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Updated: Aug 20, 2026
Fluorescence-Based Detection of FEN1 Nuclease Activity and Screening of Small-Molecule Inhibitors
Published on: June 27, 2025
The identification and optimization of a N-hydroxy urea series of flap endonuclease 1 inhibitors
L Nathan Tumey1, David Bom, Bayard Huck
1Athersys, Inc., 3201 Carnegie Ave., Cleveland, OH 44115, USA. ntumey@athersys.com
Abstract:
Flap endonuclease-1 (FEN1) is a key enzyme involved in base excision repair (BER), a primary pathway utilized by mammalian cells to repair DNA damage. Sensitization to DNA damaging agents is a potential method for the improvement of the therapeutic window of traditional chemotherapeutics. In this paper, we describe the identification and SAR of a series of low nanomolar FEN1 inhibitors. Over 1000-fold specificity was achieved against a related endonuclease, xeroderma pigmentosum G (XPG). Two compounds from this series significantly potentiate the action of methyl methanesulfonate (MMS) and temozolamide in a bladder cancer cell line (T24). To our knowledge, these are the most potent endonuclease inhibitors reported to date.
Insights
Researchers identified potent Flap endonuclease-1 (FEN1) inhibitors to enhance chemotherapy. These novel compounds show high specificity and potentiate DNA damaging agents in bladder cancer cells, offering a promising therapeutic strategy.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Flap endonuclease-1 (FEN1) is crucial for DNA repair via base excision repair (BER) in mammalian cells.
- Enhancing cancer cell sensitivity to DNA damaging agents can improve chemotherapy efficacy.
- FEN1 inhibitors represent a potential strategy to overcome therapeutic resistance.
Purpose of the Study:
- To identify and characterize novel, potent inhibitors of Flap endonuclease-1 (FEN1).
- To explore the structure-activity relationship (SAR) of these FEN1 inhibitors.
- To evaluate the potential of FEN1 inhibitors to sensitize cancer cells to chemotherapeutic agents.
Main Methods:
- Identification and synthesis of a series of FEN1 inhibitors.
- Structure-activity relationship (SAR) studies to optimize inhibitor potency and specificity.
- Enzyme inhibition assays to determine potency and selectivity against related endonucleases like xeroderma pigmentosum G (XPG).
- Cell-based assays using a bladder cancer cell line (T24) to assess potentiation of DNA damaging agents (MMS, temozolamide).
Main Results:
- Discovery of low nanomolar FEN1 inhibitors with over 1000-fold specificity against XPG.
- Two lead compounds demonstrated significant potentiation of methyl methanesulfonate (MMS) and temozolamide in T24 bladder cancer cells.
- The identified inhibitors are among the most potent endonuclease inhibitors reported to date.
Conclusions:
- Novel, highly specific, and potent FEN1 inhibitors have been developed.
- These inhibitors show promise in sensitizing bladder cancer cells to conventional chemotherapeutics.
- FEN1 inhibition represents a viable strategy for enhancing cancer therapy outcomes.
