Site-Specific Antibody Conjugation to Engineered Double Cysteine Residues.

Site-specific antibody conjugations generate homogeneous antibody-drug conjugates with high therapeutic index. However, there are limited examples for producing the site-specific conjugates with a drug-to-antibody ratio (DAR) greater than two, especially using engineered cysteines. Based on available Fc structures, we designed and introduced free cysteine residues into various antibody CH2 and CH3 regions to explore and expand this technology. The mutants were generated using site-directed mutagenesis with good yield and properties. Conjugation efficiency and selectivity were screened using PEGylation. The top single cysteine mutants were then selected and combined as double cysteine mutants for expression and further investigation. Thirty-six out of thirty-eight double cysteine mutants display comparable expression with low aggregation similar to the wild-type antibody. PEGylation screening identified seventeen double cysteine mutants with good conjugatability and high selectivity. PEGylation was demonstrated to be a valuable and efficient approach for quickly screening mutants for high selectivity as well as conjugation efficiency. Our work demonstrated the feasibility of generating antibody conjugates with a DAR greater than 3.4 and high site-selectivity using THIOMABTM method. The top single or double cysteine mutants identified can potentially be applied to site-specific antibody conjugation of cytotoxin or other therapeutic agents as a next generation conjugation strategy.

Advances in Antibody-Drug Conjugate Design: Current Clinical Landscape and Future Innovations.

The targeted delivery of potent cytotoxic molecules into cancer cells is considered a promising anticancer strategy. The design of clinically effective antibody-drug conjugates (ADCs), in which biologically active drugs are coupled through chemical linkers to monoclonal antibodies, has presented challenges for pharmaceutical researchers. After 30 years of intensive research and development activities, only seven ADCs have been approved for clinical use; two have received fast-track designation and two breakthrough therapy designation from the Food and Drug Administration. There is continued interest in the field, as documented by the growing number of candidates in clinical development. This review aims to summarize the most recent innovations that have been applied to the design of ADCs undergoing early- and late-stage clinical trials. Discovery and rational optimization of new payloads, chemical linkers, and antibody formats have improved the therapeutic index of next-generation ADCs, ultimately resulting in improved clinical benefit for the patients.

Novel naphthoquinone and quinolinedione inhibitors of CDC25 phosphatase activity with antiproliferative properties.

CDC25 phosphatases are considered as attractive targets for anti-cancer therapy. To date, quinone derivatives are among the most potent inhibitors of CDC25 phosphatase activity. We present in this paper the synthesis and the biological evaluation of new quinolinedione and naphthoquinone derivatives, containing carboxylic or malonic acids groups introduced to mimic the role of the phosphate moieties of Cyclin-Dependent Kinase complexes. The most efficient compounds show inhibitory activity against CDC25B with IC(50) values in the 10 microM range, and are cytotoxic against HeLa cells.

Protocols for lysine conjugation.

Currently, the most widely used chemical methodology for the conjugation of drugs to monoclonal antibodies involves either lysine or cysteine residues. In this chapter, several methods for the preparation of antibody-drug conjugates (ADCs) through conjugation of drugs to solvent-exposed ε-amino groups of lysine residues are described. These methods apply to various cytotoxic agents, both tubulin binders and DNA-targeting agents and different types of linkers, cleavable or not, peptidic or disulfide-based, for example.

Receptor-based virtual ligand screening for the identification of novel CDC25 phosphatase inhibitors.

CDC25 phosphatases play critical roles in cell cycle regulation and are attractive targets for anticancer therapies. Several small non-peptide molecules are known to inhibit CDC25, but many of them appear to form a covalent bond with the enzyme or act through oxidation of the thiolate group of the catalytic cysteine. Structure-based virtual ligand screening computations were performed with FRED, Surflex, and LigandFit, a compound collection of over 310,000 druglike molecules and the crystal structure of CDC25B in order to identify novel classes of ligands. In vitro experiments carried out on a selected list of 1500 molecules led to the discovery of 99 compounds able to inhibit CDC25B activity at 100 microM. Further docking computations were applied, allowing us to propose a binding mode for the most potent molecule (IC50 = 13 microM). Our best compounds represent promising new classes of CDC25 inhibitors that also exhibit antiproliferative properties.

Design, synthesis, and biological evaluation of novel naphthoquinone derivatives with CDC25 phosphatase inhibitory activity.

CDC25 dual-specificity phosphatases are essential key regulators of eukaryotic cell cycle progression and the CDC25A and B isoforms are over-expressed in different tumors and related cancer cell lines. CDC25s are now considered to be interesting targets in the search for novel anticancer agents. We describe new compounds derived from vitamin K3 that inhibit CDC25B activity with IC50 values in the low micromolar range. These naphthoquinone derivatives also display antiproliferative activity on HeLa cells as expected for CDC25 inhibitors and inhibit cell growth in a clonogenic assay at submicromolar concentrations. They increase inhibitory tyrosine 15 phosphorylation of CDK and induce the cleavage of PARP, a hallmark of apoptosis.