A small, mid-stage study of Jennerex's genetically engineered virus offered some important preliminary proof-of-concept data on its ability to zero in on cancer cells with just a single infusion.  Reporting in Nature, investigators said biopsies confirmed the virus was replicating inside the tumors of 7 of the 8 people with metastatic cancers who were given the engineered dose, leaving healthy tissue untouched. Researchers noted several weeks after treatment the tumors in half of the group had stopped growing, indicating their cancers may have stabilized, and that in one case tumors appeared to shrink.

San Francisco-based Jennerex turned to the vaccinia virus for its raw material. Investigators then armed the virus, which is known to stealthily slip past the immune system, with a protein that launches an immune system attack on cancer cells, according to an article in MIT Technology Review. A second marker gene was used to track replication in samples.

"Our platform technology opens up the possibility of selectively expressing multiple transgene products with complementary mechanisms of action at high concentration in tumors systemically," says Jennerex CEO David Kirn. "This is a first in medical history. We believe it will take truly innovative, multi-mechanistic approaches to significantly prolong survival, and to potentially cure patients with metastatic solid tumors. JX-594, with its ability to reach tumors systemically after IV infusion, coupled with its three complementary mechanisms of action, represents a bold new approach to the treatment of metastatic cancers."

With such a small patient population, Jennerex is still a long way away from offering convincing efficacy data. But the early positive indications will help fuel a hot field in the cancer drug discovery side of the biotech business. If cancer-killing viruses continue to build up promising efficacy data, it will help attract a group of Big Pharma companies interested in capitalizing on a new generation of oncology drugs.

For Jennerex, which raised $8.6 million just days ago, the news sets the stage for a Phase IIb clinical trial of JX-594 that starts later in the year involving liver cancer patients who have failed to respond to Nexavar. Researchers have a number of big hurdles to overcome, including finding out whether the human body will adjust quickly to these viral approaches, potentially eliminating their effectiveness.