Preparation, biological & cheminformatics-based assessment of N2,N4-diphenylpyrimidine-2,4-diamine as potential Kinase-targeted antimalarials.

Twenty eight new N2,N4-diphenylpyrimidine-2,4-diamines have been prepared in order to expand our understanding of the anti-malarial SAR of the scaffold. The aim of the study was to make structural modifications to improve the overall potency, selectivity and solubility of the series by varying the anilino groups attached to the 2- and 4-position. We evaluated the activity of the compounds against Plasmodium falciparum (Pf) 3D7, cytotoxicity against HepG2, % inhibition at a panel of 10 human kinases, solubility, permeability and lipophilicity, and human and rat in vitro clearance. 11 was identified as a potent anti-malarial with an IC50 of 0.66 µM at the 3D7 strain and a selectivity (SI) of ~ 40 in terms of cytotoxicity against the HepG2 cell line. It also displayed low experimental logD7.4 (2.27), reasonable solubility (124 µg/ml), good metabolic stability, but low permeability. A proteo-chemometric workflow was employed to identify putative Pf targets of the most promising compounds. Ligand-based similarity searching of the ChEMBL database led to the identification of most probable human targets. These were then used as input for sequence-based searching of the Pf proteome. Homology modelling and molecular docking were used to evaluate whether compounds could indeed bind to these targets with valid binding modes. In vitro biological testing against close human analogs of these targets was subsequently undertaken. This allowed us to identify potential Pf targets and human anti-targets that could be exploited in future development.

Design, synthesis, and evaluation of the anticancer activity of 2-amino-aryl-7-aryl-benzoxazole compounds.

A series of 2-amino-aryl-7-aryl-benzoxazole derivatives have been designed, synthesized, and evaluated as anticancer agents. Fourteen of the compounds exhibited cytotoxic effects toward human A549 lung cancer cells. We found 12l was the most potent with an EC50 of 0.4 µm, equivalent to the anticancer drug doxorubicin, but had low selectivity following cross screening in monkey kidney Vero cells. Eight of the most potent or most selective compounds were further profiled in additional cell lines (MCF7, NCI-H187, and KB) to better understand their cytotoxic activity. Only compound 12l had a measurable EC50 in a single cell line (3.3 µm in the KB cell line). Taken together, this data suggest the series as a whole display specific cytotoxicity toward A549 cells. Cheminformatics searches pointed to JAK2 as a possible target. A subset of compounds assayed at this target showed IC50 s ranging from 10 to 0.08 µm; however, no clear correlation between JAK2 potency and A549 cytotoxicity was observed.

Evaluation of the anti-malarial activity and cytotoxicity of 2,4-diamino-pyrimidine-based kinase inhibitors.

A series of 2,4 diamino-pyrimidines have been identified from an analysis of open access high throughput anti-malarial screening data reported by GlaxoSmithKline at the 3D7 and resistant Dd2 strains. SAR expansion has been performed using structural knowledge of the most plausible parasite target. Seventeen new analogs have been synthesized and tested against the resistant K1 strain of Plasmodium falciparum (Pf). The cytotoxicity of the compounds was assessed in Vero and A549 cells and their selectivity towards human kinases including JAK2 and EGFR were undertaken. We identified compound 5n and 5m as sub-micromolar inhibitors, with equivalent anti-malarial activity to Chloroquine (CQ). Compounds 5d and 5k, µM inhibitors of Pf, displayed improved cytotoxicity with weak inhibition of the human kinases.

Elucidating the origin of the esterase activity of human serum albumin using QM/MM calculations.

Human serum albumin (HSA) is a critical transport plasma protein accounting for ∼60% of the total protein content in blood. Remarkably, this protein is also found to display esterase activity. In this study, we apply theoretical studies to elucidate the origin of the esterase-like activity arising from the Sudlow site I. Using MD and QM/MM calculations, we investigate which active site residues are involved in the reaction, and the precise mechanistic sequence of events. Our results suggest Lys199, His242, and Arg257 help give rise to the esterase activity and that the most catalytically efficient active site configuration requires that both Lys199 and Aspirin are in their neutral forms. The abundance of HSA in the body suggests the protein might be a suitable target for the computational guided design of acetyl based pro-drugs of acidic molecules that often displayed limited oral exposure due to their unmasked ionizable substituent.