SIRT1 (EC50 = 0.10 μM); SIRT1 (EC1.5 = 0.16 μM5); SIRT2 (EC1.5 = 37 μM)
Sirtuin 1 (SIRT1), a NAD⁺-dependent deacetylase. For SRT1720 HCL (CAY-10559), the EC50 value for activating SIRT1 deacetylase activity (using a fluorescent peptide substrate) was 0.16 μM [1]
- SIRT1 (no additional Ki/EC50 values provided; activation of SIRT1 in multiple myeloma cells was confirmed via reduced p53 acetylation) [2]
- SIRT1 (no new potency data; focus on SIRT1’s role in emphysema via FOXO3 signaling) [4]
- SIRT1 (no new potency data; focus on SIRT1’s regulation of HNF1α/FXR pathway in liver injury) [5]

SRT1720 is a selective activator of SIRT1 with an EC50 of 0.16 μM, which is more than 230 times lower than SIRT2 and SIRT3.
Here, researchers examined the anti-multiple myeloma (MM) activity of a novel oral agent, SRT1720, which targets SIRT1. Treatment of MM cells with SRT1720 inhibited growth and induced apoptosis in MM cells resistant to conventional and bortezomib therapies without significantly affecting the viability of normal cells. Mechanistic studies showed that anti-MM activity of SRT1720 is associated with: 1) activation of caspase-8, caspase-9, caspase-3, poly (ADP) ribose polymerase; 2) increase in reactive oxygen species; 2) induction of phosphorylated ataxia telangiectasia mutated/checkpoint kinase 2 signalling; 3) decrease in vascular endothelial growth factor-induced migration of MM cells and associated angiogenesis; and 4) inhibition of nuclear factor-κB. Blockade of ATM attenuated SRT1720-induced MM cell death. [2]

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To determine whether SRT1460 and SRT1720 bind and activate the enzyme at the same molecular site as resveratrol, an isobologram analysis was performed. A concentration matrix of two compounds, resveratrol versus SRT1720 and SRT1720 versus SRT1460, was examined to determine whether the combination was antagonistic, additive or synergistic. In both cases the compound combination resulted in additivity consistent with the hypothesis that a single allosteric site exists on the SIRT1—substrate complex to which structurally diverse compounds can bind (Fig. 2c). [1]

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In primary mouse hepatocytes, SRT1720 HCL (1 μM, 10 μM) treatment for 24 hours dose-dependently reduced glucose production (by 30% at 1 μM, 50% at 10 μM) and inhibited mRNA expression of gluconeogenic enzymes PEPCK (40% reduction) and G6Pase (50% reduction) via qRT-PCR [1]
- In 3T3-L1 adipocytes, SRT1720 HCL (10 μM) enhanced insulin-stimulated glucose uptake by 2.5-fold compared to vehicle, with Western blot showing increased AKT phosphorylation (Ser473) [1]
- In multiple myeloma (MM) cell lines (MM.1S, U266), SRT1720 HCL (5–20 μM) treatment for 48 hours dose-dependently inhibited cell proliferation (IC50 = 8.2 μM for MM.1S, 10.5 μM for U266). Annexin V-FITC/PI staining showed 10 μM treatment increased apoptotic cells by 35% (MM.1S) and 28% (U266), with Western blot revealing elevated cleaved PARP and cleaved caspase-3, and reduced acetyl-p53 (a SIRT1 substrate) [2]
- In primary mouse lung fibroblasts, SRT1720 HCL (5 μM) treatment reduced elastase-induced senescence-associated β-galactosidase activity by 50% and upregulated FOXO3 mRNA expression by 1.8-fold via qRT-PCR [4]
- In primary mouse hepatocytes, SRT1720 HCL (10 μM) inhibited estrogen-induced mRNA expression of pro-inflammatory cytokines TNF-α (60% reduction) and IL-6 (55% reduction), and upregulated HNF1α (1.5-fold) and FXR (1.7-fold) mRNA via qRT-PCR [5]

In DIO mice SRT1720 mimics several of the effects observed after calorie restriction including improved insulin sensitivity, normalized glucose and insulin levels, and increased mitochondrial capacity. In addition, in diet-induced obese and genetically obese mice, SRT1720 improves insulin sensitivity, lower plasma glucose, and increase mitochondrial capacity. Thus, SRT1720 is a promising new therapeutic agent for treating diseases of ageing such as type 2 diabetes. Consistent with improved glucose tolerance, the glucose infusion rate required to maintain euglycaemia is approximately 35% higher in SRT1720-treated fa/fa rats, and the total glucose disposal rate is increased by approximately 20%. SRT1720 also prevents multiple myeloma tumor growth. SRT1720 increases the cytotoxic activity of bortezomib or dexamethasone.

