Application Of Albumin Nanoparticles Modified With PD-L1 Aptamers And Loaded With Fexofenadine In Anti-tumor Immunotherap

Objective:Cancer is a major disease that threatens people’s lives around the world.Conventional cancer treatments include surgical resection,radiotherapy,and chemotherapy,but all of them have significant limitations.In recent years,tumor immunotherapy has become a hot research area in cancer treatment,and immune checkpoint blockade therapy(ICB)represented by PD-1/PD-L1 blockade is one of the most important antitumor immunotherapies.ICB therapy could reduce tumor immunosuppression and enhance antitumor function,which have achieved remarkable clinical results.Therefore,it is of potential medical importance to explore new technical approach to further enhance the efficacy of ICB therapy.At present,all PD-1/PD-L1 blockers approved for clinical use are antibodies.In addition to antibodies,aptamer may also inhibit the PD-1/PD-L1 axis.Aptamers are single-strand DNA or RNA with stable tertiary structure that can bind to molecular targets specifically.Aptamers have certain technical advantages,including low immunogenicity,better tumor penetration,and low batch-to-batch quality variations.Aptamers can also be employed as ICB agent in cancer immunotherapy.It is well recognized that the tumor immune microenvironment(TIME)can influence immunotherapy outcome.It has reported that fexofenadine,a specific H1-antihistamine,could modulate the TIME by reducing immunosuppressive M2-like macrophage and thereby improve T cell antitumor immunity.Therefore,a combination of ICB therapeutics with TIME-modulating agent theoretically may have the potential to further improve antitumor response.Here in this study,we designed a novel nanotherapeutic agent(PDL1-NP-FEXO)to co-deliver ICB reagent(PD-L1 aptamer)and tumor immune microenvironment modulator(FEXO)to further enhance the anti-tumor effect.To date,no published study has attempted to develop nanotherapeutics for cancer immunotherapy by co-delivery of PD-L1 aptamer with FEXO in one nanocarrier.Methods:Thiol-modified PD-L1 aptamer was conjugated to the amino groups of albumin via a standard linker.FEXO is loaded into PD-L1 aptamer functioned albumin nanoparticles to prepare PDL1-NP-FEXO.Agarose gel electrophoresis was used to verify whether the PD-L1 aptamader was successfully connected to albumin.The size,zeta potential,and polydispersity coefficient of nanoparticles are determined by dynamic light scattering.The morphology of the nanoparticles was studied by transmission electron microscopy.To determine the FEXO release profile,in vitro dialysis-based drug release assay and high performance liquid chromatography was performed.Fluorescence microscopy and flow cytometry were used to assess the affinity of PD-L1 aptamer functionalized nanoparticles(PDL1-NP)on PD-L1-expressing tumor cells.The antitumor efficacies of PDL1-NP and PDL1-NP-FEXO were determined by animal experiments,and their systemic toxic side effects were evaluated in the same time.Results:Dynamic light scattering study revealed that the average size of PDL1-NP-FEXO was 154.6 nm,and the zeta potential is-24.1 mV.Albumin nanoparticles carrying FEXO exhibit typical drug release characteristics.Similar to free PD-L1 aptamer,PDL1-NP could also bind with PD-L1-expressing tumor cells specifically.Of note,compared with free PD-L1 aptamer,PDL1-NP significantly boosted tumor inhibition in animal studies.Moreover,PDL1-NP-FEXO further enhanced the antitumor efficacy in vivo vs.PDL1-NP,without raising systemic toxicity,without generating extra systemic toxicity.Conclusion:In this study,we constructed a novel nanotherapeutic agent(PDL1-NP-FEXO)for cancer immunotherapy by attaching PD-L1 aptamers to albumin nanoparticles that were loaded with FEXO.Our results indicate that PDL1-NP-FEXO represents a promising strategy to improve ICB efficacy and may have application potential in cancer immunotherapy.