Manipulating the Click Reactivity of Dibenzoazacyclooctynes: From Azide Click Component to Caged Acylation Reagent by Silver Catalysis.

Strain-promoted azide-alkyne cycloaddition using dibenzoazacyclooctyne (DBCO) is widely applied in copper-free bioorthogonal reactions. Reported here is the efficient acid-promoted rearrangement and silver-catalyzed amidation of DBCO, which alters its click reactivity robustly. In the switched click reaction, DBCO, as a caged acylation reagent, enables rapid peptide/protein modification after decaging facilitated by silver catalysts, rendering site-specific conjugation of an IgG antibody by a Fc-targeting peptide.

Thermostability detection and optimization of glycoengineered antibodies and antibody-drug conjugates based on differential scanning flouremitry analysis.

Thermostability of monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs), as a critical property of biotherapeutics, is important for their physicochemical processes, pharmacodynamics, and pharmacokinetics. Fc glycosylation of mAbs plays a crucial role in antibody functions including thermostability, however, due to the lack of homogeneous glycosylation for comparison, the precise impact of glycoforms on thermostability of mAbs and ADCs remains challenging to elucidate. In this paper, we employed the technique of differential scanning fluorimetry (DSF) to investigate the thermostability of Fc domains, glycoengineered mAbs, and ADCs, carrying well-defined N-glycan structures for comparison. The results revealed that high-mannose-type N-glycans dramatically reduce the Tm value of Fc, compared to complex-type N-glycans. We also found that core-fucose contributes to the thermostability of mAbs, and the unnatural modification on non-reducing end of biantennary N-glycan can compensate the reduced stability of afucosylated mAbs and maintain the advantage of enhanced antibody-dependent cell-mediated cytotoxicity (ADCC). DSF analysis of lysine-linked and glycosite-specific ADCs indicated that thermostability of glycan-linked ADCs is reduced, but it could be improved by using an optimized linkage. This work provides an in-depth analysis on thermostability of mAbs and ADCs with homogeneous glycoforms, and also proposes new strategies for optimizing glycoengineered mAbs and glycosite-specific ADCs using unnatural glycan and stabilized linkage.

Sulfonium, an Underestimated Moiety for Structural Modification, Alters the Antibacterial Profile of Vancomycin Against Multidrug-Resistant Bacteria.

In the antibiotics arsenal, vancomycin is a last resort for the treatment of intractable infections. However, this situation is under threat because of the increasing appearance of vancomycin-resistant bacteria (VRB). Herein, we report a series of novel vancomycin derivatives carrying a sulfonium moiety. The sulfonium-vancomycin derivatives exhibited enhanced antibacterial activity against VRB both in vitro and in vivo. These derivatives also exhibited activity against some Gram-negative bacteria. The sulfonium modification enhanced the interaction of vancomycin with the bacterial cell membrane and disrupts membrane integrity. Furthermore, the in vivo pharmacokinetic profile, stability, and toxicity of these derivatives demonstrated good druggability of the sulfonium-vancomycin analogues. This work provides a promising strategy for combating drug-resistant bacterial infection, and advances the knowledge on sulfonium derivatives for structural optimization and drug development.

One-pot N-glycosylation remodeling of IgG with non-natural sialylglycopeptides enables glycosite-specific and dual-payload antibody-drug conjugates.

Chemoenzymatic transglycosylation catalyzed by endo-S mutants is a powerful tool for in vitro glycoengineering of therapeutic antibodies. In this paper, we report a one-pot chemoenzymatic synthesis of glycoengineered Herceptin using an egg-yolk sialylglycopeptide (SGP) substrate. Combining this one-pot strategy with novel non-natural SGP derivatives carrying azido or alkyne tags, glycosite-specific conjugation was enabled for the development of new antibody-drug conjugates (ADCs). The site-specific ADCs and semi-site-specific dual-drug ADCs were successfully achieved and characterized with SDS-PAGE, intact antibody or ADC mass spectrometry analysis, and PNGase-F digestion analysis. Cancer cell cytotoxicity assay revealed that small-molecule drug release of these ADCs relied on the cleavable Val-Cit linker fragment embedded in the structure. These results represent a new approach for glycosite-specific and dual-drug ADC design and rapid synthesis, and also provide the structural requirement for their biologic activities.

[Derivation and application of sediment quality criteria of Cd and Hg for the Xiangjiang River].

Sediment quality criterion (SQC) is the concentrations of sediment-associated contaminants that are unlikely to be associated with sediment toxicity or other adverse effects on benthic invertebrates. Thus, the derivation of SQC is crucial to protect benthic invertebrates, and can serve as the tool for scientific sediment management. Sediment, interstitial water, and plant samples were collected at 43 sampling sites from the Xiangjiang River, and metal concentrations were determined. Based on equilibrium partitioning approach, spiked sediment toxicity approach using Hyalella azteca, and background value approach, SQC for Cd and Hg in the Xiangjiang River was derived. Results showed that, SQC-L for Cd and Hg in the Xiangjiang River were 1.89 mg x kg(-1) and 0.13 mg x kg(-1) respectively, and SQC-H were 28.32 mg x kg(-1) and 0.79 mg x kg(-1) respectively. SQC were comparable to those in previous studies. Also, the reasonability of SQC was demonstrated by the heavy metal concentrations in plants, matching sediment chemistry and toxicity data for benthic invertebrates in the Xiangjiang River. To assess the sediment quality of Xiangjiang, metal concentrations in sediment samples were compared with the SQC. It was found that the proportion of sampling sites with Cd and Hg concentrations lower than SQC-L or higher than SQC-H was low, and 74.4% and 76.7% of sampling sites showed Cd and Hg concentrations between SQC-L and SQC-H.