EHop-016 is an inhibitor of the small Rho GTPases Rac1 and Rac3. It inhibits Rac1 activity in MDA-MB-435 breast cancer cells with an IC50 value of 1.1 μM in a Rac1 activation assay. At a concentration of 1 μM, EHop-016 inhibits 58% of Rac3 activity, and it inhibits Cdc42 activity but only at higher concentrations (5-10 μM). It also increases Rho GTPase RhoA activity ~1.3-fold at concentrations greater than 2 μM. EHop-016 (2-4 μM) inhibits Rac-regulated functions in MDA-MB-435 cells, including lamellipodia formation and serine/threonine p21-activated kinase 1 (PAK1)-mediated cell migration. In a nude mouse model of breast cancer metastasis, EHop-016 (25 mg/kg) significantly lowers mammary fat pad tumor growth, metastasis, and angiogenesis. It also inhibits mutant receptor tyrosine kinase (KIT)-induced growth in systemic mastocytosis and acute myeloid leukemia (AML) cells (≥2.5 μM).
