Alley Stephen C, Benjamin Dennis R, Jeffrey Scott C, Okeley Nicole M, Meyer Damon L, Sanderson Russell J, Senter Peter D
Seattle Genetics, Inc., 21823 30th Drive SE, Bothell, WA 98021, USA.
Bioconjug Chem. 2008 Mar;19(3):759-65. doi: 10.1021/bc7004329. Epub 2008 Mar 4.
The linker component of antibody-drug conjugates (ADC) is a key feature in developing optimized therapeutic agents that are highly active at well tolerated doses. For maximal intratumoral drug delivery, linkers are required that are highly stable in the systemic circulation, yet allow for efficient drug release at the target site. In this respect, amide bond-based technologies constitute a technological advancement, since the linker half-lives in circulation ( t 1/2 approximately 7 days) are much longer than earlier generation linkers that break down within 1-2 days. The amide linkers, some of which contain peptides, are appended to the mAb carriers through thioether/maleimide adducts. Here, we describe that use of a bromoacetamidecaproyl (bac) in place of the maleimidocaproyl (mc) increases the plasma stability of resulting thioether ADCs. One such ADC, 1F6-C4v2-bac-MMAF, which is directed against the CD70 antigen on lymphomas and renal cell carcinoma, was prepared containing a bac thioether spacer between the drug (MMAF) and the mAb carrier (1F6-C4v2). There was no measurable systemic drug release from this ADC for 2 weeks postadministration in mice. In order to assess the impact of improving linker stability beyond mc containing ADCs, a series of mc and bac-linked 1F6-MMAF conjugates were compared for tolerability, intratumoral drug delivery, and therapeutic efficacy in nude mice with renal cell carcinoma xenografts. There were no statistically significant efficacy differences between sets of mc and bac containing ADCs, although the bac linker technology led to 25% higher intratumoral drug exposure over a 7 day period compared to the corresponding mc linker. The mechanism of drug release from maleimide-adducts likely involves a retro-Michael reaction that takes place in plasma, based on in vitro studies demonstrating that some of the released drug-maleimide derivative became covalently bound to cysteine-34 of serum albumin. In summary, the data indicate that new linkers can be obtained with improved in vivo stability by replacing the maleimide with an acetamide, but the resulting ADCs had similar tolerability and activity profiles.
抗体药物偶联物（ADC）的连接子组件是开发在良好耐受剂量下具有高活性的优化治疗药物的关键特性。为了实现最大程度的肿瘤内药物递送，需要连接子在体循环中高度稳定，但又能在靶位点实现高效的药物释放。在这方面，基于酰胺键的技术是一项技术进步，因为连接子在循环中的半衰期（t1/2约为7天）比在1 - 2天内就会分解的早期连接子长得多。一些含有肽的酰胺连接子通过硫醚/马来酰亚胺加合物连接到单克隆抗体载体上。在此，我们描述了用溴乙酰胺己酰基（bac）代替马来酰亚胺己酰基（mc）可提高所得硫醚ADC的血浆稳定性。制备了一种这样的ADC，即1F6 - C4v2 - bac - MMAF，它靶向淋巴瘤和肾细胞癌上的CD70抗原，在药物（MMAF）和单克隆抗体载体（1F6 - C4v2）之间含有一个bac硫醚间隔区。在小鼠给药后2周内，该ADC没有可测量到的全身药物释放。为了评估提高连接子稳定性对含mc的ADC的影响，比较了一系列mc和bac连接的1F6 - MMAF偶联物在肾细胞癌异种移植裸鼠中的耐受性、肿瘤内药物递送和治疗效果。含mc和含bac的ADC组之间在疗效上没有统计学上的显著差异，尽管与相应的mc连接子相比，bac连接子技术在7天内导致肿瘤内药物暴露量高出25%。基于体外研究表明一些释放的药物 - 马来酰亚胺衍生物与血清白蛋白的半胱氨酸 - 34共价结合，从马来酰亚胺加合物释放药物的机制可能涉及在血浆中发生的逆迈克尔反应。总之，数据表明通过用乙酰胺代替马来酰亚胺可以获得体内稳定性得到改善的新连接子，但所得的ADC具有相似的耐受性和活性特征。