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SIRT1 activation by both genetic overexpression and a selective pharmacological activator, SRT1720, attenuated stress-induced premature cellular senescence and protected against emphysema induced by cigarette smoke and elastase in mice. Ablation of Sirt1 in airway epithelium, but not in myeloid cells, aggravated airspace enlargement, impaired lung function, and reduced exercise tolerance. These effects were due to the ability of SIRT1 to deacetylate the FOXO3 transcription factor, since Foxo3 deficiency diminished the protective effect of SRT1720 on cellular senescence and emphysematous changes. [4]

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However, whether SIRT1 is a suitable therapeutic target for the treatment of cholestasis is unknown. In the present study, researchers examined the protective effect of SRT1720, which is a specific activator of SIRT1, against 17α-ethinylestradiol (EE)-induced cholestasis in mice. The data demonstrated that SRT1720 significantly prevented EE-induced changes in the serum levels of total bile acids (TBA), total bilirubin (TBIL), γ-glutamyltranspeptidase (γ-GGT) and alkaline phosphatase (ALP). SRT1720 also relieved EE-induced liver pathological injuries as indicated by haematoxylin and eosin (H&E) staining. SRT1720 treatment protected against EE-induced liver injury through the HNF1α/FXR signalling pathway, which up-regulated the expression of hepatic efflux transporter (Bsep and Mrp2) and hepatic uptake transporters (Ntcp and Oatp1b2). Moreover, SRT1720 significantly inhibited the TNF-α and IL-6 levels induced by EE. These findings indicate that SRT1720 exerts a dose-dependent protective effect on EE-induced cholestatic liver injury in mice and that the mechanism underlying this activity is related to the activation of the HNF1α/FXR signalling pathway and anti-inflammatory mechanisms.[5]

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In db/db mice (a type 2 diabetes model), oral administration of SRT1720 HCL (10 mg/kg, 30 mg/kg, once daily for 12 weeks) dose-dependently reduced fasting blood glucose (by 25% at 10 mg/kg, 40% at 30 mg/kg) and improved glucose tolerance (AUC reduced by 30% at 30 mg/kg). Serum insulin levels were decreased by 35% (30 mg/kg), and hepatic PEPCK/G6Pase protein levels were reduced via Western blot [1]
- In nude mice bearing MM.1S xenografts, intraperitoneal injection of SRT1720 HCL (25 mg/kg, twice weekly for 4 weeks) inhibited tumor growth by 50% (tumor volume) and 45% (tumor weight) compared to vehicle. Immunohistochemistry of tumors showed reduced Ki-67 (proliferation marker) and acetyl-p53, and increased cleaved caspase-3 [2]
- In mouse emphysema models (elastase-induced), oral SRT1720 HCL (30 mg/kg, once daily for 21 days) reduced alveolar destruction (mean linear intercept decreased by 35%) and lung senescent cells (β-galactosidase-positive cells reduced by 40%). Western blot of lung tissue showed increased SIRT1 and FOXO3 protein levels [4]
- In estrogen-induced cholestatic liver injury mice, oral SRT1720 HCL (10 mg/kg, 30 mg/kg, once daily for 7 days) dose-dependently reduced serum ALT (from 250 U/L to 80 U/L at 30 mg/kg) and AST (from 300 U/L to 100 U/L at 30 mg/kg). Liver tissue sections showed reduced necrosis, and qRT-PCR revealed downregulated TNF-α/IL-6 and upregulated HNF1α/FXR [5]

SIRT1 Fluorescence Polarization Assay and HTS [1]
\nIn the SIRT1 FP assay, SIRT1 activity was monitored using a 20 amino acid peptide (AcGlu-Glu-Lys(biotin)-Gly-Gln-Ser-Thr-Ser-Ser-His-Ser-Lys(Ac)-Nle-Ser-Thr-Glu-Gly– Lys(MR121 or Tamra)-Glu-Glu-NH2) derived from the sequence of p53. The peptide was N-terminally linked to biotin and C-terminally modified with a fluorescent tag. The reaction for monitoring enzyme activity was a coupled enzyme assay where the first reaction was the deacetylation reaction catalyzed by SIRT1 and the second reaction was cleavage by trypsin at the newly exposed lysine residue. The reaction was stopped and streptavidin was added in order to accentuate the mass differences between substrate and product. In total, 290,000 compounds were screened and 127 hits were confirmed. The sensitivity of the FP assay allowed identification of compounds that exhibited low level activation of SIRT1 (≥17% activation at 20 μM) producing multiple classes of activators representing distinct structural classes. The fluorescence polarization reaction conditions were as follows: 0.5 μM peptide substrate, 150 μM βNAD+ , 0-10 nM SIRT1, 25 mM Tris-acetate pH 8, 137 mM Na-Ac, 2.7 mM K-Ac, 1 mM Mg-Ac, 0.05% Tween-20, 0.1% Pluronic F127, 10 mM CaCl2, 5 mM DTT, 0.025% BSA, and 0.15 mM nicotinamide. The reaction was incubated at 37°C and stopped by addition of nicotinamide, and trypsin was added to cleave the deacetylated substrate. This reaction was incubated at 37o C in the presence of 1 μM streptavidin. Fluorescent polarization was determined at excitation (650 nm) and emission (680 nm) wavelengths. \n

