The invention relates to a double-stranded short interfering nucleic acid (siNA) molecule specific to the Bcl-XL transcript, comprising a sense and an antisense region, wherein the sense region comprises the nucleotide sequence SEQ ID NO: 1 or a sequence having at least 70% identity, preferably at least 80% identity, more preferably at least 90% identity with said sequence, and the antisense region comprises a nucleotide sequence that is complementary to the sense region, and its use for treating cancer.