Structure-Based Discovery of Receptor Activator of Nuclear Factor-κB Ligand (RANKL)-Induced Osteoclastogenesis Inhibitors.

Receptor activator of nuclear factor-κB ligand (RANKL) has been actively pursued as a therapeutic target for osteoporosis, given that RANKL is the master mediator of bone resorption as it promotes osteoclast differentiation, activity and survival. We employed a structure-based virtual screening approach comprising two stages of experimental evaluation and identified 11 commercially available compounds that displayed dose-dependent inhibition of osteoclastogenesis. Their inhibitory effects were quantified through TRAP activity at the low micromolar range (IC50 < 5 µΜ), but more importantly, 3 compounds displayed very low toxicity (LC50 > 100 µΜ). We also assessed the potential of an N-(1-aryl-1H-indol-5-yl)aryl-sulfonamide scaffold that was based on the structure of a hit compound, through synthesis of 30 derivatives. Their evaluation revealed 4 additional hits that inhibited osteoclastogenesis at low micromolar concentrations; however, cellular toxicity concerns preclude their further development. Taken together with the structure-activity relationships provided by the hit compounds, our study revealed potent inhibitors of RANKL-induced osteoclastogenesis of high therapeutic index, which bear diverse scaffolds that can be employed in hit-to-lead optimization for the development of therapeutics against osteolytic diseases.

A versatile δ-aminolevulinic acid (ΑLA)-cyclodextrin bimodal conjugate-prodrug for PDT applications with the help of intracellular chemistry.

Grafting of δ-aminolevulinic acid (1) moieties on the narrow periphery of a ß-cyclodextrin (ß-CD) derivative through hydrolysable bonds was implemented, in order to generate a water-soluble, molecular/drug carrier with the capacity to undergo intracellular transformation into protoporphyrin IX (PpIX), an endogenous powerful photosensitizer for photodynamic therapy (PDT). The water-soluble derivative 2 was prepared by esterifying δ-azidolevulinic acid with heptakis(6-hydroxyethylamino-6-deoxy)-ß-cyclodextrin, with an average degree of substitution, DS = 3. Delivery of water-soluble, colorless 2 to cells resulted in intense red fluorescence registered by confocal microscopy, evidently due to the engagement of the intracellular machinery towards formation of PpIX. Conjugate 2 was further complexed with a fluorescein-labeled model guest molecule which was successfully transported into the cells, thereby demonstrating the bimodal action of the derivative. The present work shows the versatility of CDs in smart applications and constitutes advancement to our previously shown PpIX-ß-CD conjugation both in terms of water solubility and lack of aggregation.