF (epidermal growth factor) receptors present in a mesothelioma xenograft. Nimotuzumab was radiolabeled with 67Ga; radiolabel efficiency, radiochemical purity, serum stability, and biodistribution were evaluated. Biodistribution and tumor uptake imaging studies by microSPECT/CT in mesothelioma xenografts revealed constant nimotuzumab uptake at the tumor site during the first 48 h after drug administration. In vivo studies using MPM xenografts showed a significant uptake of this radioimmunoconjugate, which illustrates its potential as a biomarker that could promote its theranostic use in patients with MPM.

Pharmacology of Epidermal Growth Factor Inhibitors

Research into the molecular bases of malignant diseases has yielded the development of many novel agents with potential antitumor activity. Evidence for a causative role for the epidermal growth factor receptor (EGFR), which is now regarded as an excellent target for cancer chemotherapy in human cancer, leads to the development of EGFR inhibitors. Two classes of anti-EGFR agents are currently in clinical use: monoclonal antibodies directed at the extracellular domain of the receptor, and the low-molecular-weight receptor tyrosine kinase inhibitors acting intracellularly by competing with adenosine triphosphate for binding to the tyrosine kinase portion of the EGFR. The effect on the receptor interferes with key biological functions including cell cycle arrest, potentiation of apoptosis, inhibition of angiogenesis and cell invasion and metastasis. Cetuximab, a monoclonal antibody, and the receptor tyrosine kinase inhibitors gefitinib and erlotinib are currently approved for the treatment of patients with cancer. New agents with clinical activity are entering the clinic, and new combinatorial approaches are being explored with the aim of improving the potency and pharmacokinetics of EGFR inhibition, to increase the synergistic activity in combination with chemotherapy and overcome resistance to the EGFR inhibitors.

Targeting the epidermal growth factor receptor in solid tumor malignancies

The epidermal growth factor receptor (EGFR) is over-expressed, as well as mutated, in many types of cancers. In particular, the EGFR variant type III mutant (EGFRvIII) has attracted much attention as it is frequently and exclusively found on many tumor cells, and hence both EGFR and EGFRvIII have been proposed as valid targets in many cancer therapy settings. Different strategies have been developed in order to either inhibit EGFR/EGFRvIII activity or to ablate EGFR/EGFRvIII-positive tumor cells. Drugs that inhibit these receptors include monoclonal antibodies (mAbs) that bind to the extracellular part of EGFR, blocking the binding sites for the EGFR ligands, and intracellular tyrosine kinase inhibitors (TKIs) that block the ATP binding site of the tyrosine kinase domain. Besides an EGFRvIII-targeted vaccine, conjugated anti-EGFR mAbs have been used in different settings to deliver lethal agents to the EGFR/EGFRvIII-positive cells; among these are radio-labelled mAbs and immunotoxins. This article reviews the current status and efficacy of EGFR/EGFRvIII-targeted therapies.

Recent trends in antibody-based oncologic imaging

Antibodies, with their unmatched ability for selective binding to any target, are considered as potentially the most specific probes for imaging. Their clinical utility, however, has been limited chiefly due to their slow clearance from the circulation, longer retention in non-targeted tissues and the extensive optimization required for each antibody-tracer. The development of newer contrast agents, combined with improved conjugation strategies and novel engineered forms of antibodies (diabodies, minibodies, single chain variable fragments, and nanobodies), have triggered a new wave of antibody-based imaging approaches. Apart from their conventional use with nuclear imaging probes, antibodies and their modified forms are increasingly being employed with non-radioisotopic contrast agents (MRI and ultrasound) as well as newer imaging modalities, such as quantum dots, near infra red (NIR) probes, nanoshells and surface enhanced Raman spectroscopy (SERS). The review article discusses new developments in the usage of antibodies and their modified forms in conjunction with probes of various imaging modalities such as nuclear imaging, optical imaging, ultrasound, MRI, SERS and nanoshells in preclinical and clinical studies on the diagnosis, prognosis and therapeutic responses of cancer.

Phase I clinical trial of the anti-EGFR monoclonal antibody nimotuzumab with concurrent external thoracic radiotherapy in Canadian patients diagnosed with stage IIb, III or IV non-small cell lung cancer unsuitable for radical therapy

PURPOSE

Many patients with non-small cell lung cancer (NSCLC) are eligible only for palliative radiation (RT) at presentation. This study was designed to assess the feasibility of adding the anti-EGFR monoclonal antibody nimotuzumab to palliative thoracic RT.

METHODS

Patients with stage IIB, III or IV NSCLC considered unsuitable for radical radiation or chemo-radiation received nimotuzumab weekly 8× (100, 200 or 400 mg) with radiation (30 or 36 Gy in 3 Gy fractions). If response or disease stability was observed, nimotuzumab was continued every other week starting from week 10 until progression or toxicity.

