Abstract B100: AO-176, a highly differentiated humanized anti-CD47 antibody, exhibits single-agent and combination antitumor efficacy with chemotherapy and targeted antibodies

Purpose of study: To determine whether AO-176, a highly differentiated, humanized antibody targeting CD47, shows efficacy alone or in combination with a variety of approved anti-cancer drugs in solid tumors. Methods: We investigated AO-176 as a single agent and in combination with chemotherapies and targeted antibodies, utilizing standard in vitro phagocytosis assays, tumor cell killing assays, and in vivo xenograft models. Results: AO-176 is a highly-differentiated anti-CD47 antibody that not only blocks the CD47/SIRPα interaction to stimulate phagocytosis of tumor cells, but also exerts direct killing activity on tumor cells (non-ADCC), induces immunogenic cell death, and exhibits preferential binding to tumor cells compared to normal cells. In addition, tumor-specific CD47 binding by AO-176 increases in the acidic tumor microenvironment. As a single agent, AO-176 induced cell killing (14-52% Annexin V positivity, EC50 = 1-30 μg/ml) and phagocytosis (10-34%, EC50 = 0.8-3.3 μg/ml) in ovarian, gastric, non-small cell lung, head and neck, colorectal, thyroid, pancreatic and endometrial solid tumor cell lines. When combined with tumor-targeted antibodies (i.e. cetuximab against head and neck and colorectal cancer cell lines, or the checkpoint inhibitor avelumab against ovarian cancer cell lines), AO-176 significantly enhanced phagocytosis of the tumor cells in vitro. In combination with the chemotherapeutics paclitaxel and cisplatin, AO-176 also potentiated direct tumor killing of gastric cancer cells in vitro. In vivo, AO-176 showed potent single-agent anti-tumor activity against ovarian and gastric tumor xenografts. These data add to the previous pre-clinical anti-tumor activity of AO-176 reported in breast cancer, multiple myeloma, and non-Hodgkin’s lymphoma xenografts. When cisplatin or paclitaxel was added to the AO-176 treatment regimen against xenografted ovarian tumors in vivo, significant combination anti-tumor activity was observed. We then sought to extend our promising in-vitro findings from combining AO-176 with a checkpoint inhibitor to in-vivo models. As AO-176 is human CD47-specific, we utilized an in-house murine reactive anti-CD47 blocking antibody and combined it with a murine-reactive anti-PDL1 antibody to treat MC38 murine tumors established in syngeneic mice. Combination of the two antibodies significantly improved anti-tumor efficacy compared to either single agent. Conclusions: AO-176 has demonstrated broad in vitro phagocytosis/killing as well as in vivo efficacy that supports its development, both as a single agent and in combination with other anti-cancer drugs. With a highly differentiated mechanism of action and binding profile, AO-176 may have the potential to improve upon the safety and efficacy profiles relative to other agents in this class. AO-176 is currently being evaluated in a Phase 1 clinical trial (NCT03834948) for the treatment of patients with select solid tumors. Citation Format: Casey Wilson, Myriam Bouchlaka, Robyn Puro, Ben Capoccia, Ronald Hiebsch, Prabir Chakraborty, Michael Donio, Vicki Sung, Daniel Pereira. AO-176, a highly differentiated humanized anti-CD47 antibody, exhibits single-agent and combination antitumor efficacy with chemotherapy and targeted antibodies [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B100. doi:10.1158/1535-7163.TARG-19-B100