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NVP-AUY922, a potent heat shock protein (HSP) 90 inhibitor, downregulates the expression of many oncogenic proteins, including the human epidermal growth factor receptor-2 (HER2). Because HER2 downregulation is a potential biomarker for early response to HSP90-targeted therapies, we used the (89)Zr-labelled HER2 antibody trastuzumab to quantify the alterations in HER2 expression after NVP-AUY922 treatment with HER2 positron emission tomography (PET) imaging. The HER2 overexpressing human SKOV-3 ovarian tumour cell line was used for in vitro experiments and as xenograft model in nude athymic mice. In vitro HER2 membrane expression was assessed by flow cytometry and a radio-immuno assay with (89)Zr-trastuzumab. For in vivo evaluation, mice received 50mg/kg NVP-AUY922 intraperitoneally every other day. (89)Zr-trastuzumab was injected intravenously 6d before NVP-AUY922 treatment and after 3 NVP-AUY922 doses. MicroPET imaging was performed at 24, 72 and 144h post tracer injection followed by ex-vivo biodistribution and immunohistochemical staining. After 24h NVP-AUY922 treatment HER2 membrane expression showed profound reduction with flow cytometry (80%) and radio-immuno assay (75%). PET tumour quantification, showed a mean reduction of 41% (p=0.0001) in (89)Zr-trastuzumab uptake at 144h post tracer injection after NVP-AUY922 treatment. PET results were confirmed by ex-vivo (89)Zr-trastuzumab biodistribution and HER2 immunohistochemical staining. NVP-AUY922 effectively downregulates HER2, which can be monitored and quantified in vivo non-invasively with (89)Zr-trastuzumab PET. This technique is currently under clinical evaluation and might serve as an early biomarker for HSP90 inhibition in HER2 positive metastatic breast cancer patients. [ABSTRACT FROM AUTHOR]

Multispecific antibodies are engineered antibody derivatives that can bind to two or more distinct epitopes or antigens. Unlike mixtures of monospecific antibodies, the binding properties of multispecific antibodies enable two specific molecules to be physically linked, a characteristic with important applications in cancer therapy. The field of multispecific antibodies is highly dynamic and expanding rapidly; to date, 15 multispecific antibodies have been approved for clinical use, of which 11 were approved for oncological indications, and more than 100 new antibodies are currently in clinical development. Nevertheless, substantial challenges limit the applications of multispecific antibodies in cancer therapy, particularly inefficient targeting of solid tumours and substantial adverse effects. Both PET and single photon emission CT imaging can reveal the biodistribution and complex pharmacology of radiolabelled multispecific antibodies. This Review summarizes the insights obtained from preclinical and clinical molecular imaging studies of multispecific antibodies, focusing on their structural properties, such as molecular weight, shape, target specificity, affinity and avidity. The opportunities associated with use of molecular imaging studies to support the clinical development of multispecific antibody therapies are also highlighted., Competing Interests: Competing interests D.J.A.d.G. declares that he received institutional financial support for clinical trials or contracted research from Amgen, Bayer, GE Healthcare, Hoffmann La Roche and Siemens. E.G.E.d.V. declares that she received institutional financial support for acting as a member of advisory boards or consultancy services from Crescendo Biologics, Daiichi Sankyo and NSABP, as well as institutional financial support for clinical trials or contracted research grants from Amgen, Bayer, Crescendo Biologics, Genentech, Regeneron, Roche and Servier. M.N.L.-d.H. declares that she received institutional financial support for acting as a member of advisory boards or consultancy services from Merck and institutional financial support for conducting clinical and preclinical studies from Amgen, Bayer and Servier. The other authors declare no competing interests., (© 2024. Springer Nature Limited.)

Understanding which patients with human epidermal growth factor receptor 2 (HER2)-negative or -low metastatic breast cancer (MBC) benefit from HER2-targeted strategies is urgently needed. We assessed the whole-body heterogeneity of HER2 expression on 89 Zr-trastuzumab PET (HER2 PET) and the diagnostic performance of HER2 PET in a large series of patients, including HER2-negative and -low MBC. Methods: In the IMPACT-MBC study, patients with newly diagnosed and nonrapidly progressive MBC of all subtypes were included. Metastasis HER2 status was determined by immunohistochemistry and in situ hybridization. 89 Zr-trastuzumab uptake was quantified as SUV max and SUV mean HER2 immunohistochemistry was related to the quantitative 89 Zr-trastuzumab uptake of all metastases and corresponding biopsied metastasis, uptake heterogeneity, and qualitative scan evaluation. A prediction algorithm for HER2 immunohistochemistry positivity based on uptake was developed. Results: In 200 patients, 89 Zr-trastuzumab uptake was quantified in 5,163 metastases, including 186 biopsied metastases. With increasing HER2 immunohistochemistry status, uptake was higher (geometric mean SUV max of 7.0, 7.6, 7.3, and 17.4 for a HER2 immunohistochemistry score of 0, 1, 2, or 3+, respectively; P < 0.001). High uptake exceeding 14.6 (90th percentile) was observed in one third of patients with a HER2-negative or -low metastasis biopsy. The algorithm performed best when lesion site and size were incorporated (area under the curve, 0.86; 95% CI, 0.79-0.93). Conclusion: HER2 PET had good diagnostic performance in MBC, showing considerable whole-body HER2 heterogeneity and uptake above background in HER2-negative and -low MBC. This provides novel insights into HER2-negative and -low MBC compared with standard HER2 immunohistochemistry on a single biopsy., (© 2024 by the Society of Nuclear Medicine and Molecular Imaging.)

Current immunotherapies have brought major progress in cancer treatments, but not all patients benefit. Therefore, insight into reasons for treatment failure and optimal biomarkers for patient selection are warranted. Current approved biomarkers for cancer immunotherapy do not provide insight into characteristics across tumor lesions in a patient or their heterogeneity. Here, whole-body positron emission tomography (PET) imaging with specific tracers may provide support. Moreover, the biodistribution of cell therapies and complex molecules, such as bispecific antibodies, can be visualized by PET imaging, and repeat PET imaging allows to study the whole-body kinetics of the immune response. In this review, we present the status of using PET imaging-derived biomarkers for patients with cancer receiving immunotherapy. Next, the hopes and scientific challenges ahead to optimize current PET imaging biomarker development and to discover novel PET-derived baseline and dynamic biomarkers to potentially guide us in drug development and more precise patient and therapy selection will be discussed.

Objective: Improving patient selection and development of biological therapies such as vedolizumab in IBD requires a thorough understanding of the mechanism of action and target binding, thereby providing individualised treatment strategies. We aimed to visualise the macroscopic and microscopic distribution of intravenous injected fluorescently labelled vedolizumab, vedo-800CW, and identify its target cells using fluorescence molecular imaging (FMI)., Design: Forty three FMI procedures were performed, which consisted of macroscopic in vivo assessment during endoscopy, followed by macroscopic and microscopic ex vivo imaging. In phase A, patients received an intravenous dose of 4.5 mg, 15 mg vedo-800CW or no tracer prior to endoscopy. In phase B, patients received 15 mg vedo-800CW preceded by an unlabelled (sub)therapeutic dose of vedolizumab., Results: FMI quantification showed a dose-dependent increase in vedo-800CW fluorescence intensity in inflamed tissues, with 15 mg (153.7 au (132.3-163.7)) as the most suitable tracer dose compared with 4.5 mg (55.3 au (33.6-78.2)) (p=0.0002). Moreover, the fluorescence signal decreased by 61% when vedo-800CW was administered after a therapeutic dose of unlabelled vedolizumab, suggesting target saturation in the inflamed tissue. Fluorescence microscopy and immunostaining showed that vedolizumab penetrated the inflamed mucosa and was associated with several immune cell types, most prominently with plasma cells., Conclusion: These results indicate the potential of FMI to determine the local distribution of drugs in the inflamed target tissue and identify drug target cells, providing new insights into targeted agents for their use in IBD., Trial Registration Number: NCT04112212., Competing Interests: Competing interests: GD received research grants from Royal DSM, Takeda and Janssen Pharmaceuticals and speaker fees from AbbVie, Pfizer, Takeda and Janssen Pharmaceuticals. EAMF is supported by a ZonMW Clinical Fellowship grant (project number 90719075) and has received an unrestricted research grant from Takeda. MD and SJ are employees and shareholders of Regeneron Pharmaceuticals., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Monoclonal antibodies are important cancer medicines. The European Medicines Agency (EMA) approved 48 and the Food and Drug Administration (FDA) 56 anticancer monoclonal antibody-based therapies. Their high prices burden healthcare systems and hamper global drug access. Biosimilars could retain costs and expand the availability of monoclonal antibodies. In Europe, five rituximab biosimilars, six trastuzumab biosimilars, and eight bevacizumab biosimilars are available as anti-cancer drugs. To gain insight into the biosimilar landscape for cancer treatment, we performed a literature search and analysis. In this review, we summarize cancer monoclonal antibodies' properties crucial for the desired pharmacology and point out sources of variability. The analytical assessment of all EMA-approved bevacizumab biosimilars is highlighted to illustrate this variability. The global landscape of investigational and approved biosimilars is mapped, and the challenges for access to cancer biosimilars are identified., Competing Interests: E.G.E.d.V. reports institutional financial support for advisory boards/consultancy from NSABP, Daiichi Sankyo, and Crescendo Biologics and institutional financial support for clinical trials or contracted research grants from Amgen, Genentech, Roche, Bayer, Servier, Regeneron, and Crescendo Biologics, all outside this work., (© 2024 The Authors.)

