Novel Chemical Strategies for Thymidylate Synthase Inhibition

Abstract

Thymidylate synthase (TS) is a well-validated target for cancer chemotherapy. TS was established as the principal target of the widely used anticancer drug 5-fluorouracil (5FU). The 5FU metabolite FdUMP forms a covalent complex with TS that is stabilized by 5-formyl tetrahydrofolate (leucovorin; LV). Numerous chemical strategies have been employed to develop novel TS inhibitors that are superior to 5FU/LV. 5FU is non-ideal as a TS-inhibitory drug because it is only inefficiently converted to FdUMP, while the remainder of the administered dose is converted to toxic metabolites. My laboratory has explored the utility of FdUMP[N] compounds (oligodeoxynucleotides comprised of FdUMP nucleotides) as FdUMP pro-drugs. FdUMP[N] compounds result in potent TS-inhibition, and display many advantages relative to 5FU/LV. A number of other chemical strategies have also been employed to develop pro-drugs, or metabolic precursors of FdUMP, and several of these strategies will be reviewed. In addition to chemical strategies to develop FdUMP pro-drugs, a number of chemical strategies have been devised to develop molecules that resemble the reduced folate co-factor required for TS catalysis. The synthesis of antifolates that have TS-inhibitory activity, such as Raltitrexed, has resulted in compounds that are effective and specific TS-inhibitors and, in some cases, have clinical potential. Chemical strategies that target TS mRNA for destruction are also being explored as potential chemotherapeutics. These diverse chemical approaches to control TS activity in tumor cells for the treatment of cancer will be reviewed.

Design, Synthesis, and Biological Evaluation of Classical and Nonclassical 2-Amino-4-oxo-5-substituted-6-methylpyrrolo[3,2-d]pyrimidines as Dual Thymidylate Synthase and Dihydrofolate Reductase Inhibitors

“…The mixture was neutralized with AcOH, and the methanol was removed under reduced pressure. To the residue was added water (20 mL), and the pH value was adjusted to 10-11 by adding NH 3 •H 2 O. The solid was collected by filtration and washed well with water.…”

“…The solid was collected by filtration and washed well with water. The resulting solid was added to 1 N NaOH (2 mL), and the mixture was heated at 55°C for 3 h. The mixture was cooled and neutralized with acetic acid, and then the pH of the mixture was adjusted to 10-11 by adding NH 3 •H 2 O. The solid was collected by filtration.…”

“…The solid was dissolved in MeOH and CHCl 3 (1:1, 5 mL), and 1 g of silica gel was added. The solvent was removed under reduced pressure to form a plug, which was loaded at the top of a silica gel column (15 mm × 150 mm) and eluted with 5% MeOH in CHCl 3 (containing 0.5% NH 3 •H 2 O). Fractions containing the desired compound (TLC) were pooled and evaporated to afford 5 (35% for three steps) as an off-white solid: mp >250 °C; R f = 0.46 (MeOH/CHCl 3 , 1:10); 1 H NMR (DMSO-d 6 ) † 2.14 (s, 3 H, CH 3 …”

“…The resulting precipitate was collected by filtration and dried in vacuo. The crude product was purified by silica gel column chromatography, eluting with 5% MeOH/CHCl 3 Stereoview of compound 4 superimposed on SRI 9662 in human DHFR (PDB code 1KMV). 38 The hydrophobic interaction between C7 and Phe31 is shown.…”

“…1,2 Inhibitors of folate-dependent enzymes in cancer, microbial, and protozoan cells provide compounds that have found clinical utility as antitumor, antimicrobial, and antiprotozoal agents. 3,4 Thymidylate synthase (TS a ),which catalyzes the reductive methylation of deoxyuridylate (dUMP) to deoxythymidylate (dTMP), has been of particular interest. 5 This reaction affords 7,8-dihydrofolate (7,, which is reduced by dihydrofolate reductase (DHFR) 6 to tetrahydrofolate (THF).…”