64Cu-DOTA-Trastuzumab PET Imaging in Patients with HER2-Positive Breast Cancer

Anti-cancer Antibody Trastuzumab-Melanotransferrin Conjugate (BT2111) for the Treatment of Metastatic HER2+ Breast Cancer Tumors in the Brain: an In-Vivo Study

PURPOSE

The ability of human melanotransferrin (hMTf) to carry a therapeutic concentration of trastuzumab (BTA) in the brain after conjugation (in the form of trastuzumab-melanotransferrin conjugate, BT2111 conjugate) was investigated by measuring the reduction of the number and size of metastatic human HER²⁺ breast cancer tumors in a preclinical model of brain metastases of breast cancer.

METHODS

Human metastatic brain seeking breast cancer cells were injected in NuNu mice (n = 6-12 per group) which then developed experimental brain metastases. Drug uptake was analyzed in relation to metastasis size and blood-tumor barrier permeability. To investigate in-vivo activity against brain metastases, equimolar doses of the conjugate, and relevant controls (hMTf and BTA) in separate groups were administered biweekly after intracardiac injection of the metastatic cancer cells.

RESULTS

The trastuzumab-melanotransferrin conjugate (BT2111) reduced the number of preclinical human HER²⁺ breast cancer metastases in the brain by 68% compared to control groups. Tumors which remained after treatment were 46% smaller than the control groups. In contrast, BTA alone had no effect on reducing number of metastases, and was associated with only a minimal reduction in metastasis size.

CONCLUSIONS

The results suggest the novel trastuzumab-melanotransferrin conjugate (BT2111) may have utility in treating brain metastasis and validate hMTf as a potential vector for antibody transport across the Blood Brain Barrier (BBB).

Therapeutic monoclonal antibodies for respiratory diseases: Current challenges and perspectives, March 31 - April 1, 2016, Tours, France

Monoclonal antibody (mAb) therapeutics have tremendous potential to benefit patients with lung diseases, for which there remains substantial unmet medical need. To capture the current state of mAb research and development in the area of respiratory diseases, the Research Center of Respiratory Diseases (CEPR-INSERM U1100), the Laboratory of Excellence “MAbImprove,” the GDR 3260 “Antibodies and therapeutic targeting,” and the Grant Research program ARD2020 “Biotherapeutics” invited speakers from industry, academic and government organizations to present their recent research results at the Therapeutic Monoclonal Antibodies for Respiratory Diseases: Current challenges and perspectives congress held March 31 – April 1, 2016 in Tours, France.

Synthesis and evaluation of copper-64 labeled benzofuran derivatives targeting β-amyloid aggregates

In vivo imaging of β-amyloid (Aβ) aggregates consisting of Aβ(1-40) and Aβ(1-42) peptides by positron emission tomography (PET) contributes to the diagnosis and therapy for Alzheimer's disease (AD). Because (64)Cu (t1/2=12.7h) is a radionuclide for PET with a longer physical half-life than (11)C (t1/2=20min) and (18)F (t1/2=110min), it is an attractive radionuclide for the development of Aβ imaging probes that are suitable for routine use. In the present study, we designed and synthesized two novel (64)Cu labeled benzofuran derivatives and evaluated their utility as PET imaging probes for Aβ aggregates. In an in vitro binding assay, 6 and 8 showed binding affinity for Aβ(1-42) aggregates with a Ki value of 33 and 243nM, respectively. In addition, these probes bound to Aβ plaques deposited in the brain of an AD model mouse in vitro. In a biodistribution experiment using normal mice, these probes showed low brain uptake (0.33% and 0.36% ID/g) at 2min post-injection. Although refinement to enhance brain uptake is needed, [(64)Cu]6 and [(64)Cu]8 demonstrated the feasibility of developing novel PET probes for imaging Aβ aggregates.

Imaging Diagnostic and Therapeutic Targets: Human Epidermal Growth Factor Receptor 2

Since the approval of trastuzumab, a humanized monoclonal antibody against the extracellular domain of human epidermal growth factor receptor 2 (HER2), 3 other HER2-targeting agents have gained regulatory approval: lapatinib, pertuzumab, and trastuzumab-emtansine. These agents have revolutionized the management of HER2-positive breast cancer, highlighting the concept that targeted therapies are successful when patients exhibit tumor-selective expression of a molecular target-in this case, HER2. However, response prediction and innate or acquired resistance remain serious concerns. Predictive biomarkers of a response-which could help in the selection of patients who might benefit from a selected targeted therapy-are currently lacking. Molecular imaging with anti-HER2 probes allows the noninvasive, whole-body assessment of HER2 tumor burden and has the potential to improve patient selection, optimize the dose and schedule, and rationalize assessment of the response to anti-HER2 therapies. Furthermore, unlike biopsy-based HER2 assessment, this approach can reveal inter- or intratumoral heterogeneity as well as variations in HER2 expression over time. This review summarizes the available literature and the current status of molecular imaging as a tool for the assessment of HER2 (target) expression or the prediction of an early treatment response in early and advanced HER2-positive breast cancer.

Immuno-PET Using Anticarcinoembryonic Antigen Bispecific Antibody and 68Ga-Labeled Peptide in Metastatic Medullary Thyroid Carcinoma: Clinical Optimization of the Pretargeting Parameters in a First-in-Human Trial

Earlier clinical studies reported a high sensitivity of pretargeted immunoscintigraphy using murine or chimeric anticarcinoembryonic antigen (CEA) bispecific antibody (BsMAb) and peptides labeled with ¹¹¹In or ¹³¹I in medullary thyroid carcinoma (MTC). Preclinical studies showed that new-generation humanized recombinant anti-CEA × antihistamine-succinyl-glycine (HSG) trivalent BsMAb TF2 and radiolabeled HSG peptide (IMP288) present good features for PET. This study aimed at optimizing molar doses and pretargeting interval of TF2 and ⁶⁸Ga-labeled IMP288 for immuno-PET in relapsed MTC patients with calcitonin serum levels greater than 150 pg/mL.

