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Non-invasive PET imaging of liver fibrogenesis using a RESCA-conjugated Affibody molecule. iScience 2024; 27:109688. [PMID: 38660405 PMCID: PMC11039342 DOI: 10.1016/j.isci.2024.109688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2023] [Revised: 02/02/2024] [Accepted: 04/05/2024] [Indexed: 04/26/2024] Open
Abstract
Non-invasive assessment of fibrogenic activity, rather than fibrotic scars, could significantly improve the management of fibrotic diseases and the development of anti-fibrotic drugs. This study explores the potential of an Affibody molecule (Z09591) labeled with the Al(18)F-restrained complexing agent (RESCA) method as a tracer for the non-invasive detection of fibrogenic cells. Z09591 was functionalized with the RESCA chelator for direct labeling with [18F]AlF. In vivo positron emission tomography/magnetic resonance imaging scans on U-87 tumor-bearing mice exhibited high selectivity of the resulting radiotracer, [18F]AlF-RESCA-Z09591, for platelet-derived growth factor receptor β (PDGFRβ), with minimal non-specific background uptake. Evaluation in a mouse model with carbon tetrachloride-induced fibrotic liver followed by a disease regression phase, revealed the radiotracer's high affinity and specificity for fibrogenic cells in fibrotic livers (standardized uptake value [SUV] 0.43 ± 0.05), with uptake decreasing during recovery (SUV 0.29 ± 0.03) (p < 0.0001). [18F]AlF-RESCA-Z09591 accurately detects PDGFRβ, offering non-invasive assessment of fibrogenic cells and promising applications in precise liver fibrogenesis diagnosis, potentially contributing significantly to anti-fibrotic drug development.
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Noninvasive PET Detection of CD69-Positive Immune Cells Before Signs of Clinical Disease in Inflammatory Arthritis. J Nucl Med 2024; 65:294-299. [PMID: 38050119 DOI: 10.2967/jnumed.123.266336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 10/10/2023] [Indexed: 12/06/2023] Open
Abstract
Rheumatoid arthritis (RA) is the most common inflammatory joint disease, and early diagnosis is key for effective disease management. CD69 is one of the earliest cell surface markers seen at the surface of activated immune cells, and CD69 is upregulated in synovial tissue in patients with active RA. In this study, we evaluated the performance of a CD69-targeting PET agent, [68Ga]Ga-DOTA-ZCAM241, for early disease detection in a model of inflammatory arthritis. Methods: A model of inflammatory arthritis was induced by transferring splenocytes from KRN T-cell receptor transgenic B6 mice into T-cell-deficient I-Ag7 major histocompatibility complex class II-expressing recipient mice. The mice were examined longitudinally by [68Ga]Ga-DOTA-ZCAM241 PET/CT before and 3, 7, and 12 d after induction of arthritis. Disease progression was monitored by clinical parameters, including measuring body weight and scoring the swelling of the paws. The uptake of [68Ga]Ga-DOTA-ZCAM241 in the paws was analyzed and expressed as SUVmean Tissue biopsy samples were analyzed for CD69 expression by flow cytometry or immunostaining for a histologic correlate. A second group of mice was examined by a nonbinding, size-matched Affibody molecule as the control. Results: Clinical symptoms appeared 5-7 d after induction of arthritis. The uptake of [68Ga]Ga-DOTA-ZCAM241 in the joints was negligible at baseline but increased gradually after disease induction. An elevated PET signal was found on day 3, before the appearance of clinical symptoms. The uptake of [68Ga]Ga-DOTA-ZCAM241 correlated with the clinical score and disease severity. The presence of CD69-positive cells in the joints and lymph nodes was confirmed by flow cytometry and immunostaining. The uptake of the nonbinding tracer that was the negative control also increased gradually with disease progression, although to a lesser extent than with [68Ga]Ga-DOTA-ZCAM241 Conclusion: The uptake of [68Ga]Ga-DOTA-ZCAM241 in the inflamed joints preceded the clinical symptoms in the KRN T-cell transfer model of inflammatory arthritis, in accordance with immunostaining for CD69. [68Ga]Ga-DOTA-ZCAM241 is thus a promising PET imaging marker of activated immune cells in tissue during RA onset.
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Imaging of fibrogenesis in the liver by [ 18F]TZ-Z09591, an Affibody molecule targeting platelet derived growth factor receptor β. EJNMMI Radiopharm Chem 2023; 8:23. [PMID: 37733133 PMCID: PMC10513984 DOI: 10.1186/s41181-023-00210-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 09/04/2023] [Indexed: 09/22/2023] Open
Abstract
BACKGROUND Platelet-derived growth factor receptor beta (PDGFRβ) is a receptor overexpressed on activated hepatic stellate cells (aHSCs). Positron emission tomography (PET) imaging of PDGFRβ could potentially allow the quantification of fibrogenesis in fibrotic livers. This study aims to evaluate a fluorine-18 radiolabeled Affibody molecule ([18F]TZ-Z09591) as a PET tracer for imaging liver fibrogenesis. RESULTS In vitro specificity studies demonstrated that the trans-Cyclooctenes (TCO) conjugated Z09591 Affibody molecule had a picomolar affinity for human PDGFRβ. Biodistribution performed on healthy rats showed rapid clearance of [18F]TZ-Z09591 through the kidneys and low liver background uptake. Autoradiography (ARG) studies on fibrotic livers from mice or humans correlated with histopathology results. Ex vivo biodistribution and ARG revealed that [18F]TZ-Z09591 binding in the liver was increased in fibrotic livers (p = 0.02) and corresponded to binding in fibrotic scars. CONCLUSIONS Our study highlights [18F]TZ-Z09591 as a specific tracer for fibrogenic cells in the fibrotic liver, thus offering the potential to assess fibrogenesis clearly.
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Comparative in vivo biodistribution and dosimetry in non-human primate of the fibroblast activation protein radiotracers [68Ga]Ga-FAPI-04, [68Ga]Ga-FAPI-46 and [18F]FAPI-74. Nucl Med Biol 2022. [DOI: 10.1016/s0969-8051(22)00443-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Radiolabeled GRPR Antagonists for Imaging of Disseminated Prostate Cancer - Influence of Labeling Chemistry on Targeting Properties. Curr Med Chem 2021; 27:7090-7111. [PMID: 32164503 DOI: 10.2174/0929867327666200312114902] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 12/31/2019] [Accepted: 01/10/2020] [Indexed: 12/13/2022]
Abstract
BACKGROUND Radionuclide molecular imaging of Gastrin-Releasing Peptide Receptor (GRPR) expression promises unparalleled opportunities for visualizing subtle prostate tumors, which due to small size, adjacent benign tissue, or a challenging location would otherwise remain undetected by conventional imaging. Achieving high imaging contrast is essential for this purpose and the molecular design of any probe for molecular imaging of prostate cancer should be aimed at obtaining as high tumor-to-organ ratios as possible. OBJECTIVE This short review summarizes the key imaging modalities currently used in prostate cancer, with a special focus on radionuclide molecular imaging. Emphasis is laid mainly on the issue of radiometals labeling chemistry and its influence on the targeting properties and biodistribution of radiolabeled GRPR antagonists for imaging of disseminated prostate cancer. METHODS A comprehensive literature search of the PubMed/MEDLINE, and Scopus library databases was conducted to find relevant articles. RESULTS The combination of radionuclide, chelator and required labeling chemistry was shown to have a significant influence on the stability, binding affinity and internalization rate, off-target interaction with normal tissues and blood proteins, interaction with enzymes, activity uptake and retention in excretory organs and activity uptake in tumors of radiolabeled bombesin antagonistic analogues. CONCLUSION Labeling chemistry has a very strong impact on the biodistribution profile of GRPRtargeting peptide based imaging probes and needs to be considered when designing a targeting probe for high contrast molecular imaging. Taking into account the complexity of in vivo interactions, it is not currently possible to accurately predict the optimal labeling approach. Therefore, a detailed in vivo characterization and optimization is essential for the rational design of imaging agents.
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Benefit of Later-Time-Point PET Imaging of HER3 Expression Using Optimized Radiocobalt-Labeled Affibody Molecules. Int J Mol Sci 2020; 21:ijms21061972. [PMID: 32183096 PMCID: PMC7139902 DOI: 10.3390/ijms21061972] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 03/09/2020] [Accepted: 03/11/2020] [Indexed: 02/07/2023] Open
Abstract
HER3-binding affibody molecules are a promising format for visualization of HER3 expression. Cobalt-55, a positron-emitting isotope, with a half-life of 17.5 h, allows for next-day imaging. We investigated the influence of the charge of the radiocobalt–chelator complex on the biodistribution of anti-HER3 affibody molecule (HE)3-ZHER3 and compared the best radiocobalt-labeled variant with a recently optimized gallium-labeled variant. Affibody conjugates (HE)3-ZHER3-X (X = NOTA, NODAGA, DOTA, DOTAGA) were labeled with [57Co]Co (surrogate for 55Co). Affinity measurements, binding specificity and cellular processing were studied in two HER3-expressing cancer cell lines. Biodistribution was studied 3 and 24 h post-injection (pi) in mice with HER3-expressing BxPC-3 xenografts and compared to [68Ga]Ga-(HE)3-ZHER3-NODAGA. Micro-single-photon emission tomography/computed tomography (microSPECT/CT) and micro-positron emission tomography/computed tomography (microPET/CT) imaging was performed 3 and 24 h pi. Stably labeled conjugates bound to HER3 with subnanomolar affinity. [57Co]Co-(HE)3-ZHER3-DOTA had the best tumor retention and a significantly lower concentration in blood than other conjugates, leading to superior tumor-to-blood and tumor-to-liver ratios 24 h pi. Compared to [68Ga]Ga-(HE)3-ZHER3-NODAGA 3 h pi, [57Co]Co-(HE)3-ZHER3-DOTA provided superior imaging contrast in liver 24 h pi. Concluding, the composition and charge of the [57Co]Co–chelator complex influenced the uptake in tumors and normal tissue. [57Co]Co-(HE)3-ZHER3-DOTA provided the best imaging properties among the cobalt-labeled conjugates. Delayed imaging of HER3 expression with [57Co]Co-(HE)3-ZHER3-DOTA improved imaging contrast compared to early-time-point imaging with [68Ga]Ga-(HE)3-ZHER3-NODAGA.
