Injectable hydrogel-mediated co-delivery of oncolytic adenovirus and melphalan for retinoblastoma control and vision preservation

Retinoblastoma (RB) is the most common primary ocular malignancy in children, arising from the developing retina. While higher doses of local chemotherapy have improved tumor control, concerns regarding retinal toxicity and the development of chemoresistance remain significant. Oncolytic adenovirus (OA) presents a promising therapeutic approach for RB, but rapid clearance often limits its therapeutic effects. In this study, we engineered a genetically modified OA derived from human adenovirus 5 (Ad5), designed to selectively target and lyse RB cells. The combination of OA with low-dose melphalan demonstrates an enhanced antitumor effect, while minimizing retinal toxicity. <i>In vitro</i> and <i>in vivo</i> experiments demonstrated that melphalan significantly enhanced the antitumor effect of OA and extended ocular survival. More importantly, we developed a biocompatible injectable hydrogel delivery system based on the covalent coupling of collagen and aldehyde-modified cyclodextrin, which effectively enhances the loading efficiency of melphalan and enables sustained co-delivery of OA and melphalan. The mouse RB tumor model confirmed that this hydrogel system (OA-Mel@CCA) achieved localized and sustained delivery of both therapeutics, effectively controlling tumor growth and preventing brain metastasis. Additionally, retinal structure and function were notably preserved in mice treated with OA-Mel@CCA, with no observed retinal toxicity. These findings suggest that the injectable hydrogel-based co-delivery of melphalan and oncolytic adenovirus could represent a promising strategy for RB treatment.