METHODS

Five cohorts (C1-C5) of 3 patients received variable molar doses of TF2 and approximately 150 MBq of ⁶⁸Ga-IMP288 after different pretargeting time intervals (C1: 120 nmol TF2, 6 nmol IMP288, 24 h; C2: 120 nmol TF2, 6 nmol IMP288, 30 h; C3: 120 nmol TF2, 6 nmol IMP288, 42 h; C4: 120 nmol TF2, 3 nmol IMP288, 30 h; and C5: 60 nmol TF2, 3 nmol IMP288, 30 h). TF2 and ⁶⁸Ga-IMP288 pharmacokinetics were monitored. Whole-body PET was recorded 60 and 120 min after ⁶⁸Ga-IMP288 injection. Tumor maximal SUV (T-SUV_max) and T-SUV_max-to-mediastinum blood-pool (MBP) SUV_mean ratios (T/MBP) were determined.

RESULTS

In C1, T-SUV_max and T/MBP ranged from 4.09 to 8.93 and 1.39 to 3.72 at 60 min and 5.14 to 11.25 and 2.73 to 5.38 at 120 min, respectively. Because of the high MBP, the delay was increased to 30 h in C2, increasing T-SUV_max and T/MBP. Further increasing the delay to 42 h in C3 decreased T-SUV_max and T/MBP, showing that 30 h was the most favorable delay. In C4, the TF2-to-peptide mole ratio was increased to 40 (delay 30 h), resulting in high T-SUV_max but with higher MBP than in C2. In C5, the molar dose of TF2 was reduced, resulting in lower imaging performance. Pharmacokinetics demonstrated a fast TF2 clearance and a clear relationship between blood activity clearance and the ratio between the molar amount of injected peptide to the molar amount of circulating TF2 at the time of peptide injection.

CONCLUSION

High tumor uptake and contrast can be obtained with pretargeted anti-CEA immuno-PET in relapsed MTC patients, especially using optimized pretargeting parameters: a BsMAb-to-peptide mole ratio of 20 and 30 h pretargeting delay.

Molecular imaging-its current role in cancer

Medical imaging has undergone extensive growth over the last few decades and now plays a central role in clinical oncology. The future of imaging in the management of oncology patients is molecularly targeted imaging agents. Molecular imaging differs from conventional anatomical imaging in that imaging probes are utilized to visualize target molecules-of-interest. It is envisioned that molecular imaging will have a major impact on oncology and personalized medicine by allowing earlier diagnosis, assessing early response to treatment and by predicting treatment response. It will, hopefully, also have an impact on drug development by streamlining preclinical and clinical tests for new drug candidates.

PET-based molecular imaging in personalized oncology: potential of the assessment of therapeutic outcome

Molecular imaging techniques allow an individualization and optimization of therapy on a patient basis noninvasively. The availability of new hybrid scanners, like PET-computed tomography and PET-MRI allow the combined assessment of changes in morphology and function and are a unique tool for personalized cancer treatment. In particular, it is crucial to identify nonresponders as soon as possible for therapy guidance. The choice of the appropriate therapy and optimal treatment duration can help to avoid side effects and save costs. Furthermore, the development of new specific tracers will enable a more accurate assessment of a therapeutic result. Numerous peptides targeting receptor-active tumors are in development with a high potential in a large spectrum of tumors for theranostic approaches.

Preclinical Efficacy of Ado-trastuzumab Emtansine in the Brain Microenvironment

BACKGROUND

Central nervous system (CNS) metastases represent a major problem in the treatment of human epidermal growth factor receptor 2 (HER2)-positive breast cancer because of the disappointing efficacy of HER2-targeted therapies against brain lesions. The antibody-drug conjugate ado-trastuzumab emtansine (T-DM1) has shown efficacy in trastuzumab-resistant systemic breast cancer. Here, we tested the hypothesis that T-DM1 could overcome trastuzumab resistance in murine models of brain metastases.

METHODS

We treated female nude mice bearing BT474 or MDA-MB-361 brain metastases (n = 9-11 per group) or cancer cells grown in organotypic brain slice cultures with trastuzumab or T-DM1 at equivalent or equipotent doses. Using intravital imaging, molecular techniques and histological analysis we determined tumor growth, mouse survival, cancer cell apoptosis and proliferation, tumor drug distribution, and HER2 signaling. Data were analyzed with one-way analysis of variance (ANOVA), Kaplan-Meier analysis, and Coefficient of Determination. All statistical tests were two-sided.

RESULTS

T-DM1 delayed the growth of HER2-positive breast cancer brain metastases compared with trastuzumab. These findings were consistent between HER2-driven and PI3K-driven tumors. The activity of T-DM1 resulted in a survival benefit (median survival for BT474 tumors: 28 days for trastuzumab vs 112 days for T-DM1, hazard ratio = 6.2, 95% confidence interval = 6.1 to 85.84, P < .001). No difference in drug distribution or HER2-signaling was revealed between the two groups. However, T-DM1 led to a statistically significant increase in tumor cell apoptosis (one-way ANOVA for ApopTag, P < .001), which was associated with mitotic catastrophe.

CONCLUSIONS

T-DM1 can overcome resistance to trastuzumab therapy in HER2-driven or PI3K-driven breast cancer brain lesions due to the cytotoxicity of the DM1 component. Clinical investigation of T-DM1 for patients with CNS metastases from HER2-positive breast cancer is warranted.

Combination Radioimmunotherapy Approaches and Quantification of Immuno-PET

Monoclonal antibodies (mAbs), which play a prominent role in cancer therapy, can interact with specific antigens on cancer cells, thereby enhancing the patient's immune response via various mechanisms, or mAbs can act against cell growth factors and, thereby, arrest the proliferation of tumor cells. Radionuclide-labeled mAbs, which are used in radioimmunotherapy (RIT), are effective for cancer treatment because tumor associated-mAbs linked to cytotoxic radionuclides can selectively bind to tumor antigens and release targeted cytotoxic radiation. Immunological positron emission tomography (immuno-PET), which is the combination of PET with mAb, is an attractive option for improving tumor detection and mAb quantification. However, RIT remains a challenge because of the limited delivery of mAb into tumors. The transport and uptake of mAb into tumors is slow and heterogeneous. The tumor microenvironment contributed to the limited delivery of the mAb. During the delivery process of mAb to tumor, mechanical drug resistance such as collagen distribution or physiological drug resistance such as high intestinal pressure or absence of lymphatic vessel would be the limited factor of mAb delivery to the tumor at a potentially lethal mAb concentration. When α-emitter-labeled mAbs were used, deeper penetration of α-emitter-labeled mAb inside tumors was more important because of the short range of the α emitter. Therefore, combination therapy strategies aimed at improving mAb tumor penetration and accumulation would be beneficial for maximizing their therapeutic efficacy against solid tumors.

