Research paperBenzoxazinone-containing 3,5-dimethylisoxazole derivatives as BET bromodomain inhibitors for treatment of castration-resistant prostate cancer
Graphical abstract
Introduction
Prostate cancer, a commonly diagnosed cancer, is a leading cause of cancer-related deaths. Castration-resistant prostate cancer (CRPC), a lethal form of this disease, is largely driven by increased expression and activity of the androgen receptor (AR) [[1], [2], [3]]. AR signaling is the major driver for progression to CRPC, after which most tumors continue to rely on AR signaling [[4], [5], [6]]. The standard treatment for prostate cancer is androgen deprivation therapy (ADT). However, the disease often progresses to CRPC and eventually develops resistance to second generation drugs such as abiraterone and enzalutamide [7]. Consequently, alternative approaches to elimination of AR signaling are needed for the treatment of CRPC [8,9].
The bromodomain and extra-terminal (BET) family proteins consists of BRD2, BRD3, BRD4 and BRDT, which “read” acetyl lysines that translate chromatin status into transcription activation through RNA polymerase II. BET bromodomain inhibitors show therapeutic potential in several conditions including inflammation and oncologic diseases. Several classes of BET inhibitors with different selectivity profiles have been identified and have demonstrated therapeutic potential for various human cancers [1,[10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35]]. BET bromodomains are key regulators of AR-, ERG-, and c-Myc-mediated transcription in CRPC, and they have been proposed as novel epigenetic targets for the treatment of CRPC [36]. BET inhibitors such as (6S)-4-(4-chlorophenyl)-2,3,9-trimethyl-6H-thieno[3,2-f][1,2,4]triazolo[4,3-a][1,4]-diazepine-6-acetic acid 1,1-dimethylethyl ester ((+)-JQ1), (1), (S)-2-(4-(4-chloro-phenyl)-2,3,9-trimethyl-6H-thieno[3,2-f][1,2,4]-triazolo [4,3-a]-[1,4]diazepin-6-yl)-N-(4-hydroxyphenyl)acetamide (I-BET762), (2), and compound 3 (OTX-015) have also been identified in an alternative strategy to target AR-driven cancers (Fig. 1) [1,2,37,38]. BET bromodomain inhibition has been shown to be more efficacious than direct AR antagonism in CRPC xenograft models [2]. Several BET inhibitors, compound 2 from GlaxoSmithkline [1,20,37,39], compound 3 from Merck [29,[40], [41], [42]], ZEN003694 (structure not disclosed) from Zenith Epigenetics [43] and GS-5829 (structure not disclosed) from Gilead [44] are currently being evaluated in clinical trials as a single agent or in combination with an anti-androgen in patients with CRPC. However, reports on the efficacy in CRPC of the pharmacologic inhibition by BET bromodomain inhibitors are still limited. New, potent and specific BET bromodomain inhibitors with different chemotypes are needed in order to explore therapeutic possibilities in human diseases such as CRPC.
In this article, we report the structure-based design and biological evaluation of benzoxazinone-containing 3,5-dimethylisoxazole derivatives as new BET bromodomain inhibitors with promising therapeutic effects.
Section snippets
Design of new BET inhibitors containing a 2H-benzo[b][1,4]oxazin-3(4H)-one scaffold
Several recent reports have described the 3,5-dimethylisoxazole moiety as an acetyl-lysine mimic [12,13,16,27,[45], [46], [47]]. Our design of a new class of BET inhibitors began with analysis of the binding mode of compound 5 with in complex with BRD4(1) (PDB ID: 3SVF, Fig. 2A and B). The 3,5-dimethylisoxazole moiety binds in the acetyl lysine binding site of BRD4(1) and interacts with the conserved residues Asn140 and Tyr97 through direct hydrogen bonds and indirect hydrogen bonds via a
Conclusions
In this study, we report the structure-based design, synthesis, and evaluation of a new class of BET bromodomain inhibitors. Following a structural analysis, a series of benzoxazinone-containing 3,5-dimethylisoxazole derivatives were designed and synthesized. The most promising compound, (R)-12 binds to BRD4(1) with an IC50 of 100 nM in the AlphaScreen assay and a Kd value of 110 nM in the ITC assay. This compound also exhibits excellent selectivity over other non-BET bromodomain-containing
General chemistry
The requisite reagents and solvents were obtained from commercial suppliers and used without further purification. Flash chromatography was performed using silica gel (300–400 mesh). All reactions were monitored by TLC, using silica gel plates with fluorescence F254 and UV light visualization. 1H NMR spectra were recorded on a Bruker AV-400 spectrometer at 400 MHz or AV-500 spectrometer at 500 MHz. 13C NMR spectra were recorded on a Bruker AV-500 spectrometer at 125 MHz. Coupling constants (J)
Author contributions
The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.
