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. 2023 Apr 21;14(5):636-644.
doi: 10.1021/acsmedchemlett.3c00057. eCollection 2023 May 11.

Modular One-Pot Strategy for the Synthesis of Heterobivalent Tracers

Thibaud Bailly  1 , Sacha Bodin  2 , Victor Goncalves  1 , Franck Denat  1 , Clément Morgat  2   3 , Aurélie Prignon  4 , Ibai E Valverde  1
Affiliations

Modular One-Pot Strategy for the Synthesis of Heterobivalent Tracers

Thibaud Bailly et al. ACS Med Chem Lett. .

Abstract

Bivalent ligands, i.e., molecules having two ligands covalently connected by a linker, have been gathering attention since the first description of their pharmacological potential in the early 80s. However, their synthesis, particularly of labeled heterobivalent ligands, can still be cumbersome and time-consuming. We herein report a straightforward procedure for the modular synthesis of labeled heterobivalent ligands (HBLs) using dual reactive 3,6-dichloro-1,2,4,5-tetrazine as a starting material and suitable partners for sequential SNAr and inverse electron-demand Diels-Alder (IEDDA) reactions. This assembly method conducted in a stepwise or in a sequential one-pot manner provides quick access to multiple HBLs. A conjugate combining ligands toward the prostate-specific membrane antigen (PSMA) and the gastrin-releasing peptide receptor (GRPR) was radiolabeled, and its biological activity was assessed in vitro and in vivo (receptor binding affinity, biodistribution, imaging) as an illustration that the assembly methodology preserves the tumor targeting properties of the ligands.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
General principle of the synthesis of heterobivalent ligands using dichloro-s-tetrazine.
Figure 2
Figure 2
Structures of targeting moieties 1, 2, and 3.
Figure 3
Figure 3
Structures of different spacers used in the synthesis.
Scheme 1
Scheme 1. Synthetic Reactions Used for the Preparation of Thiol- and Amino-Functionalized CXCR4, GRPR, and PSMA Ligands
Scheme 2
Scheme 2. General Synthetic Route toward HBL-Based Imaging Agents
Overall yields (with intermediate purifications of 13 and 14) are indicated in parentheses. TFA was used to deprotect compounds 18, 19, 21, and 22, whereas FA was preferred for compound 20.
Figure 4
Figure 4
Representative chromatograms of the crude mixture at different steps of the one-pot synthesis of 18. (a) Chromatogram of 9, (b) chromatogram of the crude mixture of the reaction of 9 with dichlorotetrazine to provide 13, (c) chromatogram of the crude mixture of 13 after a 2.5 h reaction with 7 to yield 15, (d) chromatogram of the one-pot synthesis of 15 after a 20 h reaction with BCN-NODAGA, (e) chromatogram of 18 after final purification. Vertical axis represents relative absorbance at 260 nm with the exception of (a), which was recorded at 214 nm due to the lack of absorbance of 9 at 260 nm. See Supporting Information for detailed information on the gradient and analytical system.
Figure 5
Figure 5
(A) The images show the maximum intensity projections recorded between 50 and 70 min p.i. of [68Ga]Ga-AMBA (A, left); [68Ga]Ga-PSMA11 (A, middle); and [68Ga]Ga-18 (A, right). (B) The images show the axial images VOI analysis around both PC3 and 22Rv1 tumors, and the heart as a blood pool background. Signal seen on the heads of the mice is due to retro-orbital injection.
Figure 6
Figure 6
Biodistribution of [68Ga]Ga-18 at 2 h p.i. in nude mice xenografted with PC3 and 22Rv1 cells. Data points show mean ± SEM n = 2–5; for values of all collected tissues and tumor-to-tissue ratios, see the Supporting Information.
See this image and copyright information in PMC

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