Structure-aided optimization of non-nucleoside M. tuberculosis thymidylate kinase inhibitors

Mycobacterium tuberculosis thymidylate kinase (MtTMPK) has emerged as an attractive target for rational drug design. We recently investigated new families of non-nucleoside MtTMPK inhibitors in an effort to diversify MtTMPK inhibitor chemical space. We here report a new series of MtTMPK inhibitors by combining the Topliss scheme with rational drug design approaches, fueled by two co-crystal structures of MtTMPK in complex with developed inhibitors. These efforts furnished the most potent MtTMPK inhibitors in our assay, with two analogues displaying low micromolar MIC values against H37Rv Mtb. Prepared inhibitors address new sub-sites in the MtTMPK nucleotide binding pocket, thereby offering new insights into its druggability. We studied the role of efflux pumps as well as the impact of cell wall permeabilizers for selected compounds to potentially provide an explanation for the lack of correlation between potent enzyme inhibition and whole-cell activity.

Structure-based identification of novel CK2 inhibitors with a linear 2-propenone scaffold as anti-cancer agents

Protein kinase CK2 has emerged as an attractive cancer therapeutic target. Previous studies have highlighted the challenge of optimizing CK2 ATP-competitive inhibitors that have low druggability due to their polycyclic ring scaffolds. Therefore the development of novel inhibitors with non-polycyclic scaffolds emerges as a promising strategy for drug discovery targeting CK2. In this current study, based on the similar predicted binding poses of the linear 2-propenone scaffold of isoliquiritigenin with that of the polycyclic inhibitor CX-4945, a series of 2-propenone derivatives containing an amine-substituted five-membered heterocycle and a benzoic acid were designed, synthesized and evaluated for their in vitro CK2 inhibition and anti-cancer activity. Compound 8b was found to be the most potent CK2 inhibitor (IC₅₀ = 0.6 μM) with the anti-proliferative activity on HepG2 cancer cells (IC₅₀ = 14 μM), compared to the activity of isoliquiritigenin (IC₅₀ = 17 μM and 51 μM, respectively). Molecular docking was performed to understand the binding modes of the newly designed 2-propenone derivatives with CK2. Compound 8b formed the most favorable network of hydrogen bonds with both the hinge region and positive area. Our results indicate that CK2 derivatives with a linear 2-propenone scaffold are promising candidates for anti-cancer drug discovery.

Datasets, processing and refinement details for Mtb-AnPRT: inhibitor structures with various space groups

There are twenty-five published structures of Mycobacterium tuberculosis anthranilate phosphoribosyltransferase (Mtb-AnPRT) that use the same crystallization protocol. The structures include protein complexed with natural and alternative substrates, protein:inhibitor complexes, and variants with mutations of substrate-binding residues. Amongst these are varying space groups (i.e. P2₁, C2, P2₁2₁2, P2₁2₁2₁). This article outlines experimental details for 3 additional Mtb-AnPRT:inhibitor structures. For one protein:inhibitor complex, two datasets are presented – one generated by crystallization of protein in the presence of the inhibitor and another where a protein crystal was soaked with the inhibitor. Automatic and manual processing of these datasets indicated the same space group for both datasets and thus indicate that the space group differences between structures of Mtb-AnPRT:ligand complexes are not related to the method used to introduce the ligand.