Immuno-positron emission tomography (immunoPET) enables imaging of specific targets that play a role in targeted therapy and immunotherapy, such as antigens on cell membranes, targets in the disease microenvironment, or immune cells. The most common immunoPET applications use a monoclonal antibody labeled with a relatively long-lived positron emitter such as 89 Zr ( T 1/2  = 78.4 h), but smaller antibody-based constructs labeled with various other positron emitting radionuclides are also being investigated. This molecular imaging technique can thus guide the development of new drugs and may have a pivotal role in selecting patients for a particular therapy. In early phase immunoPET trials, multiple imaging time points are used to examine the time-dependent biodistribution and to determine the optimal imaging time point, which may be several days after tracer injection due to the slow kinetics of larger molecules. Once this has been established, usually only one static scan is performed and semi-quantitative values are reported. However, total PET uptake of a tracer is the sum of specific and nonspecific uptake. In addition, uptake may be affected by other factors such as perfusion, pre-/co-administration of the unlabeled molecule, and the treatment schedule. This article reviews imaging methodologies used in immunoPET studies and is divided into two parts. The first part summarizes the vast majority of clinical immunoPET studies applying semi-quantitative methodologies. The second part focuses on a handful of studies applying pharmacokinetic models and includes preclinical and simulation studies. Finally, the potential and challenges of immunoPET quantification methodologies are discussed within the context of the recent technological advancements provided by long axial field of view PET/CT scanners., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (© 2024 Mohr, van Sluis, Lub-de Hooge, Lammertsma, Brouwers and Tsoumpas.)

The purpose of this study was to quantify any differences between the SUVs of 89 Zr immuno-PET scans obtained using a PET/CT system with a long axial field of view (LAFOV; Biograph Vision Quadra) compared to a PET/CT system with a short axial field of view (SAFOV; Biograph Vision) and to evaluate how LAFOV PET scan duration affects image noise and SUV metrics. Methods: Five metastatic breast cancer patients were scanned consecutively on SAFOV and LAFOV PET/CT scanners. Four additional patients were scanned using only LAFOV PET/CT. Scans on both systems lasted approximately 30 min and were acquired 4 d after injection of 37 MBq of 89 Zr-trastuzumab. LAFOV list-mode data were reprocessed to obtain images acquired using shorter scan durations (15, 10, 7.5, 5, and 3 min). Volumes of interest were placed in healthy tissues, and tumors were segmented semiautomatically to compare coefficients of variation and to perform Bland-Altman analysis on SUV metrics (SUV max , SUV peak , and SUV mean ). Results: Using 30-min images, 2 commonly used lesion SUV metrics were higher for SAFOV than for LAFOV PET (SUV max , 16.2% ± 13.4%, and SUV peak , 10.1% ± 7.2%), whereas the SUV mean of healthy tissues showed minimal differences (0.7% ± 5.8%). Coefficients of variation in the liver derived from 30-min SAFOV PET were between those of 3- and 5-min LAFOV PET. The smallest SUV max and SUV peak differences between SAFOV and LAFOV were found for 3-min LAFOV PET. Conclusion: LAFOV 89 Zr immuno-PET showed a lower SUV max and SUV peak than SAFOV because of lower image noise. LAFOV PET scan duration may be reduced at the expense of increasing image noise and bias in SUV metrics. Nevertheless, SUV peak showed only minimal bias when reducing scan duration from 30 to 10 min., (© 2023 by the Society of Nuclear Medicine and Molecular Imaging.)

Purpose: As novel tracers are continuously under development, it is important to obtain reliable radiation dose estimates to optimize the amount of activity that can be administered while keeping radiation burden within acceptable limits. Organ segmentation is required for quantification of specific uptake in organs of interest and whole-body dosimetry but is a time-consuming task which induces high interobserver variability. Therefore, we explored using manual segmentations versus an artificial intelligence (AI)-based automated segmentation tool as a pre-processing step for calculating whole-body effective doses to determine the influence of variability in volumetric whole-organ segmentations on dosimetry., Procedures: PET/CT data of six patients undergoing imaging with 89 Zr-labelled pembrolizumab were included. Manual organ segmentations were performed, using in-house developed software, and biodistribution information was obtained. Based on the activity biodistribution information, residence times were calculated. The residence times served as input for OLINDA/EXM version 1.0 (Vanderbilt University, 2003) to calculate the whole-body effective dose (mSv/MBq). Subsequently, organ segmentations were performed using RECOMIA, a cloud-based AI platform for nuclear medicine and radiology research. The workflow for calculating residence times and whole-body effective doses, as described above, was repeated., Results: Data were acquired on days 2, 4, and 7 post-injection, resulting in 18 scans. Overall analysis time per scan was approximately 4 h for manual segmentations compared to ≤ 30 min using AI-based segmentations. Median Jaccard similarity coefficients between manual and AI-based segmentations varied from 0.05 (range 0.00-0.14) for the pancreas to 0.78 (range 0.74-0.82) for the lungs. Whole-body effective doses differed minimally for the six patients with a median difference in received mSv/MBq of 0.52% (range 0.15-1.95%)., Conclusion: This pilot study suggests that whole-body dosimetry calculations can benefit from fast, automated AI-based whole organ segmentations., (© 2022. The Author(s).)

Immune checkpoint inhibitors (ICIs), by reinvigorating CD8 + T cell mediated immunity, have revolutionized cancer therapy. Yet, the systemic CD8 + T cell distribution, a potential biomarker of ICI response, remains poorly characterized. We assessed safety, imaging dose and timing, pharmacokinetics and immunogenicity of zirconium-89-labeled, CD8-specific, one-armed antibody positron emission tomography tracer 89 ZED88082A in patients with solid tumors before and ~30 days after starting ICI therapy (NCT04029181). No tracer-related side effects occurred. Positron emission tomography imaging with 10 mg antibody revealed 89 ZED88082A uptake in normal lymphoid tissues, and tumor lesions across the body varying within and between patients two days after tracer injection (n = 38, median patient maximum standard uptake value (SUV max ) 5.2, IQI 4.0-7.4). Higher SUV max was associated with mismatch repair deficiency and longer overall survival. Uptake was higher in lesions with stromal/inflamed than desert immunophenotype. Tissue radioactivity was localized to areas with immunohistochemically confirmed CD8 expression. Re-imaging patients on treatment showed no change in average (geometric mean) tumor tracer uptake compared to baseline, but individual lesions showed diverse changes independent of tumor response. The imaging data suggest enormous heterogeneity in CD8 + T cell distribution and pharmacodynamics within and between patients. In conclusion, 89 ZED88082A can characterize the complex dynamics of CD8 + T cells in the context of ICIs, and may inform immunotherapeutic treatments., (© 2022. The Author(s).)

The mesothelin (MSLN)-targeted 227 Th conjugate is a novel α-therapy developed to treat MSLN-overexpressing cancers. We radiolabeled the same antibody-chelator conjugate with 89 Zr to evaluate whether PET imaging with 89 Zr-MSLN matches 227 Th-MSLN tumor uptake, biodistribution, and antitumor activity. Methods: Serial PET imaging with protein doses of 4, 20, or 40 μg of 89 Zr-MSLN and 89 Zr-control was performed up to 168 h after tracer injection in human tumor-bearing nude mice with high (HT29-MSLN) and low (BxPc3) MSLN expression. 89 Zr-MSLN and 227 Th-MSLN ex vivo tumor uptake and biodistribution were compared at 6 time points in HT29-MSLN and in medium-MSLN-expressing (OVCAR-3) tumor-bearing mice. 89 Zr-MSLN PET imaging was performed before 227 Th-MSLN treatment in HT29-MSLN and BxPc3 tumor-bearing mice. Results: 89 Zr-MSLN PET imaging showed an SUV mean of 2.2 ± 0.5 in HT29-MSLN tumors. Ex vivo tumor uptake was 10.6% ± 2.4% injected dose per gram at 168 h. 89 Zr-MSLN tumor uptake was higher than uptake of 89 Zr-control ( P = 0.0043). 89 Zr-MSLN and 227 Th-MSLN showed comparable tumor uptake and biodistribution in OVCAR-3 and HT29-MSLN tumor-bearing mice. Pretreatment SUV mean was 2.2 ± 0.2 in HT29-MSLN tumors, which decreased in volume on 227 Th-MSLN treatment. BxPc3 tumors showed an SUV mean of 1.2 ± 0.3 and remained similar in size after 227 Th-MSLN treatment. Conclusion: 89 Zr-MSLN PET imaging reflected MSLN expression and matched 227 Th-MSLN tumor uptake and biodistribution. Our data support the clinical exploration of 89 Zr-MSLN PET imaging together with 227 Th-MSLN therapy, both using the same antibody-chelator conjugate., (© 2022 by the Society of Nuclear Medicine and Molecular Imaging.)

