Abstract: The present invention relates to molecules which function as selective modulators of the Ras-homologous (Rho) family of small GTPases, in particular, Cdc42 GTPase and their use to treat diseases, for example cancers, including metastatic cancer, genetic and acquired diseases where activation of Cdc42 GTPase plays a pivotal role, such as neurodegenerative diseases, rheumatoid arthritis, atherosclerosis, diabetes type I, autosomal polycystic kidney disease, cystic kidney disease, precystic kidney disease, microbial infections, including Chlamydia infections, E. coli infections, H. pylori infections and its secondary effects including gastric ulcers, Coxiella Brunetti (Q-fever) infections and Streptococcus pneumonia infections, fungal infections including Paracoccidiodes brasiliensis and Candida albicans and their secondary effects including lung edema.