Organic compounds to treat hepatitis b virus

The disclosure relates to compositions comprising a HBV RNAi agent. In some embodiments, the HBV RNAi agent comprises a sense and an anti-sense strand, each strand being an 18-mer and the strands together forming a blunt-ended duplex, wherein the 3' end of at least one strand terminates in a phosphate or modified internucleoside linker and further comprises, in 5' to 3' order: a spacer; a second phosphate or modified internucleoside linker; and a 3' end cap. In some embodiments, the 3' end of both the sense and anti-sense strand further comprise, in 5' to 3' order: a spacer; a second phosphate or modified internucleoside linker; and a 3' end cap. The two strands can have the same or different spacers, phosphates or modified internucleoside linkers, and/or 3' end caps. The strands can be ribonucleotides, or, optionally, one or more nucleotide can be modified or substituted. Optionally, at least one nucleotide comprises a modified internucleoside linker. Optionally, the RNAi agent can be modified on one or both