A versatile self-amplifying mRNA system consolidates oncolytic virus benefits into a single flexible backbone for cancer therapy.

Oncolytic viruses (OVs) represent a promising cancer immunotherapy modality; however, their clinical translation is significantly impeded by manufacturing complexities, biosafety concerns, pre-existing neutralizing antibodies, and viral genome engineering constraints. Here, we introduce Self-Amplifying mRNA-based Virus-like Vesicles In Vivo Generation (SAMVIG), a versatile system enabling in vivo production of enveloped virus-like vesicles (VLVs). SAMVIG integrates an alphavirus RNA replicon, therapeutic payloads, and vesicular stomatitis virus glycoprotein within a single mRNA construct delivered via lipid nanoparticles. The system orchestrates multi-layered immune activation by combining dual antigen presentation, immune modulator co-expression, and VLV-mediated intercellular spread to elicit potent innate immune responses. This design leverages the advantages of mRNA technology and consolidates OV-like immunostimulatory functions while bypassing traditional OV constraints. Local and systemic administration of SAMVIG encoding tumor antigens significantly enhanced tumor-infiltrating lymphocyte recruitment and activation, resulting in robust antitumor efficacy across subcutaneous and metastatic tumor models. The modular architecture of SAMVIG facilitated seamless integration of checkpoint inhibitors (e.g., programmed cell death protein 1 [PD-1]/programmed cell death ligand 1 [PD-L1] inhibitor) and other functional proteins to substantially enhance therapeutic efficacy, without apparent payload length limitations. Coupled with its favorable safety profile observed in vivo, SAMVIG represents a versatile and customizable immunotherapy system that marks a paradigm shift in the field of oncolytic immunotherapy.