RNAi-based therapeutic approach for untreatable adenovirus infections

Human adenoviruses (HAdV) usually cause self-limiting infections, but can trigger life-threatening systemic infections and, in particular, liver inflammation in immunocompromised patients. To date, there is no approved antiviral therapy for the treatment of HAdV infections. RNA interference (RNAi) is a promising approach, but has so far failed due to the lack of stability of RNAi-inducing small interfering RNAs (siRNAs) and the lack of transfer systems with which the siRNAs can be transferred into the corresponding virus-infected target cells. The present invention specifically addresses these limitations by using highly efficient anti-adenoviral siRNAs with chemically modified nucleotides and a lipid nanoparticle (LNP) transfer system that enables the efficient transfer of siRNA into liver cells.

The siRNA directed against various HAdV serotypes contains several modifications of the nucleotides used. These include 2′-O-methyl modifications as well as phosphorothioate linkages, which were introduced at defined positions within the siRNA. These modifications increase the stability of the siRNA by inhibiting its degradation by endonucleases. For encapsulation of the siRNAs, lipid nanoparticles composed of a specifically formulated lipid mixture are employed, which facilitate preferential uptake of the particles by hepatocytes. Inhibition of adenoviral replication and therapeutic efficacy were demonstrated both in human cell lines and in immunosuppressed Syrian hamsters infected with HAdV. This resulted in a significant reduction in viral load in the liver, attenuation of virus-induced liver damage, and a decrease in HAdV titers in blood and spleen.