Tamatinib (formerly known as R406) is a novel potent and ATP competitive Syk inhibitor with potential to treat immune disorders and inflammatory conditions. It inhibits Syk with an IC50 of 41 nM in cell-free assays, and strongly inhibits Syk but not Lyn, shows 5-fold less potency against Flt3. Tamatinib exhibited high efficacy in a number of animal models of immune disorders such as anticollagen antibody-induced arthritis.

Physicochemical Properties

Molecular Formula	C22H23FN6O5
Molecular Weight	470.45
Exact Mass	470.171
Elemental Analysis	C, 56.17; H, 4.93; F, 4.04; N, 17.86; O, 17.00
CAS #	841290-80-0
Related CAS #	R406;841290-81-1
PubChem CID	11213558
Appearance	White to light yellow solid powder
Density	1.4±0.1 g/cm3
Index of Refraction	1.618
LogP	4.32
Hydrogen Bond Donor Count	3
Hydrogen Bond Acceptor Count	11
Rotatable Bond Count	7
Heavy Atom Count	34
Complexity	691
Defined Atom Stereocenter Count	0
InChi Key	NHHQJBCNYHBUSI-UHFFFAOYSA-N
InChi Code	InChI=1S/C22H23FN6O5/c1-22(2)20(30)28-19-13(34-22)6-7-16(27-19)26-18-12(23)10-24-21(29-18)25-11-8-14(31-3)17(33-5)15(9-11)32-4/h6-10H,1-5H3,(H3,24,25,26,27,28,29,30)
Chemical Name	6-((5-fluoro-2-((3,4,5-trimethoxyphenyl)amino)pyrimidin-4-yl)amino)-2,2-dimethyl-2H-pyrido[3,2-b][1,4]oxazin-3(4H)-one
Synonyms	R406 besylate; R406 benzenesulfonate; 841290-80-0; tamatinib; R-406; R406 (free base); R406 free base; 6-(5-fluoro-2-(3,4,5-trimethoxyphenylamino)pyrimidin-4-ylamino)-2,2-dimethyl-2H-pyrido[3,2-b][1,4]oxazin-3(4H)-one; Tamatinib free base; 6-[[5-fluoro-2-(3,4,5-trimethoxyanilino)pyrimidin-4-yl]amino]-2,2-dimethyl-4H-pyrido[3,2-b][1,4]oxazin-3-one; Tamatinib; R 406, R406, R-406;
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	Syk (Ki = 30 nM); Syk (IC50 = 41 nM); Lyn (IC50 = 63 nM); Lck (IC50 = 37 nM); FLT3
ln Vitro	Adenosine transporter (IC50=1.84 µM), monoamine transporter (IC50=2.74 µM), and adenosine A3 receptor (IC50=0.081 µM) are all inhibited by R406[1]. Huh7 hepatocyte, A549 epithelial, and H1299 lung cancer lines are all inhibited by R406, with corresponding EC50s of 15.1, 2.9, and 6.3 µM[1]. R406 prevents mast cell phosphorylation of the Syk substrate LAT and B cell phosphorylation of BLNK/SLP65[1].
ln Vivo	R406 (5 and 10 mg/kg) is effective in lowering clinical symptoms and improving the Arthus reaction in the K/BxN and collagen antibody-induced arthritis (CAIA) models of rheumatoid arthritis (RA). R406 inhibits Fc receptor signaling, which reduces immune complex (IC)-mediated inflammation[1].
Enzyme Assay	R406 is serially diluted in DMSO, diluted in kinase buffer (20 mM HEPES, pH 7.4, 5 mM MgCl2, 2 mM MnCl2, 1 mM DTT, 0.1 mg/mL acetylated BGG) and finally diluted to 1% DMSO by volume. After adding ATP and substrate to kinase buffer at room temperature, the final DMSO concentration is 0.2%. 0.125 ng of Syk is added to kinase buffer to initiate the kinase reactions, which are carried out in a final volume of 20 mL with 5 mM HS1 peptide substrate and 4 mM ATP. The reaction is left to continue at room temperature for forty minutes. 20 mL of PTK quench mix containing EDTA, anti-phosphotyrosine antibody (1X final), and fluorescent phosphopeptide tracer (0.5X final) diluted in FP Dilution Buffer is added to stop the reaction. A Polarion fluorescence polarization plate reader is used to read the plate after it has been incubated for 30 minutes at room temperature in the dark. Through competition with the phosphopeptide competitor included in the Tyrosine Kinase Assay Kit, a calibration curve is created that is used to convert data into the amount of phosphopeptide present. Non-linear regression analysis is used to fit the curve and test R406 at eleven different concentrations in order to determine the IC50.
Cell Assay	Western Blot Analysis[1] Cell Types: Cultured human mast cells (CHMC) Tested Concentrations: 0.016, 0.08, 0.4, 2 µM Incubation Duration: 40 minutes Experimental Results: Inhibited all other kinases tested at 5 to 100 fold less potency than Syk as judged by phosphorylation of target proteins.
Animal Protocol	Animal/Disease Models: Female balb/c (Bagg ALBino) mouse (6-8 weeks) with CAIA[1] Doses: 5 and 10 mg/kg Route of Administration: Administered orally, bid , for 14 days, starting 4 hrs (hours) after antibody challenge on day 0. Experimental Results: decreased inflammation and swelling, and the arthritis progressed more slowly in animals treated than in vehicle controls. Animal/Disease Models: Female C57BL/6 mice with arthritis[1] Doses: 10 mg/kg Route of Administration: Administered orally one hour before serum injection; bid; for 13 days Experimental Results: Delayed the onset and decreased the severity of clinical arthritis. Paw thickening and clinical arthritis were decreased by approximately 50%.
