2,4-Diacetylphloroglucinol (DAPG) derivatives rapidly eradicate methicillin-resistant staphylococcus aureus without resistance development by disrupting membrane

Synthesis and structural modification of the natural product Ivesinol to discover novel autophagy activators

Autophagy is a lysosome-dependent cellular degradation pathway that responds to a variety of environmental and cellular stresses, which is defective in aging and age-related diseases, therefore, targeting autophagy with small-molecule activators has potential therapeutic benefits. In this study, we successfully completed the first total synthesis of Ivesinol, an identified antibacterial natural product, and efficiently constructed a library of its analogs. To measure the effect of Ivesinol analogs on autophagic activity, we performed cell imaging-based screening approach, and observed that several Ivesinol analogs exhibited potent autophagy-regulating activity. Specifically, the derivative B2 significantly activated autophagy activity in concentration- and time-dependent manners, and even outperformed the commonly used activator Torin1 in activating autophagy in MCF-7 cells at 0.5 μM. Bioinformatics analysis showed that B2 treatment significantly impacted ubiquitin mediated proteolysis and AMPK signaling pathway, with functionally related gene sets displaying strong correlations. Based on these findings, we proposed that B2 activates autophagy by mechanisms involved in downregulation of key HSP70 family members, activation of the UPR, and ultimately leading to autophagy. In conclusion, we suggest that B2 could be a promising and valuable autophagy activator with significant potential for further development.

Novel antibody-antibiotic conjugate using KRM-1657 as payload eliminates intracellular MRSA in vitro and in vivo

Staphylococcus aureus is considered to be an extracellular pathogen. However, survival of S.aureus within host cells may cause long-term colonization and clinical failure. Current treatments have poor efficacy in clearing intracellular bacteria. Antibody-antibiotic conjugates (AACs) is a novel strategy for eliminating intracellular bacteria. Herein, we use KRM-1657 as payload of AAC for the first time, and we conjugate it with anti S. aureus antibody via a dipeptide linker (Valine-Alanine) to obtain a novel AAC (ASAK-22). The ASAK-22 exhibits good in vitro pharmacokinetic properties and inhibitory activity against intracellular MRSA, with 100 μg/mL of ASAK-22 capable of eliminating intracellular MRSA to the detection limit. Furthermore, the in vivo results demonstrate that a single administration of ASAK-22 significantly reduces the bacterial burden in the bacteremia model, which is superior to the vancomycin treatment.

Discovery of novel Thymol-TPP antibiotics that eradicate MRSA persisters

The high prevalence of methicillin-resistant Staphylococcus aureus (MRSA) strains and the formation of non-growing, dormant "persisters" subsets help bacteria evade antibiotic treatment and enhance bacterial resistance, which poses a serious threat to human life and health. It is urgent to discover novel antibacterial therapies effective against MRSA persisters. Thymol is a common nutraceutical with weak antibacterial and antitumor activities. A series of Thymol triphenylphosphine (TPP) conjugates (TPP-Thy3) was designed and synthesized. These compounds showed significantly improved inhibitory activity against Gram-positive bacteria compared with Thymol. Among them, Thy3d displayed a low probability of resistance selection and showed excellent biocompatibility. Interestingly, Thy3d elicited a rapid killing effect of MRSA persisters (99.999%) at high concentration. Fluorescence experiments, electron microscopy, molecular dynamics simulation and bilayer experiment confirmed that Thy3d conjugates exerted potent antimicrobial activity by disrupting the integrity of the membrane of bacterial even the persister. Furthermore, Thy3d exhibited considerable efficacy in a mouse model of subcutaneous murine MRSA infection. In summary, TPP-Thy3 conjugates are a series of novel antibacterial agents and could serve as a new therapeutic strategy for combating antibiotic resistance.