BG45

Description:

IC50: 289 nM

Histone deacetylases (HDACs) represent novel molecular targets for the treatment of various types of cancers including multiple myeloma (MM). Many HDAC inhibitors have already shown remarkable anti-tumor activities in the preclinical studies, however, their clinical utility is limited due to unfavorable toxicities associated with their broad range HDAC inhibitory effects. BG45 is a novel small molecule HDAC3-selective inhibitor.

In vitro: BG45 is reported as an HDAC class I inhibitor with selectivity for HDAC3 over HDAC1, 2. Consistent with HDAC3 knockdown data, BG45 significantly inhibited MM cell growth dose-dependently. Importantly, BG45 also triggered a potent growth inhibitory effect against patient-derived MM cells, without affecting normal donor PBMCs [1].

In vivo: BG45 significantly inhibited MM tumor growth in a dose-dependent fashion. For example, significant differences were observed in control versus BG45 15 mg/kg, control versus BG45 50 mg/kg, and BG45 15 mg/kg versus BG45 50 mg/kg at day 22. Moreover, BG45 50 mg/kg in combination with bortezomib enhanced either single agent activity further. These results confirmed that BG45 triggers in vivo anti-MM activities [1].

Clinical trial: Up to now, BG45 is still in the preclinical development stage.

Reference:
[1] Minami J, Suzuki R, Mazitschek R, Gorgun G, Ghosh B, Cirstea D, Hu Y, Mimura N, Ohguchi H, Cottini F, Jakubikova J, Munshi NC, Haggarty SJ, Richardson PG, Hideshima T, Anderson KC.  Histone deacetylase 3 as a novel therapeutic target in multiple myeloma. Leukemia. 2014 Mar;28(3):680-9.


Design, synthesis and biological screening of 2-aminobenzamides as selective HDAC3 inhibitors with promising anticancer effects.[Pubmed:30171982]

Eur J Pharm Sci. 2018 Nov 1;124:165-181.

Histone deacetylases (HDACs) have been found as a potential target for anticancer therapy. A number of HDAC inhibitors have been used pre-clinically and clinically as anticancer agents. In the current study, we have designed and synthesized compound 12a by combining the scaffolds of CI-994 and BG45. Moreover, the structure of compound 12a was optimized and a series of 2-aminobenzamide derivatives were synthesized further. These compounds were tested for their HDAC inhibitory activity and found to be efficient HDAC inhibitors. Compound 26c showed 11.68-fold HDAC3 selectivity over pan HDACs, better than the prototype HDAC3 inhibitor BG45. Most of these compounds exhibited antiproliferative activity in both B16F10 and HeLa cell lines. Particularly, compound 26c exhibited better antitumor efficacy in the cell lines compared to the prototype inhibitors CI-994 and BG45. It was also found to promote apoptosis as well as induced significant cell growth arrest in the G2/M phase of cell cycle in B16F10 melanoma cells. This work may provide significant insight regarding structural information to design newer small molecule HDAC3 inhibitors to fight against the target specific malignancies in future.

Metformin facilitates BG45induced apoptosis via an antiWarburg effect in cholangiocarcinoma cells.[Pubmed:29484415]

Oncol Rep. 2018 Apr;39(4):1957-1965.

Cholangiocarcinoma (CCA) is a highly lethal malignancy with an often late diagnosis and consequent poor prognosis. Chemotherapy is the only therapeutic strategy for most patients. Compared to normal cells, tumor cells preferentially metabolize glucose to lactate, even in aerobic conditions. Such metabolic alterations not only support the growth and invasion of tumor cells, but also promote their chemoresistance. The purpose of our study was to explore the role of metformin in regulating the metabolism of CCA, as well as to investigate whether metformin could act as a chemosensitizer of the HDAC3 inhibitor BG45, and therefore have potential for the treatment of CCA. Through bioinformatic analysis, we found that aberrant metabolism contributed to the proliferation of CCA cells. Seahorse XF96 Extracellular Flux Analyzer analysis and lactate production analysis showed that metformin could act as a suppressor of the Warburg effect in CCA cells. Western blotting showed that metformin decreased the expression of LDHA, which plays a key role in the Warburg effect. However, suppression of the Warburg effect was not sufficient to induce CCA cellular apoptosis. According to our previous research, which showed that an HDAC3 inhibitor (MI192) was involved in CCA apoptosis, we observed that metformin combined with BG45 (a novel specific HDAC3 inhibitor) effectively induced the apoptosis of CCA cells in vitro. Furthermore, in vivo experiments revealed that the combined treatment with metformin and BG45 markedly reduced CCA growth in a CCA xenograft model. Our data revealed that reversing the Warburg effect with metformin sensitizes cells to the antitumor effects of HDAC3 inhibitors. This provides a rationale for using the combination of metformin and BG45 as a new therapeutic strategy in the treatment of CCA.

Histone deacetylase inhibitor BG45-mediated HO-1 expression induces apoptosis of multiple myeloma cells by the JAK2/STAT3 pathway.[Pubmed:29049036]

Anticancer Drugs. 2018 Jan;29(1):61-74.