The advent of immune checkpoint inhibitors has reinvigorated the field of immuno-oncology. These monoclonal antibody-based therapies allow the immune system to recognize and eliminate malignant cells. This has resulted in improved survival of patients across several tumor types. However, not all patients respond to immunotherapy therefore predictive biomarkers are important. There are only a few Food and Drug Administration-approved biomarkers to select patients for immunotherapy. These biomarkers do not consider the heterogeneity of tumor characteristics across lesions within a patient. New molecular imaging tracers allow for whole-body visualization with positron emission tomography (PET) of tumor and immune cell characteristics, and drug distribution, which might guide treatment decision making. Here, we summarize recent developments in molecular imaging of immune checkpoint molecules, such as PD-L1, PD-1, CTLA-4, and LAG-3. We discuss several molecular imaging approaches of immune cell subsets and briefly summarize the role of FDG-PET for evaluating cancer immunotherapy. The main focus is on developments in clinical molecular imaging studies, next to preclinical studies of interest given their potential translation to the clinic., Competing Interests: Competing interests: EDV reports an advisory role at Daiichi Sankyo, NSABP, and Sanofi and research funding from Amgen, AstraZeneca, Bayer, Chugai Pharma, Crescendo, CytomX Therapeutics, G1 Therapeutics, Genentech, Nordic Nanovector, Radius Health, Regeneron, Roche, Servier, and Synthon (paid to UMCG). AvdW reports an advisory role at Janssen, Takeda, and Boehringer-Ingelheim (paid to UMCG) and research funding from AstraZeneca, Boehringer-Ingelheim, Pfizer, Roche, and Takeda. ML-dH reports research funding from Merck, Bayer, and Amgen (paid to UMCG). SO reports research funding from Novartis, Pfizer and Celldex Therapeutics (paid to UMCG) and an advisory role at Bristol Myers Squibb (paid to the UMCG)., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Due to ethical and practical reasons, a knowledge gap exists on the pharmacokinetics (PK) of inflammatory bowel disease (IBD)-related drugs in pregnant women with IBD. Before evidence-based dosing can be proposed, insight into the PK has to be gained to optimize drug therapy for both mother and fetus. This systematic review aimed to describe the effect of pregnancy and IBD on the PK of drugs used for IBD. One aminosalicylate study, two thiopurine studies and twelve studies with biologicals were included. Most drugs within these groups presented data over multiple moments before, during and after pregnancy, except for mesalazine, ustekinumab and golimumab. The studies for mesalazine, ustekinumab and golimumab did not provide enough data to demonstrate an effect of pregnancy on concentration and PK parameters. Therefore, no evidence-based dosing advice was given. The 6-thioguanine nucleotide levels decreased during pregnancy to 61% compared to pre-pregnancy levels. The potentially toxic metabolite 6-methylmercaptopurine (6-MMP) increased to maximal 209% of the pre-pregnancy levels. Although the PK of the thiopurines changed throughout pregnancy, no evidence-based dosing advice was provided. One study suggested that caution should be exercised when the thiopurine dose is adjusted, due to shunting 6-MMP levels. For the biologicals, infliximab levels increased, adalimumab stayed relatively stable and vedolizumab levels tended to decrease during pregnancy. Although the PK of the biologicals changed throughout pregnancy, no evidence-based dosing advice for biologicals was provided. Other drugs retrieved from the literature search were mesalazine, ustekinumab and golimumab. We conclude that limited studies have been performed on PK parameters during pregnancy for drugs used in IBD. Therefore, more extensive research to determine the values of PK parameters is warranted. After gathering the PK data, evidence-based dosing regimens can be developed.

Background: Programmed cell death protein 1 (PD-1) antibody treatment is standard of care for melanoma and non-small-cell lung cancer (NSCLC). Accurately predicting which patients will benefit is currently not possible. Tumor uptake and biodistribution of the PD-1 antibody might play a role. Therefore, we carried out a positron emission tomography (PET) imaging study with zirconium-89 ( 89 Zr)-labeled pembrolizumab before PD-1 antibody treatment., Patients and Methods: Patients with advanced or metastatic melanoma or NSCLC received 37 MBq (1 mCi) 89 Zr-pembrolizumab (∼2.5 mg antibody) intravenously plus 2.5 or 7.5 mg unlabeled pembrolizumab. After that, up to three PET scans were carried out on days 2, 4, and 7. Next, PD-1 antibody treatment was initiated. 89 Zr-pembrolizumab tumor uptake was calculated as maximum standardized uptake value (SUV max ) and expressed as geometric mean. Normal organ uptake was calculated as SUV mean and expressed as a mean. Tumor response was assessed according to (i)RECIST v1.1., Results: Eighteen patients, 11 with melanoma and 7 with NSCLC, were included. The optimal dose was 5 mg pembrolizumab, and the optimal time point for PET scanning was day 7. The tumor SUV max did not differ between melanoma and NSCLC (4.9 and 6.5, P = 0.49). Tumor 89 Zr-pembrolizumab uptake correlated with tumor response (P trend = 0.014) and progression-free (P = 0.0025) and overall survival (P = 0.026). 89 Zr-pembrolizumab uptake at 5 mg was highest in the spleen with a mean SUV mean of 5.8 (standard deviation ±1.8). There was also 89 Zr-pembrolizumab uptake in Waldeyer's ring, in normal lymph nodes, and at sites of inflammation., Conclusion: 89 Zr-pembrolizumab uptake in tumor lesions correlated with treatment response and patient survival. 89 Zr-pembrolizumab also showed uptake in lymphoid tissues and at sites of inflammation., Competing Interests: Disclosure MJ reports consultancy fees from AstraZeneca (paid to UMCG). JBH reports consultancy roles for Achilles Therapeutics, BioNTech, BMS, GSK, Immunocore, Instil Bio, Molecular Partners, MSD, Merck Serono, Neogene Therapeutics, Novartis, Pfizer, PokeAcel, Roche/Genentech, Sanofi, T-Knife, and Third Rock Ventures and research grants from Amgen, Asher-Bio, BMS, BioNTech, MSD, Novartis, and Neogene Therapeutics (paid to the Netherlands Cancer Institute). WT reports fees from Merck, Sharp, Dohme, and Bristol-Myers-Squibb (paid to UMCG). EGEdV reports an advisory role at Daiichi Sankyo, NSABP, and Sanofi and research funding from Amgen, AstraZeneca, Bayer, Chugai Pharma, Crescendo, CytomX Therapeutics, G1 Therapeutics, Genentech, Nordic Nanovector, Radius Health, Regeneron, Roche, Servier, and Synthon (paid to UMCG). GAPH reports consulting and advisory role at Amgen, Roche, MSD, BMS, Pfizer, Novartis, and Pierre Fabry and research funding from BMS and Seerave (paid to UMCG). TJNH reports consultancy fees (paid to UMCG) from BMS, MSD, Merck, Boehringer, AstraZeneca, and Roche. AJvdW reports an advisory role at Janssen, Takeda, and Boehringer-Ingelheim (paid to UMCG) and research funding from AstraZeneca, Boehringer-Ingelheim, Pfizer, Roche, and Takeda. MNL-dH reports research funding from Merck, Bayer, and Amgen (paid to UMCG). HJMG reports an advisory role at Eli Lilly, MSD, BMS, and Novartis. All other authors have declared no conflicts of interest., (Copyright © 2021. Published by Elsevier Ltd.)

Macrophages can promote tumor development. Preclinically, targeting macrophages by colony-stimulating factor 1 (CSF1)/CSF1 receptor (CSF1R) monoclonal antibodies (mAbs) enhances conventional therapeutics in combination treatments. The physiological distribution and tumor uptake of CSF1R mAbs are unknown. Therefore, we radiolabeled a murine CSF1R mAb and preclinically visualized its biodistribution by PET. CSF1R mAb was conjugated to N -succinyl-desferrioxamine ( N -suc-DFO) and subsequently radiolabeled with zirconium-89 ( 89 Zr). Optimal protein antibody dose was first determined in non-tumor-bearing mice to assess physiological distribution. Next, biodistribution of optimal protein dose and 89 Zr-labeled isotype control was compared with PET and ex vivo biodistribution after 24 and 72 h in mammary tumor-bearing mice. Tissue autoradiography and immunohistochemistry determined radioactivity distribution and tissue macrophage presence, respectively. [ 89 Zr]Zr-DFO- N -suc-CSF1R-mAb optimal protein dose was 10 mg/kg, with blood pool levels of 10 ± 2% injected dose per gram tissue (ID/g) and spleen and liver uptake of 17 ± 4 and 11 ± 4%ID/g at 72 h. In contrast, 0.4 mg/kg of [ 89 Zr]Zr-DFO- N -suc-CSF1R mAb was eliminated from circulation within 24 h; spleen and liver uptake was 126 ± 44% and 34 ± 7%ID/g, respectively. Tumor-bearing mice showed higher uptake of [ 89 Zr]Zr-DFO- N -suc-CSF1R-mAb in the liver, lymphoid tissues, duodenum, and ileum, but not in the tumor than did 89 Zr-labeled control at 72 h. Immunohistochemistry and autoradiography showed that 89 Zr was localized to macrophages within lymphoid tissues. Following [ 89 Zr]Zr-DFO- N -suc-CSF1R-mAb administration, tumor macrophages were almost absent, whereas isotype-group tumors contained over 500 cells/mm 2 . We hypothesize that intratumoral macrophage depletion by [ 89 Zr]Zr-DFO- N -suc-CSF1R-mAb precluded tumor uptake higher than 89 Zr-labeled control. Translation of molecular imaging of macrophage-targeting therapeutics to humans may support macrophage-directed therapeutic development., Competing Interests: EV reports institutional financial support for her advisory role from Daiichi Sankyo, Merck, NSABP, Pfizer, Sanofi, and Synthon and institutional financial support for clinical trials or contracted research from Amgen, AstraZeneca, Bayer, Chugai Pharma, CytomX Therapeutics, G1 Therapeutics, Genentech, Nordic Nanovector, Radius Health, Roche, Synthon, and Servier. CS reports receiving unrestricted research grants from Novartis, Roche, Genentech, Pfizer, SNS Oncology, and G1 Therapeutics that were made available to UMCG. KdV reports receiving research grants from Roche and is a consultant for Third Rock Ventures. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Waaijer, Suurs, Hau, Vrijland, de Visser, de Groot, de Vries, Lub-de Hooge and Schröder.)

Purpose: CX-072, a PD-L1-targeting Probody therapeutic, is engineered to be activated by tumor proteases that remove a masking peptide. To study effects on biodistribution and pharmacokinetics, we performed 89Zr-CX-072 positron emission tomography (PET) imaging., Experimental Design: Patients received ∼1 mg, 37 MBq 89Zr-CX-072 plus 0, 4, or 9 mg unlabeled CX-072 and PET scans at days 2, 4, and 7. After that, treatment comprised 10 mg/kg CX-072 q2 weeks (n = 7) + 3 mg/kg ipilimumab q3w 4× (n = 1). Normal organ tracer uptake was expressed as standardized uptake value (SUV)mean and tumor uptake as SUVmax. PD-L1 expression was measured immunohistochemically in archival tumor tissue., Results: Three of the eight patients included received 10-mg protein dose resulting in a blood pool mean SUVmean ± SD of 4.27 ± 0.45 on day 4, indicating sufficient available tracer. Tumor uptake was highest at day 7, with a geometric mean SUVmax 5.89 (n = 113) and present in all patients. The median follow-up was 12 weeks (4-76+). One patient experienced stable disease and two patients a partial response. PD-L1 tumor expression was 90% in one patient and ≤1% in the other patients. Mean SUVmean ± SD day 4 at 10 mg in the spleen was 8.56 ± 1.04, bone marrow 2.21 ± 0.46, and liver 4.97 ± 0.97. Four patients out of seven showed uptake in normal lymph nodes and Waldeyer's ring. The tracer was intact in the serum or plasma., Conclusions: 89Zr-CX-072 showed tumor uptake, even in lesions with ≤1% PD-L1 expression, and modest uptake in normal lymphoid organs, with no unexpected uptake in other healthy tissues., (©2021 American Association for Cancer Research.)

