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  • 1.
    Altai, M.
    et al.
    Immunology, Genetics and Pathology, Uppsala, SWEDEN, .
    Vorobyeva, A.
    Immunology, Genetics and Pathology, Uppsala, SWEDEN, .
    Westerlund, Kristina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science, Protein Engineering.
    Mitran, B.
    Div Mol Imaging, Uppsala, Sweden..
    Orlova, A.
    Div Mol Imaging, Uppsala, Sweden..
    Eriksson Karlström, Amelie
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science, Protein Engineering.
    Tolmachev, V.
    Immunology, Genetics and Pathology, Uppsala, SWEDEN, .
    A novel method for conjugation of PNA to antibodies for radionuclide based pretargeting: proof of principal2018In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 45, p. S648-S648Article in journal (Other academic)
  • 2. Altai, M.
    et al.
    Westerlund, Kristina
    KTH, School of Biotechnology (BIO), Protein Technology.
    Velletta, J.
    Honarvar, H.
    Orlova, A.
    Eriksson Karlström, Amelie
    KTH, School of Biotechnology (BIO), Protein Technology.
    Tolmachev, V.
    Comparative evaluation of Lu-177-HP2 and In-111-HP2, secondary agents for affibody-based PNA-mediated radionuclide pretargeting2016In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 43, p. S237-S237Article in journal (Refereed)
  • 3. Altai, M.
    et al.
    Westerlund, Kristina
    KTH, School of Biotechnology (BIO), Protein Technology.
    Velletta, J.
    Mitran, B.
    Honarvar, H.
    Eriksson Karlström, Amelie
    KTH, School of Biotechnology (BIO), Protein Technology.
    Evaluation of affibody molecule-based PNA-mediated radionuclide pretargeting: Development of an optimized conjugation protocol and 177Lu labeling2017In: Nuclear Medicine and Biology, ISSN 0969-8051, E-ISSN 1872-9614, Vol. 54, p. 1-9Article in journal (Refereed)
    Abstract [en]

    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 15 h to 30 min, 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 1 h 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 1 h 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 4 h 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.

  • 4. Honarvar, H.
    et al.
    Muller, C.
    van der Meulen, N.
    Cohrs, S.
    Westerlund, K.
    KTH, School of Biotechnology (BIO), Protein Technology.
    Eriksson Karlström, Amelie
    KTH, School of Biotechnology (BIO).
    Schibli, R.
    Tolmachev, V.
    Development and application of first Sc-44-labeled Affibody molecule2016In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 43, p. S177-S177Article in journal (Refereed)
  • 5. Honarvar, H.
    et al.
    Westerlund, Kristina
    KTH, School of Biotechnology (BIO), Protein Technology.
    Altai, M.
    Sandstrom, M.
    Orlova, A.
    Tolmachev, V.
    Karlstrom, A. Eriksson
    Feasibility of Affibody molecule-based PNA-mediated pretargeting2015In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 42, p. S101-S102Article in journal (Refereed)
  • 6. Honarvar, Hadis
    et al.
    Muller, Cristina
    Cohrs, Susan
    Haller, Stephanie
    Westerlund, Kristina
    KTH, School of Biotechnology (BIO), Protein Technology.
    Eriksson Karlström, Amelie
    KTH, School of Biotechnology (BIO), Protein Technology.
    van der Meulen, Nicholas P.
    Schibli, Roger
    Tolmachev, Vladimir
    Evaluation of the first Sc-44-labeled Affibody molecule for imaging of HER2-expressing tumors2017In: Nuclear Medicine and Biology, ISSN 0969-8051, E-ISSN 1872-9614, Vol. 45, p. 15-21Article in journal (Refereed)
    Abstract [en]

