A newly developed vaccine to treat patients with metastatic HER2-positive cancers has been found effective, results from phase I clinical trial have shown.

HER2-positive breast cancer tests positive for a protein called human epidermal growth factor receptor 2 (HER2), which promotes the growth of cancer cells. Besides being more aggressive, these are also less likely to be sensitive to hormone therapy.

"We are using a vaccine approach to generate an immune response to HER2, which is found at high levels on and drives the growth of several types of cancer, including breast, ovarian, lung, colorectal, and gastroesophageal cancers," said Jay A. Berzofsky, from the US National Cancer Institute, a part of the National Institutes of Health in Maryland. 

The trial showed that among the 11 evaluable patients, those who received more than the lowest dose of the HER2-targeted therapeutic cancer vaccine, six (54 per cent) demonstrated clinical benefit. One patient with ovarian cancer had a complete response that lasted 89 weeks, one patient with gastroesophageal cancer had a partial response that lasted 16 weeks, and four patients (two with colon cancer, one with prostate cancer, and one with ovarian cancer) had stable disease.

"Our results suggest that we have a very promising vaccine for HER2-overexpressing cancers," Berzofsky said. "We hope that one day the vaccine will provide a new treatment option for patients with these cancers," he added. The vaccines were individually customised by the team using their own immune cells isolated from their blood. 

The vaccine, which is administered intradermally (between the layers of the skin), comprises patient-derived dendritic cells genetically modified with an adenovirus to produce parts of the HER2 protein. Preclinical studies showed that this type of vaccine could eradicate large, established tumours as well as lung metastases in mice.

In the trial, adverse reactions were predominantly injection-site reactions that did not require treatment. No cardiotoxicity was seen. The findings were presented at the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival in New York.