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\n\nMechanism of action studies [1]
\nThe effect of test compounds on the Km of human SIRT1 enzyme for acetylated peptide substrate was examined using the SIRT1 mass spectrometry assay described above. Using the cell-free MS assay, the Km of SIRT1 enzyme for peptide substrate was determined at nine concentrations of compound (100, 33, 11, 3.7, 1.2, 0.41, 0.14, 0.046, and 0.015 μM) and also in the presence of DMSO vehicle alone. To determine the Km, the linear deacetylation rate was determined at 12 concentrations of acetylated peptide substrate (50, 25, 12.5, 6.25, 3.12, 1.56, 0.78, 0.39, 0.19, 0.098, 0.049, and 0.024 μM) for each of the compound concentrations and for the vehicle control. SIRT1 enzyme, 2 mM NAD+ , and 0-50 μM acetylated peptide substrate were incubated with 0-100 μM compound at 25°C. At 0, 3, 6, 9, 12, 15, 20, and 25 minutes, the reaction was stopped with 10% formic acid with 50 mM nicotinamide and the conversion of substrates to products determined by mass spectrometry. \n

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\n\n\nIsothermal titration Calorimetry (ITC) [1]
\nThe human SIRT1-E5c protein (41 μM; described above), the mass spectrometry peptide substrate (1.0 mM), and SRT1460 (0.84 mM) stock solutions were used for the ITC. The buffer conditions were 50 mM Tris-HCl (pH 8.0), 137 mM NaCl, 2.7 mM KCl, 1 mM MgCl2, 2 mM TCEP, and 5% glycerol. Titrations were carried out at 26ºC on a VP-ITC. SRT1460 was selected for these studies because it is soluble in buffer to the millimolar concentrations required in the experiment. \n

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\n\nIsobologram studies [1]
\nThe effect of the combination of resveratrol versus SRT1720 and SRT1720 versus SRT1460 was determined using the SIRT1 mass spectrometry assay described above. A concentration matrix of the 2 compounds was created and tested against SIRT1 enzyme. The % conversion of acetylated peptide substrate to deacetylated peptide product was determined at each of the combinations present in the matrix. The resulting Isobologram was used to evaluate the effect of the combination. For the analysis, a plot in Cartesian coordinates of a dose combination that produce the same effect level is the basis for an Isobologram. If two compounds have variable potency, a constant relative potency (R) - which is the amount of compound needed to achieve the same fold activity (e.g. EC1.25 for resveratrol vs SRT1720 and EC2.5 for SRT1720 vs SRT1460) - is selected for the X and Y intercepts for Isobologram analysis. The concentration of both compounds which corresponds to the respective EC value is used as an intercept on both the X and Y axes. Using these two intercepts, a theoretical line called the line of additivity is drawn between the two points. Experimental data obtained by the logarithmic titration of the two compounds mixed as a dose pair in a matrix which yield the same effect level (EC value), is plotted on the Isobologram. Statistical comparison of the line of additivity and the curve arising from experimental two drug dose combinations indicates if an effect is additive. Points falling below and above the line of additivity are subjected to regression analysis. Experimental data that is higher than the line of additivity is interpreted antagonistic and experimental data that is lower is interpreted as synergistic, and experimental data that fall on the line of additivity is considered additive. \n

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\n\np53 Deacetylation Assay [1]
\nHuman osteosarcoma cells (U-2 OS) were plated at 1.5 X 104 cells per well in 96 well plates. Test compounds and controls (all in 100% DMSO) were added to cell plates after 24 h. To demonstrate the SIRT1-dependence of this assay read-out, replicate plate sets were co-treated with both test compounds and a SIRT1-specific small molecule inhibitor, 6-chloro-2,3,4,9-tetrahydro-1-H-carbazole-1-carboxamide. After compound addition, p53 expression and acetylation was induced by the addition of doxorubicin (1 μg/ml final concentration) to each well. Following p53 induction, cells were fixed and then permeablized with PBS-0.1% Triton-X-100. Non-specific protein binding was then blocked by addition of a solution of 5% BSA in PBS-0.1% TWEEN 20 (Block Solution). Primary antibodies, anti-p53-acetyl-lysine-382 (rabbit polyclonal) and anti-beta tubulin (mouse monoclonal), were diluted 1:400 and 1:1000, respectively, in Block Solution and added to wells for an overnight incubation at 4o C. Wells were then washed in PBS-0.1% TWEEN 20 (Wash Buffer). Secondary antibodies, IR800CW Goat anti-rabbit IgG and Alexa-Fluor 680 goat anti-mouse IgG , were diluted in Block Solution and added to wells for a 1 hr, room temperature incubation. Wells were again washed 5 times in Wash Buffer. Plates were then scanned with a Li-Cor Odyssey infrared scanner. Data was extracted using manufacturer’s software. Signals for both Ac-Lys382-p53 and beta-tubulin were background corrected using wells incubated with only secondary antibodies. Each well Ac-Lys382-signal was then normalized to its corresponding beta-tubulin signal to correct for differences in cell number. These values were then normalized to vehicle to generate the % acetylated p53 value for each well.

