Predicting IGF-1R therapy response in bone sarcomas: immuno-SPECT imaging with radiolabeled R1507

Preclinical Evaluation of a New Format of 68Ga- and 111In-Labeled Affibody Molecule ZIGF-1R:4551 for the Visualization of IGF-1R Expression in Malignant Tumors Using PET and SPECT

The Insulin-like growth factor-1 receptor (IGF-1R) is a molecular target for several monoclonal antibodies undergoing clinical evaluation as anticancer therapeutics. The non-invasive detection of IGF-1R expression in tumors might enable stratification of patients for specific treatment and improve the outcome of both clinical trials and routine treatment. The affibody molecule Z_IGF-1R:4551 binds specifically to IGF-1R with subnanomolar affinity. The goal of this study was to evaluate the ⁶⁸Ga and ¹¹¹In-labeled affibody construct NODAGA-(HE)₃-Z_IGF-1R:4551 for the imaging of IGF-1R expression, using PET and SPECT. The labeling was efficient and provided stable coupling of both radionuclides. The two imaging probes, [⁶⁸Ga]Ga-NODAGA-(HE)₃-Z_IGF-1R:4551 and [¹¹¹In]In-NODAGA-(HE)₃-Z_IGF-1R:4551, demonstrated specific binding to IGF-1R-expressing human cancer cell lines in vitro and to IGF-1R-expressing xenografts in mice. Preclinical PET and SPECT/CT imaging demonstrated visualization of IGF-1R-expressing xenografts already one hour after injection. The tumor-to-blood ratios at 3 h after injection were 7.8 ± 0.2 and 8.0 ± 0.6 for [⁶⁸Ga]Ga-NODAGA-(HE)₃-Z_IGF-1R:4551 and [¹¹¹In]In-NODAGA-(HE)₃-Z_IGF-1R:4551, respectively. In conclusion, a molecular design of the Z_IGF-1R:4551 affibody molecule, including placement of a (HE)₃-tag on the N-terminus and site-specific coupling of a NODAGA chelator on the C-terminus, provides a tracer with improved imaging properties for visualization of IGF-1R in malignant tumors, using PET and SPECT.

Targeting the IGF/PI3K/mTOR Pathway and AXL/YAP1/TAZ pathways in Primary Bone Cancer

Primary bone cancers (PBC) belong to the family of mesenchymal tumors classified based on their cellular origin, extracellular matrix, genetic regulation, and epigenetic modification. The three major PBC types, Ewing sarcoma, osteosarcoma, and chondrosarcoma, are frequently aggressive tumors, highly metastatic, and typically occur in children and young adults. Despite their distinct origins and pathogenesis, these sarcoma subtypes rely upon common signaling pathways to promote tumor progression, metastasis, and survival. The IGF/PI3K/mTOR and AXL/YAP/TAZ pathways, in particular, have gained significant attention recently given their ties to oncogenesis, cell fate and differentiation, metastasis, and drug resistance. Naturally, these pathways – and their protein constituents – have caught the eye of the pharmaceutical industry, and a wide array of small molecule inhibitors and antibody drug-conjugates have emerged. Here, we review how the IGF/PI3K/mTOR and AXL/YAP/TAZ pathways promote PBC and highlight the drug candidates under clinical trial investigation.

Targeting the IGF-1R in prostate and colorectal cancer: reasons behind trial failure and future directions

IGF-1Rs enact a significant part in cancer growth and its progress. IGF-1R inhibitors were encouraged in the early trials, but the patients did not benefit due to the unavailability of predictive biomarkers and IGF-1R system complexity. However, the linkage between IGF-1R and cancer was reported three decades ago. This review will shed light on the IGF-1R system, targeting IGF-1R through monoclonal antibodies, reasons behind IGF-1R trial failure and future directions. This study presented that targeting IGF-1R through monoclonal antibodies is still effective in cancer treatment, and there is a need to look for future directions. Cancer patients may benefit from using mAbs that target existing and new cancer targets, evidenced by promising results. It is also essential that the academician, trial experts and pharmaceutical companies play their role in finding a treatment for this deadly disease.

Novel Receptor Tyrosine Kinase Pathway Inhibitors for Targeted Radionuclide Therapy of Glioblastoma

Glioblastoma (GB) remains the most fatal brain tumor characterized by a high infiltration rate and treatment resistance. Overexpression and/or mutation of receptor tyrosine kinases is common in GB, which subsequently leads to the activation of many downstream pathways that have a critical impact on tumor progression and therapy resistance. Therefore, receptor tyrosine kinase inhibitors (RTKIs) have been investigated to improve the dismal prognosis of GB in an effort to evolve into a personalized targeted therapy strategy with a better treatment outcome. Numerous RTKIs have been approved in the clinic and several radiopharmaceuticals are part of (pre)clinical trials as a non-invasive method to identify patients who could benefit from RTKI. The latter opens up the scope for theranostic applications. In this review, the present status of RTKIs for the treatment, nuclear imaging and targeted radionuclide therapy of GB is presented. The focus will be on seven tyrosine kinase receptors, based on their central role in GB: EGFR, VEGFR, MET, PDGFR, FGFR, Eph receptor and IGF1R. Finally, by way of analyzing structural and physiological characteristics of the TKIs with promising clinical trial results, four small molecule RTKIs were selected based on their potential to become new therapeutic GB radiopharmaceuticals.

Personalized medicine modality based on patient-derived xenografts from a malignant transformed GCTB harboring H3F3A G34W mutation

Background

The function of H3F3A G43W mutation, which has been observed in almost all GCTB, remains poorly characterized. Breakthrough in malignant GCTB has been trapped by the lack of clinical available drugs, limited canonical patient samples and paucity of fidelity preclinical models.

Methods

Tumor samples obtained from a malignant GCTB was implanted in immunodeficient mice for the generation of PDX. Histological examination and short tandem repeat (STR) were used for inherited features analyses. An epigenetic/transcriptional targeted compound library was selected for drug screening. The in vivo effects of selected drug were validated in PDX model.

Results

We established the PDX model with recurrent malignant GCTB specimens, histological examination and STR analyses revealed that PDX and their corresponding parental patients shared the same STRs and histologic features, suggesting common origins. ITF-2357 was the most significant compound with an IC50 lower than 0.1 uM. The results of the drug screening and in vivo PDX validation demonstrated that ITF-2357 might be a promising drug targeted H3F3A G34W mutation MGCTBs.

