Differential Kinobeads Profiling for Target Identification of Irreversible Kinase Inhibitors

Chemoproteomics profiling of kinase inhibitors with kinobeads enables the assessment of inhibitor potency and selectivity for endogenously expressed protein kinases in cell lines and tissues. Using a small panel of targeted covalent inhibitors, we demonstrate the importance of measuring covalent target binding in live cells. We present a differential kinobeads profiling strategy for covalent kinase inhibitors where a compound is added either to live cells or to a cell extract that enables the comprehensive assessment of inhibitor selectivity for covalent and noncovalent targets. We found that Acalabrutinib, CC-292, and Ibrutinib potently and covalently bind TEC family kinases, but only Ibrutinib also potently binds to BLK. ZAK was identified as a submicromolar affinity Ibrutinib off-target due to covalent modification of Cys22. In contrast to Ibrutinib, 5Z-7-Oxozeaenol reacted with Cys150 next to the DFG loop, demonstrating an alternative route to covalent inactivation of this kinase, e.g., to inhibit canonical TGF-β dependent processes

A Modular Probe Strategy for Drug Localization, Target Identification and Target Occupancy Measurement on Single Cell Level

Late stage failures of candidate drug molecules are frequently caused by off-target effects or inefficient target engagement <i>in vivo</i>. In order to address these fundamental challenges in drug discovery, we developed a modular probe strategy based on bioorthogonal chemistry that enables the attachment of multiple reporters to the same probe in cell extracts and live cells. In a systematic evaluation, we identified the inverse electron demand Diels–Alder reaction between <i>trans</i>-cyclooctene labeled probe molecules and tetrazine-tagged reporters to be the most efficient bioorthogonal reaction for this strategy. Bioorthogonal biotinylation of the probe allows the identification of drug targets in a chemoproteomics competition binding assay using quantitative mass spectrometry. Attachment of a fluorescent reporter enables monitoring of spatial localization of probes as well as drug-target colocalization studies. Finally, direct target occupancy of unlabeled drugs can be determined at single cell resolution by competitive binding with fluorescently labeled probe molecules. The feasibility of the modular probe strategy is demonstrated with noncovalent PARP inhibitors

A Modular Probe Strategy for Drug Localization, Target Identification and Target Occupancy Measurement on Single Cell Level

Late stage failures of candidate drug molecules are frequently caused by off-target effects or inefficient target engagement <i>in vivo</i>. In order to address these fundamental challenges in drug discovery, we developed a modular probe strategy based on bioorthogonal chemistry that enables the attachment of multiple reporters to the same probe in cell extracts and live cells. In a systematic evaluation, we identified the inverse electron demand Diels–Alder reaction between <i>trans</i>-cyclooctene labeled probe molecules and tetrazine-tagged reporters to be the most efficient bioorthogonal reaction for this strategy. Bioorthogonal biotinylation of the probe allows the identification of drug targets in a chemoproteomics competition binding assay using quantitative mass spectrometry. Attachment of a fluorescent reporter enables monitoring of spatial localization of probes as well as drug-target colocalization studies. Finally, direct target occupancy of unlabeled drugs can be determined at single cell resolution by competitive binding with fluorescently labeled probe molecules. The feasibility of the modular probe strategy is demonstrated with noncovalent PARP inhibitors

A Modular Probe Strategy for Drug Localization, Target Identification and Target Occupancy Measurement on Single Cell Level

Late stage failures of candidate drug molecules are frequently caused by off-target effects or inefficient target engagement <i>in vivo</i>. In order to address these fundamental challenges in drug discovery, we developed a modular probe strategy based on bioorthogonal chemistry that enables the attachment of multiple reporters to the same probe in cell extracts and live cells. In a systematic evaluation, we identified the inverse electron demand Diels–Alder reaction between <i>trans</i>-cyclooctene labeled probe molecules and tetrazine-tagged reporters to be the most efficient bioorthogonal reaction for this strategy. Bioorthogonal biotinylation of the probe allows the identification of drug targets in a chemoproteomics competition binding assay using quantitative mass spectrometry. Attachment of a fluorescent reporter enables monitoring of spatial localization of probes as well as drug-target colocalization studies. Finally, direct target occupancy of unlabeled drugs can be determined at single cell resolution by competitive binding with fluorescently labeled probe molecules. The feasibility of the modular probe strategy is demonstrated with noncovalent PARP inhibitors

Discovery of a Highly Selective Tankyrase Inhibitor Displaying Growth Inhibition Effects against a Diverse Range of Tumor Derived Cell Lines

The availability of high quality probes for specific protein targets is fundamental to the investigation of their function and their validation as therapeutic targets. We report the utilization of a dedicated chemoproteomic assay platform combining affinity enrichment technology with high-resolution protein mass spectrometry to the discovery of a novel nicotinamide isoster, the tetrazoloquinoxaline <b>41</b>, a highly potent and selective tankyrase inhibitor. We also describe the use of <b>41</b> to investigate the biology of tankyrase, revealing the compound induced growth inhibition of a number of tumor derived cell lines, demonstrating the potential of tankyrase inhibitors in oncology

Interrogating the Druggability of the 2‑Oxoglutarate-Dependent Dioxygenase Target Class by Chemical Proteomics

The 2-oxoglutarate-dependent dioxygenase target class comprises around 60 enzymes including several subfamilies with relevance to human disease, such as the prolyl hydroxylases and the Jumonji-type lysine demethylases. Current drug discovery approaches are largely based on small molecule inhibitors targeting the iron/2-oxoglutarate cofactor binding site. We have devised a chemoproteomics approach based on a combination of unselective active-site ligands tethered to beads, enabling affinity capturing of around 40 different dioxygenase enzymes from human cells. Mass-spectrometry-based quantification of bead-bound enzymes using a free-ligand competition-binding format enabled the comprehensive determination of affinities for the cosubstrate 2-oxoglutarate and for oncometabolites such as 2-hydroxyglutarate. We also profiled a set of representative drug-like inhibitor compounds. The results indicate that intracellular competition by endogenous cofactors and high active site similarity present substantial challenges for drug discovery for this target class

Cell Penetrant Inhibitors of the KDM4 and KDM5 Families of Histone Lysine Demethylases. 1. 3‑Amino-4-pyridine Carboxylate Derivatives

Optimization of KDM6B (JMJD3) HTS hit <b>12</b> led to the identification of 3-((furan-2-ylmethyl)­amino)­pyridine-4-carboxylic acid <b>34</b> and 3-(((3-methylthiophen-2-yl)­methyl)­amino)­pyridine-4-carboxylic acid <b>39</b> that are inhibitors of the KDM4 (JMJD2) family of histone lysine demethylases. Compounds <b>34</b> and <b>39</b> possess activity, IC₅₀ ≤ 100 nM, in KDM4 family biochemical (RFMS) assays with ≥50-fold selectivity against KDM6B and activity in a mechanistic KDM4C cell imaging assay (IC₅₀ = 6–8 μM). Compounds <b>34</b> and <b>39</b> are also potent inhibitors of KDM5C (JARID1C) (RFMS IC₅₀ = 100–125 nM)