Chelator impact: investigating the pharmacokinetic behavior of copper-64 labeled PD-L1 radioligands
Abstract Background Programmed cell death ligand 1 (PD-L1) plays a critical role in the tumor microenvironment and overexpression in several solid cancers has been reported. This was associated with a downregulation of the local immune response, specifically of T-cells. Immune checkpoint inhibitors...
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| Format: | Article |
| Language: | English |
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SpringerOpen
2024-02-01
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| Series: | EJNMMI Radiopharmacy and Chemistry |
| Subjects: | |
| Online Access: | https://doi.org/10.1186/s41181-024-00243-5 |
| _version_ | 1797272760607571968 |
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| author | Fabian Krutzek Cornelius K. Donat Sven Stadlbauer |
| author_facet | Fabian Krutzek Cornelius K. Donat Sven Stadlbauer |
| author_sort | Fabian Krutzek |
| collection | DOAJ |
| description | Abstract Background Programmed cell death ligand 1 (PD-L1) plays a critical role in the tumor microenvironment and overexpression in several solid cancers has been reported. This was associated with a downregulation of the local immune response, specifically of T-cells. Immune checkpoint inhibitors showed a potential to break this localized immune paralysis, but only 30% of patients are considered responders. New diagnostic approaches are therefore needed to determine patient eligibility. Small molecule radiotracers targeting PD-L1, may serve as such diagnostic tools, addressing the heterogeneous PD-L1 expression between and within tumor lesions, thus aiding in therapy decisions. Results Four biphenyl-based small-molecule PD-L1 ligands were synthesized using a convergent synthetic route with a linear sequence of up to eleven steps. As a chelator NODA-GA, CB-TE2A or DiAmSar was used to allow radiolabeling with copper-64 ([64Cu]Cu-14–[64Cu]Cu-16). In addition, a dimeric structure based on DiAmSar was synthesized ([64Cu]Cu-17). All four radioligands exhibited high proteolytic stability (> 95%) up to 48 h post-radiolabeling. Saturation binding yielded moderate affinities toward PD-L1, ranging from 100 to 265 nM. Real-time radioligand binding provided more promising K D values around 20 nM for [64Cu]Cu-14 and [64Cu]Cu-15. In vivo PET imaging in mice bearing both PC3 PD-L1 overexpressing and PD-L1-mock tumors was performed at 0–2, 4–5 and 24–25 h post injection (p.i.). This revealed considerably different pharmacokinetic profiles, depending on the substituted chelator. [64Cu]Cu-14, substituted with NODA-GA, showed renal clearance with low liver uptake, whereas substitution with the cross-bridged cyclam chelator CB-TE2A resulted in a primarily hepatobiliary clearance. Notably, the monomeric DiAmSar radioligand [64Cu]Cu-16 demonstrated a higher liver uptake than [64Cu]Cu-15, but was still renally cleared as evidenced by the lack of uptake in gall bladder and intestines. The dimeric structure [64Cu]Cu-17 showed extensive accumulation and trapping in the liver but was also cleared via the renal pathway. Of all tracer candidates and across all timepoints, [64Cu]Cu-17 showed the highest accumulation at 24 h p.i. in the PD-L1-overexpressing tumor of all timepoints and all radiotracers, indicating drastically increased circulation time upon dimerization of two PD-L1 binding motifs. Conclusions This study shows that chelator choice significantly influences the pharmacokinetic profile of biphenyl-based small molecule PD-L1 radioligands. The NODA-GA-conjugated radioligand [64Cu]Cu-14 exhibited favorable renal clearance; however, the limited uptake in tumors suggests the need for structural modifications to the binding motif for future PD-L1 radiotracers. |
| first_indexed | 2024-03-07T14:33:59Z |
| format | Article |
| id | doaj.art-6b92fb27767c475693a3d55f22417df7 |
| institution | Directory Open Access Journal |
| issn | 2365-421X |
| language | English |
| last_indexed | 2024-03-07T14:33:59Z |
| publishDate | 2024-02-01 |
| publisher | SpringerOpen |
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| series | EJNMMI Radiopharmacy and Chemistry |
