RESUMEN
Designed ankyrin repeat protein (DARPin) G3 is an engineered scaffold protein. This small (14.5 kDa) targeting protein binds with high affinity to human epidermal growth factor receptor 2 (HER2). HER2 is overexpressed in several cancers. The use of the DARPin G3 for radionuclide therapy is complicated by its high renal reabsorption after clearance via the glomeruli. We tested the hypothesis that a fusion of the DARPin G3 with an albumin-binding domain (ABD) would prevent rapid renal excretion and high renal reabsorption resulting in better tumour targeting. Two fusion proteins were produced, one with the ABD at the C-terminus (G3-ABD) and another at the N-terminus (ABD-G3). Both variants were labelled with 177Lu. The binding properties of the novel constructs were evaluated in vitro and their biodistribution was compared in mice with implanted human HER2-expressing tumours. Fusion with the ABD increased the retention time of both constructs in blood compared with the non-ABD-fused control. The effect of fusion with the ABD depended strongly on the order of the domains in the constructs, resulting in appreciably better targeting properties of [177Lu]Lu-G3-ABD. Our data suggest that the order of domains is critical for the design of targeting constructs based on scaffold proteins.
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Receptor ErbB-2 , Animales , Femenino , Humanos , Ratones , Albúminas/metabolismo , Repetición de Anquirina , Línea Celular Tumoral , Lutecio , Unión Proteica , Dominios Proteicos , Radioisótopos , Radiofármacos/metabolismo , Receptor ErbB-2/antagonistas & inhibidores , Proteínas Recombinantes de Fusión/metabolismo , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/química , Distribución Tisular , Terapia Molecular DirigidaRESUMEN
The feasibility of targeted imaging and therapy using radiolabeled albuminbinding domainderived affinity proteins (ADAPTs) has been demonstrated. However, high renal uptake of radioactivity limits the maximum tolerated dose. Successful reduction of renal retention of radiolabeled Fab fragments has been demonstrated by incorporating a cleavable linker between the targeting agent and the radiometal chelator. The present study investigated if the introduction of a glycineleucineglycinelysine (GLGK)linker would reduce the kidney uptake of radiolabeled ADAPT6 and also compared it with the nonresidualizing [125I]I[(4hydroxyphenyl)ethyl]maleimide ([125I]IHPEM) labeling strategy. GLGK was sitespecifically coupled to human epidermal growth factor receptor 2 (HER2)targeting ADAPT6. Conjugates without the cleavable linker were used as controls and all constructs were labeled with lutetium177 (177Lu). [125I]IHPEM was coupled to ADAPT6 at the Cterminus. Biodistribution of all constructs was evaluated in NMRI mice 4 h after injection. Specific binding to HER2expressing cells in vitro was demonstrated for all constructs. No significant difference in kidney uptake was observed between the [177Lu]Lu2,2',2",2"'(1,4,7,10tetraazacyclododecane1,4,7,10tetrayl)tetraacetic acidGLGKconjugates and the controls. The renal activity of [125I]IHPEMADAPT6 was significantly lower compared with all other constructs. In conclusion, the incorporation of the cleavable GLGKlinker did not result in lower renal retention. Therefore, the present study emphasized that, in order to achieve a reduction of renal retention, alternative molecular design strategies may be required for different targeting agents.
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Proteínas Portadoras , Fabaceae , Humanos , Animales , Ratones , Glicina , Leucina , Lisina , Distribución Tisular , AlbúminasRESUMEN
Semaglutide is the first oral glucagon-like peptide-1 (GLP-1) analog commercially available for the treatment of type 2 diabetes. In this work, semaglutide was incorporated into poly(lactic-co-glycolic acid)-poly(ethylene glycol) (PLGA-PEG) nanoparticles (NPs) to improve its delivery across the intestinal barrier. The nanocarriers were surface-decorated with either a peptide or an affibody that target the human neonatal Fc receptor (hFcRn), located on the luminal cell surface of the enterocytes. Both ligands were successfully conjugated with the PLGA-PEG via maleimide-thiol chemistry and thereafter, the functionalized polymers were used to produce semaglutide-loaded NPs. Monodisperse NPs with an average size of 170 nm, neutral surface charge and 3% of semaglutide loading were obtained. Both FcRn-targeted NPs exhibited improved interaction and association with Caco-2 cells (cells that endogenously express the hFcRn), compared to non-targeted NPs. Additionally, the uptake of FcRn-targeted NPs was also observed to occur in human intestinal organoids (HIOs) expressing hFcRn through microinjection into the lumen of HIOs, resulting in potential increase of semaglutide permeability for both ligand-functionalized nanocarriers. Herein, our study demonstrates valuable data and insights that the FcRn-targeted NPs has the capacity to promote intestinal absorption of therapeutic peptides.
