HDAC-IN-73 (compound P-503) is a histone deacetylase (HDAC) inhibitor. The IC50s of HDAC-IN-73 for HDAC1 and HDAC6 are 0.17 and 0.49 µM, respectively. Notably, HDAC-IN-73 has enhanced inhibitory potency against HDAC6, and its efficacy is 9 times that of PsA (IC50=3.9 µM). HDAC-IN-73 has potent antiproliferative activity, induces apoptosis, and causes cell arrest in the G2/M phase. HDAC-IN-73 has the potential to be used in cancer research such as colon cancer [1].

Physicochemical Properties

Molecular Formula	C22H24BR2N4O6SE2
Molecular Weight	758.18
CAS #	2323571-16-8
Appearance	Typically exists as solid at room temperature
HS Tariff Code	2934.99.9001
Storage	Powder-20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month
Shipping Condition	Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Biological Activity

Targets	HDAC1 0.17 μM (IC50) HDAC6 0.49 μM (IC50)
ln Vitro	HDAC-IN-73 (compound P-503) (0-10 µM; 48 h) inhibits the proliferation of HCT116 cells with an IC50 value of 0.24 µM, while the IC50 value of PsA is 3.05 µM[1]. Compared with PsA, HDAC-IN-73 (0.25-2 µM; 24 h) can increase the acetylation level of histone H3 or α-tubulin in HCT116 cells[1]. HDAC-IN-73 (0.1-0.2 µM; 24 h) can induce apoptosis of HCT116 cells and has a pro-apoptotic effect superior to that of PsA[1]. HDAC-IN-73 (0.2-0.4 µM; 48 h) can induce HCT116 cell cycle arrest at the G2/M phase, while PsA increases the proportion of the G1 phase[1]. Apoptosis Analysis[1] Cell Line: HCT116 cells Concentration: 0.2, 0.4 µM Incubation Time: 48 hours Result: Induced apoptosis with 71.94 % of apoptotic cells (both early and late apoptotic cells) at define concentration of 0.4 μM, compared with PsA (56.5 %, 4 μM) . Cell Cycle Analysis[1] Cell Line: HCT116 cells Con centration: 0.1, 0.2 µM Incubation Time: 24 hours Result: Induced cell cycle arrest at G2 / M phase while PsA increased proportion of G1 phase. HDAC-IN-73 with 0.1 μM and 0.2 μM can lead to 47.92 % and 74.56 % of the cells in G2 / M phase, respectively.
ln Vivo	HDAC-IN-73 (compound P-503) (5 mg/kg; ip; every 2 days for 26 days) had significant antitumor activity at 5 mg/kg in the HCT116 xenograft model, but also Higher toxicity, safety and toxic doses of HDAC-IN-73 require further study [1].
Cell Assay	Western Blot Analysis[1] Cell Types: HCT116 Tested Concentrations: 0.25, 0.5, 1, 2 µM Incubation Duration: 24 hours Experimental Results: Increased the acetylation levels of histone H3 or α-tubulin in a dose dependent manner comparing with PsA.
Animal Protocol	Animal/Disease Models:6 weeks, Female nude mice (BALB/c-nu) (HCT116 xenograft model)[1] Doses: 5 mg/kg Route of Administration: I.p.; every 2 days for 26 days Experimental Results: Reduced the tumor volume (p < 0.0001) and the tumor weight (p < 0.01). Exhibited the significant loss of body weight which has the same trend with the group of negative control. Inhibited the tumor growth (TGI = 74.6 %) , while the TGI of SAHA (10 mg/kg, positive control) and PsA (10 mg/kg) were 13.1 % and 36.1 %, respectively. Existed high toxicity, 2 mice died during the medication. Western blot tests showed that the acetylation levels of histone H3 or α-tubulin in tumor tissues were up-regulated.
References	[1]. Psammaplin A analogues with modified disulfide bond targeting histone deacetylases: Synthesis and biological evaluation. Eur J Med Chem. 2024 May 31;275:116541.

Solubility Data

Solubility (In Vitro)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Solubility (In Vivo)

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples. Injection Formulations (e.g. IP/IV/IM/SC) Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline) *Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution. Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline) Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil) Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals). Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)] *Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution. Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline) Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline) Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline) Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil) Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline) Oral Formulations Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium) Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals). Oral Formulation 3: Dissolved in PEG400 Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose Oral Formulation 6: Mixing with food powders Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.  (Please use freshly prepared in vivo formulations for optimal results.)

Preparing Stock Solutions		1 mg	5 mg	10 mg
	1 mM	1.3189 mL	6.5947 mL	13.1895 mL
	5 mM	0.2638 mL	1.3189 mL	2.6379 mL
	10 mM	0.1319 mL	0.6595 mL	1.3189 mL

*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.