ImmunoPET/MR imaging allows specific detection of Aspergillus fumigatus lung infection in vivo

Invasive pulmonary aspergillosis (IPA) is a life-threatening lung disease caused by the fungus Aspergillus fumigatus, and is a leading cause of invasive fungal infection-related mortality and morbidity in patients with hematological malignancies and bone marrow transplants. We developed and tested a novel probe for noninvasive detection of A. fumigatus lung infection based on antibody-guided positron emission tomography and magnetic resonance (immunoPET/MR) imaging. Administration of a [(64)Cu]DOTA-labeled A. fumigatus-specific monoclonal antibody (mAb), JF5, to neutrophil-depleted A. fumigatus-infected mice allowed specific localization of lung infection when combined with PET. Optical imaging with a fluorochrome-labeled version of the mAb showed colocalization with invasive hyphae. The mAb-based newly developed PET tracer [(64)Cu]DOTA-JF5 distinguished IPA from bacterial lung infections and, in contrast to [(18)F]FDG-PET, discriminated IPA from a general increase in metabolic activity associated with lung inflammation. To our knowledge, this is the first time that antibody-guided in vivo imaging has been used for noninvasive diagnosis of a fungal lung disease (IPA) of humans, an approach with enormous potential for diagnosis of infectious diseases and with potential for clinical translation.

Targeted Therapy in Brain Metastases: Ready for Primetime?

Brain metastasis is a serious complication of cancer that causes significant morbidity for patients. Over the last decade, numerous new driver somatic mutations have been recognized and targeted therapies are changing the landscape of treatment in lung cancer, breast cancer, and melanoma, which are also the three most common cancers that result in brain metastases. The common actionable mutations include the EGFR mutation and anaplastic lymphoma kinase (ALK) translocations in non-small cell lung cancer, the HER2 mutation in breast cancer, and the BRAF mutation in melanoma. However, most of the early trials with targeted agents excluded patients with brain metastases. With a better understanding of the biology, several recent trials of targeted therapy that focus on brain metastases have been reported and others are ongoing. Novel agents with better penetration across the blood-brain barrier are currently being investigated for patients with brain metastases. In this review, we discuss the current state of use and future directions of targeted therapies in brain metastases.

Evaluation of 18F-FDG uptake for detecting lymph node metastasis of gastric cancer: a prospective pilot study for one-to-one comparison of radiation dose and pathological findings

Background

Gastric cancer exhibits various degrees of fluorine F-18 fluorodeoxyglucose (¹⁸F-FDG) uptake on positron emission tomography/computed tomography (PET/CT). We evaluated the relationship between ¹⁸F-FDG uptake and the presence/absence of metastasis in individual lymph nodes (LN) on a one-to-one basis.

Methods

We analyzed 21 patients with gastric cancer. We injected ¹⁸F-FDG intravenously in the morning, and gastrectomy with LN dissection was performed in the afternoon of the same day. Radiation doses were measured at each LN using a well-type counter, and we then compared ¹⁸F-FDG uptake, the shortest diameter, and pathological examination results for each LN.

Results

In our study, 906 LNs were analyzed, including 115 metastatic LNs. Metastatic LNs showed significantly higher ¹⁸F-FDG uptake (P < 0.0001), and were significantly enlarged (P < 0.0001). The receiver operating characteristics (ROC) curve had a larger area under the curve (0.71) for ¹⁸F-FDG uptake than for the shortest LN diameter (0.60). Considering histology, the ROC curve for intestinal type adenocarcinoma had a larger area under the curve than that for diffuse type (0.75 vs 0.61).

Conclusions

F-FDG uptake is potentially a more useful variable than LN diameter for discriminating between LN with and without metastasis, especially in intestinal type gastric cancer cases.

Bifunctional (64)Cu-labelled macrobicyclic cage amine isothiocyanates for immuno-positron emission tomography

New macrobicyclic cage amine or "sarcophagine" (sar) bifunctional chelators have been synthesised that form copper complexes of exceptional in vivo stability and incorporate isothiocyanate (-NCS) functional groups for conjugation to an antibody. The chelators were synthesised from the methyl-capped complex [Mg(II)(CH3)(NH2)sar](2+). Coordination of Mg(II) within the cavity of the cage amine ligand protects the secondary amine atoms from reacting with the -NCS functional groups. Two different [Mg(II)(NCS-sar)](2+) derivatives were conjugated to the HER2/neu-targeting antibody trastuzumab and the progress of the reaction monitored by electrospray mass spectrometry. The Mg(II) ion was removed from the immunoconjugates under mild conditions (0.1 M citrate buffer, pH 6). Labelling of the (CH3)(p-NCS-Ph)sar-trastuzumab conjugate with (64)Cu(II), a radioisotope suitable for positron emission tomography (PET), was fast (∼5 min) and easily performed at room temperature with high radiochemical purity (>95%). Biodistribution and PET imaging studies in vivo showed that (64)Cu-labelled (CH3)(p-NCS-Ph)sar-trastuzumab maintained high stability under physiological conditions with high and selective uptake in a HER2-positive cancer cell line. The stability of the copper complex and the 12.7 h half-life of the radioisotope allows clear visualisation of tumours out to 48 h.

Breast cancer brain metastases: the last frontier

Breast cancer is a common cause of brain metastases, with metastases occurring in at least 10–16 % of patients. Longer survival of patients with metastatic breast cancer and the use of better imaging techniques are associated with an increased incidence of brain metastases. Unfortunately, patients who develop brain metastases tend to have poor prognosis with short overall survival. In addition, brain metastases are a major cause of morbidity, associated with progressive neurologic deficits that result in a reduced quality of life. Tumor subtypes play a key role in prognosis and treatment selection. Current therapies include surgery, whole-brain radiation therapy, stereotactic radiosurgery, chemotherapy and targeted therapies. However, the timing and appropriate use of these therapies is controversial and careful patient selection by using available prognostic tools is extremely important. This review will focus on current treatment options, novel therapies, future approaches and ongoing clinical trials for patients with breast cancer brain metastases.

