Bis(vinylsulfonyl)piperazines as efficient linkers for highly homogeneous antibody-drug conjugates

Bispecific Antibodies Produced via Chemical Site-Specific Conjugation Technology: AJICAP Second-Generation

Bispecific antibodies (BisAbs) are biotherapeutics that amalgamate the specificities of two distinct antibodies into one molecule, however, their engineering requires genetic modification and remains time-consuming. Therefore, we used AJICAP second-generation technology, which drives the production of site-specific conjugation without genetic modification requirements, to generate BisAbs. Using haloketone chemistry as an alternative to maleimide chemistry, we successfully produced site-specific antibody conjugates. Pharmacokinetic studies revealed that the haloketone-based antibody conjugate was stable in the rat plasma. The resultant BisAbs were rigorously evaluated, and surface plasmon resonance measurements and flow cytometry analyses confirmed that the antigen binding remained intact. Additionally, the affinity for the neonatal Fc receptor (FcRn) was retained after conjugation. Further cytotoxicity evaluation emphasized the pronounced activity of the generated BisAbs. This novel approach introduces a fully chemical, site-specific strategy capable of producing BisAbs, heralding a new era in the field of biotherapeutics.

Development of a MMAE-based antibody-drug conjugate targeting B7-H3 for glioblastoma

B7-H3 (immunoregulatory protein B7-homologue 3) is overexpressed in many cancer cells with limited expression in normal tissues, considered to be a promising target for tumor therapeutics. Clinical trials of antibody-drug conjugates (ADCs) against different targets for glioblastoma have been investigated and showed potent efficacies. In this study, we developed a homogeneous ADC 401-4 with a drug-to-antibody ratio (DAR) of 4, which was prepared by conjugation of Monomethyl auristatin E (MMAE) to a humanized anti-B7-H3 mAb 401, through a divinylsulfonamide-mediated disulfide re-bridging approach. In vitro studies, 401-4 displayed specific killing against B7-H3-expressing tumors and was more effective in cells with higher levels of B7-H3 for different glioblastoma cells. 401-4 was furthered labeled with Cy5.5 to yield a fluorescent conjugate 401-4-Cy5.5. The in vivo imaging studies showed that the conjugate accumulated in tumor regions and exhibited the ability to target-specific delivery. In addition, significant antitumor activities for 401-4 was observed against U87-derived tumor xenografts in a dose dependent manner.

Phenyldivinylsulfonamides for the construction of antibody-drug conjugates with controlled four payloads

Phenyldivinylsulfonamides emerged from a series of divinylsulfonamides, demonstrating their ability to effectively re-bridge disulfide bonds. This kind of linkers was attached to monomethyl auristatin E (MMAE) and further conjugated with a model antibody, trastuzumab. After optimization, the linker 20 can deliver stable and highly homogenous DAR (Drug-to-Antibody Ratio) four antibody-drug conjugates (ADCs). The method was also applicable for other IgG1 antibodies to obtain ADCs with controlled four payloads. Moreover, the MMAE-bearing ADC is potent, selective and efficacious against target cell lines.

Chemical modification of proteins - challenges and trends at the start of the 2020s

Ribosomally expressed proteins perform multiple, versatile, and specialized tasks throughout Nature. In modern times, chemically modified proteins, including improved hormones, enzymes, and antibody-drug-conjugates have become available and have found advanced industrial and pharmaceutical applications. Chemical modification of proteins is used to introduce new functionalities, improve stability or drugability. Undertaking chemical reactions with proteins without compromising their native function is still a core challenge as proteins are large conformation dependent multifunctional molecules. Methods for functionalization ideally should be chemo-selective, site-selective, and undertaken under biocompatible conditions in aqueous buffer to prevent denaturation of the protein. Here the present challenges in the field are discussed and methods for modification of the 20 encoded amino acids as well as the N-/C-termini and protein backbone are presented. For each amino acid, common and traditional modification methods are presented first, followed by more recent ones.

Site-specific construction of triptolide-based antibody-drug conjugates

Antibody-drug conjugates (ADCs) have emerging as efficient agents to target deliver cytotoxic drugs and reduce their off-target side effects. Triptolide has attracted attention to be used in ADC development. Herein, three rationally designed triptolide drug-linkers have been synthesized for use in site-specific construction of ADCs. Carbamates that were supposed to be more stable than carbonates were introduced to attach triptolide to the linkers. PEG and discrete PEG chains were incorporated to improve the hydrophilicity of drug-linkers. The ADCs were finally site-specifically prepared by conjugation of the drug-linkers to trastuzumab through disulfide re-bridging approach. The preliminary anti-tumor activities of these ADCs were evaluated and they displayed high potencies against HER2-targeted cancer in vitro and in vivo.

