Chimeric double-stranded nucleic acid

A pharmaceutical composition for reducing the level of a transcription product in a cell comprising:

• a double-stranded nucleic acid complex comprising a first nucleic acid strand, a second nucleic acid strand which has a sequence complementary to the first nucleic acid strand, and a hairpin linker which links the first nucleic acid strand and the second nucleic acid strand, wherein:
• (i) the first nucleic acid strand hybridizes to the transcription product, and is (a) a nucleic acid strand which comprises at least 4 consecutive DNA nucleotides or modified DNA nucleotides that are recognized by RNase H when the strand is hybridized to the transcription product, wherein the total number of nucleotides of the first nucleic acid strand is 12 to 25;
• and
• (ii) the second nucleic acid strand is a nucleic acid strand which comprises (a) at least 4 consecutive RNA nucleotides, and (b) one or more modified nucleotides, nucleotide analogs and/or modified nucleotide analogs located 5′ to the at least 4 consecutive RNA nucleotides, and/or (c) one or more modified nucleotides, nucleotide analogs and/or modified nucleotide analogs located 3′ to the at least 4 consecutive RNA nucleotides, wherein the total number of nucleotides of the second nucleic acid strand is 12 to 31.