Synthesis and In Vitro Evaluation of a Scandium-44 Radiolabeled Nanobody as a PD-L1 PET Imaging Probe
<b>Background/Objective</b>: Noninvasive PET imaging-based assessment of PD-L1 expression is of high clinical value for better patient selection and treatment response rates to PD-L1 immunotherapies. Due to their shorter biological half-life and faster clearance from the blood pool, radi...
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| author | Viktoria E. Krol Aditya Bansal Manasa Kethamreddy Jason R. Ellinghuysen Daniel J. Vail Fabrice Lucien-Matteoni Haidong Dong Sean S. Park Mukesh K. Pandey |
| author_facet | Viktoria E. Krol Aditya Bansal Manasa Kethamreddy Jason R. Ellinghuysen Daniel J. Vail Fabrice Lucien-Matteoni Haidong Dong Sean S. Park Mukesh K. Pandey |
| author_sort | Viktoria E. Krol |
| collection | DOAJ |
| description | <b>Background/Objective</b>: Noninvasive PET imaging-based assessment of PD-L1 expression is of high clinical value for better patient selection and treatment response rates to PD-L1 immunotherapies. Due to their shorter biological half-life and faster clearance from the blood pool, radiolabeled antibody fragments are an attractive alternative for imaging than their full-length IgG counterpart. This work investigated the radiosynthesis and in vitro cell uptake of anti-PD-L1-B11-nanobody radiolabeled with <sup>44</sup>Sc (t<sub>1/2</sub> = 4.04 h) as an alternative to anti-PD-L1-B11-IgG, better suited for longer half-life radioisotopes such as <sup>89</sup>Zr (t<sub>1/2</sub> = 78.41 h). <b>Methods</b>: The proteins were conjugated with p-SCN-Bn-DTPA and radiolabeled at room temperature with <sup>44</sup>Sc, achieving a radiochemical yield of a RCY of 94.8 ± 3.1% (<i>n</i> = 3) for [<sup>44</sup>Sc]Sc-B11-IgG and 73.6 ± 12.1% (<i>n</i> = 3) for [<sup>44</sup>Sc]Sc-B11-nanobody, before purification. <b>Results</b>: Significantly higher uptake in the PD-L1<sub>+</sub> cells than PD-L1<sub>KO</sub> cells was observed for both probes. However, high non-specific uptake, particularly of the radiolabeled B11-nanobody, was also observed which may negatively impact its potential as a molecular imaging probe. <b>Conclusions</b>: Due to the high non-specific uptake in vitro, the <sup>44</sup>Sc radiolabeled nanobody was not progressed to further in vivo evaluation. These results should, however, not discourage future evaluations of other nanobody based probes radiolabeled with <sup>44</sup>Sc, due to their well-matched biological and physical half-life. |
| format | Article |
| id | doaj-art-d79dd5f2a21e4baabeed3af96096bbcc |
| institution | Kabale University |
| issn | 1999-4923 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | MDPI AG |
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| series | Pharmaceutics |
| spelling | doaj-art-d79dd5f2a21e4baabeed3af96096bbcc2025-08-20T03:27:39ZengMDPI AGPharmaceutics1999-49232025-06-0117679610.3390/pharmaceutics17060796Synthesis and In Vitro Evaluation of a Scandium-44 Radiolabeled Nanobody as a PD-L1 PET Imaging ProbeViktoria E. Krol0Aditya Bansal1Manasa Kethamreddy2Jason R. Ellinghuysen3Daniel J. Vail4Fabrice Lucien-Matteoni5Haidong Dong6Sean S. Park7Mukesh K. Pandey8Department of Radiology, Mayo Clinic, Rochester, MN 55905, USADepartment of Radiology, Mayo Clinic, Rochester, MN 55905, USADepartment of Radiology, Mayo Clinic, Rochester, MN 