Antibody-drug conjugate and free geldanamycin combination therapy enhances anti-cancer efficacy.

Antibody drug-conjugates (ADCs) targeting human epidermal growth factor (HER2) are a rapidly expanding class of cancer therapeutics. Such ADCs are known to suffer from inefficient trafficking to the lysosome due to HER2 endosomal recycling, leaving most bound ADCs at the cell surface or in early endosomes. This study aims to increase the maximum cytotoxicity of ADC treatment by co-delivering a small molecule inhibitor targeting the primary chaperone of HER2, heat shock protein 90 (HSP90). We hypothesized that inhibiting HSP90 could aid ADC cytotoxicity by overcoming HER2 endosomal recycling. Flow cytometric studies tracking HER2 surface expression revealed âˆ¼ 10 nM geldanamycin (GA) as the threshold for inhibiting HSP90 mediated HER2 recycling. Cytotoxicity studies in HER2 overexpressing cancer cell lines NCI-N87, MDA-MB-453, and SKOV3 demonstrated that co-administration of ADC alongside 100 nM GA significantly increased cytotoxicity compared to ADC alone. In all cases, baseline cytotoxicity was observed even in low HER2 expressing line MDA-MB-231 cells, indicating possible off-target effects. To mitigate this baseline cytotoxicity, a "pulse treatment" regime was adopted where cells are pre-loaded with T-DM1 or T-MMAE ADCs for 4 h, followed by a 4-hour pulse treatment with ADC and 100 nM GA to initiate trafficking of HER2 bound ADC to the lysosome. Afterwards, GA is removed, and ADC treatment is continued. GA pulse co-treatment decreased the amount of ADC required to achieve maximum cytotoxicity while minimizing baseline cytotoxicity. No such co-treatment regime featuring a pulse sequence has been explored before. Such co-treatments could offer a viable solution to increase ADC efficacy in hard to treat or resistant HER2-positive cancers.

Antibody drug conjugates: design and selection of linker, payload and conjugation chemistry.

Antibody drug conjugates (ADCs) have emerged as an important pharmaceutical class of drugs designed to harness the specificity of antibodies with the potency of small molecule therapeutics. The three main components of ADCs are the antibody, the linker, and the payload; the majority of early work focused intensely on improving the functionality of these pieces. Recently, considerable attention has been focused on developing methods to control the site and number of linker/drug conjugated to the antibody, with the aim of producing more homogenous ADCs. In this article, we review popular conjugation methods and highlight recent approaches including "click" conjugation and enzymatic ligation. We discuss current linker technology, contrasting the characteristics of cleavable and non-cleavable linkers, and summarize the essential properties of ADC payload, centering on chemotherapeutics. In addition, we report on the progress in characterizing to determine physicochemical properties and on advances in purifying to obtain homogenous products. Establishing a set of selection and analytical criteria will facilitate the translation of novel ADCs and ensure the production of effective biosimilars.

Redox-responsive branched-bottlebrush polymers for in vivo MRI and fluorescence imaging.

Stimuli-responsive multimodality imaging agents have broad potential in medical diagnostics. Herein, we report the development of a new class of branched-bottlebrush polymer dual-modality organic radical contrast agents--ORCAFluors--for combined magnetic resonance and near-infrared fluorescence imaging in vivo. These nitroxide radical-based nanostructures have longitudinal and transverse relaxation times that are on par with commonly used heavy-metal-based magnetic resonance imaging (MRI) contrast agents. Furthermore, these materials display a unique compensatory redox response: fluorescence is partially quenched by surrounding nitroxides in the native state; exposure to ascorbate or ascorbate/glutathione leads to nitroxide reduction and a concomitant 2- to 3.5-fold increase in fluorescence emission. This behaviour enables correlation of MRI contrast, fluorescence intensity and spin concentration with tissues known to possess high concentrations of ascorbate in mice. Our in vitro and in vivo results, along with our modular synthetic approach, make ORCAFluors a promising new platform for multimodality molecular imaging.

Catalyst-controlled Wacker-type oxidation of homoallylic alcohols in the absence of protecting groups.

Homoallylic alcohols are oxidized to ß-hydroxy ketones using a TBHP-mediated Pd-catalyzed Wacker-type oxidation. The use of a bidentate ligand, quinoline-2-oxazoline (Quinox), and TBHP((aq)) as the terminal oxidant provides good yields of the desired products with reaction times significantly reduced as compared to the Tsuji-Wacker oxidation. Additionally, bis- and tris-homoallylic alcohols are oxidized to provide cyclic peroxyketals, presumably via nucleophilic attack of the methyl ketone product.