FORMULATION DEVELOPMENT OF siRNAs FOR DRUG DELIVERY: A NEW THERAPEUTIC APPROACH FOR PANDEMIC INFLUENZA.

This study by scientists at Nastech Pharmaceuticals demonstrated how MatTek’s EpiAirway human tracheal/bronchial tissue equivalent can be used to identify lipids that facilitate siRNA uptake in lung tissue. This was part of a program to develop siRNA-based therapeutics designed for direct-to-lung delivery to treat humans infected with H5N1 Pandemic (Bird) Flu. The risk of an H5N1 Pandemic Flu outbreak is significant. New therapies to treat Influenza A viral infections are urgently needed. Short interfering RNAs (siRNAs), targeting the conserved regions of influenza viral genes, have been shown to reduce viral replication in vitro and in vivo. To provide an effective prophylactic and therapeutic treatment for pandemic flu, researchers at Nastech Pharmaceutical Co. are developing peptide and lipid formulations to efficiently deliver siRNAs to lung tissue. This involves studies on the biodistribution and cellular uptake of fluorescently labeled siRNA formulations in the mouse lung and evaluating their efficacy for knock-down of influenza viral replication. Lipids were identified that facilitate siRNA uptake in vitro using EpiAirway primary human respiratory epithelial tissue. Direct-to-lung administration of selected siRNAs reduced virus production in mice by 10-fold and with appropriate formulation by 200-fold. Optimal, stable siRNA formulations for lung delivery will permit use of lower doses, reduced dosing frequency, and a longer duration of effect, thus providing a viable therapeutic approach to treat pandemic flu. Study Findings: • Eight lead siRNAs were identified, four of which are effective against all known human and avian influenza isolates and the other four of which are effective against 99.5% of all known human and avian influenza isolates. • Lipids were identified that facilitate siRNA uptake in vitro in primary human respiratory epithelial tissue. This class of lipids is unique for siRNA uptake: – Allows penetration through mucus layer – Promotes siRNA delivery apically as well as deeper tissue penetration – Other commercially available transfection competent lipids don’t promote siRNA uptake in this tissue model • siRNAs formulated with specific peptides localize to lung tissue in vivo. • Intranasal and intravenous delivery of lipid formulated siRNAs demonstrated in vivo inhibition of viral production.

Avian flu, Bird flu, Direct to lung administration, EpiAirway, Glycoprotiens, H5N1, Hemagluttin assay, Human bronchial epithelial tissue, Influenza viral replication, Intranasal delivery, Lipid formulation, Lung tissue, Mucus layer, Nucleotides, Pandemic influenza, RNA interference, RNAi, Short interfering RNA, siRNA, siRNAs

Cy5-siRNA, Lipis formulation siRNA, Peptide formulation siRNA