Polymeric Micelle Platform for Multimodal Tomographic Imaging to Detect Scirrhous Gastric Cancer

Scirrhous gastric cancer (SGC) is a recalcitrant tumor, which is among the most lethal cancers. A critical issue for the improvement of SGC prognosis is the lack of an effective imaging method for accurate detection and diagnosis. Because combined nuclear medicine imaging with magnetic resonance imaging (MRI) has the ability to detect cancer with high sensitivity, and quantitation and spatial resolution, it has potential to overcome the issues with SGC detection. Herein, we designed and synthesized a new block copolymer poly(ethylene glycol)-b-poly(γ-benzyl l-glutamate) linked with a chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA-PEG-b-PBLG) to provide a platform for multimodal tomographic imaging. We then successfully prepared DOTA-functionalized polymeric micelles (DOTA/m) measuring 30 nm in diameter, which is an appropriate size to penetrate deeply into tumors with thick fibrosis, including SGC. ¹¹¹In-labeled DOTA/m highly accumulated in Colon-26 tumors (mouse colon cancer with hyperpermeability), but also in OCUM-2 M LN tumors (SGC with hypopermeability), clearly depicting both tumors by single photon emission computed tomography (SPECT). Gd-labeled DOTA/m clearly visualized OCUM-2 M LN tumors by MRI with high spatial resolution. Moreover, ¹¹¹In/Gd-labeled micelles, as well as the mixture of ¹¹¹In- and Gd-labeled DOTA/m demonstrated the capability of this system for selective multimodal SPECT/MR imaging of SCG. Our findings support ¹¹¹In/Gd-DOTA-labeled micelles as a clinical translationable modality for multimodal tomographic imaging capable of detecting SGC.

Gallium-68-labeled anti-HER2 single-chain Fv fragment: development and in vivo monitoring of HER2 expression

PURPOSE

We aimed to develop a gallium-68 (Ga-68)-labeled single-chain variable fragment (scFv) targeting the human epidermal growth factor receptor 2 (HER2) to rapidly and noninvasively evaluate the status of HER2 expression.

PROCEDURES

Anti-HER2 scFv was labeled with Ga-68 by using deferoxamine (Df) as a bifunctional chelate. Biodistribution of [(68)Ga]Df-anti-HER2 scFv was examined with tumor-bearing mice and positron emission tomography (PET) imaging was performed. The changes in HER2 expression after anti-HER2 therapy were monitored by PET imaging.

RESULTS

[(68)Ga]Df-anti-HER2 scFv was obtained with high radiochemical yield after only a 5-min reaction at room temperature. The probe showed high accumulation in HER2-positive xenografts and the intratumoral distribution of radioactivity coincided with HER2-positive regions. Furthermore, [(68)Ga]Df-anti-HER2 scFv helped visualize HER2-positive xenografts and monitor the changes in HER2 expression after anti-HER2 therapy.

CONCLUSION

[(68)Ga]Df-anti-HER2 scFv could be a promising probe to evaluate HER2 status by in vivo PET imaging, unless trastuzumab is prescribed as part of the therapy.

First-in-human uPAR PET: Imaging of Cancer Aggressiveness

A first-in-human clinical trial with Positron Emission Tomography (PET) imaging of the urokinase-type plasminogen activator receptor (uPAR) in patients with breast, prostate and bladder cancer, is described. uPAR is expressed in many types of human cancers and the expression is predictive of invasion, metastasis and indicates poor prognosis. uPAR PET imaging therefore holds promise to be a new and innovative method for improved cancer diagnosis, staging and individual risk stratification. The uPAR specific peptide AE105 was conjugated to the macrocyclic chelator DOTA and labeled with ⁶⁴Cu for targeted molecular imaging with PET. The safety, pharmacokinetic, biodistribution profile and radiation dosimetry after a single intravenous dose of ⁶⁴Cu-DOTA-AE105 were assessed by serial PET and computed tomography (CT) in 4 prostate, 3 breast and 3 bladder cancer patients. Safety assessment with laboratory blood screening tests was performed before and after PET ligand injection. In a subgroup of the patients, the in vivo stability of our targeted PET ligand was determined in collected blood and urine. No adverse or clinically detectable side effects in any of the 10 patients were found. The ligand exhibited good in vivo stability and fast clearance from plasma and tissue compartments by renal excretion. In addition, high uptake in both primary tumor lesions and lymph node metastases was seen and paralleled high uPAR expression in excised tumor tissue. Overall, this first-in-human study therefore provides promising evidence for safe use of ⁶⁴Cu-DOTA-AE105 for uPAR PET imaging in cancer patients.

The future of targeted therapies for brain metastases

Brain metastases (BM) are an increasing challenge in the management of patients with advanced cancer. Treatment options for BM are limited and mainly focus on the application of local therapies. Systemic therapies including targeted therapies are only poorly investigated, as patients with BM were frequently excluded from clinical trials. Several targeted therapies have shown promising activity in patients with BM. In the present review we discuss existing and emerging targeted therapies for the most frequent BM primary tumor types. We focus on challenges in the conduction of clinical trials on targeted therapies in BM patients such as patient selection, combination with radiotherapy, the obstacles of the blood–brain barrier and the definition of study end points.

PET/Computed Tomography Using New Radiopharmaceuticals in Targeted Therapy

Targeted therapy is gaining prominence in the management of different cancers. Given different mechanism of action compared with traditional chemoradiotherapy, selection of patients for targeted therapy and monitoring response to these agents is difficult with conventional imaging. Various new PET radiopharmaceuticals have been evaluated for molecular imaging of these targets to achieve specific patient selection and response monitoring. These PET/computed tomography (CT) agents target the cell surface receptors, hormone receptors, receptor tyrosine kinases, or angiogenesis components. This article reviews the established and potential role of PET/CT with new radiopharmaceuticals for guiding targeted therapy.

Molecular imaging using PET for breast cancer

Molecular imaging can visualize the biological processes at the molecular and cellular levels in vivo using certain tracers for specific molecular targets. Molecular imaging of breast cancer can be performed with various imaging modalities, however, positron emission tomography (PET) is a sensitive and non-invasive molecular imaging technology and this review will focus on PET molecular imaging of breast cancer, such as FDG-PET, FLT-PET, hormone receptor PET, and anti-HER2 PET.

