SPC2996 - A New Bcl-2 Inhibitor for the Treatment of CLL.

Abstract The proapoptotic oligonucleotide agent - SPC2996, has been developed by Santaris Pharma A/S, as a specific Bcl-2 mRNA antagonist. SPC2996 was selected from our inhouse discovery research in a library of short antisense oligonucleotides with Locked Nucleic Acid (LNA). LNA brings a significant increase in the affinity towards complementary RNA and in addition remarkably increases the bio-stability. Stability was evaluated in human and rodent plasma with SPC2996 capable of 20day half life in human serum. mRNA and protein analyses were used for showing specific downregulation of Bcl-2 in cancer cell lines and this reduction was associated with induction of apoptosis. Cellular Bcl-2 responses on mRNA and protein are seen from 1nM of SPC2996. These effects lead to apoptosis induction. Anti- tumor activity was studied in xenotransplanted athymic mice models of human cancer. SPC2996 was equally effective as Genasense in these models. That SPC2996 specifically dowregulates Bcl-2 was demonstrated in primate studies. Side by side comparison with Oblimersen sodium in these studies showed SPC2996 effectively downregulated Bcl-2 at 3mg/kg while Oblimersen sodium showed little or no target downregulation. Microarray analyses were used to demonstrate specificity of target downregulation. With SPC2996 we bring the first member of a new generation of safe, potent and specific mRNA antagonist drugs, exploiting the benefits of LNA. SPC2996 provides the cancer patient with the possibility of lower and less frequent dosing, which is unprecedented by any other oligonucleotide inhibitor of Bcl-2 used in clinical trials.