Oxymatrine and astragaloside IV co-loaded liposomes: Scale-up purposes and their enhancement of anti-PD-1 efficacy against breast cancer

The response rate of programmed cell death protein-1 (PD-1) inhibitors in breast cancer remains unsatisfactory, primarily due to the limited infiltration and activity of tumor-infiltrating T lymphocytes (TILs). Previous studies demonstrated that oxymatrine (Om) and astragaloside IV (As) could enhance TIL infiltration and function by inhibiting cancer-associated fibroblasts (CAFs) and promoting mitochondrial activity in TILs, respectively. Thus, combining Om and As may be a promising strategy to improve the antitumor effects of PD-1 inhibitors in breast cancer. However, co-delivery above drugs into breast cancer tissue is challenging due to their low bioavailability and distinct physicochemical properties. This study addresses this challenge by formulating Om and As co-loaded liposomes (Om-As-Lip) and comparing the scale-up production methods: high-pressure homogenization (EP-HPH) and microfluidics. Om-As-Lip prepared via microfluidics demonstrated superior entrapment efficiency (As: 99.03 ± 0.04%, Om: 67.01 ± 0.02%) and a significantly higher production rate (22.12 mL/min) compared to EP-HPH (1.19 mL/min). Additionally, Om-As-Lip produced by microfluidics increased the area under the curve (AUC) (Om: 6.17-fold, As: 2.07-fold) and maximum concentration (Cmax) (Om: 1.58-fold, As: 3.49-fold) compared to the free drugs. Importantly, Om-As-Lip enhanced the antitumor efficacy of α-PD-1 by inhibiting CAF activation and boosting TIL activity, resulting in a tumor inhibition rate of 61.2% and extended survival in mice. This work presents a novel perspective for scaling up co-delivered formulations of drugs with differing polarities to improve breast cancer immunotherapy.