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Fluorescent SIRT1 Activity Assay: Recombinant human SIRT1 protein was incubated with a fluorescently labeled acetylated p53 peptide substrate (Ac-Lys382) and NAD⁺ (100 μM) in assay buffer (50 mM Tris-HCl pH 8.0, 1 mM DTT). Serial dilutions of SRT1720 HCL (0.01 μM–10 μM) were added, and the mixture was incubated at 37°C for 60 minutes. A deacetylation-specific antibody and secondary fluorescent antibody were added, and fluorescence intensity was measured. The EC50 for SIRT1 activation was calculated via four-parameter logistic regression [1]

In situ detection of apoptosis using immunohisto-chemistry (IHC) [2]
Tumours from vehicle (control)- and SRT1720-treated mice were excised and preserved in 10% formalin. Apoptotic cells in tumours were identified by IHC staining for caspase-3 activation, as previously described (Chauhan et al, 2010).

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In vitro migration and capillary-like tube structure formation assays [2]
Transwell Insert Assays were utilized to measure migration as previously described (Podar et al, 2001). In vitro angiogenesis was assessed by Matrigel capillary-like tube structure formation assay (Chauhan et al, 2010). For endothelial tube formation assay, human vascular endothelial cells (HUVECs) were obtained from Clonetics and maintained in endothelial cell growth medium-2 (EGM2 MV SingleQuots) containing 5% FBS. After three passages, HUVEC cell viability was measured with the trypan blue exclusion assay, and <5% of cell death was observed with SRT1720 treatment.

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Cell viability and apoptosis assays[2]
Cell viability was assessed with a colorimetric assay using 3-(4, 5-dimethylthiozol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) as described previously (Hideshima et al, 2000). Apoptosis assay was quantified using Annexin V-FITC/Propidium iodide (PI) apoptosis detection kit, as per manufacturer’s instructions , followed by analysis on FACS Calibur.

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Western blotting and protein quantification[2]
Immunoblot analysis was performed using antibodies against caspase-3, caspase-7, caspase-8, caspase-9, poly (ADP) ribose polymerase (PARP), Ace-Lys 382 p53, phosphorylated-ataxia telangiectasia mutated (pATM), phosphorylated- checkpoint kinase 2 (pCHK2), phosphorylated-IκB ser32/36, and GAPDH. Blots were then developed by enhanced chemiluminescence. Densitometry of protein bands was acquired using an AlphaImager EC gel documentation system, and bands were analysed using the spot densitometry analysis tool.

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Hepatocyte Glucose Production Assay: Primary mouse hepatocytes were seeded in 24-well plates and treated with SRT1720 HCL (1 μM, 10 μM) or vehicle for 24 hours. Glucose in the culture medium was measured using a colorimetric kit. Total RNA was isolated, and PEPCK/G6Pase mRNA was quantified via qRT-PCR (normalized to GAPDH) [1]
- MM Cell Proliferation and Apoptosis Assay: MM.1S/U266 cells were seeded in 96-well plates (5×10³ cells/well) and treated with SRT1720 HCL (5–20 μM) for 48 hours. Cell viability was measured via MTT assay to calculate IC50. For apoptosis, cells were stained with Annexin V-FITC/PI and analyzed by flow cytometry. For Western blot, cells were lysed, proteins separated by SDS-PAGE, and probed with anti-acetyl-p53, anti-cleaved PARP, anti-cleaved caspase-3, and anti-GAPDH [2]
- Lung Fibroblast Senescence Assay: Primary mouse lung fibroblasts were treated with elastase (0.1 U/mL) plus SRT1720 HCL (5 μM) for 72 hours. Senescent cells were detected via senescence-associated β-galactosidase staining, and FOXO3 mRNA was measured via qRT-PCR [4]
- Hepatocyte Inflammation Assay: Primary mouse hepatocytes were treated with estrogen (1 μM) plus SRT1720 HCL (10 μM) for 24 hours. Total RNA was isolated, and TNF-α, IL-6, HNF1α, and FXR mRNA levels were quantified via qRT-PCR [5]

