Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, 2100 Copenhagen, Denmark.
Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark.
Bioconjug Chem. 2022 Apr 20;33(4):608-624. doi: 10.1021/acs.bioconjchem.2c00042. Epub 2022 Mar 15.
Tetrazines (Tz) have been applied as bioorthogonal agents for various biomedical applications, including pretargeted imaging approaches. In radioimmunoimaging, pretargeting increases the target-to-background ratio while simultaneously reducing the radiation burden. We have recently reported a strategy to directly F-label highly reactive tetrazines based on a 3-(3-fluorophenyl)-Tz core structure. Herein, we report a kinetic study on this versatile scaffold. A library of 40 different tetrazines was prepared, fully characterized, and investigated with an emphasis on second-order rate constants for the reaction with -cyclooctene (TCO). Our results reveal the effects of various substitution patterns and moreover demonstrate the importance of measuring reactivities in the solvent of interest, as click rates in different solvents do not necessarily correlate well. In particular, we report that tetrazines modified in the 2-position of the phenyl substituent show high intrinsic reactivity toward TCO, which is diminished in aqueous systems by unfavorable solvent effects. The obtained results enable the prediction of the bioorthogonal reactivity and thereby facilitate the development of the next generation of substituted aryltetrazines for applications.
叠氮化物（Tz）已被应用于各种生物医学应用，包括靶向成像方法。在放射免疫成像中，预靶向可以提高靶标与背景的比率，同时降低辐射负担。我们最近报道了一种基于 3-(3-氟苯基）-Tz 核心结构的直接 F 标记高反应性 Tz 的策略。在此，我们报告了对这种多功能支架的动力学研究。我们制备了 40 种不同的 Tz 库，对其进行了全面的表征，并重点研究了与 -环辛烯（TCO）的反应的二级速率常数。我们的结果揭示了各种取代模式的影响，并且还证明了在感兴趣的溶剂中测量反应性的重要性，因为不同溶剂中的点击速率不一定很好地相关。特别是，我们报告说，在苯基取代基的 2 位修饰的 Tz 对 TCO 表现出高固有反应性，但在水体系中由于不利的溶剂效应而降低。所得结果能够预测生物正交反应性，从而促进下一代用于应用的取代芳基 Tz 的开发。
