Joseph Kim Achieves Antibody Response from DNA Flu Vaccine

Joseph Kim's Inovio has taken an important step toward developing a universal DNA-based flu vaccine.

Significant T cell and antibody responses were generated in a Phase I clinical study of Inovio Pharmaceutical’s SynCon DNA vaccine for the prevention of avian H5N1 influenza.

“We are encouraged by the immune responses generated in this proof-of-principle study of our first SynCon influenza vaccine, VGX-3400X, delivered using intramuscular electroporation,” said Dr. J. Joseph Kim, Inovio’s president and CEO.
“The second Phase I study (INO-3510) builds on our universal influenza vaccine development program by adding a second component targeting the H1N1 subtype and delivering vaccine formulations using our minimally invasive intradermal electroporation delivery system, which is designed to directly access the skin tissue that is most ideal for inducing preventive antibody responses.”

These results were presented Thursday at DNA Vaccines 2011, hosted in San Diego by the International Society of DNA Vaccines.

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 CELLECTRA® 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 US 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 0.2 mg, 0.67 mg, or 2.0 mg of each plasmid at months 0 and 1.

In the study, 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, 3 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.

Significantly, 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 (72%) 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 previously reported the generation of strong, long-lasting and best-in-class T-cell responses in Phase I studies of both VGX-3100 for cervical cancer/dysplasia and PENNVAX™-B for HIV via IM electroporation delivery of Inovio SynCon™ DNA vaccines.

Of three broad types of influenza (A, B, C), influenza A is the most deadly and the causative agent of pandemics. Two of the eight proteins associated with influenza A are HA (hemagglutinin) and NA (neuraminidase). H1, H2, and H3 are the HAs and N1 and N2 are the NAs that have caused the majority of disease in man, with the specific combinations of concern to man being H1N1, H2N2, and H3N2. H5N1 is pathogenic and quite lethal but has not been shown to transmit from person to person.

The challenge to the development of effective vaccines against these influenza subtypes is that, within subtypes, there are hundreds or thousands of strains that may vary slightly and which naturally and frequently mutate to create new strains. Today’s vaccines only provide protection by matching the virus strain of concern, and are often unable to provide protection because they do not match the strain that becomes prolific during the next flu season. Moreover, subtypes can “reassort” – for example, a current concern is that a strain of H5N1, which is very deadly but does not currently pass from person to person, may combine with a strain of H1N1 or other subtype that does pass from person to person.

Inovio’s novel approach is to synthetically create consensus gene sequences derived from the HA antigens of multiple existing virus strains within a targeted influenza subtype. This results in patentable DNA vaccine constructs encoded to produce antigens that do not match any one existing strain but have been shown in multiple animal studies to protect against unmatched known and newly emergent strains (e.g. the 2009 swine-origin H1N1 virus). While providing cross-strain protection within each subtype, creating and combining multiple DNA vaccine constructs for different subtypes expands Inovio’s vision for a truly universal influenza vaccine capable of providing broad protection against yearly seasonal influenza and the less frequent but inevitable virulent strains that rise to pandemic status.

In addition to creating SynCon vaccines based on HA and NA antigens, which are the proteins that evolve most frequently, Inovio has also created SynCon constructs for the NP and m2E proteins, which mutate much less frequently and are more conserved across different strains, adding additional antigenic targets to broaden the potential protective capability of its influenza vaccines.

Inovio has established a modular development plan for systematically combining vaccine components targeting the influenza A H1N1, H5N1, H3N2, H2N2 subtypes as well as influenza B with the goal of developing a universal influenza vaccine.

Inovio clinical programs include three Phase II studies for vaccines treating cervical dysplasia/cancer, hepatitis C virus, and leukemia. Other clinical programs target influenza (preventive) and HIV (preventive and therapeutic).

“If we’re successful [with the universal flu vaccine] you don’t have to take it every year,” Kim noted.

Kim became CEO of Inovio after it merged with VGX Pharmaceuticals which he co-founded in December of 2000 to develop DNA vaccines based on technology licensed from the University of Pennsylvania.

In 2009 Inovio successfully showd that its DNA flu vaccine provides a complete protective effect against the current strain of H1N1 (swine flu) in pigs, which have immune systems similar to humans, as well as mice. The firm has also shown that the same vaccine is equally effective against several other major strains and hopes to begin clinical trials soon.

Inovio is also applying the same technologies to create vaccines for HIV and various types of cancer. Inovio is a key partner in a phase II clinical trial of a Hepatitis C DNA vaccine being developed by ChronTech Pharma which began March 13.

DNA vaccines — also known as third-generation vaccines — avoid the problems that can arise with whole-organism vaccines that use attenuated (weakened) live or killed forms of pathogens. Attenuated vaccines pose the risk of pathogens reverting to dangerous form and causing disease in immunocompromised patients. Killed vaccines, on the other hand, are not capable of eliciting killer T-cell responses, making them useless to people who have already been infected.

DNA vaccines use genetically engineered slices of DNA that, when injected into cells, trigger production of one or two key proteins of a pathogen. Those proteins, or antigens, are recognized as foreign and elicit a full range of desired immune responses, including production of killer T cells to destroy and dispose of infected and damaged cells. This allows such vaccines to be used as therapy for those who are already infected, as well as inoculation for those who aren’t.

One of the major problems of delivering vaccines via a saline injection is the problem of uptake — being absorbed through the outer cell membrane. To address this problem Inovio uses electroporation techniques. Immediately upon injection of the saline solution containing the DNA vaccine, a milisecond pulse of electricity is fired through the syringe needles. This creates many small pores to form on the cell membranes, allowing 1,000 times as much vaccine to be absorbed. The pores gradually close back up within days or weeks, after the vaccine has been absorbed.

Before starting VGX Kim led efforts in manufacturing and process development of several FDA-approved products and developmental therapeutics at Merck & Co. These products include FDA-approved vaccines for hepatitis as well as developmental vaccines and therapeutics for HIV/AIDS. Kim has published over 70 peer-reviewed scientific papers and book chapters, holds numerous patents and sits on several editorial boards and review panels.

J. Joseph Kim has a BS in chemical engineering and economics from MIT, where he was a U.S. Senate Honors Scholar. He holds a PhD in biochemical engineering from the University of Pennsylvania and an MBA in Finance from the Wharton School.

Kim’s many honors includes being named one of the world’s Top 100 Young Innovators by MIT’s Technology Review in 2002. In 2003 and 2006 he was named one of the “50 Most Influential Men” by Details Magazine. In 2004 the World Economic Forum selected Kim and VGX Pharmaceuticals as one of 30 Technology Pioneers. In 2005 Newsweek International profiled him as one of the 10 leaders, scientists and executives at the forefront of global change.