According to the World Health Organization (WHO), in a typical year, influenza infects 5 - 15 per cent of the world's population, resulting in 250,000 to 500,000 deaths.
The WHO and the Centers for Disease Control and Prevention are concerned about the potential for a major global pandemic.
Antiviral medications approved to treat influenza have the potential drawback that influenza virus strains can become resistant to one or more of these medications.
The potential advantage of RNAi antiviral therapeutics is that siRNA can be targeted against the conserved region of the influenza virus. This means that an RNAi therapeutic would be expected to be effective against all strains of the influenza virus, whether new or old.
Therefore stockpiling of an effective RNAi treatment is possible in advance of a global influenza pandemic. In addition to a potential role in a pandemic flu outbreak, RNAi therapeutics could serve as a treatment for the more common seasonal flu that as noted above can result in hospitalisation and death.
Results presented at the 8th International Symposium on Respiratory Viral Infections Conference revealed that by targeting the conserved regions of the influenza viral genome a siRNA therapeutic would be effective against strains of the influenza virus - essential in stockpiling a treatment for rapid mobilisation during an influenza pandemic.
In vitro screening results also identified highly potent siRNAs with IC50 values between 20 and 500 pM that were effective against representative human and avian influenza strains, including H5N1 avian influenza virus.
Furthermore, in vivo results demonstrate that direct-to-lung and intravenous administrations of selected proprietary formulations of siRNAs effectively inhibit influenza viral production in a preclinical model. A 200-fold reduction of viral concentration in the blood was observed.
"Nastech's goal is to rapidly develop a safe and effective treatment so that the medical community can be better prepared for an influenza pandemic, which has become an impending threat to worldwide public health," said Steven Quay, chairman, president and CEO of >Nastech.
"The results presented by Nastech demonstrate the effective inhibition of influenza virus production by a siRNA therapeutic," he added.
Vaccines currently represent the mainstay of flu prevention, but vaccines have two key limitations. First, they are developed against individual, known strains of flu and therefore may not be effective against new flu strains.
Second, vaccines are produced using a lengthy process requiring incubation in chicken eggs, thus vaccine against a new flu strain will take months or years to stockpile.
RNAi interference is a cellular mechanism that can be used to turn off the production of a protein. In the case of an RNAi directed against influenza, the target is one or more proteins critical for viral replication.
By turning off the production of such proteins, the spread of infection is prevented or slowed.
Nastech's RNAi research and development programs seek to develop safe and effective therapeutics by identifying key protein targets, designing the siRNA that will turn off the production of the targeted proteins, and developing a formulation for the systemic delivery of this potential new class of therapeutics.