A modified herpes virus, RP1, is showing promise as a treatment for advanced melanoma. Clinical trials revealed that the virus shrank tumors in approximately one-third of patients with late-stage melanoma. If approved, this oncolytic virus could offer a new therapeutic avenue for individuals with limited treatment options. The treatment involves injecting the virus directly into the tumor, where it replicates and destroys cancer cells while also stimulating the immune system to attack the remaining cancer.