AR-42 (OSU-HDAC42)

AR-42 (also known as OSU-HDAC42), a derivative of hydroxamate-tethered phenylbutyrate, is a novel and potent inhibitor of histone deacetylase (HDAC) that potently inhibits the activity of HDAC with 50% inhibition concentration IC₅₀ value of 16 nM and induces histone H3 acetylation, α-tubulin acetylation and p21 up-regulation, which have been considered as the hallmark indicators of HDAC inhibition. AR-42 has been found to modulate several apoptosis inhibitors as well as cell survival regulator, including Akt, Bcl-xL, Bax, Ku70 and surviving, and exert potent antitumor activity against multiple tumor types, such as human prostate and hepatic cancers, at least partially through PI3K/Akt pathway inhibition.

Reference

Matthew L. Bush†, Janet Oblinger†, Victoria Brendel, Griffin Santarelli, Jie Huang, Elena M. Akhmametyeva, Sarah S. Burns, Justin Wheeler, Jeremy Davis, Charles W. Yates, Abhik R. Chaudhury, Samuel Kulp, Ching-Shih Chen, Long-Sheng Chang, D. Bradley Welling, and Abraham Jacob. AR42, a novel histone deacetylase inhibitor, as a potential therapy for vestibular schwannomas and meningiomas. Neuro-Oncology 13(9):983–999, 2011

Aaron M. Sargeant, Robert C. Rengel, Samuel K. Kulp, et al. OSU-HDAC42, a Histone Deacetylase Inhibitor, Blocks Prostate Tumor Progression in the Transgenic Adenocarcinoma of the Mouse Prostate Model Cancer Res 2008;68:3999-4009.

Qiang Lu, Da-Sheng Wang, Chang-Shi Chen, Yuan-Dong Hu, and Ching-Shih Chen. Structure-Based Optimization of Phenylbutyrate-Derived Histone Deacetylase

Inhibitors. J. Med. Chem. 2005, 48, 5530-5535

The Effect of a Histone Deacetylase Inhibitor (AR-42) on Canine Prostate Cancer Growth and Metastasis.[Pubmed:28181686]

Prostate. 2017 May;77(7):776-793.

BACKGROUND: Canine prostate cancer (PCa) is an excellent preclinical model for human PCa. AR-42 is a histone deacetylase inhibitor (HDACi) developed at The Ohio State University that inhibits the proliferation of several cancers, including multiple myeloma, lung, and hepatocellular cancer. In this study, we investigated whether AR-42 would prevent or decrease. The growth and metastasis of a canine PCa (Ace-1 cells) to bone in vitro and in vivo. METHODS: Proliferation, cell viability, invasion, and metastasis of a canine prostate cancer cell line (Ace-1) were measured following treatment with AR-42. Expression of anoikis resistance, epithelial-to-mesenchymal transition (EMT), and stem cell-related markers were also evaluated. To assess the efficacy of AR-42 on prevention of PCa metastasis to bone, Ace-1 cells were injected in the left cardiac ventricle of nude mice, mice were treated with AR-42, and the incidence and growth of bone metastasis were measured. Bioluminescence was performed to monitor the bone metastases in nude mice. RESULTS: AR-42 inhibited the in vitro proliferation of Ace-1 cells in a time- and dose-dependent manner. The IC50 concentration of AR-42 for Ace-1 cells was 0.42 muM after 24 hr of treatment. AR-42 induced apoptosis, decreased cell migration, and increased the stem cell properties of Ace-1 cells in vitro. AR-42 downregulated E-cadherin, N-cadherin, TWIST, MYOF, anoikis resistance, and osteomimicry genes, while it upregulated SNAIL, PTEN, FAK, and ZEB1 gene expression in Ace-1 cells. Importantly, AR-42 decreased the bioluminescence and incidence of bone metastasis in nude mice. In addition, AR-42 induced apoptosis and altered the tumor cell morphology to an irregular cell phenotype with condensed chromatin in the bone metastases. CONCLUSION: AR-42 decreased PCa growth and bone metastasis, induced apoptosis, and downregulated osteomimicry genes in PCa cells in the bone microenvironment. Prostate 77:776-793, 2017. (c) 2017 Wiley Periodicals, Inc.

Suppression of Tumor Growth and Muscle Wasting in a Transgenic Mouse Model of Pancreatic Cancer by the Novel Histone Deacetylase Inhibitor AR-42.[Pubmed:27889645]

Neoplasia. 2016 Dec;18(12):765-774.

PURPOSE: Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer death in the United States. This study was aimed at evaluating the efficacy of AR-42 (formerly OSU-HDAC42), a novel histone deacetylase (HDAC) inhibitor currently in clinical trials, in suppressing tumor growth and/or cancer-induced muscle wasting in murine models of PDAC. EXPERIMENTAL DESIGN: The in vitro antiproliferative activity of AR-42 was evaluated in six human pancreatic cancer cell lines (AsPC-1, COLO-357, PANC-1, MiaPaCa-2, BxPC-3, SW1990). AsPC-1 subcutaneous xenograft and transgenic KP(fl/fl)C (LSL-Kras(G12D);Trp53(flox/flox);Pdx-1-Cre) mouse models of pancreatic cancer were used to evaluate the in vivo efficacy of AR-42 in suppressing tumor growth and/or muscle wasting. RESULTS: Growth suppression in AR-42-treated cells was observed in all six human pancreatic cancer cell lines with dose-dependent modulation of proliferation and apoptotic markers, which was associated with the hallmark features of HDAC inhibition, including p21 upregulation and histone H3 hyperacetylation. Oral administration of AR-42 at 50 mg/kg every other day resulted in suppression of tumor burden in the AsPC-1 xenograft and KP(fl/fl)C models by 78% and 55%, respectively, at the end of treatment. Tumor suppression was associated with HDAC inhibition, increased apoptosis, and inhibition of proliferation. Additionally, AR-42 as a single agent preserved muscle size and increased grip strength in KP(fl/fl)C mice. Finally, the combination of AR-42 and gemcitabine in transgenic mice demonstrated a significant increase in survival than either agent alone. CONCLUSIONS: These results suggest that AR-42 represents a therapeutically promising strategy for the treatment of pancreatic cancer.