    Introduction: Affibody molecules are small (58 amino acids) high-affinity proteins based on a tri-helix nonimmunoglobulin scaffold. A clinical study has demonstrated that PET imaging using Affibody molecules labeled with Ga-68 (T-1/2 = 68 min) can visualize metastases of breast cancer expressing human epidermal growth factor receptor type 2 (HER2) and provide discrimination between tumors with high and low expression level. This may help to identify breast cancer patients benefiting from HER2-targeting therapies. The best discrimination was at 4 h post injection. Due to longer half-life, a positron-emitting radionuclide Sc-44 (T-1/2 = 4.04 h) might be a preferable label for Affibody molecules for imaging at several hours after injection. Methods: A synthetic second-generation anti-HER2 Affibody molecule Z(HER2:2891) was labeled with Sc-44 via a DOTA-chelator conjugated to the N-terminal amino group. Binding specificity, affinity and cellular processing Sc-44-DOTA-Z(HER2:2891) and Ga-68-DOTA-Z(HER2:2891) were compared in vitro using HER2-expressing cells. Biodistribution and imaging properties of Sc-44-DOTA-Z(HER2,2891) and Ga-68-DOTA-Z(HER2:2891) were evaluated in Balb/c nude mice bearing HER2-expression xenografts. Results: The labeling yield of 98 +/- 2% and specific activity of 7.8 GBq/mu mol were obtained. The conjugate demonstrated specific binding to HER2-expressing SKOV3.ip cells in vitro and to SKOV3.ip xenografts in nude mice. The distribution of radioactivity at 3 h post injection was similar for Sc-44-DOTA-Z(HER2:2891) and Ga-68-DOTA-Z(HER2:2891), but the blood clearance of the Sc-44-labeled variant was slower and the tumor-to-blood ratio was reduced (15 +/- 2 for (SC)-S-44-DOTA-Z(HER2:2891) vs 46 +/- 9 for Ga-68-DOTA-Z(HER2.2891)). At 6 h after injection of Sc-44-DOTA-Z(HER2,2891) the tumor uptake was 8 +/- 2% IA/g and the tumor-to-blood ratio was 51 +/- 8. Imaging using small-animal PET/CT demonstrated that (SC)-S-44-DOTA-ZHER2,2891 provides specific and high-contrast imaging of HER2-expressing xenografts. Conclusion: The Sc-44- DOTA-Z(HER2:2891) Affibody molecule is a promising probe for imaging of HER2-expression in malignant tumors.

  • 7. Honarvar, Hadis
    et al.
    Westerlund, Kristina
    KTH, School of Biotechnology (BIO), Protein Technology.
    Altai, Mohamed
    Sandstrom, Mattias
    Orlova, Anna
    Tolmachev, Vladimir
    Eriksson Karlström, Amelie
    KTH, School of Biotechnology (BIO), Protein Technology.
    Feasibility of Affibody Molecule-Based PNA-Mediated Radionuclide Pretargeting of Malignant Tumors2016In: Theranostics, ISSN 1838-7640, E-ISSN 1838-7640, Vol. 6, no 1, p. 93-103Article in journal (Refereed)
    Abstract [en]

    Affibody molecules are small (7 kDa), non-immunoglobulin scaffold proteins with a potential as targeting agents for radionuclide imaging of cancer. However, high renal re-absorption of Affibody molecules prevents their use for radionuclide therapy with residualizing radiometals. We hypothesized that the use of Affibody-based peptide nucleic acid (PNA)-mediated pretargeting would enable higher accumulation of radiometals in tumors than in kidneys. To test this hypothesis, we designed an Affibody-PNA chimera Z(HER2:342)-SR-HP1 containing a 15-mer HP1 PNA recognition tag and a complementary HP2 hybridization probe permitting labeling with both I-125 and In-111. In-111-Z(HER2:342)-SR-HP1 bound specifically to HER2-expressing BT474 and SKOV-3 cancer cells in vitro, with a K-D of 6+/-2 pM for binding to SKOV-3 cells. Specific high affinity binding of the radiolabeled complementary PNA probe In-111-/I-125-HP2 to Z(HER2:342)-SR-HP1 pre-treated cells was demonstrated. In-111-Z(HER2:342)-SR-HP1 demonstrated specific accumulation in SKOV-3 xenografts in BALB/C nu/nu mice and rapid clearance from blood. Pre-saturation of SKOV-3 with non-labeled anti-HER2 Affibody or the use of HER2-negative Ramos xenografts resulted in significantly lower tumor uptake of In-111-Z(HER2:342)-SR-HP1. The complementary PNA probe In-111/I-125-HP2 accumulated in SKOV-3 xenografts when Z(HER2:342)-SR-HP1 was injected 4 h earlier. The tumor accumulation of In-111/I-125-HP2 was negligible without Z(HER2:342)-SR-HP1 pre-injection. The uptake of In-111-HP2 in SKOV-3 xenografts was 19+/-2 % ID/g at 1 h after injection. The uptake in blood and kidneys was approximately 50- and 2-fold lower, respectively. In conclusion, we have shown that the use of Affibody-based PNA-mediated pretargeting enables specific delivery of radiometals to tumors and provides higher radiometal concentration in tumors than in kidneys.

