Inovio Pharmaceuticals, a developer of therapeutic and preventive vaccines against cancers and infectious diseases, has reported data demonstrating long-term durability of immune responses induced by VGX-3100, its investigational DNA vaccine for treating cervical dysplasia and cancer caused by human papillomavirus (HPV).
In this study, 72% of vaccinated subjects (13 of 18) developed significant antigen-specific T-cell responses during the first four months of treatment (each patient was vaccinated at months 0, 1, and 3) by standardized interferon-g ELISpot assay. The third and highest dose group displayed the strongest level of T cell responses, with 83% (5 of 6) positive responders. The level of T cell responses in positive responders ranged from 100 to over 5000 spot forming units (SFU) per million cells when measured after overnight stimulation in the standardized ELISpot assay. In contrast, competing vaccine approaches targeting HPV therapy have consistently shown sub-100 SFU levels even when using more sensitive assays.
This newly reported data evaluated 11 of 13 positive responders as well as 3 of 5 patients who were non-responders at month 4. These patients were subsequently monitored through to study completion at month 9 (six months post last vaccination). As expected, all three non-responders at month 4 still did not show a T cell response at month 9. In contrast, 91% of evaluated patients (10 of 11) displayed strong and persistent memory T-cell responses at month 9. Importantly, the level of T cell responses remained strong, with responses ranging from 100 to over 3800 SFU. These results are consistent and add validation to similar levels of persistent and strong T cell responses at month 9 observed by Inovio from its PENNVAX HIV vaccine studies in non-human primates.