R788 (Fostamatinib) Disodium

Catalog No.S2206

R788 (Fostamatinib) disodium, a prodrug of the active metabolite R406, is a Syk inhibitor with IC50 of 41 nM in a cell-free assay, strongly inhibits Syk but not Lyn, 5-fold less potent to Flt3. Phase 3.

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R788 (Fostamatinib) Disodium Chemical Structure

R788 (Fostamatinib) Disodium Chemical Structure
Molecular Weight: 624.42

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Related Compound Libraries

R788 (Fostamatinib) Disodium is available in the following compound libraries:

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  • Research Area
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    Combination Therapy

Product Description

Biological Activity

Description R788 (Fostamatinib) disodium, a prodrug of the active metabolite R406, is a Syk inhibitor with IC50 of 41 nM in a cell-free assay, strongly inhibits Syk but not Lyn, 5-fold less potent to Flt3. Phase 3.
Targets Syk [1]
(Cell-free assay)
IC50 41 nM
In vitro R935788 is a methylene phosphate prodrug of R406, which can be rapidly converted to R406 in vivo. R406 (in vitro active form of R935788) selectively inhibits Syk-dependent signaling with EC50 values ranging from 33 nM to 171 nM, more potently than Syk-independent pathways in different cells. [1] R406 inhibits cellular proliferation of a variety of diffuse large B-cell lymphoma (DLBCL) cell lines with EC50 values ranging from 0.8 μM to 8.1 μM. [2] R406 treatment reduces basal phosphorylation of BLNK, Akt, glycogen synthase kinase-3 (GSK-3), forkhead box O (FOXO) and ERK not only in cells with high (TCL-002) but also in cells with low levels of phosphorylated Syk (TCL1-551). In addition, R406 completely inhibits the anti-IgM induced Bcr signal in TCL1 leukemias. Despite the higher levels of constitutively active Syk in TCL1 leukemias, R406 is not selectively cytotoxic to the leukemic cells. [3]
In vivo Given that plasma half-life of R406 in mice is less than 2 hours, R935788 is administered in 3 divided doses at 3-hour intervals to provide continuous Syk inhibition during each day of treatment, mimicking the longer plasma half-life in humans (15 hours). Despite the relatively modest cytotoxic effect in vitro, R935788 significantly inhibits the proliferation and survival of leukemic cell in vivo, which is associated with the blocking of antigen-dependent B-cell receptor (Bcr) signaling rather than inhibition of constitutive Syk activity. R935788 treatment at 80 mg/kg/day for 18-21 days potently inhibits tumor growth of TCL1-002, TCL1-551 and TCL1-870 in mice with undetectable leukemic CD5+/B220+ cells at the last day of treatment, significantly prolongs the survival of the treated mice with median survival increased from 45/46 days to 170/172 days, and completely eradicates the malignant cells in a substantial proportion of mice after a 6-month follow-up period without affecting the production of normal B lymphocytes. R935788 treatment also induces an early and transient migration of both normal and malignant B cells from spleen and lymph nodes to peripheral blood, which is subsequently followed by selective growth inhibition of the malignant B-cell population. In addition, R935788 is also effective against spontaneously developing TCL1 leukemias in Eμ-TCL1 transgenic mice. [3]
Features Clinically used oral formulation of R406.

Protocol(Only for Reference)

Kinase Assay:


In vitro fluorescence polarization kinase assays R406 (in vitro active form of R935788) is serially diluted in DMSO and then diluted to 1% DMSO in kinase buffer (20 mM HEPES, pH 7.4, 5 mM MgCl2, 2 mM MnCl2, 1 mM DTT, 0.1 mg/mL acetylated BGG). ATP and substrate in kinase buffer are added at room temperature, resulting in a final DMSO concentration on 0.2%. The kinase reactions are performed in a final volume of 20 μL containing 5 μM HS1 peptide substrate and 4 μM ATP and started by addition of 0.125 ng of Syk in kinase buffer. The reaction is allowed to proceed for 40 minutes at room temperature. The reaction is stopped by the addition of 20 μL of PTK quench mix containing EDTA/anti-phosphotyrosine antibody (1× final)/fluorescent phosphopeptide tracer (0.5× final) diluted in FP Dilution Buffer. The plate is incubated for 30 minutes in the dark at room temperature and then read on a Polarion fluorescence polarization plate reader. Data is converted to determine the amount of phosphopeptide present using a calibration curve generated by competition with the phosphopeptide competitor provided in the Tyrosine Kinase Assay Kit. For IC50 determination, R406 is tested at eleven concentrations in duplicate and curve-fitting is performed by non-linear regression analysis using Prism GraphPad Software.