This review describes acetaminophen pharmacokinetics (PK) throughout pregnancy, as analyzed by three methods (non-compartmental analyses (NCA), population PK, and physiologically based PK (PBPK) modelling). Eighteen studies using NCA were reported in the scientific literature. These studies reported an increase in the volume of distribution (3.5-60.7%) and an increase in the clearance (36.8-84.4%) of acetaminophen in pregnant women compared to non-pregnant women. Only two studies using population PK modelling as a technique were available in the literature. The largest difference in acetaminophen clearance (203%) was observed in women at delivery compared to non-pregnant women. One study using the PBPK technique was found in the literature. This study focused on the formation of metabolites, and the toxic metabolite N-acetyl-p-benzoquinone imine was the highest in the first trimester, followed by the second and third trimester, compared with non-pregnant women. In conclusion, this review gave an overview on acetaminophen PK changes in pregnancy. Also, knowledge gaps, such as fetal and placenta PK parameters, have been identified, which should be explored further before dosing adjustments can be suggested on an evidence-based basis.

BiTE ® (bispecific T-cell engager) molecules exert antitumor activity by binding one arm to CD3 on cytotoxic T-cells and the other arm to a tumor-associated antigen. We generated a fully mouse cross-reactive mesothelin (MSLN)-targeted BiTE molecule that is genetically fused to a Fc-domain for half-life extension, and evaluated biodistribution and tumor targeting of a zirconium-89 ( 89 Zr)-labeled MSLN HLE BiTE molecule in 4T1 breast cancer bearing syngeneic mice with positron emission tomography (PET). Biodistribution of 50 µg 89 Zr-MLSN HLE BiTE was studied over time by PET imaging in BALB/c mice and revealed uptake in tumor and lymphoid tissues with an elimination half-life of 63.4 hours. Compared to a non-targeting 89 Zr-control HLE BiTE, the 89 Zr-MLSN HLE BiTE showed a 2-fold higher tumor uptake and higher uptake in lymphoid tissues. Uptake in the tumor colocalized with mesothelin expression, while uptake in the spleen colocalized with CD3 expression. Evaluation of the effect of protein doses on the biodistribution and tumor targeting of 89 Zr-MSLN HLE BiTE revealed for all dose groups that uptake in the spleen was faster than in the tumor (day 1 vs day 5). The lowest dose of 10 µg 89 Zr-MSLN HLE BiTE had higher spleen uptake and faster blood clearance compared to higher doses of 50 µg and 200 µg. 89 Zr-MSLN HLE BiTE tumor uptake was similar at all doses. Conclusion: The MSLN HLE BiTE showed specific tumor uptake and both arms contributed to the biodistribution profile. These findings support the potential for clinical translation of HLE BiTE molecules., (Copyright © 2021 by the Society of Nuclear Medicine and Molecular Imaging, Inc.)

Purpose: Programmed cell death-1 receptor (PD-1) and its ligand (PD-L1) are the targets for immunotherapy in many cancer types. Although PD-1 blockade has therapeutic effects, the efficacy differs between patients. Factors contributing to this variability are PD-L1 expression levels and immune cells present in tumors. However, it is not well understood how PD-1 expression in the tumor microenvironment impacts immunotherapy response. Thus, imaging of PD-1-expressing immune cells is of interest. This study aims to evaluate the biodistribution of Zirconium-89 ( 89 Zr)-labeled pembrolizumab, a humanized IgG4 kappa monoclonal antibody targeting PD-1, in healthy cynomolgus monkeys as a translational model of tracking PD-1-positive immune cells., Procedures: Pembrolizumab was conjugated with the tetrafluorophenol-N-succinyl desferal-Fe(III) ester (TFP-N-sucDf) and subsequently radiolabeled with 89 Zr. Four cynomolgus monkeys with no previous exposure to humanized monoclonal antibodies received tracer only or tracer co-injected with pembrolizumab intravenously over 5 min. Thereafter, a static whole-body positron emission tomography (PET) scan was acquired with 10 min per bed position on days 0, 2, 5, and 7. Image-derived standardized uptake values (SUV mean ) were quantified by region of interest (ROI) analysis., Results: 89 Zr-N-sucDf-pembrolizumab was synthesized with high radiochemical purity (> 99 %) and acceptable molar activity (> 7 MBq/nmol). In animals dosed with tracer only, 89 Zr-N-sucDf-pembrolizumab distribution in lymphoid tissues such as mesenteric lymph nodes, spleen, and tonsils increased over time. Except for the liver, low radiotracer distribution was observed in all non-lymphoid tissue including the lung, muscle, brain, heart, and kidney. When a large excess of pembrolizumab was co-administered with a radiotracer, accumulation in the lymph nodes, spleen, and tonsils was reduced, suggestive of target-mediated accumulation., Conclusions: 89 Zr-N-sucDf-pembrolizumab shows preferential uptake in the lymphoid tissues including the lymph nodes, spleen, and tonsils. 89 Zr-N-sucDf-pembrolizumab may be useful in tracking the distribution of a subset of immune cells in non-human primates and humans., Trial Registration: ClinicalTrials.gov Identifier: NCT02760225.

18 F-BMS-986192, an adnectin-based human programmed cell death ligand 1 (PD-L1) tracer, was developed to noninvasively determine whole-body PD-L1 expression by PET. We evaluated the usability of 18 F-BMS-986192 PET to detect different PD-L1 expression levels and therapy-induced changes in PD-L1 expression in tumors. Methods: In vitro binding assays with 18 F-BMS-986192 were performed on human tumor cell lines with different total cellular and membrane PD-L1 protein expression levels. Subsequently, PET imaging was performed on immunodeficient mice xenografted with these cell lines. The mice were treated with interferon γ (IFNγ) intraperitoneally for 3 d or with the mitogen-activated protein kinase kinase inhibitor selumetinib by oral gavage for 24 h. Afterward, 18 F-BMS-986192 was administered intravenously, followed by a 60-min dynamic PET scan. Tracer uptake was expressed as percentage injected dose per gram of tissue. Tissues were collected to evaluate ex vivo tracer biodistribution and to perform flow cytometric, Western blot, and immunohistochemical tumor analyses. Results: 18 F-BMS-986192 uptake reflected PD-L1 membrane levels in tumor cell lines, and tumor tracer uptake in mice was associated with PD-L1 expression measured immunohistochemically. In vitro IFNγ treatment increased PD-L1 expression in the tumor cell lines and caused up to a 12-fold increase in tracer binding. In vivo, IFNγ affected neither PD-L1 tumor expression measured immunohistochemically nor 18 F-BMS-986192 tumor uptake. In vitro, selumetinib downregulated cellular and membrane levels of PD-L1 in tumor cells by 50% as measured by Western blotting and flow cytometry. In mice, selumetinib lowered cellular, but not membrane, PD-L1 levels of tumors, and consequently, no treatment-induced change in 18 F-BMS-986192 tumor uptake was observed. Conclusion: 18 F-BMS-986192 PET imaging allows detection of membrane-expressed PD-L1 as soon as 60 min after tracer injection. The tracer can discriminate a range of tumor cell PD-L1 membrane expression levels., (© 2020 by the Society of Nuclear Medicine and Molecular Imaging.)

Bispecific T-cell engager (BiTE) molecules are designed to engage and activate cytotoxic T cells to kill tumor cells. Little is known about their biodistribution in immunocompetent settings. Methods: To explore their pharmacokinetics and the role of the immune cells, BiTE molecules were radiolabeled with the PET isotope 89 Zr and studied in immunocompetent and immunodeficient mouse models. Results: PET images and ex vivo biodistribution in immunocompetent mice with [ 89 Zr]Zr-DFO- N -suc-muS110, targeting mouse CD3 (dissociation constant [K D ], 2.9 nM) and mouse epithelial cell adhesion molecule (EpCAM; K D , 21 nM), and with [ 89 Zr]Zr-DFO- N -suc-hyS110, targeting only mouse CD3 (K D , 2.9 nM), showed uptake in the tumor, spleen, and other lymphoid organs, whereas the human-specific control BiTE [ 89 Zr]Zr-DFO- N -suc-AMG 110 showed similar tumor uptake but lacked spleen uptake. [ 89 Zr]Zr-DFO- N -suc-muS110 spleen uptake was lower in immunodeficient than in immunocompetent mice. After repeated administration of nonradiolabeled muS110 to immunocompetent mice, 89 Zr-muS110 uptake in the spleen and other lymphoid tissues decreased and was comparable to uptake in immunodeficient mice, indicating saturation of CD3 binding sites. Autoradiography and immunohistochemistry demonstrated colocalization of [ 89 Zr]Zr-DFO- N -suc-muS110 and [ 89 Zr]Zr-DFO- N -suc-hyS110 with CD3-positive T cells in the tumor and spleen but not with EpCAM expression. Also, uptake in the duodenum correlated with a high incidence of T cells. Conclusion: [ 89 Zr]Zr-DFO- N -suc-muS110 biodistribution is dependent mainly on the T-cell-targeting arm, with a limited contribution from its second arm, targeting EpCAM. These findings highlight the need for extensive biodistribution studies of novel bispecific constructs, as the results might have implications for their respective drug development and clinical translation., (© 2020 by the Society of Nuclear Medicine and Molecular Imaging.)

