Abstract 978: Spatial-temporal delivery of OX40 agonist and PD-1 inhibitor using nanoparticles improves therapeutic efficacy of cancer immunotherapy (2017)

Abstract Background: Cancer immunotherapy is an exciting new approach to cancer treatment and there is strong interest in strategies to improve the long-term durable response rates of cancer immunotherapy. One approach is to combine checkpoint inhibitors such as aPD-1 with T cell activator such as OX40 agonist to further increase immune activation. We hypothesized that we can improve the therapeutic efficacy of this approach by temporally control the activation of OX40 and inhibition of PD-1 pathways. To accomplish this, we utilized nanoparticles that can deliver anti-OX40 and anti-PD1 antibodies simultaneously to T cells. Methods: Agonist antibody (anti-OX40) and antagonist antibody (anti-PD1) were conjugated to PLGA-PEG-Maleimide nanoparticles (AANPs) with precise ratio control and quantified by ELISA. Their specific binding to the target proteins was shown in vitro by flow cytometry. The tumor inhibition efficiency was assessed on mice bearing different tumor models. Two tumors were inoculated subcutaneously (105 B16F10 cells) or on fourth mammary fat pad (105 4T1 cells) on both flanks of mice. One side of tumor was irradiated once and AANPs were injected twice every 3 days. In vivo depletion experiments were tested on C56Bl6 mice and CD11b/c mice. Different populations of T cells in tumor and spleen were analyzed by flow cytometry and by fluorescent IHC staining. T cell killing assay and IFN-γ ELISpot were studied. Co-localization was demonstrated with fluorescent labeled antibodies and the corresponding AANPs. Results: AANPs showed a 30% cure rate, compared to 10% of free antibodies, 0% of anti-PD1 conjugated NPs, and 0% of anti-OX40 conjugated NPs in B16F10 melanoma model. We then re-challenged the cured mice with 2×105 B16F10 cells and none of the mice developed another tumor. In 4T1 breast cancer model, the survival rate on day 39 was 50% with AANPs treatment, compared to 22% in the mixture of anti-PD1 conjugated nanoparticles and anti-OX40 conjugated nanoparticles, and 0% of free antibodies. We demonstrated that AANPs led to a higher medium TCD8+/Treg ratio in tumors. The therapeutic effect was mediated by CD8+ T cells as elimination of these cells abrogated the therapeutic effects. In vitro study confirmed that AANPs were able to improve T cell stimulation compared to free antibodies by increasing IFN-γ excretion (2x). We further confirmed co-localization of antibodies with AANPs on tumor infiltration T cells in vivo. Our data demonstrated that spatial-temporal delivery of agonist and antagonist could improve T cell activation and cancer immunotherapy. Conclusions: Our data demonstrates that spatial-temporal delivery of agonist and antagonist can improve T cell activation and cancer immunotherapy. Citation Format: Yu Mi, Christof C. Smith, Feifei Yang, Jonathan Serody, Benjamin Vincent, Andrew Z. Wang. Spatial-temporal delivery of OX40 agonist and PD-1 inhibitor using nanoparticles improves therapeutic efficacy of cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 978. doi:10.1158/1538-7445.AM2017-978