[(64) Cu]-labelled trastuzumab: optimisation of labelling by DOTA and NODAGA conjugation and initial evaluation in mice

The human epidermal growth factor receptor‐2 (HER2) is overexpressed in 20–30% of all breast cancer cases, leading to increased cell proliferation, growth and migration. The monoclonal antibody, trastuzumab, binds to HER2 and is used for treatment of HER2‐positive breast cancer. Trastuzumab has previously been labelled with copper‐64 by conjugation of a 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) chelator. The aim of this study was to optimise the ⁶⁴Cu‐labelling of DOTA‐trastuzumab and as the first to produce and compare with its 1,4,7‐triazacyclononane, 1‐glutaric acid‐5,7 acetic acid (NODAGA) analogue in a preliminary HER2 tumour mouse model. The chelators were conjugated to trastuzumab using the activated esters DOTA mono‐N‐hydroxysuccinimide (NHS) and NODAGA‐NHS. ⁶⁴Cu‐labelling of DOTA‐trastuzumab was studied by varying the amount of DOTA‐trastuzumab used, reaction temperature and time. Full ⁶⁴Cu incorporation could be achieved using a minimum of 10‐µg DOTA‐trastuzumab, but the fastest labelling was obtained after 15 min at room temperature using 25 µg of DOTA‐trastuzumab. In comparison, 80% incorporation was achieved for ⁶⁴Cu‐labelling of NODAGA‐trastuzumab. Both [⁶⁴Cu]DOTA‐trastuzumab and [⁶⁴Cu]NODAGA‐trastuzumab were produced after purification with radiochemical purities of >97%. The tracers were injected into mice with HER2 expressing tumours. The mice were imaged by positron emission tomography and showed high tumour uptake of 3–9% ID/g for both tracers.

Tumor-specific delivery of BSH-3R for boron neutron capture therapy and positron emission tomography imaging in a mouse brain tumor model

Glioblastoma, a malignant brain tumor with poor disease outcomes, is managed in modern medicine by multimodality therapy. Boron neutron capture therapy (BNCT) is an encouraging treatment under clinical investigation. In malignant cells, BNCT consists of two major factors: neutron radiation and boron uptake. To increase boron uptake in cells, we created a mercapto-closo-undecahydrododecaborate ([B12HnSH](2-)2Na(+), BSH) fused with a short arginine peptide (1R, 2R, 3R) and checked cellular uptake in vitro and in vivo. In a mouse brain tumor model, only BSH with at least three arginine domains could penetrate cell membranes of glioma cells in vitro and in vivo. Furthermore, to monitor the pharmacokinetic properties of these agents in vivo, we fused BSH and BSH-3R with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA); DOTA is a metal chelating agent for labeling positron emission tomography (PET) probe with (64)Cu. We administered BSH-DOTA-(64)Cu and BSH-3R-DOTA-(64)Cu to the tumor model through a mouse tail vein and determined the drugs' pharmacokinetics by PET imaging. BSH-3R showed a high uptake in the tumor area on PET imaging. We concluded that BSH-3R is the ideal boron compound for clinical use during BNCT and that in developing this compound for clinical use, the BSH-3R PET probe is essential for pharmacokinetic imaging.

Radiopharmaceuticals as probes to characterize tumour tissue

Tumour cells exhibit several properties that allow them to grow and divide. A number of these properties are detectable by nuclear imaging methods. We discuss crucial tumour properties that can be described by current radioprobe technologies, further discuss areas of emerging radioprobe development, and finally articulate need areas that our field should aspire to develop. The review focuses largely on positron emission tomography and draws upon the seminal 'Hallmarks of Cancer' review article by Hanahan and Weinberg in 2011 placing into context the present and future roles of radiotracer imaging in characterizing tumours.

A novel PET imaging using ⁶⁴Cu-labeled monoclonal antibody against mesothelin commonly expressed on cancer cells

Mesothelin (MSLN) is a 40-kDa cell differentiation-associated glycoprotein appearing with carcinogenesis and is highly expressed in many human cancers, including the majority of pancreatic adenocarcinomas, ovarian cancers, and mesotheliomas, while its expression in normal tissue is limited to mesothelial cells lining the pleura, pericardium, and peritoneum. Clone 11-25 is a murine hybridoma secreting monoclonal antibody (mAb) against human MSLN. In this study, we applied the 11-25 mAb to in vivo imaging to detect MSLN-expressing tumors. In in vitro and ex vivo immunochemical studies, we demonstrated specificity of 11-25 mAb to membranous MSLN expressed on several pancreatic cancer cells. We showed the accumulation of Alexa Fluor 750-labeled 11-25 mAb in MSLN-expressing tumor xenografts in athymic nude mice. Then, 11-25 mAb was labeled with ⁶⁴Cu via a chelating agent DOTA and was used in both in vitro cell binding assay and in vivo positron emission tomography (PET) imaging in the tumor-bearing mice. We confirmed that ⁶⁴Cu-labeled 11-25 mAb highly accumulated in MSLN-expressing tumors as compared to MSLN-negative ones. The ⁶⁴Cu-labeled 11-25 mAb is potentially useful as a PET probe capable of being used for wide range of tumors, rather than ¹⁸F-FDG that occasionally provides nonspecific accumulation into the inflammatory lesions.

Theragnostic imaging using radiolabeled antibodies and tyrosine kinase inhibitors

During the past decade, the efficacy of new molecular targeted drugs such as tyrosine kinase inhibitors (TKIs) and monoclonal antibodies has been proven worldwide, and molecular targeted therapies have become the mainstream in cancer therapy. However, clinical use of these new drugs presents unexpected adverse effects or poor therapeutic effects. Therefore, we require diagnostic tools to estimate the target molecule status in cancer tissues and predict therapeutic efficacy and adverse effects. Although immunohistochemical, polymerase chain reaction (PCR) and fluorescence in situ hybridization (FISH) analyses of biopsy samples are conventional and popular for this diagnostic purpose, molecular imaging modalities such as positron emission tomography (PET) and single photon emission computed tomography (SPECT) are also useful for noninvasive estimation of gene and protein expression and drug pharmacokinetics. In this review, we introduce new radiolabeled TKIs, antibodies, and their clinical application in molecular targeted therapy and discuss the issues of these imaging probes.

(64)Cu-DOTA-trastuzumab PET imaging and HER2 specificity of brain metastases in HER2-positive breast cancer patients

Background

The purpose of this study was to determine whether brain metastases from HER2-positive breast cancer could be detected noninvasively using positron emission tomography (PET) with ⁶⁴Cu-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-trastuzumab.

Methods

PET was performed on five patients with brain metastases from HER2-positive breast cancer, at 24 or 48 h after the injection of approximately 130 MBq of the probe ⁶⁴Cu-DOTA-trastuzumab. Radioactivity in metastatic brain tumors was evaluated based on PET images in five patients. Autoradiography, immunohistochemistry (IHC), and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis were performed in one surgical case to confirm HER2 specificity of ⁶⁴Cu-DOTA-trastuzumab.

