ABSTRACT
The design, synthesis, and biochemical and biological evaluations of a novel series of 2,6-diaminobenz[cd]indole-containing inhibitors of human thymidylate synthase (TS) are described. The compounds are characterized by having either a pyridine or pyridazine ring in place of the (phenylsulfonyl)morpholinyl group of the known inhibitor N6-[4-(morpholinosulfonyl)benzyl]-N6-methyl-2,6-diaminobenz[ cd]indole glucuronate (i). Active compounds from this series showed human TS inhibition constants below the 10 nM level and were potent, selective submicromolar antitumor agents in cell culture. The compounds were synthesized by reductive alkylation of a substituted 6-aminobenz[cd]indole or reductive cyclization of a substituted 1-cyano-8-nitronaphthalene.
Subject(s)
Indoles/chemical synthesis , Indoles/pharmacology , Thymidylate Synthase/antagonists & inhibitors , Adenocarcinoma/drug therapy , Adenocarcinoma/pathology , Animals , Bacterial Proteins/antagonists & inhibitors , Cell Division/drug effects , Crystallography, X-Ray , Drug Design , Drug Evaluation, Preclinical , Escherichia coli/enzymology , Glucuronates/chemical synthesis , Glucuronates/chemistry , Glucuronates/pharmacology , Humans , Indoles/chemistry , Leukemia/drug therapy , Leukemia/pathology , Leukemia L1210/drug therapy , Leukemia L1210/pathology , Mice , Protein Conformation , Pyridines/chemical synthesis , Pyridines/chemistry , Pyridines/pharmacology , Structure-Activity Relationship , Tumor Cells, Cultured/drug effectsABSTRACT
The design, synthesis, and biological evaluation of a new class of inhibitors of thymidylate synthase (TS) is described. The molecular design was carried out by a repetitive crystallographic analysis of protein-ligand structures. At the onset of this project, we focused on the folate cofactor binding site of a high-resolution ternary crystal complex of Escherichia coli TS, 5'-fluorodeoxyuridylate (5-FdUMP) and a classical glutamate-containing folic acid analog. A preliminary ternary crystal structure of a novel compound was successfully solved. Upon analysis of this initial complex, further structural elaborations were made, and a series of active 5-(arylthio)quinazolinones was developed. The synthetic strategy was based on the displacement of a halogen at the 5-position of a quinazolinone by various aryl thioanions. The compounds were tested for inhibition of purified E. coli and/or human TS, and were assayed for cytotoxicity against three tumor cell lines in vitro. Significant thymidine protection effects were observed with several of the inhibitors, indicating that TS was the intracellular locus of activity.
Subject(s)
Pyridines/chemical synthesis , Quinazolines/chemical synthesis , Thymidylate Synthase/antagonists & inhibitors , Crystallography , Drug Design , Escherichia coli/drug effects , Folic Acid/analogs & derivatives , Folic Acid/metabolism , Humans , Pyridines/chemistry , Pyridines/pharmacology , Quinazolines/chemistry , Quinazolines/metabolism , Quinazolines/pharmacology , Structure-Activity RelationshipABSTRACT
The X-ray crystal-structure-based design, synthesis, and biological activity of a novel family of benz[cd]indole-containing inhibitors of thymidylate synthase (TS) are described. The structure-activity of the lead compound was studied by conceptually dividing the molecule into four regions and independently optimizing the substituents for each region. Combination of favored substituents for each region led to inhibitors with Ki's against the human enzyme in the range of 10-20 nM. Thymidine shift experiments suggested that the cytotoxic properties of the best enzyme inhibitors were due to TS targeting in cells. The inhibitors were synthesized from substituted 6-aminobenz[cd]indol-2(1H)-ones by alkylation with both a simple alkyl group and a substituted benzylic portion. The 2,6-diaminobenz[cd]indoles were prepared from the corresponding lactams by conversion to the thiolactam, alkylation to the methylated thiolactam, and then displacement with a substituted or unsubstituted amine.