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Comparative evaluation of affibody- and antibody fragments-based CAIX imaging probes in mice bearing renal cell carcinoma xenografts. Sci Rep 2019; 9:14907. [PMID: 31624303 PMCID: PMC6797765 DOI: 10.1038/s41598-019-51445-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 09/25/2019] [Indexed: 12/11/2022] Open
Abstract
Carbonic anhydrase IX (CAIX) is a cancer-associated molecular target for several classes of therapeutics. CAIX is overexpressed in a large fraction of renal cell carcinomas (RCC). Radionuclide molecular imaging of CAIX-expression might offer a non-invasive methodology for stratification of patients with disseminated RCC for CAIX-targeting therapeutics. Radiolabeled monoclonal antibodies and their fragments are actively investigated for imaging of CAIX expression. Promising alternatives are small non-immunoglobulin scaffold proteins, such as affibody molecules. A CAIX-targeting affibody ZCAIX:2 was re-designed with the aim to decrease off-target interactions and increase imaging contrast. The new tracer, DOTA-HE3-ZCAIX:2, was labeled with 111In and characterized in vitro. Tumor-targeting properties of [111In]In-DOTA-HE3-ZCAIX:2 were compared head-to-head with properties of the parental variant, [99mTc]Tc(CO)3-HE3-ZCAIX:2, and the most promising antibody fragment-based tracer, [111In]In-DTPA-G250(Fab’)2, in the same batch of nude mice bearing CAIX-expressing RCC xenografts. Compared to the 99mTc-labeled parental variant, [111In]In-DOTA-HE3-ZCAIX:2 provides significantly higher tumor-to-lung, tumor-to-bone and tumor-to-liver ratios, which is essential for imaging of CAIX expression in the major metastatic sites of RCC. [111In]In-DOTA-HE3-ZCAIX:2 offers significantly higher tumor-to-organ ratios compared with [111In]In-G250(Fab’)2. In conclusion, [111In]In-DOTA-HE3-ZCAIX:2 can be considered as a highly promising tracer for imaging of CAIX expression in RCC metastases based on our results and literature data.
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Evaluation of Tumor-Targeting Properties of an Antagonistic Bombesin Analogue RM26 Conjugated with a Non-Residualizing Radioiodine Label Comparison with a Radiometal-Labelled Counterpart. Pharmaceutics 2019; 11:pharmaceutics11080380. [PMID: 31382362 PMCID: PMC6724035 DOI: 10.3390/pharmaceutics11080380] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 07/16/2019] [Accepted: 07/24/2019] [Indexed: 12/24/2022] Open
Abstract
Radiolabelled antagonistic bombesin analogues are successfully used for targeting of gastrin-releasing peptide receptors (GRPR) that are overexpressed in prostate cancer. Internalization of antagonistic bombesin analogues is slow. We hypothesized that the use of a non-residualizing radioiodine label might not affect the tumour uptake but would reduce the retention in normal organs, where radiopharmaceutical would be internalized. To test this hypothesis, tyrosine was conjugated via diethylene glycol linker to N-terminus of an antagonistic bombesin analogue RM26 to form Tyr-PEG2-RM26. [111In]In-DOTA-PEG2-RM26 was used as a control with a residualizing label. Tyr-PEG2-RM26 was labelled with 125I with 95% radiochemical purity and retained binding specificity to GRPR. The IC50 values for Tyr-PEG2-RM26 and DOTA-PEG2-RM26 were 1.7 ± 0.3 nM and 3.3 ± 0.5 nM, respectively. The cellular processing of [125I]I-Tyr-PEG2-RM26 by PC-3 cells showed unusually fast internalization. Biodistribution showed that uptake in pancreas and tumour was GRPR-specific for both radioconjugates. Blood clearance of [125I]I-Tyr-PEG2-RM26 was appreciably slower and activity accumulation in all organs was significantly higher than for [111In]In-DOTA-PEG2-RM26. Tumor uptake of [111In]In-DOTA-PEG2-RM26 was significantly higher than for [125I]I-Tyr-PEG2-RM26, resulting in higher tumour-to-organ ratio for [111In]In-DOTA-PEG2-RM26 at studied time points. Incorporation of amino acids with hydrophilic side-chains next to tyrosine might overcome the problems associated with the use of tyrosine as a prosthetic group for radioiodination.
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Synthesis and Preclinical Evaluation of Radio-Iodinated GRPR/PSMA Bispecific Heterodimers for the Theranostics Application in Prostate Cancer. Pharmaceutics 2019; 11:E358. [PMID: 31340483 PMCID: PMC6680768 DOI: 10.3390/pharmaceutics11070358] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 07/16/2019] [Accepted: 07/20/2019] [Indexed: 12/21/2022] Open
Abstract
Gastrin-releasing peptide receptor (GRPR) and prostate-specific membrane antigen (PSMA) are overexpressed in most prostate cancers. GRPR expression is higher in early stages while PSMA expression increases with progression. The possibility of targeting both markers with a single theranostics radiotracer could improve patient management. Three GRPR/PSMA-targeting bispecific heterodimers (urea derivative PSMA-617 and bombesin-based antagonist RM26 linked via X-triazolyl-Tyr-PEG2, X = PEG2 (BO530), (CH2)8 (BO535), none (BO536)) were synthesized by solid-phase peptide synthesis. Peptides were radio-iodinated and evaluated in vitro for binding specificity, cellular retention, and affinity. In vivo specificity for all heterodimers was studied in PC-3 (GRPR-positive) and LNCaP (PSMA-positive) xenografts. [125I]I-BO530 was evaluated in PC-3pip (GRPR/PSMA-positive) xenografts. Micro single-photon emission computed tomography/computed tomography (microSPECT/CT) scans were acquired. The heterodimers were radiolabeled with high radiochemical yields, bound specifically to both targets, and demonstrated high degree of activity retention in PC-3pip cells. Only [125I]I-BO530 demonstrated in vivo specificity to both targets. A biodistribution study of [125I]I-BO530 in PC-3pip xenografted mice showed high tumor activity uptake (30%-35%ID/g at 3 h post injection (pi)). Activity uptake in tumors was stable and exceeded all other organs 24 h pi. Activity uptake decreased only two-fold 72 h pi. The GRPR/PSMA-targeting heterodimer [125I]I-BO530 is a promising agent for theranostics application in prostate cancer.
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Trastuzumab co-treatment improves survival of mice with PC-3 prostate cancer xenografts treated with [177Lu]Lu-DOTAGA-PEG2-RM26 GRPR antagonists. Nucl Med Biol 2019. [DOI: 10.1016/s0969-8051(19)30248-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Trastuzumab cotreatment improves survival of mice with PC-3 prostate cancer xenografts treated with the GRPR antagonist 177 Lu-DOTAGA-PEG 2 -RM26. Int J Cancer 2019; 145:3347-3358. [PMID: 31077356 PMCID: PMC6852655 DOI: 10.1002/ijc.32401] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Revised: 04/19/2019] [Accepted: 05/02/2019] [Indexed: 12/24/2022]
Abstract
Gastrin‐releasing peptide receptors (GRPRs) are overexpressed in prostate cancer and are suitable for targeted radionuclide therapy (TRT). We optimized the bombesin‐derived GRPR‐antagonist PEG2‐RM26 for labeling with 177Lu and further determined the effect of treatment with 177Lu‐labeled peptide alone or in combination with the anti‐HER2 antibody trastuzumab in a murine model. The PEG2‐RM26 analog was coupled to NOTA, NODAGA, DOTA and DOTAGA chelators. The peptide‐chelator conjugates were labeled with 177Lu and characterized in vitro and in vivo. A preclinical therapeutic study was performed in PC‐3 xenografted mice. Mice were treated with intravenous injections (6 cycles) of (A) PBS, (B) DOTAGA‐PEG2‐RM26, (C) 177Lu‐DOTAGA‐PEG2‐RM26, (D) trastuzumab or (E) 177Lu‐DOTAGA‐PEG2‐RM26 in combination with trastuzumab. 177Lu‐DOTAGA‐PEG2‐RM26 demonstrated quantitative labeling yield at high molar activity (450 GBq/μmol), high in vivo stability (5 min pi >98% of radioligand remained when coinjected with phosphoramidon), high affinity to GRPR (KD = 0.4 ± 0.2 nM), and favorable biodistribution (1 hr pi tumor uptake was higher than in healthy tissues, including the kidneys). Therapy with 177Lu‐DOTAGA‐PEG2‐RM26 induced a significant inhibition of tumor growth. The median survival for control groups was significantly shorter than for treated groups (Group C 66 days, Group E 74 days). Trastuzumab together with radionuclide therapy significantly improved survival. No treatment‐related toxicity was observed. In conclusion, based on in vitro and in vivo characterization of the four 177Lu‐labeled PEG2‐RM26 analogs, we concluded that 177Lu‐DOTAGA‐PEG2‐RM26 was the most promising analog for TRT. Radiotherapy using 177Lu‐DOTAGA‐PEG2‐RM26 effectively inhibited tumor growth in vivo in a murine prostate cancer model. Anti‐HER2 therapy additionally improved survival. What's new? Targeted radionuclide therapy (TRT) using radiolabeled peptides seeking gastrin‐releasing peptide receptors (GRPRs) in tumors is a promising approach to treat disseminated prostate cancer. The possibility to improve the therapeutic index via combination therapies also warrants further investigation. Here, the authors developed and characterized a promising GRPR‐targeting radioligand and demonstrated its therapeutic efficacy in prostate cancer xenografts. Moreover, this study using the anti‐HER2 antibody trastuzumab presents the first in vivo proof‐of‐principle that the effects of anti‐GRPR radiotherapy can be amplified by co‐administration of anti‐HER2 treatment leading to prolonged survival.
