Synergistic Chemo-Immunomodulation via Nanocarrier Co-Delivery of Doxorubicin and Pexidartinib

Introduction: Despite the widespread use of doxorubicin (DOX) as a chemotherapeutic agent, its effectiveness is often limited by the development of resistance in various cancers. Therefore, combination therapy has gained increasing attention as an effective strategy to enhance doxorubicin's efficacy and overcome resistance in cancer cells. Pexidartinib (PLX), a colony-stimulating factor 1 receptor inhibitor, decreases immunosuppressive tumor-associated macrophages and reprograms the functions of the remaining macrophages, which may help reverse chemoresistance. Consequently, developing a nanosystem capable of efficiently co-delivering PLX and DOX while addressing the challenges associated with dual drug delivery is expected to overcome resistance mechanisms and improve therapeutic outcomes. Methods: We designed and characterized a crosslinked nanoparticle based on β-cyclodextrin (β-CD) for effective co-delivery of DOX and PLX. The physicochemical properties of the nanoparticles were characterized, and their therapeutic efficacy was evaluated in vitro and in vivo. Results: The nanoparticles exhibited an average particle size of ~ 100 nm and a zeta potential of around +2 mV, indicating excellent stability. The entrapment efficiency exceeded 90% for both drugs. The release profile of DOX from the nanoparticles showed a pH-dependent pattern, with preferential release at pH 5 compared to physiological pH. Synergistic effects between DOX and PLX were observed in colorectal and breast cancer cell lines, with combination index (CI) values consistently below 1 across multiple drug ratios. Biodistribution and deep tissue penetration studies demonstrated preferential accumulation in tumor tissue over normal tissue. Moreover, the co-loaded nanoparticles significantly improved therapeutic efficacy compared with single-drug treatments in a subcutaneous MC38 tumor model. Flow cytometry analysis revealed increased CD8⁺ and decreased exhausted CD4⁺ cells after combination therapy. Conclusion: These results demonstrate that the co-delivery of DOX and PLX using a crosslinked nanoparticle system provides a promising strategy to enhance anticancer efficacy and overcome chemoresistance.