(Reuters) - Nearly a third of patients with advanced liver cancer who received a personalized vaccine developed by Geneos Therapeutics along with an immunotherapy drug in a small, early trial saw their tumors shrink, U.S. researchers reported on Sunday.
The result was roughly twice the response typically seen with the immunotherapy alone, the researchers said.
Findings from the preliminary study, presented at the American Association for Cancer Research in San Diego and published in Nature Medicine, suggests that vaccines based on mutations only present in a patient's tumor may boost the immune system's ability to recognize and attack hard-to-treat cancers.
The findings, which must be confirmed in a larger trial, moves the industry another step closer to effective cancer vaccines, after many past failures, and may expand the types of cancers that such therapies can treat.
Partners Moderna and Merck and Co and others have had promising results combining customized vaccines with immunotherapy to prevent skin cancer from returning in patients following surgery.
For the study, researchers used samples from patients' tumors to build vaccines based on neoantigens - new mutations only present on an individual patient's tumor. The goal was to train the immune system to attack and kill only these unique proteins, leaving healthy tissue unscathed.
Unlike skin cancer, which has many mutations for the body to recognize, liver cancer is considered a cold cancer because it contains fewer mutations, which has rendered immunotherapies less effective.
"This vaccine essentially educates the immune system to recognize antigens that it's ignored," said study leader Dr. Mark Yarchoan of Johns Hopkins Kimmel Cancer Center.
The study involved 36 patients with hepatocellular carcinoma, the most common form of liver cancer. Patients were given custom-made vaccines on top of Merck's widely used immunotherapy Keytruda, the standard of care at the time.
Nearly a third of the patients treated with the combination therapy (30.1%) experienced tumor shrinkage, with three of those subjects having a complete response, meaning no detectable signs of the tumor remaining after a median follow-up of 21.5 months.
That compares with the typical response of about 12% to 18% in patients with liver cancer who receive immunotherapy alone.
"This certainly suggested that the vaccine actually added clinical efficacy," Yarchoan said.
The most common adverse effect was mild injection site reactions. There were no serious adverse events.
Unlike many vaccine candidates based on messenger RNA (mRNA) technology, the Geneos treatment is a DNA vaccine in which the genetic code of the mutated proteins is injected into cells using a small electrical impulse. Each vaccine can target up to 40 mutated genes.
Yarchoan said larger trials are being planned, but declined to provide details.
(Reporting by Julie Steenhuysen; Editing by Bill Berkrot)