Conclusion

Our study demonstrates that PDX model maintained the same histologic and genetic features as those in the original patient. targeting HDAC through ITF-2357 effectively overcomes malignant GCTB progression in vitro and in vivo.

Translational potential statement

As PDX retain the principal histologic and genetic characteristics of the primary tumors, mad it a valuable research tool in predictive clinical efficacy. In this study, we first established a malignant GCTB PDX model, which might further accelerate the progress of drug development in malignant GCTB.

Imaging using radiolabelled targeted proteins: radioimmunodetection and beyond

The use of radiolabelled antibodies was proposed in 1970s for staging of malignant tumours. Intensive research established chemistry for radiolabelling of proteins and understanding of factors determining biodistribution and targeting properties. The use of radioimmunodetection for staging of cancer was not established as common practice due to approval and widespread use of [¹⁸F]-FDG, which provided a more general diagnostic use than antibodies or their fragments. Expanded application of antibody-based therapeutics renewed the interest in radiolabelled antibodies. RadioimmunoPET emerged as a powerful tool for evaluation of pharmacokinetics of and target engagement by biotherapeutics. In addition to monoclonal antibodies, new radiolabelled engineered proteins have recently appeared, offering high-contrast imaging of expression of therapeutic molecular targets in tumours shortly after injection. This creates preconditions for noninvasive determination of a target expression level and stratification of patients for targeted therapies. Radiolabelled proteins hold great promise to play an important role in development and implementation of personalised targeted treatment of malignant tumours. This article provides an overview of biodistribution and tumour-seeking features of major classes of targeting proteins currently utilized for molecular imaging. Such information might be useful for researchers entering the field of the protein-based radionuclide molecular imaging.

Modeling the Tumor Microenvironment and Pathogenic Signaling in Bone Sarcoma

Investigations of cancer biology and screening of potential therapeutics for efficacy and safety begin in the preclinical laboratory setting. A staple of most basic research in cancer involves the use of tissue culture plates, on which immortalized cell lines are grown in monolayers. However, this practice has been in use for over six decades and does not account for vital elements of the tumor microenvironment that are thought to aid in initiation, propagation, and ultimately, metastasis of cancer. Furthermore, information gleaned from these techniques does not always translate to animal models or, more crucially, clinical trials in cancer patients. Osteosarcoma (OS) and Ewing sarcoma (ES) are the most common primary tumors of bone, but outcomes for patients with metastatic or recurrent disease have stagnated in recent decades. The unique elements of the bone tumor microenvironment have been shown to play critical roles in the pathogenesis of these tumors and thus should be incorporated in the preclinical models of these diseases. In recent years, the field of tissue engineering has leveraged techniques used in designing scaffolds for regenerative medicine to engineer preclinical tumor models that incorporate spatiotemporal control of physical and biological elements. We herein review the clinical aspects of OS and ES, critical elements present in the sarcoma microenvironment, and engineering approaches to model the bone tumor microenvironment. Impact statement The current paradigm of cancer biology investigation and therapeutic testing relies heavily on monolayer, monoculture methods developed over half a century ago. However, these methods often lack essential hallmarks of the cancer microenvironment that contribute to tumor pathogenesis. Tissue engineers incorporate scaffolds, mechanical forces, cells, and bioactive signals into biological environments to drive cell phenotype. Investigators of bone sarcomas, aggressive tumors that often rob patients of decades of life, have begun to use tissue engineering techniques to devise in vitro models for these diseases. Their efforts highlight how critical elements of the cancer microenvironment directly affect tumor signaling and pathogenesis.

Monoclonal antibody-based molecular imaging strategies and theranostic opportunities

Molecular imaging modalities hold great potential as less invasive techniques for diagnosis and management of various diseases. Molecular imaging combines imaging agents with targeting moieties to specifically image diseased sites in the body. Monoclonal antibodies (mAbs) have become increasingly popular as novel therapeutics against a variety of diseases due to their specificity, affinity and serum stability. Because of the same properties, mAbs are also exploited in molecular imaging to target imaging agents such as radionuclides to the cell of interest in vivo. Many studies investigated the use of mAb-targeted imaging for a variety of purposes, for instance to monitor disease progression and to predict response to a specific therapeutic agent. Herein, we highlighted the application of mAb-targeted imaging in three different types of pathologies: autoimmune diseases, oncology and cardiovascular diseases. We also described the potential of molecular imaging strategies in theranostics and precision medicine. Due to the nearly infinite repertoire of mAbs, molecular imaging can change the future of modern medicine by revolutionizing diagnostics and response prediction in practically any disease.

Correlation between mouse age and human age in anti-tumor research: Significance and method establishment

Age is closely related with the occurrence and development of tumors, and with treatment outcomes. To improve the accuracy and rigor of preclinical studies, and to enhance consistency between the preclinical research and the clinical reality, the age of experimental animals used in preclinical studies is important. The mouse genome is 99% identical to the human genome, and mice have similar patterns with respect to organs and systemic physiology. Thus, mice have been the most widely used animals in anti-tumor research. However, most mice used in such studies are 6 to 8 weeks old, ignoring the fact that different tumors may often occur in various periods, with a particular tendency to occur in later stages of life. The great difference in age limits the success rate of clinical transformation. Therefore, it is very important to choose mice of suitable age for preclinical studies and to correlate ages of human and mice. Only a few related studies have been reported and there is a lack of consistency in the findings. This review points out that age is one of the important factors in anti-tumor research, and establishes a new method for calculating the age correlation between humans and mice. The equations obtained from the method can help researchers conveniently determine suitable aged mouse for their research, which will improve the rigor of their experimental results. Furthermore, this method can be used beyond anti-tumor research, in studies on other diseases that use mouse as an animal model.

Molecular Imaging of IGF-1R in Cancer

The important role of insulin-like growth factor 1 receptor (IGF-1R) in malignant tumors has been well established. Increased IGF-1R activity promotes cancer cell proliferation, migration, and invasion and is associated with tumor metastasis, treatment resistance, poor prognosis, and shortened survival in patients with cancer. However, while IGF-1R has become a promising target for cancer therapy, IGF-1R-targeted therapy is ineffective in unselected patients. It is therefore essential to evaluate IGF-1R expression before treatment in order to identify responsive patients, monitor therapy efficacy, and estimate prognosis. Insulin-like growth factor 1 receptor molecular imaging is an optimal method for assessing the expression of IGF-1R in vivo accurately and noninvasively. In this review, we will summarize the current status of IGF-1R molecular imaging in cancer, in which 5 major classes of ligands that have been developed for noninvasive IGF-1R molecular imaging will be discussed: natural ligands, monoclonal antibodies, antibody fragments, affibodies, and small molecules. For decades, IGF-1R molecular imaging is studied in full swing and more effort is needed in the future.

