Resistance-modifying agents. 5. Synthesis and biological properties of quinazolinone inhibitors of the DNA repair enzyme poly(ADP-ribose) polymerase (PARP)

J Med Chem. 1998 Dec 17;41(26):5247-56. doi: 10.1021/jm980273t.


Clinical studies concerning the role of poly(ADP-ribose) polymerase (PARP) in the repair of drug- and radiation-induced DNA damage have been impeded by the poor solubility, lack of potency, and limited specificity of currently available inhibitors. A series of 2-alkyl- and 2-aryl-substituted 8-hydroxy-, 8-methoxy-, and 8-methylquinazolin-4(3H)-ones has been synthesized and evaluated for PARP inhibitory activity in permeabilized L1210 murine leukemia cells. 8-Methoxy- and 8-methylquinazolinones (14-34) were readily prepared by acylation of 3-substituted anthranilamides with the appropriate acid chloride, followed by base-catalyzed cyclization. The requisite 8-hydroxyquinazolinones (6, 35-39) were synthesized by demethylation of the corresponding 8-methoxyquinazolinones with BBr3. N-Methylation of 8-methoxy-2-methylquinazolinone (15) with MeI, followed by O-demethylation by BBr3, afforded the control N3-methylquinazolinones 42 and 43, respectively. In general, an 8-hydroxy or 8-methyl substituent enhanced inhibitory activity in comparison with an 8-methoxy group. 2-Phenylquinazolinones were marginally less potent than the corresponding 2-methylquinazolinones, but the introduction of an electron-withdrawing or electron-donating 4'-substituent on the 2-aryl ring invariably increased potency. This was particularly evident in the 8-methylquinazolinone series (IC50 values 0.13-0.27 microM), which are among the most potent PARP inhibitors reported to date. N3-Methylquinazolinones 42 and 43 were essentially devoid of activity (IC50 values > 100 microM). In studies with L1210 cells in vitro, a concentration of 200 microM 8-hydroxy-2-methylquinazolinone (6, NU1025) (IC50 value 0.40 microM) potentiated the cytotoxicity of the monomethylating agent 5-(3-methyltriazen-1-yl)imidazole-4-carboxamide and gamma-radiation 3.5- and 1.4-fold, respectively, at the 10% survival level.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkylating Agents / pharmacology
  • Animals
  • Antineoplastic Agents / chemical synthesis*
  • Antineoplastic Agents / chemistry
  • Antineoplastic Agents / pharmacology
  • Cell Survival / drug effects
  • Cell Survival / radiation effects
  • DNA Repair*
  • Dacarbazine / analogs & derivatives
  • Dacarbazine / pharmacology
  • Drug Resistance, Neoplasm
  • Drug Screening Assays, Antitumor
  • Drug Synergism
  • Enzyme Inhibitors / chemical synthesis*
  • Enzyme Inhibitors / chemistry
  • Enzyme Inhibitors / pharmacology
  • Gamma Rays
  • Leukemia L1210 / pathology
  • Mice
  • Poly(ADP-ribose) Polymerase Inhibitors*
  • Quinazolines / chemical synthesis*
  • Quinazolines / chemistry
  • Quinazolines / pharmacology
  • Structure-Activity Relationship
  • Tumor Cells, Cultured


  • Alkylating Agents
  • Antineoplastic Agents
  • Enzyme Inhibitors
  • NU 1025
  • Poly(ADP-ribose) Polymerase Inhibitors
  • Quinazolines
  • Dacarbazine
  • 5-(3-methyl-1-triazeno)imidazole-4-carboxamide