Dually-decorated palmitate-containing lipid nanoparticles for the targeted delivery of siRNAs against HER2 and Hsp27 in HER2+ breast cancer

ABSTRACT Ionizable lipid nanoparticles (LNPs) have enabled significant advances in oligonucleotide therapeutics, culminating in the clinical approval of an siRNA-based formulation. Unfortunately, practical use of siRNA containing LNPs is still hampered by difficulties, one of them directing LNPs toward specific cells. To improve cell-specific delivery, we have developed a new generation of palmitate-containing ionizable LNPs functionalized with two distinct ligands: i) a targeting peptide (octreotide, Oct), for selective recognition of somatostatin receptor 2 (SSTR2)-expressing tumor cells, and ii) a cell penetrating peptide (penetratin, RK16) to enhance intracellular delivery. This dually-decorated LNP was used to co-deliver two siRNAs targeting key mediators of drug resistance in HER2+ breast cancer –Hsp27 and HER2– demonstrating strong potential for combinatorial RNAi-based therapies. The Oct moiety conferred high selectivity toward malignant SSTR2-overexpresing (SSTR2OE) HER2+ BC cells, even in heterogeneous environments containing non-tumor epithelial cells. Simultaneously, the RK16 peptide facilitated enhanced intracellular delivery, resulting in improved antiproliferative activity and a notable reduction in the SSTR2-overexpressing cell population compared to non-functionalized LNPs. Taken together, the structural design and biological performance of this novel class of LNP formulation establish it as a versatile and innovative delivery platform for ON-based targeted therapies. By simply altering the targeting peptide moiety and siRNA combination, this dually-functionalized LNP system could be readily adapted for a broad range of tumors and combination treatment strategies. Finally, the inclusion of palmitic acid in the LNP composition selectively contributes to cytotoxicity in palmitate sensitive cell lines, such as SK-BR-3, offering an additional therapeutic advantage when targeting these tumor subtypes.