Developing an antibody drug encapsulation nanoagent targeting HER2 for cancer treatment

Human epidermal growth factor receptor 2 (HER2) is overexpressed in 15–20% of breast cancer and some other cancers. Trastuzumab (Tr)-based antibody drug conjugates (ADCs) have emerged as a new class of anti-HER2 therapies. However, traditional ADCs face challenges including limited in vivo stability, inefficient drug release, and manufacturing complexities. We developed Tr-ACT2, a first-in-class antibody drug encapsulation nanoagent, using single protein encapsulation technology. Tr-ACT2 was characterized by UV absorbance/fluorescence emission spectroscopy, membrane dialysis, particle size distribution, and molecular docking studies. In vitro cellular uptake and cytotoxicity were evaluated in breast and lung cancer cell lines using cell viability assays, western blotting, apoptosis assays, and immunofluorescence. In vivo toxicity was assessed using the A549 xenograft mouse model treated with Tr-ACT2 or irinotecan. As a potential antibody-encapsulated drug (AED), Tr-ACT2 features each Tr protein encapsulating two actinomycin D (ACT) molecules without chemical conjugation and linkers. Tr-ACT2 exhibited time-dependent internalization into breast and lung cancer cells with various HER2 expression levels. It led to inhibition of cell growth, induction of apoptosis, and reduction of Akt activation. Notably, Tr-ACT2’s cytotoxic activity appeared to be independent of HER2 expression levels. In a human lung cancer xenograft mouse model, intravenous administration of Tr-ACT2 demonstrated a significant anticancer therapeutic efficacy. These findings support further evaluation of Tr-ACT2 for the treatment of human cancers. The AED approach may be broadly applicable to other antibodies and chemotherapeutic agents, potentially opening a new avenue for developing targeted anticancer therapies.