Dual-Site Covalent Targeting Enables BD2-Selective BET Inhibition With Potent Antitumor Activity in Mice

Jibo Kang, Xuan Wang, Hong Zhang, Jieying Lin, Peng Chen, Zuqin Wang, Zengjun Hao, Fengfei Miao, Fengcai Zhang, Tao Li, Yusheng Xie, Junjian Wang, Zhi-Min Zhang, Shao Q. Yao, Xiaoyun Lu

Angewandte Chemie International Edition 2026 e1224416

https://doi.org/10.1002/anie.1224416

Bromodomain and extra-terminal (BET) proteins are validated therapeutic targets for cancer, but clinical translation of pan-BET inhibitors is limited by dose-limiting toxicities from non-selective inhibition of BD1/BD2 domains. Herein, we report the first-ever domain-selective covalent inhibitor, named ipAE1, of BET BD2 domains by installing an epoxide warhead onto the scaffold of ABBV-744. ipAE1 was shown to irreversibly modify Glu438 and His437 (to a lesser extent) located within the BRD4(2) binding pocket via a dual-covalent mechanism, as evidenced by its chemical probe pAE1. Furthermore, ipAE1 exhibited exceptional potency against BRD4(2) (Kd = 0.096 nM) with > 1900-fold selectivity over BRD4(1), leading to potent and sustained antiproliferative activity in MV4-11 cells (GI50 = 1.5 nM). Subsequent live-cell proteome-wide profiling validated BRD4 as the primary cellular target of ipAE1. Consistent with cellular activities, ipAE1 possessed a significantly enhanced antitumor efficacy in an MV4-11 xenografted mouse model compared to ABBV-744, presumably due to its on-target covalent engagement in vivo. Our study thus establishes for the first time a novel targeted covalent inhibition (TCI) strategy that engages two weakly nucleophilic residues within a single bromodomain, an approach generalizable to other compounds targeting E/H, providing a highly selective platform for future development of next-generation BET inhibitors.

Isoform-Selective Targeting of Akt Through Covalent Allosteric Inhibition

'Angelo, Giovanni Danilo; Pervanidis, Kosmas Alexandros; Athanasiadis, Ioannis; Lukianchikov, Vladimir; Scrima, Andrea; Depta, Laura; Stier, Sara; Müller, Matthias P.; Farin, Henner F.; Quambusch, Lena; Rauh, Daniel. 

Angewandte Chemie International Edition (2026), e3567206. 

https://doi.org/10.1002/anie.3567206

The Akt family of serine/threonine kinases plays a crucial role in various cellular processes, including proliferation, survival, and metabolism. Three Akt isoforms (Akt1, Akt2, and Akt3) have distinct physiological roles, and while individual isoform dysregulation is disease-linked, unselective Akt inhibition leads to side effects. Here, we report the development of selective covalent-allosteric Akt inhibitors (CAAIs) targeting Akt2 and Akt3 while sparing Akt1. Guided by protein x-ray crystallography and molecular modeling, key structural differences within the allosteric pockets of the isoforms were identified and exploited in a structure-based design strategy. By stabilizing the inactive kinase conformation, CAAIs overcome the intrinsic selectivity limitations of ATP-competitive inhibitors. After biological characterization, the pyrazole-containing inhibitors emerged as the most potent and selective Akt2 inhibitors, while inhibitors with pyridines as an isoform-selective element were predominantly targeting Akt3 selectively. Importantly, these new inhibitors were also evaluated in patient-derived colorectal cancer organoids. Co-crystal structures of inhibitors bound to an engineered construct mimicking the Akt2 allosteric pocket elucidated the molecular basis of isoform selectivity, guiding further optimization. This work not only establishes a framework for the development of isoform-selective therapeutics but also highlights the potential for unraveling isoform-specific functions in signaling pathways relevant to cancer biology.