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Selection of the optimal macrocyclic chelators for labeling with 111In and 68Ga improves contrast of HER2 imaging using engineered scaffold protein ADAPT6. Eur J Pharm Biopharm 2019; 140:109-120. [PMID: 31082509 DOI: 10.1016/j.ejpb.2019.05.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 05/07/2019] [Accepted: 05/09/2019] [Indexed: 12/16/2022]
Abstract
Radionuclide molecular imaging is a promising tool that becomes increasingly important as targeted cancer therapies are developed. To ensure an effective treatment, a molecular stratification of the cancer is a necessity. To accomplish this, visualization of cancer associated molecular abnormalities in vivo by molecular imaging is the method of choice. ADAPTs, a novel type of small protein scaffold, have been utilized to select and develop high affinity binders to different proteinaceous targets. One of these binders, ADAPT6 selectively interacts with human epidermal growth factor 2 (HER2) with low nanomolar affinity and can therefore be used for its in vivo visualization. Molecular design and optimization of labeled anti-HER2 ADAPT has been explored in several earlier studies, showing that small changes in the scaffold affect the biodistribution of the domain. In this study, we evaluate how the biodistribution properties of ADAPT6 is affected by the commonly used maleimido derivatives of the macrocyclic chelators NOTA, NODAGA, DOTA and DOTAGA with the aim to select the best variants for SPECT and PET imaging. The different conjugates were labeled with 111In for SPECT and 68Ga for PET. The acquired data show that the combination of a radionuclide and a chelator for its conjugation has a strong influence on the uptake of ADAPT6 in normal tissues and thereby gives a significant variation in tumor-to-organ ratios. Hence, it was concluded that the best variant for SPECT imaging is 111In-(HE)3DANS-ADAPT6-GSSC-DOTA while the best variant for PET imaging is 68Ga-(HE)3DANS-ADAPT6-GSSC-NODAGA.
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Comparison of tumor‑targeting properties of directly and indirectly radioiodinated designed ankyrin repeat protein (DARPin) G3 variants for molecular imaging of HER2. Int J Oncol 2019; 54:1209-1220. [PMID: 30968147 PMCID: PMC6411343 DOI: 10.3892/ijo.2019.4712] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 01/25/2019] [Indexed: 12/12/2022] Open
Abstract
Evaluation of human epidermal growth factor receptor 2 (HER2) expression levels in breast and gastroesophageal cancer is used for the stratification of patients for HER2‑targeting therapies. The use of radionuclide molecular imaging may facilitate such evaluation in a non‑invasive way. Designed ankyrin repeat proteins (DARPins) are engineered scaffold proteins with high potential as probes for radionuclide molecular imaging. DARPin G3 binds with high affinity to HER2 and may be used to visualize this important therapeutic target. Studies on other engineered scaffold proteins have demonstrated that selection of the optimal labeling approach improves the sensitivity and specificity of radionuclide imaging. The present study compared two methods of labeling G3, direct and indirect radioiodination, to select an approach providing the best imaging contrast. G3‑H6 was labeled with iodine‑124, iodine‑125 and iodine‑131 using a direct method. A novel construct bearing a C‑terminal cysteine, G3‑GGGC, was site‑specifically labeled using [125I]I‑iodo‑[(4‑hydroxyphenyl)ethyl]maleimide (HPEM). The two radiolabeled G3 variants preserved binding specificity and high affinity to HER2‑expressing cells. The specificity of tumor targeting in vivo was demonstrated. Biodistribution comparison of [131I]I‑G3‑H6 and [125I]I‑HPEM‑G3‑GGGC in mice, bearing HER2‑expressing SKOV3 xenografts, demonstrated an appreciable contribution of hepatobiliary excretion to the clearance of [125I]I‑HPEM‑G3‑GGGC and a decreased tumor uptake compared to [131I]I‑G3‑H6. The direct label provided higher tumor‑to‑blood and tumor‑to‑organ ratios compared with the indirect label at 4 h post‑injection. The feasibility of high contrast PET/CT imaging of HER2 expression in SKOV3 xenografts in mice using [124I]I‑G3‑H6 was demonstrated. In conclusion, direct radioiodination is the preferable approach for labeling DARPin G3 with iodine‑123 and iodine‑124 for clinical single photon emission computed tomography and positron emission tomography imaging.
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Comparative Evaluation of Two DARPin Variants: Effect of Affinity, Size, and Label on Tumor Targeting Properties. Mol Pharm 2019; 16:995-1008. [PMID: 30608701 DOI: 10.1021/acs.molpharmaceut.8b00922] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Designed ankyrin repeat proteins (DARPins) are small engineered scaffold proteins that can be selected for binding to desirable molecular targets. High affinity and small size of DARPins render them promising probes for radionuclide molecular imaging. However, detailed knowledge on many factors influencing their imaging properties is still lacking. We have evaluated two human epidermal growth factor 2 (HER2)-specific DARPins with different size and binding properties. DARPins 9_29-H6 and G3-H6 were radiolabeled with iodine-125 and tricarbonyl technetium-99m and evaluated in vitro. A side-by-side comparison of biodistribution and tumor targeting was performed. HER2-specific tumor accumulation of G3-H6 was demonstrated. A combination of smaller size and higher affinity resulted in a higher tumor uptake of G3-H6 in comparison to 9_29-H6. Technetium-99m labeled G3-H6 demonstrated a better biodistribution profile than 9_29-H6, with several-fold lower uptake in liver. Radioiodinated G3-H6 showed the best tumor-to-organ ratios. The combined effect of affinity, molecular weight, scaffold composition, and nonresidualizing properties of iodine label provided radioiodinated G3-H6 with high clinical potential for imaging of HER2.
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Optimization of HER3 expression imaging using affibody molecules: Influence of chelator for labeling with indium-111. Sci Rep 2019; 9:655. [PMID: 30679757 PMCID: PMC6345776 DOI: 10.1038/s41598-018-36827-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 11/09/2018] [Indexed: 12/21/2022] Open
Abstract
Radionuclide molecular imaging of human epidermal growth factor receptor 3 (HER3) expression using affibody molecules could be used for patient stratification for HER3-targeted cancer therapeutics. We hypothesized that the properties of HER3-targeting affibody molecules might be improved through modification of the radiometal-chelator complex. Macrocyclic chelators NOTA (1,4,7-triazacyclononane-N,N',N''-triacetic acid), NODAGA (1-(1,3-carboxypropyl)-4,7-carboxymethyl-1,4,7-triazacyclononane), DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), and DOTAGA (1,4,7,10-tetraazacyclododececane,1-(glutaric acid)-4,7,10-triacetic acid) were conjugated to the C-terminus of anti-HER3 affibody molecule Z08698 and conjugates were labeled with indium-111. All conjugates bound specifically and with picomolar affinity to HER3 in vitro. In mice bearing HER3-expressing xenografts, no significant difference in tumor uptake between the conjugates was observed. Presence of the negatively charged 111In-DOTAGA-complex resulted in the lowest hepatic uptake and the highest tumor-to-liver ratio. In conclusion, the choice of chelator influences the biodistribution of indium-111 labeled anti-HER3 affibody molecules. Hepatic uptake of anti-HER3 affibody molecules could be reduced by the increase of negative charge of the radiometal-chelator complex on the C-terminus without significantly influencing the tumor uptake.
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Comparative evaluation of dimeric and monomeric forms of ADAPT scaffold protein for targeting of HER2-expressing tumours. Eur J Pharm Biopharm 2018; 134:37-48. [PMID: 30408518 DOI: 10.1016/j.ejpb.2018.11.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 10/19/2018] [Accepted: 11/04/2018] [Indexed: 12/23/2022]
Abstract
ADAPTs are small engineered non-immunoglobulin scaffold proteins, which have demonstrated very promising features as vectors for radionuclide tumour targeting. Radionuclide imaging of human epidermal growth factor 2 (HER2) expression in vivo might be used for stratification of patients for HER2-targeting therapies. ADAPT6, which specifically binds to HER2, has earlier been shown to have very promising features for in vivo targeting of HER2 expressing tumours. In this study we tested the hypothesis that dimerization of ADAPT6 would increase the apparent affinity to HER2 and accordingly improve tumour targeting. To find an optimal molecular design of dimers, a series of ADAPT dimers with different linkers, -SSSG- (DiADAPT6L1), -(SSSG)2- (DiADAPT6L2), and -(SSSG)3- (DiADAPT6L3) was evaluated. Dimers in combination with optimal linker lengths demonstrated increased apparent affinity to HER2. The best variants, DiADAPT6L2 and DiADAPT6L3 were site-specifically labelled with 111In and 125I, and compared with a monomeric ADAPT6 in mice bearing HER2-expressing tumours. Despite higher affinity, both dimers had lower tumour uptake and lower tumour-to-organ ratios compared to the monomer. We conclude that improved affinity of a dimeric form of ADAPT does not compensate the disadvantage of increased size. Therefore, increase of affinity should be obtained by affinity maturation and not by dimerization.
