AB928 is a potent and selective dual antagonist of the adenosine receptors known as A2aR and A2bR. Adenosine is a powerful immunosuppressive substance produced inside tumors as a result of rapid cancer cell turnover and, in some cases, in connection with certain anti-tumor interventions, such as chemotherapy and radiation. The A2aR and A2bR receptors are expressed on the surface of immune cells (such as T cells, NK cells, dendritic cells and macrophages) and mediate the immunosuppressive effects of adenosine. AB928, a small-molecule drug that will be administered to patients orally, is the only drug currently in development that is able to block both of these adenosine receptors. We anticipate initiating clinical trials with AB928 in the third quarter of 2017.
AB154 is a monoclonal antibody (mAb) that potently and selectively blocks a novel immune checkpoint called TIGIT. Like some of the first-generation immune checkpoints (e.g., PD-1 and CTLA-4), TIGIT is expressed on exhausted T cells, which may reside inside tumors but are unable to mount an effective attack against the cancer cells. It is also expressed on a wide range of other tumor-infiltrating immune cells, such as NK cells and regulatory T cells. By producing proteins that bind to TIGIT, cancer and other cells can interfere with the ability of tumor-infiltrating immune cells to mount an effective anti-tumor response. AB154 will block this interaction, which we expect will result in a powerful anti-tumor effect. We anticipate initiating clinical trials with AB154 in the first half of 2018.