Reductant-Responsive Squalene Dual-Prodrug Nanoparticles Co-Delivering Doxorubicin and Exatecan for Synergistic Breast Tumor Therapy.

Background

combination chemotherapy employing agents with complementary mechanisms of action can enhance therapeutic efficacy and overcome resistance, but mismatched pharmacokinetics and systemic toxicity limit benefit.

Methods

We designed reductant-responsive squalene prodrugs of doxorubicin (DOX) and exatecan (EXA) that co-assemble with DSPE-PEG2k into approximately 76 nm dual-prodrug nanoparticles (doxorubicin prodrug-exatecan prodrug nanoparticles, DP-EP NPs) at a predefined synergistic ratio 1:2.

Results

The minimalist, drug-as-carrier formulation achieved high effective loadings with minimal leakage under normoxia, yet synchronously liberated both drugs in reductive, hypoxia-mimicking media (24 h release: DOX ~65% and EXA ~58% at 1 mM Na2S2O4 vs. ~8-11% at 0 mM Na2S2O4). In MCF-7 and 4T1 cells, the nanoparticles enhanced intracellular accumulation, intensified the disruption of DNA damage repair, as evidenced by increased colocalization of 53BP1 and enhanced γ-H2AX foci, and induced markers of immunogenic cell death, including increased CRT-associated cellular fluorescence and reduced intracellular HMGB1 staining. Furthermore, they partially reversed drug resistance in MCF-7/ADR cells. In rats, the formulation prolonged circulation and increased exposure (DOX t½ ~9×, AUC ~1.8×; EXA t½ ~5×, AUC ~14.9×) relative to the free-drug mixture. In 4T1 tumor-bearing mice, the nanoparticles produced the greatest tumor-growth inhibition with improved tolerability, supported by stable body weight and benign histopathology.

Conclusions

These findings establish a scalable, excipient-lean platform that aligns pharmacokinetics with microenvironment-triggered pharmacodynamics to deliver synchronized Topo II/I inhibition for synergistic chemotherapy.