Cancer diagnostics: The journey from histomorphology to molecular profiling

Although histomorphology has made significant advances into the understanding of cancer etiology, classification and pathogenesis, it is sometimes complicated by morphologic ambiguities, and other shortcomings that necessitate the development of ancillary tests to complement its diagnostic value. A new approach to cancer patient management consists of targeting specific molecules or gene mutations in the cancer genome by inhibitory therapy. Molecular diagnostic tests and genomic profiling methods are increasingly being developed to identify tumor targeted molecular profile that is the basis of targeted therapy. Novel targeted therapy has revolutionized the treatment of gastrointestinal stromal tumor, renal cell carcinoma and other cancers that were previously difficult to treat with standard chemotherapy. In this review, we discuss the role of histomorphology in cancer diagnosis and management and the rising role of molecular profiling in targeted therapy. Molecular profiling in certain diagnostic and therapeutic difficulties may provide a practical and useful complement to histomorphology and opens new avenues for targeted therapy and alternative methods of cancer patient management.

Phosphoproteomic Profiling Reveals ALK and MET as Novel Actionable Targets across Synovial Sarcoma Subtypes

Despite intensive multimodal treatment of sarcomas, a heterogeneous group of malignant tumors arising from connective tissue, survival remains poor. Candidate-based targeted treatments have demonstrated limited clinical success, urging an unbiased and comprehensive analysis of oncogenic signaling networks to reveal therapeutic targets and personalized treatment strategies. Here we applied mass spectrometry-based phosphoproteomic profiling to the largest and most heterogeneous set of sarcoma cell lines characterized to date and identified novel tyrosine phosphorylation patterns, enhanced tyrosine kinases in specific subtypes, and potential driver kinases. ALK was identified as a novel driver in the Aska-SS synovial sarcoma (SS) cell line via expression of an ALK variant with a large extracellular domain deletion (ALKΔ2-17). Functional ALK dependency was confirmed in vitro and in vivo with selective inhibitors. Importantly, ALK immunopositivity was detected in 6 of 43 (14%) of SS patient specimens, one of which exhibited an ALK rearrangement. High PDGFRα phosphorylation also characterized SS cell lines, which was accompanied by enhanced MET activation in Yamato-SS cells. Although Yamato-SS cells were sensitive to crizotinib (ALK/MET-inhibitor) but not pazopanib (VEGFR/PDGFR-inhibitor) monotherapy in vitro, synergistic effects were observed upon drug combination. In vivo, both drugs were individually effective, with pazopanib efficacy likely attributable to reduced angiogenesis. MET or PDGFRα expression was detected in 58% and 84% of SS patients, respectively, with coexpression in 56%. Consequently, our integrated approach has led to the identification of ALK and MET as promising therapeutic targets in SS. Cancer Res; 77(16); 4279-92. ©2017 AACR.

In vivo evaluation of IGF1R/IR PET ligand [18F]BMS-754807 in rodents

In vivo evaluation of [¹⁸F]BMS-754807 binding in mice and rats using microPET and biodistribution methods is described herein. The radioligand shows consistent binding characteristics, in vivo, in both species. Early time frames of the microPET images and time activity curves of brain indicate poor penetration of the tracer across the blood brain barrier (BBB) in both species. However, microPET experiments in mice and rats show high binding of the radioligand outside the brain to heart, pancreas and muscle, the organs known for higher expression of IGF1R/1R. Biodistribution analysis 2h after injection of [¹⁸F]BMS-754807 in rats show negligible [¹⁸F]defluorination as reflected by the low bone uptake and clearance from blood. Overall, the data indicate that [¹⁸F]BMS-754807 can potentially be a radiotracer for the quantification of IGF1R/IR outside the brain using PET.

The role of AXL and the in vitro activity of the receptor tyrosine kinase inhibitor BGB324 in Ewing sarcoma

New targets for Ewing sarcoma (ES) patients are urgently needed. Therefore, we investigated the expression and genetic aberrations of the oncogenic receptor tyrosine kinase (RTK) AXL in ES and determined the efficacy of AXL targeting on cell viability and migration. First, AXL and Gas6 (ligand) mRNA expression was determined by RT-PCR on 29 ES samples. Low, medium and high AXL mRNA expression was observed in 31% (n = 9), 48% (n = 14) and 21% (n = 6) of samples. Gas6 was abundantly present in all specimens. We next tested AXL protein expression immunohistochemically in 36 tumors (primary, post-chemotherapy, metastasized and relapsed samples) from 25 ES patients. Low, medium and high AXL protein expression was observed in 17% (n = 6), 19% (n = 7) and 36% (n = 13) of samples. In primary tumors (n = 15), high AXL expression correlated significantly with a worse overall survival compared to patients with lower expression (61 vs. 194 months, p = 0.026). No genetic aberrations were detected in the AXL RTK domain (n = 29). The AXL-inhibitor BGB324 affected viability (IC50 0.79-2.13 μmol/L) and migratory potential of all tested ES cell lines in vitro (n = 5-6). BGB324 chemosensitized chemotherapy-resistant ES-4 cells to vincristine and doxorubicin. These data suggest that AXL is a potential novel, druggable therapeutic target in ES.