Results

Metastatic brain lesions could be visualized by ⁶⁴Cu-DOTA-trastuzumab PET in all of five cases, which might indicated that trastuzumab passes through the blood-brain barrier (BBB). The HER2 specificity of ⁶⁴Cu-DOTA-trastuzumab was demonstrated in one patient by autoradiography, immunohistochemistry, and LC-MS/MS.

Conclusions

Cu-DOTA-trastuzumab PET could be a potential noninvasive procedure for serial identification of metastatic brain lesions in patients with HER2-positive breast cancer.

Trial registration

UMIN000004170

Whole-body immunoPET reveals active SIV dynamics in viremic and antiretroviral therapy-treated macaques

The detection of viral dynamics and localization in the context of controlled HIV infection remains a challenge and is limited to blood and biopsies. We developed a method to capture total-body simian immunodeficiency virus (SIV) replication using immunoPET (antibody-targeted positron emission tomography). The administration of a poly(ethylene glycol)-modified, (64)Cu-labeled SIV Gp120-specific antibody led to readily detectable signals in the gastrointestinal and respiratory tract, lymphoid tissues and reproductive organs of viremic monkeys. Viral signals were reduced in aviremic antiretroviral-treated monkeys but detectable in colon, select lymph nodes, small bowel, nasal turbinates, the genital tract and lung. In elite controllers, virus was detected primarily in foci in the small bowel, select lymphoid areas and the male reproductive tract, as confirmed by quantitative reverse-transcription PCR (qRT-PCR) and immunohistochemistry. This real-time, in vivo viral imaging method has broad applications to the study of immunodeficiency virus pathogenesis, drug and vaccine development, and the potential for clinical translation.

Cancer stratification by molecular imaging

The lack of specificity of traditional cytotoxic drugs has triggered the development of anticancer agents that selectively address specific molecular targets. An intrinsic property of these specialized drugs is their limited applicability for specific patient subgroups. Consequently, the generation of information about tumor characteristics is the key to exploit the potential of these drugs. Currently, cancer stratification relies on three approaches: Gene expression analysis and cancer proteomics, immunohistochemistry and molecular imaging. In order to enable the precise localization of functionally expressed targets, molecular imaging combines highly selective biomarkers and intense signal sources. Thus, cancer stratification and localization are performed simultaneously. Many cancer types are characterized by altered receptor expression, such as somatostatin receptors, folate receptors or Her2 (human epidermal growth factor receptor 2). Similar correlations are also known for a multitude of transporters, such as glucose transporters, amino acid transporters or hNIS (human sodium iodide symporter), as well as cell specific proteins, such as the prostate specific membrane antigen, integrins, and CD20. This review provides a comprehensive description of the methods, targets and agents used in molecular imaging, to outline their application for cancer stratification. Emphasis is placed on radiotracers which are used to identify altered expression patterns of cancer associated markers.

Preclinical characterization and validation of a dual-labeled trastuzumab-based imaging agent for diagnosing breast cancer

OBJECTIVE

The combination of both nuclear and fluorescent reporters provides unique opportunities for noninvasive nuclear imaging with subsequent fluorescence image-guided resection and pathology. Our objective was to synthesize and optimize a dual-labeled trastuzumab-based imaging agent that can be used to validate an optical imaging agent with potential use in identifying tumor metastases in human epidermal growth factor receptor 2 (HER2) positive breast cancer patients.

METHODS

[(111)In]-DTPA-trastuzumab-IRDye 800 was synthesized by a three-step procedure. Purity, stability, immunoreactivity, internalization and biodistribution were explored in HER2+ SKBR-3 cells. Biodistribution of [(111)In]-DTPA-trastuzumab-IRDye 800 was performed in a SKBR-3 xenograft model.

RESULTS

[(111)In]-DTPA-trastuzumab-IRDye 800 demonstrated high purity by both chemical and fluorometric determinations. Both flow cytometry and the Lindmo assay demonstrated a high binding affinity of [(111)In]-DTPA-trastuzumab-IRDye 800 to HER2-overexpressing cells. The dual-labeled conjugate was stable in PBS, but not in serum after 24 h at 37 °C. Larger molecules (>150 kD) were seen after a 24 h-incubation in human serum. Biodistribution studies revealed tumor-specific accumulation of [(111)In]-DTPA-trastuzumab-IRDye 800 in SKBR-3 tumors, and tumor uptakes at 24 and 48 h were (12.42±1.72)% and (9.96±1.05)%, respectively, following intravenous administration. The tumor-to-muscle ratio was 9.13±1.68 at 24 h, and increased to 12.79±2.13 at 48 h. Liver and kidney showed marked uptake of the dual-labeled imaging agent.

CONCLUSIONS

[(111)In]-DTPA-trastuzumab-IRDye 800 is an effective diagnostic biomarker that can be used to validate dual-labeled, molecularly targeted imaging agents and can allow these agents to be translated into clinical practice for identifying HER2+ lesions.

Tumor immunotargeting using innovative radionuclides

This paper reviews some aspects and recent developments in the use of antibodies to target radionuclides for tumor imaging and therapy. While radiolabeled antibodies have been considered for many years in this context, only a few have reached the level of routine clinical use. However, alternative radionuclides, with more appropriate physical properties, such as lutetium-177 or copper-67, as well as alpha-emitting radionuclides, including astatine-211, bismuth-213, actinium-225, and others are currently reviving hopes in cancer treatments, both in hematological diseases and solid tumors. At the same time, PET imaging, with short-lived radionuclides, such as gallium-68, fluorine-18 or copper-64, or long half-life ones, particularly iodine-124 and zirconium-89 now offers new perspectives in immuno-specific phenotype tumor imaging. New antibody analogues and pretargeting strategies have also considerably improved the performances of tumor immunotargeting and completely renewed the interest in these approaches for imaging and therapy by providing theranostics, companion diagnostics and news tools to make personalized medicine a reality.

Emerging strategies for treating brain metastases from breast cancer

Brain metastasis is an end stage in breast cancer progression. Traditional treatment options have minimal efficacy, and overall survival is on the order of months. The incidence of brain metastatic disease is increasing with the improved management of systemic disease and prolongation of survival. Unfortunately, the targeted therapies that control systemic disease have diminished efficacy against brain lesions. There are reasons to be optimistic, however, as emerging therapies have shown promise in preclinical and early clinical settings. This review discusses recent advances in breast cancer brain metastasis therapy and potential approaches for successful treatment.

