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Inovio Pharmaceuticals (AMEX:INO) reported Friday the positive long-term effects of its VGX-3100 vaccine, designed to treat cervical dysplasia and cancer caused by the human papillomavirus, or HPV.

In a follow-on study, the company’s SynCon DNA vaccine showed T-cell immune responses of up to over two years in 7 of 8 patients tested, following a fourth vaccination of VGX-3100. The vaccine was delivered using intramuscular electroportation.

The company said the data further highlights the viability of using multiple booster vaccinations with a DNA vaccine, which  are designed to provide broad cross-strain protection against a number of strains of pathogens.

Inovio’s VGX-3100 is designed to raise immune responses against the E6 and E7 oncogenes common to specific HPV types, which are responsible for transforming HPV-infected cells into pre-cancerous and cancerous cells. The goal is to stimulate a T-cell immune response strong enough to reject these infected or transformed cells from the body.

“Achieving long-lasting immune responses exceeding two years is exceptional,” said Inovio president and CEO, Dr. J. Joseph Kim.

“In general, the durability of these T cell responses places Inovio’s DNA vaccine technology on par with live virus vaccines, but without their various safety and other issues, and substantially exceeds current data from alternative non-replicating vaccine technologies.

“Furthermore, being able to use multiple vaccinations without safety concerns or unwanted immune responses is a notable advantage of Inovio’s DNA vaccine technology.”

Currently, there is no therapeutic live virus or non-replicating vaccine for cervical dysplasias, which are pre-cancerous lesions, and cancers in the market.

Inovio’s original phase one trial treated 18 women who had previously been diagnosed with and surgically treated for a pre-malignant lesion that may lead to cervical cancer, with a three-vaccination regimen of its VGX-3100.

In a longer-term analysis of T cell responses, at nine or more months after the initial vaccination, of 13 initially responding patients, 12, or 92%, had maintained significant T cell responses nine to 19 months after their first vaccination.

The company then decided to initiate the latest follow-on study, with the intent to assess the safety and immune responses following a fourth vaccination. Of the original 18 subjects, 11 T-cell responders and two non-responders agreed to participate, for a total of 13. Of the 13, only 8 have been analyzed thus far, Inovio said.

Based on the promising results, the vaccine developer is now recruiting for its phase two study, which is designed to enroll 148 patients with pre-cancerous cervical lesions, at around 25 centres in the US, Korea, South Africa, Australia and Canada.–Deborah Sterescu