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Affibody‑mediated imaging of EGFR expression in prostate cancer using radiocobalt‑labeled DOTA‑ZEGFR:2377. Oncol Rep 2018; 41:534-542. [PMID: 30320363 DOI: 10.3892/or.2018.6792] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 09/20/2018] [Indexed: 11/06/2022] Open
Abstract
The epidermal growth factor receptor (EGFR) is often overexpressed during prostate cancer (PCa) progression towards androgen‑independence after hormone therapy, but the overexpression is lower than in other types of cancers. Despite the low expression, EGFR has emerged as a promising therapeutic target for patients with castration‑resistant PCa. Non‑invasive methods for determination of EGFR expression in PCa can serve for patient stratification and therapy response monitoring. Radionuclide imaging probes based on affibody molecules (7 kDa) provide high contrast imaging of cancer‑associated molecular targets. We hypothesized that the anti‑EGFR affibody molecule DOTA‑ZEGFR:2377 labeled with 55Co (positron‑emitter, T1/2=17.5 h) would enable imaging of EGFR expression in PCa xenografts. The human PCa cell line DU‑145 was used for in vitro and in vivo experiments and 57Co was used as a surrogate for 55Co in the present study. Binding of 57Co‑DOTA‑ZEGFR:2377 to EGFR‑expressing xenografts was saturable with anti‑EGFR monoclonal antibody cetuximab, which would motivate the use of this tracer for monitoring the receptor occupancy during treatment. A significant dose‑dependent difference in radioactivity accumulation in tumors and normal organs was observed when the biodistribution was studied 3 h after the injection of 10 and 35 µg of 57Co‑DOTA‑ZEGFR:2377: At lower doses the tumor uptake was 2‑fold higher although tumor‑to‑organ ratios were not altered. For clinically relevant organs for PCa, tumor‑to‑organ ratios increased with time, and at 24 h pi were 2.2±0.5 for colon, 7±2 for muscle, and 4.0±0.7 for bones. Small animal SPECT/CT images confirmed the capacity of radiocobalt labeled DOTA‑ZEGFR:2377 to visualize EGFR expression in PCa. In conclusion, the present study demonstrated the feasibility of using the radiocobalt labeled anti‑EGFR affibody conjugate ZEGFR:2377 as an imaging agent for in vivo visualization of low EGFR‑expressing tumors, like PCa, and for monitoring of receptor occupancy during cetuximab therapy as well as the importance of optimal dosing in order to achieve higher sensitivity molecular imaging.
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Radionuclide imaging of VEGFR2 in glioma vasculature using biparatopic affibody conjugate: proof-of-principle in a murine model. Theranostics 2018; 8:4462-4476. [PMID: 30214632 PMCID: PMC6134937 DOI: 10.7150/thno.24395] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2017] [Accepted: 04/21/2018] [Indexed: 01/09/2023] Open
Abstract
Vascular endothelial growth factor receptor-2 (VEGFR2) is a key mediator of angiogenesis and therefore a promising therapeutic target in malignancies including glioblastoma multiforme (GBM). Molecular imaging of VEGFR2 expression may enable patient stratification for antiangiogenic therapy. The goal of the current study was to evaluate the capacity of the novel anti-VEGFR2 biparatopic affibody conjugate (ZVEGFR2-Bp2) for in vivo visualization of VEGFR2 expression in GBM. Methods: ZVEGFR2-Bp2 coupled to a NODAGA chelator was generated and radiolabeled with indium-111. The VEGFR2-expressing murine endothelial cell line MS1 was used to evaluate in vitro binding specificity and affinity, cellular processing and targeting specificity in mice. Further tumor targeting was studied in vivo in GL261 glioblastoma orthotopic tumors. Experimental imaging was performed. Results: [111In]In-NODAGA-ZVEGFR2-Bp2 bound specifically to VEGFR2 (KD=33±18 pM). VEGFR2-mediated accumulation was observed in liver, spleen and lungs. The tumor-to-organ ratios 2 h post injection for mice bearing MS1 tumors were approximately 11 for blood, 15 for muscles and 78 for brain. Intracranial GL261 glioblastoma was visualized using SPECT/CT. The activity uptake in tumors was significantly higher than in normal brain tissue. The tumor-to-cerebellum ratios after injection of 4 µg [111In]In-NODAGA-ZVEGFR2-Bp2 were significantly higher than the ratios observed for the 40 µg injected dose and for the non-VEGFR2 binding size-matched conjugate, demonstrating target specificity. Microautoradiography of cryosectioned CNS tissue was in good agreement with the SPECT/CT images. Conclusion: The anti-VEGFR2 affibody conjugate [111In]In-NODAGA-ZVEGFR2-Bp2 specifically targeted VEGFR2 in vivo and visualized its expression in a murine GBM orthotopic model. Tumor-to-blood ratios for [111In]In-NODAGA-ZVEGFR2-Bp2 were higher compared to other VEGFR2 imaging probes. [111In]In-NODAGA-ZVEGFR2-Bp2 appears to be a promising probe for in vivo noninvasive visualization of tumor angiogenesis in glioblastoma.
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Development of an optimal imaging strategy for selection of patients for affibody-based PNA-mediated radionuclide therapy. Sci Rep 2018; 8:9643. [PMID: 29942011 PMCID: PMC6018533 DOI: 10.1038/s41598-018-27886-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 06/08/2018] [Indexed: 01/03/2023] Open
Abstract
Affibody molecules are engineered scaffold proteins, which demonstrated excellent binding to selected tumor-associated molecular abnormalities in vivo and highly sensitive and specific radionuclide imaging of Her2-expressing tumors in clinics. Recently, we have shown that peptide nucleic acid (PNA)-mediated affibody-based pretargeted radionuclide therapy using beta-emitting radionuclide 177Lu extended significantly survival of mice bearing human Her2-expressing tumor xenografts. In this study, we evaluated two approaches to use positron emission tomography (PET) for stratification of patients for affibody-based pretargeting therapy. The primary targeting probe ZHER2:342-SR-HP1 and the secondary probe HP2 (both conjugated with DOTA chelator) were labeled with the positron-emitting radionuclide 68Ga. Biodistribution of both probes was measured in BALB/C nu/nu mice bearing either SKOV-3 xenografts with high Her2 expression or DU-145 xenografts with low Her2 expression. 68Ga-HP2 was evaluated in the pretargeting setting. Tumor uptake of both probes was compared with the uptake of pretargeted 177Lu-HP2. The uptake of both 68Ga-ZHER2:342-SR-HP1 and 68Ga-HP2 depended on Her2-expression level providing clear discrimination of between tumors with high and low Her2 expression. Tumor uptake of 68Ga-HP2 correlated better with the uptake of 177Lu-HP2 than the uptake of 68Ga-ZHER2:342-SR-HP1. The use of 68Ga-HP2 as a theranostics counterpart would be preferable approach for clinical translation.
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Abstract
Radionuclide molecular imaging is a promising tool for visualization of cancer associated molecular abnormalities in vivo and stratification of patients for specific therapies. ADAPT is a new type of small engineered proteins based on the scaffold of an albumin binding domain of protein G. ADAPTs have been utilized to select and develop high affinity binders to different proteinaceous targets. ADAPT6 binds to human epidermal growth factor 2 (HER2) with low nanomolar affinity and can be used for its in vivo visualization. Molecular design of 111In-labeled anti-HER2 ADAPT has been optimized in several earlier studies. In this study, we made a direct comparison of two of the most promising variants, having either a DEAVDANS or a (HE)3DANS sequence at the N-terminus, conjugated with a maleimido derivative of DOTA to a GSSC amino acids sequence at the C-terminus. The variants (designated DOTA-C59-DEAVDANS-ADAPT6-GSSC and DOTA-C61-(HE)3DANS-ADAPT6-GSSC) were stably labeled with 111In for SPECT and 68Ga for PET. Biodistribution of labeled ADAPT variants was evaluated in nude mice bearing human tumor xenografts with different levels of HER2 expression. Both variants enabled clear discrimination between tumors with high and low levels of HER2 expression. 111In-labeled ADAPT6 derivatives provided higher tumor-to-organ ratios compared to 68Ga-labeled counterparts. The best performing variant was DOTA-C61-(HE)3DANS-ADAPT6-GSSC, which provided tumor-to-blood ratios of 208 ± 36 and 109 ± 17 at 3 h for 111In and 68Ga labels, respectively.
