In Vivo Tracking Modalities for Oncolytic Reovirus: Principles, Clinical Applications, and Translational Integration

Oncolytic reovirus, particularly Pelareorep, is a promising cancer therapeutic due to selective replication in Ras-activated tumor cells and immunomodulatory effects. This review aims to critically evaluate current and emerging in vivo tracking strategies, emphasizing translational relevance and clinical implementation.

We systematically analyzed preclinical and clinical studies employing optical imaging, nuclear imaging, magnetic resonance imaging, ultrasound/photoacoustic techniques, molecular reporters, and nanoparticle-based platforms. Special focus was placed on integrating functional imaging and molecular assays in Pelareorep trials to monitor viral distribution and therapeutic response.

Optical imaging offers high sensitivity for preclinical investigations; however, it is limited by shallow tissue penetration. Nuclear imaging provides quantitative, whole-body monitoring that is suitable for clinical translation, whereas MRI and ultrasound/photoacoustic modalities enable real-time visualization of both structural and functional aspects. Nanotechnology-based platforms facilitate multimodal imaging and targeted delivery, while molecular tools such as reporter genes, CRISPR-driven circuits, and viral barcoding further enhance spatiotemporal resolution. Clinical trials with Pelareorep demonstrate the feasibility of integrating imaging with molecular assays to evaluate safety, delivery efficiency, and antitumor activity. Persisting challenges include limited genome capacity, immune-mediated clearance, and suboptimal signal penetration.

Emerging strategies, including synthetic biology reporters, AI-driven image analysis, biosensors, and liquid biopsies, provide scalable, patient-specific tracking solutions. This integrative framework bridges preclinical insights with clinical translation, supporting optimized design, monitoring, and personalization of oncolytic reovirus therapy.