This invention relates to compounds and their use as inhibitors or activators of Rab7 GTPase to treat or prevent the onset of Rab 7 GTPase-associated disorders such as neuropathies, cancer, metabolic diseases of bone and lipid storage. The invention is also applicable to infectious diseases where Rab7 is inactivated or its protein-protein interactions are modulated to facilitate intracellular survival of pathogens. The compound described acts as a competitive inhibitor of nucleotide binding and as such also has utility as a scaffold for targeting other small GTPases. In one aspect, methods of treatment of the invention are used to treat or prevent the onset of hereditary sensory neuropathies such as Charcot-Marie-Tooth type 2B disease. Related pharmaceutical compositions, assays, and drug screens are also provided.