Conflicts of interest
The authors declare no competing financial interest.
Acknowledgments
We gratefully acknowledge financial support from the National Natural Science Foundation of China (grant 81673357 and 21602222), the “Personalized Medicines − Molecular Signature-based Drug Discovery and Development”, Strategic Priority Research Program of the Chinese Academy of Sciences (grant No. XDA12020363), the Chinese National Programs for Key Research and Development (grant 2016YFB0201701), the Natural Science Foundation of Guangdong Province (2015A030312014), the National R&D
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2024, European Journal of Medicinal ChemistryDesign, synthesis, and evaluation of novel pyridone derivatives as potent BRD4 inhibitors for the potential treatment of prostate cancer
2022, Bioorganic ChemistryCitation Excerpt :The inhibition of BRD4 can disrupt the binding of P-TEFb with histones and reduce the expression of c-Myc, representing a feasible approach for the treatment of various c-Myc-dependent cancers [13]. Recent reports have indicated that BRD4 plays a vital role in the regulation of AR signaling pathway and oncogenic c-Myc in CRPC [14,15]. A few BRD4 inhibitors, such as JQ1 [16], Y06036 [17], OTX015 [18], I-BET-762 [19], GS-5829 [20], and ABBV-744 [21,22] have been reported to show potent antitumor activities in AR-positive prostate cancer (Fig. 1).
Discovery and optimization of novel N-benzyl-3,6-dimethylbenzo[d]isoxazol-5-amine derivatives as potent and selective TRIM24 bromodomain inhibitors with potential anti-cancer activities
2020, Bioorganic ChemistryCitation Excerpt :CRPC is generally fatal and these patients are in significant need of more effective treatments such as targeted therapeutic drugs. In recent years, we have been focused on development of small molecule inhibitors of BCPs and nuclear receptors which are potential therapeutic targets for CRPC [18–22]. Pioneer work by Brown and others supported that the TRIM24 mediated CRPC growth through its bromodomain and LXXLL motif and suggested that the bromodomain was a potential drug target [11,23–25].
Novel phenanthridin-6(5H)-one derivatives as potent and selective BET bromodomain inhibitors: Rational design, synthesis and biological evaluation
2019, European Journal of Medicinal ChemistryCitation Excerpt :Disrupting the protein-protein interactions between bromodomain and KAc by inhibitors can be a viable therapeutic target for many diseases [9,10]. In the last few years, a number of high-affinity small molecule BET inhibitors have been identified [11–16]. Till now, over 20 clinical trials are underway for studying the effects of BET family inhibition as anti-cancer or anti-inflammatory therapies [17,18].
Design, synthesis and biological evaluation of novel indole derivatives as potential HDAC/BRD4 dual inhibitors and anti-leukemia agents
2019, Bioorganic ChemistryCitation Excerpt :On the other hand, the SAR of BRD4 inhibitors have been carefully studied. Many BRD4 inhibitors consist of a hydrogen bond acceptor group as a mimic of Kac such as 3, 5-dimethylisoxazole, which interact with the conserved asparagine (Asn140), and a hydrophobic group coupled with the hydrogen bond acceptor group via a parent nucleus, which occupies the groove of WPF shelf [24–26] (Fig. 2A). It is notable that the ZA channel, a hydrophobic tunnel connects BRD4 active pocket and solvent area, is not fully occupied.