title: Design and synthesis of novel 6,7-imidazotetrahydroquinoline inhibitors of thymidylate synthase using iterative protein crystal structure analysis.
abstract: Antifolate inhibitors of thymidylate synthase (TS) have primarily been based on the structure of folic acid. This paper describes the identification and development of novel 6,7-imidazotetrahydroquinoline TS inhibitors by iterative ligand design, synthesis, and crystallographic analysis of protein-inhibitor complexes. Beginning with a high-resolution crystal structure of E. coli TS (TS, EC 2.1.1.45), an imidazotetrahydroquinoline inhibitor was designed de novo to occupy the folate binding pocket. Structural modifications of the initial compound 1h (Ki approximately 5 microM human/E. coli TS) were then made on the basis of feedback from additional cocrystal structures and activity data. An amino group in the 2-position of the imidazole was found to increase the potency of the series by 1-2 orders of magnitude. Other substitutions on the imidazole ring (1-CH3, 2-CH3, 2-NHCH3, 2-SCH3) generally led to weaker inhibition. Additional improvements in activity were obtained by modification of the substituents on the tetrahydroquinoline nitrogen, bringing the Ki of three of the compounds below 15 nM against the human TS enzyme. The compounds were tested for cytotoxicity and were shown to inhibit the growth of three tumor cell lines in vitro.
authors.affiliation: Agouron Pharmaceuticals, Inc., San Diego, California 92121.
authors.forename: S H
authors.initials: SH
authors.lastname: Reich
authors.forename: M A
authors.initials: MA
authors.lastname: Fuhry
authors.forename: D
authors.initials: D
authors.lastname: Nguyen
authors.forename: M J
authors.initials: MJ
authors.lastname: Pino
authors.forename: K M
authors.initials: KM
authors.lastname: Welsh
authors.forename: S
authors.initials: S
authors.lastname: Webber
authors.forename: C A
authors.initials: CA
authors.lastname: Janson
authors.forename: S R
authors.initials: SR
authors.lastname: Jordan
authors.forename: D A
authors.initials: DA
authors.lastname: Matthews
authors.forename: W W
authors.initials: WW
authors.lastname: Smith
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology; D000818:Animals; D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000494:pharmacology; D001665:Binding Sites; D002455:Cell Division / Q000187:drug effects; D003460:Crystallization; D015195:Drug Design; D004926:Escherichia coli / Q000201:enzymology; D005492:Folic Acid / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D007938:Leukemia / Q000473:pathology; D007939:Leukemia L1210 / Q000473:pathology; D051379:Mice; D015394:Molecular Structure; D011804:Quinolines / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D007093:Imidazoles; D011804:Quinolines; D005492:Folic Acid; D013940:Thymidylate Synthase