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Diabetes Mellitus Tipo 2 , Péptidos Similares al Glucagón , Lactatos , Nanopartículas , Polietilenglicoles , Recién Nacido , Humanos , Células CACO-2 , Péptidos , Receptores FcRESUMEN
Non-invasive radionuclide imaging of human epidermal growth factor receptor type 2 (HER2) expression in breast, gastroesophageal, and ovarian cancers may stratify patients for treatment using HER2-targeted therapeutics. Designed ankyrin repeat proteins (DARPins) are a promising type of targeting probe for radionuclide imaging. In clinical studies, the DARPin [99mTc]Tc-(HE)3-G3 labeled using a peptide-based chelator His-Glu-His-Glu-His-Glu ((HE)3), provided clear imaging of HER2 expressing breast cancer 2-4 h after injection. The goal of this study was to evaluate if the use of cysteine-containing peptide-based chelators Glu-Glu-Glu-Cys (E3C), Gly-Gly-Gly-Cys (G3C), and Gly-Gly-Gly-Ser-Cys connected via a (Gly-Gly-Gly-Ser)3-linker (designated as G3-(G3S)3C) would further improve the contrast of imaging using 99mTc-labeled derivatives of G3. The labeling of the new variants of G3 provided a radiochemical yield of over 95%. Labeled G3 variants bound specifically to human HER2-expressing cancer cell lines with affinities in the range of 1.9-5 nM. Biodistribution of [99mTc]Tc-G3-G3C, [99mTc]Tc-G3-(G3S)3C, and [99mTc]Tc-G3-E3C in mice was compared with the biodistribution of [99mTc]Tc-(HE)3-G3. It was found that the novel variants provide specific accumulation in HER2-expressing human xenografts and enable discrimination between tumors with high and low HER2 expression. However, [99mTc]Tc-(HE)3-G3 provided better contrast between tumors and the most frequent metastatic sites of HER2-expressing cancers and is therefore more suitable for clinical applications.
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Neoplasias de la Mama , Proteínas de Repetición de Anquirina Diseñadas , Femenino , Humanos , Animales , Ratones , Quelantes , Distribución Tisular , Línea Celular Tumoral , Cintigrafía , Péptidos , Neoplasias de la Mama/diagnóstico por imagenRESUMEN
Overexpression of the human epidermal growth factor receptor 2 (HER2) in breast and gastric cancer is exploited for targeted therapy using monoclonal antibodies and antibody-drug conjugates. Small engineered scaffold proteins, such as the albumin binding domain (ABD) derived affinity proteins (ADAPTs), are a promising new format of targeting probes for development of drug conjugates with well-defined structure and tunable pharmacokinetics. Radiolabeled ADAPT6 has shown excellent tumor-targeting properties in clinical trials. Recently, we developed a drug conjugate based on the HER2-targeting ADAPT6 fused to an albumin binding domain (ABD) for increased bioavailability and conjugated to DM1 for cytotoxic action, designated as ADAPT6-ABD-mcDM1. In this study, we investigated the therapeutic efficacy of this conjugate in mice bearing HER2-expressing SKOV3 ovarian cancer xenografts. A secondary aim was to evaluate several formats of imaging probes for visualization of HER2 expression in tumors. Administration of ADAPT6-ABD-mcDM1 provided a significant delay of tumor growth and increased the median survival of the mice, in comparison with both a non-targeting homologous construct (ADAPTNeg-ABD-mcDM1) and the vehicle-treated groups, without inducing toxicity to liver or kidneys. Moreover, the evaluation of imaging probes showed that small scaffold proteins, such as 99mTc(CO)3-ADAPT6 or the affibody molecule 99mTc-ZHER2:41071, are well suited as diagnostic companions for potential stratification of patients for ADAPT6-ABD-mcDM1-based therapy.
