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

Abstract

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 “bystander effect” 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 L-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 (mil40-15) not only exhibits ideal plasma stability and maintains potent cytotoxicity as MMAE (IC50: 10−11 M), but also shows improved safety with lower bystander toxicity (IC50: 10−9 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.

Small Molecule-Based Prodrug Targeting Prostate Specific Membrane Antigen for the Treatment of Prostate Cancer

“…Conversely, the greatest advantage of the noncleavable linkers is their increased plasma stability [ 63 ]. Recently, antitumor activities of MMAE based ADCs with noncleavable linker have been reported [ 64 , 65 ] and it was found that complete lysosomal proteolytic degradation of the antibody is required to generate toxic payloads for ADCs with noncleavable linker. In this study, we used our PSMA-1 ligand to deliver MMAE to PSMA-expressing prostate cancer cells.…”

Antibody–drug conjugates: Recent advances in linker chemistry

“…Adapted with modification from Ref. 59 © 2017 American Chemical Society. (C) The structure of noncleavable linker-MMAE-containing ADCs.…”

“…Based on this, our group developed a noncleavable ADC with MMAE as the payload, which could broaden the therapeutic window of MMAE-based ADCs ( Fig. 10 C) 59 . The active part of the noncleavable ADC ( l -cysteine (Cys)-linker-MMAE) not only exhibited similar cytotoxicity to that of MMAE (IC 50 : 10 −11 mol/L), but also reduced toxicity in the bystander effect test.…”

Recent Advances in Drug–Antibody Ratio Determination of Antibody–Drug Conjugates

“…8,9) Although many analytical chemists have reported unique methodologies in the scientific literature that are geared toward the establishment of a gold standard technique for DAR characterization, challenges remain because of the structural complexity, diversity and heterogeneity of ADCs. 7,10) In addition to heterogeneity due to conjugation methodology as described above, there is antibody-related issue to be considered. Naked antibodies, starting material of ADCs, are usually produced as complex mixtures of Fc glycoforms.…”