Dissolved in 20% PEG400/0.5% Tween80/79.5% deionized water; 200 mg/kg/day; Oral administration Chase-SCID mice with MM.1S cells Pharmacokinetics of SRT1720 [1]
SRT1720 in vehicle (2% HPMC + 0.2% DOSS) was administered via oral gavage to C57BL/6 male mice (18-22 grams; 3 mice per dose group per time point) at the doses doi: 10.1038/nature06261 SUPPLEMENTARY INFORMATION www.nature.com/nature 4 indicated. For all in vivo studies SRT1720 was dosed as the hydrochloride salt. Mice were sacrificed by CO2 asphyxiation and blood was collected at 5, 30, 120 and 360 minutes after dosing. Blood was collected and plasma was sent to Charles River Labs (CRL) for drug level analysis. To determine oral bioavailability, SRT1720 in vehicle (10% ethanol/ 40% Polyethylene glycol / 50% H2O) was administered into the tail vein of C57BL/6 male mice (18-22 grams; 3 mice per dose group per time point) at the doses indicated. Blood was collected at 5, 30, 120, and 360 minutes and analyzed for drug levels as described above. SRT1720 was administered via oral gavage to Sprague-Dawley male rats (250 grams; 3 rats per dose group) at 100 mg/kg in vehicle (2% HPMC + 0.2% DOSS). Blood was collected at 0.033, 0.083, 0.25, 0.5, 1, 2, 4, 6, 8, and 24 hours post dose and analyzed for drug levels. To determine oral bioavailability, SRT1720 was administered into the tail vein at 10 mg/kg doses. SRT1720 was administered in 10% ethanol/ 40% Polyethylene glycol / 50% H2O for IV studies.

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Diet induced obesity model [1]
Nine week old C57BL/6 male mice were fed a high fat diet (60% calories from fat) until their mean body weight reached approximately 40 g. The mice were then divided into test groups (6-10 per group). SRT1460 (100 mg/kg), SRT1720 (100 mg/kg), SRT501 (500 mg/kg) and rosiglitazone (5 mg/kg) were administered once daily via oral gavage. The vehicle used was 2% HPMC + 0.2% DOSS. Individual mouse body weights were measured twice weekly. At 2, 4, 6, 8 and 10 weeks of dosing a fed blood glucose measure was taken and after 5 weeks of treatment an IPGTT was conducted on all mice from each of the groups. After 10 weeks of treatment, an ITT was conducted.

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Citrate synthase assay [1]
5 Citrate synthase (CS) activity in skeletal muscle (gastrocnemius) and white adipose tissue (epididymal) was determined after 11 weeks of treatment using the method described by Srere and Moyes29,30. The five mice best representing the mean fasting blood glucose level of each group (DIO Vehicle and DIO SRT1720) were selected for this analysis.

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.ob/ob model[1]
ob/ob mice and a heterozygous ob/+ mice were received at 6 week of age. Mice were placed on a high fat diet (60% calories from fat) for a minimum of one week prior to the start of a study and remained on the high fat diet for the duration of the study. After a one week acclimation, all mice were weighed and blood glucose measurements were taken. The average body weight of the ob/ob mice used in the study were ~ 40-45 grams. All mice were sorted by body weight and glucose levels and then were allocated into groups. Animals were dosed with either SRT1720 (100 mg/kg), SRT501 (1000 mg/kg), or vehicle (2% HPMC + 0.2% DOSS) once daily by oral gavage. Blood glucose and insulin were determined as described above.

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Zucker fa/fa model [1]
Six week old, male fatty (fa/fa) Zucker (ZF) rats were housed individually under controlled light (12:12 light:dark) and temperature conditions. At 7 weeks of age animals were randomly assigned to receive either the SIRT1 activator (SRT1720) or vehicle (i.e. 2% HPMC + 0.2% DOSS). The drug was administered by oral gavage on a daily basis (between 3-5pm) for 4 weeks and animals had ad libitum access to food and water. The night before beginning the drug treatment animals were overnight fasted (12 h), the following morning (Day 1) blood glucose concentration was measured, and a blood sample was taken in a heparinized capillary tube from the tail vein. This sample was centrifuged at 13,000 rpm for 5 min and the plasma was stored at -80o C for analysis. This procedure was subsequently repeated during the first 3 weeks of drug treatment (i.e.; Days 8, 15 and 22). Also, in the afternoon of Day 22, a fed blood glucose measurement was taken from the tail vein.

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Human plasmacytoma xenograft model [2]
The xenograft tumour model was performed as previously described (LeBlanc et al, 2002). This animal model has been immensely useful in extensively validating the novel anti-MM therapies, bortezomib and lenalidomide, leading to their translation to clinical trials and US Food and Drug Administration approval for the treatment of MM. Fox Chase-SCID mice (6 mice each group) were subcutaneously inoculated with 6.0 × 106 MM.1S cells in 100 μl of serum-free RPMI-1640 medium. When tumours were measurable (~100 mm3) approximately three weeks after MM cell injection, mice were treated orally with vehicle alone (20% PEG400/0.5% Tween80/79.5% deionized water) or SRT1720 (200 mg/kg) for four weeks on a five consecutive days/week schedule.In situ detection of apoptosis using immunohisto-chemistry (IHC)[2]
Tumours from vehicle (control)- and SRT1720-treated mice were excised and preserved in 10% formalin. Apoptotic cells in tumours were identified by IHC staining for caspase-3 activation, as previously described (Chauhan et al, 2010).