PET imaging of insulin-like growth factor type 1 receptor expression with a 64Cu-labeled Affibody molecule

The insulin-like growth factor 1 receptor (IGF-1R) serves as an attractive target for cancer molecular imaging and therapy. Previous single photon emission computerized tomography (SPECT) studies showed that the IGF-1R-targeting Affibody molecules (99m)Tc-ZIGF1R:4551-GGGC, [(99m)Tc(CO)3](+)-(HE)3-ZIGF1R:4551 and (111)In-DOTA-ZIGF1R:4551 can discriminate between high and low IGF-1R-expression tumors and have the potential for patient selection for IGF-1R-targeted therapy. Compared with SPECT, positron emission tomography (PET) may improve imaging of IGF-1R-expression, because of its high sensitivity, high spatial resolution, strong quantification ability. The aim of the present study was to develop the (64)Cu-labeled NOTA-conjugated Affibody molecule ZIGF-1R:4:40 as a PET probe for imaging of IGF-1R-positive tumor. An Affibody analogue (Ac-Cys-ZIGF-1R:4:40) binding to IGF-1R was site-specifically conjugated with NOTA and labeled with (64)Cu. Binding affinity and specificity of (64)Cu-NOTA-ZIGF-1R:4:40 to IGF-1R were evaluated using human glioblastoma U87MG cells. Small-animal PET, biodistribution, and metabolic stability studies were conducted on mice bearing U87MG xenografts after the injection of (64)Cu-NOTA-ZIGF-1R:4:40 with or without co-injection of unlabeled Affibody proteins. The radiosynthesis of (64)Cu-NOTA-ZIGF-1R:4:40 was completed successfully within 60 min with a decay-corrected yield of 75 %. (64)Cu-NOTA-ZIGF-1R:4:40 bound to IGF-1R with low nanomolar affinity (K D = 28.55 ± 3.95 nM) in U87MG cells. (64)Cu-NOTA-ZIGF-1R:4:40 also displayed excellent in vitro and in vivo stability. In vivo biodistribution and PET studies demonstrated targeting of U87MG gliomas xenografts was IGF-1R specific. The tumor uptake was 5.08 ± 1.07 %ID/g, and the tumor to muscle ratio was 11.89 ± 2.16 at 24 h after injection. Small animal PET imaging studies revealed that (64)Cu-NOTA-ZIGF-1R:4:40 could clearly identify U87MG tumors with good contrast at 1-24 h after injection. This study demonstrates that (64)Cu-NOTA-ZIGF-1R:4:40 is a promising PET probe for imaging IGF-1R positive tumor.

Dynamics of IGF-1R expression during endocrine breast cancer treatment

PURPOSE

The aim was to assess changes in insulin-like growth factor 1 receptor (IGF-1R) expression with immunoSPECT/CT and to study the dynamics of IGF-1R expression of human breast tumors during endocrine treatment.

PROCEDURES

Mice with MCF-7 xenografts were treated with estradiol or tamoxifen, and IGF-1R expression was measured by immunohistochemistry and immunoSPECT/CT using (111)In-R1507 (anti-IGF-1R antibody). Moreover, IGF-1R expression was analyzed immunohistochemically on 22 human breast tumors, treated preoperatively with endocrine therapy.

RESULTS

Estradiol resulted in an increased expression of IGF-1R, as measured by immunohistochemistry and immunoSPECT/CT. In contrast, tamoxifen resulted in a downregulation of IGF-1R, whereas this could not be measured with immunoSPECT/CT. A downregulation was also detectable in 9 out of 22 (41 %) human breast tumors after endocrine therapy.

CONCLUSIONS

Anti-estrogen treatment can cause a reduction in membranous IGF-1R expression. Based on these results, a combination of anti-IGF-1R antibodies with anti-estrogen therapy might not be a rational treatment strategy.

Evaluation of 99mTc-Z IGF1R:4551-GGGC affibody molecule, a new probe for imaging of insulin-like growth factor type 1 receptor expression

Overexpression of insulin-like growth factor-1 receptor (IGF-1R) in several cancers is associated with resistance to therapy. Radionuclide molecular imaging of IGF-1R expression in tumors may help in selecting the patients that will potentially respond to IGF-1R-targeted therapy. Affibody molecules are small (7 kDa) non-immunoglobulin-based scaffold proteins that are well-suited probes for radionuclide imaging. The aim of this study was the evaluation of an anti-IGF-1R affibody molecule labeled with technetium-99m using cysteine-containing peptide-based chelator GGGC at C-terminus. Z_IGF1R:4551-GGGC was efficiently and stably labeled with technetium-99m (radiochemical yield 97 ± 3 %). ^99mTc-Z_IGF1R:4551-GGGC demonstrated specific binding to IGF-1R-expressing DU-145 (prostate cancer) and MCF-7 (breast cancer) cell lines and slow internalization in vitro. The tumor-targeting properties were studied in BALB/c nu/nu mice bearing DU-145 and MCF-7 xenografts. [^99mTc(CO)₃]⁺-(HE)₃-Z_IGF1R:4551 was used for comparison. The biodistribution study demonstrated high tumor-to-blood ratios (6.2 ± 0.9 and 6.9 ± 1.0, for DU-145 and MCF-7, respectively, at 4 h after injection). Renal radioactivity concentration was 16-fold lower for ^99mTc-Z_IGF1R:4551-GGGC than for [^99mTc(CO)₃]⁺-(HE)₃-Z_IGF1R:4551 at 4 h after injection. However, the liver uptake of ^99mTc-Z_IGF1R:4551-GGGC was 1.2- to 2-fold higher in comparison with [^99mTc(CO)₃]⁺-(HE)₃-Z_IGF1R:4551. A possible reason for the elevated hepatic uptake of ^99mTc-Z_IGF1R:4551-GGGC is a high lipophilicity of amino acids in the binding site of Z_IGF1R:4551, which is not compensated in ^99mTc-Z_IGF1R:4551-GGGC. In conclusion, ^99mTc-Z_IGF1R:4551-GGGC can visualize the IGF-1R expression in human tumor xenografts and provides low retention of radioactivity in kidneys. Further development of this imaging agent should include molecular design aimed at reducing the hepatic uptake.

Generation and screening of monoclonal antibodies for immunoPET imaging of IGF1R in prostate cancer

Insulin-like growth factor 1 receptor (IGF1R) plays an important role in proliferation, apoptosis, angiogenesis, and tumor invasion. The expression level of IGF1R is related to resistance to several targeted therapies. The goal of this study was to develop an immunoPET tracer for imaging of IGF1R in prostate cancer. Murine antibodies against human IGF1R were generated in BALB/c mice, which were screened in IGF1R-positive MCF-7 cells using flow cytometry as well as biodistribution studies with multiple (64)Cu-labeled antibody clones. The antibody production method we adopted could readily produce milligram quantities of anti-IGF1R antibodies for in vivo studies. One antibody clone (1A2G11) with the highest affinity for IGF1R was selected and conjugated to NOTA for (64)Cu-labeling. NOTA-1A2G11 maintained IGF1R specificity/avidity based on flow cytometry. (64)Cu-labeling was achieved with good yield (>50%) and high specific activity (>1 Ci/μmol). Serial PET imaging revealed that uptake of (64)Cu-NOTA-1A2G11 was 2.8 ± 0.7, 10.2 ± 2.6, and 9.6 ± 1.7 %ID/g in IGF1R-positive DU-145 tumors at 4, 24, and 48 h postinjection, respectively (n = 3), significantly higher than that in IGF1R-negative LNCaP tumors (<3 %ID/g at each time point) except at 4 h postinjection. Histology studies showed strong correlations between IGF1R expression level in the prostate cancer tumor tissues and tumor uptake of (64)Cu-NOTA-1A2G11. Prominent, persistent, and IGF1R-specific uptake of (64)Cu-NOTA-1A2G11 in IGF1R-positive prostate tumors holds strong potential for future cancer diagnosis, prognosis, and therapy using this antibody.

