Development of Novel Neratinib and Docetaxel Core-Loaded and Trastuzumab Surface-Conjugated Nanoparticle for Treatment of HER-2 Positive Breast Cancer

<b>Background/Objectives</b>: This study developed a targeted drug delivery nanoplatform for treating HER2-positive breast cancer. The nanoplatform encapsulated two hydrophobic anticancer agents, neratinib (NTB) and docetaxel (DTX), within nanoparticles (DTX+NTB-NP) functionalized for conjugation to trastuzumab to form trastuzumab-tagged nanoparticles (TRZ-NP). Trastuzumab is a HER2-specific monoclo-nal antibody that binds to HER2 receptors, blocking signal transduction and inducing an-tibody-dependent cellular cytotoxicity (ADCC). Upon receptor-mediated endocytosis, neratinib inhibits cytosolic HER2 signaling, while docetaxel disrupts mitotic cell division, collectively leading to tumor cell death. <b>Methods</b>: Nanoparticles were fabricated by the nanoprecipitation technique, followed by surface modification with a crosslinker and a targeting moiety. DTX+NTB-NP, TRZ-NP, and singly loaded nanoparticles (NTB-NP and DTX-NP) were characterized and their effects evaluated in HER2-positive cancer cell line and xenograft model. <b>Results</b>: In vitro antiproliferation assay in SKBR-3 cell line re-veals a dose and time-dependent cytotoxicity. There was no significant difference in cyto-toxicity observed between DTX+NTB-NP and its free form (DTX+NTB) [p = 0.9172], and between TRZ-NP and its free form (TRZ+DTX+NTB) [<i>p</i> = 0.6750]. However, TRZ-NP, at half the concentration of the singly loaded nanoparticles, significantly reduced the viabil-ity of SKBR-3 cells compared to pure trastuzumab (TRZ) [<i>p</i> < 0.001], NTB-NP [<i>p</i> = 0.0019], and DTX-NP [<i>p</i> = 0.0002]. In vivo evaluation in female athymic nude mice showed sig-nificant log relative tumor volume (%) reduction in groups treated with TRZ-NP and DTX+NTB-NP compared to PBS (phosphate-buffered saline) controls (<i>p</i> ≤ 0.001 and <i>p</i> ≤ 0.001), respectively. Notably, TRZ-NP demonstrated a statistically significant regression in the log relative tumor volume (%) compared to DTX+NTB-NP (<i>p</i> = 0.001). <b>Conclusions</b>: These findings underscore the therapeutic potential and suitability of these nanoplatforms for the precise and controlled targeting of HER2-positive tumors. This study is the first to synchronize the delivery of multiple agents-docetaxel, neratinib, and trastuzumab-within a nanoparticle system for treating HER2-positive tumors, offering a promising strategy to enhance treatment outcomes for HER2 positive breast cancer patients.