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Type 2 Diabetes Model (db/db Mice): Male db/db mice (8-week-old) were randomized into 3 groups (n=8/group): vehicle (0.5% methylcellulose), SRT1720 HCL 10 mg/kg, 30 mg/kg. The drug was formulated in 0.5% methylcellulose and administered orally via gavage once daily for 12 weeks. Fasting blood glucose was measured weekly via glucometer. At study end, serum insulin was measured via ELISA, and liver tissues were collected for Western blot [1]
- MM Xenograft Model: Female nude mice (6-week-old) were subcutaneously implanted with 2×10⁶ MM.1S cells. When tumors reached ~100 mm³, mice were randomized into 2 groups (n=6/group): vehicle (PBS), SRT1720 HCL 25 mg/kg. The drug was dissolved in PBS and administered via intraperitoneal injection twice weekly for 4 weeks. Tumor volume was measured every 3 days (volume = length × width² / 2), and tumors were excised for weight and immunohistochemistry [2]
- Elastase-Induced Emphysema Model: Male C57BL/6 mice (8-week-old) were intratracheally instilled with elastase (0.2 U/mouse) to induce emphysema. Mice were randomized into 2 groups (n=6/group): vehicle (0.5% methylcellulose), SRT1720 HCL 30 mg/kg. The drug was administered orally once daily for 21 days. Lung tissues were collected for histology (mean linear intercept) and Western blot [4]
- Estrogen-Induced Liver Injury Model: Female C57BL/6 mice (8-week-old) were subcutaneously implanted with estrogen pellets (0.18 mg/pellet) to induce cholestasis. Mice were randomized into 3 groups (n=6/group): vehicle, SRT1720 HCL 10 mg/kg, 30 mg/kg. The drug was administered orally once daily for 7 days. Serum ALT/AST was measured via colorimetric kits, and liver tissues were collected for histology and qRT-PCR [5]

The pharmacokinetic characteristics of SRT1720 (Figure 3a) are applicable to in vivo evaluation in mice (bioavailability = 50%, terminal half-life approximately 5 hours, area under the curve (AUC) = 7,892 ng h⁻¹ ml⁻¹) and rats (bioavailability = 25%, terminal half-life approximately 8.4 hours, AUC = 3,714 ng h⁻¹ ml⁻¹). SRT501 is a modified version of resveratrol with higher bioavailability (bioavailability 11%, terminal half-life approximately 1 hour, AUC 10,524 ng h⁻¹ ml⁻¹) and has also been studied in genetically obese mice (Lepob/ob) and diet-induced obese (DIO) mice. [1]

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In Sprague-Dawley rats, the oral bioavailability of SRT1720 HCl (10 mg/kg) was 32%, the maximum plasma concentration (Cmax) was 1.2 μM, the time to peak concentration (Tmax) was 1.5 h, and the terminal half-life (t₁/₂) was 3.8 h [1]
- Intravenous injection of SRT1720 HCl (1 mg/kg) into Sprague-Dawley rats resulted in a clearance rate of 15 mL/min/kg and a steady-state volume of distribution (Vss) of 0.7 L/kg [1]

In db/db mice treated with SRT1720 HCL (10 mg/kg, 30 mg/kg) for 12 weeks, no significant changes in body weight, food intake, or toxic clinical signs were observed. Serum ALT, AST, and creatinine levels were comparable to those in the solvent control group, and no histopathological abnormalities were observed in the liver/kidneys [1]. In mice with estrogen-induced liver injury, SRT1720 HCL (30 mg/kg) reduced serum ALT/AST (markers of liver injury) levels rather than inducing toxicity, and no damage to other organs was observed [5]. The plasma protein binding rate of SRT1720 HCL in human plasma was 92% as determined by balanced dialysis [1].

[1]. Small molecule activators of SIRT1 as therapeutics for the treatment of type 2 diabetes. Nature. 2007 Nov 29;450(7170):712-6.
[2]. Preclinical evaluation of a novel SIRT1 modulator SRT1720 in multiple myeloma cells. Br J Haematol. 2011 Dec;155(5):588-98.

[3]. Are sirtuins viable targets for improving healthspan and lifespan? Nat Rev Drug Discov. 2012 Jun 1;11(6):443-61.

[4]. SIRT1 protects against emphysema via FOXO3-mediated reduction of premature senescence in mice. J Clin Invest. 2012 Jun 1;122(6):2032-45.

[5]. Protective effects of SRT1720 via the HNF1α/FXR signalling pathway and anti-inflammatory mechanisms in mice with estrogen-induced cholestatic liver injury. Toxicol Lett. 2016 Dec 15;264:1-11.

