Inovio Pharmaceuticals, a developer of therapeutic and preventive vaccines against cancers and infectious diseases, announced that significant T cell and antibody responses were generated in its phase I clinical study of VGX-3400X, a SynCon DNA vaccine for the prevention of avian H5N1 influenza delivered using intramuscular (IM) electroporation.

Inovio has launched a second phase I clinical study as part of its universal influenza vaccine program. This trial will assess a multi-subtype SynCon vaccine for H1N1 and H5N1 influenza using its skin-targeted intradermal (ID) electroporator. Inovio's SynCon vaccine design process uses a proprietary method to achieve cross-strain protection against the natural and frequent mutations of influenza strains within subtypes.

Inovio's VGX-3400X targets the pandemic influenza subtype H5N1. The vaccine consists of three distinct DNA plasmids coded for a consensus hemagglutinin (HA) antigen derived from different H5N1 virus strains; a consensus neuraminidase (NA) antigen derived from different N1 sequences; and a consensus nucleoprotein (NP) fused to a small portion of the m2 protein (m2E) based on a broader cross-section of influenza viruses in addition to H5N1 and H1N1.

In this first proof-of-principle study of Inovio's universal flu vaccine program, VGX-3400X was delivered with IM electroporation using Inovio's CELLECTRAR electroporation device. The primary objectives of this clinical trial were to assess safety and tolerability. The secondary objective was the measurement of antigen-specific T cell and antibody responses, including binding and hemagglutination inhibition (HI) responses.

The study assessed a total of 60 healthy volunteers, 30 in the U.S. and 30 in Korea (in a separate, parallel clinical trial sponsored by Inovio affiliate VGX International). Three dose cohorts of 10 subjects were each given two injections of 0.2mg, 0.67mg, or 2.0mg of each plasmid at months 0 and 1.

VGX-3400X was found to be generally safe and well tolerated at all dose levels. There were no vaccine-related serious adverse events. Reported adverse events and injection site reactions were mild to moderate and required no treatment.

Inovio tested for antibody responses against the target antigens and observed high levels of binding antibodies in 26 of 27 evaluated subjects (96%). Antibodies were generated against all three antigens, as tested by the enzyme-linked immunosorbent assay (ELISA). Positive antibody responses persisted to seven months, the latest time point tested.

In testing for HI responses against the Vietnam (A/H5N1/1203/04) strain, three of 27 subjects (11%) showed HI titers greater than 1:40, which is considered to be an indicator of protection against influenza in humans. Two of the three subjects with HI titers exceeding 1:40 against the Vietnam strain also demonstrated greater than 1:40 titers against the Indonesia (A/H5N1/5/2005) strain, demonstrating cross-reactive responses in these volunteers.

Antigen-specific cytotoxic T-lymphocyte (CTL) responses were also observed against all three antigens (HA, NA and NP). After two vaccinations, 13 of 18 vaccinated subjects from the first two cohorts developed strong CTL responses to at least one of the vaccine components. Cohort 3 samples have not yet been analyzed. These positive T cell responses were measured up to seven months after the first vaccination. Generation of influenza antigen-specific T cell responses is believed to be important for generating universal, long-lasting immunity against influenza as well as to generate a stronger immune response against flu in elderly people.

Inovio has since initiated a booster study in which U.S. study participants were vaccinated with a booster dose of 0.9 mg of just the H5 HA SynCon DNA vaccine component delivered with Inovio's new intradermal electroporation delivery technology.

This is the first flu study of ID electroporation delivery in humans. ID electroporation is focused on delivering a DNA vaccine into skin, which contains large amounts of immune cells such as dendritic cells and macrophages. Inovio's skin electroporation device includes a patented design that introduces a miniaturized array, which delivers the electrical pulses into the skin, and uniquely optimized electroporation conditions. A recent controlled study conducted in human volunteers showed that tolerability of this device was similar to conventional syringe-delivered vaccines. Inovio believes these important design outcomes could make such devices suitable for widely applicable preventive vaccine regimens against infectious diseases such as influenza, dengue and malaria.

The goal of the booster study is to determine if ID vaccination with the monovalent H5HA construct can increase HI titers. Of the 27 available subjects, 18 have already received the ID booster vaccination. Safety and immune response data are expected in the fourth quarter of 2011.

Inovio is advancing its universal influenza vaccine strategy with the initiation of a second phase I influenza vaccine study. This trial is assessing INO-3510, Inovio's multi-subtype SynCon DNA vaccine consisting of the H5N1 and H1N1 subtypes delivered exclusively with its new ID electroporator.

This phase I introduces three strategic components for its universal influenza program, which is funded in part by a recent grant from the National Institutes of Health. First, this vaccine adds the H1N1 seasonal/pandemic influenza subtype to the H5N1 pandemic subtype. Second, it will be Inovio's first clinical study solely using ID electroporation delivery. Third, this study will test the SynCon vaccine's ability to provide cross-strain protection against H1N1 and H5N1 viruses.

In this study, 90 subjects will receive two or three doses of the DNA vaccines over one to six months. The Investigational New Drug submission for this study has been approved by the FDA and all 90 subjects are currently being screened and randomized. Preliminary safety and immune response data are expected in the first quarter of 2012.