Tilman Läppchen1, Raffaella Rossin2, Tiemen R van Mourik3, Guillaume Gruntz3, Freek J M Hoeben4, Ron M Versteegen4, Henk M Janssen4, Johan Lub3, Marc S Robillard5. 1. Philips Research, High Tech Campus 11, 5656 AE Eindhoven, The Netherlands; Department of Nuclear Medicine, Medical Center- University of Freiburg, Faculty of Medicine, University of Freiburg, Hugstetterstrasse 55, 79106 Freiburg, Germany; Department of Nuclear Medicine, Inselspital, Bern University Hospital and University of Bern, Freiburgstrasse, 3010 Bern, Switzerland. 2. Philips Research, High Tech Campus 11, 5656 AE Eindhoven, The Netherlands; Tagworks Pharmaceuticals BV, c/o Department of Nuclear Medicine and Radiology, Radboud University Medical Center, 6500 HB Nijmegen, The Netherlands. 3. Philips Research, High Tech Campus 11, 5656 AE Eindhoven, The Netherlands. 4. SyMO-Chem BV, Den Dolech 2, 5612 AZ, Eindhoven, The Netherlands. 5. Philips Research, High Tech Campus 11, 5656 AE Eindhoven, The Netherlands; Tagworks Pharmaceuticals BV, c/o Department of Nuclear Medicine and Radiology, Radboud University Medical Center, 6500 HB Nijmegen, The Netherlands. Electronic address: marc.robillard@tagworkspharma.com.
Abstract
INTRODUCTION: Pretargeted radioimmunoimaging and -therapy approaches building on the bioorthogonal inverse-electron-demand Diels-Alder (IEDDA) reaction between strained trans-cyclooctenes (TCO) and electron-deficient tetrazines (Tz) have yielded impressive results in recent years and have proven a vital alternative to biological pretargeting systems. After improvement of the TCO-antibody conjugates, we here report on our evaluation of a new series of radiolabeled Tz-probes. METHODS: Four new Tz-probes were synthesized, radiolabeled with lutetium-177, and characterized in vitro in terms of lipophilicity, reactivity, and stability in PBS and mouse serum. The in vivo biodistribution profile and tumor-targeting potential of the probes were evaluated in LS174T tumor-bearing mice pretargeted with TCO-antibody conjugates using non-pretargeted mice as control. RESULTS: Radiolabeling of all probes proceeded in high yields providing the 177Lu-labeled tetrazines in >95% radiochemical purity without any further purification. In mouse serum, half-lives of the probes varied between 8 and 13 h, with the exception of the most lipophilic probe, [177Lu]1b, with a serum half-life of less than 1 h. This probe also showed the fastest blood clearance (t1/2 = 5.4 min), more than 2-fold faster than PEG-linked probes [177Lu]3 and [177Lu]4, and even 3-fold faster than the other small probes without the PEG-linker, [177Lu]1a and [177Lu]2. In the pretargeting experiments, tumor uptake of the lead probe [177Lu]4 (~6 %ID/g) was most closely approached by [177Lu]2, followed by [177Lu]3 and [177Lu]1a. While all the smaller and more lipophilic probes suffered from increased liver uptake, the PEG-linked probe [177Lu]3 with its additional negative charge surprisingly showed the highest kidney uptake among all of the probes. CONCLUSION: The in vitro performance of some of the new tetrazine probes turned out to be comparable to the established lead probe [177Lu]Lu-DOTA-PEG11-Tz ([177Lu]4). However, tumor pretargeting studies in vivo showed lower tumor uptake and increased uptake in non-target organs.
INTRODUCTION: Pretargeted radioimmunoimaging and -therapy approaches building on the bioorthogonal inverse-electron-demand Diels-Alder (IEDDA) reaction between strained trans-cyclooctenes (TCO) and electron-deficient tetrazines (Tz) have yielded impressive results in recent years and have proven a vital alternative to biological pretargeting systems. After improvement of the TCO-antibody conjugates, we here report on our evaluation of a new series of radiolabeled Tz-probes. METHODS: Four new Tz-probes were synthesized, radiolabeled with lutetium-177, and characterized in vitro in terms of lipophilicity, reactivity, and stability in PBS and mouse serum. The in vivo biodistribution profile and tumor-targeting potential of the probes were evaluated in LS174T tumor-bearing mice pretargeted with TCO-antibody conjugates using non-pretargeted mice as control. RESULTS: Radiolabeling of all probes proceeded in high yields providing the 177Lu-labeled tetrazines in >95% radiochemical purity without any further purification. In mouse serum, half-lives of the probes varied between 8 and 13 h, with the exception of the most lipophilic probe, [177Lu]1b, with a serum half-life of less than 1 h. This probe also showed the fastest blood clearance (t1/2 = 5.4 min), more than 2-fold faster than PEG-linked probes [177Lu]3 and [177Lu]4, and even 3-fold faster than the other small probes without the PEG-linker, [177Lu]1a and [177Lu]2. In the pretargeting experiments, tumor uptake of the lead probe [177Lu]4 (~6 %ID/g) was most closely approached by [177Lu]2, followed by [177Lu]3 and [177Lu]1a. While all the smaller and more lipophilic probes suffered from increased liver uptake, the PEG-linked probe [177Lu]3 with its additional negative charge surprisingly showed the highest kidney uptake among all of the probes. CONCLUSION: The in vitro performance of some of the new tetrazine probes turned out to be comparable to the established lead probe [177Lu]Lu-DOTA-PEG11-Tz ([177Lu]4). However, tumor pretargeting studies in vivo showed lower tumor uptake and increased uptake in non-target organs.
Authors: Jan-Philip Meyer; Kathryn M Tully; James Jackson; Thomas R Dilling; Thomas Reiner; Jason S Lewis Journal: Bioconjug Chem Date: 2018-02-09 Impact factor: 4.774
Authors: Song Yu; Hans M de Bruijn; Dennis Svatunek; Trevor A Hamlin; F Matthias Bickelhaupt Journal: ChemistryOpen Date: 2018-11-26 Impact factor: 2.911