RESUMEN
Albumin binding domain derived affinity proteins (ADAPTs) are a class of small and folded engineered scaffold proteins that holds great promise for targeting cancer tumors. Here, we have extended the in vivo half-life of an ADAPT, targeting the human epidermal growth factor receptor 2 (HER2) by fusion with an albumin binding domain (ABD), and armed it with the highly cytotoxic payload mertansine (DM1) for an investigation of its properties in vitro and in vivo. The resulting drug conjugate, ADAPT6-ABD-mcDM1, retained binding to its intended targets, namely HER2 and serum albumins. Further, it was able to specifically bind to cells with high HER2 expression, get internalized, and showed potent toxicity, with IC50 values ranging from 5 to 80 nM. Conversely, no toxic effect was found for cells with low HER2 expression. In vivo, ADAPT6-ABD-mcDM1, radiolabeled with 99mTc, was characterized by low uptake in most normal organs, and the main excretion route was shown to be through the kidneys. The tumor uptake was 5.5% ID/g after 24 h, which was higher than the uptake in all normal organs at this time point except for the kidneys. The uptake in the tumors was blockable by pre-injection of an excess of the monoclonal antibody trastuzumab (having an overlapping epitope on the HER2 receptor). In conclusion, half-life extended drug conjugates based on the ADAPT platform of affinity proteins holds promise for further development towards targeted cancer therapy.
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The epithelial cell adhesion molecule (EpCAM) is intensively overexpressed in 40-60% of prostate cancer (PCa) cases and can be used as a target for the delivery of drugs and toxins. The designed ankyrin repeat protein (DARPin) Ec1 has a high affinity to EpCAM (68 pM) and a small size (18 kDa). Radiolabeled Ec1 might be used as a companion diagnostic for the selection of PCa patients for therapy. The study aimed to investigate the influence of radiolabel position (N- or C-terminal) and composition on the targeting and imaging properties of Ec1. Two variants, having an N- or C-terminal cysteine, were produced, site-specifically conjugated to a DOTA chelator and labeled with cobalt-57, gallium-68 or indium-111. Site-specific radioiodination was performed using ((4-hydroxyphenyl)-ethyl)maleimide (HPEM). Biodistribution of eight radiolabeled Ec1-probes was measured in nude mice bearing PCa DU145 xenografts. In all cases, positioning of a label at the C-terminus provided the best tumor-to-organ ratios. The non-residualizing [125I]I-HPEM label provided the highest tumor-to-muscle and tumor-to-bone ratios and is more suitable for EpCAM imaging in early-stage PCa. Among the radiometals, indium-111 provided the highest tumor-to-blood, tumor-to-lung and tumor-to-liver ratios and could be used at late-stage PCa. In conclusion, label position and composition are important for the DARPin Ec1.
RESUMEN
Epidermal growth factor receptor (EGFR) is overexpressed in many malignancies. EGFR-targeted therapy extends survival of patients with disseminated cancers. Radionuclide molecular imaging of EGFR expression would make EGFR-directed treatment more personalized and therefore more efficient. A previous study demonstrated that affibody molecule [68Ga]Ga-DFO-ZEGFR:2377 permits specific positron-emission tomography (PET) imaging of EGFR expression in xenografts at 3 h after injection. We anticipated that imaging at 24 h after injection would provide higher contrast, but this is prevented by the short half-life of 68Ga (67.6 min). Here, we therefore tested the hypothesis that the use of the non-conventional long-lived positron emitter 66Ga (T1/2 = 9.49 h, ß+ = 56.5%) would permit imaging with higher contrast. 66Ga was produced by the 66Zn(p,n)66Ga nuclear reaction and DFO-ZEGFR:2377 was efficiently labelled with 66Ga with preserved binding specificity in vitro and in vivo. At 24 h after injection, [66Ga]Ga-DFO-ZEGFR:2377 provided 3.9-fold higher tumor-to-blood ratio and 2.3-fold higher tumor-to-liver ratio than [68Ga]Ga-DFO-ZEGFR:2377 at 3 h after injection. At the same time point, [66Ga]Ga-DFO-ZEGFR:2377 provided 1.8-fold higher tumor-to-blood ratio, 3-fold higher tumor-to-liver ratio, 1.9-fold higher tumor-to-muscle ratio and 2.3-fold higher tumor-to-bone ratio than [89Zr]Zr-DFO-ZEGFR:2377. Biodistribution data were confirmed by whole body PET combined with magnetic resonance imaging (PET/MRI). The use of the positron emitter 66Ga for labelling of DFO-ZEGFR:2377 permits PET imaging of EGFR expression at 24 h after injection and improves imaging contrast.
