Mocetinostat (MG0103) is an orally available HDAC inhibitor with most potency for HDAC1 (IC50: 0.15 μM), 2- to 10- fold selectivity against HDAC2/3/11.

HDAC2:0.29 μM(cell free), HDAC11:0.59 μM(cell free), HDAC1:0.15 μM(cell free), HDAC3:1.66 μM(cell free)

Mocetinostat (MGCD0103) 在体外有效针对人类HDAC1并对HDAC2、HDAC3和HDAC11也有抑制作用。在完整细胞中，MGCD0103仅抑制了总HDAC活性的一部分，并且即使在药物移除后也显示出持久的抑制活性。MGCD0103诱导组蛋白过度乙酰化，选择性诱导凋亡，并且在多种人类癌症细胞系中以剂量依赖的方式导致细胞周期阻滞[1]。MGCD0103在体外的多种人类癌症细胞系中以及体外的人类外周白细胞(WBC)中剂量依赖性地抑制HDAC活性。MGCD0103的HDAC抑制活性是时间依赖的，在外周WBC中至少持续24小时[2]。

在体内，Mocetinostat显著以剂量依赖的方式抑制裸鼠体内人类肿瘤异种移植物的生长，其抗肿瘤活性与肿瘤中组蛋白乙酰化的诱导相关[1]。Mocetinostat的抑制活性在裸鼠体内至少持续8小时，在固体肿瘤患者中持续48小时。在癌症患者中，Mocetinostat持续的药效仅通过外周WBC中剂量依赖的酶抑制得以观察到，而非通过组蛋白乙酰化分析[2]。以高剂量通过胃内给药7天的MGCD0103，轻微诱导大鼠的托布他胺代谢。Mocetinostat未能诱导或抑制CYP1A2、CYP2B1、CYP2D4和CYP3A2酶的活性[3]。MGCD0103改善了肺动脉加速时间，并减少了肺动脉流动轮廓的收缩期凹陷[4]。

The deacetylase enzyme assay was based on a homogeneous fluorescence release assay. Purified recombinant HDAC enzymes were incubated with compounds diluted in various concentrations for 10 min in assay buffer [25 mmol/L HEPES (pH 8.0), 137 mmol/L NaCl, 1 mmol/L MgCl2, 2.7 mmol/L KCl] at room temperature. The substrate Boc-Lys(ε-Ac)-AMC was added to the reaction for further incubation at 37°C. The concentration of the substrate and the incubation time varied for different isotypes of HDAC enzymes. A 20-min trypsin incubation at room temperature allowed the release of the fluorophore from the deacetylated substrate. The fluorescent signal was detected by fluorometer at excitation of 360 nm, emission of 470 nm, and cutoff at 435 nm. The IC50 values of the compounds were determined by analyzing dose-response inhibition curves [1].

Cells were transfected with antisense oligonucleotides for 4 h everyday for 2 d. At 48 h after initial transfection, cells were harvested and apoptosis was evaluated with the Cell Death Detection ELISA Plus kit following the manufacturer's protocol. In all experiments, a fixed amount of DNA-histone complex, provided with the ELISA kit as a positive control, was used to ensure results were comparable among experiments. To analyze caspase-dependent apoptosis, an antibody specifically recognizing the caspase cleavage fragment of human poly(ADP-ribose) polymerase (PARP) was used to probe Western blots of lysates from cells treated with MGCD0103 [1].

Female CD-1 nude mice, ages 8 to 10 wk, were used. Tumor fragments (～30 mg), which had been serially passaged thrice in vivo in minimal, were implanted s.c. through a small surgical incision on the flank of the mice while under general anesthesia. HDAC inhibitors were dissolved in vehicle (PBS acidified with 0.1 N HCl or PEG400/0.2 N HCl saline, 40:60) and dosed p.o. as solutions daily. Tumor volumes and body weight were monitored thrice weekly for at least 2 wk. Each experimental group contained six to eight animals. For pharmacokinetic study, blood was collected from animals at various time points, and plasma samples were analyzed using an HPLC system coupled with a triple quadrupole mass spectrometer [1]. . Forty rats (220 ± 20?g) were randomly divided into four different dosages of MGCD0103 groups (Low group, Medium group, High group, and control group with 10 rats in each group). MGCD0103 was dissolved in corn oil as suspension at three different concentrations (20, 40, and 80?mg/mL). Three different MGCD0103 groups (Low group, Medium group, and High group) were respectively given MGCD0103 20, 40, and 80?mg/kg one time by intragastric administration at every morning and last for 7 days. Control group were given saline by same administration method. At 8 days morning, six probe drugs, bupropion, phenacetin, tolbutamide, metoprolol, testosterone, and omeprazole, were mixed in corn oil and given to the rats of three MGCD0103 groups and control group by intragastric administration at a single dosage of 10?mg/kg for bupropion, phenacetin, metoprolol, testosterone, and omeprazole and 1?mg/kg for tolbutamide. Blood (0.3?mL) samples were collected into heparinized 1.5?mL polythene tubes from the tail vein at 0.0833, 0.5, 1, 2, 3, 4, 6, 8, 12, 24, and 48?h after intragastric administration of six probe drugs. 100?μL of plasma was obtained from blood sample after centrifugation at 4000?g for 10?min. In a 1.5?mL centrifuge tube, 200?μL of acetonitrile (containing 50?ng/mL IS) was added into 100?μL of collected plasma sample. After vortex-mixing for 1.0?min, the sample was centrifuged at 13000?g for 15?min. Then supernatant (2?μL) was injected into the UPLC-MS/MS system for analysis. Concentration of plasma probe drugs versus time was analyzed by Version 3.0 Data Analysis System. The main pharmacokinetic parameters of the MGCD0103 group and control group were analyzed by SPSS l8.0 statistical software [3].