Positive results from PaxVax's Ad4-H5-Vtn vector vaccine Phase 1 trial on avian flu

PaxVax, Inc., which develops and commercializes innovative vaccines against infectious diseases in a socially responsible manner, today announced positive results in a Phase 1 clinical trial for its oral, replicating adenovirus serotype 4 (Ad4) vector vaccine for H5N1 (avian flu). The results have been published in the journal Lancet Infectious Diseases (published online January 29, 2013). The study was funded by The Wellcome Trust.

The goals of this Phase 1 study were to evaluate the safety and immunogenicity of the Ad4-H5-Vtn candidate vaccine, and, more generally, to evaluate the replication-competent Ad4 as an orally administered vector vaccine platform. The authors found the Ad4-H5-Vtn vector vaccine was well tolerated and induced cellular immune responses to the H5 HA. Subsequent boosting with a single dose of a licensed inactivated H5N1 vaccine led to high rates of seroprotection (HAI ≥ 40), significantly higher than in placebo recipients receiving a single dose of H5N1 vaccine (p<0.001).

"We are pleased to share these promising results from the first clinical trial of our oral Ad4 technology," said Marc Gurwith, M.D., Chief Medical Officer of PaxVax. "In addition to demonstrating initial proof of concept in H5N1, this study demonstrates the potential ability of an oral Ad4 vector-based vaccine as part of a prime/boost regimen to generate more robust antibody responses than traditional vaccine methodologies."

PaxVax's vaccine vector technology such as the Ad4-H5-Vtn vaccine is based on the existing licensed Adenovirus serotypes 4 and 7 (Ad4 and Ad7) vaccines, currently used by the U.S. Military. These Ad4 and Ad7 vaccines have a substantial safety experience having been administered to more than 10 million recruits without significant adverse experience.

Kenneth Kelley, Chief Executive Officer of PaxVax commented: "We are excited by these results in H5N1 and will continue to develop this vaccine to potentially add another option for defense against avian influenza pandemics. These Phase 1 results also provide support for the Ad4 (and Ad7) oral replicating virus vector approach. PaxVax will pursue other vaccine candidates for different disease targets using this technology."

To date, PaxVax has bioengineered dozens of vaccine candidates using the Ad4 and Ad7 vector technology. Under NIH supported programs, a number of different Ad4 vector vaccine candidates for HIV and for anthrax have advanced into additional pre-clinical development and animal studies, and are scheduled for Phase 1 clinical trials in 2013. Other vectors that have been constructed and are potential vaccine candidates for further development include Ad4 vectors expressing immunogens for herpes, influenza and rabies viruses. The company has filed for patents to protect the IP involved in developing these replication competent, oral vector vaccines.