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Radionuclide Therapy of HER2-Expressing Human Xenografts Using Affibody-Based Peptide Nucleic Acid-Mediated Pretargeting: In Vivo Proof of Principle. J Nucl Med 2018; 59:1092-1098. [PMID: 29439013 DOI: 10.2967/jnumed.118.208348] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 01/23/2018] [Indexed: 12/25/2022] Open
Abstract
Affibody molecules are small proteins engineered using a nonantibody scaffold. Radiolabeled Affibody molecules are excellent imaging probes, but their application to radionuclide therapy has been prevented by high renal reabsorption. The aim of this study was to test the hypothesis that Affibody-based peptide nucleic acid (PNA)-mediated pretargeted therapy of human epidermal growth factor receptor 2 (HER2)-expressing cancer extends survival without accompanying renal toxicity. Methods: A HER2-targeting Affibody molecule ligated with an AGTCGTGATGTAGTC PNA hybridization probe (ZHER2:342-SR-HP1) was used as the primary pretargeting agent. A complementary AGTCGTGATGTAGTC PNA conjugated to the chelator DOTA and labeled with the radionuclide 177Lu (177Lu-HP2) was used as the secondary agent. The influence of different factors on pretargeting was investigated. Experimental radionuclide therapy in mice bearing SKOV-3 xenografts was performed in 6 cycles separated by 7 d. Results: Optimal tumor targeting was achieved when 16 MBq/3.5 μg (0.65 nmol) of 177Lu-HP2 was injected 16 h after injection of 100 μg (7.7 nmol) of ZHER2:342-SR-HP1. The calculated absorbed dose to tumors was 1,075 mGy/MBq, whereas the absorbed dose to kidneys was 206 mGy/MBq and the absorbed dose to blood (surrogate of bone marrow) was 4 mGy/MBq. Survival of mice was significantly longer (P < 0.05) in the treatment group (66 d) than in the control groups treated with the same amount of ZHER2:342-SR-HP1 only (37 d), the same amount and activity of 177Lu-HP2 only (32 d), or phosphate-buffered saline (37 d). Conclusion: The studied pretargeting system can deliver an absorbed dose to tumors appreciably exceeding absorbed doses to critical organs, making Affibody-based PNA-mediated pretargeted radionuclide therapy highly attractive.
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Abstracts of the 33rd International Austrian Winter Symposium : Zell am See, Austria. 24-27 January 2018. EJNMMI Res 2018; 8:5. [PMID: 29362999 PMCID: PMC5780335 DOI: 10.1186/s13550-017-0354-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Cyclic versus Noncyclic Chelating Scaffold for 89Zr-Labeled ZEGFR:2377 Affibody Bioconjugates Targeting Epidermal Growth Factor Receptor Overexpression. Mol Pharm 2017; 15:175-185. [PMID: 29160082 PMCID: PMC5751887 DOI: 10.1021/acs.molpharmaceut.7b00787] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
![]()
Zirconium-89
is an emerging radionuclide for positron emission
tomography (PET) especially for biomolecules with slow pharmacokinetics
as due to its longer half-life, in comparison to fluorine-18 and gallium-68,
imaging at late time points is feasible. Desferrioxamine B (DFO),
a linear bifunctional chelator (BFC) is mostly used for this radionuclide
so far but shows limitations regarding stability. Our group recently
reported on fusarinine C (FSC) with similar zirconium-89 complexing
properties but potentially higher stability related to its cyclic
structure. This study was designed to compare FSC and DFO head-to-head
as bifunctional chelators for 89Zr-radiolabeled EGFR-targeting
ZEGFR:2377 affibody bioconjugates. FSC-ZEGFR:2377 and DFO-ZEGFR:2377
were evaluated regarding radiolabeling, in vitro stability,
specificity, cell uptake, receptor affinity, biodistribution, and
microPET-CT imaging. Both conjugates were efficiently labeled with
zirconium-89 at room temperature but radiochemical yields increased
substantially at elevated temperature, 85 °C. Both 89Zr-FSC-ZEGFR:2377 and 89Zr-DFO-ZEGFR:2377 revealed remarkable
specificity, affinity and slow cell-line dependent internalization.
Radiolabeling at 85 °C showed comparable results in A431 tumor
xenografted mice with minor differences regarding blood clearance,
tumor and liver uptake. In comparison 89Zr-DFO-ZEGFR:2377,
radiolabeled at room temperature, showed a significant difference
regarding tumor-to-organ ratios. MicroPET-CT imaging studies of 89Zr-FSC-ZEGFR:2377 as well as 89Zr-DFO-ZEGFR:2377
confirmed these findings. In summary we were able to show that FSC
is a suitable alternative to DFO for radiolabeling of biomolecules
with zirconium-89. Furthermore, our findings indicate that 89Zr-radiolabeling of DFO conjugates at higher temperature reduces
off-chelate binding leading to significantly improved tumor-to-organ
ratios and therefore enhancing image contrast.
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Comparative evaluation of tumor targeting using the anti-HER2 ADAPT scaffold protein labeled at the C-terminus with indium-111 or technetium-99m. Sci Rep 2017; 7:14780. [PMID: 29116215 PMCID: PMC5676751 DOI: 10.1038/s41598-017-15366-w] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 10/20/2017] [Indexed: 12/29/2022] Open
Abstract
ABD-Derived Affinity Proteins (ADAPTs) is a novel class of engineered scaffold proteins derived from an albumin-binding domain of protein G. The use of ADAPT6 derivatives as targeting moiety have provided excellent preclinical radionuclide imaging of human epidermal growth factor 2 (HER2) tumor xenografts. Previous studies have demonstrated that selection of nuclide and chelator for its conjugation has an appreciable effect on imaging properties of scaffold proteins. In this study we performed a comparative evaluation of the anti-HER2 ADAPT having an aspartate-glutamate-alanine-valine-aspartate-alanine-asparagine-serine (DEAVDANS) N-terminal sequence and labeled at C-terminus with 99mTc using a cysteine-containing peptide based chelator, glycine-serine-serine-cysteine (GSSC), and a similar variant labeled with 111In using a maleimido derivative of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelator. Both 99mTc-DEAVDANS-ADAPT6-GSSC and 111In-DEAVDANS-ADAPT6-GSSC-DOTA accumulated specifically in HER2-expressing SKOV3 xenografts. The tumor uptake of both variants did not differ significantly and average values were in the range of 19–21%ID/g. However, there was an appreciable variation in uptake of conjugates in normal tissues that resulted in a notable difference in the tumor-to-organ ratios. The 111In-DOTA label provided 2–6 fold higher tumor-to-organ ratios than 99mTc-GSSC and is therefore the preferable label for ADAPTs.
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Evaluation of a radiocobalt-labelled affibody molecule for imaging of human epidermal growth factor receptor 3 expression. Int J Oncol 2017; 51:1765-1774. [PMID: 29039474 DOI: 10.3892/ijo.2017.4152] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 08/25/2017] [Indexed: 11/06/2022] Open
Abstract
The human epidermal growth factor receptor 3 (HER3) is involved in the development of cancer resistance towards tyrosine kinase-targeted therapies. Several HER3‑targeting therapeutics are currently under clinical evaluation. Non-invasive imaging of HER3 expression could improve patient management. Affibody molecules are small engineered scaffold proteins demonstrating superior properties as targeting probes for molecular imaging compared with monoclonal antibodies. Feasibility of in vivo HER3 imaging using affibody molecules has been previously demonstrated. Preclinical studies have shown that the contrast when imaging using anti-HER3 affibody molecules can be improved over time. We aim to develop an agent for PET imaging of HER3 expression using the long-lived positron-emitting radionuclide cobalt-55 (55Co) (T1/2=17.5 h). A long-lived cobalt isotope 57Co was used as a surrogate for 55Co in this study. The anti-HER3 affibody molecule HEHEHE-ZHER3-NOTA was labelled with radiocobalt with high yield, purity and stability. Biodistribution of 57Co-HEHEHE-ZHER3-NOTA was measured in mice bearing DU145 (prostate carcinoma) and LS174T (colorectal carcinoma) xenografts at 3 and 24 h post injection (p.i.). Tumour-to-blood ratios significantly increased between 3 and 24 h p.i. (p<0.05). At 24 h p.i., tumour-to-blood ratios were 6 for DU145 and 8 for LS174T xenografts, respectively. HER3‑expressing xenografts were clearly visualized in a preclinical imaging setting already 3 h p.i., and contrast further improved at 24 h p.i. In conclusion, the radiocobalt-labelled anti-HER3 affibody molecule, HEHEHE-ZHER3-NOTA, is a promising tracer for imaging of HER3 expression in tumours.
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Radionuclide Tumor Targeting Using ADAPT Scaffold Proteins: Aspects of Label Positioning and Residualizing Properties of the Label. J Nucl Med 2017; 59:93-99. [PMID: 28864631 DOI: 10.2967/jnumed.117.197202] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 08/10/2017] [Indexed: 12/13/2022] Open
Abstract
Visualization of cancer-associated alterations of molecular phenotype using radionuclide imaging is a noninvasive approach to stratifying patients for targeted therapies. The engineered albumin-binding domain-derived affinity protein (ADAPT) is a promising tracer for radionuclide molecular imaging because of its small size (6.5 kDa), which satisfies the precondition for efficient tumor penetration and rapid clearance. Previous studies demonstrated that the human epidermal growth factor receptor type 2 (HER2)-targeting ADAPT6 labeled with radiometals at the N terminus is able to image HER2 expression in xenografts a few hours after injection. The aim of this study was to evaluate whether the use of a nonresidualizing label or placement of the labels at the C terminus would further improve the targeting properties of ADAPT6. Methods: Two constructs, Cys2-ADAPT6 and Cys59-ADAPT6, having the (HE)3DANS sequence at the N terminus were produced and site-specifically labeled using 111In-DOTA or 125I-iodo-((4-hydroxyphenyl)ethyl) maleimide (HPEM). The conjugates were compared in vitro and in vivo. HER2-targeting properties and biodistribution were evaluated in BALB/C nu/nu mice bearing ovarian carcinoma cell (SKOV-3) xenografts. Results: Specific HER2 binding and high affinity were preserved after labeling. Both Cys2-ADAPT6 and Cys59-ADAPT6 were internalized slowly by HER2-expressing cancer cells. Depending on the label position, uptake at 4 h after injection varied from 10% to 22% of the injected dose per gram of tumor tissue. Regardless of terminus position, the 125I-HPEM label provided more than 140-fold lower renal uptake than the 111In-DOTA label at 4 after injection. The tumor-to-organ ratios were, in contrast, higher for both of the 111In-DOTA-labeled ADAPT variants in other organs. Tumor-to-blood ratios for 111In-labeled Cys2-ADAPT6 and Cys59-ADAPT6 did not differ significantly (250-280), but 111In-DOTA-Cys59-ADAPT6 provided significantly higher tumor-to-lung, tumor-to-liver, tumor-to-spleen, and tumor-to-muscle ratios. Radioiodinated variants had similar tumor-to-organ ratios, but 125I-HPEM-Cys59-ADAPT6 had significantly higher tumor uptake and a higher tumor-to-kidney ratio. Conclusion: Residualizing properties of the label strongly influence the targeting properties of ADAPT6. The position of the radiolabel influences targeting as well, although to a lesser extent. Placement of a label at the C terminus yields the best biodistribution features for both radiometal and radiohalogen labels. Low renal retention of the radioiodine label creates a precondition for radionuclide therapy using 131I-labeled HPEM-Cys59-ADAPT6.
