IPA-3 (IPA3; IPA 3) is a novel, potent, selective and non-ATP competitive PAK1 (p21-activated protein kinase 1) inhibitor with potential antitumor activity. It inhibits the growth of liver cancer cells by suppressing PAK1 and NF-κB activation and has IC50 of 2.5 μM, and shows no inhibition to group II PAKs (PAKs 4-6).

Physicochemical Properties

Molecular Formula	C20H14O2S2
Molecular Weight	350.45
Exact Mass	350.043
CAS #	42521-82-4
Related CAS #	42521-82-4
PubChem CID	521106
Appearance	Light yellow to yellow solid powder
Density	1.5±0.1 g/cm3
Boiling Point	543.7±35.0 °C at 760 mmHg
Melting Point	172℃
Flash Point	263.4±24.7 °C
Vapour Pressure	0.0±1.5 mmHg at 25°C
Index of Refraction	1.836
LogP	4.96
Hydrogen Bond Donor Count	2
Hydrogen Bond Acceptor Count	4
Rotatable Bond Count	3
Heavy Atom Count	24
Complexity	380
Defined Atom Stereocenter Count	0
InChi Key	RFAXLXKIAKIUDT-UHFFFAOYSA-N
InChi Code	InChI=1S/C20H14O2S2/c21-17-11-9-13-5-1-3-7-15(13)19(17)23-24-20-16-8-4-2-6-14(16)10-12-18(20)22/h1-12,21-22H
Chemical Name	1,1-disulfanediylbis(naphthalen-2-ol)
Synonyms	IPA-3; IPA 3; IPA3
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

ln Vitro	Part of the mechanism by which IPA-3 suppresses Pak1 activation is covalent attachment to Pak1's regulatory domain. Pak1 is covalently bound by IPA-3 in a temperature- and time-dependent manner. Binding of the Pak1 activator Cdc42 is inhibited by IPA-3. Direct binding of IPA-3 occurs with the Pak1 autoregulatory domain. In cells, IPA-3 reversibly prevents PMA-induced membrane ruffling[1]. Human primary Schwann and schwannoma cells exhibit reduced cell spreading in response to IPA-3 (2 μM, 5 μM, or 20 μM). In a dose-dependent manner, IPA-3 therapy dramatically lowers adherent Schwann and schwannoma cell counts[2]. IPA-3 is an allosteric inhibitor of p21-activated kinase 1 (Pak1) that is non-ATP-competitive. The IPA-3 control chemical is PIR3.5. On Thr423, IPA-3 inhibits the autophosphorylation of Pak1 induced by Cdc42. Additionally, sphingosine-dependent Pak1 autophosphorylation is inhibited by IPA-3. IPA-3 does not specifically target Pak1's exposed cysteine residues. The disulfide bond in IPA-3 is essential for the inhibition of Pak1, and Pak1 inhibition by IPA-3 is eliminated in vitro when the reducing agent dithiothreitol (DTT) is reduced. IPA-3 prevents different activators from activating Pak1, but it has no effect on Pak1 that has already been activated. In mouse embryonic fibroblasts, IPA-3 suppresses the activation of Pak in response to PDGF[3].
ln Vivo
Animal Protocol
References	[1]. An allosteric kinase inhibitor binds the p21-activated kinase autoregulatory domain covalently. Mol Cancer Ther. 2009 Sep;8(9):2559-65. [2]. PAK kinase regulates Rac GTPase and is a potential target in human schwannomas. Exp Neurol. 2009 Jul;218(1):137-44. [3]. An isoform-selective, small-molecule inhibitor targets the autoregulatory mechanism of p21-activated kinase. Chem Biol. 2008 Apr;15(4):322-31.
Additional Infomation	IPA-3 is an organic disulfide obtained by oxidative dimerisation of 1-sulfanylnaphthalen-2-ol. It has a role as an EC 2.7.11.1 (non-specific serine/threonine protein kinase) inhibitor. It is an organic disulfide and a member of naphthols.

Solubility Data

Solubility (In Vitro)

DMSO: 70 mg/mL (199.7 mM) Water:<1 mg/mL Ethanol:7 mg/mL (20.0 mM)

Solubility (In Vivo)

Solubility in Formulation 1: 2.5 mg/mL (7.13 mM) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution; with sonication. 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. Solubility in Formulation 2: 2.5 mg/mL (7.13 mM) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), suspension solution; with ultrasonication. 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 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: ≥ 2.5 mg/mL (7.13 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.  (Please use freshly prepared in vivo formulations for optimal results.)

Preparing Stock Solutions		1 mg	5 mg	10 mg
	1 mM	2.8535 mL	14.2674 mL	28.5347 mL
	5 mM	0.5707 mL	2.8535 mL	5.7069 mL
	10 mM	0.2853 mL	1.4267 mL	2.8535 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.