<p>The immunosuppressive tumor microenvironment (TME) undermines the efficacy of many cancer therapies. This study investigated the immunomodulatory and anti-tumor activity of Azvudine (FNC), alone or in combination with anti-PD-1 blockade. We established syngeneic tumor models in immunocompetent mice. Single-cell RNA sequencing, flow cytometry, and immunological assays were employed to analyze immune cell reconstitution and functional changes following FNC administration. FNC demonstrated dose- and time-dependent tumor inhibition. It significantly expanded memory T cells, natural killer (NK) cells, and CD8⁺ cytotoxic T lymphocytes, while reducing the abundance of myeloid-derived suppressor cells (MDSCs). Flow cytometry confirmed these immunological shifts, showing enhanced infiltration of effector immune cells within the TME. Moreover, FNC induced hallmark features of immunogenic cell death (ICD), including the release of damage-associated molecular patterns such as high-mobility group box 1 (HMGB1) and calreticulin. When combined with anti-PD-1 therapy, FNC produced a synergistic anti-tumor effect, leading to durable tumor remission in all treated mice. FNC remodels the TME by mitigating immunosuppression and amplifying anti-tumor immunity, offering a promising strategy to augment existing immunotherapies. Further clinical evaluation is warranted to ascertain the translational potential of FNC in diverse oncologic settings.</p>