Multiple myeloma (MM) is a hematological malignancy that is characterized by the clonal expansion of plasma cells in the bone marrow. Histone deacetylases (HDACs) represent a new type of molecular targeted therapy for different types of cancers and promising targets for myeloma therapy. We showed that HDAC3 mRNA and protein levels of CD138 mononuclear cells from MM patients were higher than those in healthy donors. Therefore, we investigated the effects of a novel class I HDAC inhibitor BG45 on MM cells in vitro. BG45 downmodulated heme oxygenase 1 (HO-1) when class I HDACs decreased in MM cells. HO-1 is a target for the treatment of MM. Moreover, BG45 induced hyperacetylation of histone H3 and inhibited the growth, especially the apoptosis of MM cell lines. Treatment with BG45 induced apoptosis by downregulating bcl-2 and Bcl-xl, upregulating Bax and other antiapoptotic proteins and activating poly(ADP-ribose)polymerase, and decreasing protein levels of p-JAK2 and p-STAT3. These effects were partly blocked by HO-1. Correspondingly, BG45 led to an accumulation in the G0/G1 phase, accompanied by decreased levels of CDK4 and phospho-retinoblastoma protein, an increased level of p21, and a moderately reduced level of CDK2. Clinical use of single agents was limited because of toxic side effects and drug resistance. However, combining BG45 with lenalidomide exerted synergistic effects. In conclusion, we verified the potent antimyeloma activity of this novel HDAC inhibitor and that the combination of BG45 and lenalidomide is a new method for MM treatment. Thus, BG45 may be applicable to the treatment of MM and other hematological malignancies.

HDAC3 regulates DNMT1 expression in multiple myeloma: therapeutic implications.[Pubmed:28490812]

Leukemia. 2017 Dec;31(12):2670-2677.

Epigenetic signaling pathways are implicated in tumorigenesis and therefore histone deacetylases (HDACs) represent novel therapeutic targets for cancers, including multiple myeloma (MM). Although non-selective HDAC inhibitors show anti-MM activities, unfavorable side effects limit their clinical efficacy. Isoform- and/or class-selective HDAC inhibition offers the possibility to maintain clinical activity while avoiding adverse events attendant to broad non-selective HDAC inhibition. We have previously reported that HDAC3 inhibition, either by genetic knockdown or selective inhibitor BG45, abrogates MM cell proliferation. Here we show that knockdown of HDAC3, but not HDAC1 or HDAC2, as well as BG45, downregulate expression of DNA methyltransferase 1 (DNMT1) mediating MM cell proliferation. DNMT1 expression is regulated by c-Myc, and HDAC3 inhibition triggers degradation of c-Myc protein. Moreover, HDAC3 inhibition results in hyperacetylation of DNMT1, thereby reducing the stability of DNMT1 protein. Combined inhibition of HDAC3 and DNMT1 with BG45 and DNMT1 inhibitor 5-azacytidine (AZA), respectively, triggers synergistic downregulation of DNMT1, growth inhibition and apoptosis in both MM cell lines and patient MM cells. Efficacy of this combination treatment is confirmed in a murine xenograft MM model. Our results therefore provide the rationale for combination treatment using HDAC3 inhibitor with DNMT1 inhibitor to improve patient outcome in MM.

Histone deacetylase 3 as a novel therapeutic target in multiple myeloma.[Pubmed:23913134]

Leukemia. 2014 Mar;28(3):680-9.

Histone deacetylases (HDACs) represent novel molecular targets for the treatment of various types of cancers, including multiple myeloma (MM). Many HDAC inhibitors have already shown remarkable antitumor activities in the preclinical setting; however, their clinical utility is limited because of unfavorable toxicities associated with their broad range HDAC inhibitory effects. Isoform-selective HDAC inhibition may allow for MM cytotoxicity without attendant side effects. In this study, we demonstrated that HDAC3 knockdown and a small-molecule HDAC3 inhibitor BG45 trigger significant MM cell growth inhibition via apoptosis, evidenced by caspase and poly (ADP-ribose) polymerase cleavage. Importantly, HDAC3 inhibition downregulates phosphorylation (tyrosine 705 and serine 727) of signal transducers and activators of transcription 3 (STAT3). Neither interleukin-6 nor bone marrow stromal cells overcome this inhibitory effect of HDAC3 inhibition on phospho-STAT3 and MM cell growth. Moreover, HDAC3 inhibition also triggers hyperacetylation of STAT3, suggesting crosstalk signaling between phosphorylation and acetylation of STAT3. Importantly, inhibition of HDAC3, but not HDAC1 or 2, significantly enhances bortezomib-induced cytotoxicity. Finally, we confirm that BG45 alone and in combination with bortezomib trigger significant tumor growth inhibition in vivo in a murine xenograft model of human MM. Our results indicate that HDAC3 represents a promising therapeutic target, and validate a prototype novel HDAC3 inhibitor BG45 in MM.