| spelling | doaj.art-6b92fb27767c475693a3d55f22417df72024-03-05T20:46:14ZengSpringerOpenEJNMMI Radiopharmacy and Chemistry2365-421X2024-02-019112410.1186/s41181-024-00243-5Chelator impact: investigating the pharmacokinetic behavior of copper-64 labeled PD-L1 radioligandsFabian Krutzek0Cornelius K. Donat1Sven Stadlbauer2Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-RossendorfInstitute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-RossendorfInstitute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-RossendorfAbstract Background Programmed cell death ligand 1 (PD-L1) plays a critical role in the tumor microenvironment and overexpression in several solid cancers has been reported. This was associated with a downregulation of the local immune response, specifically of T-cells. Immune checkpoint inhibitors showed a potential to break this localized immune paralysis, but only 30% of patients are considered responders. New diagnostic approaches are therefore needed to determine patient eligibility. Small molecule radiotracers targeting PD-L1, may serve as such diagnostic tools, addressing the heterogeneous PD-L1 expression between and within tumor lesions, thus aiding in therapy decisions. Results Four biphenyl-based small-molecule PD-L1 ligands were synthesized using a convergent synthetic route with a linear sequence of up to eleven steps. As a chelator NODA-GA, CB-TE2A or DiAmSar was used to allow radiolabeling with copper-64 ([64Cu]Cu-14–[64Cu]Cu-16). In addition, a dimeric structure based on DiAmSar was synthesized ([64Cu]Cu-17). All four radioligands exhibited high proteolytic stability (> 95%) up to 48 h post-radiolabeling. Saturation binding yielded moderate affinities toward PD-L1, ranging from 100 to 265 nM. Real-time radioligand binding provided more promising K D values around 20 nM for [64Cu]Cu-14 and [64Cu]Cu-15. In vivo PET imaging in mice bearing both PC3 PD-L1 overexpressing and PD-L1-mock tumors was performed at 0–2, 4–5 and 24–25 h post injection (p.i.). This revealed considerably different pharmacokinetic profiles, depending on the substituted chelator. [64Cu]Cu-14, substituted with NODA-GA, showed renal clearance with low liver uptake, whereas substitution with the cross-bridged cyclam chelator CB-TE2A resulted in a primarily hepatobiliary clearance. Notably, the monomeric DiAmSar radioligand [64Cu]Cu-16 demonstrated a higher liver uptake than [64Cu]Cu-15, but was still renally cleared as evidenced by the lack of uptake in gall bladder and intestines. The dimeric structure [64Cu]Cu-17 showed extensive accumulation and trapping in the liver but was also cleared via the renal pathway. Of all tracer candidates and across all timepoints, [64Cu]Cu-17 showed the highest accumulation at 24 h p.i. in the PD-L1-overexpressing tumor of all timepoints and all radiotracers, indicating drastically increased circulation time upon dimerization of two PD-L1 binding motifs. Conclusions This study shows that chelator choice significantly influences the pharmacokinetic profile of biphenyl-based small molecule PD-L1 radioligands. The NODA-GA-conjugated radioligand [64Cu]Cu-14 exhibited favorable renal clearance; however, the limited uptake in tumors suggests the need for structural modifications to the binding motif for future PD-L1 radiotracers.https://doi.org/10.1186/s41181-024-00243-5PET-tracersSmall moleculesCopper-64ChelatorsPD-L1 |
| spellingShingle | Fabian Krutzek Cornelius K. Donat Sven Stadlbauer Chelator impact: investigating the pharmacokinetic behavior of copper-64 labeled PD-L1 radioligands EJNMMI Radiopharmacy and Chemistry PET-tracers Small molecules Copper-64 Chelators PD-L1 |
| title | Chelator impact: investigating the pharmacokinetic behavior of copper-64 labeled PD-L1 radioligands |
| title_full | Chelator impact: investigating the pharmacokinetic behavior of copper-64 labeled PD-L1 radioligands |
| title_fullStr | Chelator impact: investigating the pharmacokinetic behavior of copper-64 labeled PD-L1 radioligands |
| title_full_unstemmed | Chelator impact: investigating the pharmacokinetic behavior of copper-64 labeled PD-L1 radioligands |
| title_short | Chelator impact: investigating the pharmacokinetic behavior of copper-64 labeled PD-L1 radioligands |
| title_sort | chelator impact investigating the pharmacokinetic behavior of copper 64 labeled pd l1 radioligands |
| topic | PET-tracers Small molecules Copper-64 Chelators PD-L1 |
| url | https://doi.org/10.1186/s41181-024-00243-5 |
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