The barriers from cancer-associated fibroblasts (CAFs) have diminished the clinical efficacy of immunotherapy for triple-negative breast cancer (TNBC). The obstacles from CAFs often result in poor drug penetration, constrained cytotoxic T lymphocyte infiltration, and an immunosuppressive microenvironment. Herein, chondroitin sulfate (CS) was engineered to conjugate dasatinib (DAS), a tyrosine kinase inhibitor, via the cathepsin B (CTSB)-responsive GFLG linker to produce CS-GFLG-DAS (CGD), which could be employed to reverse the CAF phenotype and regulate the biosynthesis of extracellular matrix (ECM), thus enhancing the efficacy of immune checkpoint blockade (ICB) therapy. Upon reaching the tumor site, DAS released from CGD in response to overexpressed CTSB in the tumor microenvironment could transform CAFs into a quiescent state instead of killing them to prevent CAFs from producing abundant ECM, thereby promoting deep penetration of CGD to effectively kill tumor cells. In addition, ECM remodeling facilitated tumor infiltration of cytotoxic T lymphocytes, synergistically enhancing the anti-PD-1 efficacy in the 4T1 tumor-bearing mice. In summary, this prodrug enhanced deep drug penetration and therapeutic sensitivity of anti-PD-1 by regulating CAFs, providing new insights into optimizing immunotherapy in treating fibrotic tumors via nanomedicine.Copyright © 2025 Elsevier B.V. All rights reserved.