ABSTRACT
The intracellular polymerization and the concomitant sickling processes, central to the pathology of sickle cell disease, can be mitigated by increasing the oxygen affinity of sickle hemoglobin (HbS). Attempts to develop azolylacryloyl derivatives to covalently interact with ßCys93 and destabilize the low-O2-affinity T-state (deoxygenated) HbS to the polymer resistant high-O2-affinity R-state (liganded) HbS were only partially successful. This was likely due to the azolylacryloyls carboxylate moiety directing the compounds to also bind in the central water cavity of deoxygenated Hb and stabilizing the T-state. We now report a second generation of KAUS compounds (KAUS-28, KAUS-33, KAUS-38, and KAUS-39) without the carboxylate moiety designed to bind exclusively to ßCys93. As expected, the compounds showed reactivity with both free amino acid l-Cys and the Hb ßCys93. At 2 mM concentrations, the compounds demonstrated increased Hb affinity for oxygen (6% to 15%) in vitro, while the previously reported imidazolylacryloyl carboxylate derivative, KAUS-15 only showed 4.5% increase. The increased O2 affinity effects were sustained through the experimental period of 12 h for KAUS-28, KAUS-33, and KAUS-38, suggesting conserved pharmacokinetic profiles. When incubated at 2 mM with red blood cells from patients with homozygous SS, the compounds inhibited erythrocyte sickling by 5% to 9%, respectively in correlation with the increase Hb-O2 affinity. These values compare to 2% for KAUS-15. When tested with healthy mice, KAUS-38 showed very low toxicity.
ABSTRACT
Aromatic aldehydes and ethacrynic acid (ECA) exhibit antipolymerization properties that are beneficial for sickle cell disease therapy. Based on the ECA pharmacophore and its atomic interaction with hemoglobin, we designed and synthesized several compounds - designated as KAUS (imidazolylacryloyl derivatives) - that we hypothesized would bind covalently to ßCys93 of hemoglobin and inhibit sickling. The compounds surprisingly showed weak allosteric and antisickling properties. X-ray studies of hemoglobin in complex with representative KAUS compounds revealed an unanticipated mode of Michael addition between the ß-unsaturated carbon and the N-terminal αVal1 nitrogen at the α-cleft of hemoglobin, with no observable interaction with ßCys93. Interestingly, the compounds exhibited almost no reactivity with the free amino acids, L-Val, L-His and L-Lys, but showed some reactivity with both glutathione and L-Cys. Our findings provide a molecular level explanation for the compounds biological activities and an important framework for targeted modifications that would yield novel potent antisickling agents.
Subject(s)
Acrylates/pharmacology , Anemia, Sickle Cell/drug therapy , Antisickling Agents/pharmacology , Hemoglobin, Sickle/antagonists & inhibitors , Imidazoles/pharmacology , Acrylates/chemical synthesis , Acrylates/chemistry , Anemia, Sickle Cell/pathology , Animals , Antisickling Agents/chemical synthesis , Antisickling Agents/chemistry , Cell Line , Cell Survival/drug effects , Dose-Response Relationship, Drug , Hemoglobin, Sickle/chemistry , Humans , Imidazoles/chemical synthesis , Imidazoles/chemistry , Mice , Models, Molecular , Molecular Structure , Structure-Activity RelationshipABSTRACT
VEGFR-2 tyrosine kinase inhibitors are currently receiving high interest in drug discovery process as anticancer agents. We have used virtual screening techniques in order to discover new scaffolds that can be used for developing new VEGFR-2 kinase inhibitors.Similarity ensemble approach was used to reduce the chemical space of ZINC database to select a subset of compounds. A validated structure-based pharmacophore was developed and adopted to screen the selected subset. Initial hits mapped to the pharmacophore were filtered using docking and scoring. Selected compounds were synthesized and biologically tested. Compound 9 showed very good cytotoxicity profile against the NCI 60 cancer cell lines, while compound 8 showed reasonable inhibition of VEGFR-2 tyrosine kinase.Stepwise virtual screening of databases such as ZINC may result in new scaffolds for developing VEGFR-2 kinase inhibitors.
Subject(s)
Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/pharmacology , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/pharmacology , Vascular Endothelial Growth Factor Receptor-2/antagonists & inhibitors , Algorithms , Cell Line, Tumor , Cell Survival/drug effects , Computer Simulation , Databases, Factual , Drug Screening Assays, Antitumor , Humans , Ligands , Models, Molecular , Molecular Conformation , Protein Kinase Inhibitors/pharmacology , User-Computer InterfaceABSTRACT
4-Anilinoquinazoline is a privileged scaffold in developing small molecule inhibitors of tyrosine kinases (TK) especially epidermal growth factor receptor (EGFR). 2 series belonging to 3'-substituted-4-anilinoquinazoline scaffold were synthesized and screened in vitro on isolated and a breast cancer cell line. The research aims at exploring the activity of compounds having diverse substituents at 3' position of the aniline moiety. Generally, the meta-substituted-anilinoquinazolines exhibited significant inhibitory activity against isolated enzyme as well as MCF-7 cancer cell line. For instance, compound 10b inhibited >99% of EGFR activities at 10 µM concentration. 6 of the tested compounds exhibited range of anti-proliferative activity below 10 µM potency. In particular, compounds 6e and 10b displayed the highest activity among the tested compounds with IC50 values equal to 8.6 and 4.84 µM, respectively. Structure-based tools were utilized to rationalize EGFR-TK binding of compound 10b since it is the most active compound in the enzyme inhibition test.