Antibody-drug conjugates: Recent advances in linker chemistry

Antibody–drug conjugates (ADCs) are gradually revolutionizing clinical cancer therapy. The antibody–drug conjugate linker molecule determines both the efficacy and the adverse effects, and so has a major influence on the fate of ADCs. An ideal linker should be stable in the circulatory system and release the cytotoxic payload specifically in the tumor. However, existing linkers often release payloads nonspecifically and inevitably lead to off-target toxicity. This defect is becoming an increasingly important factor that restricts the development of ADCs. The pursuit of ADCs with optimal therapeutic windows has resulted in remarkable progress in the discovery and development of novel linkers. The present review summarizes the advance of the chemical trigger, linker‒antibody attachment and linker‒payload attachment over the last 5 years, and describes the ADMET properties of ADCs. This work also helps clarify future developmental directions for the linkers.

Strategies and Applications of Antigen-Binding Fragment (Fab) Production in Escherichia coli

With the advancement of genetic engineering, monoclonal antibodies (mAbs) have made far-reaching progress in the treatment of various human diseases. However, due to the high cost of production, the increasing demands for antibody-based therapies have not been fully met. Currently, mAb-derived alternatives, such as antigen-binding fragments (Fab), single-chain variable fragments, bispecifics, nanobodies, and conjugated mAbs have emerged as promising new therapeutic modalities. They can be readily prepared in bacterial systems with well-established fermentation technology and ease of manipulation, leading to the reduction of overall cost. This review aims to shed light on the strategies to improve the expression, purification, and yield of Fab fragments in Escherichia coli expression systems, as well as current advances in the applications of Fab fragments.

Combretastatin A4-derived payloads for antibody-drug conjugates

We describe the use of natural product combretastatin A4 (CA4) as a versatile new payload for the construction of antibody-drug conjugates (ADCs). Cetuximab conjugates consisting of CA4 derivatives were site-specially prepared by disulfide re-bridging approach using cleavable and non-cleavable linkers. These ADCs retained antigen binding and internalization efficiency and exhibited high potencies against cancer cell lines in vitro. The conjugates also demonstrated significant antitumor activities in EGFR-positive xenograft models without observed toxicities. CA4 appears to be a viable payload option for ADCs research and development.

Stimulus-cleavable chemistry in the field of controlled drug delivery

This review comprehensively summarises stimulus-cleavable linkers from various research areas and their cleavage mechanisms, thus provides an insightful guideline to extend their potential applications to controlled drug release from nanomaterials.

An overview of process development for antibody-drug conjugates produced by chemical conjugation technology

Introduction: We discuss chemical conjugation strategies for antibody-drug conjugates (ADCs) from an industrial perspective and compare three promising chemical conjugation technologies to produce site-specific ADCs.Areas covered: Currently, nine ADCs are commercially approved and all are produced by chemical conjugation technology. However, seven of these ADCs contain a relatively broad drug distribution, potentially limiting their therapeutic indices. In 2019, the first site-specific ADC was launched on the market by Daiichi-Sankyo. This achievement, and an analysis of clinical trials over the last decade, indicates that current industrial interest in the ADC field is shifting toward site-specific conjugation technologies. From an industrial point of view, we aim to provide guidance regarding established conjugation methodologies that have already been applied to scale-up stages. With an emphasis on highly productive, scalable, and synthetic process robustness, conjugation methodologies for ADC production is discussed herein.Expert opinion: All three chemical conjugation technologies described in this review have various advantages and disadvantages, therefore drug developers can utilize these depending on their biological and/or protein targets. The future landscape of the ADC field is also discussed.

Divinylsulfonamides enable the construction of homogeneous antibody-drug conjugates

Methods that site-specifically attach payloads to an antibody with controlled DAR (Drug-Antibody Ratio) are highly desirable for the generation of homogeneous antibody-drug conjugates (ADCs). We describe the use of N-phenyl-divinylsulfonamide scaffold as a linker platform to site-specifically construct homogeneous DAR four ADCs through a disulfide re-bridging approach. Several monomethyl auristatin E (MMAE)-linkers were synthesized and the drug-linkers that contain electron-donating groups on the phenyl of the linker showed high stability. Her2-targeted MMAE-linker-herceptin and EGFR targeted MMAE-linker-cetuximab conjugates were prepared. The conjugates demonstrated high efficacy and selectivity for killing target-positive cancer cells in vitro. The EGFR-targeted conjugates also showed significant antitumor activities in vivo.