RESULTS

Eighteen patients were enrolled: 6 at 100 mg, 7 at 200 mg, 5 at 400 mg nimotuzumab. Patient characteristics included median age 69 years, 11 males, 17 smokers, 17 Caucasians, stage IIIA/IIIB/IV 2/7/9, 5 Eastern Cooperative Oncology Group performance status (PS) 2; 9 adenocarcinoma. The most commonly reported adverse events were fatigue, anorexia, chills, pain and hypophosphatemia (grades 1 to 2 in most patients). No severe skin or allergic toxicity was noted. No dose-limiting toxicity was encountered. Objective response rate and disease control rate inside the radiation field were 66 and 94.0%, respectively.

CONCLUSION

Nimotuzumab administered concurrently with palliative thoracic radiation is well tolerated at each of the three doses investigated in NSCLC patients unsuitable for radical treatment. The low toxicity and absence of rash make this combination therapeutically attractive for frail patients with other co-morbidities and poor performance status. These results support further testing of this regimen in the phase II setting.

A dose-escalation phase I trial of nimotuzumab, an antibody against the epidermal growth factor receptor, in patients with advanced solid malignancies

PURPOSE

Nimotuzumab is a humanized monoclonal antibody which inhibits the ligand-dependent activation of epidermal growth factor receptor (EGFR). We conducted a phase I trial to assess the pharmacodynamic (PD) effects of escalating doses of nimotuzumab administered alone in patients with advanced solid cancers patients.

EXPERIMENTAL DESIGN

Patients were treated with escalating doses of weekly intravenous nimotuzumab at doses ranging between 100 and 800 mg. Tumor and skin biopsies were done before start of treatment and repeated 3 weeks after to assess immunohistochemical expression of EGFR and its downstream components.

RESULTS

Seventeen patients were enrolled, including 1 patient never treated. Although 1 dose-limiting-toxicity (DLT) was observed at 100 mg (grade 3 fatigue), nimotuzumab dose was escalated to 800 mg with no other DLT. No grade 4 toxicity was observed. Only 3 patients developed a grade 1 acneiform rash (18.7%). One patient achieved a partial response (6.2%) and 8 patients had stable disease (50.0%). The median TTP was 2.4 months. No significant changes in EGFR, AKT, ERK and Ki67 immuno-stainings were observed between pre- and on-treatment tumor or skin biopsies.

CONCLUSION

Nimotuzumab could be safety administered up to 800 mg with manageable toxicity. No relationships were found between pharmacodynamic effects on EGFR downstream signaling pathways and drug efficacy or toxicity.

Nimotuzumab in pediatric glioma

High-grade gliomas and diffuse brainstem gliomas carry a very poor prognosis despite current therapies, and account together for the largest number of deaths in children with brain tumors. Many of these tumors have been found to overexpress the EGF receptor (EGFR). Nimotuzumab (h-R3) is a humanized monoclonal antibody against the EGFR, and consequently inhibits tyrosine kinase activation. In vitro and in vivo studies have supported the antiproliferative, antiangiogenic, pro-apoptotic and radiosensitizing activities of nimotuzumab. Emerging trials suggest a promising role for nimotuzumab as a therapeutic agent in patients with high-grade gliomas. This review attempts to provide a context for the evolving interest and evidence for nimotuzumab in pediatric glioma.

Immunotherapy of malignant brain tumors

Despite aggressive multi-modality therapy including surgery, radiation, and chemotherapy, the prognosis for patients with malignant primary brain tumors remains very poor. Moreover, the non-specific nature of conventional therapy for brain tumors often results in incapacitating damage to surrounding normal brain and systemic tissues. Thus, there is an urgent need for the development of therapeutic strategies that precisely target tumor cells while minimizing collateral damage to neighboring eloquent cerebral cortex. The rationale for using the immune system to target brain tumors is based on the premise that the inherent specificity of immunologic reactivity could meet the clear need for more specific and precise therapy. The success of this modality is dependent on our ability to understand the mechanisms of immune regulation within the central nervous system (CNS), as well as counter the broad defects in host cell-mediated immunity that malignant gliomas are known to elicit. Recent advances in our understanding of tumor-induced and host-mediated immunosuppressive mechanisms, the development of effective strategies to combat these suppressive effects, and a better understanding of how to deliver immunologic effector molecules more efficiently to CNS tumors have all facilitated significant progress toward the realization of true clinical benefit from immunotherapeutic treatment of malignant gliomas.