Insulin-like growth factor 1 receptor and response to anti-IGF1R antibody therapy in osteosarcoma

Background

Survival outcomes for patients with osteosarcoma (OS) have remained stagnant over the past three decades. Insulin-like growth factor 1 receptor (IGF1R) is over-expressed in a number of malignancies, and anti-IGF1R antibodies have and are currently being studied in clinical trials. Understanding the molecular aberrations which result in increased tumor response to anti-IGF1R therapy could allow for the selection of patients most likely to benefit from IGF1R targeted therapy.

Methods

IGF1R mRNA expression was assessed by RT PCR in OS patient primary tumors, cell lines, and xenograft tumors. IGF1R copy number was assessed by 3 approaches: PCR, FISH, and dot blot analysis. Exons 1–20 of IGF1R were sequenced in xenograft tumors and 87 primary OS tumors, and surface expression of IGF1R was assessed by flow cytometry. Levels of mRNA and protein expression, copy number, and mutation status were compared with tumor response to anti-IGF1R antibody therapy in 4 OS xenograft models.

Results

IGF1R mRNA is expressed in OS. Primary patient samples and xenograft samples had higher mRNA expression and copy number compared with corresponding cell lines. IGF1R mRNA expression, cell surface expression, copy number, and mutation status were not associated with tumor responsiveness to anti-IGF1R antibody therapy.

Conclusions

IGF1R is expressed in OS, however, no clear molecular markers predict response to IGF1R antibody-mediated therapy. Additional pre-clinical studies assessing potential predictive biomarkers and investigating targetable molecular pathways critical to the proliferation of OS cells are needed.

Can we unlock the potential of IGF-1R inhibition in cancer therapy?

IGF-1R inhibitors arrived in the clinic accompanied by optimism based on preclinical activity of IGF-1R targeting, and recognition that low IGF bioactivity protects from cancer. This was tempered by concerns about toxicity to normal tissue IGF-1R and cross-reactivity with insulin receptor (InsR). In fact, toxicity is not a show-stopper; the key issue is efficacy. While IGF-1R inhibition induces responses as monotherapy in sarcomas and with chemotherapy or targeted agents in common cancers, negative Phase 2/3 trials in unselected patients prompted the cessation of several Pharma programs. Here, we review completed and on-going trials of IGF-1R antibodies, kinase inhibitors and ligand antibodies. We assess candidate biomarkers for patient selection, highlighting the potential predictive value of circulating IGFs/IGFBPs, the need for standardized assays for IGF-1R, and preclinical evidence that variant InsRs mediate resistance to IGF-1R antibodies. We review hypothesis-led and unbiased approaches to evaluate IGF-1R inhibitors with other agents, and stress the need to consider sequencing with chemotherapy. The last few years were a tough time for IGF-1R therapeutics, but also brought progress in understanding IGF biology. Even failed studies include patients who derived benefit; they should be investigated to identify features distinguishing the tumors and host environment of responders from non-responders. We emphasize the importance of incorporating biospecimen collection into trial design, and wording patient consents to allow post hoc analysis of trial material as new data become available. Such information represents the key to unlocking the potential of this approach, to inform the next generation of trials of IGF signalling inhibitors.

A phase 2 trial of R1507, a monoclonal antibody to the insulin-like growth factor-1 receptor (IGF-1R), in patients with recurrent or refractory rhabdomyosarcoma, osteosarcoma, synovial sarcoma, and other soft tissue sarcomas: results of a Sarcoma Alliance for Research Through Collaboration study

BACKGROUND

Insulin-like growth factor-1 receptor (IGF-1R) is implicated in the pathogenesis of rhabdomyosarcoma (RMS), osteosarcoma (OS), and synovial sarcoma (SS). The authors conducted a multi-institutional phase 2 trial of the monoclonal antibody R1507 in patients with various subtypes of recurrent or refractory sarcomas.

METHODS

Eligibility criteria included age ≥ 2 years and a diagnosis of recurrent or refractory RMS, OS, SS, and other soft tissue sarcomas. Patients received a weekly dose of 9 mg/kg R1507 intravenously. The primary endpoint was the best objective response rate using World Health Organization criteria. Tumor imaging was performed every 6 weeks × 4 and every 12 weeks thereafter.

RESULTS

From December 2007 through August 2009, 163 eligible patients from 33 institutions were enrolled. The median patient age was 31 years (range, 7-85 years). Histologic diagnoses included OS (n = 38), RMS (n = 36), SS (n = 23), and other sarcomas (n = 66). The overall objective response rate was 2.5% (95% confidence interval, 0.7%-6.2%). Partial responses were observed in 4 patients, including 2 patients with OS, 1 patient with RMS, and 1 patient with alveolar soft part sarcoma. Four additional patients (3 with RMS and 1 with myxoid liposarcoma) had a ≥ 50% decrease in tumor size that lasted for <4 weeks. The median progression-free survival was 5.7 weeks, and the median overall survival was 11 months. The most common grade 3/4 toxicities were metabolic (12%), hematologic (6%), gastrointestinal (4%), and general constitutional symptoms (8%).

CONCLUSIONS

R1507 is safe and well tolerated but has limited activity in patients with recurrent or refractory bone and soft tissue sarcomas. Additional studies to help identify the predictive factors associated with clinical benefit in selected histologies such as RMS appear to be warranted.

