GSH-responsive nanoparticle drug delivery system for simultaneous blockade of CD73/A2AR to reverse adenosine-mediated immunosuppression.

The adenosine signaling pathway is a key mechanism of tumor immune evasion, collaboratively promoting immunosuppression through CD73-mediated adenosine production and A2AR-mediated signal transduction. This study designed and synthesized two novel conjugates, BSC and BSPC, which chemically link the CD73 inhibitor betulinic acid (BA) and the A2AR antagonist CPI-444 via a disulfide bond. These conjugates were further fabricated into glutathione (GSH)-responsive nanoparticles, namely BSC NPs and BSPC NPs. This nano-delivery system leveraged enhanced permeability and retention (EPR) effect for tumor-targeted delivery and enabled controlled drug release triggered by the high GSH concentration of the tumor microenvironment (TME). The nanoparticles possessed favorable colloidal stability, biocompatibility, and hemocompatibility. In the 4T1 triple-negative breast cancer BALB/c mouse xenograft model, BSC NPs exhibited significant antitumor efficacy and effectively promoted the infiltration of T cells. Furthermore, combination therapy with BSC NPs and an anti-PD-L1 antibody demonstrated a synergistic effect, markedly enhancing the antitumor immune response without inducing significant systemic toxicity. This study provides a novel nano-based combination therapy strategy for reversing adenosine-mediated immunosuppression.