RESUMEN
Radionuclide molecular imaging of human epidermal growth factor receptor type 2 (HER2) expression may help to stratify breast and gastroesophageal cancer patients for HER2-targeting therapies. Albumin-binding domain-derived affinity proteins (ADAPTs) are a new type of small (46-59 amino acids) protein useful as probes for molecular imaging. The aim of this first-in-humans study was to evaluate the biodistribution, dosimetry, and safety of the HER2-specific 99mTc-ADAPT6. Methods: Twenty-nine patients with primary breast cancer were included. In 22 patients with HER2-positive (n = 11) or HER2-negative (n = 11) histopathology, an intravenous injection of 385 ± 125 MBq of 99mTc-ADAPT6 was performed, randomized to an injected protein mass of either 500 µg (n = 11) or 1,000 µg (n = 11). Planar scintigraphy followed by SPECT imaging was performed after 2, 4, 6, and 24 h. An additional cohort (n = 7) was injected with 165 ± 29 MBq (injected protein mass, 250 µg), and imaging was performed after 2 h only. Results: Injections of 99mTc-ADAPT6 were well tolerated at all mass levels and not associated with adverse effects. 99mTc-ADAPT6 cleared rapidly from the blood and most other tissues. The normal organs with the highest accumulation were the kidney, liver, and lung. Effective doses were 0.009 ± 0.002 and 0.010 ± 0.003 mSv/MBq for injected protein masses of 500 and 1,000 µg, respectively. Injection of 500 µg resulted in excellent discrimination between HER2-positive and HER2-negative tumors as early as 2 h after injection (tumor-to-contralateral breast ratio, 37 ± 19 vs. 5 ± 2; P < 0.01). The tumor-to-contralateral breast ratios for HER2-positive tumors were significantly (P < 0.05) higher for an injected mass of 500 µg than for either 250 or 1,000 µg. Conclusion: Injections of 99mTc-ADAPT6 are safe and associated with low absorbed and effective doses. A protein dose of 500 µg is preferable for discrimination between tumors with high and low expression of HER2. Further studies are justified to evaluate whether 99mTc-ADAPT6 can be used as an imaging probe to stratify patients for HER2-targeting therapy in areas where PET imaging is not readily available.
Asunto(s)
Neoplasias de la Mama/diagnóstico por imagen , Neoplasias de la Mama/metabolismo , Regulación Neoplásica de la Expresión Génica , Receptor ErbB-2/metabolismo , Tomografía Computarizada de Emisión de Fotón Único , Adulto , Femenino , Humanos , Persona de Mediana Edad , Radiometría , Seguridad , Tecnecio/análisisRESUMEN
Molecular recognition in targeted therapeutics is typically based on immunoglobulins. Development of engineered scaffold proteins (ESPs) has provided additional opportunities for the development of targeted therapies. ESPs offer inexpensive production in prokaryotic hosts, high stability and convenient approaches to modify their biodistribution. In this study, we demonstrated successful modification of the biodistribution of an ESP known as ADAPT (Albumin-binding domain Derived Affinity ProTein). ADAPTs are selected from a library based on the scaffold of ABD (Albumin Binding Domain) of protein G. A particular ADAPT, the ADAPT6, binds to human epidermal growth factor receptor type 2 (HER2) with high affinity. Preclinical and early clinical studies have demonstrated that radiolabeled ADAPT6 can image HER2-expression in tumors with high contrast. However, its rapid glomerular filtration and high renal reabsorption have prevented its use in radionuclide therapy. To modify the biodistribution, ADAPT6 was genetically fused to an ABD. The non-covalent binding to the host's albumin resulted in a 14-fold reduction of renal uptake and appreciable increase of tumor uptake for the best variant, 177Lu-DOTA-ADAPT6-ABD035. Experimental therapy in mice bearing HER2-expressing xenografts demonstrated more than two-fold increase of median survival even after a single injection of 18 MBq 177Lu-DOTA-ADAPT6-ABD035. Thus, a fusion with ABD and optimization of the molecular design provides ADAPT derivatives with attractive targeting properties for radionuclide therapy.
