Cell lines

Human mast cells

Preparation method

The solubility of this compound in DMSO is >10 mM. General tips for obtaining a higher concentration: Please warm the tube at 37 ℃ for 10 minutes and/or shake it in the ultrasonic bath for a while.Stock solution can be stored below -20℃ for several months.

Reaction Conditions

EC50: 56 nM, 30min

Applications

Cells were incubated with R406 or DMSO for 30 min. They were then stimulated with either 0.25 to 2 mg/ml anti-IgE or anti-IgG or 2 μM ionomycin. R406 dose-dependently inhibited anti-IgE-mediated CHMC degranulation measured as tryptase release but showed no activity on ionomycin-triggered tryptase release, indicating that R406 is specific to FcR signaling and not degranulation per se. As intended, this specific inhibition also implies that R406 site of action is proximal to the receptor complex and upstream of calcium mobilization.

Animal models

Female C57BL/6 mice

Dosage form

Oral administration, 0.1, 0.5, 1 and 5 mg.kg

Applications

Mice were used for the model of immune complex - mediated inflammation. The ability of R406 to inhibit the reverse passive Arthus reaction was investigated in this model. Prophylactic treatment of mice with R406 administered 1 h before immune complex challenge reduced the cutaneous reverse passive Arthus reaction by approximately 72 and 86% at 1 and 5 mg/kg, respectively, compared with the vehicle control. The net optical density reading of extravasated dye extracted after treatment with R406 at 1 or 5 mg/kg R406 was reduced from 0.14 (vehicle) to 0.04 or 0.02, respectively.

Other notes

Please test the solubility of all compounds indoor, and the actual solubility may slightly differ with the theoretical value. This is caused by an experimental system error and it is normal.

R406 is a potent SYK inhibitorSpleen tyrosine kinase (SYK) is a non-receptor tyrosine kinase mainly expressed in hematopoietic cells. It transmits signals from a variety of cell surface receptors including CD74, Fc receptor and integrins. It is crucial for adaptive immune response, and also very important for cellular adhesion, innate immune recognition, osteoclast maturation, platelet activation and vascular development. [1]

Functional abnormality of SYK has been implicated in several blood malignancies. Constitutively active SYK can transform B cells. SYK inhibition can be beneficial for patients with blood cancers and autoimmune diseases.

R406 is a potent inhibitor of IgE and IgG mediated Fc receptor activation with EC50 for degranulation of 56-64 nM. [2] R406 targets SYK and inhibits phosphorylation of SYK substrates by binding to its ATP binding pocket and competing with ATP. R406 strongly inhibits SYK kinase activity with an IC50 of 41 nM.

R406 induces apoptosis in diffuse large B-cell lymphoma cell lines. It blocks B cell receptor signaling through inhibiton of SYK autophosphorylation of Y525/Y526 and SYK-dependent phosphorylation of the B-cell linker protein. [3]

R406 can be administrated orally.

References:
[1]Mocsai A, Ruland J, Tybulewicz VL. The SYK tyrosine kinase: a crucial player in diverse biological functions. Nat Rev Immunol 2010. 10(6): 387-402.
[2]Braselmann S, Taylor V, Zhao H, et al. R406, an orally available spleen tyrosine kinase inhibitor blocks fc receptor signaling and reduces immune complex-mediated inflammation. J Pharmacol Exp Ther 2006. 319(3): 998-1008.
[3]Chen L, Monti S, Juszczynski P, et al. SYK-dependent tonic B-cell receptor signaling is a rational treatment target in diffuse large B-cell lymphoma. Blood 2008. 111(4): 2230*2237.