Background: Exosomes are extracellular vesicles (EVs) that produced in the endosomal compartment of most eukaryotic cells, and have observed increasing attentions over the past decades. They play important roles in cell- to-cell communications, they can carry varieties of substances, like proteins, nucleic acids and lipids, to the target cells they encounter. These cargos could influence the function of recipient cells. This novel mode of intercellular communication is found to be of critical importance to many cellular activities. However, exosomes are involved in various diseases processes. Tumor- derived exosomes could promote cancer progression, and our preliminary study indicated that exosome released from osteoclasts could inhibit bone formation. We also found that osteoarthritis (OA) progression in OA mice could be attenuated by inhibiting exosomes released by osteoclasts. Therefore, inhibition of exosome release has potential value in the treatment of diseases. The exosome release is under control by RAB27A, which is a protein involved in protein transport and signal transduction. It is reported that a compound named Nexinhib20 could selectively inhibit RAB27A, but this compound is highly toxic to RAW264.7 cells, which IC 50 is 1.5 µM. Therefore, for safety concerns, it has to be chemically modified to reduce toxicity. Aim: (1) To design and synthesize a series compounds based on the structure of Nexinhib20. (2) To evaluate the toxicity and exosome inhibiting activity of the synthesized compounds and discuss the structure-activity relationships (SAR) of them. Materials and Methods: Nexinhib20 derivatives were synthesized by aldol reaction. The cytotoxicity of these compounds was evaluated by MTT assay. The exosome inhibiting activity of these compounds was evaluated through exosome isolation and quantitation. Result: A series of compounds were synthesized and their structures were confirmed by LC-MS and NMR. The structure-activity relationships of these compounds were discussed, and the results showed that compounds A3, A23 and B2 exhibited lower toxicity compared to Nexinhib20 and strong exosome inhibiting ability. Conclusion: The results of this project indicate that A3, A23 and B2 exhibited low toxicity and good exosome inhibiting activity. Based on this, further chemical modification could be applied to develop new exosome inhibitors with better efficacy

Thesis (M.Sc. (Pharmacy)) - Rhodes University, 2007.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--Pardee Rand Graduate School, 2009. / Title from PDF t.p. Includes bibliographical references.