HDAC1 ( IC50 = 48 nM ); HDAC4 ( IC50 = 32 nM ); HDAC6 ( IC50 = 41 nM ); HIV-1
PTACH (compound 51) treatment increases p21^WAF1/CIP1 and acetylated histone H4 levels in a dose-dependent manner[1].
PTACH (compound 51) exhibits robust activity in the assay for inhibiting the growth of cancer cells. At EC50 values of 2.3 μM, 9.1 μM, 3.0 μM, 2.6 μM, 1.1 μM, 4.5 μM, 2.4 μM, 5.0 μM, and 4.5 μM for MDA-MB-231, SNB-78, HCT116, NCI-H226, LOX-IMVI, SK-OV-3, RXF-631L, St-4, and DU-145 cells, respectively, PTACH inhibits a variety of cancer cells[1].
PTACH (NCH-51) increases the production of HIV-1 in latently infected OM10.1 cells. This reactivation is linked to a loss of HDAC1 occupancy and subsequent hyperacetylation of histones in nuc-1 at the HIV-1 promoter[2].

PTACH (compound 51) treatment increases p21^WAF1/CIP1 and acetylated histone H4 levels in a dose-dependent manner[1].
PTACH (compound 51) exhibits robust activity in the assay for inhibiting the growth of cancer cells. At EC50 values of 2.3 μM, 9.1 μM, 3.0 μM, 2.6 μM, 1.1 μM, 4.5 μM, 2.4 μM, 5.0 μM, and 4.5 μM for MDA-MB-231, SNB-78, HCT116, NCI-H226, LOX-IMVI, SK-OV-3, RXF-631L, St-4, and DU-145 cells, respectively, PTACH inhibits a variety of cancer cells[1].
PTACH (NCH-51) increases the production of HIV-1 in latently infected OM10.1 cells. This reactivation is linked to a loss of HDAC1 occupancy and subsequent hyperacetylation of histones in nuc-1 at the HIV-1 promoter[2].

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Treatment of latently HIV-1 infected OM10.1 cells (a myelomonocytic leukemic cell line) with NCH-51 alone induced the production of HIV-1 p24 antigen in a dose-dependent manner (0-1.6 μM tested). This effect was further augmented when combined with TNF-α (1 ng/ml). [1]
Similar upregulation of virus production was observed in chronically HIV-1 infected ACH-2 T cells treated with NCH-51. [1]
Western blot analysis of whole cell lysates from OM10.1 cells showed that treatment with NCH-51 (0-1.6 μM for 24 h) increased the acetylation of histone H3 at lysine 9 or 14 in a dose-dependent manner. [1]
Chromatin immunoprecipitation (ChIP) assay in OM10.1 cells treated with 1.6 μM NCH-51 demonstrated hyperacetylation of histone H3 at the nuc-1 region of the HIV-1 long terminal repeat (LTR), concurrent with a reduction in HDAC1 occupancy at the promoter. The assay also showed enrichment of positive transcription factors (RNA polymerase II, TBP) and loss of the negative regulator AP-4 at the HIV-1 LTR. [1]
Treatment of OM10.1 cells with the topoisomerase II inhibitor novobiocin (100 and 200 μg/ml) inhibited the NCH-51-mediated induction of HIV-1 p24 production, suggesting the reactivation involves changes in chromatin structure. [1]
Transient transfection of wild-type and truncated/mutant HIV-1 LTR-driven luciferase reporter plasmids in 293 and Jurkat T cells showed that NCH-51 (1.6 μM) activated transcription. Mutation of all three Sp1 binding sites, but not mutation of NF-κB sites, severely attenuated this activation, indicating Sp1 sites are crucial for NCH-51's effect. [1]
Knockdown of Sp1 using siRNA in TZM-bl cells (containing a stably integrated HIV-1 LTR) significantly suppressed the NCH-51-induced increase in LTR-driven luciferase activity. [1]
Pretreatment of OM10.1 cells with the Sp1 inhibitor mithramycin A (50-100 nM) inhibited the NCH-51-induced HIV-1 p24 expression in a dose-dependent manner. [1]

Cell Line: HCT 116 cells
Concentration: 1 μM, 5 μM, 25 μM
Incubation Time: 8 hours
Result: Gave rise to elevated and dose-dependent levels of acetylated histone H4 and p21^WAF1/CIP1.

