Anti‐HER2 Immunoliposomes: Antitumor Efficacy Attributable to Targeted Delivery of Anthraquinone‐Fused Enediyne

Abstract Although natural products are essential sources of small‐molecule antitumor drugs, some can exert substantial toxicities, limiting their clinical utility. Anthraquinone‐fused enediyne natural products are remarkably potent antitumor drug candidates, and uncialamycin and tiancimycin (TNM) A are under development as antibody‐drug conjugates. Herein, a novel drug delivery system is introduced for TNM A using anti‐human epidermal growth factor receptor 2 (HER2) immunoliposomes (ILs). Trastuzumab‐coated TNM A‐loaded ILs (HER2‐TNM A‐ILs) is engineered with an average particle size of 182.8 ± 2.1 nm and a zeta potential of 1.75 ± 0.12 mV. Compared with liposomes lacking trastuzumab, HER2‐TNM A‐ILs exhibited selective toxicity against HER2‐positive KPL‐4 and SKBR3 cells. Coumarin‐6, a fluorescent TNM A surrogate, is encapsulated within anti‐HER2 ILs; the resultant ILs have enhanced cellular uptake in KPL‐4 and SKBR3 cells when compared with control liposomes. Furthermore, ILs loaded with more Cy5.5 accumulated in KPL‐4 mouse tumors. A single HER2‐TNM A‐IL dose (0.02 mg kg −1 ) suppressed the growth of HER2‐positive KPL‐4 mouse tumors without apparent toxicity. This study not only provides a straightforward method for the effective delivery of TNM A against HER2‐positive breast tumors but also underscores the potential of IL‐based drug delivery systems when employing highly potent cytotoxins as payloads.