The in vivo delivery of therapeutic nanoparticles (NPs) represents a potentially powerful tool that can significantly alter the biological effects of pharmaceutically active compounds. Here, we report on sensitization of tumors to chemotherapy by ammonium trichloro(dioxoethylene-o,o')tellurate (AS101) encapsulated in NPs, termed AS101-NPs, developed as a composite with the biocompatible and biodegradable copolymer of poly(d,l-lactic-co-glycolic acid)-block-poly(ethylene glycol) (PLGA-b-PEG). AS101 is a potent immunomodulating agent (both in vitro and in vivo) currently undergoing phase II clinical trials for antitumor activity and sensitization of tumors to chemotherapy. Approaches that can control the pharmacokinetic parameters to regulate its clearance from the administered drug delivery system and minimize side effects are of prodigious importance. A strategy to synthesize AS101-NPs by nanoprecipitation is presented, along with their physical characterization. The influence of AS101 encapsulation on its properties was evaluated in vivo. The AS101-NPs demonstrated a significantly enhanced peritoneal macrophage count compared with AS101 administered in vivo at a conventional dosage in mouse models. Moreover, AS101 inhibited B16 melanoma lung metastasis in mice when given intraperitoneally, before or after tumor cell inoculation. A bell-shaped dose-response was observed. The frequency of AS101 administration appears to be an important factor for achieving an optimal antimetastatic effect.
Keywords: AS101; PLGA−PEG; antimetastatic effect; dose−response; immunomodulating agent; melanoma lung metastasis.