Kinase experiment:

A scintillation proximity assay is used for radioligand competition binding assays with some modifications. For each assay point, 1 μg of membrane is preincubated for 1 hr with 300 μg wheat germ agglutinin (WGA) coated SPA beads in the binding buffer (50 mM HEPES, 1 mM CaCl2, 5 mM MgCl2, 125 mM NaCl, 0.002% NaN3, 1.0% BSA) at room temperature. The beads are spun down, resuspended in the binding buffer and transferred to a 96-well Isoplate. The indicated concentrations of 125I-hCXCL10, 125I-hCXCL11 or 35S-SCH 535390 with a series of titrations of SCH 546738 (1-10 μM) are added to start the reaction. After indicated reaction times at room temperature, the amount of radioactivity bound to the SPA beads is determined with a Wallac 1450 Microbeta counter[1].

Cell experiment:

The preparation of human activated T cells is performed. Human peripheral blood lymphocytes are prepared by Ficoll-Hypaque centrifugation, depleted of monocytes, and stimulated for 2 days with 1 μg/mL PHA and 100 U/mL IL-2 in RPMI 1640 supplemented with 10% fetal bovine serum (FBS), 2 mM L-Glutamine, 100 μg/mL Streptomycin, 100 U/mL Penecillin, 1% non-essential amino acids and 2 mM HEPES. Following stimulation, peripheral blood lymphocytes are cultured in above media containing 5% conditioned media for up to 15 days. uman activated T cell chemotaxis assays ae performed using 96-well ChemoTx microplates with a 3 μm filter. Activated T cells are washed with RPMI medium twice, and then resuspended in the medium containing 20% FBS. 1.25×105 cells/reaction are mixed with indicated concentrations of SCH 546738 (1, 10 or 100 nM) and placed on the filter. SCH 546738 and chemokines are mixed and placed in the bottom well of the ChemoTx system. After 2.5 hours incubation at 37℃/5% CO2, the cells are scraped off and the plate system is centrifuged for 5 minutes at 1000 RPM. The filter screen is then removed and the ChemoTx plate is inverted into a 96 well plate with a funnel plate. The plate system is centrifuged for 5 minutes at 1000 RPM. The volume in the wells is brought to 100 μL with assay buffer and the plates are rested for approximately 15 minutes at room temperature. The number of migrated cells is measured using the Cell Titer Glo Luminescent Assay. Chemotaxis is expressed as a chemotactic index, which is a ratio versus the one without chemokines[1]

Animal experiment:

Mice[1]Female C57BL/6 mice are used. For immunization, 150 μg MOG35-55 peptide prepared by Princeton Biomolecules and 300 μg killed Mycobacterium tuberculosis are mixed in CFA and injected s.c. in two 50-μL injections over the flanks on day 1. Also, 200 ng of pertussis toxin is injected i.v. on days 0 and 2. SCH 546738 is administered orally 30 mpk in C57BL/6 mice twice daily. Dosing with SCH 546738 started at day 0, 24 h prior to MOG35-55 immunization (day 1). Mice are monitored daily and assessed for clinical signs of disease in a blinded fashion according to the following criteria: 0, no signs of disease; 1, tail paralysis; 2, limp tail and hind limb weakness; 3, hind limb paralysis; 4, hind limb plus forelimb paralysis; and 5, moribund or dead. Cumulative clinical scores are calculated by adding daily scores from the day of immunization until the end of the experiment. Mean clinical scores at separate days and mean maximal scores are calculated by adding the scores of individual mice and dividing with the number of mice in each group, including mice not developing signs of EAE. Rats[1]Male Lewis rats challenged by injection of 50 μL (30 mg) of a guinea pig spinal cord homogenate in complete Freund's adjuvant (CFA) into one footpad. SCH 546738 or 0.4% methylcellulose (vehicle) is orally administered at the indicated dose (0.2 mL) twice a day, starting on the day before transplantation until the day of graft rejection. SCH 546738 is administered orally at 10 mg/kg (mpk) in Lewis rats. To test whether SCH 546738 enhances the effect of conventional immunosuppressive reagent, the recipients are received treatment with subtherapeutic dose of CsA for one week combined with treatment with SCH 546738. Graft survival is analyzed using the log-rank test. The parametric data are analyzed by Student t test (2-tailed) using GraphPad InStat version.

SCH 546738 is a potent, orally active and non-competitive CXCR3 antagonist, the affinity constant (Ki) of SCH 546738 binding to human CXCR3 receptor is determined to be 0.4 nM in multiple experiments. Human CXCR3|0.4 nM (Ki)

The affinity of SCH 546738 binding to human CXCR3 receptor is determined by competition binding analysis using 35S radiolabeled SCH 535390 (a sulfonamide analog of the CXCR3 compound series with a Kd of 0.6 nM) as a competitive tracer. In addition, SCH 546738 displaces radiolabeled CXCL10 and CXCL11 from human CXCR3 with IC50 ranging from 0.8 to 2.2 nM in a non-competitive manner. SCH 546738 potently and specifically inhibits CXCR3-mediated chemotaxis in human activated T cells with IC90 about 10 nM. Competition of human CXCL10 and CXCL11 binding to human CXCR3 by SCH 546738 is determined at various concentrations of [125I]hCXCL10 and [125I]hCXCL11 around the Kd (50-100 pM) for the receptor. The IC50 of SCH 546738 is constant (~1 or 2 nM) and independent of the input concentrations of either [125I]hCXCL10 (25-500 pM) or [125I]hCXCL11 (12.5-250 pM), respectively[1].

SCH 546738 has strong cross-species activities with IC50 of 1.3 nM, 6.4 nM, 5.9 nM and 4.2 nM in inhibiting the binding of [125I]hCXCL10 to CXCR3 of monkey, dog, mouse and rat origin, respectively. SCH 546738 is a selective and potent CXCR3 antagonist with a good PK for in vivo studies. In addition, SCH 546738 has a favourable pharmacokinetic profile in rodents, the plasma concentrations of SCH 546738 in Lewis rat and C57BL/6 mouse over 24 hr post-dose. The AUC (0-24 hr) is 7.7 μM.hr in Lewis rat 10 mg/kg (mpk) and is 12.6 μM.hr in C57BL/6 mouse 30 mpk[1].

[1]. Jenh CH, et al. A selective and potent CXCR3 antagonist SCH 546738 attenuates the development of autoimmune diseases and delays graft rejection. BMC Immunol. 2012 Jan 10;13:2. [2]. Zhang X, et al. CXC chemokine receptor 3 promotes steatohepatitis in mice through mediating inflammatory cytokines, macrophages and autophagy. J Hepatol. 2016 Jan;64(1):160-70. [3]. Yue C, et al. STAT3 in CD8+ T Cells Inhibits Their Tumor Accumulation by Downregulating CXCR3/CXCL10 Axis. Cancer Immunol Res. 2015 Aug;3(8):864-870.