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Proteínas , Radioterapia , Receptor ErbB-2 , Albúminas , Animales , Línea Celular Tumoral , Ratones , Proteínas/metabolismo , Radioisótopos , Receptor ErbB-2/metabolismo , Distribución TisularRESUMEN
Albumin binding domain-Derived Affinity ProTeins (ADAPTs) are small (5 kDa) engineered scaffold proteins that are promising targeting agents for radionuclide-based imaging. A recent clinical study has demonstrated that radiolabeled ADAPTs can efficiently visualize human epidermal growth factor receptor 2 (HER2) expression in breast cancer using SPECT imaging. However, the use of ADAPTs directly labeled with radiometals for targeted radionuclide therapy is limited by their high reabsorption and prolonged retention of activity in kidneys. In this study, we investigated whether a co-injection of lysine or gelofusin, commonly used for reduction of renal uptake of radiolabeled peptides in clinics, would reduce the renal uptake of [99mTc]Tc(CO)3-ADAPT6 in NMRI mice. In order to better understand the mechanism behind the reabsorption of [99mTc]Tc(CO)3-ADAPT6, we included several compounds that act on various parts of the reabsorption system in kidneys. Administration of gelofusine, lysine, probenecid, furosemide, mannitol, or colchicine did not change the uptake of [99mTc]Tc(CO)3-ADAPT6 in kidneys. Sodium maleate reduced the uptake of [99mTc]Tc(CO)3-ADAPT6 to ca. 25% of the uptake in the control, a high dose of fructose (50 mmol/kg) reduced the uptake by ca. two-fold. However, a lower dose (20 mmol/kg) had no effect. These results indicate that common clinical strategies are not effective for reduction of kidney uptake of [99mTc]Tc(CO)3-ADAPT6 and that other strategies for reduction of activity uptake or retention in kidneys should be investigated for ADAPT6.
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Riñón/metabolismo , Proteínas/farmacología , Radiofármacos/farmacología , Animales , Autorradiografía , Cromatografía Líquida de Alta Presión , Cromatografía de Fase Inversa , Femenino , Ratones , Proteínas/administración & dosificación , Proteínas/metabolismo , Radiofármacos/administración & dosificación , Distribución Tisular/efectos de los fármacosRESUMEN
Efficient treatment of disseminated triple-negative breast cancer (TNBC) remains an unmet clinical need. The epithelial cell adhesion molecule (EpCAM) is often overexpressed on the surface of TNBC cells, which makes EpCAM a potential therapeutic target. Radionuclide molecular imaging of EpCAM expression might permit selection of patients for EpCAM-targeting therapies. In this study, we evaluated a scaffold protein, designed ankyrin repeat protein (DARPin) Ec1, for imaging of EpCAM in TNBC. DARPin Ec1 was labeled with a non-residualizing [125I]I-para-iodobenzoate (PIB) label and a residualizing [99mTc]Tc(CO)3 label. Both imaging probes retained high binding specificity and affinity to EpCAM-expressing MDA-MB-468 TNBC cells after labeling. Internalization studies showed that Ec1 was retained on the surface of MDA-MB-468 cells to a high degree up to 24 h. Biodistribution in Balb/c nu/nu mice bearing MDA-MB-468 xenografts demonstrated specific uptake of both [125I]I-PIB-Ec1 and [99mTc]Tc(CO)3-Ec1 in TNBC tumors. [125I]I-PIB-Ec1 had appreciably lower uptake in normal organs compared with [99mTc]Tc(CO)3-Ec1, which resulted in significantly (p < 0.05) higher tumor-to-organ ratios. The biodistribution data were confirmed by micro-Single-Photon Emission Computed Tomography/Computed Tomography (microSPECT/CT) imaging. In conclusion, an indirectly radioiodinated Ec1 is the preferable probe for imaging of EpCAM in TNBC.
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Molécula de Adhesión Celular Epitelial/análisis , Imagen Molecular/métodos , Sondas Moleculares/química , Neoplasias de la Mama Triple Negativas/metabolismo , Animales , Línea Celular Tumoral , Molécula de Adhesión Celular Epitelial/metabolismo , Femenino , Humanos , Radioisótopos de Yodo/química , Radioisótopos de Yodo/farmacocinética , Yodobenzoatos/química , Ratones Endogámicos BALB C , Sondas Moleculares/farmacocinética , Proteínas Musculares/química , Proteínas Nucleares/química , Radiofármacos/química , Radiofármacos/farmacocinética , Tecnecio , Distribución Tisular , Tomografía Computarizada de Emisión de Fotón Único/métodos , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Affibody molecules are the most studied class of engineered scaffold proteins (ESPs) in radionuclide molecular imaging. Attempts to use affibody molecules directly labelled with radiometals for targeted radionuclide therapy were hampered by the high uptake and retention of radioactivity in kidneys. Several promising strategies have been implemented to circumvent this problem. Here, we investigated whether a pharmacological approach targeting different components of the reabsorption system could be used to lower the uptake of [99mTc]Tc-ZHER:2395 affibody molecule in kidneys. Pre-injection of probenecid, furosemide, mannitol or colchicine had no influence on activity uptake in kidneys compared to the control group. Mice pre-injected with maleate and fructose had 33% and 51% reduction in the kidney-associated activity, respectively, compared to the control group. Autoradiography images showed that the accumulation of activity after [99mTc]Tc-ZHER2:2395 injection was in the renal cortex and that both maleate and fructose could significantly reduce it. Results from this study demonstrate that pharmacological intervention with maleate and fructose was effective in reducing the kidney uptake of affibody molecules. A presumable mechanism is the disruption of ATP-mediated cellular uptake and endocytosis processes of affibody molecules by tubular cells.