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For the viral replication assay, latently infected OM10.1 cells were treated with or without NCH-51 for 4 hours and then stimulated with or without TNF-α (1 ng/ml) for 24 hours at 37°C. The culture supernatants were collected and assayed for HIV-1 p24 antigen using a commercial ELISA kit. Cytotoxicity of the compounds was measured in parallel using the WST-1 method, and the CC50 was defined as the concentration reducing cell viability by 50%. [1]
For chromatin immunoprecipitation (ChIP) assay, OM10.1 cells were cross-linked with formaldehyde, lysed, and the chromatin was sheared by sonication. Sheared chromatin was pre-cleared and then immunoprecipitated overnight at 4°C with specific antibodies (e.g., anti-HDAC1, anti-acetyl-H3, anti-RNA Pol II). Immune complexes were collected using magnetic beads, washed, eluted, and reverse cross-linked. DNA was purified and analyzed by PCR using primers spanning the nuc-1 region (-109 to +79) of the HIV-1 LTR. Input DNA (10% of total chromatin) served as a control. [1]
For transfection and luciferase assays, 293 cells or Jurkat T cells were transfected with HIV-1 LTR-luciferase reporter plasmids using transfection reagents. After 24 hours, cells were treated with NCH-51 (1.6 μM) or TNF-α (5 ng/ml) as a positive control for an additional 12 or 24 hours. Cells were then harvested, lysed, and luciferase activity was measured using a luciferase assay system and normalized to protein concentration. [1]
For siRNA knockdown, TZM-bl cells were cultured in plates and transfected with 50 nM Sp1 siRNA or control siRNA using a lipofectamine reagent according to the manufacturer's instructions and incubated for 48 hours. Knockdown efficiency was confirmed by Western blotting with anti-Sp1 antibody. The transfected cells were then harvested for luciferase assay. [1]

The article mentions that NCH-51 was designed based on the structure of SAHA (octanoylaniline hydroxamic acid), and that by replacing the hydroxamic acid group with an acylated thiol group, better pharmacokinetic properties and lower toxicity were obtained, and cites previous reports (reference 24). [1]

After incubation for 48 hours in OM10.1 and ACH-2 cells, the cytotoxicity of NCH-51 was assessed using the WST-1 assay. The CC50 (50% cytotoxic concentration) of OM10.1 cells was estimated to be approximately 2.2 μM, and the CC50 of ACH-2 cells was estimated to be approximately 2.4 μM. [1]

[1]. Novel inhibitors of human histone deacetylases: design, synthesis, enzyme inhibition, and cancer cell growth inhibition of SAHA-based non-hydroxamates. J Med Chem. 2005 Feb 24;48(4):1019-1032.

[2]. Novel histone deacetylase inhibitor NCH-51 activates latent HIV-1 gene expression. FEBS Lett. 2011 Apr 6;585(7):1103-11.

2-Methylpropionate S-[7-oxo-7-[(4-phenyl-2-thiazolyl)amino]heptyl] ester is an aromatic amide.

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NCH-51 is a novel histone deacetylase inhibitor (HDACi). [1]
It is designed based on the structure of the FDA-approved HDACi SAHA (vorinostat), replacing the hydroxamic acid group with an acylated thiol group in order to improve pharmacokinetics and reduce toxicity. [1]
Studies have shown that NCH-51 can activate latent HIV-1 proviruses in latent cell line models (OM10.1, ACH-2). Its mechanism involves the inhibition of HDACs, leading to histone hyperacetylation, detachment of HDAC1 and the repressor AP-4 from the HIV-1 LTR, recruitment of positive transcription factors (RNA polymerase II, TBP), and subsequent activation of transcription. This transcriptional activation is highly dependent on the Sp1 binding site within the HIV-1 LTR promoter. [1]
The combined use of NCH-51 and TNF-α can effectively activate HIV, suggesting its potential as a combination therapy against latent HIV infection. However, the study also points out that this type of approach needs careful evaluation. [1]

C20H26N2O2S2

390.56264257431

390.143

C, 61.51; H, 6.71; N, 7.17; O, 8.19; S, 16.42

848354-66-5

11395181

White to off-white solid powder

1.2±0.1 g/cm3

1.588

5.49

1

5

11

26

440

0

O=C(C(C)C)SCCCCCCC(NC1SC=C(C2C=CC=CC=2)N=1)=O

MDYDGUOQFUQOGE-UHFFFAOYSA-N

InChI=1S/C20H26N2O2S2/c1-15(2)19(24)25-13-9-4-3-8-12-18(23)22-20-21-17(14-26-20)16-10-6-5-7-11-16/h5-7,10-11,14-15H,3-4,8-9,12-13H2,1-2H3,(H,21,22,23)

S-[7-oxo-7-[(4-phenyl-1,3-thiazol-2-yl)amino]heptyl] 2-methylpropanethioate

NCH-51; NCH 51; NCH51. PTACH

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)

DMSO: ~50 mg/mL (~128.0 mM）

Solubility in Formulation 1: ≥ 2.5 mg/mL (6.40 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (6.40 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)