Structure–Activity Relationships and Antileukemia Effects of the Tricyclic Benzoic Acid FTO Inhibitors

Abstract

The N 6-methyladenosine (m6A) demethylase FTO is overexpressed in acute myeloid leukemia (AML) cells and promotes leukemogenesis. We previously developed tricyclic benzoic acid FB23 as a highly potent FTO inhibitor in vitro. However, it showed a moderate antiproliferative effect on AML cells. In this work, we performed a structure–activity relationship study of tricyclic benzoic acids as FTO inhibitors. The analog 13a exhibited excellent inhibitory effects on FTO similar to that of FB23 in vitro. In contrast to FB23, 13a exerted a strong antiproliferative effect on AML cells. Like FTO knock down, 13a upregulated ASB2 and RARA expression and increased the protein abundance while it downregulated MYC expression and decreased MYC protein abundance. These genes are key FTO targets in AML cells. Finally, 13a treatment improved the survival rate of MONOMAC6-transplanted NSG mice. Collectively, our data suggest that targeting FTO with tricyclic benzoic acid inhibitors may be a potential strategy for treating AML.

Rational Design of RNA Demethylase FTO Inhibitors with Enhanced Antileukemia Drug-Like Properties

“…We further determined their half-maximal inhibitory concentration (IC 50 ) values using the PAGE-based assay (Figures A–D and S3). The IC 50 values of the 11 FTO inhibitors range from 16.8 ± 0.9 to 0.8 ± 0.1 μM, with compound 41 having an IC 50 value of 0.8 ± 0.1 μM, which is comparable to that of the previously reported tricyclic benzoic acid FTO inhibitor, 13a /Dac85 …”

“…SAR analysis reveals that the FTO inhibitors with flexible alkaline side chain substitution at the 6-position of benzoic acid exhibit better activity than those with flexible alkaline side chain substitution at the 5-position. Further c log P and LipE assessments indicate that FTO inhibitor 44 /ZLD115 achieves a better balance between their potency and ADME properties than the previously reported FTO inhibitors, FB23 and 13a /Dac85 . NMR titration shows interaction between FTO and 22 or 44 /ZLD115.…”

“…This inhibitor displays comparable enzymatic and cellular activities with FB23 and FB23-2, respectively. 42 However, the drug-like properties of these tricyclic benzoic acids, FB23 and 13a/Dac85, are not ideal due to their rigid structures, which may hinder further clinical development.…”

“…Thus, the catalytic core domain of FTO exhibits two binding sites that can be used for chemical intervention: a substrate and a 2-OG pocket. The determination of the crystal structure of FTO protein provides a structural basis for the development of small-molecule FTO inhibitors. , In 2012, we reported the first FTO inhibitor, rhein, and researchers have been interested in developing FTO inhibitors ever since. ,− The currently reported FTO inhibitors can be divided into the following four categories according to the mode of actions: (A) substrate-competitive inhibitors, such as rhein, meclofenamic acid (MA), N -CDPCB, fluorescein, CHTB, radicicol, FB23, FB23-2, Dac51, FTO-4, and TR-FTO-43N; ,− (B) 2-OG-competitive inhibitors, such as pyridine-2,4-dicarboxylate and R -2HG; , (C) substrate/2-OG dual competitive inhibitors, such as IOX3, entacapone, and HZ-MA hybrid; ,− and (D) inhibitors with unverified mechanisms, such as nafamostat mesilate, clausine E, CS1, CS2, diacerein, and saikosaponin D (Figure S1). − …”

Emerging roles of m6A RNA modification in cancer therapeutic resistance

“…For immunotherapy, another inhibitor Dac5 relived the constraints on T cells activation and functions imposed by FTO, which improves the ICB efficacy in melanoma [ 151 ]. Recent advances showed that the FB23 analog, FB23-13a exerted a stronger anti-proliferative effect on AML cells both in vitro and in vivo [ 164 ]. Recent researches made favorable progressions in more tumor types rather than AML and glioma.…”