PET显像是使用标记89Zr的单克隆抗体（mAb）的主要挑战之一，其血液循环时间长，导致高背景信号，降低图像质量。为了克服这一限制，我们报道了一种生物正交连接断裂方法（click-to-release化学）来选择性地释放來自转环辛烯功能化曲妥珠单抗（TCO-Tmab）的[89Zr]Zr-DFO，通过在BT-474肿瘤携带的小鼠中给予四氮唑化合物（触发剂）作用于血液中。方法：我们构建了一系列TCO-DFO结构，并使用不同的触发剂化合物评价了它们在体外从Tmab释放[89Zr]Zr-DFO的性能。先在健康小鼠中研究了最佳[89Zr]Zr-TCO-Tmab的体内行为以确定触发剂的最佳剂量。为了找到最佳的触发剂给药时间，研究了[89Zr]Zr-TCO-Tmab在BT-474癌细胞中的内化速率。最后，在给予[89Zr]Zr-TCO-Tmab后的6小时或24小时将触发剂给予携带肿瘤的小鼠，以释放[89Zr]Zr-DFO碎片。PET扫描显示了在触发剂给予后6小时的携带肿瘤小鼠中的肿瘤摄取，与由于释放的[89Zr]Zr-DFO含有物从通过肾脏的循环中迅速清除而导致的强烈降低的背景。结果：具有最佳体内性能的[89Zr]Zr-TCO-Tmab和触发剂对在50％小鼠血浆中释放83％。在携带肿瘤的小鼠中，当触发剂在mAb后的6小时和24小时给予时，肿瘤血比显著增加，分别从1.0±0.4增加到2.3±0.6（p=0.0057）和从2.5±0.7增加到6.6±0.9（p<0.0001）。同一天的PET显像清晰地显示了肿瘤的摄取以及由于释放的[89Zr]Zr-DFO含有物从循环中快速清除而导致的背景降低。结论：这是第一个证明在小鼠中使用转环辛烯-四氮唑click-to-release化学来释放来自mAb的放射性螯合物，以增加肿瘤与血液的比率。我们的结果表明click可断裂的放射免疫显像技术可能允许PET显像中使用全mAb的时间间隔大大缩短，减少辐射剂量，甚至可能实现同日显像。©作者。

One of the main challenges of PET imaging with 89Zr-labeled monoclonal antibodies (mAbs) remains the long blood circulation of the radiolabeled mAbs, leading to high background signals, decreasing image quality. To overcome this limitation, here we report the use of a bioorthogonal linker cleavage approach (click-to-release chemistry) to selectively liberate [89Zr]Zr-DFO from trans-cyclooctene-functionalized trastuzumab (TCO-Tmab) in blood, following the administration of a tetrazine compound (trigger) in BT-474 tumor-bearing mice. Methods: We created a series of TCO-DFO constructs and evaluated their performance in [89Zr]Zr-DFO release from Tmab in vitro using different trigger compounds. The in vivo behavior of the best performing [89Zr]Zr-TCO-Tmab was studied in healthy mice first to determine the optimal dose of the trigger. To find the optimal time for the trigger administration, the rate of [89Zr]Zr-TCO-Tmab internalization was studied in BT-474 cancer cells. Finally, the trigger was administered 6 h or 24 h after [89Zr]Zr-TCO-Tmab- administration in tumor-bearing mice to liberate the [89Zr]Zr-DFO fragment. PET scans were obtained of tumor-bearing mice that received the trigger 6 h post-[89Zr]Zr-TCO-Tmab administration. Results: The [89Zr]Zr-TCO-Tmab and trigger pair with the best in vivo properties exhibited 83% release in 50% mouse plasma. In tumor-bearing mice the tumor-blood ratios were markedly increased from 1.0 ± 0.4 to 2.3 ± 0.6 (p = 0.0057) and from 2.5 ± 0.7 to 6.6 ± 0.9 (p < 0.0001) when the trigger was administered at 6 h and 24 h post-mAb, respectively. Same day PET imaging clearly showed uptake in the tumor combined with a strongly reduced background due to the fast clearance of the released [89Zr]Zr-DFO-containing fragment from the circulation through the kidneys. Conclusions: This is the first demonstration of the use of trans-cyclooctene-tetrazine click-to-release chemistry to release a radioactive chelator from a mAb in mice to increase tumor-to-blood ratios. Our results suggest that click-cleavable radioimmunoimaging may allow for substantially shorter intervals in PET imaging with full mAbs, reducing radiation doses and potentially even enabling same day imaging.© The author(s).