FEN1-IN-4 (Compound 2) is a human flap endonuclease-1 (hFEN1) inhibitor[1].

FEN1 inhibition selectively impairs proliferation of colon cancer cells deficient in Cdc4 and Mre11a, both frequently mutated in colorectal cancers. FEN1 has also emerged as a potential chemosensitizing target due to its role in LP-BER since it is critical for repair of Methyl methanesulfonate-induced alkylation damage, and its knockdown or inhibition increases sensitivity to Temozolomide in glioblastoma and colorectal cancer cell lines[1].

[1]. Jack C Exell, et al. Cellularly Active N-hydroxyurea FEN1 Inhibitors Block Substrate Entry to the Active Site. Nat Chem Biol. 2016 Oct;12(10):815-21.