Site-Specific Trastuzumab Maytansinoid Antibody–Drug Conjugates with Improved Therapeutic Activity through Linker and Antibody Engineering

Abstract

Antibody-drug conjugates (ADCs) have a significant impact toward the treatment of cancer, as evidenced by the clinical activity of the recently approved ADCs, brentuximab vedotin for Hodgkin lymphoma and ado-trastuzumab emtansine (trastuzumab-MCC-DM1) for metastatic HER2+ breast cancer. DM1 is an analog of the natural product maytansine, a microtubule inhibitor that by itself has limited clinical activity and high systemic toxicity. However, by conjugation of DM1 to trastuzumab, the safety was improved and clinical activity was demonstrated. Here, we report that through chemical modification of the linker-drug and antibody engineering, the therapeutic activity of trastuzumab maytansinoid ADCs can be further improved. These improvements include eliminating DM1 release in the plasma and increasing the drug load by engineering four cysteine residues into the antibody. The chemical synthesis of highly stable linker-drugs and the modification of cysteine residues of engineered site-specific antibodies resulted in a homogeneous ADC with increased therapeutic activity compared to the clinically approved ADC, trastuzumab-MCC-DM1.

Site-specific protein modification using immobilized sortase in batch and continuous-flow systems

“…For example, PEGylation, while increasing circulatory half-life 1 , may cause a decrease or even loss of biological activity due to the chemical modification(s) imposed 2 . Such results have also been observed when preparing antibody-drug conjugates 3 . Heterogeneity after labeling may confound accurate dosing and complicate drug approval and pharmaceutical production.…”

Antibody Drug Conjugates for Cancer Therapy

“…Here, the resulting drug retains the linker plus a cysteine residue derived from the antibody (Doronina et al, 2006). It should be noted that although the MCC and MC linkers described here do not contain a cleavable bond, a retro-Michael reaction involving the malemide moiety is possible and can result in deconjugation of drug from antibody in vivo or in other matrices (Alley et al, 2008;Pillow et al, 2014).…”

In Vivo Biotransformations of Antibody–Drug Conjugates

“…To address this issue, Pillow and colleagues from Genentech engineered cysteine residues which were employed to generate site-specific conjugates allowing for a more homogeneous loading profile [61]. They reported a series of T-DM1 analogs by maleimide-thiol conjugation which are expected to release the cys-capped linker payload upon ADC catabolism.…”