抑制过表达酶是针对癌症治疗最有前途的方法之一。然而，许多癌细胞产生的酶是“非致死性”的，即抑制酶的活性还不足以杀死癌细胞。常规的抗体治疗方法可以通过靶向细胞外的非致死性靶点来有效治疗，但很难对靶向细胞内的酶。在此，我们报告了一种肿瘤靶向治疗策略，该策略通过选择性标记癌干细胞（CSC）和Click化学介导的药物传递来利用细胞内的非致死性酶。一种新设计的化合物，AAMCHO（N-(3,4,6-三乙酰基-N-azido乙酰甘露糖胺)-顺-2-乙基-3-甲酰基丙烯酰胺糖甙），通过细胞内醛脱氢酶1A1的酶促氧化选择性地标记癌症CSC，在体外和体内都能实现。值得注意的是，与CD44等内源性标志物相比，氮化物标记在鉴定肿瘤发生性细胞群中更高效。二苯并环辛炔（DBCO）-毒素偶联物，DBCO-MMAE（单甲基金丝黄素E），可以通过生物正交的Click反应靶向标记的CSC，在体内对一系列肿瘤模型，包括原位异种移植瘤、耐药肿瘤和肺转移瘤，实现优异的抗癌效果，并具有低毒性。在一个晚期三阴性乳腺癌异种移植瘤（体积约500 mm3）经过单周期治疗后，观察到5/7完全缓解。

Inhibition of overexpressed enzymes is among the most promising approaches for targeted cancer treatment. However, many cancer-expressed enzymes are "nonlethal," in that the inhibition of the enzymes' activity is insufficient to kill cancer cells. Conventional antibody-based therapeutics can mediate efficient treatment by targeting extracellular nonlethal targets but can hardly target intracellular enzymes. Herein, we report a cancer targeting and treatment strategy to utilize intracellular nonlethal enzymes through a combination of selective cancer stem-like cell (CSC) labeling and Click chemistry-mediated drug delivery. A de novo designed compound, AAMCHO [N-(3,4,6-triacetyl- N-azidoacetylmannosamine)-cis-2-ethyl-3-formylacrylamideglycoside], selectively labeled cancer CSCs in vitro and in vivo through enzymatic oxidation by intracellular aldehyde dehydrogenase 1A1. Notably, azide labeling is more efficient in identifying tumorigenic cell populations than endogenous markers such as CD44. A dibenzocyclooctyne (DBCO)-toxin conjugate, DBCO-MMAE (Monomethylauristatin E), could next target the labeled CSCs in vivo via bioorthogonal Click reaction to achieve excellent anticancer efficacy against a series of tumor models, including orthotopic xenograft, drug-resistant tumor, and lung metastasis with low toxicity. A 5/7 complete remission was observed after single-cycle treatment of an advanced triple-negative breast cancer xenograft (~500 mm3).