Antibody-Drug Conjugate Using Ionized Cys-Linker-MMAE as the Potent Payload Shows Optimal Therapeutic Safety

• Main Authors: Yanming Wang, Lianqi Liu, Shiyong Fan, Dian Xiao, Fei Xie, Wei Li, Wu Zhong, Xinbo Zhou
• Format: Article
• Language: English
• Published: MDPI AG 2020-03-01
• Series: Cancers
• Subjects: tumor; antibody-drug conjugate; linker; mmae; cys-linker-mmae
• Online Access: https://www.mdpi.com/2072-6694/12/3/744

Monomethyl auristatin E (MMAE) is the most popular and widely used cytotoxin in the development of antibody-drug conjugates (ADCs). However, current MMAE-based ADCs are all constructed using cleavable linkers, and this design concept still has insurmountable drawbacks. Their potential instabilities and lipophilic MMAE-induced &#8220;bystander effect&#8221; inevitably increase the toxicity to normal tissues. Herein, we overturn previous negative views of MMAE-based ADCs with non-cleavable linkers and propose using ionized <i>L</i>-Cysteine (Cys)-linker-MMAE as a novel payload, which can ingeniously enrich and enter tumor cells through receptor-mediated endocytosis of antibodies while its lower permeability helps to avoid further off-target toxicity. We demonstrate that Cys-linker-MMAE maintains high potency similar to free MMAE at the tubulin molecular level and can also be efficiently released in target cells. As a result, the preferred ADC (mil40-<b>15</b>) not only exhibits ideal plasma stability and maintains potent cytotoxicity as MMAE (IC₅₀: 10^&#8722;11 M), but also shows improved safety with lower bystander toxicity (IC₅₀: 10^&#8722;9 M), its maximum tolerated dose approaching the level of the naked antibody (160 mg/kg). This study indicated that Cys-linker-MMAE has the potential as a potent payload for ADCs, which is expected to provide novel strategies for the development of MMAE-based ADCs.