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Quelantes/química , Fructosa/farmacología , Riñón/metabolismo , Maleatos/farmacología , Compuestos de Organotecnecio/farmacocinética , Radiofármacos/farmacocinética , Proteínas Recombinantes de Fusión/farmacocinética , Animales , Inhibidores Enzimáticos/farmacología , Femenino , Riñón/diagnóstico por imagen , Riñón/efectos de los fármacos , Ratones , Imagen Molecular , Compuestos de Organotecnecio/química , Cintigrafía , Radiofármacos/química , Proteínas Recombinantes de Fusión/química , Edulcorantes/farmacología , Distribución TisularRESUMEN
The use of radiolabelled antibodies was proposed in 1970s for staging of malignant tumours. Intensive research established chemistry for radiolabelling of proteins and understanding of factors determining biodistribution and targeting properties. The use of radioimmunodetection for staging of cancer was not established as common practice due to approval and widespread use of [18F]-FDG, which provided a more general diagnostic use than antibodies or their fragments. Expanded application of antibody-based therapeutics renewed the interest in radiolabelled antibodies. RadioimmunoPET emerged as a powerful tool for evaluation of pharmacokinetics of and target engagement by biotherapeutics. In addition to monoclonal antibodies, new radiolabelled engineered proteins have recently appeared, offering high-contrast imaging of expression of therapeutic molecular targets in tumours shortly after injection. This creates preconditions for noninvasive determination of a target expression level and stratification of patients for targeted therapies. Radiolabelled proteins hold great promise to play an important role in development and implementation of personalised targeted treatment of malignant tumours. This article provides an overview of biodistribution and tumour-seeking features of major classes of targeting proteins currently utilized for molecular imaging. Such information might be useful for researchers entering the field of the protein-based radionuclide molecular imaging.
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Epithelial cell adhesion molecule (EpCAM) is overexpressed in 55%-75% of ovarian carcinomas (OC). EpCAM might be used as a target for a treatment of disseminated OC. Designed ankyrin repeats protein (DARPin) Ec1 is a small (18 kDa) protein, which binds to EpCAM with subnanomolar affinity. We tested a hypothesis that Ec1 labeled with a non-residualizing label might serve as a companion imaging diagnostic for stratification of patients for EpCAM-targeting therapy. Ec1 was labeled with 125I using N-succinimidyl-para-iodobenzoate. Binding affinity, specificity, and cellular processing of [125I]I-PIB-Ec1 were evaluated using SKOV-3 and OVCAR-3 ovarian carcinoma cell lines. Biodistribution and tumor-targeting properties of [125I]I-PIB-Ec1 were studied in Balb/c nu/nu mice bearing SKOV-3 and OVCAR-3 xenografts. EpCAM-negative Ramos lymphoma xenografts served as specificity control. Binding of [125I]I-PIB-Ec1 to ovarian carcinoma cell lines was highly specific and had affinity in picomolar range. Slow internalization of [125I]I-PIB-Ec1 by OC cells confirmed utility of non-residualizing label for in vivo imaging. [125I]I-PIB-Ec1 provided 6 h after injection tumor-to-blood ratios of 30 ± 11 and 48 ± 12 for OVCAR-3 and SKOV-3 xenografts, respectively, and high contrast to other organs. Tumor targeting was highly specific. Saturation of tumor uptake at a high dose of Ec1 in SKOV-3 model provided a rationale for dose selection in further studies using therapeutic conjugates of Ec1 for targeted therapy. In conclusion, [125I]I-PIB-Ec1 is a promising agent for visualizing EpCAM expression in OC.
