Animal experiment:

Mice[1]Female athymic nu/nu mice, 4 to 5wk old are used. GFP-HER2-BM cells (~5×105) in Matrigel are injected at the fourth right mammary fat pad under isofluorane inhalation to produce orthotopic primary tumors. After tumor establishment (1wk post-inoculation), animals are randomly divided into treatment groups (n=6). Mice are treated with vehicle (12.5% ethanol, 12.5% Cremophor, and 75% 1X PBS pH 7.4), or 1 or 10 mg/kg BW MBQ-167 by i.p. injection in a 100 μL volume 3X a wk. Treatments continue until sacrifice at day 65[1].

• 1.Xu, Qiong, et al. "POTEE promotes colorectal carcinoma progression via activating the Rac1/Cdc42 pathway." Experimental Cell Research (2020): 111933.

MBQ-167 is a dual Rac/Cdc42 inhibitor, with IC50s of 103 nM for Rac 1/2/3 and 78 nM for Cdc42 in MDA-MB-231 cells, respectively.

MBQ-167 (≥100 nM) induces a loss of polarity in metastatic breast cancer cells. Treatment with 500 nM MBQ-167 for 24 h results in ~95% cell rounding and detachment from the substratum in metastatic MDA-MB-231 cells. Moreover, MBQ-167 induces this phenotype in multiple mesenchymal cancer cell types including GFP-HER2-BM, MDA-MB-468, and Hs578t human breast cancer cells, as well as Mia-PaCa-2 pancreatic cancer cells, SKOV3 ovarian cancer cells, AGS and NCI-N87 gastric cancer cells, and SH-SY5Y neuroblastoma cells. Following treatment with 250 nM MBQ-167 for 24 h, the attached population of MDA-MB-231 cells demonstrate a ~25% decrease in Rac activation while the detached cells are more responsive with a ~75% decrease. At earlier times (6h), treatment with 250 or 500 nM MBQ-167, induce a inhibition in Rac activity in the attached cell population, while the detached population demonstrate a ~40-50% inhibition[1].

MBQ-167-treated mice demonstrate a statistically significant reduction in tumor growth. At sacrifice, 1.0 mg/kg BW of MBQ-167 results in a ~80% reduction in tumor growth, and the 10 mg/kg BW MBQ-167 treatment results in ~95% reduction in tumor growth. Since EHop-016 only exerts ~40% reduction of tumor growth at 10 mg/kg BW, MBQ-167 is 10X more effective than EHop-016. MBQ-167 treated mice demonstrate similar doubling times for both treatments (10 and 11 days)[1].

[1]. Humphries-Bickley T, et al. Characterization of a Dual Rac/Cdc42 Inhibitor MBQ-167 in Metastatic Cancer. Mol Cancer Ther. 2017 May;16(5):805-818.