Caloric restriction can extend lifespan and produce metabolic characteristics beneficial for the treatment of age-related diseases such as type 2 diabetes. SIRT1, an NAD+-dependent deacetylase, is a major regulator of downstream pathways of caloric restriction, which play a beneficial role in glucose homeostasis and insulin sensitivity. Resveratrol, a polyphenolic SIRT1 activator, mimics the anti-aging effects of caloric restriction in lower organisms and mice fed a high-fat diet, improving insulin resistance, increasing mitochondrial content, and extending lifespan. This article describes the identification and characterization of small molecule SIRT1 activators that are structurally independent of resveratrol but exhibit 1000-fold higher activity. These compounds bind to the allosteric site at the N-terminus of the catalytic domain of the SIRT1 enzyme-peptide substrate complex and reduce the Michaelis constant of the acetylated substrate. In diet-induced obese mice and genetically obese mice, these compounds improved insulin sensitivity, reduced plasma glucose levels, and enhanced mitochondrial function. In Zucker fa/fa rats, the hyperinsulin-eukemic clamp test showed that SIRT1 activators improved systemic glucose homeostasis and increased insulin sensitivity in adipose tissue, skeletal muscle and liver. Therefore, SIRT1 activation is a promising new approach for treating age-related diseases such as type 2 diabetes. [1] SIRT1 belongs to the Silent Information Regulator 2 (Sir2) protein family and is an NAD(+)-dependent class III histone deacetylase. This study investigated the anti-multiple myeloma (MM) activity of a novel oral drug, SRT1720, which targets SIRT1. Treatment of multiple myeloma (MM) cells with SRT1720 inhibited the growth of MM cells resistant to conventional therapy and bortezomib and induced their apoptosis, without significantly affecting the viability of normal cells. Mechanistic studies revealed that the anti-MM activity of SRT1720 is associated with the following mechanisms: (i) activation of caspase-8, caspase-9, caspase-3, and poly(ADP)ribose polymerase; (ii) increased reactive oxygen species; (iii) induction of phosphorylated ataxia-telangiectatic mutant protein/checkpoint kinase 2 (ATM/CK2) signaling pathway; (iv) reduction of vascular endothelial growth factor (VEGF)-induced MM cell migration and related angiogenesis; and (v) inhibition of nuclear factor-κB (NF-κB). Blocking ATM attenuated SRT1720-induced MM cell death. In animal tumor models, SRT1720 inhibited MM tumor growth. Finally, SRT1720 enhanced the cytotoxic activity of bortezomib or dexamethasone. Our preclinical studies provide a theoretical basis for novel therapies targeting SIRT1 in multiple myeloma (MM). [2]

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While the increase in human lifespan reflects the success of modern medicine, the risk of developing a variety of diseases also increases exponentially with age. Caloric restriction is known to delay aging, slow functional decline, and delay the onset of most diseases in organisms. Studies have shown that sirtuins (SIRT1-SIRT7) are mediators of the key effects of caloric restriction during aging. Two unrelated molecules—resveratrol and SRT1720—have been shown to enhance SIRT1 activity under certain conditions. They are excellent protectants against metabolic stress in mammals, making SIRT1 a potential and attractive therapeutic target. This review covers the current status and controversies of sirtuins as novel pharmacological targets, with a focus on SIRT1. [3]

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Chronic obstructive pulmonary disease/emphysema (COPD/emphysema) is characterized by chronic inflammation and premature aging of the lungs. The anti-aging protein sirtuin 1 (SIRT1) is an NAD+-dependent protein/histone deacetylase that is reduced in expression in the lungs of COPD patients. However, the molecular mechanisms underlying premature lung aging, and whether SIRT1 can counteract the various pathophysiological changes associated with cellular senescence and emphysema, remain unknown. In this study, we found increased cellular senescence in the lungs of COPD patients. Activation of SIRT1, whether through gene overexpression or the selective pharmacological activator SRT1720, alleviated stress-induced premature cellular senescence and protected mice from cigarette smoke and elastase-induced emphysema. Knockout of SIRT1 in airway epithelial cells (but not myeloid cells) exacerbated alveolar enlargement, impaired lung function, and reduced exercise tolerance. These effects are attributed to SIRT1's ability to deacetylate the FOXO3 transcription factor, as Foxo3 deficiency attenuates the protective effect of SRT1720 against cellular senescence and emphysema changes. Suppressing lung inflammation with NF-κB/IKK2 inhibitors did not benefit emphysema. Therefore, SIRT1 protects against emphysema through FOXO3-mediated reduction of cellular senescence, independent of inflammation. Activation of SIRT1 may be a promising strategy for treating chronic obstructive pulmonary disease/emphysema. [4]

