ABSTRACT
Recently, we disclosed a series of potent pyrimidine benzamide-based thrombopoietin receptor agonists. Unfortunately, the structural features required for the desired activity conferred physicochemical properties that were not favorable for the development of an oral agent. The physical properties of the series were improved by replacing the aminopyrimidinyl group with a piperidine-4-carboxylic acid moiety. The resulting compounds possessed favorable in vivo pharmacokinetic properties, including good bioavailability.
Subject(s)
Benzoates/chemistry , Benzoates/metabolism , Hydrazines/chemistry , Hydrazines/metabolism , Pyrazoles/chemistry , Pyrazoles/metabolism , Receptors, Thrombopoietin/agonists , Receptors, Thrombopoietin/metabolism , Administration, Oral , Animals , Benzoates/administration & dosage , Biological Availability , Caco-2 Cells , Humans , Hydrazines/administration & dosage , Piperidines/chemical synthesis , Piperidines/metabolism , Pyrazinamide/analogs & derivatives , Pyrazinamide/chemical synthesis , Pyrazinamide/metabolism , Pyrazoles/administration & dosage , Pyrimidines/chemical synthesis , Pyrimidines/metabolism , RatsABSTRACT
A series of pyrimidine benzamide-based thrombopoietin receptor agonists is described. The lead molecule contains a 2-amino-5-unsubstituted thiazole, a group that has been associated with idiosyncratic toxicity. The potential for metabolic oxidation at C-5 of the thiazole, the likely source of toxic metabolites, was removed by substitution at C-5 or by replacing the thiazole with a thiadiazole. Potency in the series was improved by modifying the substituents on the pyrimidine and/or on the thiazole or thiadiazole pendant aryl ring. In vivo examination revealed that compounds from the series are not highly bioavailable. This is attributed to low solubility and poor permeability.
Subject(s)
Benzamides/chemical synthesis , Benzamides/pharmacology , Pyrimidines/chemical synthesis , Pyrimidines/pharmacology , Receptors, Thrombopoietin/agonists , Antigens, CD34/metabolism , Benzamides/pharmacokinetics , Cell Differentiation/drug effects , Cell Line , Cell Proliferation/drug effects , Chemical Phenomena , Chemistry, Physical , Computer Simulation , Cross Reactions , Drug Evaluation, Preclinical , Humans , Molecular Weight , Pyrimidines/pharmacokinetics , Solubility , Structure-Activity RelationshipABSTRACT
The oxazolidinones are one of the newest classes of antibiotics. They inhibit bacterial growth by interfering with protein synthesis. The mechanism of oxazolidinone action and the precise location of the drug binding site in the ribosome are unknown. We used a panel of photoreactive derivatives to identify the site of action of oxazolidinones in the ribosomes of bacterial and human cells. The in vivo crosslinking data were used to model the position of the oxazolidinone molecule within its binding site in the peptidyl transferase center (PTC). Oxazolidinones interact with the A site of the bacterial ribosome where they should interfere with the placement of the aminoacyl-tRNA. In human cells, oxazolidinones were crosslinked to rRNA in the PTC of mitochondrial, but not cytoplasmic, ribosomes. Interaction of oxazolidinones with the mitochondrial ribosomes provides a structural basis for the inhibition of mitochondrial protein synthesis, which is linked to clinical side effects associated with oxazolidinone therapy.
Subject(s)
Mitochondria/drug effects , Oxazolidinones/pharmacology , Peptidyl Transferases/drug effects , Protein Synthesis Inhibitors/pharmacology , RNA, Ribosomal/drug effects , Software , Acetamides , Anti-Infective Agents/chemistry , Anti-Infective Agents/pharmacology , Binding Sites/drug effects , Cross-Linking Reagents/chemistry , Cross-Linking Reagents/pharmacology , Cytoplasm/drug effects , Cytoplasm/enzymology , Drug Resistance/genetics , Escherichia coli/drug effects , Escherichia coli/enzymology , Humans , Linezolid , Mitochondria/enzymology , Models, Molecular , Molecular Structure , Mutation/genetics , Oxazolidinones/chemistry , Peptidyl Transferases/metabolism , Protein Synthesis Inhibitors/chemistry , RNA, Bacterial/genetics , RNA, Bacterial/metabolism , RNA, Ribosomal/metabolism , RNA, Ribosomal, 23S , RNA, Transfer, Amino Acyl/antagonists & inhibitors , RNA, Transfer, Amino Acyl/metabolism , Staining and Labeling , Staphylococcus aureus/drug effects , Staphylococcus aureus/enzymologyABSTRACT
Replacement of the morpholine C-ring of linezolid 1 with a 1,3,4-thiadiazolyl ring leads to oxazolidinone analogues 5 having potent antibacterial activity against both gram-positive and gram-negative organisms. Conversion of the C5 acetamide group to a thioacetamide further increases the potency of these compounds.
Subject(s)
Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/pharmacology , Gram-Positive Bacteria/drug effects , Oxazolidinones/chemical synthesis , Oxazolidinones/pharmacology , Phenols/chemistry , Thiadiazoles/chemistry , Acetamides/chemical synthesis , Acetamides/chemistry , Acetamides/pharmacology , Animals , Anti-Bacterial Agents/chemistry , Linezolid , Microbial Sensitivity Tests , Oxazolidinones/chemistry , Rats , Structure-Activity Relationship , Thioacetamide/chemical synthesis , Thioacetamide/chemistry , Thioacetamide/pharmacologyABSTRACT
Oxazolidinone antibiotics, an important new class of synthetic antibacterials, inhibit protein synthesis by interfering with ribosomal function. The exact site and mechanism of oxazolidinone action has not been elucidated. Although genetic data pointed to the ribosomal peptidyltransferase as the primary site of drug action, some biochemical studies conducted in vitro suggested interaction with different regions of the ribosome. These inconsistent observations obtained in vivo and in vitro have complicated the understanding of oxazolidinone action. To localize the site of oxazolidinone action in the living cell, we have cross-linked a photoactive drug analog to its target in intact, actively growing Staphylococcus aureus. The oxazolidinone cross-linked specifically to 23 S rRNA, tRNA, and two polypeptides. The site of cross-linking to 23 S rRNA was mapped to the universally conserved A-2602. Polypeptides cross-linked were the ribosomal protein L27, whose N terminus may reach the peptidyltransferase center, and LepA, a protein homologous to translation factors. Only ribosome-associated LepA, but not free protein, was cross-linked, indicating that LepA was cross-linked by the ribosome-bound antibiotic. The evidence suggests that a specific oxazolidinone binding site is formed in the translating ribosome in the immediate vicinity of the peptidyltransferase center.