Background: To better predict response to immune checkpoint therapy and toxicity in healthy tissues, insight in the in vivo behavior of immune checkpoint targeting monoclonal antibodies is essential. Therefore, we aimed to study in vivo pharmacokinetics and whole-body distribution of zirconium-89 ( 89 Zr) labeled programmed cell death protein-1 (PD-1) targeting pembrolizumab with positron-emission tomography (PET) in humanized mice., Methods: Humanized (huNOG) and non-humanized NOG mice were xenografted with human A375M melanoma cells. PET imaging was performed on day 7 post 89 Zr-pembrolizumab (10 µg, 2.5 MBq) administration, followed by ex vivo biodistribution studies. Other huNOG mice bearing A375M tumors received a co-injection of excess (90 µg) unlabeled pembrolizumab or 89 Zr-IgG 4 control (10 µg, 2.5 MBq). Tumor and spleen tissue were studied with autoradiography and immunohistochemically including PD-1., Results: PET imaging and biodistribution studies showed high 89 Zr-pembrolizumab uptake in tissues containing human immune cells, including spleen, lymph nodes and bone marrow. Tumor uptake of 89 Zr-pembrolizumab was lower than uptake in lymphoid tissues, but higher than uptake in other organs. High uptake in lymphoid tissues could be reduced by excess unlabeled pembrolizumab. Tracer activity in blood pool was increased by addition of unlabeled pembrolizumab, but tumor uptake was not affected. Autoradiography supported PET findings and immunohistochemical staining on spleen and lymph node tissue showed PD-1 positive cells, whereas tumor tissue was PD-1 negative., Conclusion: 89 Zr-pembrolizumab whole-body biodistribution showed high PD-1-mediated uptake in lymphoid tissues, such as spleen, lymph nodes and bone marrow, and modest tumor uptake. Our data may enable evaluation of 89 Zr-pembrolizumab whole-body distribution in patients., Competing Interests: Competing interests: EGEdV reports grants from IMI TRISTAN (GA no.116106), during the conduct of the study; consulting and advisory role for NSABP, Daiichi Sankyo, Pfizer, Sanofi, Merck, Synthon Biopharmaceuticals; grants from Amgen, Genentech, Roche, Chugai Pharma, CytomX Therapeutics, Nordic Nanovector, G1 Therapeutics, AstraZeneca, Radius Health, Bayer, all made available to the institution, outside the submitted work., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Recently, N -(4- 18 F-fluorobenzoyl)-interleukin-2 ( 18 F-FB-IL2) was introduced as a PET tracer for T cell imaging. However, production is complex and time-consuming. Therefore, we developed 2 radiolabeled IL2 variants, namely aluminum 18 F-fluoride-(restrained complexing agent)-IL2 ( 18 F-AlF-RESCA-IL2) and 68 Ga-gallium-(1,4,7-triazacyclononane-4,7-diacetic acid-1-glutaric acid)-IL2 ( 68 Ga-Ga-NODAGA-IL2), and compared their in vitro and in vivo characteristics with 18 F-FB-IL2. Methods: Radiolabeling of 18 F-AlF-RESCA-IL2 and 68 Ga-Ga-NODAGA-IL2 was optimized, and stability was evaluated in human serum. Receptor binding was studied with activated human peripheral blood mononuclear cells (hPBMCs). Ex vivo tracer biodistribution in immunocompetent BALB/cOlaHsd (BALB/c) mice was performed at 15, 60, and 90 min after tracer injection. In vivo binding characteristics were studied in severe combined immunodeficient (SCID) mice inoculated with activated hPBMCs in Matrigel. Tracer was injected 15 min after hPBMC inoculation, and a 60-min dynamic PET scan was acquired, followed by ex vivo biodistribution studies. Specific uptake was determined by coinjection of tracer with unlabeled IL2 and by evaluating uptake in a control group inoculated with Matrigel only. Results: 68 Ga-Ga-NODAGA-IL2 and 18 F-AlF-RESCA-IL2 were produced with radiochemical purity of more than 95% and radiochemical yield of 13.1% ± 4.7% and 2.4% ± 1.6% within 60 and 90 min, respectively. Both tracers were stable in serum, with more than 90% being intact tracer after 1 h. In vitro, both tracers displayed preferential binding to activated hPBMCs. Ex vivo biodistribution studies on BALB/c mice showed higher uptake of 18 F-AlF-RESCA-IL2 than of 18 F-FB-IL2 in liver, kidney, spleen, bone, and bone marrow. 68 Ga-Ga-NODAGA-IL2 uptake in liver and kidney was higher than 18 F-FB-IL2 uptake. In vivo, all tracers revealed uptake in activated hPBMCs in SCID mice. Low uptake was seen after a blocking dose of IL2 and in the Matrigel control group. In addition, 18 F-AlF-RESCA-IL2 yielded the highest-contrast PET images of target lymph nodes. Conclusion: Production of 18 F-AlF-RESCA-IL2 and 68 Ga-Ga-NODAGA-IL2 is simpler and faster than that of 18 F-FB-IL2. Both tracers showed good in vitro and in vivo characteristics, with high uptake in lymphoid tissue and hPBMC xenografts., (© 2020 by the Society of Nuclear Medicine and Molecular Imaging.)

Purpose: Probody therapeutic CX-072 is a protease-activatable antibody that is cross-reactive with murine and human programmed death-ligand 1 (PD-L1). CX-072 can be activated in vivo by proteases present in the tumor microenvironment, thereby potentially reducing peripheral, anti-PD-L1-mediated toxicities. To study its targeting of PD-L1-expressing tissues, we radiolabeled CX-072 with the PET isotope zirconium-89 ( 89 Zr)., Experimental Design: 89 Zr-labeled CX-072, nonspecific Probody control molecule (PbCtrl) and CX-072 parental antibody (CX-075) were injected in BALB/c nude mice bearing human MDA-MB-231 tumors or C57BL/6J mice bearing syngeneic MC38 tumors. Mice underwent serial PET imaging 1, 3, and 6 days after intravenous injection (pi), followed by ex vivo biodistribution. Intratumoral 89 Zr-CX-072 distribution was studied by autoradiography on tumor tissue sections, which were subsequently stained for PD-L1 by IHC. Activated CX-072 species in tissue lysates were detected by Western capillary electrophoresis., Results: PET imaging revealed 89 Zr-CX-072 accumulation in MDA-MB-231 tumors with 2.1-fold higher tumor-to-blood ratios at 6 days pi compared with 89 Zr-PbCtrl. Tumor tissue autoradiography showed high 89 Zr-CX-072 uptake in high PD-L1-expressing regions. Activated CX-072 species were detected in these tumors, with 5.3-fold lower levels found in the spleen. Furthermore, 89 Zr-CX-072 uptake by lymphoid tissues of immune-competent mice bearing MC38 tumors was low compared with 89 Zr-CX-075, which lacks the Probody design., Conclusions: 89 Zr-CX-072 accumulates specifically in PD-L1-expressing tumors with limited uptake in murine peripheral lymphoid tissues. Our data may enable clinical evaluation of 89 Zr-CX-072 whole-body distribution as a tool to support CX-072 drug development (NCT03013491)., (©2020 American Association for Cancer Research.)

Mature lymphoproliferative diseases are a heterogeneous group of neoplasms arising from different stages of B-cell and T-cell development. With improved understanding of the molecular processes in lymphoma and novel treatment options, arises a growing need for the molecular characterisation of tumours. Molecular imaging with single-photon-emission CT and PET using specific radionuclide tracers can provide whole-body information to investigate cancer biology, to evaluate phenotypic heterogeneity, to identify resistance to targeted therapy, and to assess the biodistribution of drugs in patients. In this Review, we evaluate the existing literature on molecular imaging in lymphoma, other than 18 F-fluordeoxyglucose molecular imaging. The aim is to examine the contribution of molecular imaging to the understanding of the biology of lymphoma and to discuss potential implications for the diagnostics and therapy of this disease. Finally, we discuss possible applications for molecular imaging of patients with lymphoma in the clinical context., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: Bispecific antibodies redirecting T cells to the tumor obtain increasing interest as potential cancer immunotherapy. ERY974, a full-length bispecific antibody targeting CD3ε on T cells and glypican 3 (GPC3) on tumors, has been in clinical development However, information on the influence of T cells on biodistribution of bispecific antibodies, like ERY974, is scarce. Here, we report the biodistribution and tumor targeting of zirconium-89 ( 89 Zr) labeled ERY974 in mouse models using immuno-positron emission tomography (PET) imaging., Methods: To study both the role of GPC3 and CD3 on the biodistribution of [ 89 Zr]Zr-N-suc-Df-ERY974, 89 Zr-labeled control antibodies targeting CD3 and non-mammalian protein keyhole limpet hemocyanin (KLH) or KLH only were used. GPC3 dependent tumor targeting of [ 89 Zr]Zr-N-suc-Df-ERY974 was tested in xenograft models with different levels of GPC3 expression. In addition, CD3 influence on biodistribution of [ 89 Zr]Zr-N-suc-Df-ERY974 was evaluated by comparing biodistribution between tumor-bearing immunodeficient mice and mice reconstituted with human immune cells using microPET imaging and ex vivo biodistribution. Ex vivo autoradiography was used to study deep tissue distribution., Results: In tumor-bearing immunodeficient mice, [ 89 Zr]Zr-N-suc-Df-ERY974 tumor uptake was GPC3 dependent and specific over [ 89 Zr]Zr-N-suc-Df-KLH/CD3 and [ 89 Zr]Zr-N-suc-Df-KLH/KLH. In mice engrafted with human immune cells, [ 89 Zr]Zr-N-suc-Df-ERY974 specific tumor uptake was higher than in immunodeficient mice. Ex vivo autoradiography demonstrated a preferential distribution of [ 89 Zr]Zr-N-suc-Df-ERY974 to T cell rich tumor tissue. Next to tumor, highest specific [ 89 Zr]Zr-N-suc-Df-ERY974 uptake was observed in spleen and lymph nodes., Conclusion: [89Zr] Zr-N-suc-Df-ERY974 can potentially be used to study ERY974 biodistribution in patients to support drug development., Competing Interests: Competing interests: TI, YS and NS are employees of Chugai Pharmaceutical and have ownership interest (including stocks and patents) in Chugai Pharmaceutical. A research grant to EDV was obtained from Chugai and made available to the institution., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Immune checkpoint inhibitors (ICIs) have substantially changed the field of oncology over the past few years. ICIs offer an alternative treatment strategy by exploiting the patients' immune system, resulting in a T cell mediated anti-tumor response. These therapies are effective in multiple different tumor types. Unfortunately, a substantial group of patients do not respond to ICIs. Molecular imaging, using single-photon emission computed tomography (SPECT) and positron emission tomography (PET), can provide non-invasive whole-body visualization of tumor and immune cell characteristics and might support patient selection or response evaluations for ICI therapies. In this review, recent studies with 18 F-fluorodeoxyglucose-PET imaging, imaging of immune checkpoints and imaging of immune cells will be discussed. These studies are until now mainly exploratory, but the first results suggest that molecular imaging biomarkers could have a role in the evaluation of ICI therapy., Competing Interests: Competing Interests: E.G.E. de Vries reports institutional financial support for her advisory role from Daiichi Sankyo, Merck, NSABP, Pfizer, Sanofi, Synthon and for clinical trials or contracted research from Amgen, AstraZeneca, Bayer, Chugai Pharma, CytomX Therapeutics, G1 Therapeutics, Genentech, Nordic Nanovector, Radius Health, Roche, Synthon. S.F. Oosting reports institutional financial support for clinical trials or contracted research from Celldex, Pfizer, Novartis, Bristol Myers Squibb, Kura Oncology, MedImmune, Roche, Merck Sharp & Dohme. A.J. van der Wekken reports institutional financial support for his advisory role from Pfizer, Boehringer-Ingelheim, Roche (diagnostics), Astra Zeneca and institutional financial support for clinical trials from AstraZeneca. All remaining authors have declared no conflicts of interest., (© The author(s).)

