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- Ahlgren, Sara, 1979-
(författare)
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Molecular Radionuclide Imaging Using Site-specifically Labelled Recombinant Affibody Molecules : Preparation and Preclinical Evaluation
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Radionuclide molecular imaging is an emerging multidisciplinary technique that is used in modern medicine to visualise diseases at cellular and molecular levels. This thesis is based on five papers (I-V) and focuses on the development of site-specific radiolabelled recombinant anti-HER2 Affibody molecules and preclinical evaluations in vitro and in vivo of the labelled conjugates. This work is part of a preclinical development of an Affibody molecule-based tracer for molecular imaging of HER2 expressing tumours. Papers I and II report the evaluation of the Affibody molecule ZHER2:2395-C, site-specifically labelled with the radiometals 111In (for SPECT) and 57Co (as a surrogate for 55Co, suitable for PET applications) using a thiol reactive DOTA derivative as a chelator. Both conjugates demonstrated very suitable biodistribution properties, enabling high contrast imaging just a few hours after injection. Papers III and IV report the development and optimization of a technique for site-specific labelling of ZHER2:2395-C with 99mTc using an N3S chelating peptide sequence. 99mTc-ZHER2:2395-C demonstrated high and specific tumour uptake and rapid clearance of non-bound tracer from the blood, resulting in high tumour-to-non-tumour ratios shortly after injection, enabling high contrast imaging. In addition, in the study described in paper IV, freeze-dried kits previously developed for 99mTc-labelling were optimised, resulting in the development of a kit in which all the reagents and protein needed for labelling of ZHER2:2395-C with 99mTc were contained in a single vial. Paper V reports the evaluation of an anti-HER2 Affibody molecule, ABY-025, with a fundamentally re-engineered scaffold. Despite the profound re-engineering, the biodistribution pattern of 111In-ABY-025 was very similar to that of two variants of the parental molecule. It seems reasonable to believe that these results will also be applicable to Affibody molecules towards other targets. Hopefully, this work will also be helpful in the development of other small proteinaceous tracers.
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| 2. |
- Malmberg, Jennie
(författare)
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Preclinical Development of Imaging Agents for HER2 Expression in Prostate Cancer Using Radiolabeled Affibody Molecules
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is focused on pre-clinical evaluation of in vivo detection of HER2-expression in prostate cancer (PCa) patients and on the possibility of using targeted molecular imaging to personalize treatment of disseminated PCa. The work is divided into three distinct parts: (1) the establishment of a preclinical model for further studies, (2) imaging of HER2 in a murine model of PCa and (3) exploration of new treatment regimes against PCa. The characterized cell line panel reflect the heterogeneity of PCa in a way that one cell line never could, and is crucial for a better understanding of different developmental stages during the progression toward androgen independence. The possibility of molecular detection of HER2 in PCa was determined in vitro using 111In-labeled CHX-A’’DTPA-trastuzumab and anti-HER2 ABY-025 affibody molecules. A novel real-time assay for radiolabeled tracer kinetics on living cells was evaluated, in an attempt to bring early developmental work a step closer to the target environment (imaging in living systems). The second part demonstrated the possibility of imaging PCa xenografts, despite the low expression levels, and that ABY-025 is better adapted for this than the therapeutic anti-HER2 antibody trastuzumab. The study also demonstrated that a residualizing radiometal-label further improves imaging contrast. A comparative study of a HER2-binding affibody molecule N-terminally conjugated to DOTA, NOTA or NODAGA highlighted the influence of the chelator on biodistribution and emphasized the importance of taking into account potential metastatic sited during tracer development. The final study used the previously established in vitro model to explore the hypothesis of using molecular imaging of HER2 to identify PCa patients that may benefit from complemental treatment.One conclusion from this thesis is that for imaging of PCa, molecular biological context and expression of the molecular target are equally important to consider. Another, that evaluation of response to treatment also need to consider the effect on the overall phenotypic profile, and consequently what this could mean for the efficacy of the treatment. The results of this thesis are in a larger perspective related to how the heterogeneity of tumors may affect the models used for diagnostics and monitoring of cancer in general.
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| 3. |
- Altai, Mohamed
(författare)
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Tumour Targeting using Radiolabelled Affibody Molecules : Influence of Labelling Chemistry
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Affibody molecules are promising candidates for targeted radionuclide-based imaging and therapy applications. Optimisation of targeting properties would permit the in vivo visualization of cancer-specific surface receptors with high contrast. In therapy, this may increase the ratio of radioactivity uptake between tumour and normal tissues. This thesis work is based on 5 original research articles (papers I-V) and focuses on optimisation of targeting properties of anti-HER2 affibody molecules by optimising the labelling chemistry.Paper I and II report the comparative evaluation of the anti-HER2 ZHER2:2395 affibody molecule site specifically labelled with 111In (suitable for SPECT imaging) and 68Ga (suitable for PET imaging) using the thiol reactive derivatives of DOTA and NODAGA as chelators. The incorporation of different macrocyclic chelators and labelling with different radionuclides modified the biodistribution properties of affibody molecules. This indicates that the labelling strategy may have a profound effect on the targeting properties of radiotracers and must be carefully optimized.Paper III reports the study of the mechanism of renal reabsorption of anti-HER2 ZHER2:2395 affibody molecule. An unknown receptor (not HER2) is suspected to be responsible for the high reabsorption of ZHER2:2395 molecules in the kidneys.Paper IV reports the optimization and development of in vivo targeting properties of 188Re-labelled anti-HER2 affibody molecules. By using an array of peptide based chelators, it was found that substitution of one amino acid by another or changing its position can have a dramatic effect on the biodistribution properties of 188Re-labelled affibody molecules. This permitted the selection of –GGGC chelator whichdemonstrated the lowest retention of radioactivity in kidneys compared to other variants and showed excellent tumour targeting properties.Paper V reports the preclinical evaluation of 188Re-ZHER2:V2 as a potential candidate for targeted radionuclide therapy of HER2-expressing tumours. In vivo experiments in mice along with dosimetry assessment in both murine and human models revealed that future human radiotherapy studies using 188Re-ZHER2:V2 may be feasible.It would be reasonable to believe that the results of optimisation of anti-HER2 affibody molecules summarized in this thesis can be of importance for the development of other scaffold protein-based targeting agents.
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