  • 8.
    Vorobyeva, A.
    et al.
    Uppsala Univ, Uppsala, Sweden..
    Westerlund, Kristina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science, Protein Engineering.
    Mitran, B.
    Uppsala Univ, Uppsala, Sweden..
    Altai, M.
    Uppsala Univ, Uppsala, Sweden..
    Rinne, S.
    Uppsala Univ, Uppsala, Sweden..
    Sorensen, J.
    Uppsala Univ, Uppsala, Sweden..
    Orlova, A.
    Uppsala Univ, Uppsala, Sweden..
    Eriksson Karlström, Amelie
    KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science, Protein Engineering.
    Tolmachev, V.
    Uppsala Univ, Uppsala, Sweden..
    Development of a PET Imaging Approach for Selection of Patients for Affibody-Based PNA-Mediated Pretargeted Radionuclide Therapy2018In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 45, p. S104-S104Article in journal (Other academic)
  • 9. Vorobyeva, A.
    et al.
    Westerlund, Kristina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science, Protein Engineering.
    Mitran, B.
    Altai, M.
    Rinne, S.
    Sörensen, J.
    Orlova, A.
    Tolmachev, V.
    Eriksson Karlström, Amelie
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science.
    Development of an optimal imaging strategy for selection of patients for affibody-based PNA-mediated radionuclide therapy2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, no 1, article id 9643Article in journal (Refereed)
    Abstract [en]

    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. 

  • 10.
    Westerlund, Kristina
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science, Protein Engineering.
    Altai, Mohamed
    Uppsala Univ, Dept Immunol Genet & Pathol, SE-75181 Uppsala, Sweden..
    Mitran, Bogdan
    Uppsala Univ, Div Mol Imaging, Dept Med Chem, Uppsala, Sweden..
    Konijnenberg, Mark
    Erasmus MC, Dept Radiol & Nucl Med, Rotterdam, Netherlands..
    Oroujeni, Maryam
    Uppsala Univ, Dept Immunol Genet & Pathol, SE-75181 Uppsala, Sweden..
    Atterby, Christina
    Uppsala Univ, Dept Immunol Genet & Pathol, SE-75181 Uppsala, Sweden..
    de Jong, Marion
    Erasmus MC, Dept Radiol & Nucl Med, Rotterdam, Netherlands..
    Orlova, Anna
    Uppsala Univ, Div Mol Imaging, Dept Med Chem, Uppsala, Sweden..
    Mattsson, Johanna
    Uppsala Univ, Dept Immunol Genet & Pathol, SE-75181 Uppsala, Sweden..
    Micke, Patrick
    Uppsala Univ, Dept Immunol Genet & Pathol, SE-75181 Uppsala, Sweden..
    Eriksson Karlström, Amelie
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science, Protein Engineering.
    Tolmachev, Vladimir
    Uppsala Univ, Dept Immunol Genet & Pathol, SE-75181 Uppsala, Sweden..
    Radionuclide Therapy of HER2-Expressing Human Xenografts Using Affibody-Based Peptide Nucleic Acid-Mediated Pretargeting: In Vivo Proof of Principle2018In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 59, no 7, p. 1092-1098Article in journal (Refereed)
    Abstract [en]

    Affibody molecules are small proteins engineered using a nonanti-body 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 (Z(HER2:342)-SR-HP1) was used as the primary pretargeting agent. A complementary AGTCGTGATGTAGTC PNA conjugated to the chelator DOTA and labeled with the radionuclide Lu-177 (Lu-177-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 mu g (0.65 nmol) of Lu-177-HP2 was injected 16 h after injection of 100 mu g (7.7 nmol) of Z(HER2:342)-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 Z(HER2:342)-SR-HP1 only (37 d), the same amount and activity of Lu-177-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.