[Molecular breast imaging. An update]

CLINICAL/METHODICAL ISSUE

The aim of molecular imaging is to visualize and quantify biological, physiological and pathological processes at cellular and molecular levels. Molecular imaging using various techniques has recently become established in breast imaging.

STANDARD RADIOLOGICAL METHODS

Currently molecular imaging techniques comprise multiparametric magnetic resonance imaging (MRI) using dynamic contrast-enhanced MRI (DCE-MRI), diffusion-weighted imaging (DWI), proton MR spectroscopy ((1)H-MRSI), nuclear imaging by breast-specific gamma imaging (BSGI), positron emission tomography (PET) and positron emission mammography (PEM) and combinations of techniques (e.g. PET-CT and multiparametric PET-MRI).

METHODICAL INNOVATIONS

Recently, novel techniques for molecular imaging of breast tumors, such as sodium imaging ((23)Na-MRI), phosphorus spectroscopy ((31)P-MRSI) and hyperpolarized MRI as well as specific radiotracers have been developed and are currently under investigation.

PRACTICAL RECOMMENDATIONS

It can be expected that molecular imaging of breast tumors will enable a simultaneous assessment of the multiple metabolic and molecular processes involved in cancer development and thus an improved detection, characterization, staging and monitoring of response to treatment will become possible.

Kit for the preparation of 111In-labeled pertuzumab injection for imaging response of HER2-positive breast cancer to trastuzumab (Herceptin)

We previously reported that ¹¹¹In-labeled pertuzumab imaged trastuzumab (Herceptin)-mediated changes in HER2 expression preclinically in breast cancer tumors. To advance ¹¹¹In-labeled pertuzumab to a Phase I/II clinical trial, a kit was designed for preparing this agent in a form suitable for human administration. Unit-dose kits containing pertuzumab modified with 2-(4-isothiocyanatobenzyl)-diethylenetriaminepentaacetic acid (BzDTPA) were prepared that labeled to high efficiency (>90%) with ¹¹¹In and met specifications for pharmaceutical quality. The kits were stable for 4 months and the final radiopharmaceutical was stable for 24h. Imaging studies demonstrated high and specific uptake in HER2-positive tumors in mice using this clinical kit formulation.

Brain metastases in breast cancer

Brain metastases are less common than bone or visceral metastases in patients with breast cancer. The overall prognosis of breast cancer patients with brain metastases remains poor, and these metastases are less responsive to systemic therapies. Brain metastasis is associated with a reduced quality of life due to progressive neurologic impairments. Recently, a trend of increased incidence of brain metastases in breast cancer has been noted. Reasons for this increased incidence include the more frequent use of sensitive detection methods such as contrast-enhanced magnetic resonance imaging and increased awareness of brain metastasis among patients and clinicians. Adjuvant and systemic therapy with drugs that have a low blood-brain barrier penetrance can lead to an increased risk of brain metastases in breast cancer patients. Molecular subtype is a predictive factor for overall survival after developing brain metastases. Patients who do not have a poor prognosis based on previously identified prognostic factors should be treated with radiation therapy to control symptoms. Whole-brain radiation therapy, stereotactic irradiation and surgery are tools for the local treatment of brain metastases. Novel molecular target therapy, including HER2-targeted therapy, has demonstrated an antitumor effect on brain metastases. In this review, we provide a practical algorithm for the treatment of breast cancer brain metastases. This review provides an overview of the incidence, risk factors, diagnosis, prognostic factors and current and potential future management strategies of breast cancer brain metastases.

Synthesis, physicochemical and biological evaluation of technetium-99m labeled lapatinib as a novel potential tumor imaging agent of Her-2 positive breast cancer

Tumors that are Her-2-positive tend to grow and spread more quickly than other types of breast cancer. Overexpression of Her-2 can be a predictive biomarker for stratification of patients for therapy with Herceptin (containing humanized IgG1 monoclonal antibody trastuzumab) or Tykerb (containing lapatinib di-p-toluenesulfonate) drug. Usually, Her-2 status is determined by immunohistochemical (IHC) as well as fluorescent or chromogenic in situ hybridisation (FISH or CISH) analysis of biopsy material. The objective of the present work was to standardize the conjugation of anti-cancer drug lapatinib (which recognizes selectively the Her-2 extracellular domain) with technetium-99m complex, of type '4+1', to obtain (99m)Tc(NS3)(CN-lapatinib) conjugate for use as in vivo tracer of the Her-2 expression in breast cancer. The conjugate (99m)Tc(NS3)(CN-lapatinib) was formed with high yield, high radiochemical purity and specific activity within the range 25-30 GBq/μmol. The biological in vitro and in vivo studies of the conjugate showed its high affinity to Her-2 receptor (Kd = 3.5 ± 0.4 nM, Ki = 2.9 ± 0.5 nM, Bmax = 2.4 ± 0.3 nM, approximate number of 2.4 × 10(6) binding sites per cell, IC50 = 41.2 ± 0.4 nM) and also pointed out to the clearance through the hepatic and renal route in comparable degree. Basing on these results one can conclude that (99m)Tc(NS3)(CN-lapatinib) conjugate could be a promising radiopharmaceutical for in vivo diagnosis of the Her-2 status in breast with impact on treatment planning.

Molecular imaging of targeted therapies with positron emission tomography: the visualization of personalized cancer care

INTRODUCTION

Molecular imaging has been defined as the visualization, characterization and measurement of biological processes at the molecular and cellular level in humans and other living systems. In oncology it enables to visualize (part of) the functional behaviour of tumour cells, in contrast to anatomical imaging that focuses on the size and location of malignant lesions. Available molecular imaging techniques include single photon emission computed tomography (SPECT), positron emission tomography (PET) and optical imaging. In PET, a radiotracer consisting of a positron emitting radionuclide attached to the biologically active molecule of interest is administrated to the patient. Several approaches have been undertaken to use PET for the improvement of personalized cancer care. For example, a variety of radiolabelled ligands have been investigated for intratumoural target identification and radiolabelled drugs have been developed for direct visualization of the biodistibution in vivo, including intratumoural therapy uptake. First indications of the clinical value of PET for target identification and response prediction in oncology have been reported. This new imaging approach is rapidly developing, but uniformity of scanning processes, standardized methods for outcome evaluation and implementation in daily clinical practice are still in progress. In this review we discuss the available literature on molecular imaging with PET for personalized targeted treatment strategies.