Theranostic applications of antibodies in oncology

Targeted therapies, including antibodies, are becoming increasingly important in cancer therapy. Important limitations, however, are that not every patient benefits from a specific antibody therapy and that responses could be short-lived due to acquired resistance. In addition, targeted therapies are quite expensive and are not completely devoid of side-effects. This urges the need for accurate patient selection and response monitoring. An important step towards personalizing antibody treatment could be the implementation of theranostics. Antibody theranostics combine the diagnostic and therapeutic potential of an antibody, thereby selecting those patients who are most likely to benefit from antibody treatment. This review focuses on the clinical application of theranostic antibodies in oncology. It provides detailed information concerning the suitability of antibodies for theranostics, the different types of theranostic tests available and summarizes the efficacy of theranostic antibodies used in current clinical practice. Advanced theranostic applications, including radiolabeled antibodies for non-invasive functional imagining, are also addressed. Finally, we discuss the importance of theranostics in the emerging field of personalized medicine and critically evaluate recent data to determine the best way to apply antibody theranostics in the future.

Targeting receptor tyrosine kinases in osteosarcoma and Ewing sarcoma: current hurdles and future perspectives

Osteosarcoma (OS) and Ewing sarcoma (ES) are the two most common types of primary bone cancer, which mainly affect children and young adults. Despite intensive multi-modal treatment, the survival of both OS and ES has not improved much during the last decades and new therapeutic options are awaited. One promising approach is the specific targeting of transmembrane receptor tyrosine kinases (RTKs) implicated in these types of bone cancer. However, despite encouraging in vitro and in vivo results, apart from intriguing results of Insulin-like Growth Factor-1 Receptor (IGF-1R) antibodies in ES, clinical studies are limited or disappointing. Primary resistance to RTK inhibitors is frequently observed in OS and ES patients, and even patients that initially respond well eventually develop acquired resistance. There are, however, a few remarks to make concerning the current set-up of clinical trials and about strategies to improve RTK-based treatments in OS and ES. This review provides an overview concerning current RTK-mediated therapies in OS and ES and discusses the problems observed in the clinic. More importantly, we describe several strategies to overcome resistance to RTK inhibitors which may significantly improve outcome of OS and ES patients.

IGF-IR Targeted Therapy: Past, Present and Future

The IGF-I receptor (IGF-IR) has been studied as an anti-cancer target. However, monotherapy trials with IGF-IR targeted antibodies or with IGF-IR specific tyrosine kinase inhibitors have, overall, been very disappointing in the clinical setting. This review discusses potential reasons why IGF-I R targeted therapy fails to inhibit growth of human cancers. It has become clear that intracellular signaling pathways are highly interconnected and complex instead of being linear and simple. One of the most potent candidates for failure of IGF-IR targeted therapy is the insulin receptor isoform A (IR-A). Activation of the IR-A by insulin-like growth factor-II (IGF-II) bypasses the IGF-IR and its inhibition. Another factor may be that anti-cancer treatment may reduce IGF-IR expression. IGF-IR blocking drugs may also induce hyperglycemia and hyperinsulinemia, which may further stimulate cell growth. In addition, circulating IGF-IRs may reduce therapeutic effects of IGF-IR targeted therapy. Nevertheless, it is still possible that the IGF-IR may be a useful adjuvant or secondary target for the treatment of human cancers. Development of functional inhibitors that affect the IGF-IR and IR-A may be necessary to overcome resistance and to make IGF-IR targeted therapy successful. Drugs that modify alternative downstream effects of the IGF-IR, so called "biasing agonists," should also be considered.

IGF signaling pathway analysis of osteosarcomas reveals the prognostic value of pAKT localization

Aim: The aim of this study was to examine the expression of the IGF signaling pathway components in osteosarcoma samples before and after chemotherapy with special emphasis on their prognostic value. Materials & methods: Tumor material and follow-up data of 58 osteosarcoma patients were analyzed. Immunohistochemical staining was carried out to identify proteins related to the IGF pathway. Changes in protein expression during treatment, correlations between proteins and subsequent influence on survival were tested. Results: Proteins of the IGF signaling system are widely expressed in osteosarcoma samples. We demonstrate a change in expression of intracellular pathway proteins after chemotherapy. Remarkably, cytoplasmic pAKT, but not nuclear pAKT, is associated with poor survival. Conclusion: IGF pathway proteins seem to be widely activated in osteosarcoma, but their expression changes after chemotherapy. This has implications for the timing of both measuring target expression and pathway interference. Our observations on the prognostic value of cytoplasmic pAKT warrant further investigation while considering the introduction of AKT inhibitors for osteosarcoma treatment.

Synthesis and in vitro evaluation of [18F]BMS-754807: a potential PET ligand for IGF-1R

Radiosynthesis and in vitro evaluation of [(18)F](S)-1-(4-((5-cyclopropyl-1H-pyrazol-3-yl)amino)pyrrolo[2,1-f][1,2,4]triazin-2-yl)-N-(6-fluoropyridin-3-yl)-2-methylpyrrolidine-2-carboxamide ([(18)F]BMS-754807 or [(18)F]1) a specific IGF-1R inhibitor was performed. [(18)F]1 demonstrated specific binding in vitro to human cancer tissues. Synthesis of reference standard 1 and corresponding bromo derivative (1a), the precursor for radiolabeling were achieved from 2,4-dichloropyrrolo[2,1-f][1,2,4]triazine (4) in three steps with 50% overall yield. The radioproduct was obtained in 8% yield by reacting 1a with [(18)F]TBAF in DMSO at 170°C at high radiochemical purity and specific activity (1-2Ci/μmol, N=10). The proof of concept of IGF-IR imaging with [(18)F]1 was demonstrated by in vitro autoradiography studies using pathologically identified surgically removed grade IV glioblastoma, breast cancer and pancreatic tumor tissues. These studies indicate that [(18)F]1 can be a potential PET tracer for monitoring IGF-1R.

The strength of small: improved targeting of insulin-like growth factor-1 receptor (IGF-1R) with F(ab')₂-R1507 fragments in Ewing sarcomas

PURPOSE

To investigate whether F(ab')₂-fragments of the monoclonal Insulin-like Growth Factor-1 Receptor (IGF-1R) antibody R1507 (F(ab')₂-R1507) can successfully target IGF-1R in Ewing sarcomas (ES).

