A synthetic antisense oligonucleotide against Bcl-2 messenger RNA with potential antitumor activity. Oligonucleotide SPC2996 binds to and inactivates Bcl-2 mRNA, thereby inhibiting the expression of Bcl-2 protein, promoting tumor cell apoptosis, and potentially enhancing the efficacy of standard cytotoxic chemotherapy. Linked to tumor drug resistance, the antiapoptotic protein Bcl-2 is upregulated in several types of cancers.