Association of downregulated HDAC 2 with the impaired mitochondrial function and cytokine secretion in the monocytes/macrophages from gestational diabetes mellitus patients.[Pubmed:26936353]

Cell Biol Int. 2016 Jun;40(6):642-51.

Gestational diabetes mellitus (GDM) is associated with an increased risk of type 2 diabetes (T2DM) and cardiovascular diseases in later life, yet with underlying mechanisms unclear. The present study was to explore the association of upregulated histone deacetylase 2 (HDAC 2) with the impaired mitochondrial function and the cytokine secretion in the monocytes/macrophages from GDM patients. In this study, we examined the mitochondrial function, proinflamatory cytokine secretion and the HDAC 2 level in the serum or in the monocytes/macrophages from GDM patients, investigated the influence by HDAC 2 inhibitor, AR-42 (N-hydroxy-4-[[(2S)-3-methyl-2-phenylbutanoyl]amino]benzamide), on the mitochondrial function and cytokine secretion in the isolated GDM monocytes/macrophages. Results demonstrated an increased mitochondria size, mitochondrial superoxide and reactive oxygen species (ROS) production, and an undermined mitochondria membrane potential (MMP) in the GDM monocytes/macrophages. And the serum levels of interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha and IL-6 were also markedly higher in the GDM pregnancies, while the expression and activity of HDAC 2 was downregulated. Moreover, AR-42-mediated HDAC 2 inhibition in vitro contributed to the impaired mitochondrial function and the proinflamatory cytokine secretion. In conclusion, this study suggests an association of the impaired mitochondrial function and the promoted proinflamatory cytokine secretion with the reduced HDAC 2 activity in GDM. These findings may present HDAC 2 as a target for GDM treatment.

Preclinical Pharmacokinetics Study of R- and S-Enantiomers of the Histone Deacetylase Inhibitor, AR-42 (NSC 731438), in Rodents.[Pubmed:26943915]

AAPS J. 2016 May;18(3):737-45.

AR-42, a new orally bioavailable, potent, hydroxamate-tethered phenylbutyrate class I/IIB histone deacetylase inhibitor currently is under evaluation in phase 1 and 2 clinical trials and has demonstrated activity in both hematologic and solid tumor malignancies. This report focuses on the preclinical characterization of the pharmacokinetics of AR-42 in mice and rats. A high-performance liquid chromatography-tandem mass spectrometry assay has been developed and applied to the pharmacokinetic study of the more active stereoisomer, S-AR-42, when administered via intravenous and oral routes in rodents, including plasma, bone marrow, and spleen pharmacokinetics (PK) in CD2F1 mice and plasma PK in F344 rats. Oral bioavailability was estimated to be 26 and 100% in mice and rats, respectively. R-AR-42 was also evaluated intravenously in rats and was shown to display different pharmacokinetics with a much shorter terminal half-life compared to that of S-AR-42. Renal clearance was a minor elimination pathway for parental S-AR-42. Oral administration of S-AR-42 to tumor-bearing mice demonstrated high uptake and exposure of the parent drug in the lymphoid tissues, spleen, and bone marrow. This is the first report of the pharmacokinetics of this novel agent, which is now in early phase clinical trials.

Non-epigenetic function of HDAC8 in regulating breast cancer stem cells by maintaining Notch1 protein stability.[Pubmed:26625202]

Oncotarget. 2016 Jan 12;7(2):1796-807.

Here, we report a novel non-epigenetic function of histone deacetylase (HDAC) 8 in activating cancer stem cell (CSC)-like properties in breast cancer cells by enhancing the stability of Notch1 protein. The pan-HDAC inhibitors AR-42 and SAHA, and the class I HDAC inhibitor depsipeptide, suppressed mammosphere formation and other CSC markers by reducing Notch1 expression in MDA-MB-231 and SUM-159 cells. Interrogation of individual class I isoforms (HDAC1-3 and 8) using si/shRNA-mediated knockdown, ectopic expression and/or pharmacological inhibition revealed HDAC8 to be the primary mediator of this drug effect. This suppression of Notch1 in response to HDAC8 inhibition was abrogated by the proteasome inhibitor MG132 and siRNA-induced silencing of Fbwx7, indicating Notch1 suppression occurred through proteasomal degradation. However, co-immunoprecipitation analysis indicated that HDAC8 did not form complexes with Notch1 and HDAC inhibition had no effect on Notch1 acetylation. In a xenograft tumor model, the tumorigenicity of breast cancer cells was decreased by HDAC8 knockdown. These findings suggest the therapeutic potential of HDAC8 inhibition to suppress Notch1 signaling in breast cancer.