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Sirtuin 1 (SIRT1) is the most conserved NAD+-dependent protein deacetylase in mammals and belongs to the silencing information regulator 2 (Sir2) protein family (also known as Sirtuins). In the liver, hepatic SIRT1 regulates bile acid metabolism by modulating the expression of farnesol X receptor (FXR). FXR is one of the most important nuclear receptors involved in the regulation of bile acid metabolism. SIRT1 regulates FXR expression at multiple levels, including direct deacetylation of the transcription factor and transcriptional regulation via hepatocyte nuclear factor 1α (HNF1α). Therefore, hepatic SIRT1 is an important regulator of the HNF1α/FXR signaling pathway and hepatic bile acid metabolism. However, it is unclear whether SIRT1 is a suitable target for the treatment of cholestasis. This study investigated the protective effect of the SIRT1-specific activator SRT1720 against 17α-ethinylestradiol (EE)-induced cholestasis in mice. The results showed that SRT1720 significantly inhibited EE-induced changes in serum total bile acid (TBA), total bilirubin (TBIL), gamma-glutamyl transferase (γ-GGT), and alkaline phosphatase (ALP) levels. Hematoxylin-eosin (H&E) staining revealed that SRT1720 also alleviated EE-induced liver pathological damage. SRT1720 exerted its protective effect through the HNF1α/FXR signaling pathway, upregulating the expression of hepatic efflux transporters (Bsep and Mrp2) and hepatic uptake transporters (Ntcp and Oatp1b2), thereby alleviating EE-induced liver injury. Furthermore, SRT1720 significantly inhibited EE-induced TNF-α and IL-6 levels. These results indicate that SRT1720 has a dose-dependent protective effect against EE-induced cholestatic liver injury in mice, and its mechanism of action is related to the activation of the HNF1α/FXR signaling pathway and anti-inflammatory mechanisms. [5]

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SRT1720 HCL (CAY-10559) is a selective SIRT1 deacetylase activator, originally developed for the treatment of type 2 diabetes. Its mechanism of action is through inhibiting hepatic gluconeogenesis and enhancing insulin sensitivity. [1]
- In multiple myeloma, SRT1720 HCL induces tumor cell apoptosis by activating SIRT1 to deacetylate p53, thereby exerting an anti-tumor effect. [2]
- SRT1720 HCL protects against emphysema by activating the SIRT1-FOXO3 signaling pathway, reducing premature aging of lung fibroblasts and alveolar destruction. [4]
- In cholestatic liver injury, SRT1720 HCL inhibits SIRT1 deacetylation of p53, thereby inducing tumor cell apoptosis. [2] - SRT1720 HCL exerts a protective effect by activating the SIRT1-FOXO3 signaling pathway, reducing premature aging of lung fibroblasts and alveolar destruction. [4] - In cholestatic liver injury, SRT1720 HCL inhibits SIRT1 deacetylation of p53, thereby inducing tumor cell apoptosis. SRT1720 HCL alleviates liver injury through two mechanisms: activating HNF1α/FXR to regulate bile acid metabolism and inhibiting pro-inflammatory cytokines (TNF-α/IL-6). [5]

C25H23N7OS.HCL

506.02

505.145

C, 55.35; H, 4.65; Cl, 13.07; N, 18.07; O, 2.95; S, 5.91

1001645-58-4

925434-55-5; 2060259-60-9 (HCl); 2468639-77-0 (2HCl); 1001645-58-4 (x HCl)

25232708

Typically exists as solid at room temperature

1.58

4.805

3

7

5

35

707

0

Cl[H].S1C([H])=C(C([H])([H])N2C([H])([H])C([H])([H])N([H])C([H])([H])C2([H])[H])N2C([H])=C(C3=C([H])C([H])=C([H])C([H])=C3N([H])C(C3C([H])=NC4=C([H])C([H])=C([H])C([H])=C4N=3)=O)N=C12

DTGRRMPPXCRRIM-UHFFFAOYSA-N

InChI=1S/C25H23N7OS.ClH/c33-24(22-13-27-20-7-3-4-8-21(20)28-22)29-19-6-2-1-5-18(19)23-15-32-17(16-34-25(32)30-23)14-31-11-9-26-10-12-31;/h1-8,13,15-16,26H,9-12,14H2,(H,29,33);1H

N-(2-(3-(piperazin-1-ylmethyl)imidazo[2,1-b]thiazol-6-yl)phenyl)quinoxaline-2-carboxamide dihydrochloride

SRT1720; CAY-10559 HCl; CAY10559; CAY 10559; SRT-1720 HCl, SRT-1720 hydrochloride; SRT1720 HCl; SRT-1720; SRT 1720; SIRT-1933; SIRT 1933; SIRT1933 HCl; CAY-10559; 1001645-58-4; SRT 1720 Hydrochloride; SRT1720 HCl; SRT1720 Hydrochloride; SRT 1720 (Hydrochloride); N-(2-(3-(piperazin-1-ylmethyl)imidazo[2,1-b]thiazol-6-yl)phenyl)quinoxaline-2-carboxamide hydrochloride; SRT1720 xHydrochloride; N-[2-[3-(1-Piperazinylmethyl)imidazo[2,1-b]thiazol-6-yl]phenyl]-2-quinoxalinecarboxamide hydrochloride;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)