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The use of radiocobalt as a label improves imaging of EGFR using DOTA-conjugated Affibody molecule. Sci Rep 2017; 7:5961. [PMID: 28729680 PMCID: PMC5519605 DOI: 10.1038/s41598-017-05700-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 06/01/2017] [Indexed: 02/04/2023] Open
Abstract
Several anti-cancer therapies target the epidermal growth factor receptor (EGFR). Radionuclide imaging of EGFR expression in tumours may aid in selection of optimal cancer therapy. The 111In-labelled DOTA-conjugated ZEGFR:2377 Affibody molecule was successfully used for imaging of EGFR-expressing xenografts in mice. An optimal combination of radionuclide, chelator and targeting protein may further improve the contrast of radionuclide imaging. The aim of this study was to evaluate the targeting properties of radiocobalt-labelled DOTA-ZEGFR:2377. DOTA-ZEGFR:2377 was labelled with 57Co (T1/2 = 271.8 d), 55Co (T1/2 = 17.5 h), and, for comparison, with the positron-emitting radionuclide 68Ga (T1/2 = 67.6 min) with preserved specificity of binding to EGFR-expressing A431 cells. The long-lived cobalt radioisotope 57Co was used in animal studies. Both 57Co-DOTA-ZEGFR:2377 and 68Ga-DOTA-ZEGFR:2377 demonstrated EGFR-specific accumulation in A431 xenografts and EGFR-expressing tissues in mice. Tumour-to-organ ratios for the radiocobalt-labelled DOTA-ZEGFR:2377 were significantly higher than for the gallium-labelled counterpart already at 3 h after injection. Importantly, 57Co-DOTA-ZEGFR:2377 demonstrated a tumour-to-liver ratio of 3, which is 7-fold higher than the tumour-to-liver ratio for 68Ga-DOTA-ZEGFR:2377. The results of this study suggest that the positron-emitting cobalt isotope 55Co would be an optimal label for DOTA-ZEGFR:2377 and further development should concentrate on this radionuclide as a label.
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Evaluation of affibody molecule-based PNA-mediated radionuclide pretargeting: Development of an optimized conjugation protocol and 177Lu labeling. Nucl Med Biol 2017; 54:1-9. [PMID: 28810153 DOI: 10.1016/j.nucmedbio.2017.07.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 06/30/2017] [Accepted: 07/04/2017] [Indexed: 12/20/2022]
Abstract
INTRODUCTION We have previously developed a pretargeting approach for affibody-mediated cancer therapy based on PNA-PNA hybridization. In this article we have further developed this approach by optimizing the production of the primary agent, ZHER2:342-SR-HP1, and labeling the secondary agent, HP2, with the therapeutic radionuclide 177Lu. We also studied the biodistribution profile of 177Lu-HP2 in mice, and evaluated pretargeting with 177Lu-HP2 in vitro and in vivo. METHODS The biodistribution profile of 177Lu-HP2 was evaluated in NMRI mice and compared to the previously studied 111In-HP2. Pretargeting using 177Lu-HP2 was studied in vitro using the HER2-expressing cell lines BT-474 and SKOV-3, and in vivo in mice bearing SKOV-3 xenografts. RESULTS AND CONCLUSION Using an optimized production protocol for ZHER2:342-SR-HP1 the ligation time was reduced from 15h to 30min, and the yield increased from 45% to 70%. 177Lu-labeled HP2 binds specifically in vitro to BT474 and SKOV-3 cells pre-treated with ZHER2:342-SR-HP1. 177Lu-HP2 was shown to have a more rapid blood clearance compared to 111In-HP2 in NMRI mice, and the measured radioactivity in blood was 0.22±0.1 and 0.68±0.07%ID/g for 177Lu- and 111In-HP2, respectively, at 1h p.i. In contrast, no significant difference in kidney uptake was observed (4.47±1.17 and 3.94±0.58%ID/g for 177Lu- and 111In-HP2, respectively, at 1h p.i.). Co-injection with either Gelofusine or lysine significantly reduced the kidney uptake for 177Lu-HP2 (1.0±0.1 and 1.6±0.2, respectively, vs. 2.97±0.87%ID/g in controls at 4h p.i.). 177Lu-HP2 accumulated in SKOV-3 xenografts in BALB/C nu/nu mice when administered after injection of ZHER2:342-SR-HP1. Without pre-injection of ZHER2:342-SR-HP1, the uptake of 177Lu-HP2 was about 90-fold lower in tumor (0.23±0.08 vs. 20.7±3.5%ID/g). The tumor-to-kidney radioactivity accumulation ratio was almost 5-fold higher in the group of mice pre-injected with ZHER2:342-SR-HP1. In conclusion, 177Lu-HP2 was shown to be a promising secondary agent for affibody-mediated tumor pretargeting in vivo.
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Synthesis of 11C-labeled Sulfonyl Carbamates through a Multicomponent Reaction Employing Sulfonyl Azides, Alcohols, and [ 11C]CO. ChemistryOpen 2016; 5:566-573. [PMID: 28032026 PMCID: PMC5167284 DOI: 10.1002/open.201600091] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Indexed: 12/13/2022] Open
Abstract
We describe the development of a new methodology focusing on 11C-labeling of sulfonyl carbamates in a multicomponent reaction comprised of a sulfonyl azide, an alkyl alcohol, and [11C]CO. A number of 11C-labeled sulfonyl carbamates were synthesized and isolated, and the developed methodology was then applied in the preparation of a biologically active molecule. The target compound was obtained in 24±10 % isolated radiochemical yield and was evaluated for binding properties in a tumor cell assay; in vivo biodistribution and imaging studies were also performed. This represents the first successful radiolabeling of a non-peptide angiotensin II receptor subtype 2 agonist, C21, currently in clinical trials for the treatment of idiopathic pulmonary fibrosis.
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Influence of the N-Terminal Composition on Targeting Properties of Radiometal-Labeled Anti-HER2 Scaffold Protein ADAPT6. Bioconjug Chem 2016; 27:2678-2688. [PMID: 27740752 DOI: 10.1021/acs.bioconjchem.6b00465] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Radionuclide-imaging-based stratification of patients to targeted therapies makes cancer treatment more personalized and therefore more efficient. Albumin-binding domain derived affinity proteins (ADAPTs) constitute a novel group of imaging probes based on the scaffold of an albumin-binding domain (ABD). To evaluate how different compositions of the N-terminal sequence of ADAPTs influence their biodistribution, a series of human epidermal growth factor receptor type 2 (HER2)-binding ADAPT6 derivatives with different N-terminal sequences were created: GCH6DANS (2), GC(HE)3DANS (3), GCDEAVDANS (4), and GCVDANS(5). These were compared with the parental variant: GCSS(HE)3DEAVDANS (1). All variants were site-specifically conjugated with a maleimido-derivative of a DOTA chelator and labeled with 111In. Binding to HER2-expressing cells in vitro, in vivo biodistribution as well as targeting properties of the new variants were compared with properties of the 111In-labeled parental ADAPT variant 1 (111In-DOTA-1). The composition of the N-terminal sequence had an apparent influence on biodistribution of ADAPT6 in mice. The use of a hexahistidine tag in 111In-DOTA-2 was associated with elevated hepatic uptake compared to the (HE)3-containing counterpart, 111In-DOTA-3. All new variants without a hexahistidine tag demonstrated lower uptake in blood, lung, spleen, and muscle compared to uptake in the parental variant. The best new variants, 111In-DOTA-3 and 111In-DOTA-5, provided tumor uptakes of 14.6 ± 2.4 and 12.5 ± 1.3% ID/g at 4 h after injection, respectively. The tumor uptake of 111In-DOTA-3 was significantly higher than the uptake of the parental 111In-DOTA-1 (9.1 ± 2.0% ID/g). The tumor-to-blood ratios of 395 ± 75 and 419 ± 91 at 4 h after injection were obtained for 111In-DOTA-5 and 111In-DOTA-3, respectively. In conclusion, the N-terminal sequence composition affects the biodistribution and targeting properties of ADAPT-based imaging probes, and its optimization may improve imaging contrast.
