Researchers have developed a more advanced version of an oncolytic vaccinia virus, designed to safely target and kill cancer cells while sparing healthy tissue. Although this type of “living drug” has shown promise, earlier versions faced key challenges, including safety concerns from uncontrolled viral spread, risk of infecting others through skin lesions, and difficulty tracking the virus inside the body.
To solve these issues, scientists engineered the virus with a powerful built-in “off-switch” using a modified enzyme called HSV-TK.007. This allows doctors to stop the virus at any time by giving the antiviral drug ganciclovir, which is converted into a toxic compound that kills the virus. The same approach can also be applied topically to treat skin lesions and prevent viral shedding. In addition, the modified virus can be tracked using PET scans, enabling doctors to see exactly where it travels in the body without invasive procedures.
In preclinical studies, the engineered virus showed strong tumor selectivity, effectively targeting cancer cells while avoiding normal cells, and even improved production efficiency. Researchers also enhanced its cancer-fighting ability by adding a safer version of an immune-boosting protein. Now in early clinical trials, this next-generation virus could mark a major step forward in making oncolytic virus therapies safer, more controllable, and more effective for patients with solid tumors.