AS2863619 free base enables conversion of antigen-specific effector/memory T cells into Foxp3 + regulatory T (T reg ) cells for the treatment of various immunological diseases. AS2863619 free base is a potent, orally active cyclin-dependent kinase 8 (CDK8) and CDK19 inhibitor with IC 50 s of 0.61 nM and 4.28 nM, respectively. STAT5 activation enhanced by AS2863619 free base inhibition of CDK8/19 , which consequently activates the Foxp3 gene In Vitro AS2863619 (1 μM; 22 hours; mouse CD4 + T cells) treatment suppresses serine phosphorylation of the PSP motif of STAT5b to ~40% while enhancing tyrosine phosphorylation in the C-terminal domain to ~160% of control-treated samples. MCE has not independently confirmed the accuracy of these methods. They are for reference only. Western Blot AnalysisCell Line: Mouse CD4 + T cells Concentration: 1 μM Incubation Time: 22 hours Result: Suppressed serine phosphorylation of the PSP motif of STAT5b to ~40% while enhancing tyrosine phosphorylation in the C-terminal domain to ~160% of control-treated samples. In Vivo AS2863619 (30 mg/kg; oral administration; daily; for 2 weeks; mice) treatment after sensitization with 2,4-dinitrofluorobenzene (DNFB) dampens the degree of the secondary response, with milder infiltration of inflammatory cells into the skin and decreases ratios of interferon-γ + (IFN-γ + ) cells in a skin contact hypersensitivity model, when compared with vehicle-treated control mice. T reg depletion before the elicitation of the secondary response abolishes AS2863619-induced suppression. KLRG1 + Foxp3 + T cells are specifically increased in DNFB sensitized AS2863619-treated mice . MCE has not independently confirmed the accuracy of these methods. They are for reference only. Animal Model: Mice with DNFB-induced contact skin hypersensitivity Dosage: 30 mg/kg Administration: Oral administration; daily; for 2 weeks Result: The degree of the secondary response, with milder infiltration of inflammatory cells into the skin and decreased ratios of interferon-γ + (IFN-γ + ) cells. Form:Solid IC50& Target:CDK8 0.61 nM (IC 50 ) CDK19 4.28 nM (IC 50 ) GSK3α 76.67 nM (IC 50 ) GSK3β 63.06 nM (IC 50 ) STAT5