In current clinical trials, viruses engineered to target cancer cells must be delivered directly into tumors. But David Kirn, CEO of Jennerex, Inc., says that to become broadly useful as cancer treatments, they must be given systemically with an IV—allowing them to reach even metastatic tumors. Jennerex recently announced a major step toward that goal, demonstrating that an oncolytic virus delivered intravenously can selectively target and replicate in metastatic solid tumors in humans, and deliver multiple transgenes to the tumor tissue (Nature 2011;477:99–102).

The therapy, called JX-594, is an oncolytic poxvirus derived from a vaccinia vaccine. The treatment is designed to seek and destroy cancer cells, as well as stimulate an immune response against them. It has been altered to replicate selectively in cancer cells and carries two transgenes: one encoding a protein that stimulates the immune system, and another that serves as a marker for detecting viral activity.

In a phase I dose-escalation trial in 23 patients with advanced metastatic solid tumors that had failed other treatments, biopsies taken several days after treatment demonstrated that 87% of patients were positive for JX-594 when given at higher doses. The results add to previous trials demonstrating the efficacy of the therapy when injected directly into tumors.

The company is now involved in a phase II trial in patients with end-stage liver cancer. The next big question is whether the drug will remain effective over time when given systemically.