Direct Surface Engineering of Oncolytic Adenovirus with Targeted Antibody and Chemotherapeutics for HER2-Targeted Chemo-Virotherapy

Background/Objectives: Systemic delivery of oncolytic adenovirus (oAd) remains a major challenge due to rapid immune clearance, hepatic sequestration, and off-target toxicity. To overcome these barriers and enhance tumor-targeting efficacy, we developed Ad-DTX/HER, a novel viral complex engineered by directly co-conjugating the cytotoxic agent docetaxel (DTX) and the site-specifically modified HER2-targeting antibody trastuzumab (Herceptin, HER) onto the oAd surface. Methods: DTX and trastuzumab were site-specifically conjugated onto the naked viral capsid in a polymer-free manner, and the resulting Ad-DTX/HER complex was characterized for size distribution and structural integrity. Its HER2 selectivity and oncolytic activity were evaluated in cancer cells, and its biodistribution and organ toxicity were assessed following systemic administration in tumor-bearing mice. Results: Ad-DTX/HER exhibited a uniform size distribution, sustained structural integrity, and remarkable selectivity toward HER2-overexpressing cancer cells without compromising viral oncolytic activity. Systemic administration in tumor-bearing mice drastically minimized non-specific hepatic uptake while significantly enhancing tumor accumulation, achieving a marked ~2800-fold increase in the tumor-to-liver ratio compared to naked oAd. Histopathological analysis of major organs indicated that systemic administration of Ad-DTX/HER is not associated with overt off-target organ toxicity. Conclusions: This polymer-free, direct capsid-engineering platform provides an effective systemic delivery paradigm, offering potent synergistic chemo-virotherapy for HER2-positive tumor.