Sequential co-delivery of gemcitabine and nintedanib via mPEG-PLG nanomicelles for enhanced breast cancer chemotherapy

The combination of the antiangiogenic agent nintedanib (BIBF) with the antimetabolite gemcitabine (GEM) represents a mechanistically rational yet clinically challenging strategy for breast cancer therapy. However, its clinical translation has been hindered by mismatched pharmacokinetics and the absence of a delivery system capable of coordinating their temporal release profiles. In this study, we developed a polymer-based nanoplatform designed to achieve sequential drug release: rapid initial release of BIBF to modulate the tumor microenvironment, followed by sustained release of GEM to exert cytotoxic effects. The gemcitabine prodrug (mPEG-PLG- GEM) was synthesized via covalent conjugation and subsequently used to prepare dual-loaded nanomicelles (mPEG-PLG-GEM@BIBF) through thin-film hydration. This system exhibited a well-defined sequential release profile in vitro, with BIBF released faster than the GEM prodrug. An optimal synergistic molar ratio (GEM:BIBF = 3:1) was identified. The nanomicelles (∼134.5 nm) enhanced the plasma stability and prolonged the systemic circulation of both drugs (half-lives of GEM increased from 1.38 h to 5.90 h; BIBF from 4.35 h to 8.90 h). Biodistribution studies showed increased tumor accumulation, with the intratumoral GEM:BIBF ratio maintained within the synergistic range around the target ratio of 3:1. In a 4T1 murine breast cancer model, mPEG-PLG-GEM@BIBF achieved a superior tumor inhibition rate of 77.84%, significantly outperforming the free drug combination (50.63%) and GEM monotherapy (33.54%), while also demonstrating a reduced systemic toxicity profile. This work presents a co-delivery nanoplatform designed to coordinate the release and tumor exposure of BIBF and GEM. The improved therapeutic effect is likely associated with the coordinated pharmacokinetics, enhanced tumor accumulation, and BIBF-faster-than-GEM release profile of the nanomicelles. Although direct evidence of vascular normalization and intracellular GEM activation was not obtained in this study, the results support a promising sequential co-delivery strategy for improving GEM/BIBF combination chemotherapy in breast cancer. Download: Download high-res image (206KB) Download: Download full-size image