References	[1]. R406, an orally available spleen tyrosine kinase inhibitor blocks fc receptor signaling and reduces immune complex-mediated inflammation. J Pharmacol Exp Ther. 2006 Dec;319(3):998-1008. [2]. A novel spleen tyrosine kinase inhibitor blocks c-Jun N-terminal kinase-mediated gene expression in synoviocytes. J Pharmacol Exp Ther. 2006 May;317(2):571-8.
Additional Infomation	6-[[5-fluoro-2-(3,4,5-trimethoxyanilino)-4-pyrimidinyl]amino]-2,2-dimethyl-4H-pyrido[3,2-b][1,4]oxazin-3-one is a member of methoxybenzenes and a substituted aniline. Recent compelling evidence has lead to renewed interest in the role of antibodies and immune complexes in the pathogenesis of several autoimmune disorders, such as rheumatoid arthritis. These immune complexes, consisting of autoantibodies to self-antigens, can mediate inflammatory responses largely through binding and activating the immunoglobulin Fc receptors (FcRs). Using cell-based structure activity relationships with cultured human mast cells, we have identified the small molecule R406 [N4-(2,2-dimethyl-3-oxo-4H-pyrid[1,4]oxazin-6-yl)-5-fluoro-N2-(3,4,5-trimethoxyphenyl)-2,4-pyrimidinediamine] as a potent inhibitor of immunoglobulin E (IgE)- and IgG-mediated activation of Fc receptor signaling (EC(50) for degranulation = 56-64 nM). Here we show that the primary target for R406 is the spleen tyrosine kinase (Syk), which plays a key role in the signaling of activating Fc receptors and the B-cell receptor (BCR). R406 inhibited phosphorylation of Syk substrate linker for activation of T cells in mast cells and B-cell linker protein/SLP65 in B cells. R406 bound to the ATP binding pocket of Syk and inhibited its kinase activity as an ATP-competitive inhibitor (K(i) = 30 nM). Furthermore, R406 blocked Syk-dependent FcR-mediated activation of monocytes/macrophages and neutrophils and BCR-mediated activation of B lymphocytes. R406 was selective as assessed using a large panel of Syk-independent cell-based assays representing both specific and general signaling pathways. Consistent with Syk inhibition, oral administration of R406 to mice reduced immune complex-mediated inflammation in a reverse-passive Arthus reaction and two antibody-induced arthritis models. Finally, we report a first-inhuman study showing that R406 is orally bioavailable, achieving exposures capable of inhibiting Syk-dependent IgE-mediated basophil activation. Collectively, the results show R406 potential for modulating Syk activity in human disease.[1] Spleen tyrosine kinase (Syk) is a key regulator of cell signaling induced by cytokines or Fc receptor engagement. However, the role of Syk in rheumatoid arthritis (RA) is not known yet. We investigated the pathways activated by Syk in tumor necrosis factor-alpha (TNFalpha)-stimulated fibroblast-like synoviocytes (FLS) using the novel Syk inhibitor N4-(2,2-dimethyl-3-oxo-4H-pyrid[1,4]oxazin-6-yl)-5-fluoro-N2-(3,4,5-trimethoxyphenyl)-2,4-pyrimidinediamine (R406). Using immunohistochemistry, Syk was detected in RA synovial tissue (ST), primarily in the synovial intimal lining. Western blot analysis demonstrated significantly greater amounts of phospho-Syk expression in RA ST compared with osteoarthritis ST. The kinase was expressed and functionally activated by TNFalpha in FLS and was blocked by R406. Western blot analysis demonstrated that Syk inhibition by R406 markedly suppressed TNFalpha-induced c-Jun N-terminal kinase (JNK) phosphorylation in FLS, with a modest decrease in extracellular signal-regulated kinase phosphorylation. Surprisingly, p38 activation was not affected by R406. The Syk inhibitor also decreased TNFalpha-induced mitogen-activated protein kinase kinase (MKK) 4 phosphorylation but not MKK3 and MKK6 phosphorylation, which is consistent with its selective sparing of p38. The connection between Syk and JNK was confirmed by demonstrating decreased phospho-c-Jun protein expression and complete inhibition of JNK function in R406-treated cells. R406 also suppressed downstream actions of JNK, as determined by activator protein 1 binding, as well as matrix metalloproteinase 3 gene expression. These data demonstrate that Syk activation plays an essential role in TNFalpha-induced cytokine and matrix metalloproteinase production in RA FLS, especially by suppressing activation of the JNK pathway.[2]

Solubility Data

Solubility (In Vitro)

DMSO: 21 mg/mL (44.6 mM) Water:<1 mg/mL Ethanol:<1 mg/mL

Solubility (In Vivo)

Solubility in Formulation 1: 2.5 mg/mL (5.31 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), suspension 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 (5.31 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. Solubility in Formulation 3: 1% DMSO+30% polyethylene glycol+1% Tween 80:30mg/mL  (Please use freshly prepared in vivo formulations for optimal results.)

Preparing Stock Solutions		1 mg	5 mg	10 mg
	1 mM	2.1256 mL	10.6281 mL	21.2562 mL
	5 mM	0.4251 mL	2.1256 mL	4.2512 mL
	10 mM	0.2126 mL	1.0628 mL	2.1256 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.