Bispecific antibodies (bsAbs) are antibodies that bind two distinct epitopes to cancer.. For use in oncology, one bsAb has been approved and 57 bsAbs are in clinical trials, none of which has reached phase 3. These bsAbs show great variability in design and mechanism of action. The various designs are often linked to the mechanisms of actions. The majority of bsAbs engage immune cells to destroy tumor cells. However, some bsAbs are also used to deliver payloads to tumors or to block tumor signaling pathways. This review provides insight into the choice of construct for bsAbs, summarizes the clinical development of bsAbs in oncology and identifies subsequent challenges., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Molecular imaging of immune cells might be a potential tool for response prediction, treatment evaluation and patient selection in inflammatory diseases as well as oncology. Targeting interleukin-2 (IL2) receptors on activated T-cells using positron emission tomography (PET) with N-(4-[ 18 F]fluorobenzoyl)-interleukin-2 ([ 18 F]FB-IL2) could be such a strategy. This paper describes the challenging translation of the partly manual labeling of [ 18 F]FB-IL2 for preclinical studies into an automated procedure following Good Manufacturing Practices (GMP), resulting in a radiopharmaceutical suitable for clinical use., Methods: The preclinical synthesis of [ 18 F]FB-IL2 was the starting point for translation to a clinical production method. To overcome several challenges, major adaptations in the production process were executed. The final analytical methods and production method were validated and documented. All data with regards to the quality and safety of the final drug product were documented in an investigational medicinal product dossier., Results: Restrictions in the [ 18 F]FB-IL2 production were imposed by hardware configuration of the automated synthesis equipment and by use of disposable cassettes. Critical steps in the [ 18 F]FB-IL2 production comprised the purification method, stability of recombinant human IL2 and the final formulation. With the GMP compliant production method, [ 18 F]FB-IL2 could reliably be produced with consistent quality complying to all specifications., Conclusions: To enable the use of [ 18 F]FB-IL2 in clinical studies, a fully automated GMP compliant production process was developed. [ 18 F]FB-IL2 is now produced consistently for use in clinical studies.

Purpose: Biodistribution of bispecific antibodies in patients is largely unknown. We therefore performed a feasibility study in 9 patients with advanced gastrointestinal adenocarcinomas to explore AMG 211 biodistribution (also known as MEDI-565), an approximately 55 kDa bispecific T-cell engager (BiTE®) directed against carcinoembryonic antigen (CEA) on tumor cells and cluster of differentiation 3 (CD3) on T-cells., Experimental Design: 89 Zr-labeled AMG 211 as tracer was administered alone or with cold AMG 211, for PET imaging before and/or during AMG 211 treatment., Results: Before AMG 211 treatment, the optimal imaging dose was 200-μg 89 Zr-AMG 211 + 1,800-μg cold AMG 211. At 3 hours, the highest blood pool standardized uptake value (SUV) mean was 4.0, and tracer serum half-life was 3.3 hours. CD3-mediated uptake was clearly observed in CD3-rich lymphoid tissues including spleen and bone marrow (SUV mean 3.2 and 1.8, respectively), and the SUV mean decreased more slowly than in other healthy tissues. 89 Zr-AMG 211 remained intact in plasma and was excreted predominantly via the kidneys in degraded forms. Of 43 visible tumor lesions, 37 were PET quantifiable, with a SUV max of 4.0 [interquartile range (IQR) 2.7-4.4] at 3 hours using the optimal imaging dose. The tracer uptake differed between tumor lesions 5-fold within and 9-fold between patients. During AMG 211 treatment, tracer was present in the blood pool, whereas tumor lesions were not visualized, possibly reflecting target saturation., Conclusions: This first-in-human study shows high, specific 89 Zr-AMG 211 accumulation in CD3-rich lymphoid tissues, as well as a clear, inter- and intraindividual heterogeneous tumor uptake., (©2019 American Association for Cancer Research.)

Effective patient selection before or early during treatment is important to increasing the therapeutic benefits of anticancer treatments. This selection process is often predicated on biomarkers, predominantly biospecimen biomarkers derived from blood or tumour tissue; however, such biomarkers provide limited information about the true extent of disease or about the characteristics of different, potentially heterogeneous tumours present in an individual patient. Molecular imaging can also produce quantitative outputs; such imaging biomarkers can help to fill these knowledge gaps by providing complementary information on tumour characteristics, including heterogeneity and the microenvironment, as well as on pharmacokinetic parameters, drug-target engagement and responses to treatment. This integrative approach could therefore streamline biomarker and drug development, although a range of issues need to be overcome in order to enable a broader use of molecular imaging in clinical trials. In this Perspective article, we outline the multistage process of developing novel molecular imaging biomarkers. We discuss the challenges that have restricted the use of molecular imaging in clinical oncology research to date and outline future opportunities in this area.

Optical molecular imaging using fluorescently labeled monoclonal antibodies is of significant added value in guiding surgical or endoscopic procedures. However, development of tracers for clinical trials is complex, and implementation in the clinic is therefore slow. We present a roadmap for development and translation of monoclonal antibody tracers into a drug product compliant with current good manufacturing processes (cGMPs). Methods: The production process for cetuximab-800CW and trastuzumab-800CW was optimized with regard to dye-to-protein ratio and formulation buffer. Promising formulations were produced under cGMP conditions and advanced to a full-scale stability study. Tracers were analyzed for stability by size-exclusion high-pressure liquid chromatography, pH measurement, osmolality, visual inspection, and sterility, as required by the European Pharmacopeia and cGMP guidelines. Results: Seven formulations were investigated for cetuximab-800CW and 10 for trastuzumab-800CW. On the basis of the formulation study results, we chose 2 formulations per antibody for investigation during the full-scale stability study. These formulations all performed well, showing good compliance with the acceptance criteria set for each product. Conclusion: We designed a roadmap to standardize the development, formulation, and cGMP translation of molecular fluorescent tracers. Using our standardized approach, we developed 2 stable antibody-based tracers for clinical use. The proposed roadmap can be used to efficiently develop a cGMP-compliant formulation and improve the translation of newly developed optical tracers to first-in-human use., (© 2019 by the Society of Nuclear Medicine and Molecular Imaging.)

Programmed cell death protein-1/ligand-1 (PD-1/PD-L1) blockade is effective in a subset of patients with several tumor types, but predicting patient benefit using approved diagnostics is inexact, as some patients with PD-L1-negative tumors also show clinical benefit 1,2 . Moreover, all biopsy-based tests are subject to the errors and limitations of invasive tissue collection 3-11 . Preclinical studies of positron-emission tomography (PET) imaging with antibodies to PD-L1 suggested that this imaging method might be an approach to selecting patients 12,13 . Such a technique, however, requires substantial clinical development and validation. Here we present the initial results from a first-in-human study to assess the feasibility of imaging with zirconium-89-labeled atezolizumab (anti-PD-L1), including biodistribution, and secondly test its potential to predict response to PD-L1 blockade (ClinicalTrials.gov identifiers NCT02453984 and NCT02478099). We imaged 22 patients across three tumor types before the start of atezolizumab therapy. The PET signal, a function of tracer exposure and target expression, was high in lymphoid tissues and at sites of inflammation. In tumors, uptake was generally high but heterogeneous, varying within and among lesions, patients, and tumor types. Intriguingly, clinical responses in our patients were better correlated with pretreatment PET signal than with immunohistochemistry- or RNA-sequencing-based predictive biomarkers, encouraging further development of molecular PET imaging for assessment of PD-L1 status and clinical response prediction.

