A genetically modified smallpox vaccine shrunk tumors in liver cancer patients and extended survival more than a year, a study found.
 

The therapy from closely held Jennerex Inc., called JX-594, or Pexa-Vec, is being tested in people with advanced hepatocellular carcinoma. The 16 patients who received a high dose of the medicine lived a median 14.1 months after injection, compared with 6.7 months for 14 patients on a low dose, according to the study published Sunday by the journal Nature Medicine.
 

“The treatment options for advanced HCC are limited, with few promising agents currently in development,” Tony Reid, a professor at the University of California, San Diego, and co-lead author of the paper, said in a statement. The study“highlights the unique possibility of a meaningful survival benefit combined with short-term, transient, and manageable side effects.”
 

Hepatocellular carcinoma is a cancer that forms in the tissues of the liver and can spread to other parts of the body. The disease was diagnosed in 28,720 people in the U.S. last year, and 20,550 people died from the illness, according to the National Cancer Institute.

In the study published Sunday, patients received the medicine three times during a four-week period. About 35 percent of those in the high-dose group were alive 18 months later, the study said. The current five-year survival rate for liver patients is about 15 percent, according to the American Cancer Society.

San Francisco-based Jennerex is competing with companies including Amgen Inc., Oncolytics Biotech Inc., PsiOxus Therapeutics Ltd., and Transgene SA to develop vaccines using oncolytic tumor viruses, pathogens that infect and destroy cancer cells. The approach may enhance the tumor-fighting effects of standard treatments such as chemotherapy and radiation or work alone.
 

Researchers studying Jennerex’s therapy used the same strain of virus that’s used in the smallpox vaccine, called vaccinia virus, because of its natural ability to replicate in cancer cells. They modified the virus to enhance its cancer-fighting properties.
 

The approach differs from so-called cancer vaccines, such as Merck & Co.’s Gardasil shot that targets a virus that causes cervical cancer or Dendreon Corp.’s Provenge, which stimulates an immune response against prostate cancer cells.
 

While vaccinia virus is similar to smallpox, it doesn’t contain smallpox and can’t cause the disease, according to theU.S. Centers for Disease Control and Prevention.
 

The company’s name is based on Edward Jenner, an 18th century English scientist who developed the first vaccination with an inoculation against the related cow-pox virus.