Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. Current tyrosine kinase inhibitors (TKIs) targeting oncogenic KIT and PDGFRA have improved patient outcomes, yet off-target toxicities and drug resistance mutations remain major clinical challenges. Many approved TKIs, often repurposed from other cancer indications, harbor diverse hinge-binding motifs that limit activity against resistance mutations clustering in the ATP-binding pocket of the kinase domain. Here, we describe a structure-based scaffold-hopping strategy to design kinase inhibitors with selectivity for mutant KIT/PDGFRA. Using structure-activity relationship (SAR) studies and 14 determined co-crystal structures, including a structure of the PDGFRA-G680R solvent-front mutation, we define key molecular interactions underlying resistance and inhibitor selectivity. Our lead 6,7-quinazoline-based inhibitors show high potency against clinically relevant KIT/PDGFRA mutations and effectively suppress downstream signaling. These compounds provide selective chemical tools to interrogate resistance mechanisms, and the PDGFRA-G680R structure shows the molecular basis for targeting solvent-front mutations across oncogenic kinases. In this work, the authors develop and characterize KIT/PDGFRA inhibitors to define key molecular interactions underlying inhibitor selectivity and drug-resistance, reporting structural insights for targeting solvent-front mutations across oncogenic kinases.
T. Schulz, M. Beerbaum, A. Scrima et al.· Nature Communications· 0 citations
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.
G. D'Angelo, Kosmas Alexandros Pervanidis, Ioannis Athanasiadis et al.· Angewandte Chemie· 0 citations
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