STEFs: Activated Vinylogous Protein-Reactive Electrophiles

Macrodiolide Diversification Reveals Broad Immunosuppressive Activity That Impairs the cGAS-STING Pathway

The development of new immunomodulatory agents can impact various areas of medicine. In particular, compounds with the ability to modulate innate immunological pathways hold significant unexplored potential. Herein, we report a modular synthetic approach to the macrodiolide natural product (-)-vermiculine, an agent previously shown to possess diverse biological effects, including cytotoxic and immunosuppressive activity. The synthesis allows for a high degree of flexibility in modifying the macrocyclic framework, including the formation of all possible stereoisomers. In total, 18 analogues were prepared. Two analogues with minor structural modifications showed clearly enhanced cancer cell line selectivity and reduced toxicity. Moreover, these compounds possessed broad inhibitory activity against innate immunological pathways in human PBMCs, including the DNA-sensing cGAS-STING pathway. Initial mechanistic characterization suggests a surprising impairment of the STING-TBK1 interaction.

Forward Chemical Genetic Screen for Oxygen-Dependent Cytotoxins Uncovers New Covalent Fragments that Target GPX4

The identification of growth inhibitory compounds with the ability to selectively target the cellular oxygenation state may be of therapeutic interest. Here, a phenotypic screen of a covalent fragment library revealed diverse compounds containing propiolamide warheads with selective toxicity for liver cancer cells in normoxic conditions. Target identification and validation through CETSA and direct pulldown experiments demonstrated that several compounds target glutathione peroxidase 4 (GPX4) and induce ferroptotic cell death. Although being an oxidative cell death mechanism, ferroptosis can be induced also under hypoxic conditions. Prompted by the selective toxicity discovered in the screen, we mapped the oxygen-dependence of several ferroptosis-inducing compounds across three different cell lines. These studies revealed combinations with notable reductions in sensitivity under hypoxic conditions. These observations are mechanistically interesting and may be relevant for the use of ferroptosis-inducers as anti-cancer agents.

Reactivity and Selectivity Principles in Native Protein Bioconjugation

Are chemical methods capable of precisely engineering the native proteins? Is it possible to develop platforms that can empower the regulation of chemoselectivity, site-selectivity, modularity, protein-specificity, and site-specificity? This account delineates our research journey in the last ten years on the developments revolving around these questions. It will range from the realization of chemoselective and site-selective labeling of reactivity hotspots to modular linchpin directed modification (LDM®) platform and site-specific Gly-tag® technology. Also, we outline a few biotechnology tools, including Maspecter®, that accelerated the detailed analysis of the bioconjugates and rendered a powerful toolbox for homogeneous antibody-drug conjugates (ADCs).