Fenretinide-loaded mesenchymal stem cells-derived extracellular vesicles as novel drug carriers against human neuroblastoma

Fenretinide (4-HPR) is a synthetic retinoid with little adverse effects, whose antitumor efficacy has been widely demonstrated. Unfortunately, clinical responses both in adult and pediatric patients are partial, revealing a limited activity of 4-HPR against existing disease. The underlying causes of this slight therapeutic efficacy consist in its poor water solubility, low bioavailability and high first-pass hepatic effect. As a result, new formulations are required to improve clinical outcomes. To this end, we propose a new 4-HPR formulation based on mesenchymal stem cells derived extracellular vesicles (EVs) as endogenous carriers for drug delivering. After isolation from human umbilical cord, the mesenchymal stem cells were treated with high doses of 4-HPR to achieve a passive drug loading. The resulting 4-HPR-EVs were collected, purified by ultracentrifugation and characterized for size, concentration. The drug amount encapsulated into the vesicles was determined by HPLC and to estimate the analyte recovery the internal standard N-(4-ethoxyphenyl)-retinamide was synthetized by us. We evaluated the EV uptake and efficacy on neuroblastoma cell lines cultured both in 2- and 3-D.