Targeted therapy of respiratory syncytial virus by 2-5A antisense

Respiratory syncytial virus is a leading cause of respiratory disease in infants, young children, immunocompromized patients, and the elderly. Previous work has shown that RNase L, an antiviral enzyme of the interferon system, can be recruited to cleave RSV genomic RNA by attaching tetrameric 2' 5'-linked oligoadenylates (2 5A) to an antisense oligonucleotide complementary to repetitive intergenic sequences within the RSV genome (2 5A antisense). RBI034, a 2'-O-methyl RNA-modified analogue of the 2 5A anti-RS V compound, was found to have enhanced antiviral activity in cell culture studies while also cleaving RSV genomic RNA in an RNase L- and sequence-specific manner. RBI034s efficacy in suppressing RSV replication in cell culture is 50 to 100 times better than ribavirin, the only approved drug for RSV infection. Here we show that the activity of 2 5A antisense compound can be further enhanced by a combination treatment with interferon or ribavirin. The anti-RSV activity resulting from combination treatment is more potent than either treatment alone. We also demonstrate that RBI034 is effective against RSV in three different species: mice, cotton rats, and African green monkeys.