SPECT imaging with 99mTc-labeled EGFR-specific nanobody for in vivo monitoring of EGFR expression

PURPOSE

Overexpression of the epidermal growth factor receptor (EGFR) occurs with high incidence in various carcinomas. The oncogenic expression of the receptor has been exploited for immunoglobulin-based diagnostics and therapeutics. We describe the use of a llama single-domain antibody fragment, termed Nanobody, for the in vivo radioimmunodetection of EGFR overexpressing tumors using single photon emission computed tomography (SPECT) in mice.

METHODS

Fluorescence-activated cell sorting (FACS) analysis was performed to evaluate the specificity and selectivity of 8B6 Nanobody to bind EGFR on EGFR overexpressing cells. The Nanobody was then labeled with (99m)Tc via its C-terminal histidine tail. Uptake in normal organs and tissues was assessed by ex vivo analysis. In vivo tumor targeting of (99m)Tc-8B6 Nanobody was evaluated via pinhole SPECT in mice bearing xenografts of tumor cells with either high (A431) or moderate (DU145) overexpression of EGFR.

RESULTS

FACS analysis indicated that the 8B6 Nanobody only recognizes cells overexpressing EGFR. In vivo blood clearance of (99m)Tc-8B6 Nanobody is relatively fast (half-life, 1.5 h) and mainly via the kidneys. At 3 h postinjection, total kidney accumulation is high (46.6+/-0.9%IA) compared to total liver uptake (18.9+/-0.6%IA). Pinhole SPECT imaging of mice bearing A431 xenografts showed higher average tumor uptake (5.2+/-0.5%IA/cm(3)) of (99m)Tc-8B6 Nanobody compared to DU145 xenografts (1.8+/-0.3%IA/cm(3), p<0.001).

CONCLUSION

The EGFR-binding Nanobody investigated in this study shows high specificity and selectivity towards EGFR overexpressing cells. Pinhole SPECT analysis with (99m)Tc-8B6 Nanobody enabled in vivo discrimination between tumors with high and moderate EGFR overexpression. The favorable biodistribution further corroborates the suitability of Nanobodies for in vivo tumor imaging.

EGFR targeting of solid tumors

BACKGROUND

Recent clinical trials suggest that epidermal growth factor receptor (EGFR)-targeted agents could benefit many patients with cancer.

METHODS

We review the current status of several EGFR-targeted therapies in cancer patients and address the efficacy of theses drugs as monotherapy or in combination with other drugs and/or treatments.

RESULTS

Cetuximab is the most widely studied anti-EGFR monoclonal antibody. Other monoclonal antibody agents under investigation are panitumumab, matuzumab, MDX-447, nimutozumab, and mAb806. Extensive research has also evaluated the efficacy of EGFR tyrosine kinase inhibitors such as erlotinib, gefitinib, EKB-569, lapatinib (GW572016), PKI-166, and canertinib (CI-1033). All of these agents have been studied for the treatment of colorectal, lung, breast, pancreatic, renal, head and neck, gynecologic, and prostate cancer. Currently, cetuximab and panitumumab are FDA approved for the treatment of metastatic colorectal cancer. Additionally, cetuximab is approved for head and neck cancer. Erlotinib is FDA approved for advanced/metastatic lung cancer. Erlotinib in combination with gemcitabine is approved for advanced/metastatic pancreatic cancer treatment.

CONCLUSIONS

EGFR-targeted agents have already shown utility in different scenarios. Researchers are continuously investigating additional cancer types and combined treatment modalities that could also benefit from the use of EGFR-targeted agents. Careful patient selection through the identification of specific biologic markers, such as gene expression, genomic polymorphism, and posttranslational modifications of EGFR downstream effectors, most likely will contribute to the successful use of these agents.

Novel antibodies as anticancer agents

In recent years antibodies, whether generated by traditional hybridoma technology or by recombinant DNA strategies, have evolved from Paul Ehrlich's 'magic bullets' to a modern age 'guided missile'. In the recent years of immunologic research, we are witnessing development in the fields of antigen screening and protein engineering in order to create specific anticancer remedies. The developments in the field of recombinant DNA, protein engineering and cancer biology have let us gain insight into many cancer-related mechanisms. Moreover, novel techniques have facilitated tools allowing unique distinction between malignantly transformed cells, and regular ones. This understanding has paved the way for the rational design of a new age of pharmaceuticals: monoclonal antibodies and their fragments. Antibodies can select antigens on both a specific and a high-affinity account, and further implementation of these qualities is used to target cancer cells by specifically identifying exogenous antigens of cancer cell populations. The structure of the antibody provides plasticity resonating from its functional sites. This review will screen some of the many novel antibodies and antibody-based approaches that are being currently developed for clinical applications as the new generation of anticancer agents.