Patent ID: 7763590

Claim:
A method for inhibiting the expression of a mutant target gene in a mammalian cell in vitro, comprising the steps of: a) introducing into said cell in vitro an oligoribonucleotide having a double stranded structure (dsRNA) consisting of two separate non-linked RNA strands, wherein a first strand of the dsRNA has a complementary region that is substantially complementary to less than 26 contiguous nucleotides of an RNA transcript of at least part of said target mutant gene and a second strand of the dsRNA is complementary to the first strand, and b) maintaining the cell produced in step (a) for a time sufficient to obtain degradation of an RNA transcript of said mutant target gene, thereby inhibiting the expression of said target mutant gene in said cell without inhibiting expression of a wild-type form of the target gene, wherein said first and second strand of said dsRNA are 19 to less than 30 nucleotides in length, and wherein the complementary region of said first strand of said dsRNA contains one mismatch relative to said mutant target gene and at least two mismatches relative to the wild type form of the target gene.