Background: Up-to-date information on human epidermal growth factor receptor 2 (HER2) status in breast cancer (BC) is important, as expression can vary during the course of the disease, necessitating anti-HER2 therapy adjustments. Repeat biopsies, however, are not always possible. In this feasibility trial we assessed whether 89 Zr-trastuzumab PET could support diagnostic understanding and aid clinical decision making, when HER2 status could not be determined by standard work up. Additionally, HER2 status on circulating tumour cells (CTCs) was assessed., Patients and Methods: 89 Zr-trastuzumab PET was performed in patients if disease HER2 status remained unclear after standard work up (bone scan, 18 F-FDG PET, CT and if feasible a biopsy). PET result and central pathologic revision of available tumour biopsies were reported to the referring physician. CTC HER2 status prior to PET was evaluated afterwards and therefore not reported. Diagnostic understanding and treatment decision questionnaires were completed by the referring physicians before, directly after and ≥ 3 months after 89 Zr-trastuzumab PET., Results: Twenty patients were enrolled: 8 with two primary cancers (HER2-positive and HER2-negative BC or BC and non-BC), 7 with metastases inaccessible for biopsy, 4 with prior HER2-positive and -negative metastases and 1 with primary BC with equivocal HER2 status. 89 Zr-trastuzumab PET was positive in 12 patients, negative in 7 and equivocal in 1 patient. In 15/20 patients, 89 Zr-trastuzumab PET supported treatment decision. The scan altered treatment of 8 patients, increased physicians' confidence without affecting treatment in 10, and improved physicians' disease understanding in 18 patients. In 10/20 patients CTCs were detected; 6/10 showed HER2 expression. CTC HER2 status was not correlated to 89 Zr-trastuzumab PET result or treatment decision., Conclusion: 89 Zr-trastuzumab PET supports clinical decision making when HER2 status cannot be determined by standard work up. The impact of CTC HER2 status needs to be further explored.

Cancer immunotherapy has led to impressive antitumor effects. However, not all patients respond to immunotherapy, serious toxicity can occur and combination therapy may be warranted. Strategies for rational early treatment choices are urgently required. In the absence of ideal accompanying biomarkers it remains challenging to capture the dynamic, heterogeneous and complex tumor behavior. Tumor immune response involves next to tumor cells, numerous other cells and molecules in the tumor microenvironment. We review research to identify potential novel imaging biomarkers by non-invasive whole body molecular imaging with positron emission tomography and single-photon emission computed tomography for cancer immunotherapy. Firstly, imaging with radiolabeled immune checkpoint targeting molecules. Secondly, imaging of immune cells with ex vivo or in vivo radiolabeled tracers and thirdly, imaging extracellular matrix components, including adhesion molecules, growth factors and cytokines. These molecular imaging strategies - used alone, in combination or serially - could potentially contribute to patient selection upfront or early during immunotherapy., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Purpose: AMG 211, a bispecific T-cell engager (BiTE) antibody construct, targets carcinoembryonic antigen (CEA) and the CD3 epsilon subunit of the human T-cell receptor. AMG 211 was labeled with zirconium-89 ( 89 Zr) or fluorescent dye to evaluate the tumor-targeting properties. Experimental Design: 89 Zr-AMG211 was administered to mice bearing CEA-positive xenograft tumors of LS174T colorectal adenocarcinoma or BT474 breast cancer cells, as well as CEA-negative HL-60 promyelocytic leukemia xenografts. Biodistribution studies with 2- to 10-μg 89 Zr-AMG211 supplemented with unlabeled AMG 211 up to 500-μg protein dose were performed. A BiTE that does not bind CEA, 89 Zr-Mec14, served as a negative control. 89 Zr-AMG211 integrity was determined in tumor lysates ex vivo Intratumoral distribution was studied with IRDye800CW-AMG211. Moreover, 89 Zr-AMG211 was manufactured according to Good Manufacturing Practice (GMP) guidelines for clinical trial NCT02760199 Results: 89 Zr-AMG211 demonstrated dose-dependent tumor uptake at 6 hours. The highest tumor uptake was observed with a 2-μg dose, and the lowest tumor uptake was observed with a 500-μg dose. After 24 hours, higher uptake of 10-μg 89 Zr-AMG211 occurred in CEA-positive xenografts, compared with CEA-negative xenografts. Although the blood half-life of 89 Zr-AMG211 was approximately 1 hour, tumor retention persisted for at least 24 hours. 89 Zr-Mec14 showed no tumor accumulation beyond background level. Ex vivo autoradiography revealed time-dependent disintegration of 89 Zr-AMG211. 800CW-AMG211 was specifically localized in CEA-expressing viable tumor tissue. GMP-manufactured 89 Zr-AMG211 fulfilled release specifications. Conclusions: 89 Zr-AMG211 showed dose-dependent CEA-specific tumor targeting and localization in viable tumor tissue. Our data enabled its use to clinically evaluate AMG 211 in vivo behavior. Clin Cancer Res; 24(20); 4988-96. ©2018 AACR ., (©2018 American Association for Cancer Research.)

Newly developed protein drugs that target tumor-associated antigens are often modified in order to increase their therapeutic effect, tumor exposure, and safety profile. During the development of protein drugs, molecular imaging is increasingly used to provide additional information on their in vivo behavior. As a result, there are increasing numbers of studies that demonstrate the effect of protein modification on whole body distribution and tumor uptake of protein drugs. However, much still remains unclear about how to interpret obtained biodistribution data correctly. Consequently, there is a need for more insight in the correct way of interpreting preclinical and clinical imaging data. Summarizing the knowledge gained to date may facilitate this interpretation. This review therefore provides an overview of specific protein properties and modifications that can affect biodistribution and tumor uptake of anticancer antibodies, antibody fragments, and nonimmunoglobulin scaffolds. Protein properties that are discussed in this review are molecular size, target interaction, FcRn binding, and charge. Protein modifications that are discussed are radiolabeling, fluorescent labeling drug conjugation, glycosylation, humanization, albumin binding, and polyethylene glycolation., (© 2018 Wiley Periodicals, Inc.)

Rationale: Knowledge on monoclonal antibody biodistribution in healthy tissues in humans can support clinical drug development. Molecular imaging with positron emission tomography (PET) can yield information in this setting. However, recent imaging studies have analyzed the behavior of single antibodies only, neglecting comparison across different antibodies. Methods: We compared the distribution of four 89 Zr-labeled antibodies in healthy tissue in a retrospective analysis based on the recently published harmonization protocol for 89 Zr-tracers and our delineation protocol. Results: The biodistribution patterns of 89 Zr-lumretuzumab, 89 Zr-MMOT0530A, 89 Zr-bevacizumab and 89 Zr-trastuzumab on day 4 after tracer injection were largely similar. The highest tracer concentration was seen in healthy liver, spleen, kidney and intestines. About one-third of the injected tracer dose was found in the circulation, up to 15% in the liver and only 4% in the spleen and kidney. Lower tracer concentration was seen in bone marrow, lung, compact bone, muscle, fat and the brain. Despite low tracer accumulation per gram of tissue, large-volume tissues, especially fat, can influence overall distribution: On average, 5-7% of the injected tracer dose accumulated in fat, with a peak of 19% in a patient with morbid obesity. Conclusion: The similar biodistribution of the four antibodies is probably based on their similar molecular structure, binding characteristics and similar metabolic pathways. These data provide a basis for a prospectively growing, online accessible warehouse of molecular imaging data, which enables researchers to increase and exchange knowledge on whole body drug distribution and potentially supports drug development decisions., Competing Interests: Competing Interests: The UMCG received grants form Roche and Genentech for conduct of the imaging trials. All other authors declare no competing interests.

Development of new oncology drugs has increased since the improved understanding of cancer's complex biology. The oncology field has become the top therapeutic research area for new drugs. However, only a limited number of drugs entering clinical trials will be approved for use as the standard of care for cancer patients. Molecular imaging is increasingly perceived as a tool to support go/no-go decisions early during drug development. It encompasses a wide range of techniques that include radiolabeling a compound of interest followed by visualization with SPECT or PET. Radiolabeling can be performed using a variety of radionuclides, which are preferably matched to the compound on the basis of size and half-life. Imaging can provide information on drug behavior in vivo, whole-body drug target visualization, and heterogeneity in drug target expression. This review focuses on current applications of molecular imaging in the development of small molecules, antibodies, and antihormonal anticancer drugs., (© 2018 by the Society of Nuclear Medicine and Molecular Imaging.)

Treatment of human epidermal growth factor receptor 2 (HER2)-driven breast cancer with tyrosine kinase inhibitor lapatinib can induce a compensatory HER3 increase, which may attenuate antitumor efficacy. Therefore, we explored in vivo HER3 tumor status assessment after lapatinib treatment with zirconium-89 ( 89 Zr)-labeled anti-HER3 antibody mAb3481 positron emission tomography (PET). Lapatinib effects on HER3 cell surface expression and mAb3481 internalization were evaluated in human breast (BT474, SKBR3) and gastric (N87) cancer cell lines using flow cytometry. Next, in vivo effects of daily lapatinib treatment on 89 Zr-mAb3481 BT474 and N87 xenograft tumor uptake were studied. PET-scans (BT474 only) were made after daily lapatinib treatment for 9 days, starting 3 days prior to 89 Zr-mAb3481 administration. Subsequently, ex vivo 89 Zr-mAb3481 organ distribution analysis was performed and HER3 tumor levels were measured with Western blot and immunohistochemistry. In vitro, lapatinib increased membranous HER3 in BT474, SKBR3 and N87 cells, and consequently mAb3481 internalization 1.7-fold (BT474), 1.4-fold (SKBR3) and 1.4-fold (N87). 89 Zr-mAb3481 BT474 tumor uptake was remarkably high at SUV mean 5.6±0.6 (51.8±7.7%ID/g) using a 10 μg 89 Zr-mAb3481 protein dose in vehicle-treated mice. However, compared to vehicle, lapatinib did not affect 89 Zr-mAb3481 ex vivo uptake in BT474 and N87 tumors, while HER3 tumor expression remained unchanged. In conclusion, lapatinib increased in vitro HER3 tumor cell expression, but not when these cells were xenografted. 89 Zr-mAb3481 PET accurately reflected HER3 tumor status. 89 Zr-mAb3481 PET showed high, HER3-specific tumor uptake, and such an approach might sensitively assess HER3 tumor heterogeneity and treatment response in patients.

