Abstract: A method for inhibiting expression of an mRNA having an expanded trinucleotide repeat region is provided comprising administering an oligomer comprising a sense strand and an antisense strand wherein: a) the antisense strand comprises a sequence of Formula (I): rGrCrUrGrCrUrGrCX1X2rCrUrGrCrUrGrCrUrG (I), wherein X1 and X2 are each independently selected from rA, rU, rG, rC, UNA-A, UNA-U, UNA-G, and UNA-C and wherein at least one of X1 and X2 is a UNA monomer; b) the oligomer comprises a UNA monomer at the first position at the 5?-end of the sense strand; and the sense strand and the antisense strand each independently include 19-29 monomers. The oligomer can be formulated in a lipid delivery vehicle, and can inhibit expression of Atrophin-1, Huntingtin, Ataxin-1, Ataxin-2, Ataxin-3, Ataxin-7, Alpha1A-voltage-dependent calcium channel subunit, TATA-box binding protein (TBP), Androgen Receptor, PP2A-PR55beta, FMR-1 Protein (FMRP), FMR-2 protein, Frataxin, Dystrophy Protein Kinase (DMPK), or Ataxin-8.