TY - JOUR
T1 - Site-Specific 68Ga Radiolabeling of Trastuzumab Fab via Methionine for ImmunoPET Imaging
AU - Yue, Thomas T.C.
AU - Ge, Ying
AU - Aprile, Francesco A.
AU - Ma, Michelle T.
AU - Pham, Truc T.
AU - Long, Nicholas J.
N1 - Funding Information:
This research was supported by a Cancer Research UK Career Establishment Award (C63178/A24959) (to M.T.M.), the EPSRC Programme for Next Generation Molecular Imaging and Therapy with Radionuclides (EP/S032789/1, “MITHRAS”), the Wellcome Multiuser Equipment Radioanalytical Facility funded by the Wellcome Trust (212885/Z/18/Z), a Schrodinger Studentship from Imperial College London (to T.T.C.Y.), and a UK Research and Innovation Future Leaders Fellowship MR/S033947/1 (to F.A.A.). We thank Dr. Susanna Elledge (University of California, San Francisco) for providing the expression plasmid for the trastuzumab M74 Fab protein.
Publisher Copyright:
© 2023 The Authors. Published by American Chemical Society.
PY - 2023/10/18
Y1 - 2023/10/18
N2 - Bioconjugates of antibodies and their derivatives radiolabeled with β+-emitting radionuclides can be utilized for diagnostic PET imaging. Site-specific attachment of radioactive cargo to antibody delivery vectors provides homogeneous, well-defined immunoconjugates. Recent studies have demonstrated the utility of oxaziridine chemistry for site-specific labeling of methionine residues. Herein, we applied this approach to site-specifically radiolabel trastuzumab-derived Fab immunoconjugates with 68Ga, which can be used for in vivo PET imaging of HER2-positive breast cancer tumors. Initially, a reactive azide was introduced to a single solvent-accessible methionine residue in both the wild-type Fab and an engineered derivative containing methionine residue M74, utilizing the principles of oxaziridine chemistry. Subsequently, these conjugates were functionalized with a modified DFO chelator incorporating dibenzocyclooctyne. The resulting DFO-WT and DFO-M74 conjugates were radiolabeled with generator-produced [68Ga]Ga3+, to yield the novel PET radiotracers, [68Ga]Ga-DFO-WT and [68Ga]Ga-DFO-M74. In vitro and in vivo studies demonstrated that [68Ga]Ga-DFO-M74 exhibited a higher affinity for HER2 receptors. Biodistribution studies in mice bearing orthotopic HER2-positive breast tumors revealed a higher uptake of [68Ga]Ga-DFO-M74 in the tumor tissue, accompanied by rapid renal clearance, enabling clear delineation of tumors using PET imaging. Conversely, [68Ga]Ga-DFO-WT exhibited lower uptake and inferior image contrast compared to [68Ga]Ga-DFO-M74. Overall, the results demonstrate that the highly facile methionine-oxaziridine modification approach can be simply applied to the synthesis of stable and site-specifically modified radiolabeled antibody-chelator conjugates with favorable pharmacokinetics for PET imaging.
AB - Bioconjugates of antibodies and their derivatives radiolabeled with β+-emitting radionuclides can be utilized for diagnostic PET imaging. Site-specific attachment of radioactive cargo to antibody delivery vectors provides homogeneous, well-defined immunoconjugates. Recent studies have demonstrated the utility of oxaziridine chemistry for site-specific labeling of methionine residues. Herein, we applied this approach to site-specifically radiolabel trastuzumab-derived Fab immunoconjugates with 68Ga, which can be used for in vivo PET imaging of HER2-positive breast cancer tumors. Initially, a reactive azide was introduced to a single solvent-accessible methionine residue in both the wild-type Fab and an engineered derivative containing methionine residue M74, utilizing the principles of oxaziridine chemistry. Subsequently, these conjugates were functionalized with a modified DFO chelator incorporating dibenzocyclooctyne. The resulting DFO-WT and DFO-M74 conjugates were radiolabeled with generator-produced [68Ga]Ga3+, to yield the novel PET radiotracers, [68Ga]Ga-DFO-WT and [68Ga]Ga-DFO-M74. In vitro and in vivo studies demonstrated that [68Ga]Ga-DFO-M74 exhibited a higher affinity for HER2 receptors. Biodistribution studies in mice bearing orthotopic HER2-positive breast tumors revealed a higher uptake of [68Ga]Ga-DFO-M74 in the tumor tissue, accompanied by rapid renal clearance, enabling clear delineation of tumors using PET imaging. Conversely, [68Ga]Ga-DFO-WT exhibited lower uptake and inferior image contrast compared to [68Ga]Ga-DFO-M74. Overall, the results demonstrate that the highly facile methionine-oxaziridine modification approach can be simply applied to the synthesis of stable and site-specifically modified radiolabeled antibody-chelator conjugates with favorable pharmacokinetics for PET imaging.
UR - http://www.scopus.com/inward/record.url?scp=85174752376&partnerID=8YFLogxK
U2 - 10.1021/acs.bioconjchem.3c00344
DO - 10.1021/acs.bioconjchem.3c00344
M3 - Article
C2 - 37751398
AN - SCOPUS:85174752376
SN - 1043-1802
VL - 34
SP - 1802
EP - 1810
JO - Bioconjugate chemistry
JF - Bioconjugate chemistry
IS - 10
ER -
