A method of treating a disease resulting from the expression of a harmful gene is described. The method includes the step of administering a therapeutically effective amount of a pharmaceutical composition having at least one double stranded oligonucleotide including two complementary oligonucleotide sequences forming a hybrid. Each oligonucleotide sequence comprises at one of their 3' or 5' ends one to five unpaired nucleotides forming single-strand ends extending beyond the hybrid. One of the oligonucleotide sequences is substantially complementary to a target sequence belonging to a DNA or messenger RNA molecule of a gene coding a mutated or nonmutated androgen receptor.