55905, USADepartment of Radiology, Mayo Clinic, Rochester, MN 55905, USADepartment of Radiology, Mayo Clinic, Rochester, MN 55905, USADepartment of Urology, Mayo Clinic, Rochester, MN 55905, USADepartment of Urology, Mayo Clinic, Rochester, MN 55905, USADepartment of Radiation Oncology, Mayo Clinic, Rochester, MN 55905, USADepartment of Radiology, Mayo Clinic, Rochester, MN 55905, USA<b>Background/Objective</b>: Noninvasive PET imaging-based assessment of PD-L1 expression is of high clinical value for better patient selection and treatment response rates to PD-L1 immunotherapies. Due to their shorter biological half-life and faster clearance from the blood pool, radiolabeled antibody fragments are an attractive alternative for imaging than their full-length IgG counterpart. This work investigated the radiosynthesis and in vitro cell uptake of anti-PD-L1-B11-nanobody radiolabeled with <sup>44</sup>Sc (t<sub>1/2</sub> = 4.04 h) as an alternative to anti-PD-L1-B11-IgG, better suited for longer half-life radioisotopes such as <sup>89</sup>Zr (t<sub>1/2</sub> = 78.41 h). <b>Methods</b>: The proteins were conjugated with p-SCN-Bn-DTPA and radiolabeled at room temperature with <sup>44</sup>Sc, achieving a radiochemical yield of a RCY of 94.8 ± 3.1% (<i>n</i> = 3) for [<sup>44</sup>Sc]Sc-B11-IgG and 73.6 ± 12.1% (<i>n</i> = 3) for [<sup>44</sup>Sc]Sc-B11-nanobody, before purification. <b>Results</b>: Significantly higher uptake in the PD-L1<sub>+</sub> cells than PD-L1<sub>KO</sub> cells was observed for both probes. However, high non-specific uptake, particularly of the radiolabeled B11-nanobody, was also observed which may negatively impact its potential as a molecular imaging probe. <b>Conclusions</b>: Due to the high non-specific uptake in vitro, the <sup>44</sup>Sc radiolabeled nanobody was not progressed to further in vivo evaluation. These results should, however, not discourage future evaluations of other nanobody based probes radiolabeled with <sup>44</sup>Sc, due to their well-matched biological and physical half-life.https://www.mdpi.com/1999-4923/17/6/796Scandium-44immunoPETmolecular imagingPD-L1breast cancer |
| spellingShingle | Viktoria E. Krol Aditya Bansal Manasa Kethamreddy Jason R. Ellinghuysen Daniel J. Vail Fabrice Lucien-Matteoni Haidong Dong Sean S. Park Mukesh K. Pandey Synthesis and In Vitro Evaluation of a Scandium-44 Radiolabeled Nanobody as a PD-L1 PET Imaging Probe Pharmaceutics Scandium-44 immunoPET molecular imaging PD-L1 breast cancer |
| title | Synthesis and In Vitro Evaluation of a Scandium-44 Radiolabeled Nanobody as a PD-L1 PET Imaging Probe |
| title_full | Synthesis and In Vitro Evaluation of a Scandium-44 Radiolabeled Nanobody as a PD-L1 PET Imaging Probe |
| title_fullStr | Synthesis and In Vitro Evaluation of a Scandium-44 Radiolabeled Nanobody as a PD-L1 PET Imaging Probe |
| title_full_unstemmed | Synthesis and In Vitro Evaluation of a Scandium-44 Radiolabeled Nanobody as a PD-L1 PET Imaging Probe |
| title_short | Synthesis and In Vitro Evaluation of a Scandium-44 Radiolabeled Nanobody as a PD-L1 PET Imaging Probe |
| title_sort | synthesis and in vitro evaluation of a scandium 44 radiolabeled nanobody as a pd l1 pet imaging probe |
| topic | Scandium-44 immunoPET molecular imaging PD-L1 breast cancer |
| url | https://www.mdpi.com/1999-4923/17/6/796 |
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