The disclosure relates to compositions comprising a RNAi agent having a novel format. These RNAi agents comprise 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 first two base-pairing nucleotides on the 3 end of the sense and/or anti-sense strand are 2-MOE. Optionally, the RNAi agent can be modified on one or both 5 end. Optionally, the sense strand can comprise a 5 end cap which reduces the amount of the RNA interference mediated by this strand. Optionally, the RNAi agent is attached to a ligand. This format can be used to devise RNAi agents to a variety of different targets and sequences. The disclosure also relates to processes for making such compositions, and methods and uses of such compositions, e.g., to mediate RNA interference.La présente invention concerne des compositions comprenant un agent de type ARNi présentant un format inédit. Ces agents de type ARNi comprennent un brin sens et un brin antisens, chaque brin étant un 18-mère et lesdits brins formant conjointement un duplex à extrémités franches, lextrémité 3 dau moins un brin se terminant dans une séquence de liaison phosphate ou internucléosidique modifiée, et comprenant, en outre, en allant de lextrémité 5 ver