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Molécula de Adhesión Celular Epitelial/metabolismo , Radioisótopos de Yodo/química , Imagen Molecular/métodos , Neoplasias Ováricas/diagnóstico por imagen , Proteínas Recombinantes de Fusión/administración & dosificación , Animales , Línea Celular Tumoral , Estudios de Factibilidad , Femenino , Humanos , Ratones , Ratones Desnudos , Terapia Molecular Dirigida , Trasplante de Neoplasias , Neoplasias Ováricas/metabolismo , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/farmacocinética , Tomografía Computarizada por Tomografía Computarizada de Emisión de Fotón Único , Distribución TisularRESUMEN
The human epidermal growth factor receptor 2 (HER2) is a clinically validated target for cancer therapy, and targeted therapies are often used in regimens for patients with a high HER2 expression level. Despite the success of current drugs, a number of patients succumb to their disease, which motivates development of novel drugs with other modes of action. We have previously shown that an albumin binding domain-derived affinity protein with specific affinity for HER2, ADAPT6, can be used to deliver the highly cytotoxic protein domain PE25, a derivative of Pseudomonas exotoxin A, to HER2 overexpressing malignant cells, leading to potent and specific cell killing. In this study we expanded the investigation for an optimal targeting domain and constructed two fusion toxins where a HER2-binding affibody molecule, ZHER2:2891, or the dual-HER2-binding hybrid ZHER2:2891-ADAPT6 were used for cancer cell targeting. We found that both targeting domains conferred strong binding to HER2; both to the purified extracellular domain and to the HER2 overexpressing cell line SKOV3. This resulted in fusion toxins with high cytotoxic potency toward cell lines with high expression levels of HER2, with EC50 values between 10 and 100 pM. For extension of the plasma half-life, an albumin binding domain was also included. Intravenous injection of the fusion toxins into mice showed a profound influence of the targeting domain on biodistribution. Compared to previous results, with ADAPT6 as targeting domain, ZHER2:2891 gave rise to further extension of the plasma half-life and also shifted the clearance route of the fusion toxin from the liver to the kidneys. Collectively, the results show that the targeting domain has a major impact on uptake of PE25-based fusion toxins in different organs. The results also show that PE25-based fusion toxins with high affinity to HER2 do not necessarily increase the cytotoxicity beyond a certain point in affinity. In conclusion, ZHER2:2891 has the most favorable characteristics as targeting domain for PE25.
RESUMEN
BACKGROUND: Designed ankyrin repeat proteins (DARPins) are small engineered scaffold proteins (14-18 kDa) that demonstrated promising tumor-targeting properties in preclinical studies. However, high renal accumulation of activity for DARPins labeled with residualizing labels is a limitation for targeted radionuclide therapy. A better understanding of the mechanisms behind the kidney uptake of DARPins could aid the development of strategies to reduce it. In this study, we have investigated whether the renal uptake of [99mTc]Tc(CO)3-G3 DARPin could be reduced by administration of compounds that act on various parts of the reabsorption system in the kidney. RESULTS: Co-injection of lysine or Gelofusine was not effective for the reduction of kidney uptake of [99mTc]Tc(CO)3-G3. Administration of sodium maleate before the injection of [99mTc]Tc(CO)3-G3 reduced the kidney-associated activity by 60.4 ± 10.3%, while administration of fructose reduced it by 46.9 ± 7.6% compared with the control. The decrease in the kidney uptake provided by sodium maleate was also observed for [99mTc]Tc(CO)3-9_29 DARPin. Preinjection of colchicine, probenecid, mannitol, or furosemide had no effect on the kidney uptake of [99mTc]Tc(CO)3-G3. Kidney autoradiography showed mainly cortical accumulation of activity for all studied groups. CONCLUSION: Common clinical strategies were not effective for the reduction of kidney uptake of [99mTc]Tc(CO)3-G3. Both fructose and maleate lower the cellular ATP level in the proximal tubule cells and their reduction of the kidney reuptake indicates the involvement of an ATP-driven uptake mechanism. The decrease provided by maleate for both G3 and 9_29 DARPins indicates that their uptake proceeds through a mechanism independent of DARPin structure and binding site composition.
