ABSTRACT
Earlier we reported potent cRaf1 kinase inhibitors with a key acidic phenol pharmacophore that had, at best, adequate cellular efficacy. To improve the cellular potency, phenol isosteres and prodrugs were investigated. Many phenol isosteres were synthesized and tested, but failed to provide adequate enzyme potency. A prodrug approach resulted in a 2- to 17-fold improvement over the parent compound in cell-based efficacy.
Subject(s)
Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/pharmacology , Drug Design , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/pharmacology , Prodrugs , Proteins/metabolism , Proto-Oncogene Proteins c-raf/metabolism , Cells, Cultured , Down-Regulation/drug effects , Humans , Indicators and Reagents , Mitogen-Activated Protein Kinases/biosynthesis , Phenols/chemical synthesis , Phenols/pharmacology , Structure-Activity Relationship , TNF Receptor-Associated Factor 3ABSTRACT
A series of benzylidene-1H-indol-2-one (oxindole) derivatives was synthesized and evaluated as cRaf-1 kinase inhibitors. The key features of the molecules were the donor/acceptor motif common to kinase inhibitors and a critical acidic phenol flanked by two substitutions. Diverse 5-position substitutions provided compounds with low nanomolar kinase enzyme inhibition and inhibited the intracellular MAPK pathway.
Subject(s)
Enzyme Inhibitors/pharmacology , Proto-Oncogene Proteins c-raf/antagonists & inhibitors , Enzyme Inhibitors/chemistry , MAP Kinase Signaling System , Structure-Activity RelationshipABSTRACT
The X-ray crystal structure of the src SH2 domain revealed the presence of a thiol residue (Cys 188) located proximal to the phosphotyrosine portion of a dipeptide ligand. An aldehyde bearing ligand (1) was designed to position an electrophilic carbonyl group in the vicinity of the thiol. X-ray crystallographic and NMR examination of the complex formed between (1) and the src SH2 domain revealed a hemithioacetal formed by addition of the thiol to the aldehyde group with an additional stabilizing hydrogen bond between the acetal hydroxyl and a backbone carbonyl.
Subject(s)
Dipeptides/chemistry , Protein Conformation , Proteins/chemistry , src Homology Domains , Aldehydes , Amino Acid Sequence , Binding Sites , Crystallography, X-Ray , Cysteine , Dipeptides/chemical synthesis , Hydrogen Bonding , Ligands , Magnetic Resonance Spectroscopy , Models, Molecular , PhosphotyrosineABSTRACT
Thermodynamic measurements, structural determinations, and molecular computations were applied to a series of peptide ligands of the pp60(c-src) SH2 domain in an attempt to understand the critical binding determinants for this class of molecules. Isothermal titration calorimetry (ITC) measurements were combined with structural data derived from X-ray crystallographic studies on 12 peptide-SH2 domain complexes. The peptide ligands studied fall into two general classes: (1) dipeptides of the general framework N-acetylphosphotyrosine (or phosphotyrosine replacement)-Glu or methionine (or S-methylcysteine)-X, where X represents a hydrophobic amine, and (2) tetra- or pentapeptides of the general framework N-acetylphosphotyrosine-Glu-Glu-Ile-X, where X represents either Glu, Gln, or NH2. Dipeptide analogs which featured X as either hexanolamine or heptanolamine were able to pick up new hydrogen bonds involving their hydroxyl groups within a predominantly lipophilic surface cavity. However, due to internal strain as well as the solvent accessibility of the new hydrogen bonds formed, no net increase in binding affinity was observed. Phosphatase-resistant benzylmalonate and alpha,alpha-difluorobenzyl phosphonate analogs of phosphotyrosine retained some binding affinity for the pp60(c-src) SH2 domain but caused local structural perturbations in the phosphotyrosine-binding site. In the case where a reversible covalent thiohemiacetal was formed between a formylated phosphotyrosine analog and the thiol side chain of Cys-188, deltaS was 25.6 cal/(mol K) lower than for the nonformylated phosphotyrosine parent. Normal mode calculations show that the dramatic decrease in entropy observed for the covalent thiohemiacetal complex is due to the inability of the phosphotyrosine moiety to transform lost rotational and translational degrees of freedom into new vibrational modes.
Subject(s)
Peptides/chemistry , Protein Structure, Tertiary , Proto-Oncogene Proteins pp60(c-src)/chemistry , src Homology Domains , Amino Acid Sequence , Crystallography, X-Ray , Dipeptides/chemistry , Dipeptides/metabolism , Kinetics , Ligands , Oligopeptides/chemistry , Oligopeptides/metabolism , Peptides/metabolism , Phosphotyrosine/chemistry , Phosphotyrosine/metabolism , Protein Binding , Proto-Oncogene Proteins pp60(c-src)/metabolism , Structure-Activity Relationship , ThermodynamicsABSTRACT
To describe the health effects of the political system in Zaïre on asylum seekers seen at the Medical Foundation for the Care of Victims of Torture a retrospective study was performed of the records of 92 asylum seekers from Zaïre who were seen for medical reports at the medical foundation in 1993 and 1994. Eighty one had been imprisoned; the others had been severely treated at home by the security services. Sixty six had been detained for up to one year. Prison conditions were invariably unsanitary, and food of poor quality when provided. All had been beaten on arrest, and all but two had been beaten repeatedly in prison. Nearly all the women and some of the men described sexual abuse. Almost all left prison through bribery or because a guard had a similar background. Seventy two asylum seekers had scarring, consider to be consistent with the history, and 70 were considered to have suffered persistent psychological damage. Asylum seekers from Zaïre will have health effects from experiences unimaginable to the ordinary Briton. An understanding of the background will help clinicians manage them.