Elgersma Ronald C, Coumans Ruud G E, Huijbregts Tijl, Menge Wiro M P B, Joosten John A F, Spijker Henri J, de Groot Franciscus M H, van der Lee Miranda M C, Ubink Ruud, van den Dobbelsteen Diels J, Egging David F, Dokter Wim H A, Verheijden Gijs F M, Lemmens Jacques M, Timmers C Marco, Beusker Patrick H
Mol Pharm. 2015 Jun 1;12(6):1813-35. doi: 10.1021/mp500781a. Epub 2015 Feb 18.
Antibody-drug conjugates (ADCs) that are currently on the market or in clinical trials are predominantly based on two drug classes: auristatins and maytansinoids. Both are tubulin binders and block the cell in its progression through mitosis. We set out to develop a new class of linker-drugs based on duocarmycins, potent DNA-alkylating agents that are composed of a DNA-alkylating and a DNA-binding moiety and that bind into the minor groove of DNA. Linker-drugs were evaluated as ADCs by conjugation to the anti-HER2 antibody trastuzumab via reduced interchain disulfides. Duocarmycin 3b, bearing an imidazo[1,2-a]pyridine-based DNA-binding unit, was selected as the drug moiety, notably because of its rapid degradation in plasma. The drug was incorporated into the linker-drugs in its inactive prodrug form, seco-duocarmycin 3a. Linker attachment to the hydroxyl group in the DNA-alkylating moiety was favored over linking to the DNA-binding moiety, as the first approach gave more consistent results for in vitro cytotoxicity and generated ADCs with excellent human plasma stability. Linker-drug 2 was eventually selected based on the properties of the corresponding trastuzumab conjugate, SYD983, which had an average drug-to-antibody ratio (DAR) of about 2. SYD983 showed subnanomolar potencies against multiple human cancer cell lines, was highly efficacious in a BT-474 xenograft model, and had a long half-life in cynomolgus monkeys, in line with high stability in monkey and human plasma. Studies comparing ADCs with a different average DAR showed that a higher average DAR leads to increased efficacy but also to somewhat less favorable physicochemical and toxicological properties. Fractionation of SYD983 with hydrophobic interaction chromatography resulted in SYD985, consisting of about 95% DAR2 and DAR4 species in an approximate 2:1 ratio and having an average DAR of about 2.8. SYD985 combines several favorable properties from the unfractionated ADCs with an improved homogeneity. It was selected for further development and recently entered clinical Phase I evaluation.
目前已上市或处于临床试验阶段的抗体药物偶联物（ADC）主要基于两类药物：奥瑞他汀和美登素类。这两类药物均为微管蛋白结合剂，可在有丝分裂过程中阻止细胞进程。我们着手研发一类基于双吲哚霉素的新型连接体药物，双吲哚霉素是一种强效DNA烷基化剂，由一个DNA烷基化部分和一个DNA结合部分组成，能结合到DNA小沟中。通过还原链间二硫键与抗HER2抗体曲妥珠单抗偶联，将连接体药物评估为ADC。带有咪唑并[1,2 - a]吡啶基DNA结合单元的双吲哚霉素3b被选为药物部分，特别是因为它在血浆中能快速降解。该药物以其无活性的前药形式，即开环双吲哚霉素3a，被纳入连接体药物中。连接体与DNA烷基化部分中的羟基连接比与DNA结合部分连接更受青睐，因为第一种方法在体外细胞毒性方面能给出更一致的结果，并生成在人血浆中具有优异稳定性的ADC。最终基于相应曲妥珠单抗偶联物SYD983的性质选择了连接体药物2，其平均药物与抗体比率（DAR）约为2。SYD983对多种人类癌细胞系显示出亚纳摩尔级的效力，在BT - 474异种移植模型中具有高效性，并且在食蟹猴体内具有较长的半衰期，这与在猴和人血浆中的高稳定性一致。比较不同平均DAR的ADC的研究表明，较高的平均DAR会导致疗效增加，但也会使物理化学和毒理学性质略逊一筹。用疏水相互作用色谱法对SYD983进行分级分离得到了SYD985，其由约95%的DAR2和DAR4物种组成，比例约为2:1，平均DAR约为2.8。SYD985结合了未分级ADC的几种有利性质，同时具有更高的均一性。它被选中进行进一步开发，最近进入了临床I期评估。
