A new immune-nanoplatform for promoting adaptive antitumor immune response.

Immunoliposomes (ILs), obtained with monoclonal antibodies (mAbs) decorating the liposome surface, are used for cancer treatment. These mAbs provide the recognition of molecules upregulated in cancer cells, like Programmed Death-Ligand 1 (PD-L1), an immune-checkpoint involved in tumor resistance, forming a complex that blocks this molecule and thereby, induces antitumor immune response. This mechanism introduces a new concept for ILs. ILs coupled to anti-PD-L1 or its Fab' fragment have been developed and in vitro/in vivo characterized. Factors such as coupling methods, PEG density and ligand size were optimized. In vitro data showed that Fab'-ILs displayed the highest PD-L1 cell interaction, correlating with a higher in vivo tumor accumulation and an increase of effector cytotoxic CD8+ T cells, providing tumor shrinkage and total regression in 20% of mice. Therefore, a novel immune-nanoplatform able to modulate the immune system has been developed, allowing the encapsulation of several agents for combinatorial therapies.

Regulation of in vivo behavior of TAT-modified liposome by associated protein corona and avidity to tumor cells.

INTRODUCTION: PEGylated liposomes are widely used and studied as carriers for chemotherapeutics. While pharmacokinetics of the encapsulated drug is drastically altered resulting in favorable circulation time, improved tumor accumulation, and better manageable or reduced side effects, therapeutic efficacy has been disappointing. Major drawbacks are a failure to reach the tumor cell, limited penetration depth, and impaired uptake by tumor cells. MATERIALS AND METHODS: Here, we study the implication of HIV-1 transactivator of transcription (TAT)-derived peptides inserted on PEGylated liposomal doxorubicin (PLD) and followed in vitro and in vivo fate. PLDs were installed with 25-400 TAT peptides per liposome without an effect on PLD stability. RESULTS: While TAT peptides facilitate active endocytosis of the carriers, we observed that these peptides did not promote endosomal escape or enhanced intracellular availability of doxorubicin. Interestingly, incorporation of TAT peptides did not change pharmacokinetics or biodistribution, which we found to result from a dysopsonization of the TAT-modified liposomes by serum proteins. A protein corona (PC) on TAT peptide-modified PLDs shields the active moieties and effectively reduces clearance of the TAT peptide containing nanoparticles. However, intratumoral activity was influenced by the number of TAT peptides present. The best antitumor efficacy was observed with a TAT peptide density of 100, while lower amounts showed results comparable to unmodified PLDs. At 200 TAT peptides, the preparation appeared to be least effective, which likely results from augmented interaction with tumor cells directly upon extravasation. CONCLUSION: We conclude that by optimizing TAT-modified PLDs, the occurring PC balances pharmacokinetics and tumor penetration through interference with avidity.