Structure–Activity Relationship Studies in Substituted Oxadiazoles as Inducers of Extracellular Vesicles

We
characterized small-molecule compounds discovered through a
prior high-throughput screening campaign that enhanced the release
of immunostimulatory extracellular vesicles (EVs) and identified compound #645 (compound 1) as an immunomodulatory compound.
Here, we performed systematic structure–activity relationship
(SAR) studies to probe the scaffold for analogs inducing tetraspanin
(CD63) reporter activity, a marker of EV biogenesis and release, in
human THP-1 cells. A potent analog 39 was identified,
which also stimulated the expression of an immunostimulatory cytokine
and costimulatory molecules by antigen-presenting cells and promoted
antigen cross-presentation to CD8+ T cells. As its mechanism
of action, compound 39 was found to interfere with tubulin
polymerization, possibly binding to the nocodazole binding site on
beta-tubulin as evident by molecular docking studies. Additionally, 39 preferentially impaired the viability in proliferating
cells and may be a potential therapeutic agent for cancer and immunotherapy
applications.