Paclitaxel and Lapatinib dual loaded chitosan-coated PLGA nanoparticles enhance cytotoxicity by circumventing MDR1-mediated trastuzumab resistance in HER2 positive breast cancers: In-vitro and in-vivo studies

Treatment options for multidrug-resistant breast cancer are limited and ineffective. Few combinations of chemotherapeutic agents are clinically successful in treating multiple drug-resistant cancers. However, due to their varied pharmacokinetic characteristics, it is challenging to deliver dual drugs to the tumor simultaneously with the best proportion by simple co-administration. This study aimed to generate chitosan-coated PLGA nanoparticles delivering a synergistic combination of Paclitaxel (PTX) and Lapatinib (LPB) to improve efficacy in patients with multidrug-resistant breast cancer. In comparison to sensitive BT-474 cells, the 3:1 M ratio of PTX/LPB demonstrated significant synergism with a reversal index of approximately 13.4 in trastuzumab-resistant BT-474/TR cells. Particle diameters of the prepared chitosan (CS) PLGA Nps ranged from 157.4 +/- 9.2 to 263.5 +/- 13.5 nm. CS-coated Nps exhibited good EE and DL values of 80.8 +/- 3.4% and 1.5 +/- 0.12%, respectively. Moreover, CS-coating allowed successful co-delivery of PTX and LPB, resulting in the maximum in-vitro release within 72 h. Cytotoxicity against BT-474/TR cells was significantly increased when CS-coated dual loaded Nps were compared to other Nps, including free PTX, LPB, and their mixture. Quantification of the intracellular drug accumulation revealed that the encapsulation effectively increased drug uptake in BT-474/TR cells. These CS-coated dual loaded Nps exerted an excellent synergistic effect in BT-474/TR cells, leading to significantly improved cell inhibition via circumventing the MDR1 mediated trastuzumab resistance. Additionally, co-delivery of PTX and LPB demonstrated the most effective tumor growth reduction in the BT-474/TR human breast tumor xenograft compared to the saline control, single loaded PTX, and LPB Nps and a mixture of PTX and LPB combinations. The data suggest that CS-coated PLGA Nps loaded with PTX and LPB concurrently may be one of the most promising formulations for treating MDR1 mediated chemoresistance in HER2-positive breast tumors.