Anti-epidermal growth factor receptor (EGFR) and anti-human epidermal growth receptor 2 (HER2)-immunoliposome formulations substantially boosted topotecan internalization compared to the non-targeted counterparts and free topotecan, resulting in enhanced cytotoxic activity and superior antitumor efficacy against HER2-overexpressing human breast cancer (BT474) xenografts. Here, ERBB2 is linked to breast cancer.