CONCLUSION

Molecular imaging with radiolabelled targeted anticancer drugs has great potential for the improvement of personalized cancer care. The non-invasive quantification of drug accumulation in tumours and normal tissues provides understanding of the biodistribution in relation to therapeutic and toxic effects.

Evaluation of (89)Zr-pertuzumab in Breast cancer xenografts

Pertuzumab is a monoclonal antibody that binds to HER2 and is used in combination with another HER2–specific monoclonal antibody, trastuzumab, for the treatment of HER2+ metastatic breast cancer. Pertuzumab binds to an HER2 binding site distinct from that of trastuzumab, and its affinity is enhanced when trastuzumab is present. We aim to exploit this enhanced affinity of pertuzumab for its HER2 binding epitope and adapt this antibody as a PET imaging agent by radiolabeling with ⁸⁹Zr to increase the sensitivity of HER2 detection in vivo. Here, we investigate the biodistribution of ⁸⁹Zr-pertuzumab in HER2–expressing BT-474 and HER2–nonexpressing MDA-MB-231 xenografts to quantitatively assess HER2 expression in vivo. In vitro cell binding studies were performed resulting in retained immunoreactivity and specificity for HER2–expressing cells. In vivo evaluation of ⁸⁹Zr-pertuzumab was conducted in severely combined immunodeficient mice, subcutaneously inoculated with BT-474 and MDA-MB-231 cells. ⁸⁹Zr-pertuzumab was systemically administered and imaged at 7 days postinjection (p.i.) followed by terminal biodistribution studies. Higher tumor uptake was observed in BT-474 compared to MDA-MB-231 xenografts with 47.5 ± 32.9 and 9.5 ± 1.7% ID/g, respectively at 7 days p.i (P = 0.0009) and blocking studies with excess unlabeled pertuzumab showed a 5-fold decrease in BT-474 tumor uptake (P = 0.0006), confirming the in vivo specificity of this radiotracer. Importantly, we observed that the tumor accumulation of ⁸⁹Zr-pertuzumab was increased in the presence of unlabeled trastuzumab, at 173 ± 74.5% ID/g (P = 0.01). Biodistribution studies correlate with PET imaging quantification using max SUV (r = 0.98, P = 0.01). Collectively, these results illustrate that ⁸⁹Zr-pertuzumab as a PET imaging agent may be beneficial for the quantitative and noninvasive assessment of HER2 expression in vivo especially for patients undergoing trastuzumab therapy.

Radioimmunoconjugates for the treatment of cancer

Radioimmunotherapy (RIT) has been developed for more than 30 years. Two products targeting the CD20 antigen are approved in the treatment of non-Hodgkin B-cell lymphoma (NHBL): iodine 131-tositumomab and yttrium 90-ibritumomab tiuxetan. RIT can be integrated in clinical practice for the treatment of patients with relapsed or refractory follicular lymphoma (FL) or as consolidation after induction chemotherapy. High-dose treatment, RIT in first-line treatment, fractionated RIT, and use of new humanized monoclonal antibodies (MAbs), in particular targeting CD22, showed promising results in NHBL. In other hemopathies, such as multiple myeloma, efficacy has been demonstrated in preclinical studies. In solid tumors, more resistant to radiation and less accessible to large molecules such as MAbs, clinical efficacy remains limited. However, pretargeting methods have shown clinical efficacy. Finally, new beta emitters such as lutetium 177, with better physical properties will further improve the safety of RIT and alpha emitters, such as bismuth 213 or astatine 211, offer the theoretical possibility to eradicate the last microscopic clusters of tumor cells, in the consolidation setting. Personalized treatments, based on quantitative positron emission tomography (PET), pre-therapeutic imaging, and dosimetry procedures, also could be applied to adapt injected activity to each patient.

The use of molecular imaging combined with genomic techniques to understand the heterogeneity in cancer metastasis

Tumour heterogeneity has, in recent times, come to play a vital role in how we understand and treat cancers; however, the clinical translation of this has lagged behind advances in research. Although significant advancements in oncological management have been made, personalized care remains an elusive goal. Inter- and intratumour heterogeneity, particularly in the clinical setting, has been difficult to quantify and therefore to treat. The histological quantification of heterogeneity of tumours can be a logistical and clinical challenge. The ability to examine not just the whole tumour but also all the molecular variations of metastatic disease in a patient is obviously difficult with current histological techniques. Advances in imaging techniques and novel applications, alongside our understanding of tumour heterogeneity, have opened up a plethora of non-invasive biomarker potential to examine tumours, their heterogeneity and the clinical translation. This review will focus on how various imaging methods that allow for quantification of metastatic tumour heterogeneity, along with the potential of developing imaging, integrated with other in vitro diagnostic approaches such as genomics and exosome analyses, have the potential role as a non-invasive biomarker for guiding the treatment algorithm.

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

Previous in vitro studies demonstrated that treating tumors expressing both epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 with trastuzumab resulted in increased EGFR homodimerization and subsequent rapid downregulation of EGFR. We investigated whether molecular imaging using near-infrared fluorescence (NIRF) imaging and PET probes could sensitively detect trastuzumab-induced EGFR downregulation in vivo.

METHODS

The F(ab')2 antibody fragment PaniF(ab')2 was generated by digesting the anti-EGFR monoclonal antibody panitumumab. PaniF(ab')2 was labeled with either a NIRF dye or (68)Ga, and optical imaging and small-animal PET imaging of Dye-PaniF(ab')2 and (68)Ga-PaniF(ab')2, respectively, were performed in HT-29 tumor-bearing nude mice treated with trastuzumab or untreated control.

RESULTS

Longitudinal NIRF imaging studies revealed significantly reduced tumor uptake of Dye-PaniF(ab')2 on days 5 and 7 in trastuzumab-treated HT-29 tumors, compared with control. Western blotting confirmed the downregulation of EGFR after treatment with trastuzumab. Small-animal PET on day 5 after trastuzumab treatment also demonstrated decreased (68)Ga-PaniF(ab')2 uptake in trastuzumab-treated HT-29 tumors. The tumor uptake value of (68)Ga-PaniF(ab')2 obtained from PET imaging had an excellent linear correlation with the uptake value measured using biodistribution.

CONCLUSION

The downregulation of EGFR induced by trastuzumab treatment could be detected noninvasively using optical and PET imaging. This molecular imaging strategy could provide a dynamic readout of changes in the tumor signaling and may facilitate the noninvasive monitoring of the early tumor response to drug treatment.

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.