The systemic virotherapy strategy involves not only the direct delivery of therapeutic payloads encoded by viruses to tumors, but also the modification of the tumor microenvironment, aiming to target both primary and metastatic lesions. At the ongoing American Society of Clinical Oncology (ASCO) meeting, researchers from Calidi Biotherapeutics Inc. reported the development of a novel approach using a selected and engineered tumor-selective strain of vaccinia virus.