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Feasibility of imaging of epidermal growth factor receptor expression with ZEGFR:2377 affibody molecule labeled with 99mTc using a peptide-based cysteine-containing chelator. Int J Oncol 2016; 49:2285-2293. [PMID: 27748899 PMCID: PMC5118000 DOI: 10.3892/ijo.2016.3721] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 08/30/2016] [Indexed: 12/13/2022] Open
Abstract
The epidermal growth factor receptor (EGFR) is overexpressed in a number of malignant tumors and is a molecular target for several specific anticancer antibodies and tyrosine kinase inhibitors. The overexpression of EGFR is a predictive biomarker for response to several therapy regimens. Radionuclide molecular imaging might enable detection of EGFR overexpression by a non-invasive procedure and could be used repeatedly. Affibody molecules are engineered scaffold proteins, which could be selected to have a high affinity and selectivity to predetermined targets. The anti-EGFR ZEGFR:2377 affibody molecule is a potential imaging probe for EGFR detection. The use of the generator-produced radionuclide 99mTc should facilitate clinical translation of an imaging probe due to its low price, availability and favorable dosimetry of the radionuclide. In the present study, we evaluated feasibility of ZEGFR:2377 labeling with 99mTc using a peptide-based cysteine-containing chelator expressed at the C-terminus of ZEGFR:2377. The label was stable in vitro under cysteine challenge. In addition, 99mTc-ZEGFR:2377 was capable of specific binding to EGFR-expressing cells with high affinity (274 pM). Studies in BALB/C nu/nu mice bearing A431 xenografts demonstrated that 99mTc-ZEGFR:2377 accumulates in tumors in an EGFR-specific manner. The tumor uptake values were 3.6±1 and 2.5±0.4% ID/g at 3 and 24 h after injection, respectively. The corresponding tumor-to-blood ratios were 1.8±0.4 and 8±3. The xenografts were clearly visualized at both time-points. This study demonstrated the potential of 99mTc-labeled ZEGFR:2377 for imaging of EGFR in vivo.
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Comparative Evaluation of Affibody Molecules for Radionuclide Imaging of in Vivo Expression of Carbonic Anhydrase IX. Mol Pharm 2016; 13:3676-3687. [PMID: 27529191 DOI: 10.1021/acs.molpharmaceut.6b00502] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Overexpression of the enzyme carbonic anhydrase IX (CAIX) is documented for chronically hypoxic malignant tumors as well as for normoxic renal cell carcinoma. Radionuclide molecular imaging of CAIX would be useful for detection of hypoxic areas in malignant tumors, for patients' stratification for CAIX-targeted therapies, and for discrimination of primary malignant and benign renal tumors. Earlier, we have reported feasibility of in vivo radionuclide based imaging of CAIX expressing tumors using Affibody molecules, small affinity proteins based on a nonimmunoglobulin scaffold. In this study, we compared imaging properties of several anti-CAIX Affibody molecules having identical scaffold parts and competing for the same epitope on CAIX, but having different binding paratopes. Four variants were labeled using residualizing 99mTc and nonresidualizing 125I labels. All radiolabeled variants demonstrated high-affinity detection of CAIX-expressing cell line SK-RC-52 in vitro and specific accumulation in SK-RC-52 xenografts in vivo. 125I-labeled conjugates demonstrated much lower radioactivity uptake in kidneys but higher radioactivity concentration in blood compared with 99mTc-labeled counterparts. Although all variants cleared rapidly from blood and nonspecific compartments, there was noticeable difference in their biodistribution. The best variant for imaging of expression of CAIX in disseminated cancer was 99mTc-(HE)3-ZCAIX:2 providing tumor uptake of 16.3 ± 0.9% ID/g and tumor-to-blood ratio of 44 ± 7 at 4 h after injection. For primary renal cell carcinoma, the most promising imaging candidate was 125I-ZCAIX:4 providing tumor-kidney ratio of 2.1 ± 0.5. In conclusion, several clones of scaffold proteins should be evaluated to select the best variant for development of an imaging probe with optimal sensitivity for the intended application.
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Increasing the Net Negative Charge by Replacement of DOTA Chelator with DOTAGA Improves the Biodistribution of Radiolabeled Second-Generation Synthetic Affibody Molecules. Mol Pharm 2016; 13:1668-78. [PMID: 27010700 DOI: 10.1021/acs.molpharmaceut.6b00089] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
A promising strategy to enable patient stratification for targeted therapies is to monitor the target expression in a tumor by radionuclide molecular imaging. Affibody molecules (7 kDa) are nonimmunoglobulin scaffold proteins with a 25-fold smaller size than intact antibodies. They have shown an apparent potential as molecular imaging probes both in preclinical and clinical studies. Earlier, we found that hepatic uptake can be reduced by the incorporation of negatively charged purification tags at the N-terminus of Affibody molecules. We hypothesized that liver uptake might similarly be reduced by positioning the chelator at the N-terminus, where the chelator-radionuclide complex will provide negative charges. To test this hypothesis, a second generation synthetic anti-HER2 ZHER2:2891 Affibody molecule was synthesized and labeled with (111)In and (68)Ga using DOTAGA and DOTA chelators. The chelators were manually coupled to the N-terminus of ZHER2:2891 forming an amide bond. Labeling DOTAGA-ZHER2:2891 and DOTA-ZHER2:2891 with (68)Ga and (111)In resulted in stable radioconjugates. The tumor-targeting and biodistribution properties of the (111)In- and (68)Ga-labeled conjugates were compared in SKOV-3 tumor-bearing nude mice at 2 h postinjection. The HER2-specific binding of the radioconjugates was verified both in vitro and in vivo. Using the DOTAGA chelator gave significantly lower radioactivity in liver and blood for both radionuclides. The (111)In-labeled conjugates showed more rapid blood clearance than the (68)Ga-labeled conjugates. The most pronounced influence of the chelators was found when they were labeled with (68)Ga. The DOTAGA chelator gave significantly higher tumor-to-blood (61 ± 6 vs 23 ± 5, p < 0.05) and tumor-to-liver (10.4 ± 0.6 vs 4.5 ± 0.5, p < 0.05) ratios than the DOTA chelator. This study demonstrated that chelators may be used to alter the uptake of Affibody molecules, and most likely other scaffold-based imaging probes, for improvement of imaging contrast.
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Selection of optimal chelator improves the contrast of GRPR imaging using bombesin analogue RM26. Int J Oncol 2016; 48:2124-34. [PMID: 26983776 DOI: 10.3892/ijo.2016.3429] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 01/27/2016] [Indexed: 11/05/2022] Open
Abstract
Bombesin (BN) analogs bind with high affinity to gastrin-releasing peptide receptors (GRPRs) that are up-regulated in prostate cancer and can be used for the visualization of prostate cancer. The aim of this study was to investigate the influence of radionuclide-chelator complexes on the biodistribution pattern of the 111In-labeled bombesin antagonist PEG2-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2 (PEG2-RM26) and to identify an optimal construct for SPECT imaging. A series of RM26 analogs N-terminally conjugated with NOTA, NODAGA, DOTA and DOTAGA via a PEG2 spacer were radiolabeled with 111In and evaluated both in vitro and in vivo. The conjugates were successfully labeled with 111In with 100% purity and retained binding specificity to GRPR and high stability. The cellular processing of all compounds was characterized by slow internalization. The IC50 values were in the low nanomolar range, with lower IC50 values for positively charged natIn-NOTA-PEG2-RM26 (2.6 ± 0.1 nM) and higher values for negatively charged natIn-DOTAGA-PEG2-RM26 (4.8 ± 0.5 nM). The kinetic binding studies showed KD values in the picomolar range that followed the same pattern as the IC50 data. The biodistribution of all compounds was studied in BALB/c nu/nu mice bearing PC-3 prostate cancer xenografts. Tumor targeting and biodistribution studies displayed rapid clearance of radioactivity from the blood and normal organs via kidney excretion. All conjugates showed similar uptake in tumors at 4 h p.i. The radioactivity accumulation in GRPR-expressing organs was significantly lower for DOTA- and DOTAGA-containing constructs compared to those containing NOTA and NODAGA. 111In-NOTA-PEG2-RM26 with a positively charged complex showed the highest initial uptake and the slowest clearance of radioactivity from the liver. At 4 h p.i., DOTA- and DOTAGA-coupled analogs showed significantly higher tumor-to-organ ratios compared to NOTA- and NODAGA-containing variants. The NODAGA conjugate demonstrated the best retention of radioactivity in tumors, and, at 24 h p.i., had the highest contrast to blood, muscle and bones.
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PET imaging of epidermal growth factor receptor expression in tumours using 89Zr-labelled ZEGFR:2377 affibody molecules. Int J Oncol 2016; 48:1325-32. [PMID: 26847636 PMCID: PMC4777594 DOI: 10.3892/ijo.2016.3369] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 12/23/2015] [Indexed: 12/25/2022] Open
Abstract
Epidermal growth factor receptor (EGFR) is a transmembrane tyrosine kinase receptor, which is overexpressed in many types of cancer. The use of EGFR-targeting monoclonal antibodies and tyrosine-kinase inhibitors improves significantly survival of patients with colorectal, non-small cell lung cancer and head and neck squamous cell carcinoma. Detection of EGFR overexpression provides important prognostic and predictive information influencing management of the patients. The use of radionuclide molecular imaging would enable non-invasive repeatable determination of EGFR expression in disseminated cancer. Moreover, positron emission tomography (PET) would provide superior sensitivity and quantitation accuracy in EGFR expression imaging. Affibody molecules are a new type of imaging probes, providing high contrast in molecular imaging. In the present study, an EGFR-binding affibody molecule (ZEGFR:2377) was site-specifically conjugated with a deferoxamine (DFO) chelator and labelled under mild conditions (room temperature and neutral pH) with a positron-emitting radionuclide 89Zr. The 89Zr-DFO-ZEGFR:2377 tracer demonstrated specific high affinity (160±60 pM) binding to EGFR-expressing A431 epidermoid carcinoma cell line. In mice bearing A431 xenografts, 89Zr-DFO-ZEGFR:2377 demonstrated specific uptake in tumours and EGFR-expressing tissues. The tracer provided tumour uptake of 2.6±0.5% ID/g and tumour-to-blood ratio of 3.7±0.6 at 24 h after injection. 89Zr-DFO-ZEGFR:2377 provides higher tumour-to-organ ratios than anti-EGFR antibody 89Zr-DFO-cetuximab at 48 h after injection. EGFR-expressing tumours were clearly visualized by microPET using 89Zr-DFO-ZEGFR:2377 at both 3 and 24 h after injection. In conclusion, 89Zr-DFO-ZEGFR:2377 is a potential probe for PET imaging of EGFR-expression in vivo.