MATERIALS AND METHODS

BALB/c nude mice were subcutaneously implanted with IGF-1R-expressing human ES xenografts (EW-5 and EW-8) which previously showed heterogeneous or no uptake of indium-111-labelled R1507 IgG ((111)In-R1507), respectively. Mice were injected with (111)In-F(ab')₂-R1507 or (111)In-R1507 as a reference. Biodistribution and immuno-SPECT/computed tomography (CT) imaging studies were carried out 2, 4, 8 and 24 h post-injection (p.i.) for (111)In-F(ab')₂-R1507 and 24 h p.i. for (111)In-R1507.

RESULTS

Biodistribution studies showed specific accumulation of (111)In-F(ab')₂-R1507 in EW-5 xenografts from t=2 h p.i. onwards (3.6 ± 0.2%ID/g at t = 24 h p.i.) and (111)In-F(ab')₂-R1507 immuno-SPECT showed almost homogeneous intratumoural distribution at t=24h p.i. Tumour-to-blood ratios of (111)In-F(ab')₂-R1507 were significantly higher than those of (111)In-R1507 at t=24 h p.i. (2.4 ± 0.4 versus 0.5 ± 0.1, respectively; p<0.05). More importantly, (111)In-F(ab')₂-R1507 also specifically accumulated in EW-8 tumours (3.7 ± 0.7%ID/g at t = 24 h p.i). In both EW-5 and EW-8 tumours, there was a good spatial correlation between IGF-1R expression and (111)In-F(ab')₂-R1507 tumour distribution.

CONCLUSION

(111)In-F(ab')₂-R1507 fragments can successfully target IGF-1R in ES models and have superior tumour penetrating and IGF-1R-targeting properties as compared to (111)In-R1507. This suggests that anti-IGF-1R therapies in ES and other tumours may be improved by using smaller therapeutic compounds, although further in vivo studies addressing this topic are warranted.

Antibody biodistribution coefficients: inferring tissue concentrations of monoclonal antibodies based on the plasma concentrations in several preclinical species and human

Tissue vs. plasma concentration profiles have been generated from a physiologically-based pharmacokinetic model of monoclonal antibody (mAb). Based on the profiles, we hypothesized that a linear relationship between the plasma and tissue concentrations of non-binding mAbs could exist; and that the relationship may be generally constant irrespective of the absolute mAb concentration, time, and animal species being analyzed. The hypothesis was verified for various tissues in mice, rat, monkey, and human using mAb or antibody-drug conjugate tissue distribution data collected from diverse literature. The relationship between the plasma and various tissue concentrations was mathematically characterized using the antibody biodistribution coefficient (ABC). Estimated ABC values suggest that typically the concentration of mAb in lung is 14.9%, heart 10.2%, kidney 13.7%, muscle 3.97%, skin 15.7%, small intestine 5.22%, large intestine 5.03%, spleen 12.8%, liver 12.1%, bone 7.27%, stomach 4.98%, lymph node 8.46%, adipose 4.78%, brain 0.351%, pancreas 6.4%, testes 5.88%, thyroid 67.5% and thymus is 6.62% of the plasma concentration. The validity of using the ABC to predict mAb concentrations in different tissues of mouse, rat, monkey, and human species was evaluated by generating validation data sets, which demonstrated that predicted concentrations were within 2-fold of the observed concentrations. The use of ABC to infer tissue concentrations of mAbs and related molecules provides a valuable tool for investigating preclinical or clinical disposition of these molecules. It can also help eliminate or optimize biodistribution studies, and interpret efficacy or toxicity of the drug in a particular tissue.

New systemic therapy options for advanced sarcomas

The outcome of patients with advanced soft tissue sarcomas (STS) has not improved much during the last decade. Apart from non-pleomorphic rhabdomyosarcoma, adjuvant chemotherapy has no standard role in high risk STS. In metastatic disease little progress has been made, but during recent years much effort has been put into the development of better clinical study protocols, with stratification of patients to at least the most common histological subtypes, preventing the dilution of potential treatment efficacy when measuring results over the total heterogeneous group of STS. The outcome of patients with advanced STS is however not only dependent on the introduction of new drugs, but also on the availability of dedicated sarcoma centers in which multidisciplinary teams with the input of all experts from different disciplines, such as pathology, radiology, nuclear medicine, surgery, orthopedics radiotherapy and medical oncology is present. Long delay, wrong histological diagnoses, under- and overtreatment are not in the favor of these patients, neither with regard to outcome, nor with respect to short- and long-term toxicity. Disappointedly, centralization is not a routine part of daily care of STS patients and their care givers. Patient advocacy groups are more and more aware of the relevance of treatment in centers of expertise and are active in guiding the patients to these hospitals. At the same time the sarcoma centers should be pro-active in putting patients into clinical trials, also for rare indications within the STS group, as only in this way a better outcome for this group of patients can be reached.

[99mTc(CO)3]+-(HE)3-ZIGF1R:4551, a new Affibody conjugate for visualization of insulin-like growth factor-1 receptor expression in malignant tumours

PURPOSE

Radionuclide imaging of insulin-like growth factor type 1 receptor (IGF-1R) expression in tumours might be used for selection of patients who would benefit from IGF-1R-targeted therapy. We have previously shown the feasibility of IGF-1R imaging using the Affibody molecule (111)In-DOTA-His(6)-Z(IGF1R:4551). The use of (99m)Tc instead of (111)In should improve sensitivity and resolution of imaging, and reduce the dose burden to patients. We hypothesized that inclusion of a HEHEHE tag instead of a His(6) tag in Z(IGF1R:4551) would permit its convenient purification using IMAC, enable labelling with [(99m)Tc(CO)(3)](+), and improve its biodistribution.

METHODS

Z(IGF1R:4551) was expressed with a HEHEHE tag in the N terminus. The resulting (HE)(3)-Z(IGF1R:4551) construct was labelled with [(99m)Tc(CO)(3)](+). Targeting of IGF-1R-expressing cells using [(99m)Tc(CO)(3)](+)-(HE)(3)-Z(IGF1R:4551) was evaluated in vitro and in vivo.

RESULTS

(HE)(3)-Z(IGF1R:4551) was stably labelled with (99m)Tc with preserved specific binding to IGF-1R-expressing DU-145 prostate cancer cells in vitro. In mice, [(99m)Tc(CO)(3)](+)-(HE)(3)-Z(IGF1R:4551) accumulated in IGF-1R-expressing organs (pancreas, stomach, lung and salivary gland). [(99m)Tc(CO)(3)](+)-(HE)(3)-Z(IGF1R:4551) demonstrated 3.6-fold lower accumulation in the liver and spleen than (111)In-DOTA-Z(IGF1R:4551). In NMRI nu/nu mice with DU-145 prostate cancer xenografts, the tumour uptake was 1.32 ± 0.11 %ID/g and the tumour-to-blood ratio was 4.4 ± 0.3 at 8 h after injection. The xenografts were visualized using a gamma camera 6 h after injection.

