The present invention relates to molecules which function as modulators (i.e., inhibitors and agonists) of the Ras-homologous (Rho) family of small GTPases (e.g. Rac, Cdc42 and Rho GTPases) and their use to treat diseases, including cancers (including solid tumors-medulloblastoma, ovarian, breast, head and neck, testicular, prostate among others and hematologic malignancies-B cell lymphoma, where these GTPases are overexpressed or hyperactivated), sporadic and genetic diseases where activation of Rho GTPases plays a pivotal role (Menkes disease, rheumatoid arthritis, atherosclerosis, diabetes (type I), Huntington's disease and Alzheimer's disease) which are mediated through these proteins. Compounds according to the present invention may also be used as a therapy for the treatment of Entamoeba spp. or Acanthamoeba spp. infections, especially including Entamoeba histolytica.