Brind Thomasin, Lawer Aggie, Todd Tobias, Aryal Sushant, Hook Sarah, Gamble Allan B
School of Pharmacy, University of Otago, 18 Frederick Street, Dunedin, 9054, New Zealand.
Chemistry. 2025 Jul 25;31(42):e202501544. doi: 10.1002/chem.202501544. Epub 2025 Jul 2.
Bioorthogonal click-to-release prodrug activation strategies should be fast and high yielding. However, in strain-promoted alkene-azide click-to-release, a fast click-step translates to slow and inefficient drug release. To improve drug yield, branched dual-core scaffolds that increase drug release are reported. The dual-core consists of an exposed electron-deficient aryl azide (core-1) attached to an electron-rich self-immolating branched linker (core-2). Core-1, a tetrafluoroaryl azide with methyl-substitution at the benzylic carbon, facilitates a rapid click reaction with trans-cyclooctenes (TCOs). Core-2 had an N-methyl carbamate or ether linker and a 1,4/1,4- or 1,4/1,6-self-immolating scaffold. Various release rates of a fluorophore were observed across the series, with 1,4/1,6-self-immolating core-2, linked via the N-methyl carbamate, having sustained and enhanced fluorophore release. The second-order rate constant for cycloaddition of this 1,4/1,6-self-immolating analogue and d-TCO is, to the best of our knowledge, the fastest to date (22.0 M s). A persistent intermediate was observed, leading to a long, sustained release of fluorophore from the branched scaffold, though activation under acidic conditions (pH = 5.5) led to ≈ 15% higher fluorophore release compared to activation at pH 7.4. Therefore, combinations of core-1 and core-2 could improve future pretargeted in vivo bioorthogonal click-to-release prodrug strategies, especially in the acidic tumor environment.
生物正交点击释放前药激活策略应快速且产率高。然而，在应变促进的烯烃 - 叠氮化物点击释放中，快速的点击步骤会导致缓慢且低效的药物释放。为了提高药物产率，报道了可增加药物释放的支链双核支架。双核由连接到富电子自毁支链连接体（核心 - 2）上的暴露缺电子芳基叠氮化物（核心 - 1）组成。核心 - 1是在苄基碳处有甲基取代的四氟芳基叠氮化物，促进与反式环辛烯（TCO）的快速点击反应。核心 - 2具有N - 甲基氨基甲酸酯或醚连接体以及1,4/1,4 - 或1,4/1,6 - 自毁支架。在整个系列中观察到荧光团的各种释放速率，通过N - 甲基氨基甲酸酯连接的1,4/1,6 - 自毁核心 - 2具有持续且增强的荧光团释放。据我们所知，这种1,4/1,6 - 自毁类似物与d - TCO环加成反应二阶速率常数是迄今为止最快的（22.0 M⁻¹ s⁻¹）。观察到一个持久中间体，导致荧光团从支链支架中长时间持续释放，不过在酸性条件（pH = 5.5）下激活比在pH 7.4下激活导致荧光团释放高出约15%。因此，核心 - 1和核心 - 2的组合可以改善未来体内预靶向生物正交点击释放前药策略，特别是在酸性肿瘤环境中。
