with linear oligonucleotides at the same dose. At the conclusion of the initial phase of the experiment, seven out of eight mice in the group treated with the combination of AST-008 and the anti-PD-1 antibody had no palpable tumors. In contrast, no mice treated with linear oligonucleotides and the anti-PD-1 antibody survived.
In the next phase of this study, we re-challenged the seven surviving mice from the combination group that was treated with AST-008 and anti-PD-1 with the same breast cancer tumor type. A new group of six mice that had never received any therapy, referred to here as naïve mice, was also inoculated with the same breast cancer tumor type for comparison. The tumor growth and survival were monitored in both groups of mice without further treatment with the AST-008 and anti-PD-1 antibody combination. No palpable tumors were observed in the surviving mice from the combination group through day 105 of the study, whereas naïve mice showed tumor growth. Finally, on day 105 of the study, the mice from the combination group that had survived two rounds of tumor implantation were injected with different tumor types. The mouse colon cancer tumors grew in the animals that had survived two challenges with breast cancer cells. Taken together, we believe these data demonstrate an adaptive immune response and a systemic anti-cancer vaccination against the treated tumor type. We believe these data also demonstrate that AST-008 has the potential to synergize with checkpoint inhibitors for immuno-oncology applications.
Importantly, AST-008 in combination with selected anti-PD-1 antibodies shows significantly greater activity compared to the linear oligonucleotides of the same sequence and concentration. We believe this demonstrates the potential advantage of our proprietary SNA design compared to linear oligonucleotides for effecting a tumor clearing response.
AST-008 in combination with a certain anti-PD-1 antibody in breast cancer mouse model resistant to anti-PD-1 treatment. Surviving mice from the experiment treated with anti-PD-1 and AST-008 survived when re-injected with the same EMT6 breast cancer cells, but did not survive when injected with unrelated CT-26 or 4T1 cancer cells. * p < 0.0001 versus vehicle treated group.
Melanoma mouse model. We have demonstrated the synergy of AST-008 with a selected anti-PD-1 antibody in a mouse melanoma model where the antibody is not effective on its own. This is representative of most advanced melanoma patients who receive anti-PD-1 antibodies because the majority of patients do not respond to the therapy. This study was executed with 10 mice per group, and there were four treatment groups. The animals were treated with vehicle, an anti-PD-1 antibody alone, AST-008 alone, or a combination of the antibody and AST-008. AST-008 was administered subcutaneously on days 3, 6, 9, 12, and 15 after tumor implantation at a dose of 0.8 mg/kg/injection. The anti-PD-1 antibody was injected intraperitoneally on days 5, 10 and 15 at a dose of 10 mg/kg/