MS-444 inhibits the activity of purified smooth muscle myosin light chain kinase ( MLCK ) with an IC 50 value of 10 μM. In Vitro MS-444 is a small molecule RNA-binding protein HuR (ELAVL1) inhibitor. Colorectal cancer (CRC) cells that display HuR overexpression are treated with MS-444 (1-100 μM) for 48 hr with IC 50 s of 10.98±1.76 μM, 12.84±2.10 μM, 5.60±0.90 μM, 14.21±2.11 μM, and 10.98±1.24 μM for HCT116, HCA-7, RKO, HT-29, and SW480 cells, respectively. Growth inhibition is observed in all CRC lines with IC 50 values ranging from 5.60 μM to 14.21 μM with observable effects seen at 10 μM MS-444. Contrasting effects are observed using non-transformed small intestinal (RIE-1 (IC 50 =40.70±3.53 μM)) and colonic (YAMC (IC 50 =28.16±3.23 μM)) epithelial cells. Both cell types display properties of normal intestinal epithelial cells and are proficient in 3′UTR AU-rich elements (ARE)-mRNA decay. Both non-transformed cell lines are ~3- to 4-fold less responsive to MS-444-mediated growth inhibition, with IC 50 values of 40.70 μM and 28.16 μM ( P In Vivo To test the effects of MS-444 on CRC cell growth in vivo, mice bearing HCT116 cell xenografts receive IP injections of MS-444 (25 mg/kg bw) or vehicle every 48 hr. Over the experiment course, mice do not display any adverse effects and maintained similar weights. Anti-tumor effects of MS-444 are observed with approximately 1.7-fold reduction in tumor size. Mice treated with MS-444 show a marked 2- to 3-fold decrease in microvessel density (MVD), indicating the anti-angiogenic potential of MS-444. MCE has not independently confirmed the accuracy of these methods. They are for reference only. Cell Assay Human colorectal cancer cell lines RKO , HCA-7 , HCT116 , HT-29 , SW480 and the non-transformed intestinal epithelial cell lines RIE-1 , YAMC are treated with varying concentrations of MS-444 (1-100 μM) for 48 hr. Cell survival is measured by MTT assay after incubation of cells for 48 hr with MS-444. Relative cell survival is calculated as percentage normalized to DMSO vehicle-treated cells and plotted to determine IC 50. MCE has not independently confirmed the accuracy of these methods. They are for reference only. Animal administration Mice Athymic nude (Nu/Nu) mice are used. HCT116 (2×10 6 cells) and HCA-7 (2.5×10 6 ) cells resuspended in PBS are injected into the dorsal subcutaneous tissue. Mice (n=5 per group) receive intraperitoneal ( IP ) injections of MS-444 ( 25 mg/kg ) dissolved in PBS/5% N-Methyl Pyrrolidine (NMP) or vehicle control every 48 hr. Tumor growth is assayed . aladdin has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid IC50& Target:IC50: 10 μM (myosin)