Furin plays a crucial role in embryogenesis and homeostasis and in diseases such as Alzheimer's disease, cancer, and viral and bacterial infections. Thus, inhibition of furin may provide a feasible and promising approach for therapeutic intervention of furin-mediated disease mechanisms. Here, we report on a class of small molecule furin inhibitors based on 2,5-dideoxystreptamine. Derivatization of 2,5-dideoxystreptamine by the addition of guanidinylated aryl groups yielded a set of furin inhibitors with nanomolar range potency against furin when assayed in a biochemical cleavage assay. Moreover, a subset of these furin inhibitors protected RAW 264.7 macrophage cells from toxicity caused by furin-dependent processing of anthrax protective antigen. These inhibitors were found to behave as competitive inhibitors of furin and to be relatively specific for furin. Molecular modeling revealed that these inhibitors may target the active site of furin as they showed site occupancy similar to the alkylating inhibitor decanoyl-Arg-Val-LysArg-CH 2Cl. The compounds presented here are bona fide synthetic small molecule furin inhibitors that exhibit potency in the nanomolar range, suggesting that they may serve as valuable tools for studying furin action and potential therapeutics agents for furindependent diseases.serine endoprotease ͉ prohormone ͉ proprotein convertase F urin is a membrane-anchored, calcium-dependent serine endoprotease and is expressed in all tissues and cell lines examined (1-3). It is the first and, so far, the best-characterized member of the mammalian subtilisin-like family of prohormone/proprotein convertases (PCs), which convert precursors of many secreted proteins and peptide hormones into their biologically active forms (1-3). Furin is predominantly localized in the trans-Golgi network and cycles between this compartment, the cell surface, and the endosomes (2, 4). Hence, furin is able to access and efficiently process a diverse spectrum of substrates including growth factors, receptors, serum proteins, matrix metalloproteinases, viral envelope glycoproteins, and bacterial toxins, typically at sites with the consensus sequence Arg-Xaa-Lys/Arg-Arg 2 (2).Although furin plays an essential role in embryogenesis and homeostasis, this endoprotease has also been implicated in the neurodegeneration associated with Alzheimer's disease, and tumor metastasis and the activation and virulence of many bacterial and viral pathogens (2). It has been demonstrated that furin inhibitors modulate tumor growth (5) and attenuate the toxicity of anthrax (6) and Pseudomonas aeruginosa (7) toxins and cytomegalovirus (8) in cell culture and animal models. Therefore, furin inhibitors hold great promise as potential therapeutic agents for treating furinmediated diseases and viral and bacterial infections, particularly for short-term therapy.To date, most furin inhibitors reported in the literature have been proteins (9-19) or peptides (20-24), which show excellent potency against furin, and largely mimic the substrate in bindi...
