ATP-responsive Nanoparticles for Reversal of Immune Evasion in Breast Cancer - Summary Antibody-drug conjugates (ADCs) have driven a revolution in the treatment of breast cancer; however, the long-term benefits on patients are still heterogeneous. ADCs induce immunogenic cell death of cancer cells, leading to anticancer immunity, and this plays a key role in antitumor response of ADCs. Therapy-induced anticancer immunity is often limited by immunosuppressive mechanisms posed by the tumor microenvironment (TME). Treatment of breast cancer cells with trastuzumab-emtansine (T-DM1), an ADC, causes extracellular ATP release, which initiates the recruitment of innate immune cells and in the priming of anti‐tumor immunity. However, extracellular ATP in the TME is quickly degraded into immunosuppressive adenosine via the concerted enzymatic activities of CD39 and CD73, dampening anticancer immunity. We hypothesize that ATP-responsive delivery of CD39/CD73 inhibitors with boronic acid (BA)-containing nanoparticles enables complementation of ADCs’ actions and the NP delivery, leading to synergistic anticancer actions at two levels. Firstly, cancer- targeting ADCs generate ATP to trigger the release of CD39/CD73 inhibitors from the NPs only in tumor sites, preventing off-target effects in normal tissues. Thereafter, the released enzyme inhibitors prevent conversion of ATP to Ado, enhancing and prolonging the immunogenic actions by ADCs, leading to durable tumor response. We have prepared BA-containing nanoparticles for ATP-responsive drug delivery. CD39 inhibitor ARL67156 (ARL), a nucleotide analogue, is loaded to the nanoparticles through the interaction with BA. The nucleotide drug can be released from the nanoparticles through replacement with ATP and other nucleotides. In preliminary studies, treatment of breast cancer cells with T-DM1 followed by NP-ARL increased extracellular ATP concentration and reduced the presence of adenosine. Combination therapy with T-DM1 and NP-ARL in EO711/HER2-bearing mice remodeled the TME into an immunostimulatory landscape. This change of immune landscape led to excellent immune-medicated tumor response in this syngeneic mouse model of breast cancer. In this proposal, we will explore the mechanisms for immune activation produced by ATP-responsive drug delivery, and will then enhance anticancer activity of our approach for providing an effective and safe therapy of HER2-low breast cancer. This project can be directly translated into a novel cancer immunotherapy treating BC that is aggressive and highly immune heterogeneous. Studies of this project will test the feasibility of using BA- based nanoparticles as a new delivery system for drug targeting, and thus will open a new research horizon for delivery of nucleotide/nucleoside drugs that can treat various diseases.
