ACY-738 (ACY738) is a novel, potent, selective, brain penetrable and orally-bioavailable HDAC6 inhibitor with neuroprotective and anticancer activities. It also inhibits HDAC1, HDAC2, and HDAC3, with IC50s of 94, 128, and 218 nM; its IC50 for HDAC6 is 1.7 nM. In RN46A-B14 cells, ACY-738 (2.5 μM) raises the acetylated (lysine 40) fraction of α-tubulin. Cell death induced by ACY-738 (10 μM) is similar to that of FK228 and LBH589. ACY-738 has a selectivity of 60–1500 times greater than class I HDACs and low nanomolar potency when inhibiting HDAC6. ACY-738 stimulates mouse exploratory behaviors in unfamiliar but novel environments and causes dramatic increases in α-tubulin acetylation in the brain, unlike tubastatin A, a reference HDAC6 inhibitor with similar potency and peripheral activity but less brain bioavailability.

Physicochemical Properties

Molecular Formula	C14H14N4O2
Molecular Weight	270.29
Exact Mass	270.111
Elemental Analysis	C, 62.21; H, 5.22; N, 20.73; O, 11.84
CAS #	1375465-91-0
Related CAS #	1375465-91-0
PubChem CID	57381425
Appearance	White to off-white solid powder
Density	1.4±0.1 g/cm3
Index of Refraction	1.715
LogP	0.24
Hydrogen Bond Donor Count	3
Hydrogen Bond Acceptor Count	5
Rotatable Bond Count	4
Heavy Atom Count	20
Complexity	345
Defined Atom Stereocenter Count	0
SMILES	O=C(C1=C([H])N=C(N=C1[H])N([H])C1(C2C([H])=C([H])C([H])=C([H])C=2[H])C([H])([H])C1([H])[H])N([H])O[H]
InChi Key	LIIWIMDSZVNYHY-UHFFFAOYSA-N
InChi Code	InChI=1S/C14H14N4O2/c19-12(18-20)10-8-15-13(16-9-10)17-14(6-7-14)11-4-2-1-3-5-11/h1-5,8-9,20H,6-7H2,(H,18,19)(H,15,16,17)
Chemical Name	N-hydroxy-2-[(1-phenylcyclopropyl)amino]pyrimidine-5-carboxamide
Synonyms	ACY738; ACY 738; ACY-738
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	HDAC6 ( IC50 = 1.7 nM ); HDAC1 ( IC50 = 94 nM ); HDAC2 ( IC50 = 128 nM ); HDAC3 ( IC50 = 218 nM )
ln Vitro	ACY-738 (2.5 μM) raises the acetylated (lysine 40) fraction of α-tubulin in RN46A-B14 cells[1]. ACY-738 (10 μM) causes a similar amount of cell death as FK228 and LBH589[3].
ln Vivo	ACY-738 (5 mg/kg) significantly increases α-tubulin acetylation in whole-brain lysates. In WT mice examined in a home cage setting, ACY-738 (50 mg/kg) does not result in an increase in locomotor activity[1]. ACY-738 (5 mg/kg) takes 0.0830 hours to reach its maximum plasma concentration of 1310 ng/mL. IgG and C3 deposition in NZB/W mice are not significantly affected by ACY-738 (5 mg/kg BW), although it does change the differentiation of BM B cells. The severity of proteinuria in NZB/W F1 mice is significantly reduced by ACY-738 (20 mg/kg). With age, NZB/W mice treated with ACY-738 (5 mg/kg) produced significantly less anti-dsDNA. As the NZB/W mice aged, ACY-738 (5, 20 mg/kg) attenuated the production of IL-1β in the sera. While treatment with ACY-738 (20 mg/kg) reduced IL-6 and IL-10 mRNA to non-detectable levels, ACY-738 (5 mg/kg) significantly reduced glomerular IL-6 and IL-10 mRNA levels by more than 50%[2].
Enzyme Assay	ACY-738 is a newly developed HDAC6 inhibitor that is highly selective, potent, and orally bioavailable. Its IC50 is 1.7 nM, and it also inhibits HDAC1, HDAC2, and HDAC3 at IC50s of 94, 128, and 218 nM.
Cell Assay	In RN46A-B14 cells, ACY-738 (2.5 μM) raises the acetylated (lysine 40) fraction of α-tubulin.
Animal Protocol	5, 20, 50 mg/kg; i.p. and p.o. In RN46A-B14 cells, ACY-738 (2.5 μM) raises the acetylated (lysine 40) fraction of α-tubulin.Beginning at 22 weeks of age and continuing until their euthanasia at 38 weeks, mice receive intraperitoneal injections five days a week of either the vehicle control (DMSO), ACY-738 treatment at 5 mg/kg (low-dose), or ACY-738 treatment at 20 mg/kg (high-dose). Eighty μL is the total volume injected. Every two weeks, weight and proteinuria are assessed, and every four weeks, blood is drawn for sera analysis. Siemens Uristix dipsticks are used in a standard semi-quantitative test to measure proteinuria. Dipstick readings of 0 mg/dL = 0, trace = 1, 30-100 mg/dL = 2, 100-300 mg/dL = 3, 300-2000 mg/dL = 4, and 2000 + mg/dL = 5 are the methods used to quantify and score the results[2].
References	[1]. Antidepressant-like properties of novel HDAC6-selective inhibitors with improved brain bioavailability. Neuropsychopharmacology. 2014 Jan;39(2):389-400. [2]. Specific HDAC6 inhibition by ACY-738 reduces SLE pathogenesis in NZB/W mice. Clin Immunol. 2016 Jan;162:58-73. [3]. Histone deacetylase (HDAC) inhibitors as single agents induce multiple myeloma cell death principally through the inhibition of class I HDAC. Br J Haematol. 2013 Aug;162(4):559-62.

Solubility Data

Solubility (In Vitro)

DMSO: ≥ 32 mg/mL Water: <1 mg/mL Ethanol:

Solubility (In Vivo)

Solubility in Formulation 1: ≥ 2.08 mg/mL (7.70 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 20.8 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. Solubility in Formulation 2: ≥ 2.08 mg/mL (7.70 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in 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 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly. 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. Solubility in Formulation 3: ≥ 2.08 mg/mL (7.70 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 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.  (Please use freshly prepared in vivo formulations for optimal results.)

Preparing Stock Solutions		1 mg	5 mg	10 mg
	1 mM	3.6997 mL	18.4986 mL	36.9973 mL
	5 mM	0.7399 mL	3.6997 mL	7.3995 mL
	10 mM	0.3700 mL	1.8499 mL	3.6997 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.