The present invention relates to anti-gene oligonucleotides adapted to hybridize to DNA in a HTT gene, which are based on locked nucleic acids, phosphorodiamidate morpholino oligomers, (PMO) or equivalent oligonucleotide analogues comprising a (CAG)n sequence, and whose target is a sequence where the majority of the repeats are CAG/CTG, for use in down regulating the expression of the HTT gene, resulting in reduced HTT mRNA and protein levels in afflicted subjects, or in diagnosis, treatment and/or prevention of Huntington's disease, and where the anti-gene oligonucleotides target non-canonical DNA structures, including hairpin and cruciform. The invention also relates to a delivery system comprising said oligonucleotides and said use thereof.