Molecular Weight: 487.42 OTSSP167 is a highly potent MELK (maternal embryonic leucine zipper kinase) inhibitor with IC50 of 0.41 nM.
OTSSP167 inhibits A549, T47D, DU4475, and 22Rv1 cancer cells, in which
MELK is highly expressed, with IC50 values of 6.7, 4.3, 2.3, and 6.0 nM,
respectively. OTSSP167 inhibited the phosphorylation of PSMA1
(proteasome subunit alpha type 1) and DBNL (drebrin-like), which are
novel MELK substrates and are important for stem-cell characteristics
and invasiveness. OTSSP167 suppresses mammosphere formation of breast
cancer cells through the inhibition of PSMA1 phosphorylation.
OTSSP167 exhibits significant tumor growth suppression in xenograft
studies using breast, lung, prostate, and pancreas cancer cell lines in
mice by both intravenous and oral administration. In MDA-MB-231 model,
intravenous administration of OTSSP167 at 20 mg/kg once every two days
results in TGI of 73% The oral administration at 10 mg/kg once a day
reveals TGI of 72%. OTSSP167 for multiple cancer types in dose-dependent
and MELK-dependent manners with no or a little body-weight loss.
Protocol(Only for Reference)
Kinase Assay: 
|in vitro kinase assay||MELK recombinant protein (0.4 μg) is mixed with 5 μg of each substrate in 20 μL of kinase buffer containing 30 mM Tris-HCl (pH), 10 mM DTT, 40 mM NaF, 10 mM MgCl2, 0.1 mM EGTA with 50 μM cold-ATP and 10 Ci of [γ-32P]ATP for 30 min at 30 °C. The reaction is terminated by addition of SDS sample buffer and boiled for 5 min prior to SDS-PAGE. The gel is dried and autoradiographed with intensifying screens at room temperature. OTSSP167 (final concentration of 10 nM) is dissolved in DMSO and added to kinase buffer before the incubation.|
Cell Assay: 
|Cell lines||A549, T47D, DU4475, and 22Rv1, HT1197|
|Incubation Time||72 h|
|Method||Cell Counting Kit-8|
Animal Study: 
|Animal Models||MDA-MB-231, A549, DU145 xenografts|
|Dosages||1 mg/kg , 5mg/kg ,10 mg/kg, 20 mg/kg|
Conversion of different model animals based on BSA (Value based on data from FDA Draft Guidelines)
|Body Surface Area (m2)||0.6||0.5||0.24||0.15||0.05||0.025||0.02||0.007|
|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|
|Molecular Weight (MW)||487.42|
|Storage||3 years -20℃Powder|
|6 months-80℃in solvent (DMSO, water, etc.)|
|Solubility (25°C) *||In vitro||DMSO||0.5 mg/mL heating (1.02 mM)|
|Water||<1 mg/mL (|
|Ethanol||<1 mg/mL (|
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