H5N1 Pandemic Influenza - Vaccine Candidate

• Disease Overview
• Prevalence and Current Treatment
• Product Candidate Description
• Broadly H5-specific cross-protective pre-pandemic vaccine
• Broadly H5-specific cross-reactive monoclonal antibodies
• Announcements

Disease Overview

According to the World Health Organization (WHO), influenza A virus subtype H5N1, also known as "bird flu", or simply H5N1, is a subtype of the Influenza A virus which can cause fatal illness in humans and many other animal species. A bird-adapted strain of H5N1, called HPAI A(H5N1) for "highly pathogenic avian influenza virus of type A of subtype H5N1," is the causative agent of H5N1 flu, commonly known as "avian influenza" or "bird flu." H5N1 has the ability to “jump” from bird to humans and there have been cases suggesting limited human-to-human transmission. Currently transmission from birds to humans is low in frequency, however H5N1 may mutate or re-assort into a strain capable of highly efficient human-to-human transmission that could potentially enable H5N1 to spread globally, thereby causing a pandemic. Around 60 percent of humans known to have been infected with the current Asian strain of H5N1 have died from it. Due to the high lethality of H5N1, its increasing pathogenicity and increasing host reservoir, the WHO and many other global health bodies consider, this virus to be one of the world's largest current pandemic threats.

Prevalence and Current Treatment

H5N1 is prevalent predominantly in South East Asia, but recent outbreaks were reported in Egypt and other parts of the world. Influenza viruses are typically transmitted from person to person through contact with infected airborne droplets generated by coughing and sneezing, and once robust human-to-human transmission occurs a global pandemic is possible. Influenza vaccines are potentially the most efficacious means of mitigating the impact of an influenza pandemic by helping to contain an emerging pandemic virus.

There is no highly effective treatment for H5N1. Antiviral drugs like oseltamivir (commercially marketed by Roche as Tamiflu^®), and zanamivir (commercially marketed by GlaxoSmithKline as Relenza^®) can sometimes inhibit the influenza virus from spreading and reduce the duration of influenza like symptoms. Many governments stockpile these drugs as part of a pandemic preparedness strategy.

Both drugs have been shown to be active against certain strains of influenza, but resistance to strains of H5N1 has been reported.

Product Candidate Description

EPIC Bio, a joint venture between Emergent and Temasek Life Sciences, is currently addressing the limitations of timely vaccine supply and potentially ineffective antiviral treatments by developing two different products:
1) A broadly cross-protective H5N1 vaccine based on Emergent’s MVAtor™ (viral vaccine vector) platform to prevent disease, and
2) H5-specific monoclonal antibodies to treat disease in people infected with H5N1.

Broadly H5-specific cross-protective pre-pandemic vaccine

A limitation of today’s influenza vaccines is that they are strain-specific and need to be adapted to a currently circulating strain. In the case of an H5N1 pandemic, it is estimated it would take up to six months to produce a strain-specific vaccine. EPIC Bio is developing a recombinant H5 viral vaccine that, if successful, may provide protection against multiple H5 clades. Epitopes on the H5 HA that cover all H5 avian influenza clades have been identified. We believe that presentation of these antigens using a live, attenuated viral delivery system such as Modified Vaccinia Ankara (MVA) may induce broad protective immune responses.

Broadly H5-specific cross-reactive monoclonal antibodies

Conserved epitopes in the HA sialic acid binding site that are conserved across all H5 clades have been identified. Monoclonal antibodies recognizing these epitopes have demonstrated the ability to treat and protect H5N1-infected mice, when treated 1 or 3 days post viral challenge. Antibody candidates will be selected to develop a treatment for those infected with H5N1 virus at risk for serious complications of influenza disease.

Tamiflu and Relenza are trademarks of their respective companies.

Announcements