In a small, preliminary study, an experimental vaccine provoked a strong immune response against precancerous cells in women treated for cervical lesions that can progress to cancer.

Most cases of cervical cancer are caused by infection with two types of human papillomavirus, or HPV. Some women who have precancerous cervical lesions associated with the Type 16 and Type 18 strains of HPV are able to fight them off without medical intervention. They do so by producing high levels of immune cells called killer T-cells.

The experimental drug, called VGX-3100, is a therapeutic vaccine using synthetic DNA that is intended to work in patients who have abnormal precancerous changes in the cervix. It is not related to preventive vaccines meant to protect against infection with HPV. The experimental vaccine attempts to harness the human immune system to fight disease: Similar to gene therapy, the drug inserts a piece of DNA into a patient’s cells to produce a protein that primes the immune system to attack HPV-altered cells.

“Our immune system is capable of protecting us from millions of pathogens,” said J. Joseph Kim, president and chief executive of Inovio Pharmaceuticals, maker of the experimental vaccine. “We want to use the existing hardware in our immune system, but use better software to train our immune system to fight off disease.”