  • 11.
    Westerlund, Kristina
    et al.
    KTH, School of Biotechnology (BIO), Protein Technology.
    Honarvar, H.
    Tolmachev, V.
    Eriksson Karlström, Amelie
    KTH, School of Biotechnology (BIO), Protein Technology.
    Design, Preparation, and Characterization of PNA-Based Hybridization Probes for Affibody-Molecule-Mediated Pretargeting2015In: Bioconjugate chemistry, ISSN 1043-1802, E-ISSN 1520-4812, Vol. 26, no 8, p. 1724-1736Article in journal (Refereed)
    Abstract [en]

    In radioimmunotherapy, the contrast between tumor and normal tissue can be improved by using a pretargeting strategy with a primary targeting agent, which is conjugated to a recognition tag, and a secondary radiolabeled molecule binding specifically to the recognition tag. The secondary molecule is injected after the targeting agent has accumulated in the tumor and is designed to have a favorable biodistribution profile, with fast clearance from blood and low uptake in normal tissues. In this study, we have designed and evaluated two complementary peptide nucleic acid (PNA)-based probes for specific and high-affinity association in vivo. An anti-HER2 Affibody-PNA chimera, Z<inf>HER2:342</inf>-SR-HP1, was produced by a semisynthetic approach using sortase A catalyzed ligation of a recombinantly produced Affibody molecule to a PNA-based HP1-probe assembled using solid-phase chemistry. A complementary HP2 probe carrying a DOTA chelator and a tyrosine for dual radiolabeling was prepared by solid-phase synthesis. Circular dichroism (CD) spectroscopy and UV thermal melts showed that the probes can hybridize to form a structured duplex with a very high melting temperature (T<inf>m</inf>), both in HP1:HP2 and in Z<inf>HER2:342</inf>-SR-HP1:HP2 (T<inf>m</inf> = 86-88 °C), and the high binding affinity between Z<inf>HER2:342</inf>-SR-HP1 and HP2 was confirmed in a surface plasmon resonance (SPR)-based binding study. Following a moderately fast association (1.7 × 105 M-1 s-1), the dissociation of the probes was extremely slow and <5% dissociation was observed after 17 h. The equilibrium dissociation constant (K<inf>D</inf>) for Z<inf>HER2:342</inf>-SR-HP1:HP2 binding to HER2 was estimated by SPR to be 212 pM, suggesting that the conjugation to PNA does not impair Affibody binding to HER2. The biodistribution profiles of 111In- and 125I-labeled HP2 were measured in NMRI mice, showing very fast blood clearance rates and low accumulation of radioactivity in kidneys and other organs. The measured radioactivity in blood was 0.63 ± 0.15 and 0.41 ± 0.15%ID/g for 125I- and 111In-HP2, respectively, at 1 h p.i., and at 4 h p.i., the kidney accumulation of radioactivity was 0.17 ± 0.04%ID/g for 125I-HP2 and 3.83 ± 0.39%ID/g for 111In-HP2. Taken together, the results suggest that a PNA-based system has suitable biophysical and in vivo properties and is a promising approach for pretargeting of Affibody molecules.