Cell Assay:


Cell lines TCL1-002, TCL1-252, TCL1-551, TCL1-870, and TCL1-540
Concentrations Dissolved in DMSO, final concentrations ~10 μM
Incubation Time 48 hours

Cells are exposed to increasing concentrations of R406 (in vitro active form of R935788) for 48 hours. The percentage of apoptotic cells is determined by double staining with propidium iodide (PI) and annexin-A5–FITC conjugate. Ki-67 staining is performed with the FITC mouse anti–Ki-67 set. Samples are analyzed on a FACSCalibur flow cytometer with CellQuest Version 3.3 software.

Animal Study:


Animal Models B6/C3H F1 female mice intraperitoneally injected with TCL1-002, TCL1-551, or TCL1-870 leukemia cells, and Eμ-TCL1 transgenic mice
Formulation Formulated as a 4 mg/mL solution in 0.1% carboxymethylcellulose sodium, 0.1% methylparaben, and 0.02% propylparaben (pH 6.5)
Dosages 80 mg/kg/day
Administration Intraperitoneal administration in 3 divided doses at 3-hour intervals

Conversion of different model animals based on BSA (Value based on data from FDA Draft Guidelines)

SpeciesMouseRatRabbitGuinea pigHamsterDog
Weight (kg)
Body Surface Area (m2)0.0070.0250.
Km factor36128520
Animal A (mg/kg) = Animal B (mg/kg) multiplied by  Animal B Km
Animal A Km

For example, to modify the dose of resveratrol used for a mouse (22.4 mg/kg) to a dose based on the BSA for a rat, multiply 22.4 mg/kg by the Km factor for a mouse and then divide by the Km factor for a rat. This calculation results in a rat equivalent dose for resveratrol of 11.2 mg/kg.

Rat dose (mg/kg) = mouse dose (22.4 mg/kg) ×  mouse Km(3)  = 11.2 mg/kg
rat Km(6)


[1] Braselmann S, et al. J Pharmacol Exp Ther, 2006, 319(3), 998-1008.

[2] Chen L, et al. Blood, 2008, 111(4), 2230-2237.

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Clinical Trial Information( data from http://clinicaltrials.gov, updated on 2016-07-30)

NCT Number Recruitment Conditions Sponsor
Start Date Phases
NCT02612558 Recruiting Warm Antibody Autoimmune Hemolytic Anemia Rigel Pharmaceuticals April 2016 Phase 2
NCT02611063 Recruiting Hematological Malignancies Stefanie Sarantopoulos, MD, PhD.|Duke University January 2016 Phase 1
NCT02433236 Withdrawn IGA Nephropathy Rigel Pharmaceuticals September 2015 Phase 2
NCT02076412 Active, not recruiting Immune Thrombocytopenic Purpura Rigel Pharmaceuticals November 2014 Phase 3
NCT02112838 Recruiting IGA Nephropathy Rigel Pharmaceuticals October 2014 Phase 2

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Chemical Information

Download R788 (Fostamatinib) Disodium SDF
Molecular Weight (MW) 624.42


CAS No. 1025687-58-4
Storage 3 years -20℃powder
2 years -80℃in solvent
Synonyms Tamatinib Fosdium
Solubility (25°C) * In vitro DMSO 6 mg/mL warming (9.6 mM)
Water <1 mg/mL
Ethanol <1 mg/mL
In vivo 0.5% CMC+0.25% Tween 80,pH6.5 30 mg/mL
* <1 mg/ml means slightly soluble or insoluble.
* Please note that Selleck tests the solubility of all compounds in-house, and the actual solubility may differ slightly from published values. This is normal and is due to slight batch-to-batch variations.
Chemical Name 2H-Pyrido[3,2-b]-1,4-oxazin-3(4H)-one, 6-[[5-fluoro-2-[(3,4,5-trimethoxyphenyl)amino]-4-pyrimidinyl]amino]-2,2-dimethyl-4-[(phosphonooxy)methyl]-, sodium salt (1:2)

Frequently Asked Questions

  • Question 1
    What’s the difference between S2625 and S2206?

    Answer: The differences between S2625 and S2206: 1. S2206 is more stable than S2625; 2. The water solubility of S2206 is better than S2625; 3. The absorption of S2206 is harder than S2625, so you need to test the suitable dosage if you use the product in animal assays; 4. The potency of S2206 and S2625 is similar.

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Cell Lines Assay Type Concentration Incubation Time Formulation Activity Description PMID
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