CONCLUSION

(99m)Tc(CO)(3)](+)-(HE)(3)-Z(IGF1R:4551) is a promising candidate for visualization of IGF-1R expression in malignant tumours.

Advances in immuno-positron emission tomography: antibodies for molecular imaging in oncology

Identification of cancer cell-surface biomarkers and advances in antibody engineering have led to a sharp increase in the development of therapeutic antibodies. These same advances have led to a new generation of radiolabeled antibodies and antibody fragments that can be used as cancer-specific imaging agents, allowing quantitative imaging of cell-surface protein expression in vivo. Immuno-positron emission tomography (immunoPET) imaging with intact antibodies has shown success clinically in diagnosing and staging cancer. Engineered antibody fragments, such as diabodies, minibodies, and single-chain Fv (scFv) -Fc, have been successfully employed for immunoPET imaging of cancer cell-surface biomarkers in preclinical models and are poised to bring same-day imaging into clinical development. ImmunoPET can potentially provide a noninvasive approach for obtaining target-specific information useful for titrating doses for radioimmunotherapy, for patient risk stratification and selection of targeted therapies, for evaluating response to therapy, and for predicting adverse effects, thus contributing to the ongoing development of personalized cancer treatment.

Prospects and challenges for the development of new therapies for Ewing sarcoma

The Ewing sarcoma family of tumors or Ewing sarcoma (ES) is the second most common malignant bone tumor of childhood. The prognosis for localized Ewing sarcoma has improved through the development of intense multimodal therapy over the past several decades. Unfortunately, patients with recurrent or metastatic disease continue to have a poor prognosis. Therefore, a number of complementary approaches are being developed in both the preclinical and clinical arenas to improve these outcomes. In this review, we will discuss efforts to directly target the biologic drivers of this disease and relate these efforts to the experience with several different agents both in the clinic and under development. We will review the data for compounds that have shown excellent activity in the clinic, such as the camptothecins, and summarize the biological data that supports this activity. In addition, we will review the clinical experience with IGF1 targeted agents, ET-743 and epigenetically targeted therapies, the substantial amount of literature that supports their activity in Ewing sarcoma and the challenges remaining translating these therapies to the clinic. Finally, we will highlight recent work aimed at directly targeting the EWS-FLI1 transcription factor with small molecules in Ewing tumors.

Optimization of IGF-1R SPECT/CT imaging using 111In-labeled F(ab')2 and Fab fragments of the monoclonal antibody R1507

The insulin-like growth factor 1 receptor (IGF-1R) is a potential new target for the treatment of breast cancer. Patients with breast cancer lesions that express IGF-1R may benefit from treatment with anti-IGF-1R antibodies. IGF-1R expression can be visualized using radiolabeled R1507, a monoclonal antibody directed against IGF-1R. However, antibodies clear slowly from the circulation, resulting in low tumor-to-background ratios early after injection. Therefore, we aimed to accelerate targeting of IGF-1R using radiolabeled R1507 F(ab')2 and Fab fragments. In vitro, immunoreactivity, binding affinity and internalization of R1507 IgG, F(ab')2 and Fab were determined using the triple negative IGF-1R-expressing breast cancer cell line SUM149. In vivo, pharmacokinetics of (111)In-labeled R1507 IgG, F(ab')2 and Fab were studied in mice bearing subcutaneous SUM149 xenografts. SPECT/CT images were acquired and the biodistribution was measured ex vivo. The in vitro binding characteristics of radiolabeled R1507 IgG and F(ab')2 were comparable, whereas the affinity of Fab fragments was significantly lower (Kd: 0.6 nM, 0.7 nM and 3.0 nM for R1507 IgG, F(ab')2 and Fab, respectively). Biodistribution studies showed that the maximum tumor uptake of (111)In-R1507 IgG, F(ab')2 and Fab was 31.8% ID/g (72 h p.i.), 10.0% ID/g (6 h p.i.), and 1.8% ID/g (1 h p.i.), respectively. However, maximal tumor-to-blood ratios for F(ab')2 (24 h p.i.: 7.5) were more than twice as high as those obtained with R1507 (72 h p.i.: 2.8) and Fab (6 h p.i.: 2.8). Injection of an excess of unlabeled R1507 significantly reduced tumor uptake, suggesting that the uptake of R1507 IgG and F(ab')2 was specific for IGF-1R, while the major fraction of the tumor uptake of Fab was nonspecific. IGF-1R-expressing xenografts were visualized with (111)In-F(ab')2 SPECT/CT as early as 6 h p.i., while with R1507 IgG, the tumor could be visualized after 24 h. No specific targeting was observed with (111)In-Fab. (111)In-F(ab')2 fragments showed improved targeting of IGF-1R expressing tumors. Tumor-to-blood ratios were twice as high as those obtained with (111)In-R1507, and adequate tumor targeting on SPECT/CT images was observed as early as 6 h p.i. For individualization and optimization of IGF-1R targeted therapy, (111)In-F(ab')2 may be the tracer of choice.

Molecular imaging of insulin-like growth factor 1 receptor in cancer

Insulin-like growth factor 1 receptor (IGF1R) plays an important role in proliferation, apoptosis, angiogenesis, and tumor invasion. Histology and in situ hybridization studies have revealed that IGF1R was significantly up-regulated at the protein and mRNA level in many types of cancer. Since measuring IGF1R expression with immunohistochemistry has many limitations, non-invasive imaging of IGF1R can allow for more accurate patient stratification (e.g. selecting the right patient population for IGF1R-targeted therapy) and more effective monitoring of the therapeutic responses in cancer patients. In this review, we will summarize the current status of imaging IGF1R expression in cancer, which includes single-photon emission computed tomography, positron emission tomography, fluorescence, and γ-camera imaging. The four major classes of ligands that have been developed for non-invasive visualization of IGF1R will be discussed: proteins, antibodies, peptides, and affibodies. To date, molecular imaging of IGF1R expression is understudied and more research effort is needed in the future.