Purpose: We evaluated biodistribution and tumor targeting of 89 Zr-lumretuzumab before and during treatment with lumretuzumab, a human epidermal growth factor receptor 3 (HER3)-targeting monoclonal antibody. Experimental Design: Twenty patients with histologically confirmed HER3-expressing tumors received 89 Zr-lumretuzumab and underwent positron emission tomography (PET). In part A, 89 Zr-lumretuzumab was given with additional, escalating doses of unlabeled lumretuzumab, and scans were performed 2, 4, and 7 days after injection to determine optimal imaging conditions. In part B, patients were scanned following tracer injection before (baseline) and after a pharmacodynamic (PD)-active lumretuzumab dose for saturation analysis. HER3 expression was determined immunohistochemically in skin biopsies. Tracer uptake was calculated as standardized uptake value (SUV). Results: Optimal PET conditions were found to be 4 and 7 days after administration of 89 Zr-lumretuzumab with 100-mg unlabeled lumretuzumab. At baseline using 100-mg unlabeled lumretuzumab, the tumor SUVmax was 3.4 (±1.9) at 4 days after injection. SUVmean values for normal blood, liver, lung, and brain tissues were 4.9, 6.4, 0.9 and 0.2, respectively. Saturation analysis ( n = 7) showed that 4 days after lumretuzumab administration, tumor uptake decreased by 11.9% (±8.2), 10.0% (±16.5), and 24.6% (±20.9) at PD-active doses of 400, 800, and 1,600 mg, respectively, when compared with baseline. Membranous HER3 was completely downregulated in paired skin biopsies already at and above 400-mg lumretuzumab. Conclusions: PET imaging showed biodistribution and tumor-specific 89 Zr-lumretuzumab uptake. Although, PD-active lumretuzumab doses decreased 89 Zr-lumretuzumab uptake, there was no clear evidence of tumor saturation by PET imaging as the tumor SUV did not plateau with increasing doses. Clin Cancer Res; 23(20); 6128-37. ©2017 AACR ., (©2017 American Association for Cancer Research.)

In theranostics, radiolabeled compounds are used to determine a treatment strategy by combining therapeutics and diagnostics in the same agent. Monoclonal antibodies (mAbs) and antibody-related therapeutics represent a rapidly expanding group of cancer medicines. Theranostic approaches using these drugs in oncology are particularly interesting because antibodies are designed against specific targets on the tumor cell membrane and immune cells as well as targets in the tumor microenvironment. In addition, these drugs are relatively easy to radiolabel. Noninvasive molecular imaging techniques, such as SPECT and PET, provide information on the whole-body distribution of radiolabeled mAbs and antibody-related therapeutics. Molecular antibody imaging can potentially elucidate drug target expression, tracer uptake in the tumor, tumor saturation, and heterogeneity for these parameters within the tumor. These data can support drug development and may aid in patient stratification and monitoring of the treatment response. Selecting a radionuclide for theranostic purposes generally starts by matching the serum half-life of the mAb or antibody-related therapeutic and the physical half-life of the radionuclide. Furthermore, PET imaging allows better quantification than the SPECT technique. This information has increased interest in theranostics using PET radionuclides with a relatively long physical half-life, such as 89 Zr. In this review, we provide an overview of ongoing research on mAbs and antibody-related theranostics in preclinical and clinical oncologic settings. We identified 24 antibodies or antibody-related therapeutics labeled with PET radionuclides for theranostic purposes in patients. For this approach to become integrated in standard care, further standardization with respect to the procedures involved is required., (© 2017 by the Society of Nuclear Medicine and Molecular Imaging.)

The human epidermal growth factor receptor 3 (HER3) is an interesting target for antitumor therapy. For optimal HER3 signaling inhibition, a biparatopic Nanobody construct (MSB0010853) was developed that binds 2 different HER3 epitopes. In addition, MSB0010853 contains a third HER3 epitope that binds albumin to extend its circulation time. MSB0010853 is cross-reactive with HER3 and albumin of mouse origin. We aimed to gain insight into MSB0010853 biodistribution and tumor uptake by radiolabeling the Nanobody construct with 89 Zr. Methods: MSB0010853 was radiolabeled with 89 Zr. Dose- and time-dependent tumor uptake was studied in nude BALB/c mice bearing a subcutaneous HER3 overexpressing H441 non-small cell lung cancer xenograft. Dose-dependent biodistribution of 89 Zr-MSB0010853 was assessed ex vivo at 24 h after intravenous injection. Protein doses of 5, 10, 25, 100, and 1,000 μg were used. Time-dependent biodistribution of MSB0010853 was analyzed ex vivo at 3, 6, 24, and 96 h after intravenous administration of 25 μg of 89 Zr-MSB0010853. PET imaging and biodistribution were performed 24 h after administration of 25 μg of 89 Zr-MSB0010853 to mice bearing human H441, FaDu (high HER3 expression), or Calu-1 (no HER3 expression) tumor xenografts. Results: Radiolabeling of MSB0010853 with 89 Zr was performed with a radiochemical purity of greater than 95%. Ex vivo biodistribution showed protein dose- and time-dependent distribution of 89 Zr-MSB0010853 in all organs. Uptake of 89 Zr-MSB0010853 in H441 tumors was only time-dependent. Tumor could be visualized up to at least 96 h after injection. The highest mean SUV of 0.6 ± 0.2 was observed at 24 h after injection of 25 μg of 89 Zr-MSB0010853. 89 Zr-MSB0010853 tumor uptake correlated with HER3 expression and was highest in H441 (6.2 ± 1.1 percentage injected dose per gram [%ID/g]) and lowest in Calu-1 (2.3 ± 0.3 %ID/g) xenografts. Conclusion: 89 Zr-MSB0010853 organ distribution and tumor uptake in mice are time-dependent, and tumor uptake correlates with HER3 expression. In contrast to tumor uptake except for kidney uptake, organ distribution of 89 Zr-MSB0010853 is protein dose-dependent for the tested doses. 89 Zr-MSB0010853 PET imaging gives insight into the in vivo behavior of MSB0010853., (© 2017 by the Society of Nuclear Medicine and Molecular Imaging.)

Purpose: c-MET and its ligand hepatocyte growth factor are often dysregulated in human cancers. Dynamic changes in c-MET expression occur and might predict drug efficacy or emergence of resistance. Noninvasive visualization of c-MET dynamics could therefore potentially guide c-MET-directed therapies. We investigated the feasibility of 89 Zr-labelled one-armed c-MET antibody onartuzumab PET for detecting relevant changes in c-MET levels induced by c-MET-mediated epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor erlotinib resistance or heat shock protein-90 (HSP90) inhibitor NVP-AUY-922 treatment in human non-small-cell lung cancer (NSCLC) xenografts., Methods: In vitro membrane c-MET levels were determined by flow cytometry. HCC827ErlRes, an erlotinib-resistant clone with c-MET upregulation, was generated from the exon-19 EGFR-mutant human NSCLC cell line HCC827. Mice bearing HCC827 and HCC827ErlRes tumours in opposite flanks underwent 89 Zr-onartuzumab PET scans. The HCC827-xenografted mice underwent 89 Zr-onartuzumab PET scans before treatment and while receiving biweekly intraperitoneal injections of 100 mg/kg NVP-AUY-922 or vehicle. Ex vivo, tumour c-MET immunohistochemistry was correlated with the imaging results., Results: In vitro, membrane c-MET was upregulated in HCC827ErlRes tumours by 213 ± 44% in relation to the level in HCC827 tumours, while c-MET was downregulated by 69 ± 9% in HCC827 tumours following treatment with NVP-AUY-922. In vivo, 89 Zr-onartuzumab uptake was 26% higher (P < 0.05) in erlotinib-resistant HCC827ErlRes than in HCC827 xenografts, while HCC827 tumour uptake was 33% lower (P < 0.001) following NVP-AUY-922 treatment., Conclusion: The results show that 89 Zr-onartuzumab PET effectively discriminates relevant changes in c-MET levels and could potentially be used clinically to monitor c-MET status.

Purpose: To provide proof of principle of safety, breast tumor-specific uptake, and positive tumor margin assessment of the systemically administered near-infrared fluorescent tracer bevacizumab-IRDye800CW targeting VEGF-A in patients with breast cancer. Experimental Design: Twenty patients with primary invasive breast cancer eligible for primary surgery received 4.5 mg bevacizumab-IRDye800CW as intravenous bolus injection. Safety aspects were assessed as well as tracer uptake and tumor delineation during surgery and ex vivo in surgical specimens using an optical imaging system. Ex vivo multiplexed histopathology analyses were performed for evaluation of biodistribution of tracer uptake and coregistration of tumor tissue and healthy tissue. Results: None of the patients experienced adverse events. Tracer levels in primary tumor tissue were higher compared with those in the tumor margin ( P < 0.05) and healthy tissue ( P < 0.0001). VEGF-A tumor levels also correlated with tracer levels ( r = 0.63, P < 0.0002). All but one tumor showed specific tracer uptake. Two of 20 surgically excised lumps contained microscopic positive margins detected ex vivo by fluorescent macro- and microscopy and confirmed at the cellular level. Conclusions: Our study shows that systemic administration of the bevacizumab-IRDye800CW tracer is safe for breast cancer guidance and confirms tumor and tumor margin uptake as evaluated by a systematic validation methodology. The findings are a step toward a phase II dose-finding study aimed at in vivo margin assessment and point to a novel drug assessment tool that provides a detailed picture of drug distribution in the tumor tissue. Clin Cancer Res; 23(11); 2730-41. ©2016 AACR ., (©2016 American Association for Cancer Research.)