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Abstract
UNLABELLED Affibody molecules constitute a new class of probes for radionuclide tumor targeting. The small size of Affibody molecules is favorable for rapid localization in tumors and clearance from circulation. However, high renal reabsorption of Affibody molecules prevents the use of residualizing radiometals, including several promising low-energy β- and α-emitters, for radionuclide therapy. We tested a hypothesis that Affibody-based pretargeting mediated by a bioorthogonal interaction between trans-cyclooctene (TCO) and tetrazine would provide higher accumulation of radiometals in tumor xenografts than in the kidneys. METHODS TCO was conjugated to the anti-human epidermal growth factor receptor 2 (HER2) Affibody molecule Z2395. DOTA-tetrazine was labeled with (111)In and (177)Lu. In vitro pretargeting was studied in HER2-expressing SKOV-3 and BT474 cell lines. In vivo studies were performed on BALB/C nu/nu mice bearing SKOV-3 xenografts. RESULTS (125)I-Z2395-TCO bound specifically to HER2-expressing cells in vitro with an affinity of 45 ± 16 pM. (111)In-tetrazine bound specifically and selectively to Z2395-TCO pretreated cells. In vivo studies demonstrated HER2-specific (125)I-Z2395-TCO accumulation in xenografts. TCO-mediated (111)In-tetrazine localization was shown in tumors, when the radiolabeled tracer was injected 4 h after an injection of Z2395-TCO. At 1 h after injection, the tumor uptake of (111)In-tetrazine and (177)Lu-tetrazine was approximately 2-fold higher than the renal uptake. Pretargeting provided more than a 56-fold reduction of renal uptake of (111)In in comparison with direct targeting. CONCLUSION The feasibility of Affibody-based bioorthogonal chemistry-mediated pretargeting was demonstrated. The use of pretargeting provides a substantial reduction of radiometal accumulation in kidneys, creating preconditions for palliative radionuclide therapy.
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Affibody-mediated PET imaging of HER3 expression in malignant tumours. Sci Rep 2015; 5:15226. [PMID: 26477646 PMCID: PMC4609989 DOI: 10.1038/srep15226] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Accepted: 09/17/2015] [Indexed: 01/02/2023] Open
Abstract
Human epidermal growth factor receptor 3 (HER3) is involved in the progression of various cancers and in resistance to therapies targeting the HER family. In vivo imaging of HER3 expression would enable patient stratification for anti-HER3 immunotherapy. Key challenges with HER3-targeting are the relatively low expression in HER3-positive tumours and HER3 expression in normal tissues. The use of positron-emission tomography (PET) provides advantages of high resolution, sensitivity and quantification accuracy compared to SPECT. Affibody molecules, imaging probes based on a non-immunoglobulin scaffold, provide high imaging contrast shortly after injection. The aim of this study was to evaluate feasibility of PET imaging of HER3 expression using (68)Ga-labeled affibody molecules. The anti-HER3 affibody molecule HEHEHE-Z08698-NOTA was successfully labelled with (68)Ga with high yield, purity and stability. The agent bound specifically to HER3-expressing cancer cells in vitro and in vivo. At 3 h pi, uptake of (68)Ga-HEHEHE-Z08698-NOTA was significantly higher in xenografts with high HER3 expression (BT474, BxPC-3) than in xenografts with low HER3 expression (A431). In xenografts with high expression, tumour-to-blood ratios were >20, tumour-to-muscle >15, and tumour-to-bone >7. HER3-positive xenografts were visualised using microPET 3 h pi. In conclusion, PET imaging of HER3 expression is feasible using (68)Ga-HEHEHE-Z08698-NOTA shortly after administration.
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The effect of macrocyclic chelators on the targeting properties of the 68 Ga-labeled gastrin releasing peptide receptor antagonist PEG 2 -RM26. Nucl Med Biol 2015; 42:446-454. [DOI: 10.1016/j.nucmedbio.2014.12.009] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 11/26/2014] [Accepted: 12/07/2014] [Indexed: 11/30/2022]
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Evaluation of 99mTc-Z IGF1R:4551-GGGC affibody molecule, a new probe for imaging of insulin-like growth factor type 1 receptor expression. Amino Acids 2014; 47:303-15. [PMID: 25425114 PMCID: PMC4302241 DOI: 10.1007/s00726-014-1859-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Accepted: 10/18/2014] [Indexed: 11/30/2022]
Abstract
Overexpression of insulin-like growth factor-1 receptor (IGF-1R) in several cancers is associated with resistance to therapy. Radionuclide molecular imaging of IGF-1R expression in tumors may help in selecting the patients that will potentially respond to IGF-1R-targeted therapy. Affibody molecules are small (7 kDa) non-immunoglobulin-based scaffold proteins that are well-suited probes for radionuclide imaging. The aim of this study was the evaluation of an anti-IGF-1R affibody molecule labeled with technetium-99m using cysteine-containing peptide-based chelator GGGC at C-terminus. ZIGF1R:4551-GGGC was efficiently and stably labeled with technetium-99m (radiochemical yield 97 ± 3 %). 99mTc-ZIGF1R:4551-GGGC demonstrated specific binding to IGF-1R-expressing DU-145 (prostate cancer) and MCF-7 (breast cancer) cell lines and slow internalization in vitro. The tumor-targeting properties were studied in BALB/c nu/nu mice bearing DU-145 and MCF-7 xenografts. [99mTc(CO)3]+-(HE)3-ZIGF1R:4551 was used for comparison. The biodistribution study demonstrated high tumor-to-blood ratios (6.2 ± 0.9 and 6.9 ± 1.0, for DU-145 and MCF-7, respectively, at 4 h after injection). Renal radioactivity concentration was 16-fold lower for 99mTc-ZIGF1R:4551-GGGC than for [99mTc(CO)3]+-(HE)3-ZIGF1R:4551 at 4 h after injection. However, the liver uptake of 99mTc-ZIGF1R:4551-GGGC was 1.2- to 2-fold higher in comparison with [99mTc(CO)3]+-(HE)3-ZIGF1R:4551. A possible reason for the elevated hepatic uptake of 99mTc-ZIGF1R:4551-GGGC is a high lipophilicity of amino acids in the binding site of ZIGF1R:4551, which is not compensated in 99mTc-ZIGF1R:4551-GGGC. In conclusion, 99mTc-ZIGF1R:4551-GGGC can visualize the IGF-1R expression in human tumor xenografts and provides low retention of radioactivity in kidneys. Further development of this imaging agent should include molecular design aimed at reducing the hepatic uptake.
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The effect of mini-PEG-based spacer length on binding and pharmacokinetic properties of a 68Ga-labeled NOTA-conjugated antagonistic analog of bombesin. Molecules 2014; 19:10455-72. [PMID: 25036155 PMCID: PMC6270800 DOI: 10.3390/molecules190710455] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 07/10/2014] [Accepted: 07/11/2014] [Indexed: 11/25/2022] Open
Abstract
The overexpression of gastrin-releasing peptide receptor (GRPR) in cancer can be used for peptide-receptor mediated radionuclide imaging and therapy. We have previously shown that an antagonist analog of bombesin RM26 conjugated to 1,4,7-triazacyclononane-N,N',N''-triacetic acid (NOTA) via a diethyleneglycol (PEG2) spacer (NOTA-PEG2-RM26) and labeled with 68Ga can be used for imaging of GRPR-expressing tumors. In this study, we evaluated if a variation of mini-PEG spacer length can be used for optimization of targeting properties of the NOTA-conjugated RM26. A series of analogs with different PEG-length (n = 2, 3, 4, 6) was synthesized, radiolabeled and evaluated in vitro and in vivo. The IC50 values of natGa-NOTA-PEGn-RM26 (n = 2, 3, 4, 6) were 3.1 ± 0.2, 3.9 ± 0.3, 5.4 ± 0.4 and 5.8 ± 0.3 nM, respectively. In normal mice all conjugates demonstrated similar biodistribution pattern, however 68Ga-NOTA-PEG3-RM26 showed lower liver uptake. Biodistribution of 68Ga-NOTA-PEG3-RM26 was evaluated in nude mice bearing PC-3 (prostate cancer) and BT-474 (breast cancer) xenografts. High uptake in tumors (4.6 ± 0.6%ID/g and 2.8 ± 0.4%ID/g for PC-3 and BT-474 xenografts, respectively) and high tumor-to-background ratios (tumor/blood of 44 ± 12 and 42 ± 5 for PC-3 and BT-474 xenografts, respectively) were found already at 2 h p.i. of 68Ga-NOTA-PEG3-RM26. Results of this study suggest that variation in the length of the PEG spacer can be used for optimization of targeting properties of peptide-chelator conjugates. However, the influence of the mini-PEG length on biodistribution is minor when di-, tri-, tetra- and hexaethylene glycol are compared.
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