  • 12.
    Westerlund, Kristina
    et al.
    KTH, School of Biotechnology (BIO), Protein Technology.
    Honarvar, Hadis
    Norrström, Emily
    KTH, School of Biotechnology (BIO), Protein Technology.
    Strand, Joanna
    Mitran, Bogdan
    Orlova, Anna
    Eriksson Karlström, Amelie
    KTH, School of Biotechnology (BIO), Protein Technology.
    Tolmachev, Vladimir
    Increasing the Net Negative Charge by Replacement of DOTA Chelator with DOTAGA Improves the Biodistribution of Radiolabeled Second-Generation Synthetic Affibody Molecules2016In: Molecular Pharmaceutics, ISSN 1543-8384, E-ISSN 1543-8392, Vol. 13, no 5, p. 1668-1678Article in journal (Refereed)
    Abstract [en]

    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 Z(HER2:2891) Affibody molecule was synthesized and labeled with In-111 and Ga-68 using DOTAGA and DOTA chelators. The chelators were manually coupled to the N-terminus of Z(HER2:2891) forming an amide bond. Labeling DOTAGA-Z(HER2:2891) and DOTA-Z(HER2:2891) with Ga-68 and In-111 resulted in stable radioconjugates. The tumor-targeting and biodistribution properties of the In-111- and Ga-68-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 In-111-labeled conjugates showed more rapid blood clearance than the Ga-68-labeled conjugates. The most pronounced influence of the chelators was found when they were labeled with Ga-68. 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.

  • 13.
    Westerlund, Kristina
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science.
    Vorobyeva, Anzhelika
    Uppsala Univ, Dept Immunol Genet & Pathol, Uppsala, Sweden..
    Mitran, Bogdan
    Uppsala Univ, Dept Med Chem, Div Mol Imaging, Uppsala, Sweden..
    Orlova, Anna
    Uppsala Univ, Dept Med Chem, Div Mol Imaging, Uppsala, Sweden..
    Tolmachev, Vladimir
    Uppsala Univ, Dept Immunol Genet & Pathol, Uppsala, Sweden..
    Eriksson Karlström, Amelie
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science.
    Altai, Mohamed
    Uppsala Univ, Dept Immunol Genet & Pathol, Uppsala, Sweden..
    Site-specific conjugation of recognition tags to trastuzumab for peptide nucleic acid-mediated radionuclide HER2 pretargeting2019In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 203, p. 73-85Article in journal (Refereed)
    Abstract [en]

    Pretargeting is a promising strategy to reach high imaging contrast in a shorter time than by targeting with directly radiolabeled monoclonal antibodies (mAbs). One of problems in pretargeting is a site-specific, reproducible and uniform conjugation of recognition tags to mAbs. To solve this issue we propose a photoconjugation to covalently couple a recognition tag to a mAb via a photoactivatable Z domain. The Z-domain, a 58-amino acid protein derived from the IgG-binding B-domain of Staphylococcus aureus protein A, has a well-characterized binding site in the Fc portion of IgG. We tested the feasibility of this approach using pretargeting based on hybridization between peptide nucleic acids (PNAs). We have used photoconjugation to couple trastuzumab with the PNA-based hybridization probe, HP1. A complementary [Co-57]Co-labeled PNA hybridization probe ([Co-57]Co-HP2) was used as the secondary targeting probe. In vitro studies demonstrated that trastuzumab-ZHP1 bound specifically to human epidermal growth factor receptor 2 (HER2)-expressing cells with nanomolar affinity. The binding of the secondary [Co-57]Co-HP2 probe to trastuzumab-PNA-pretreated cells was in the picomolar affinity range. A two-fold increase in SKOV-3 tumor targeting was achieved when [Co-57]Co-HP2 (0.7 nmol) was injected 48 h after injection of trastuzumab-ZHP1 (0.5 nmol) compared with trastuzumab-ZHP1 alone (0.8 +/- 0.2 vs. 0.33 +/- 0.06 %ID/g). Tumor accumulation of [Co-57]Co-HP2 was significantly reduced by pre-saturation with trastuzumab or when no trastuzumab-ZHP1 was preinjected. A tumor-to-blood uptake ratio of 1.5 +/- 0.3 was achieved resulting in a clear visualization of HER2-expressing xenografts as confirmed by SPECT imaging. In conclusion, the feasibility of stable site-specific coupling of a PNA-based recognition tag to trastuzumab and successful pretargeting has been demonstrated. This approach can hopefully be used for a broad range of mAbs and recognition tags.

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