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Radionuclide-based imaging of molecular therapeutic targets might facilitate stratifying patients for specific biotherapeutics. New type of imaging probes, based on designed ankyrin repeat proteins (DARPins), have demonstrated excellent contrast of imaging of human epidermal growth factor type 2 (HER2) expression in preclinical models. We hypothesized that labeling approaches, which result in lipophilic radiometabolites (non-residualizing labels), would provide the best imaging contrast for DARPins that internalize slowly after binding to cancer cells. The hypothesis was tested using DARPin Ec1 that binds to epithelial cell adhesion molecule (EpCAM). EpCAM is a promising therapeutic target. Ec1 was labeled with 125I using two methods to obtain the non-residualizing labels, while residualizing labels were obtained by labeling it with 99mTc. All labeled Ec1 variants preserved target specificity and picomolar binding affinity to EpCAM-expressing pancreatic adenocarcinoma BxPC-3 cells. In murine models, all the variants provided similar tumor uptake. However, 125I-PIB-H6-Ec1 had noticeably lower retention in normal tissues, which provided appreciably higher tumor-to-organ ratios. Furthermore, 125I-PIB-H6-Ec1 demonstrated the highest imaging contrast in preclinical models than any other EpCAM-imaging agent tested so far. In conclusion, DARPin Ec1 in combination with a non-residualizing label is a promising probe for imaging EpCAM expression a few hours after injection.
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Adenocarcinoma/diagnóstico por imagen , Biomarcadores de Tumor/genética , Molécula de Adhesión Celular Epitelial/genética , Neoplasias Pancreáticas/diagnóstico por imagen , Ingeniería de Proteínas/métodos , Receptor ErbB-2/genética , Adenocarcinoma/genética , Adenocarcinoma/metabolismo , Adenocarcinoma/patología , Animales , Disponibilidad Biológica , Biomarcadores de Tumor/metabolismo , Endocitosis , Molécula de Adhesión Celular Epitelial/metabolismo , Expresión Génica , Células HT29 , Xenoinjertos , Humanos , Radioisótopos de Yodo , Ratones , Ratones Endogámicos BALB C , Ratones Desnudos , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/metabolismo , Neoplasias Pancreáticas/patología , Tomografía de Emisión de Positrones , Unión Proteica , Receptor ErbB-2/metabolismo , Distribución Tisular , Tomografía Computarizada de Emisión de Fotón ÚnicoRESUMEN
Hypoxia-induced carbonic anhydrase IX (CAIX) expression is a prognostic marker in solid tumors. In recent years many radiotracers have been developed, but a fair comparison of these compounds is not possible because of the diversity in tumor models and other experimental parameters. In this study we performed a direct in vivo comparison of three promising CAIX targeting radiotracers in xenografted head and neck cancer models. The biodistribution of [111In]In-DOTA-ZCAIX:2 was directly compared with [111In]In-DTPA-G250-F(ab')2 and [111In] In-DTPA-G250 in female BALB/C nu/nu mice bearing two HNSCC xenografts with different levels of CAIX expression. In vivo biodistribution was quantified by means of microSPECT/CT scans and ex vivo biodistribution was determined with the use of a γ-counter. Tumors were snap frozen and sections were stained for CAIX expression, vessels, hypoxia (pimonidazole) and tumor blood perfusion. Tracer uptake was significantly higher in SSCNij153 tumors compared to SCCNij185 tumors for [111In]In-DOTA-HE3-ZCAIX:2: 0.32 ± 0.03 versus 0.18 ± 0.01%ID/g,(p = 0.003) 4 h p.i., for [111In]In-DTPA-girentuximab-F(ab')2: 3.0 ± 0.5%ID/g and 1.2 ± 0.1%ID/g (p = 0.03), 24 h p.i. and for [111In]In-DTPA-girentuximab: 30 ± 2.1%ID/g and 7.0 ± 1.0%ID/g (p = 0.0002) 72 h p.i. SPECT imaging with both [111In]In-DTPA-girentuximab-F(ab')2 and [111In]In-DTPA-girentuximab showed a clear difference in tracer distribution between the two tumor models. The whole IgG, i.e. [111In]In-DTPA-girentuximab, showed the highest tumor-to-muscle ratio. We showed that different CAIX-targeting radiotracers can discriminate a low CAIX-expressing tumor from a high CAIX-expressing head and neck cancer xenografts model. In these hypoxic head and neck xenograft models [111In]In-DTPA-girentuximab showed the most promising results.
Asunto(s)
Anhidrasa Carbónica IX/metabolismo , Neoplasias de Cabeza y Cuello/diagnóstico por imagen , Tomografía Computarizada por Tomografía Computarizada de Emisión de Fotón Único/métodos , Animales , Femenino , Ratones , Ratones Endogámicos BALB C , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
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.