Structure-based discovery and in-parallel optimization of novel competitive inhibitors of thymidylate synthase

Chem Biol. 1999 May;6(5):319-31. doi: 10.1016/S1074-5521(99)80077-5.

Abstract

Background: The substrate sites of enzymes are attractive targets for structure-based inhibitor design. Two difficulties hinder efforts to discover and elaborate new (nonsubstrate-like) inhibitors for these sites. First, novel inhibitors often bind at nonsubstrate sites. Second, a novel scaffold introduces chemistry that is frequently unfamiliar, making synthetic elaboration challenging.

Results: In an effort to discover and elaborate a novel scaffold for a substrate site, we combined structure-based screening with in-parallel synthetic elaboration. These techniques were used to find new inhibitors that bound to the folate site of Lactobacillus casei thymidylate synthase (LcTS), an enzyme that is a potential target for proliferative diseases, and is highly studied. The available chemicals directory was screened, using a molecular-docking computer program, for molecules that complemented the three-dimensional structure of this site. Five high-ranking compounds were selected for testing. Activity and docking studies led to a derivative of one of these, dansyltyrosine (Ki 65 microM). Using solid-phase in-parallel techniques 33 derivatives of this lead were synthesized and tested. These analogs are dissimilar to the substrate but bind competitively with it. The most active analog had a Ki of 1.3 microM. The tighter binding inhibitors were also the most specific for LcTS versus related enzymes.

Conclusions: TS can recognize inhibitors that are dissimilar to, but that bind competitively with, the folate substrate. Combining structure-based discovery with in-parallel synthetic techniques allowed the rapid elaboration of this series of compounds. More automated versions of this approach can be envisaged.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Catalytic Domain
  • Drug Design
  • Enzyme Inhibitors / chemical synthesis
  • Enzyme Inhibitors / pharmacology*
  • Folic Acid Antagonists / chemical synthesis
  • Folic Acid Antagonists / pharmacology*
  • Lactobacillus casei / enzymology
  • Models, Molecular
  • Structure-Activity Relationship
  • Thymidylate Synthase / antagonists & inhibitors*

Substances

  • Enzyme Inhibitors
  • Folic Acid Antagonists
  • Thymidylate Synthase